METHOD FOR DEWAXING HYDROCARBON OIL AND METHOD FOR PRODUCING LUBRICATING-OIL BASE OIL

Information

  • Patent Application
  • 20150114882
  • Publication Number
    20150114882
  • Date Filed
    March 29, 2013
    11 years ago
  • Date Published
    April 30, 2015
    9 years ago
Abstract
There is provided a method for dewaxing a hydrocarbon oil for improving the life of a hydroisomerization catalyst. An aspect of a method for dewaxing a hydrocarbon oil according to the present invention comprises: a first step of subjecting a hydrocarbon oil in which a peroxide value is 100 ppm by mass or more to hydrotreating to obtain a material to be treated in which a peroxide value is 30 ppm by mass or less; and a second step of subjecting the material to be treated in which a peroxide value is 30 ppm by mass or less to hydroisomerization treatment using a hydroisomerization catalyst.
Description
TECHNICAL FIELD

The present invention relates to a method for dewaxing a hydrocarbon oil and a method for producing a lubricant base oil.


BACKGROUND ART

Among petroleum products, for example, lubricant oils, gas oils, and jet fuels or the like are products in which cold flow property is regarded as important. When base oils used for these products contain waxy components such as normal paraffins or slightly branched isoparaffins, the cold flow property of the base oils decreases. Therefore, it is desirable to completely or partially remove the waxy components in the production of the base oils. Alternatively, it is desirable that the waxy components are completely or partially converted to components other than the waxy components. Hydrocarbons (hereinafter, referred to as “FT synthetic oils”) obtained by a Fischer-Tropsch reaction (hereinafter, referred to as a “FT reaction”) have recently attracted attention as feedstocks for producing lubricant oils or fuels, because they do not contain environmental load substances such as sulfur compounds. However, because the FT synthetic oils also contain many waxy components, the waxy components in the FT synthetic oils are desirably reduced.


As a dewaxing technique for removing waxy components from hydrocarbon oils, a method for extracting waxy components using a solvent such as liquefied propane or MEK (Methyl Ethyl Ketone) is known. However, this method has problems in that the operating costs of an extracting apparatus are high; the types of applicable feedstocks are limited; and the product yield is limited by the type of feedstock.


On the other hand, as a dewaxing technique for converting waxy components in a hydrocarbon oil to non-waxy components, for example, catalytic dewaxing is known, in which the hydrocarbon oil is contacted, in the presence of hydrogen, with a so-called bifunctional catalyst having hydrogenation-dehydrogenation function and isomerization function, thereby isomerizing normal paraffins in the hydrocarbon oil to isoparaffins. As bifunctional catalysts used for catalytic dewaxing, solid acids are known. Among the solid acids, catalysts containing molecular sieves made of zeolites, and metals belonging to Groups 8 to 10 or Group 6 of the periodic table are known, and in particular, catalysts in which the metals are supported on molecular sieves are known.


Catalytic dewaxing is an effective method for improving the cold flow property of hydrocarbon oils. It is necessary to sufficiently increase the conversion rate of the normal paraffins in the hydrocarbon oils in order to obtain a fraction that is suitable as a lubricant base oil or a fuel base oil according to the catalytic dewaxing of the hydrocarbon oils. However, the above-mentioned catalysts used in catalytic dewaxing have both isomerization function and hydrocarbon-cracking function. Therefore, in the catalytic dewaxing of the hydrocarbon oils, conversion of the hydrocarbon oil to lighter products also proceeds as the conversion rate of the normal paraffins increases, to make it difficult to obtain a desired fraction in high yield. Particularly when producing a high-quality lubricant base oil in which a high viscosity index and a low pour point are required, it is very difficult to economically obtain an intended fraction by the catalytic dewaxing of the hydrocarbon oil. For this reason, synthetic base oils such as poly-α-olefins have been frequently used in this field.


In recent years, however, in the fields of lubricant base oils and fuel base oils or the like, the production of Group II, Group III, and Group III+ base oils using hydrotreating has become increasingly popular. Under such circumstances, there is a need for a hydroisomerization catalyst having both suppressed cracking activity for hydrocarbons and high isomerization reaction activity, i.e., having excellent isomerization selectivity, for the purpose of obtaining a desired isoparaffin fraction in high yield from a hydrocarbon oil containing waxy components.


Attempts to improve the isomerization selectivity of catalysts used in catalytic dewaxing have been made in the past. For example, the following Patent Literature 1 discloses a hydroisomerization catalyst including a molecular sieve (ZSM-22, ZSM-23, and ZSM-48 or the like) containing a metal of Group VIII or the like of the periodic table, having one-dimensional pores of an intermediate size, and having a crystallite size of not more than about 0.5 μm. The following Patent Literature 1 discloses a process for producing a dewaxed lubricant oil, wherein a straight-chain or slightly branched hydrocarbon raw material having 10 or more carbon atoms is contacted under isomerization conditions with the above-mentioned hydroisomerization catalyst.


Zeolite that constitutes a hydroisomerization catalyst is typically produced by hydrothermal synthesis in the presence of an organic template in order to construct a predetermined porous structure. Herein, the organic template is an organic compound having an amino group and ammonium group or the like. The synthesized zeolite is calcined in an atmosphere containing molecular oxygen at a temperature of, for example, about 550° C. or more, thereby removing the organic template contained in the zeolite (see the final paragraph of “2.1. Materials” on page 453 of the following Non-Patent Literature 1). The calcined zeolite is ion-exchanged into an ammonium form in an aqueous solution containing ammonium ions, for example (see “2.3. Catalytic experiments” on page 453 of the following Non-Patent Literature 1). Metal components of Group 8 to 10 or the like of the periodic table are further supported on the ion-exchanged zeolite. The zeolite on which the metal component is supported is subjected to steps such as drying and optionally extruding, and then loaded in a reactor; the zeolite is calcined in an atmosphere containing molecular oxygen at a temperature of about 400° C. The calcined zeolite is further subjected to reduction treatment with, for example, hydrogen, at about the same temperature, and thereby the zeolite is provided with catalytic activity as a bifunctional catalyst.


Recently, there has been proposed a method for ion-exchanging zeolite subjected to hydrothermal synthesis in a state where the zeolite contains an organic template without calcining the zeolite at the above-mentioned high temperature, to produce a hydroisomerization catalyst from the ion-exchanged zeolite, for the purpose of further improving isomerization selectivity of the hydroisomerization catalyst (see the following Patent Literature 2).


CITATION LIST
Patent Literature



  • Patent Literature 1: U.S. Pat. No. 5,282,958

  • Patent Literature 2: Japanese Patent Application Laid-Open No. 2010-155187



Non Patent Literature

Non-Patent Literature 1: J. A. Martens et al., J. Catal. 239 (2006) 451


SUMMARY OF INVENTION
Technical Problem

In the above-mentioned hydroisomerization catalyst, the reduced metal functions as an active site. Therefore, when a hydrocarbon oil containing strong oxidizer is contacted with the hydroisomerization catalyst, the metal that is the active site is oxidized to lose catalytic activity, which is apt to extremely shorten the life of the hydroisomerization catalyst. The short life of the catalyst poses an economical problem because it causes the catalyst costs to increase.


The present invention has been made in view of the above-mentioned problems of the conventional technique, and an object of the present invention is to provide a method for dewaxing a hydrocarbon oil and a method for producing a lubricant base oil for improving the life of a hydroisomerization catalyst.


Solution to Problem

An aspect of a method for dewaxing a hydrocarbon oil of the present invention comprises: a first step of subjecting a hydrocarbon oil in which a peroxide value is 100 ppm by mass or more to hydrotreating to obtain a material to be treated in which a peroxide value is 30 ppm by mass or less; and a second step of subjecting the material to be treated in which a peroxide value is 30 ppm by mass or less to hydroisomerization treatment using a hydroisomerization catalyst.


In an aspect of the present invention, the hydrocarbon oil is preferably synthesized by a Fischer-Tropsch reaction.


In an aspect of the present invention, it is preferable that the hydroisomerization catalyst contains zeolite; and the zeolite contains an organic template, and has a one-dimensional porous structure including a 10-membered ring.


In an aspect of the present invention, the zeolite is preferably at least one selected from the group consisting of zeolite ZSM-22, zeolite ZSM-23, zeolite SSZ-32, and zeolite ZSM-48.


In an aspect of the present invention, it is preferable that the material to be treated contains normal paraffins those carbon numbers are 10 or more; and the material to be treated is contacted with the hydroisomerization catalyst in the presence of hydrogen in the second step.


An aspect of a method for producing a lubricant base oil of the present invention uses the above-mentioned method for dewaxing a hydrocarbon oil.


In an aspect of the method for producing a lubricant base oil of the present invention, it is preferable that the method further comprises the step of subjecting the material to be treated after the hydroisomerization treatment to hydrofinishing.


In an aspect of the method for producing a lubricant base oil of the present invention, it is preferable that the method further comprises the step of subjecting the material to be treated after the hydrofinishing to vacuum distillation.


Advantageous Effects of Invention

The present invention provides a method for dewaxing a hydrocarbon oil and a method for producing a lubricant base oil for improving the life of a hydroisomerization catalyst.







DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments in any way.


[Method for Dewaxing Hydrocarbon Oil]


A method for dewaxing a hydrocarbon oil according to this embodiment comprises a first step and a second step. The first step subjects a hydrocarbon oil in which a peroxide value is 100 ppm by mass or more to hydrotreating to obtain a material to be treated in which a peroxide value is 30 ppm by mass or less. The second step (dewaxing step) subjects the material to be treated in which a peroxide value is reduced to 30 ppm by mass or less in the first step to hydroisomerization treatment using a hydroisomerization catalyst.


(Hydrocarbon Oil)


A hydrocarbon oil derived from petroleum may be used as a hydrocarbon oil that is a raw material, and an FT synthetic oil synthesized by a Fischer-Tropsch reaction may be used. In this embodiment, the hydrocarbon oil is preferably the FT synthetic oil (particularly, an FT wax). The sulfur content and aromatic hydrocarbon in the FT synthetic oil are lower than that of the hydrocarbon oil derived from the petroleum. Therefore, a lubricant base oil and a fuel base oil or the like in which a load on the environment is reduced can be produced by using the FT synthetic oil as a raw material. Because the sulfur content is a catalyst poison of a catalyst for hydrotreating or hydroisomerization catalyst, the poisoning of the catalyst is suppressed by using an FT synthetic oil in which the sulfur content is low, to easily improve the life of the catalyst. Hereinafter, a case where the hydrocarbon oil is the FT synthetic oil will be described.


The FT synthetic oil is produced, for example, by the following method. First, natural gas as a raw material is desulfurized. Specifically, a sulfur compound in the natural gas is converted to hydrogen sulfide by a hydrodesulfurization catalyst, or is removed by using a material adsorbing the hydrogen sulfide.


