Patent Application
20180355264
Systems and methods are provided for production of diesel and lubricant oil base stocks from waxy whole crude oil.
Crude petroleum may be distilled and fractionated into many products such as gasoline, kerosene, jet fuel, asphaltenes, and the like. One portion of the crude petroleum form the base of lubricating base oils used in, inter alia, the lubricating of internal combustion engines. Lube oil users are demanding ever increasing base oil quality, and refiners are finding that their available equipment is becoming less and less able to produce base oils that meet these higher quality specifications. New processes are required to provide refiners with the tools for preparing high quality modern base oils, particularly using existing equipment at lower cost and with safer operation.
Finished lubricants used for such things as automobiles, diesel engines, and industrial applications generally are comprised of a lube base oil and additives. In general, a few lube base oils are used to produce a wide variety of finished lubricants by varying the mixtures of individual lube base oils and individual additives. Typically, lube base oils are simply hydrocarbons prepared from petroleum or other sources. Lube base oils are normally manufactured by making narrow cuts of vacuum gas oils from a crude vacuum tower. The cut points are set to control the final viscosity and flash point of the lube base oil.
Group I base oils, those with greater than 300 ppm sulfur and 10 wt % aromatics, are generally produced by first extracting a vacuum gas oil (or waxy distillate) with a polar solvent, such as N-methyl-pyyrolidone, furfural, or phenol. The resulting waxy raffinates produced from solvent extraction processes are then dewaxed, either catalytically with the use of a dewaxing catalyst such as ZSM-5, or by solvent dewaxing. The resultant base oil may be hydrofinished to improve color and other lubricant properties.
Group II base oils, those with less than 300 ppm sulfur and 10 wt % aromatics, and with a viscosity index range of 8-120, are typically produced by hydrocracking followed by selective catalytic dewaxing and hydrofinishing. Hydrocracking upgrades the viscosity index of the entrained oil in the feedstock by ring cracking and aromatics saturation. The degree of aromatics saturation is limited by the high temperature (300-450° C.) of the hydrocracking stage. In the second stage of the process, the hydrocracked oil is dewaxed, either by solvent dewaxing or by catalytic dewaxing, with catalytic dewaxing typically being the preferred method. The dewaxed oil is then preferably hydrofinished at mild temperatures (150-300° C.) to remove polynuclear aromatics (PNAs) which were not converted in the first stage and the dewaxing stage and which have a strongly detrimental impact on lube base oil quality.
Group III base oils have the same sulfur and aromatics specifications as Group II base stocks but have viscosity indices above 120. These materials are manufactured with the same type of catalytic technology employed to produce Group II base oils but with either the hydrocracker being operated at higher severity, or with the use of feedstocks with higher wax content.
A typical lube hydroprocessing plant consists of two primary processing stages. In the lead stage, a feedstock, typically a vacuum gas oil, deasphalted oil, processed gas oils, or any combination of these materials, is hydrocracked. In a second stage, the hydrocracked oil is dearomatized, preferably with an aromatic saturation catalyst, and dewaxed, preferably with the use of a highly shape-selective catalyst capable of wax conversion by isomerization. The dewaxed, dearomatized oil can be subsequently hydrofinished to remove PNA impurities. Operation of the final hydrofinishing step is optimized to convert PNA impurities since significant conversion of one ring and two ring aromatics cannot be accomplished in the final hydrofinishing step because of its low operating temperature.
It is desirable to continue to improve the process of producing base oils, particularly Group III base oils with the more stringent specifications, by minimizing the required processing stages and separations required.
The claimed invention provides a process of producing Group III base oils, along with a naphtha product and diesel product, from whole waxy crude oil without the typical vacuum distillation stage and separations to form the typical cuts off of the vacuum tower. By selecting a waxy crude oil suitable for processing without separations, the crude oil may be hydroprocessed, dearomatized, dewaxed, and hydrofinished to produce a Group III base oil. Additionally, the dewaxing catalyst will isomerize the naphtha range molecules to increase the octane value to a suitable level for blending into gasoline and the diesel range molecules to reduce the diesel cloud point.
