Patent Application
20130253238
The present invention relates to a method for producing a lubricating base oil with a low cloud point (<−5° C.) and a high viscosity index (>120).
Patent CN101134910A discloses a method for lowering the pour point and the cloud point of a lubricating oil distillate. In the method, a catalytic dewaxing process is adopted, and the catalyst includes nickel metal as an active component, which is contained in a support of a ZSM-5 molecular sieve. The pour point of a light deasphalted hydrotreated oil can be lowered from 9° C. to −24° C., and the cloud point can be lowered from 12° C. to −16° C. The method has the following obvious disadvantage: the yield and the viscosity of the base oil product will be greatly decreased when the wax content in the feed stock is high, and the drops of the pour point and the cloud point need to be increased.
Patent CN1524929 discloses a method for lowering the cloud point of a lubricating base oil, in which a lube stock is first subjected to solvent pre-dewaxing, the pour point of the dewaxed oil is −5° C. to 15° C.; the pre-dewaxed oil is subjected to hydrotreating to reduce the sulfur content and the nitrogen content; the pre-dewaxed oil after hydrotreating is subjected to isodewaxing, to obtain a lubricating base oil with a low cloud point. In order to avoid increase of the severity of the reaction and a resulted severe cracking reaction, in the method, most of the wax needs to be removed through a solvent pre-dewaxing process, and then a hydrotreating and isodewaxing process is performed. The pour point of the dewaxed oil of the method should be not higher than 15° C., otherwise the cloud point of the isomerization product cannot be lowered to less than 0° C., even cannot be lowered to less than 5° C.
U.S. Pat. No. 6,699,385 discloses a method for lowering the cloud point through an isodewaxing process. In order to avoid increase of the severity of the reaction and a resulted severe cracking reaction, the waxy feed stock needs to be first fractionated, and a light fraction is subjected to isodewaxing, and the cloud point can only be decreased to about 0° C.
All the methods for dewaxing a lubricating base oil disclosed in the published patents and documents above do not clarify or imply a method for producing a base oil with a low pour point, a low cloud point and a high viscosity index by an isomerization-asymmetrical cracking reaction process, and compared with the method disclosed in the published patents and documents, the yield of a base oil, especially the yield of a heavy base oil of an isomerization-symmetric cracking reaction process is higher.
The present invention is directed to a method for producing a lubricating base oil having a low cloud point (<−5° C.) and a high viscosity index (>120), wherein a highly waxy heavy fraction oil having an initial boiling point of 300° C. to 460° C., a wax content of 5% or more, a pour point of −20° C. or more and a cloud point of −5° C. or more is used as raw material to produce a API (American Petroleum Institute) II, III (see the classification standard in Table 1) type lubricating base oil having a low pour point and a high viscosity index by a hydrogenation pre-refining-isomerization/asymmetrical cracking-supplementary refining three-stage hydrogenation process.
The production method provided by the present invention includes: (1) a hydrorefining process: at a certain hydrogen pressure, a waxy feed stock contacts a hydrorefining catalyst and is subjected to desulfurization, denitrogenation, aromatic saturation and an ring-opening reaction, products of the hydrorefining reaction are separated by a stripping column, and the bottom fraction enters a hydroisomerization/asymmetrical cracking process; (2) a hydroisomerization/asymmetrical cracking process: at a certain hydrogen pressure, a bottom product of the stripping column contacts an isomerization-asymmetrical cracking catalyst and is subjected to isomerization-asymmetrical cracking and a hydrogenation saturation reaction, to obtain a product having a low pour point, a low cloud point, a low aromatic content and a high viscosity index, and then all the product directly enters a hydrofinishing process; (3) a hydrofinishing process: at a certain hydrogen pressure, the isomerization-asymmetrical cracking reaction product contacts a hydrofinishing catalyst and is subjected to a hydrogenation saturation reaction, to obtain a hydrofinishing oil having good light stability and thermal stability; and (4) a product separation process: the product obtained in the hydrofinishing process is separated into a gas phase product and a liquid phase product by a hot high-pressure separator and a cold low-pressure separator, the liquid product passes through a normal-pressure fractionating column and a reduced-pressure fractionating column to extract naphtha, kerosene, diesel oil and light, middle and heavy lubricating base oil having a low pour point and a high viscosity index.
According to the method of the present invention, the feed stock includes anyone of furfural refined oil, foots oil, cerate (soft wax), propane deasphalted oil (DAO), hydrocracking unconverted oil (UCO), Fischer-Tropsch wax, vacuum gas oil and other waxy oils or a mixture thereof.