High-temperature synthesis gas primarily containing carbon monoxide gas and hydrogen gas is generated according to the reforming reaction (reforming) of the desulfurized natural gas. The reforming reaction of the natural gas is represented by the following chemical reaction equations (1) and (2). A reforming method is not limited to a water vapor-carbon dioxide reforming method using carbon dioxide and water vapor. For example, a water vapor reforming method, a partial oxidation reforming method (PDX) using oxygen, an autothermal reforming method (ATR) that is a combination of the partial oxidation reforming method and the water vapor reforming method, and a carbon dioxide reforming method or the like can also be utilized.





CH4+H2O→CO+3H2  (1)





CH4+CO2→2CO+2H2  (2)


The hydrogen gas and the carbon monoxide gas in the synthesis gas are reacted with each other. That is, the FT synthetic oil is generated by making an FT reaction exemplified by the following chemical reaction equation (3) proceed.





(2n+1)H2+nCO→CnH2n+2+nH2O  (3)


A catalyst in which an active metal is supported on an inorganic support is used as a catalyst for the FT reaction (FT catalyst). Examples of the inorganic support include porous oxides such as silica, alumina, titania, magnesia, and zirconia. Examples of the active metal include cobalt, ruthenium, iron, and nickel. A compound containing metal elements such as zirconium, titanium, hafnium, sodium, lithium, and magnesium in addition to the above-mentioned active metal may be supported on the FT catalyst. These components improve catalytic activity or contribute to control of the number of carbon atoms of the FT synthetic oil and distribution thereof.


The FT synthetic oil is a mixture of straight-chain hydrocarbons (normal paraffins) in which the number of carbon atoms is about 1 to 100, and hardly contains aromatic hydrocarbons, naphthenic hydrocarbons, and isoparaffins. An FT wax in which the number of carbon atoms is about 21 or more, and a boiling point is more than about 360° C. is contained in the FT synthetic oil.


(Summary of First Step and Second Step)


In this embodiment, the FT wax in the FT synthetic oil is dewaxed. A method for producing the lubricant base oil, the fuel base oil, or the like utilizing the FT reaction is roughly divided into a so-called GTL (Gas To Liquids) step as described above and a dewaxing-distilling step of the FT synthetic oil (FT wax). Conventionally, a plant (GTL plant) for carrying out the GTL step and a plant (dewaxing plant) for carrying out the dewaxing-distilling step of the FT wax are not necessarily adjacent to each other. For example, the GTL plant is often located in a foreign country where an extracting gas well exists, and the dewaxing plant is often located in the country (Japan). Thus, when the GTL plant and the dewaxing plant are far apart from each other, it is necessary to transport the FT wax produced in the GTL plant to the dewaxing plant. Because the transportation requires a long time of about several months, the FT wax is oxidized by oxygen in the atmosphere during the transportation. If the synthesized FT wax is stored for a long period of time even when the GTL plant and the dewaxing plant are not far apart from each other, the FT wax is oxidized.


The present inventors discovered that the FT wax oxidized during the transportation oxidizes a metal that is the active site of the hydroisomerization catalyst used for the dewaxing step after the transportation, and thereby the activity of the hydroisomerization catalyst is reduced. That is, the present inventors found that the oxidizer of the FT wax after the transportation is one of factors that shorten the life of the hydroisomerization catalyst. An object of the first step in this embodiment is to improve the life of the hydroisomerization catalyst used for the dewaxing step (second step) as described below.


In the first step of this embodiment, the FT wax oxidized during the transportation is subjected to hydrotreating to weaken the oxidizer of the FT wax. Herein, although the hydrotreating in the first step means reduction due to hydrogenation, at least any of the hydrocracking, hydroisomerization, or hydrorefining (desulfurization and denitrification or the like) of the FT wax may proceed by the hydrotreating. In the second step (dewaxing step), the FT wax is subjected to hydroisomerization treatment before the FT wax is oxidized again. That is, after the FT wax is transported to the dewaxing plant from the GTL plant in this embodiment, the FT wax oxidized during the transportation is subjected to hydrotreating in the dewaxing plant. Before the FT wax reduced by the hydrotreating is oxidized again, the dewaxing of the FT wax is carried out. As a result, the hydroisomerization catalyst for dewaxing is hardly oxidized by the FT wax, to improve the life of the catalyst. That is, because the FT wax is subjected to the hydrotreating just before the dewaxing step (after the transportation or after storage) in this embodiment, the life of the hydroisomerization catalyst can be improved irrespective of the length of a transportation time or a storage time.


Other examples of the method for reducing the oxidation nature of the FT wax include hydrotreating to the FT wax before transportation or storage, or addition of an antioxidant to the FT wax. However, it is difficult to sufficiently suppress the oxidization of the FT wax that is associated with the transportation or the storage according to only these methods. On the other hand, because the FT wax is reduced by the hydrotreating just before the dewaxing step in this embodiment, the life of the hydroisomerization catalyst can be certainly improved without using other methods.


The above-mentioned first step and second step are quantitatively expressed as follows. That is, in the first step, the hydrocarbon oil in which the peroxide value is 100 ppm by mass or more is subjected to the hydrotreating to reduce the peroxide value to 30 ppm by mass or less. In the second step (dewaxing step), the material to be treated in which the peroxide value is maintained at 30 ppm by mass or less is subjected to the hydroisomerization treatment.


Herein, the peroxide value is a ratio (unit:ppm by mass or mg/kg) of the mass of hydroperoxide (peroxide) contained in the hydrocarbon oil (FT wax) to the total mass of the hydrocarbon oil. When the hydrocarbon oil takes in oxygen in the air, the hydrocarbon oil is oxidized, to generate the hydroperoxide, which increases the peroxide value. The larger the peroxide value of the hydrocarbon oil is, the higher the oxidation nature of the hydrocarbon oil is. Therefore, the hydrocarbon oil (FT wax) in which the peroxide value is 100 ppm by mass or more means a hydrocarbon oil (FT wax) having oxidation nature that is high enough to degrade the hydroisomerization catalyst.


Although a method for measuring the peroxide value in this embodiment is based on the Japan Petroleum Institute method JPI-5S-46-96 “Testing Method for Peroxide Number of Kerosine”, the method is a method in which kerosene is replaced by a hydrocarbon oil in the test method. In this embodiment, the peroxide value is measured by making hydroperoxide in a hydrocarbon oil react with potassium iodide, and titrating free iodine with a sodium thiosulfate solution. The specific procedure of the measurement is as follows. First, a sample (hydrocarbon oil) is precisely measured off. A liquid mixture of chloroform and glacial acetic acid (volume ratio 2:3) was added into the sample put into a stoppered Erlenmeyer flask, to dissolve the sample. When the sample is not uniformly dissolved, the liquid mixture of chloroform and glacial acetic acid is further suitably added. Subsequently, while air in the flask is replaced by nitrogen gas or carbon dioxide, a saturated potassium iodide solution is added into the liquid mixture in which the sample is dissolved, and a stopper is immediately closed. After the liquid mixture in the flask is mixed for several minutes, a starch test solution as an indicator was added into the liquid mixture, and iodine in the liquid mixture was titrated with a sodium thiosulfate solution.


If the second step (dewaxing step) is carried out for the FT wax in which the peroxide value is 100 ppm by mass or more without the first step, the noble metal that is the active site of the hydroisomerization catalyst is oxidized by the FT wax, to shorten the life of the catalyst. However, in this embodiment, the FT wax is reduced by the hydrotreating in the first step. As a result, a material to be treated in which a peroxide value is reduced to 30 ppm by mass or less and oxidation nature is low is obtained. Therefore, in the second step, the oxidization of the hydroisomerization catalyst by the material to be treated hardly occurs to improve the life of the catalyst. The refining (desulfurization or the like) of the hydrocarbon oil also proceeds by the hydrotreating in the first step to obtain the material to be treated in which the content of the catalyst poison (sulfur or the like) is reduced. Therefore, in the second step, the poisoning of the hydroisomerization catalyst by the catalyst poison in the material to be treated also hardly occurs to improve the life of the catalyst.


If the hydroisomerization is carried out after the material to be treated obtained in the first step is oxidized again and the peroxide value is more than 30 ppm by mass, the hydroisomerization catalyst is oxidized by the material to be treated, which makes it difficult to improve the life of the catalyst. However, in this embodiment, the hydroisomerization is carried out before the peroxide value of the material to be treated is more than 30 ppm by mass by the oxidization after the first step, which makes it possible to improve the life of the hydroisomerization catalyst.


The upper limit value of the peroxide value of the hydrocarbon oil (FT wax) just before the first step is about 2000 ppm by mass, for example. If the first step is carried out for the hydrocarbon oil in which the peroxide value is 2000 ppm by mass or less, the peroxide value of the material to be treated obtained in the first step is easily reduced to 30 ppm by mass or less, and an effect of improving the life of the hydroisomerization catalyst used in the second step is easily obtained. If the first step is carried out for the hydrocarbon oil in which the peroxide value is 2000 ppm by mass or less, the oxidization and degradation of the catalyst for hydrotreating used in the first step are suppressed, and the life of the catalyst for hydrotreating is also improved. In this embodiment, the range of the peroxide value of the hydrocarbon oil (FT wax) just before the first step may be 100 to 2000 ppm by mass, 100 to 500 ppm by mass, or about 130 to 450 ppm by mass.


The peroxide value of the material to be treated obtained in the first step is 0 to 30 ppm by mass, and preferably 0 to 1 ppm by mass. That is, in the first step, the peroxide value of the hydrocarbon oil (FT wax) is reduced to 0 to 30 ppm by mass, and preferably 0 to 1 ppm by mass. In other words, until the hydroisomerization treatment is started, the peroxide value of the material to be treated is maintained at 0 to 30 ppm by mass, and preferably at 0 to 1 ppm by mass. When the peroxide value of the material to be treated is lower, the oxidization and degradation of a catalyst for hydroisomerization treatment are suppressed, and the life of the catalyst for hydroisomerization treatment is easily improved. In order to suppress the reoxidization of the material to be treated and to maintain the peroxide value at 30 ppm by mass or less, the material to be treated may be held in an inactive atmosphere or an nonoxidative atmosphere (for example, a storage tank or a transfer pipe shut off from the atmosphere), for example, until the second step is performed. If a time after the first step before the second step is shortened as much as possible, the reoxidization of the material to be treated can be suppressed.