In one embodiment, a method for producing lubricant base oils from a whole petroleum crude oil is provided. A whole petroleum crude oil feedstock comprising less than about 2 wt % of heptane asphaltenes, less than about 2 wt % of Conradson carbon residue (CCR), and less than about 50 ppm of metals is hydrotreated over at least one bed of a hydrotreating catalyst under effective hydrotreating conditions to produce a hydrotreated effluent having less sulfur, nitrogen and aromatics than the whole petroleum crude oil. The hydrotreated effluent is then dewaxed in the presence of a dewaxing catalyst to produce a naphtha product having an octane value greater than 60, a diesel product having a cloud point less than 0° C., and a lubricant base oil product, which is fractionated into at least a low viscosity lubricant base oil product having a viscosity of 2-8 cSt at 100° C. and a high viscosity lubricant base oil product having a viscosity of 6-30 cSt at 100° C.
In another embodiment, a naphtha product, a diesel product, and a lubricant base oil product is produced from a whole petroleum crude oil. A whole petroleum crude oil feedstock, containing less than about 2 wt % of heptane asphaltenes, less than about 2 wt % of Conradson carbon residue (CCR), and less than about 50 ppm of metals, is provided, without separation or pretreatment, to a hydrotreating unit, where it is hydrotreated over at least one bed of a hydrotreating catalyst under effective hydrotreating conditions to produce a hydrotreated effluent having less than 15 ppm sulfur, less than 5 ppm nitrogen, less than 2 wt % C3- paraffins, and less than 25 wt % of aromatics. The hydrotreated effluent is dewaxed in the presence of a dewaxing catalyst to produce a dewaxed effluent, which is separated into at least a naphtha product having an octane value greater than 60, a diesel product having a cloud point less than 0° C., and a base stock product. The base stock product is subjected to hydrofinishing and/or aromatic saturation to remove polynuclear aromatic compounds and produce a hydrofinished base stock, which is then fractionated into at least a low viscosity lubricant base oil product having a viscosity of 2-8 cSt at 100° C. and a high viscosity lubricant base oil product having a viscosity of 6-30 cSt at 100° C.
All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
In various embodiments, methods are provided for producing lubricant base oils from crude oil. In a typical lubricant base oil production process, crude oil is subjected to atmospheric distillation to obtain a distillate cut and an atmospheric residual cut. The atmospheric residual cut is then sent to vacuum distillation where at least volatile distillate, light neutral distillate, heavy neutral distillate, and vacuum residual cuts are obtained. Deasphalting is then performed on the vacuum residual cut to remove asphaltenes, and the deasphalted oil is then subjected, along with the light neutral and heavy neutral cuts, to solvent extraction to remove aromatics. The raffinate from solvent extraction may then be hydroprocessed and dewaxed to produce base oils. However, the present inventors have discovered a way to produce high quality lubricant base oils while omitting several steps of the typical process, specifically atmospheric distillation, vacuum distillation, deasphalting and solvent extraction.
Suitable feedstocks for the present invention include whole petroleum crude oils that are low in metals and heptane asphaltenes. These whole petroleum crude oils often contain a high volume of waxy hydrocarbons. Ideally, the feedstock will be suitable for processing without separation.
One way of defining a feedstock is based on the boiling range of the feed. One option for defining a boiling range is to use an initial boiling point for a feed and/or a final boiling point for a feed. Another option, which in some instances may provide a more representative description of a feed, is to characterize a feed based on the amount of the feed that boils at one or more temperatures. For example, a “T5” boiling point for a feed is defined as the temperature at which 5 wt % of the feed will boil off. Similarly, a “T50” boiling point is a temperature at 50 wt % of the feed will boil. The percentage of a feed that will boil at a given temperature can be determined by the method specified in ASTM D2887. Whole waxy crudes suitable for the claimed process include, for example, feeds with an initial boiling point of at least 70° F. (21° C.), or at least 100° F. (37° C.), or at least 125° F. (51° C.).
In some aspects, the content of heptane asphaltenes in the whole crude feedstock can be less than 2.0 wt %, or less than 1 wt %, or less than 0.5 wt %, or less than 0.25 wt %, based on the total weight of the feedstock. The content of heptane asphaltenes in the 1050° F.+(565° C.+) fraction of the feedstock is less than 5.0 wt %. The feedstock may have a metals content of less than 50 ppm, or less than 20 ppm, or less than 15 ppm, or less than 10 ppm, or less than 5 ppm, and a content of carbonaceous residue of less than 2.0 wt %, or less than 1.5 wt %, or less than 1.0 wt %, or less than 0.5 wt %, as measured by the micro carbon residue test defined in ASTM D4530.