According to the method of the present invention, the hydrorefining catalyst includes 60 wt % to 90 wt % of one or more of alumina, silica and titania, and 10 wt % to 40 wt % of one or more of molybdenum trioxide, tungsten trioxide, nickel oxide and cobalt oxide.
According to the method of the present invention, before use, the hydrorefining catalyst is pre-sulfurated by hydrogen sulfide or sulfur-containing feed stock at a temperature of 150 to 350° C. in the presence of hydrogen. This type of pre-vulcanization may be carried out ex situ or in situ.
According to the method of the present invention, the hydrorefining process conditions are: reaction temperature: 350° C. to 410° C., hydrogen partial pressure: 10 MPa to 18 MPa, space velocity (LHSV): 0.5 h−1 to 2.0 h−1, and volume ratio of hydrogen to oil:300 Nm3/m3 to 1000 Nm3/m3.
According to the method of the present invention, the oil obtained by stripping separation of the hydrorefining product has a total sulfur content of no higher than 10 μg/g and a total nitrogen content of no higher than 5 μg/g.
According to the method of the present invention, the isomerization-asymmetrical cracking catalyst is at least one of the following one-dimensional 10-membered ring mesoporous composite molecular sieves: a ZSM-22/ZSM-23 composite molecular sieve, a ZSM-23/ZSM-22 composite molecular sieve, a ZSM-5/SAPO-11 composite molecular sieve, a ZSM-22/SAPO-11 composite molecular sieve, a ZSM-23/SAPO-11 composite molecular sieve, an EU-1/SAPO-11 composite molecular sieve, and a NU-87/SAPO-11 composite molecular sieve. The content of the molecular sieve is 40% to 80%, and the rest is alumina and at least one group VIII noble metal, where the noble metal is Pt and/or Pd and has a content of 0.3 wt % to 0.6 wt %. The average pore diameter of the catalyst is 0.3 nm to 0.8 nm, the average pore volume is 0.1 ml/g to 0.4 mug, and the BET specific surface area is 120 m2/g to 300 m2/g.
According to the method of the present invention, before use, the isomerization/asymmetrical cracking catalyst needs to be pre-reduced at a temperature of 150 to 450° C. in the presence of hydrogen.
According to the method of the present invention, the isomerization/asymmetrical cracking process conditions are: reaction temperature: 260° C. to 410° C., hydrogen partial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h−1 to 3.0 h−1, volume ratio of hydrogen to oil:300 Nm3/m3 to 1000 Nm3/m3.
According to the method of the present invention, the hydrofinishing catalyst includes amorphous silica-alumina and at least one group VIII noble metal.
According to the method of the present invention, the hydrofinishing catalyst has a ratio of SiO2:Al2O3 of 1:1 to 9, an average pore radius of 1.0 nm to 5.0 nm, a pore volume of 0.3 ml/g to 1.0 ml/g, and a BET specific surface area of 260 m2/g to 450 m2/g. The noble metal is Pt and/or Pd, and the content of the noble metal is 0.3 wt % to 0.6 wt %.
According to the method of the present invention, before use, the hydrofinishing catalyst is generally pre-reduced at a temperature of 150° C. to 450° C. in the presence of hydrogen.
According to the method of the present invention, the hydrofinishing reaction conditions are: reaction temperature: 180° C. to 320° C., hydrogen partial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h−1 to 3.0 h−1, volume ratio of hydrogen to oil:300 Nm3/m3 to 1000 Nm3/m3.
According to the method of the present invention, the normal-pressure distillation and reduced-pressure distillation process are to separate the oil mixture after supplementary refining by normal-pressure distillation and reduced-pressure distillation, to obtain a naphtha, a middle fraction oil and a lubricating base oil.
The present invention is further described with the following examples.
The hydrorefining catalyst and the supplementary refining catalyst used in the examples of the present invention and preparation method thereof are briefly described as follows:
Same hydrorefining catalyst and hydrofinishing catalyst are used in the examples and comparative examples of the present invention. The hydrorefining catalyst is prepared according to the following process: pseudo-boehmite having an appropriate pore structure is selected and used to prepare a strip-like support having a clover-shaped cross section, after the support is dried and baked, Ni element and Mo element are loaded on the alumina support by an impregnation method, and then dried and baked to obtain a hydrorefining catalyst, wherein the NiO content is 4.20%, the MoO3 content is 18.3%, and the rest is alumina, the specific surface area is 175 m2/g, and the pore volume is 0.45 cm3/g.