(Specific Aspect of First Step)


In the hydrotreating in the first step, the hydrocarbon oil (FT wax) may be contacted with the catalyst for hydrotreating. A method for producing the catalyst for hydrotreating comprises a supporting step and a calcining step. The supporting step supports an active metal component containing an active metal element on a support to obtain a catalyst precursor. The calcining step calcines the precursor obtained in the supporting step to obtain the catalyst for hydrotreating. A support in which the content of a carbonaceous material containing a carbon atom is 0.5% by mass or less in terms of the carbon atom may be used as the support. At least one selected from metals belonging to Groups 6, 8, 9, and 10 of the periodic table may be used as the active metal element. The periodic table means a long period type element periodic table established by the International Union of Pure and Applied Chemistry (IUPAC).


The catalyst for hydrotreating may be a hydrocracking catalyst. The catalyst for hydrotreating may be a hydrorefining catalyst.


When the catalyst for hydrotreating is the hydrocracking catalyst, the support is preferably a support containing crystalline zeolites such as ultrastable Y (USY)-type zeolite, Y-type zeolite, mordenite, and β zeolite, and one or more solid acids selected from amorphous composite metal oxides such as silica-alumina, silica-zirconia, alumina-boria, alumina-zirconia, silica-titania, and silica-magnesia.


When the catalyst for hydrotreating is the hydrocracking catalyst, the support is preferably a support containing USY-type zeolite, and one or more selected from silica-alumina, alumina-boria, and silica-zirconia. The support is more preferably a support containing USY-type zeolite, and one or more selected from alumina-boria and silica-alumina.


The USY-type zeolite is obtained by ultrastabilizing the Y-type zeolite according to hydrothermal treatment and/or acid treatment. The USY-type zeolite includes a fine porous structure intrinsically included in the Y-type zeolite. This fine porous structure is a structure including micropores having a pore diameter of 2 nm or less. In addition to the above-mentioned fine porous structure, new pores in which a pore diameter is 2 to 10 nm are further formed in the USY-type zeolite. Although the mean particle size of the USY-type zeolite is not particularly limited, the mean particle size is preferably 1.0 μm or less, and more preferably 0.5 μm or less. The molar ratio (the molar ratio of silica to alumina) of silica/alumina in the USY-type zeolite is preferably 10 to 200, more preferably 15 to 100, and still more preferably 20 to 60.


The support of the hydrocracking catalyst preferably contains 0.1 of 80% by mass of crystalline zeolite and 0.1 to 60% by mass of an amorphous composite metal oxide.


A binder may be mixed in the support of the hydrocracking catalyst for the purpose of improving the extrudability and mechanical strength of the support. Preferred examples of the binder include alumina, silica, and magnesia. Although the mixing amount of the binder is not particularly limited, the mixing amount is preferably 20 to 98% by mass based on the total mass of the support, and more preferably 30 to 96% by mass.


The support of the hydrocracking catalyst is preferably extruded. Although the shape of the extruded support is not particularly limited, examples of the shape include a spherical shape, a cylindrical shape, an irregular tubular shape having a three leaf-shaped or four leaf-shaped cross section, and a disc shape. A method for forming the support is not limited, and known methods such as extrusion and tablet molding are used. The extruded support is typically calcined.


The active metal element contained in the hydrocracking catalyst is preferably at least one selected from the group consisting of metals belonging to Groups 8 to 10 of the periodic table. Suitable examples of the active metal element include cobalt, nickel, rhodium, palladium, iridium, and platinum. Among these metals, at least one selected from nickel, palladium, and platinum is more preferably used, and at least one selected from palladium and platinum is still more preferably used.


When the active metal element contained in the hydrocracking catalyst is a metal other than noble metals such as cobalt and nickel, the content of the active metal element is preferably 2 to 50 parts by mass in terms of a metal oxide based on the total mass of the support. When the active metal element supported on the support in the hydrocracking catalyst is a noble metal such as platinum, palladium, rhodium, or indium, the content of the active metal element is preferably 0.1 to 3.0 parts by mass in terms of a metal atom based on the total mass of the support. When the content of the active metal element is less than the above-mentioned lower limit value, the hydrocracking tends not to sufficiently proceed. On the other hand, when the content of the active metal element is more than the above-mentioned upper limit value, the dispersion of the active metal element tends to decrease to decrease the activity of the catalyst, and the catalyst costs increase.


When the catalyst for hydrotreating of this embodiment is the hydrorefining catalyst, the support is preferably a support containing metal oxides such as alumina, silica, titania, zirconia, and boria. The support of the hydrorefining catalyst may be a support containing composite metal oxides such as silica-alumina, silica-zirconia, alumina-boria, alumina-zirconia, silica-titania, and silica-magnesia.


The support of the hydrorefining catalyst preferably contains a composite metal oxide having solid acidity such as silica-alumina, silica-zirconia, alumina-zirconia, and alumina-boria. Thereby, it is possible to allow the hydroisomerization of a linear aliphatic hydrocarbon to efficiently proceed simultaneously with the hydrorefining. The support may contain a small amount of zeolite.


A binder may be mixed in the support of the hydrorefining catalyst for the purpose of improving the extrudability and mechanical strength of the support. Preferred examples of the binder include alumina, silica, and magnesia. Although the mixing amount of the binder is not particularly limited, the mixing amount is preferably 20 to 98 parts by mass based on the total mass of the support, and more preferably 30 to 96 parts by mass.


The support of the hydrorefining catalyst is preferably extruded. Although the shape of the extruded support is not particularly limited, examples of the shape include a spherical shape, a cylindrical shape, an irregular tubular shape having a three leaf-shaped or four leaf-shaped cross section, and a disc shape. A method for forming the support is not limited, and known methods such as extrusion and tablet molding are used. The extruded support is typically calcined.


The active metal element contained in the hydrorefining catalyst is preferably at least one selected from the group consisting of metals belonging to Groups 6, 8, 9, and 10 of the periodic table. Suitable examples of the active metal element include noble metals such as platinum, palladium, rhodium, ruthenium, iridium, and osmium, or cobalt, nickel, molybdenum, tungsten, and iron. The active metal element is preferably platinum, palladium, nickel, cobalt, molybdenum, or tungsten, and more preferably platinum or palladium. A plurality of these metals may be used in combination. Preferred examples of the combination of the active metal elements include platinum-palladium, cobalt-molybdenum, nickel-molybdenum, nickel-cobalt-molybdenum, and nickel-tungsten.


When the active metal element supported on the support in the hydrorefining catalyst is the noble metal, the content of the active metal element is preferably 0.1 to 3.0 parts by mass in terms of a metal atom based on the total mass of the support. When the active metal element supported on the support in the hydrorefining catalyst is a metal other than the noble metal, the content of the active metal element is preferably 2 to 50 parts by mass in terms of a metal oxide based on the total mass of the support. When the content of the active metal element is less than the above-mentioned lower limit value, the hydrorefining and the hydroisomerization tend not to sufficiently proceed. When the content of the active metal element is more than the above-mentioned upper limit value, the dispersibility of the active metal element tends to decrease to decrease the activity of the catalyst, and the catalyst costs increase.


In a hydrotreating apparatus for carrying out the hydrotreating in the first step, a crude wax fraction and an uncracked wax fraction (a hydrocarbon of about C21 or more) that constitute the FT wax are partially converted to a hydrocarbon in which the number of carbon atoms is about C20 or less by the hydrocracking. Furthermore, the hydrocarbon is partially converted to a naphtha fraction (about C5 to C10) lighter than a middle fraction (about C11 to C20) by excessive cracking, and is further converted to a gaseous hydrocarbon of C4 or less. On the other hand, partially, the crude wax fraction and the uncracked wax fraction do not sufficiently undergo the hydrocracking, and become the uncracked wax fraction of about C21 or more. The composition of a hydrocracked product is determined by the hydrocracking catalyst to be used and hydrocracking reaction conditions. Herein, the “hydrocracked product” refers to all hydrocracked products containing the uncracked wax fraction unless otherwise specified. If the hydrocracking reaction conditions are made severe beyond necessity, the content of the uncracked wax fraction in the hydrocracked product decreases, however, a light component in which a molecular weight is equal to or less than that of the naphtha fraction increases, to decrease the yield of the middle fraction. On the other hand, if the hydrocracking reaction conditions are eased beyond necessity, the uncracked wax fraction increases, to decrease the yield of the middle fraction. When the mass of all the cracked products in which a boiling point is 25° C. or more is M1 and the mass of the cracked product in which a boiling point is 25 to 360° C. is M2, a cracking rate M2/M1 is about 10 to 90%. The cracking rate M2/M1 is preferably 20 to 80%, and more preferably 25 to 50%. The cracking rate M2/M1 is adjusted by suitably setting each reaction condition of the hydrotreating.


In the hydrotreating apparatus, in parallel to a hydrocracking reaction, the hydroisomerization reaction of the normal paraffins constituting the crude wax fraction and the uncracked wax fraction, or the hydrocracked products thereof proceeds, to generate the isoparaffins. When the hydrocracked product is used as a fuel oil base, the isoparaffins generated according to the hydroisomerization reaction are components contributing to improvement in the cold flow property, and the generation rate is preferably high. Furthermore, the removal of oxygen-containing compounds such as olefins and alcohols that are contained in the crude wax fraction and are by-products of an FT synthesis reaction also proceeds. That is, the olefins are converted to a paraffin hydrocarbon by the hydrogenation, and the oxygen-containing compounds are converted to the paraffin hydrocarbon and water by hydrogenation deoxygenation.


In the first step, the hydrotreating may be carried out under each of the following step conditions in order to reduce the peroxide value of the FT wax to a value of 30 ppm by mass or less from a value of 100 ppm by mass or more.


The reaction temperature of the hydrotreating is about 180 to 400° C., preferably 200 to 370° C., more preferably 250 to 350° C., and particularly preferably 280 to 350° C. Although the peroxide value is reduced when the reaction temperature is more than 400° C., the cracking of the FT wax to the light component proceeds, which tends to decrease the yields of the middle fraction and heavy component and to color the product, thereby limiting the use of the product as the fuel oil base. On the other hand, when the reaction temperature is less than 180° C., the peroxide value cannot be reduced. Furthermore, the hydrocracking reaction does not sufficiently proceed, to decrease the yield of the middle fraction and to suppress the generation of the isoparaffins according to the hydroisomerization reaction, and the oxygen-containing compounds such as alcohols tend to remain without being sufficiently removed.


A hydrogen partial pressure in a hydrotreating reaction is about 0.5 to 12 MPa, and preferably 1.0 to 5.0 MPa. When the hydrogen partial pressure is less than 0.5 MPa, the hydrocracking and the hydroisomerization or the like tend not to sufficiently proceed. On the other hand, when the hydrogen partial pressure is more than 12 MPa, high pressure resistance is required for the hydrotreating apparatus, and facility costs tend to increase.