The feedstock 102 is hydrotreated in a first stage of the reactor system by a hydroprocessing unit 110. Hydrotreatment is typically used to reduce the sulfur, nitrogen, and aromatic content of a feed. The catalysts used for hydrotreatment of the crude oil can include conventional hydroprocessing catalysts, such as those that comprise at least one Group VIII non-noble metal (Columns 8-10 of IUPAC periodic table), preferably Fe, Co, and/or Ni, such as Co and/or Ni; and at least one Group VI metal (Column 6 of IUPAC periodic table), preferably Mo and/or W. Such hydroprocessing catalysts optionally include transition metal sulfides that are impregnated or dispersed on a refractory support or carrier such as alumina and/or silica. The support or carrier itself typically has no significant/measurable catalytic activity. Substantially carrier- or support-free catalysts, commonly referred to as bulk catalysts, generally have higher volumetric activities than their supported counterparts.
The catalysts can either be in bulk form or in supported form. In addition to alumina and/or silica, other suitable support/carrier materials can include, but are not limited to, zeolites, titania, silica-titania, and titania-alumina. Suitable aluminas are porous aluminas such as gamma or eta having average pore sizes from 50 to 200 Å, or 75 to 150 Å; a surface area from 100 to 300 m2/g, or 150 to 250 m2/g; and a pore volume of from 0.25 to 1.0 cm3/g, or 0.35 to 0.8 cm3/g. More generally, any convenient size, shape, and/or pore size distribution for a catalyst suitable for hydrotreatment of a distillate (including lubricant base oil) boiling range feed in a conventional manner may be used. It is within the scope of the present disclosure that more than one type of hydroprocessing catalyst can be used in one or multiple reaction vessels.
The at least one Group VIII non-noble metal, in oxide form, can typically be present in an amount ranging from 2 wt % to 40 wt %, preferably from 4 wt % to 15 wt %. The at least one Group VI metal, in oxide form, can typically be present in an amount ranging from 2 wt % to 70 wt %, preferably for supported catalysts from 6 wt % to 40 wt % or from 10 wt % to 30 wt %. These weight percents are based on the total weight of the catalyst. Suitable metal catalysts include cobalt/molybdenum (1-10% Co as oxide, 10-40% Mo as oxide), nickel/molybdenum (1-10% Ni as oxide, 10-40% Co as oxide), or nickel/tungsten (1-10% Ni as oxide, 10-40% W as oxide) on alumina, silica, silica-alumina, or titania.
The hydrotreatment is carried out in the presence of hydrogen. A hydrogen stream is, therefore, fed or injected into a vessel or reaction zone or hydroprocessing zone in which the hydroprocessing catalyst is located. Hydrogen, which is contained in a hydrogen “treat gas,” is provided to the reaction zone. Treat gas, as referred to in this disclosure, can be either pure hydrogen or a hydrogen-containing gas, which is a gas stream containing hydrogen in an amount that is sufficient for the intended reaction(s), optionally including one or more other gasses (e.g., nitrogen and light hydrocarbons such as methane), and which will not adversely interfere with or affect either the reactions or the products. Impurities, such as H2S and NH3 are undesirable and would typically be removed from the treat gas before it is conducted to the reactor. The treat gas stream introduced into a reaction stage will preferably contain at least 50 vol. % and more preferably at least 75 vol % hydrogen.
Hydrogen can be supplied at a rate of from 100 SCF/B (standard cubic feet of hydrogen per barrel of feed) (17 Nm3/m3) to 1500 SCF/B (253 Nm3/m3). Preferably, the hydrogen is provided in a range of from 200 SCF/B (34 Nm3/m3) to 1200 SCF/B (202 Nm3/m3). Hydrogen can be supplied co-currently with the input feed to the hydrotreatment reactor and/or reaction zone or separately via a separate gas conduit to the hydrotreatment zone.