The isomerization/asymmetrical cracking catalyst used in the examples is a 0.5% Pt/ZSM-22/SAPO-11 catalyst prepared according to the method described in Example 12 of patent CN 1762594A.
In a method for preparing the hydrofinishing catalyst, amorphous silica-alumina used as support is prepared by using cocurrent flow fixed pH value and silica-alumina coprecipitation. After being dried and baked, the support is squeezed into a strip having a clover-shaped cross section, and dried and baked, and then metal Pt is loaded by an impregnation method, and then dried and baked to obtain a hydrofinishing catalyst, wherein the Pt content is 0.51%, the rest is silica and alumina, the ratio of SiO2:Al2O3 is 1:6.3, the specific surface area is 305 cm2/g, and the pore volume is 1.08 cm3/g.
A SAPO-11 molecular sieve was synthesized by a method described in Example 18 of U.S. Pat. No. 4,440,871. Pseudo-boehmite is incorporated into a SAPO-11 molecular sieve powder in a ratio of 70% SAPO-11 molecular sieve to 30% pseudo-boehmite, and then a small amount of an adhesive such as an aqueous solution of HNO3 was added, blended and shaped into a strip of φ1.2 mm, baked at 110° C. for 24 hours and at 600° C. for 24 hours, and pulverized into particles having a length of 1 mm to 2 mm. A sufficient amount of support particles was impregnated in a suitable amount of a Pt(NH3)4Cl2 solution having a concentration of 3% for 16 hours by a common pore filling impregnation method, and then dried at 120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml of the prepared catalyst was pre-reduced by pure hydrogen in situ on a high-pressure hydrogenation reaction experimental device having a catalyst load of 200 ml to obtain a 0.5% Pt/SAPO-11 catalyst. The isodewaxing catalyst reduction conditions are: hydrogen flow rate: 2000 mL/h, the temperature was raised to 250° C. at a rate of 5° C./min and maintained at 250° C. for 2 hours. Then, the temperature was raised to 450° C. at a rate of 5° C./min and maintained at 450° C. for 2 hours, and the reaction temperature was adjusted in a hydrogen flow. The hydrogenation pre-refining-isodewaxing-hydrofinishing process shown in
According to the process shown in
Product distribution comparison of Example 1 and Comparative Example 1 is shown in Table 4, and main product properties are shown in Table 5.
According to the process shown in
It can be seen from Tables 2 to 5 and
A ZSM-22 molecular sieve was synthesized by the method described in Example 2 of U.S. Pat. No. 5,783,168. Pseudo-boehmite is incorporated into a ZSM-22 molecular sieve powder in a ratio of 70% ZSM-22 molecular sieve to 30% pseudo-boehmite, and then a small amount of an adhesive such as an aqueous solution of HNO3 was added, blended and shaped into a strip of φ1.2 mm, baked at 110° C. for 24 hours and at 600° C. for 24 hours, and breaked into particles having a length of 1 mm to 2 mm. A sufficient amount of support particles was impregnated in a suitable amount of a Pt(NH3)4Cl2 solution having a concentration of 3% for 16 hours by a common pore filling impregnation method, and then dried at 120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml of the prepared catalyst was pre-reduced by pure hydrogen in situ in a high-pressure hydrogenation reaction experimental device having a catalyst load of 200 ml to obtain 0.5% of Pt/ZSM-22. The catalyst reduction conditions were the same as those in Comparative Example 1. A paraffin base 200SN dewaxed oil was used as a raw material, the physical and chemical properties thereof are shown in Table 6, and a hydrorefining-isodewaxing-hydrofinishing series process (shown in
The process, experimental device and feed stock were the same as those in Comparative Example 2. The other reaction conditions were the same as those in Comparative Example 2 except that the temperature of the isomerization/asymmetrical cracking reaction was 325° C., and the liquid hourly space velocity was 1.2 h−1.
The product distributions of the reactions of Example 2 and Comparative Example 2 are shown in Table 8, and main properties of the products are shown in Table 9.
It can be seen from Tables 6 to 9 and
According to the process shown in
According to the process shown in
It can be seen from Tables 10 to 13 that the distribution of the product of the isomerization/asymmetrical cracking in Example 3 is similar to those of the products of isomerization/asymmetrical cracking in Examples 1 and 2, the product mainly includes light component products (gas and naphtha) and a 2 cst base oil product, and the yields of the two products are 17.32% and 70.83% respectively, and the diesel yield is 11.87%, indicating a bimodal distribution of a high yield of the light component product and the heavy component product and a low yield of the middle fraction. The product distribution in Example 4 is similar to that in Example 3, and the feature of bimodal distribution is more significant. The pour points and the cloud points of the 2 cst and 6 cst base oil products of Examples 3 and 4 are very low, and the viscosity index of the 6 cst base oil is up to 123, which meets the requirements of API Group III base oil.