The liquid hourly space velocity (LHSV) of the FT wax (the crude wax fraction and the uncracked wax fraction) in the hydrotreating reaction is about 0.1 to 10.0 h−1, and preferably 0.3 to 3.5 hr−1. When the LHSV is less than 0.1 hr−1, excessive hydrocracking tends to proceed, resulting in lowered productivity. Conversely, when the LHSV is more than 10.0 hr−1, the peroxide value cannot be reduced, and the hydrocracking and the hydroisomerization or the like tend not to sufficiently proceed.


A hydrogen/oil ratio (a hydrogen/FT wax ratio) is about 50 to 1000 Nm3/m3, and preferably 70 to 800 Nm3/m3. When the hydrogen/oil ratio is less than 50 Nm3/m3, the hydrocracking and the hydroisomerization or the like tend not to sufficiently proceed. Conversely, when the hydrogen/oil ratio is more than 1000 Nm3/m3, a large-scale hydrogen feed apparatus or the like tends to be required.


The amount of the catalyst for hydrotreating used and the time required for the hydrotreating, or the like may be suitably adjusted according to the amount of the FT wax, the peroxide value of the FT wax before the hydrotreating, and each of the above-mentioned reaction conditions, or the like.


(Specific Aspect of Second Step)


The hydroisomerization catalyst used in the second step is produced according to a specific method, and is thereby provided with its features. Hereinafter, the hydroisomerization catalyst will be described according to its preferred production aspect. This embodiment can significantly improve the life of the following hydroisomerization catalyst particularly.


A method for producing the hydroisomerization catalyst of this embodiment comprises a first step of heating a mixture containing an ion-exchanged zeolite obtained by ion-exchanging an organic template-containing zeolite containing an organic template and having a 10-membered ring one-dimensional porous structure in a solution containing ammonium ions and/or protons, and a binder at a temperature of 250 to 350° C. in a N2 atmosphere to obtain a support precursor, and a second step of calcining a catalyst precursor in which a platinum salt and/or a palladium salt are/is contained in the support precursor at a temperature of 350 to 400° C. in an atmosphere containing molecular oxygen to obtain a hydroisomerization catalyst in which platinum and/or palladium are/is supported on the support containing the zeolite.


The organic template-containing zeolite used in this embodiment has a one-dimensional porous structure including a 10-membered ring, in view of achieving a high level of both high isomerization activity and suppressed cracking activity in the hydroisomerization reactions of normal paraffins. Examples of such zeolites include AEL, EUO, FER, HEU, MEL, MFI, NES, TON, MTT, WEI, *MRE, and SSZ-32. The above-mentioned three alphabet letters mean framework type codes assigned to structures of classified molecular sieve-type zeolites by the Structure Commission of the International Zeolite Association. Zeolites having the same topology are collectively designated by the same code.


Among the above-mentioned zeolites having one-dimensional porous structures including a 10-membered ring, the organic template-containing zeolite are preferably zeolites having a TON and MIT structures, zeolite ZSM-48 that is zeolite having an *MRE structure, and zeolite SSZ-32 in view of high isomerization activity and low cracking activity. Zeolite ZSM-22 is more preferred among zeolites having the TON structure, and zeolite ZSM-23 is more preferred among zeolites having the MTT structure.


The organic template-containing zeolite is hydrothermally synthesized according to a known method using a silica source, an alumina source, and an organic template that is added to construct the predetermined porous structure described above.


The organic template is an organic compound having an amino group and an ammonium group or the like, and is selected according to the structure of the zeolite to be synthesized, however, the organic template is preferably an amine derivative. Specifically, the organic template is preferably at least one selected from the group consisting of alkylamine, alkyldiamine, alkyltriamine, alkyltetramine, pyrrolidine, piperazine, aminopiperazine, alkylpentamine, alkylhexamine, and their derivatives. The carbon number of above alkyl group may be 4 to 10, preferably 6 to 8. Typical examples of the alkyldiamines include 1,6-hexanediamine and 1,8-diaminooctane.


The molar ratio of the silicon element to the aluminum element ([Si]/[Al], hereinafter referred to as the “Si/Al ratio”) both of which constitute the organic template-containing zeolite having a 10-membered ring one-dimensional porous structure is preferably 10 to 400, and more preferably 20 to 350. When the Si/Al ratio is less than 10, although the activity for the conversion of the normal paraffins increases, the isomerization selectivity to isoparaffins tends to decrease, and cracking reactions tend to sharply increase as the reaction temperature increases, which is undesirable. Conversely, if the Si/Al ratio is more than 400, catalytic activity needed for the conversion of the normal paraffins cannot be easily obtained, which is undesirable.


The synthesized organic template-containing zeolite that has preferably been washed and dried typically has alkali metal cations as counter cations, and incorporates the organic template in its porous structure. The zeolite containing an organic template, which is used for producing the hydroisomerization catalyst of the present invention is preferably in such a synthesized state, i.e., preferably, the zeolite has not been subjected to calcination treatment for removing the organic template incorporated therein.


The organic template-containing zeolite is subsequently ion-exchanged in a solution containing ammonium ions and/or protons. By the ion-exchange treatment, the counter cations contained in the organic template-containing zeolite are exchanged into ammonium ions and/or protons. At the same time, a portion of the organic template incorporated in the organic template-containing zeolite is removed.


The solution used for the ion-exchange treatment is preferably a solution that uses a solvent containing at least 50% by volume of water, and more preferably an aqueous solution. Examples of compounds for supplying ammonium ions into the solution include various inorganic and organic ammonium salts such as ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphate, and ammonium acetate. On the other hand, mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid are typically utilized as compounds for supplying protons into the solution. The ion-exchanged zeolite (herein, an ammonium-form zeolite) obtained by ion exchange of the organic template-containing zeolite in the presence of ammonium ions releases ammonia during subsequent calcination, and the counter cations are converted to protons to form Bronsted acid sites. Ammonium ions are preferred as the cationic species used for the ion exchange. The content of ammonium ions and/or protons contained in the solution is preferably set to 10 to 1000 equivalents relative to the total amount of the counter cations and organic template contained in the organic template-containing zeolite used.


The ion-exchange treatment may be applied to the organic template-containing zeolite support in powder form; alternatively, prior to the ion-exchange treatment, the organic template-containing zeolite may be mixed with an inorganic oxide that is a binder, and extruded, and the ion-exchange treatment may be applied to the resulting extruded body. However, if the above-mentioned extruded body is subjected to the ion exchange treatment without being calcined, the problems of collapsing and powdering of the extruded body will easily arise; therefore, it is preferred to subject the organic template-containing zeolite in powder form to the ion-exchange treatment.


The ion-exchange treatment is preferably performed according to a standard method, i.e., a method in which the zeolite containing an organic template is immersed in a solution containing ammonium ions and/or protons, preferably, an aqueous solution, and the solution is stirred or fluidized. The stirring or fluidization is preferably performed under heating to improve the ion-exchange efficiency. In the present invention, a method in which the aqueous solution is heated, boiled, and ion-exchanged under reflux is particularly preferred.


Further, in view of improving the ion-exchange efficiency, during the ion exchange of the zeolite in a solution, the solution is preferably exchanged with a fresh one once or twice or more, and more preferably exchanged with a fresh one once or twice. When the solution is exchanged once, the ion-exchange efficiency can be improved by, for example, immersing the organic template-containing zeolite in a solution containing ammonium ions and/or protons, and heating the solution under reflux for 1 to 6 hours, followed by exchanging the solution with a fresh one, and further heating under reflux for 6 to 12 hours.


By the ion-exchange treatment, substantially all of the counter cations such as an alkali metal in the zeolite can be exchanged into ammonium ions and/or protons. On the other hand, with respect to the organic template incorporated in the zeolite, although a portion of the organic template is removed by the ion-exchange treatment, it is generally difficult to remove the entire organic template even if the ion-exchange treatment is repeatedly performed, resulting in a portion of the organic template remaining inside the zeolite.


In this embodiment, a mixture containing ion-exchanged zeolite and a binder is heated at a temperature of 250 to 350° C. in a nitrogen atmosphere to obtain a support precursor.


The mixture containing the ion-exchanged zeolite and the binder is preferably a extruded body obtained by mixing an inorganic oxide into the ion-exchanged zeolite obtained by the above-mentioned method that is a binder, and extruding the obtained composition. The purpose of mixing an inorganic oxide into the ion-exchanged zeolite is to increase the mechanical strength of the support (in particular, a particulate support) obtained by calcining the extruded body to a degree that the support can withstand practical applications, however, the present inventors have found that the selection of the type of inorganic oxide affects the isomerization selectivity of the hydroisomerization catalyst. From this viewpoint, at least one inorganic oxide selected from alumina, silica, titania, boria, zirconia, magnesia, ceria, zinc oxide, phosphorus oxide, and a composite oxide containing a combination of two or more of these oxides is used as the above-mentioned inorganic oxide. Among the above, silica and alumina are preferred in view of further improving the isomerization selectivity of the hydroisomerization catalyst, and alumina is more preferred. The phrase “composite oxide containing a combination of two or more of these oxides” is a composite oxide containing at least two components from alumina, silica, titania, boria, zirconia, magnesia, ceria, zinc oxide, and phosphorus oxide, but is preferably an alumina-based composite oxide containing 50% by mass or more of an alumina component based on the composite oxide, and more preferably alumina-silica.


The proportion of the ion-exchanged zeolite to the inorganic oxide contained in the above-mentioned composition is preferably 10:90 to 90:10, and more preferably 30:70 to 85:15, in terms of the mass ratio of the ion-exchanged zeolite to the inorganic oxide. When this ratio is less than 10:90, the activity of the hydroisomerization catalyst tends to be insufficient, which is undesirable. Conversely, when the ratio is more than 90:10, the mechanical strength of the support obtained by extruding and calcining the composition tends to be insufficient, which is undesirable.


Although the method for mixing the above-mentioned inorganic oxide into the ion-exchanged zeolite is not particularly limited, a general method can be employed, such as a method in which a suitable amount of a liquid such as water is added to the powders of both components to form a viscous fluid, and the fluid is kneaded in a kneader or the like.


The composition containing the above-mentioned ion-exchanged zeolite and the above-mentioned inorganic oxide, or a viscous fluid containing the composition is formed by extrusion or the like, and is preferably dried, to form a particulate extruded body. Although the shape of the extruded body is not particularly limited, examples of the shape include a cylindrical shape, a pellet shape, a spherical shape, and an irregular tubular shape having a three leaf-shaped or four leaf-shaped cross section. Although the size of the extruded body is not particularly limited, the extruded body is preferably, for example, about 1 to 30 mm in long axis, and about 1 to 20 mm in short axis in view of the ease of handling, and the load density in the reactor or the like.