Hydrotreating conditions can include temperatures of 200° C. to 450° C., or 315° C. to 425° C., preferably 340° C. to 420° C.; pressures of 250 psig (1.8 MPag) to 5000 psig (34.6 MPag) or 300 psig (2.1 MPag) to 3000 psig (20.8 MPag), preferably 1500 psig (10.3 MPag) to 2500 psig (13.8 MPag), more preferably 1750 psig (12.1 MPag) to 2250 psig (13.1 MPag); liquid hourly space velocities (LHSV) of 0.1 hr−1 to 10 hr−1, preferably 0.1 hr−1 to 2 hr−1, more preferably 0.3 hr−1 to 0.7 hr−1; and hydrogen treat rates of 200 SCF/B (35.6 m3/m3) to 10,000 SCF/B (1781 m3/m3), or 500 (89 m3/m3) to 10,000 SCF/B (1781 m3/m3).
The hydrotreatment may be carried out in one or more catalyst beds. In one embodiment, the hydroprocessing unit 110 contains more than one hydrotreatment catalyst beds, in some embodiments, two catalyst beds, and in some embodiments, three catalyst beds. The hydrotreated effluent 112 contains less sulfur, nitrogen, and aromatics than the feedstock 102. In some embodiments, the hydrotreated effluent 112 will contain less than 15 ppm of sulfur, less than 5 ppm of nitrogen, less than 2 wt % of C3— paraffins, and less than 25 wt % of aromatics.
In addition to or as an alternative to exposing the petrolatum to a hydrotreating catalyst, the petrolatum can be exposed to one or more beds of hydrocracking catalyst. The hydrocracking conditions can be selected so that the total conversion from all hydrotreating and/or hydrocracking stages is 15 wt % or less, or 10 wt % or less, or 8 wt % or less, as described above.
Hydrocracking catalysts typically contain sulfided base metals on acidic supports, such as amorphous silica alumina, cracking zeolites such as USY, or acidified alumina. Often these acidic supports are mixed or bound with other metal oxides such as alumina, titania or silica. Non-limiting examples of metals for hydrocracking catalysts include nickel, nickel-cobalt-molybdenum, cobalt-molybdenum, nickel-tungsten, nickel-molybdenum, and/or nickel-molybdenum-tungsten. Additionally or alternately, hydrocracking catalysts with noble metals can also be used. Non-limiting examples of noble metal catalysts include those based on platinum and/or palladium. Support materials which may be used for both the noble and non-noble metal catalysts can comprise a refractory oxide material such as alumina, silica, alumina-silica, kieselguhr, diatomaceous earth, magnesia, zirconia, or combinations thereof, with alumina, silica, alumina-silica being the most common (and preferred, in one embodiment).
In various aspects, the conditions selected for hydrocracking can depend on the desired level of conversion, the level of contaminants in the input feed to the hydrocracking stage, and potentially other factors. A hydrocracking process can be carried out at temperatures of 550° F. (288° C.) to 840° F. (449° C.), hydrogen partial pressures of from 250 psig to 5000 psig (1.8 MPag to 34.6 MPag), liquid hourly space velocities of from 0.05 h−1 to 10−1, and hydrogen treat gas rates of from 35.6 m3/m3 to 1781 m3/m3 (200 SCF/B to 10,000 SCF/B). In other embodiments, the conditions can include temperatures in the range of 600° F. (343° C.) to 815° F. (435° C.), hydrogen partial pressures of from 500 psig to 3000 psig (3.5 MPag to 20.9 MPag), and hydrogen treat gas rates of from 213 m3/m3 to 1068 m3/m3 (1200 SCF/B to 6000 SCF/B). The LHSV relative to only the hydrocracking catalyst can be from 0.25 h−1 to 50 hr−1, such as from 0.5 hr−1 to 20 hr−1, and preferably from 1.0 hr−1 to 4.0 h−1.
In some aspects, a high pressure stripper (or another type of separator) can then be used in between the hydrotreatment stage 110 and catalytic dewaxing stage 120 of the reaction system to remove gas phase sulfur and nitrogen contaminants. A separator allows contaminant gases formed during hydrotreatment (such as H2S and NH3) to be removed from the reaction system prior to passing the hydrotreated effluent 112 into a later stage of the reaction system. One option for the separator is to simply perform a gas-liquid separation to remove contaminants. Another option is to use a separator such as a flash separator that can perform a separation at a higher temperature.