According to the process shown in
According to the process shown in
It can be seen from Tables 14 to 17 that the fractions of 650SN cerate and 150BS cerate are very heavy, and the pour points thereof are very high. With regard to the two types of heavy and waxy feed stocks, the reduction of the pour point of the base oil needs to be up to 78° C. to achieve a pour point of base oil of no higher than −15° C. The features of high yields of small-molecule products (gas and naphtha) and big-molecule products (8 cst and 20 cst base oils) generated by the hydrorefining-isomerization/asymmetrical cracking-hydrofinishing and low yield of the middle fraction oil (diesel +2 cst base oil) are significant. The viscosity index of the heavy product having a low pour point is extremely high, which can be up to 140, and the pour point and the cloud point of the heavy product can be decreased to a very low level.
A hydrocracking UCO is a heavy fraction oil generated from a reduced-pressure fraction oil by a hydrorefining-hydrocracking reaction, the impurities such as sulfur and nitrogen have been removed, and most of the aromatic hydrocarbons have been subjected to hydrosaturation and ring-opening, such that the hydrocracking UCO needs not to be subjected to a hydrorefining reaction to remove sulfur and nitrogen, and needs not to be subjected to a hydrorefining-reaction to improve the viscosity index, and the isomerization-asymmetrical cracking/hydrofinishing shown in
An Fischer-Tropsch wax is a hydrocarbon product with high-carbon-number long-chain normal paraffins as the main component synthesized in the presence of a Co-based catalyst. The wax mainly includes C8 to C45 normal paraffins, and the distribution of maximum carbon number is around C18. After cutting off components distillated at less than 320° C., the distribution of maximum carbon number of the Fischer-Tropsch wax is slight shifted to a higher carbon number.
In the present invention, the highly waxy heavy fraction oil having an initial boiling point of 300° C. to 460° C., a wax content of no lower than 5%, a pour point of no lower than −20° C., and a cloud point of no lower than −5° C. is used as a feed stock to produce a API (American Petroleum Institute) Group II or Group III (see the classification standard in Table 1) type lubricating base oil having a low pour point and a high viscosity index by a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing three-stage hydrogenation process, wherein a critical reaction process of hydrogenation isomerization-asymmetrical cracking is involved. The isomerization/asymmetrical cracking reaction include two chemical reactions, namely, an isomerization reaction and an asymmetrical cracking reaction. When the isomerization is carried out, the linear paraffins having a high pour point and big-molecular and less-branched iso-paraffins with high pour point and high viscosity index in the feed stock are subjected to an asymmetrical cracking reaction at the same time. The so-called asymmetrical cracking reaction refers to a hydrocracking reaction occurs at a C—C bond close to the two ends of the paraffin, and a big-molecule and a small molecule are generated, wherein the small molecule belongs to the gas and naphtha fraction, and the big-molecule belongs to the lubricating base oil fraction.
In the asymmetrical cracking reaction, a 10-membered ring composite molecular sieve having a special pore structure is used as a catalyst support to enhance the restriction of the catalyst pores on the internal diffusion of normal paraffins and less-branched iso-paraffins, such that the cracking reaction preferably occurs at a position close to the two ends of the normal paraffins, thereby significantly improving the yield of the base oil product, especially that of the heavy base oil product.
The isomerization/asymmetrical cracking reaction is characterized in that the product has a bimodal distribution, that is, the yields of the light components (gas and naphtha) and the heavy base oil having a low pour point and a low cloud point are high, and the yield of a middle fraction oil (kerosene and diesel) is low. The method can solve the problems of low yield of target product, high pour point and cloud point, high aromatic content and low viscosity index and the like in the production of lubricating base oil from heavy highly waxy oil by physical processes such as solvent refining and solvent dewaxing and/or chemical processes such as hydrotreating, catalytic dewaxing, hydrotreating and hydrocracking. The process has the advantages of good adaptability to heavy highly waxy feed stock, high yield of the heavy base oil product with good properties such as viscosity, viscosity index, pour point and cloud point of the product and co-production of naphtha and a small amount of a middle fraction oil.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201010274479.X | Sep 2010 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN11/00946 | 6/3/2011 | WO | 00 | 3/5/2013 |