In this embodiment, the extruded body obtained as described above is preferably heated at a temperature of 250 to 350° C. in a N2 atmosphere to form the support precursor. A heating time is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours.


When the above-mentioned heating temperature is less than 250° C. in this embodiment, the organic template remains in a large amount, and zeolite pores are plugged by the remaining template. Isomerization active sites are considered to exist near pore-mouth; a reactive substrate cannot be diffused into the pores by pore blockage in the above-mentioned case; the active sites are covered, and thereby an isomerization reaction does not easily proceed, and the conversion rate of the normal paraffins tends to be hardly obtained sufficiently. On the other hand, when the heating temperature is more than 350° C., the isomerization selectivity of the obtained hydroisomerization catalyst is not sufficiently improved.


A lower limit temperature when the extruded body is heated to form the support precursor is preferably 280° C. or more. An upper limit temperature is preferably 330° C. or less.


In this embodiment, the above-mentioned mixture is preferably heated such that a potion of the organic template contained in the above-mentioned extruded body remains. Specifically, heating conditions are preferably set such that the amount of carbon in the hydroisomerization catalyst obtained by calcination after metal supporting, which will be described below, is 0.4 to 3.5% by mass, preferably 0.4 to 3.0% by mass, more preferably 0.4 to 2.5% by mass, and the micro-pore volume per unit mass of the catalyst is 0.02 to 0.12 cc/g, which will be described below, and the micro-pore volume per unit mass of the zeolite contained in the catalyst is 0.01 to 0.12 cc/g.


Next, the catalyst precursor in which the platinum salt and/or the palladium salt are/is contained in the above-mentioned support precursor is calcined at a temperature of 350 to 400° C., preferably 380 to 400° C., and more preferably 400° C. in an atmosphere containing molecular oxygen, to obtain a hydroisomerization catalyst in which platinum and/or palladium are/is supported on the support containing zeolite. The phrase “in an atmosphere containing molecular oxygen” means contacting with gas containing oxygen gas, and preferably air. A calcining time is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours.


Examples of the platinum salts include chloroplatinic acid, tetraamminedinitroplatinum, dinitroaminoplatinum, and tetraamminedichloroplatmum. Because the chloride salt generates hydrochloric acid during the reaction to possibly cause the corrosion of the apparatus, tetraamminedinitroplatinum that is a platinum salt in which platinum is highly dispersed other than the chloride salt is preferred.


Examples of the palladium salts include palladium chloride, tetraammine palladium nitrate, and diaminopalladium nitrate. Because the chloride salt generates hydrochloric acid during the reaction to possibly cause the corrosion of the apparatus, tetraammine palladium nitrate that is a palladium salt in which palladium is highly dispersed other than the chloride salt is preferred.


The amount of the active metal supported on the support containing the zeolite of this embodiment is preferably 0.001 to 20% by mass based on the mass of the support, and more preferably 0.01 to 5% by mass. When the amount of the supported metal is less than 0.001% by mass, it will be difficult to impart a predetermined hydrogenation/dehydrogenation function. Conversely, when the amount of the supported metal is more than 20% by mass, the conversion of hydrocarbons to lighter products on the active metal by cracking tends to easily proceed, to cause the yield of an intended fraction to decrease, and further to cause the catalyst costs to increase, which is undesirable.


When the hydroisomerization catalyst of this embodiment is used for hydroisomerization of a hydrocarbon oil containing many sulfur-containing compounds and/or nitrogen-containing compounds, it is preferred that the hydroisomerization catalyst contain, as active metals, a combination such as nickel-cobalt, nickel-molybdenum, cobalt-molybdenum, nickel-molybdenum-cobalt, or nickel-tungsten-cobalt in view of the persistence of catalytic activity. The amounts of these metals supported are preferably 0.001 to 50% by mass based on the mass of the support, and more preferably 0.01 to 30% by mass.


In this embodiment, the above-mentioned catalyst precursor is preferably calcined such that the organic template remaining in the above-mentioned support precursor remains. Specifically, heating conditions are preferably set such that the amount of carbon in the obtained hydroisomerization catalyst is 0.4 to 3.5% by mass, preferably 0.4 to 3.0% by mass, more preferably 0.4 to 2.5% by mass, and the micro-pore volume per unit mass of the catalyst is 0.02 to 0.12 cc/g and the micro-pore volume per unit mass of the zeolite contained in the catalyst is 0.01 to 0.12 cc/g. The amount of carbon in the hydroisomerization catalyst is measured by “combustion in oxygen gas flow—infrared absorption method”. Specifically, the catalyst is combusted in the oxygen gas flow to generate carbon dioxide gas and the amount of carbon is determined based on an infrared absorption amount of the carbon dioxide gas. Analysis equipments for carbon—sulfur (for example, EMIA-920V manufactured by HORIBA, Ltd.) are used for the measurement.


The micro-pore volume per unit mass of the hydroisomerization catalyst is calculated by a method referred to as nitrogen adsorption measurement. That is, the micro-pore volume per unit mass of the catalyst is calculated by analyzing an isothermal line of nitrogen physical adsorption and desorption measured at a liquid nitrogen temperature (−196° C.) for the catalyst, and specifically analyzing an isothermal line of nitrogen adsorption measured at a liquid nitrogen temperature (−196° C.) by a t-plot method. The micro-pore volume per unit mass of the zeolite contained in the catalyst is also calculated by the above-mentioned nitrogen adsorption measurement.


The micro-pore volume VZ per unit mass of the zeolite contained in the catalyst can be calculated according to the following expression from a value Vc of the micro-pore volume per unit mass of the hydroisomerization catalyst and a content ratio Mz (% by mass) of the zeolite in the catalyst, for example, when the binder has no micro-pore volume.






V
z
=V
c
/Mz×100


It is preferred that, subsequent to the calcination treatment, the hydroisomerization catalyst of the present invention is subjected to reduction treatment, preferably after the catalyst is loaded in the reactor for performing the hydroisomerization reaction. Specifically, the hydroisomerization catalyst is preferably subjected to the reduction treatment performed for about 0.5 to 5 hours in an atmosphere containing molecular hydrogen, and preferably under a stream of hydrogen gas, preferably at 250 to 500° C., and more preferably at 300 to 400° C. This step further ensures that high activity for dewaxing a hydrocarbon oil can be imparted to the catalyst.


An another embodiment of the hydroisomerization catalyst according to the present invention is a hydroisomerization catalyst that contains a support containing zeolite having a 10-membered ring one-dimensional porous structure and a binder, and platinum and/or palladium supported on the support, wherein the amount of carbon in the catalyst is 0.4 to 3.5% by mass, preferably 0.4 to 3.0% by mass, more preferably 0.4 to 2.5% by mass, and the micro-pore volume per unit mass of the catalyst is 0.02 to 0.12 cc/g, and the above-mentioned zeolite is derived from the ion-exchanged zeolite obtained by ion-exchanging organic template-containing zeolite containing an organic template and having the 10-membered ring one-dimensional porous structure in a solution containing ammonium ions and/or protons, and the micro-pore volume per unit mass of the zeolite contained in the catalyst is 0.01 to 0.12 cc/g.


The above-mentioned hydroisomerization catalyst can be produced by the method described above. The micro-pore volume per unit mass of the catalyst and the micro-pore volume per unit mass of the zeolite contained in the catalyst can be set to the above-mentioned range by suitably adjusting the mixing amount of the ion-exchanged zeolite in the mixture containing the ion-exchanged zeolite and the binder, the heating conditions of the mixture in the N2 atmosphere, and the heating conditions of the catalyst precursor in the atmosphere containing molecular oxygen.


The peroxide value of the material to be treated subjected to the hydrotreating in the first step is reduced to 30 ppm by mass or less. The material to be treated contains normal paraffins having 10 or more carbon atoms. In the hydroisomerization in the second step, the material to be treated may be contacted with the above-mentioned hydroisomerization catalyst in the presence of hydrogen. A portion or entire of the material to be treated containing the normal paraffins is converted to isoparaffins by the contact with the hydroisomerization catalyst.


It is noted that isomerization of the hydrocarbon oil refers to a reaction in which only the molecular structure of the hydrocarbon oil changes without a change in the number of carbon atoms (the molecular weight). It is noted that cracking of the hydrocarbon oil refers to a reaction that involves a decrease in the number of carbon atoms (molecular weight) of the hydrocarbon oil. In the catalytic dewaxing reaction utilizing the hydroisomerization catalyst, not only the isomerization but also a certain degree of cracking reaction of the hydrocarbon oil and isomerized products may occur. As long as the number of carbon atoms (the molecular weight) of the product of the cracking reaction is maintained within a predetermined range that permits the formation of an intended base oil, no problem is caused. That is, the cracked products may also be constituents of the base oil.


The reaction conditions of the hydroisomerization in the second step are as follows.


The temperature of the hydroisomerization reaction is preferably 200 to 450° C., and more preferably 220 to 400° C. When the reaction temperature is below 200° C., the isomerization of the normal paraffins contained in the material to be treated after the hydrotreating tends not to easily proceed, resulting in insufficient reduction and removal of the waxy components. Conversely, when the reaction temperature is more than 450° C., the cracking of the material to be treated tends to be significant, to result in a reduced yield of an intended hydrocarbon.


The pressure of the reaction field (in the reactor) in the hydroisomerization reaction is preferably 0.1 to 20 MPa, and more preferably 0.5 to 15 MPa. When the reaction pressure is below 0.1 MPa, catalyst degradation due to the formation of coke tends to be accelerated. Conversely, when the reaction pressure is more than 20 MPa, pressure resistance is required for the reactor, and thereby construction costs for the reactor tend to increase, to make it difficult to realize an economical process.


The liquid hourly space velocity of the material to be treated in the hydrotreating reaction is preferably 0.01 to 100 h−1, and more preferably 0.1 to 50 h−1. When the liquid hourly space velocity is less than 0.01 h−1, excessive cracking of the material to be treated tends to easily proceed, to result in lowered production efficiency for an intended hydrocarbon. Conversely, when the liquid hourly space velocity is more than 100 h−1, the isomerization of the normal paraffins contained in the material to be treated tends not to easily proceed, to result in insufficient reduction and removal of the waxy components.


The feed ratio of hydrogen to the material to be treated is preferably 100 to 1000 Nm3/m3, and more preferably 200 to 800 Nm3/m3. When the feed ratio is less than 100 Nm3/m3, and for example, the material to be treated contains sulfur and nitrogen compounds, hydrogen sulfide and ammonia gas produced by desulfurization and denitrification reactions that accompany the isomerization reaction tend to adsorb onto and poison the active metal on the catalyst. This tends to make it difficult to achieve predetermined catalytic performance. Conversely, if the feed ratio is more than 1000 Nm3/m3, hydrogen feed equipment having increased capacity tends to be required, which makes it difficult to realize an economical process.


The conversion rate of the normal paraffins in the hydroisomerization reaction is freely controlled by adjusting the reaction conditions such as the reaction temperature according to the use of the obtained hydrocarbon.


By the above-mentioned dewaxing method, it is possible to allow the isomerization (i.e., dewaxing) of the normal paraffins contained in the FT wax to proceed, while sufficiently suppressing the conversion of the normal paraffins to lighter products. Therefore, hydrocarbons containing 90% by volume or more of fractions having boiling points of more than 360° C. as calculated at ordinary pressure can be produced in high yield.


[Method for Producing Lubricant Base Oil]


In the method for producing a lubricant base oil of the present invention, a production oil obtained by the above-mentioned method for dewaxing the hydrocarbon oil is used. According to this embodiment, a base oil having a high content of an isomer having a branched-chain structure can be obtained. In particular, for a high-quality lubricant base oil, it is required that the content of normal paraffins is 0.1% by mass or less, however, according to this embodiment, a lubricant base oil that meets this level of requirement can be obtained in high yield.


When the lubricant base oil is produced, the material to be treated containing normal paraffins having 10 or more carbon atoms is preferably contacted with the hydroisomerization catalyst in the presence of hydrogen under conditions that give substantially 100% by mass conversion rate of the normal paraffins in the above-mentioned second step. Herein, the phrase “substantially 100% by mass conversion rate” means that the content of normal paraffins contained in the material to be treated after being contacted with the catalyst is 0.1% by mass or less. The conversion rate of the normal paraffins is defined by the following expression (I):






R=(1−M1/M2)×100  (I)


In the expression (I), R is the conversion rate (unit: % by mass) of the normal paraffins. M1 represents the total mass of the normal paraffins contained in the material to be treated after being contacted with a hydroisomerization catalyst and having Cn carbon atoms or more. M2 represents the total mass of the normal paraffins contained in the material to be treated before being contacted with the hydroisomerization catalyst and having Cn carbon atoms or more. Cn represents a minimum number of carbon atoms of the normal paraffins contained in the material to be treated before being contacted with the hydroisomerization catalyst and having 10 or more carbon atoms.


Examples of the above-mentioned method for improving the conversion rate of the normal paraffins include increasing the reaction temperature of the hydroisomerization in the second step. Because the content of the normal paraffins in a reaction product (lubricant base oil) is low when the conversion rate is high, the cold flow property of the lubricant base oil can be improved. However, increasing the reaction temperature promotes the cracking reactions of the material to be treated (FT wax) and isomerized products, thereby increasing conversion rate of the normal paraffins and increasing the amount of light fractions. Because the increase in the light fractions decreases the viscosity index of the hydrocarbon oil, in order to maintain the performance of the lubricant base oil within a predetermined range, it is necessary to separate and remove these light fractions by, for example, distillation. Particularly in the production of high-performance lubricant base oils such as Group II (a viscosity index of 80 or more and less than 120, and a saturated hydrocarbon content of 90% by mass or more, and a sulfur content of 0.03% by mass or less), Group III (a viscosity index of 120 or more, and a saturated hydrocarbon content of 90% by mass or more, and a sulfur content of 0.03% by mass or less), and Group III+ (a viscosity index of 140 or more, and a saturated hydrocarbon content of 90% by mass or more, and a sulfur content of 0.03% by mass or less) according to the classification of the grades of lubricant oils prescribed by the American Petroleum Institute (API) by catalytic dewaxing of the hydrocarbon feedstock, it is necessary to increase the conversion rate of the normal paraffins up to substantially 100%. With conventional methods for producing lubricant base oils using catalysts for catalytic dewaxing, the yields of the above-mentioned high-performance lubricant base oils are extremely low when dewaxing is performed under conditions that give substantially 100% conversion rate. As opposed to this, according to the method for producing a lubricant base oil of the present invention, it is possible to increase the yields of the above-mentioned high-performance lubricant base oils even when the hydroisomerization (second step) is performed under conditions that give substantially 100% conversion rate of the normal paraffins.


The reaction equipment for carrying out the first step (hydrotreating) and the reaction equipment for carrying out the second step (hydroisomerization treatment) are not particularly limited. Known equipment can be used as each equipment. The equipment may be any of a continuous flow-type, a batch-type, and a semi-batch-type, however, the continuous flow-type is preferred in view of productivity and efficiency. The catalyst layer of the equipment may be any of a fixed bed, a fluidized bed, and a stirred bed, however, the fixed bed is preferred in view of equipment costs or the like. The reaction phase is preferably a mixed phase of gas and liquid.


This embodiment may comprise the step of subjecting the material to be treated after the hydroisomerization treatment to hydrofinishing. In the hydrofinishing, the material to be treated is contacted with a hydrogenation catalyst supported on a metal, in the presence of hydrogen. Examples of the hydrogenation catalyst include alumina on which platinum is supported. By the hydrofinishing, it is possible to improve the hue and oxidation stability or the like of the reaction product obtained in the dewaxing step (second step), thereby enhancing the product quality. A catalyst layer for hydrofinishing may be provided downstream the catalyst layer of the hydroisomerization catalyst provided in the reactor for performing the dewaxing step (second step), and the hydrofinishing may be performed subsequent to the dewaxing step. The hydrofinishing may be carried out in reaction equipment separate from that of the dewaxing step. In this embodiment, the material to be treated after the hydrofinishing may be subjected to vacuum distillation to refine the base oil.


EXAMPLES

The present invention will be further described in detail below with reference to Examples, however, the present invention is not limited to the following Examples as long as Examples do not depart from the technical thought of the present invention.


[Production of Catalyst for Hydrotreating]


A mixture of USY zeolite, silica-alumina, and an alumina binder was cylindrically formed by an extrusion method. The mean particle size of the USY zeolite was 0.82 μm. The molar ratio of the silica/alumina of the USY zeolite was 37. The mass ratio of USY/silica-alumina/alumina binder in the mixture was 3:47:50. The diameter of the cylinder was about 1.5 mm and the length thereof was about 3 mm. The obtained extruded body was dried and calcined to obtain a support. This support was impregnated with an aqueous solution of tetraamminedinitroplatinum [Pt(NH3)4](NO3)2, to support platinum of 0.6 parts by mass based on the mass of the support. This was dried and calcined to obtain a catalyst for hydrotreating for the first step.


[Production of Hydroisomerization Catalyst E-1]


<Synthesis of Organic Template-Containing Zeolite ZSM-22>

Organic template-containing zeolite ZSM-22 made of a crystalline aluminosilicate having a Si/Al ratio of 45 was synthesized in the following procedure. Hereinafter, the zeolite ZSM-22 is referred to as the “ZSM-22.”


First, the following four types of aqueous solutions were prepared.


Solution A: A solution prepared by dissolving 1.94 g of potassium hydroxide in 6.75 mL of ion-exchange water.


Solution B: A solution prepared by dissolving 1.33 g of aluminum sulfate 18-hydrate in 5 mL of ion-exchange water.


Solution C: A solution prepared by diluting 4.18 g of 1,6-hexanediamine (an organic template) with 32.5 mL of ion-exchange water.


Solution D: A solution prepared by diluting 18 g of colloidal silica with 31 mL of ion-exchange water. Ludox AS-40 manufactured by Grace Davison was used as the colloidal silica.


Next, the solution A was added to the solution B, and the mixture was stirred until the aluminum component was completely dissolved. After the solution C was added to this mixed solution, the mixture of the solutions A, B, and C was poured into the solution D with vigorous stirring at room temperature. To the resulting mixture, 0.25 g of a powder of ZSM-22 that had been separately synthesized, and had not been subjected to any special treatment after the synthesis was further added as a “seed crystal” that promotes crystallization, to obtain a gel.


The gel obtained by the above-mentioned operation was transferred into a stainless steel autoclave reactor having an internal volume of 120 mL, and the autoclave reactor was rotated on a tumbling apparatus in a heated oven, to cause a hydrothermal synthesis reaction to take place. The temperature in the oven was 150° C. The execution time of the hydrothermal synthesis reaction was 60 hours. The rotational speed of the autoclave reactor was about 60 rpm. After the completion of the reaction, the reactor was opened after cooling, and dried overnight in a drier at 60° C., to obtain ZSM-22 having a Si/Al ratio of 45.


<Ion Exchange of ZSM-22 Containing Organic Template>


The above-mentioned ZSM-22 was subjected to ion-exchange treatment in an aqueous solution containing ammonium ions according to the following operation.


The ZSM-22 was taken in a flask, and 100 mL of 0.5 N-ammonium chloride aqueous solution per gram of the zeolite ZSM-22 was added thereto, and the mixture was heated under reflux for 6 hours. After cooling the heated mixture to room temperature, the supernatant was removed, and the crystalline aluminosilicate was washed with ion-exchange water. To the resulting product, the same amount of 0.5 N-ammonium chloride aqueous solution as above was added again, and the mixture was heated under reflux for 12 hours.


Subsequently, the solids were collected by filtration, washed with ion-exchanged water, and dried overnight in a drier at 60° C., to obtain ion-exchanged NH4-form ZSM-22. The ZSM-22 was an ion-exchanged zeolite containing an organic template.


<Mixing of Binder, Extruding, and Calcination>


The NH4-form ZSM-22 obtained above was mixed with alumina as a binder in a mass ratio of 7:3, a small amount of ion-exchange water was added thereto, and the mixture was kneaded. The obtained viscous fluid was loaded in an extruder and extruded to obtain a cylindrical extruded body having a diameter of about 1.6 min and a length of about 10 mm. This extruded body was heated in a N2 atmosphere for 3 hours at 300° C., to obtain a support precursor.


<Supporting of Platinum, and Calcination>


Tetraamminedinitroplatinum [Pt(NH3)4](NO3)2 was dissolved in an amount of ion-exchange water equivalent to the amount of water absorption of the support precursor that had been previously measured, to obtain an impregnation solution. This solution was impregnated in the above-mentioned support precursor by an incipient wetting method, to support platinum on the support precursor such that the amount of the platinum was 0.3% by mass based on the mass of the zeolite ZSM-22. Next, the obtained impregnation product (catalyst precursor) was dried overnight in a drier at 60° C., and then calcined under an air stream for 3 hours at 400° C., to obtain a hydroisomerization catalyst E-1 containing 0.56% by mass of carbon. The amount of carbon was measured by “combustion in oxygen gas flow—infrared absorption method”. EMIA-920V manufactured by HORIBA, Ltd. was used for the measurement.


Furthermore, the micro-pore volume per unit mass of the obtained hydroisomerization catalyst E-1 was calculated by the following method. First, in order to remove moisture adsorbing onto the hydroisomerization catalyst, pretreatment was performed to perform vacuum exhaust at 150° C. for 5 hours. Nitrogen adsorption measurement of the hydroisomerization catalyst after this pretreatment was performed at a liquid nitrogen temperature (−196° C.) using BELSORP-max manufactured by BEL Japan, Inc. The adsorption isothermal line of the measured nitrogen was analyzed by a t-plot method, to calculate the micro-pore volume (cc/g) per unit mass of the hydroisomerization catalyst. The micro-pore volume per unit mass of the hydroisomerization catalyst was 0.055 (cc/g).


Furthermore, the micro-pore volume Vz per unit mass of the zeolite contained in the hydroisomerization catalyst was calculated according to the expression Vz=Vc/Mz×100. In the expression, Vc represents the micro-pore volume per unit mass of the hydroisomerization catalyst, and Mz represents the content (% by mass) of the zeolite in the catalyst. When the nitrogen adsorption measurement of alumina used as the binder was performed as described above, it was confirmed that alumina does not have micropores. The micro-pore volume Vz was 0.079 (cc/g).


[Production of Hydroisomerization Catalyst E-2]


<Synthesis of Organic Template-Containing Zeolite ZSM-48>

Organic template-containing zeolite ZSM-48 having a Si/Al ratio of 45 was synthesized in the following procedure. Hereinafter, the zeolite ZSM-48 is referred to as the “ZSM-48.”


First, the following five types of reagents were prepared.


Reagent A: 2.97 g of sodium hydroxide.


Reagent B: 0.80 g of aluminum sulfate 18-hydrate.


Reagent C: 26.2 g of 1,6-hexanediamine (organic template).


Reagent D: 0.9 ml of a 98% sulfuric acid solution.


Reagent E: 75 g of a colloidal silica aqueous solution (SiO2 concentration: 40%). Ludox AS-40 manufactured by Grace Davison was used as the colloidal silica.


The above-mentioned reagents A, B, C, D, and E were added to 180 mg of ion-exchange water, and then completely dissolved by stirring for 2 hours at normal temperature.


The gel obtained by the above-mentioned stirring operation was transferred into a 100 mL internal volume stainless steel autoclave reactor, and the autoclave reactor was rotated on a tumbling apparatus in a heated oven, to cause a hydrothermal synthesis reaction to take place. The temperature in the oven was 160° C. The execution time of the hydrothermal synthesis reaction was 60 hours. The rotational speed of the autoclave reactor was about 60 rpm. After the completion of the reaction, the reactor was opened after cooling, and dried overnight in a drier at 60° C., to obtain ZSM-48 having a Si/Al ratio of 45.


<Ion Exchange of ZSM-48 Containing Organic Template>


The inn-exchange treatment of 7KM-48 was performed according to the same operation as that in the case of the catalyst E-1 except that the ZSM-48 was used instead of the ZSM-22. Ion-exchanged NH4-form ZSM-48 was obtained by this treatment. The ZSM-48 was an ion-exchanged zeolite containing an organic template.


A series of steps including mixing of the binder, extruding, calcining, supporting of platinum, and calcining were carried out in the same manner as in the catalyst E-1 except that the NH4-form ZSM-48 was used, to obtain a hydroisomerization catalyst E-2, wherein the amount of carbon in the hydroisomerization catalyst is 0.43% by mass, and the micro-pore volume per unit mass of the hydroisomerization catalyst is 0.078 cc/g, and the micro-pore volume per unit mass of the zeolite contained in the hydroisomerization catalyst is 0.111 cc/g.


[Production of Hydroisomerization Catalyst E-3]


<Synthesis of Organic Template-Containing Zeolite SSZ-32>

Organic template-containing zeolite SSZ-32 was synthesized in the following procedure. Hereinafter, the zeolite SSZ-32 is referred to as the “SSZ-32.”


Sodium hydroxide, aluminium sulfate, colloidal silica, isobutylamine (organic template), and an N-methyl-N-isopropyl-imidazolium cation were mixed to give the following molar ratios, and prepared:





SiO2/Al2O3=35.


The total amount (unit: g) of the isobutylamine and N-methyl-N′-isopropyl-imidazolium cation was 0.2 times the amount of SiO2.


The gel obtained by the above-mentioned operation was transferred into a 100 mL internal volume stainless steel autoclave reactor, and the autoclave reactor was rotated on a tumbling apparatus in a heated oven, to cause a hydrothermal synthesis reaction to take place. The temperature in the oven was 160° C. The execution time of the hydrothermal synthesis reaction was 60 hours. The rotational speed of the autoclave reactor was about 60 rpm. After the completion of the reaction, the reactor was opened after cooling, and dried overnight in a drier at 60° C., to obtain SSZ-32 having a Si/Al ratio of 45.


<Ion Exchange of SSZ-32 Containing Organic Template>


The ion-exchange treatment of SSZ-32 was performed according to the same operation as that in the case of the catalyst E-1 except that the SSZ-32 was used instead of the ZSM-22. Ion-exchanged NH4-form SSZ-32 was obtained by this treatment. The SSZ-32 was an ion-exchanged zeolite containing an organic template.


A series of steps including mixing of the binder, extruding, calcining, supporting of platinum, and calcining were carried out in the same manner as in the catalyst E-1 except that NH4-form SSZ-32 was used, to obtain a hydroisomerization catalyst E-3, wherein the amount of carbon in the hydroisomerization catalyst is 0.50% by mass, and the micro-pore volume per unit mass of the hydroisomerization catalyst is 0.062 cc/g, and the micro-pore volume per unit mass of the zeolite contained in the hydroisomerization catalyst is 0.089 cc/g.


Example 1
First Step

An FT synthetic oil was obtained using an FT synthesis reactor. The reaction temperature of an FT reaction was 210° C. A crude wax (FT wax) was obtained by the fractionation of the FT synthetic, oil. Components constituting the FT wax, and the content thereof were as follows.


Alcohols: 3.3% by mass.


Normal paraffin: 92.5% by mass.


Olefins: 4.2% by mass.


This crude wax was transported to a hydrotreating apparatus that was not adjacent to the FT synthesis reactor from the FT synthesis reactor without being treated. The peroxide value of the transported crude wax was measured by the following method.


The peroxide value was measured by reacting hydroperoxide in the crude wax with potassium iodide, and titrating free iodine with a sodium thiosulfate solution. The specific procedure of the measurement was as follows. First, the crude wax was precisely measured off. A liquid mixture of chloroform and glacial acetic acid (volume ratio 2:3) was added into the crude wax put into a stoppered Erlenmeyer flask, to dissolve the crude wax. Subsequently, while air in the flask was replaced by inactive gas, a saturated potassium iodide solution was added into the liquid mixture in which the crude wax was dissolved, and a stopper was immediately closed. After the liquid mixture in the flask was mixed for several minutes, a starch test solution as an indicator was added into the liquid mixture, and iodine in the liquid mixture was titrated with the sodium thiosulfate solution.


The peroxide value of the crude wax measured by the above-mentioned method was 430 ppm by mass.


[First Step: Hydrotreating]


The transported crude wax was subjected to hydrotreating using a hydrotreating apparatus. In the hydrotreating, the crude wax was contacted with the above-mentioned catalyst for hydrotreating in a hydrogen gas flow. The conditions of the hydrotreating were as follows.


A reaction temperature of hydrotreating: 290° C.


A reaction pressure of hydrotreating: 4.0 MPa.


A hydrogen/crude wax ratio: 340 Nm3/m3.


LHSV of crude wax: 2.0 h−1.


Generally, in the hydrotreating, the catalyst for hydrotreating is degraded with elapse of time to reduce a cracking rate. Therefore, in the above-mentioned hydrotreating, the reaction temperature was stepwise and continuously increased from 290° C. such that the cracking rate represented by the following expression (II) was maintained at 30%, to compensate for the reduced catalytic activity. The cracking rate was calculated from the analysis result of a production oil by a gas chromatography method. The upper limit value of the reaction temperature was set to 350° C. The temperature of 350° C. is a temperature at which polycyclic aromatic hydrocarbons are generated in the production oil of the hydrotreating to start to cause the degradation of the hue of the production oil. If the reaction temperature is increased to a temperature higher than 350° C. in order to compensate for the catalytic activity, the hue of the production oil is worsened to reduce the quality of the base oil product obtained from the production oil. That is, at the reaction temperature more than 350° C., it becomes difficult to satisfy both the compensation of the catalytic activity and the prevention of the degradation of the hue.





Cracking rate (% by mass)=Ma/Mb×100  (II)


Ma: the mass of a fraction contained in the production oil of the hydrotreating and having a boiling point of less than 360° C.


Mb: the mass of a fraction contained in the crude wax and having a boiling point of 360° C. or more.


A time t1 required to increase the reaction temperature of the hydrotreating to 350° C. from 290° C. was measured. The time t1 of Example 1 was 730 days. The short time t1 means that the catalyst is degraded in a short time. Therefore, the time t1 means the life of the catalyst for hydrotreating.


The production oil obtained by the hydrotreating of the crude wax was distilled, to obtain a fraction having a boiling point of 520° C. or less under ordinary pressure. A fraction having a boiling point of 520° C. or more was mixed with an FT production oil, and subjected to the hydrotreating again.


The peroxide value of the production oil (material to be treated) obtained by the above-mentioned hydrotreating was measured by the same method as the case of the crude wax before the hydrotreating. The peroxide value of the production oil of Example 1 was 0 ppm by mass.


[Second Step: Hydroisomerization Treatment]


The production oil of Example 1 was subjected to hydroisomerization treatment (dewaxing treatment) using a hydroisomerization catalyst according to the following procedure.


The above-mentioned catalyst E-1 was used as the hydroisomerization catalyst. Before the hydroisomerization treatment is performed, the catalyst E-1 was subjected to the following pretreatment. A stainless-steel reaction tube having an inner diameter of 15 mm and a length of 380 mm was loaded with 100 ml of the catalyst E-1. The catalyst E-1 in the reaction tube was subjected to reduction treatment for 12 hours under a hydrogen stream. In the reduction treatment, the average temperature of the catalyst layer (catalyst E-1) in the reaction tube was adjusted to 350° C. The hydrogen partial pressure in the reaction tube was adjusted to 3 MPa.


The production oil of Example 1 in which the peroxide value was maintained at 0 ppm by mass was passed in the above-mentioned reaction tube after the reduction treatment, to subject the production oil to the hydroisomerization treatment. The reaction temperature of the hydroisomerization was adjusted to the range of 310 to 330° C. The hydrogen partial pressure in the reaction tube during the hydroisomerization was adjusted to 3 MPa. LHSV of the production oil introduced into the reaction tube was adjusted to 1.0 h−1. A hydrogen/production oil ratio was adjusted to 500 Nm3/m3. The reaction time of the hydroisomerization was 72 hours. The hydroisomerization product was collected and analyzed.


Subsequently, the hydrogen partial pressure, the LHSV, and the hydrogen/production oil ratio were maintained at the above-mentioned values, and the reaction temperature was increased stepwise to about 350° C., to increase the conversion rate of the normal paraffins as defined by the above-mentioned expression (I). That is, at a plurality of reaction temperatures, the hydroisomerization reactions were caused to proceed. After the hydroisomerization reaction was continued at each reaction temperature for 72 hours and the reaction product was stabilized, the reaction product was collected and analyzed. The conversion rate of the normal paraffins in the hydroisomerization at each reaction temperature was calculated using the above-mentioned expression (I) based on the analysis result.


[Separation and Recovery Steps of Lubricant base oil Fractions]


Of the reaction products of the hydroisomerization treatment at the reaction temperatures, each of the reaction products obtained at reaction temperatures at which the conversion rate of the normal paraffins was 100% was fractionated according to the following operation. The following lubricant base oil fractions were separated and recovered by the fractionation.


Each of the reaction products obtained at reaction temperatures at which the conversion rate of the normal paraffins was 100% was fractionated into naphtha, kerosene and gas oil fractions, and heavy fractions. The heavy fractions were further fractionated into a lubricant base oil fraction 1 and a lubricant base oil fraction 2. The lubricant base oil fraction 1 means a lubricant base oil fraction having a boiling point range of 330 to 410° C. and having a kinematic viscosity at 100° C. of 2.7±0.1 mm2/s. The lubricant base oil fraction 2 means a lubricant base oil fraction having a boiling point range of 410 to 450° C. and having a kinematic viscosity at 100° C. of 4.0±0.1 mm2/s.


The lowest initial reaction temperature in the reaction temperatures of the hydroisomerization at which the lubricant base oil fraction 2 having a pour point of −22.5° C. or less and a viscosity index (VI) of 140 or more was generated was defined as Tc (° C.). The reaction temperature Tc of the hydroisomerization treatment of Example 1 was 325° C. Table 1 shows the yields of the lubricant base oil fractions 1 and 2 obtained by the hydroisomerization treatment at the reaction temperature Tc, and the pour point and viscosity index of the lubricant base oil fraction 2.


[Life Evaluation of Hydroisomerization Catalyst]


Generally, in the hydroisomerization treatment, the hydroisomerization catalyst is degraded with elapse of time to decrease the conversion rate of the normal paraffins. Therefore, in the hydroisomerization treatment in which the initial reaction temperature was Tc, the reaction temperature was gradually and continuously increased to 350° C. from Tc such that the conversion rate of the normal paraffins was maintained at 100%, to compensate for the reduced catalytic activity. The conversion rate was calculated from the analysis result of the reaction product of the hydroisomerization treatment by the gas chromatography method. A time t2 required to increase the reaction temperature of the hydroisomerization treatment to 350° C. from Tc was measured. The time t2 of Example 1 was 670 days. The short time t2 means that the catalyst is degraded in a short time. Therefore, the time t2 means the life of the hydroisomerization catalyst.


Example 2

In Example 2, in a second step, not the catalyst E-1 but the catalyst E-2 was used as a hydroisomerization catalyst. In the same manner as in Example 1 except for this point, hydrotreating, hydroisomerization treatment, and separation and recovery steps of a lubricant base oil fraction of Example 2 were performed. A peroxide value of a crude wax before the hydrotreating, a catalyst life t1, a peroxide value of a production oil (material to be treated) obtained by the hydrotreating, a reaction initial temperature Tc, yields of lubricant base oil fractions 1 and 2, a pour point and viscosity index of the lubricant base oil fraction 2, and a catalyst life t2 in Example 2 were obtained in the same manner as in Example 1. These are shown in Table 1.


Example 3

In Example 3, in a second step, not the catalyst E-1 but the catalyst E-3 was used as a hydroisomerization catalyst. In the same manner as in Example 1 except for this point, hydrotreating, hydroisomerization treatment, and separation and recovery steps of a lubricant base oil fraction of Example 3 were performed. A peroxide value of a crude wax before the hydrotreating, a catalyst life t1, a peroxide value of a production oil (material to be treated) obtained by the hydrotreating, a reaction initial temperature Tc, yields of lubricant base oil fractions 1 and 2, a pour point and viscosity index of the lubricant base oil fraction 2, and a catalyst life t2 in Example 3 were obtained in the same manner as in Example 1. These are shown in Table 1.


Comparative Example 1

In Comparative Example 1, an FT synthetic oil was produced using an FT synthesis reactor set in a GTL plant apart from Example 1. A crude wax was obtained by the fractionation of the FT synthetic oil. The peroxide value of the crude wax of Comparative Example 1 was measured in the same manner as in Example 1. The peroxide value of the crude wax of Comparative Example 1 was 2420 ppm by mass. This crude wax was subjected to hydrotreating under the same reaction conditions as those of Example 1. The life t1 of a catalyst for hydrotreating of Comparative Example 1 was measured in the same manner as in Example 1. The life t1 of the catalyst for hydrotreating of Comparative Example 1 was 135 days.


A production oil (material to be treated) obtained by the hydrotreating was transported to a reaction tube for hydroisomerization treatment used in Example 1 from the GTL plant. The transporting period was two months. The peroxide value of the production oil after the transportation (just before hydroisomerization treatment) was measured in the same manner as in Example 1. The peroxide value of the production oil after the transportation of Comparative Example 1 was 34 ppm by mass.


The hydroisomerization treatment and the separation and recovery steps of a lubricant base oil fraction of Comparative Example 1 were performed in the same manner as in Example 1 except for the above matters. A reaction initial temperature Tc, yields of lubricant base oil fractions 1 and 2, a pour point and viscosity index of the lubricant base oil fraction 2, and a catalyst life t2 in Comparative Example 1 were obtained in the same manner as in Example 1. These are shown in Table 1.


Comparative Example 2

In Comparative Example 2, an FT synthetic oil was produced using an FT synthesis reactor set in a GTL plant apart from Example 1 and Comparative Example 1. A crude wax was obtained by the fractionation of the FT synthetic oil. The peroxide value of the crude wax of Comparative Example 2 was measured in the same manner as in Example 1. The peroxide value of the crude wax of Comparative Example 2 was 3700 ppm by mass. This crude wax was subjected to hydrotreating under the same reaction conditions as those of Example 1. The life t1 of a catalyst for hydrotreating of Comparative Example 2 was measured in the same manner as in Example 1. The life t1 of the catalyst for hydrotreating of Comparative Example 2 was 93 days.


A production oil (material to be treated) obtained by the hydrotreating was transported to a reaction tube for hydroisomerization treatment used in Example 1 from the GTL plant. The transporting period was four months. The peroxide value of the production oil (material to be treated) after the transportation was measured in the same manner as in Example 1. The peroxide value of the production oil after the transportation (just before hydroisomerization treatment) of Comparative Example 2 was 128 ppm by mass.


The hydroisomerization treatment and the separation and recovery steps of a lubricant base oil fraction of Comparative Example 2 were performed in the same manner as in Example 1 except for the above matters. A reaction initial temperature Tc, yields of lubricant base oil fractions 1 and 2, a pour point and viscosity index of the lubricant base oil fraction 2, and a catalyst life t2 in Comparative Example 2 were obtained in the same manner as in Example 1. These are shown in Table 1.


In the following Table 1, a “peroxide value 1” means the peroxide value of the crude wax before the hydrotreating. The “life t1” means the life of the catalyst for hydrotreating in the hydrotreating of the crude wax. A “peroxide value 2” means the peroxide value just before the hydroisomerization treatment of the production oil obtained by the hydrotreating. The “catalyst” means a hydroisomerization catalyst. The “life t2” means the life of the hydroisomerization catalyst in the hydroisomerization treatment of the production oil.

















Table 1








Peroxide

Peroxide




Fraction 2

















value 1
Life
value 2


Life
Yield (%)
Pour



















(ppm by
t1
(ppm by

Tc
t2
Fraction
Fraction
point
Viscosity


Table 1
mass)
(day)
mass)
Catalyst
(° C.)
(day)
1
2
(° C.)
index




















Example 1
430
730
0
E-1
325
670
30
62
−27.5
148


Example 2
430
730
0
E-2
320
660
34
57
−25.0
145


Example 3
430
730
0
E-3
325
640
30
57
−27.5
148


Comparative
2420
135
34
E-1
327
600
39
62
−27.5
148


Example 1












Comparative
3700
93
128
E-1
330
520
28
63
−27.5
148


Example 2



















INDUSTRIAL APPLICABILITY

Because the present invention improves the life of the hydroisomerization catalyst and enables effective hydroisomerization treatment (dewaxing treatment) of the hydrocarbon oil at low cost, the present invention is suitable for the method for producing the lubricant base oil or the like.

Claims
  • 1. A method for dewaxing a hydrocarbon oil comprising: a first step of subjecting a hydrocarbon oil in which a peroxide value is 100 ppm by mass or more to hydrotreating to obtain a material to be treated in which a peroxide value is 30 ppm by mass or less; anda second step of subjecting the material to be treated in which a peroxide value is 30 ppm by mass or less to hydroisomerization treatment using a hydroisomerization catalyst.
  • 2. The method for dewaxing a hydrocarbon oil according to claim 1, wherein the hydrocarbon oil is synthesized by a Fischer-Tropsch reaction.
  • 3. The method for dewaxing a hydrocarbon oil according to claim 1, wherein the hydroisomerization catalyst contains zeolite; and the zeolite contains an organic template, and has a one-dimensional porous structure including a 10-membered ring.
  • 4. The method for dewaxing a hydrocarbon oil according to claim 3, wherein the zeolite is at least one selected from the group consisting of zeolite ZSM-22, zeolite ZSM-23, zeolite SSZ-32, and zeolite ZSM-48.
  • 5. The method for dewaxing a hydrocarbon oil according to claim 1, wherein the material to be treated contains normal paraffins having 10 or more of carbon number; and the material to be treated is contacted with the hydroisomerization catalyst in the presence of hydrogen in the second step.
  • 6. A method for producing a lubricant base oil using the method according to claim 1.
  • 7. The method for producing a lubricant base oil according to claim 6, further comprising a step of subjecting the material to be treated after the hydroisomerization treatment to hydrofinishing.
  • 8. The method for producing a lubricant base oil according to claim 7, further comprising a step of subjecting the material to be treated after the hydrofinishing to vacuum distillation.
Priority Claims (1)
Number Date Country Kind
2012-082257 Mar 2012 JP national
PCT Information
Filing Document Filing Date Country Kind
PCT/JP2013/059599 3/29/2013 WO 00