The hydrotreated effluent 112 is then processed over one or more catalyst beds containing a dewaxing catalyst in a catalytic dewaxing unit 120. Typically, the dewaxing catalyst is located in a bed downstream from any hydrotreatment catalyst stages and/or any hydrotreatment catalyst present in a stage. This can allow the dewaxing to occur on molecules that have already been hydrotreated to remove a significant fraction of organic sulfur- and nitrogen-containing species.
Suitable dewaxing catalysts can include molecular sieves such as crystalline aluminosilicates (zeolites). In an embodiment, the molecular sieve can comprise, consist essentially of, or be a molecular sieve having a structure with 10-member rings or smaller, such as ZSM-22, ZSM-23, ZSM-35 (or ferrierite), ZSM-48, or a combination thereof, for example ZSM-23 and/or ZSM-48, or ZSM-48 and/or zeolite Beta. Optionally but preferably, molecular sieves that are selective for dewaxing by isomerization as opposed to cracking can be used, such as ZSM-48, ZSM-23, or a combination thereof. Additionally or alternately, the molecular sieve can comprise, consist essentially of, or be a 10-member ring 1-D molecular sieve. Examples include EU-1, ZSM-35 (or ferrierite), ZSM-11, ZSM-57, NU-87, SAPO-11, ZSM-48, ZSM-23, and ZSM-22. Preferred materials are EU-2, EU-11, ZBM-30, ZSM-48, or ZSM-23. ZSM-48 is most preferred. Note that a zeolite having the ZSM-23 structure with a silica to alumina ratio of from 20:1 to 40:1 can sometimes be referred to as SSZ-32. Optionally but preferably, the dewaxing catalyst can include a binder for the molecular sieve, such as alumina, titania, silica, silica-alumina, zirconia, or a combination thereof, for example alumina and/or titania or silica and/or zirconia and/or titania.
Preferably, the dewaxing catalysts used in processes according to the disclosure are catalysts with a low ratio of silica to alumina. For example, for ZSM-48, the ratio of silica to alumina in the zeolite can be less than 200:1, such as less than 110:1, or less than 100:1, or less than 90:1, or less than 75:1. In various embodiments, the ratio of silica to alumina can be from 50:1 to 200:1, such as 60:1 to 160:1, or 70:1 to 100:1.
In various embodiments, the catalysts according to the disclosure further include a metal hydrogenation component. The metal hydrogenation component is typically a Group VI and/or a Group VIII metal. Preferably, the metal hydrogenation component is a Group VIII noble metal. Preferably, the metal hydrogenation component is Pt, Pd, or a mixture thereof. In an alternative preferred embodiment, the metal hydrogenation component can be a combination of a non-noble Group VIII metal with a Group VI metal. Suitable combinations can include Ni, Co, or Fe with Mo or W, preferably Ni with Mo or W.
The metal hydrogenation component may be added to the catalyst in any convenient manner. One technique for adding the metal hydrogenation component is by incipient wetness. For example, after combining a zeolite and a binder, the combined zeolite and binder can be extruded into catalyst particles. These catalyst particles can then be exposed to a solution containing a suitable metal precursor. Alternatively, metal can be added to the catalyst by ion exchange, where a metal precursor is added to a mixture of zeolite (or zeolite and binder) prior to extrusion.
The amount of metal in the catalyst can be at least 0.1 wt % based on catalyst, or at least 0.15 wt %, or at least 0.2 wt %, or at least 0.25 wt %, or at least 0.3 wt %, or at least 0.5 wt % based on catalyst. The amount of metal in the catalyst can be 20 wt % or less based on catalyst, or 10 wt % or less, or 5 wt % or less, or 2.5 wt % or less, or 1 wt % or less. For embodiments where the metal is Pt, Pd, another Group VIII noble metal, or a combination thereof, the amount of metal can be from 0.1 to 5 wt %, preferably from 0.1 to 2 wt %, or 0.25 to 1.8 wt %, or 0.4 to 1.5 wt %. For embodiments where the metal is a combination of a non-noble Group VIII metal with a Group VI metal, the combined amount of metal can be from 0.5 wt % to 20 wt %, or 1 wt % to 15 wt %, or 2.5 wt % to 10 wt %.
The dewaxing catalysts useful in processes according to the disclosure can also include a binder. In some embodiments, the dewaxing catalysts used in process according to the disclosure are formulated using a low surface area binder, where a low surface area binder represents a binder with a surface area of 100 m2/g or less, or 80 m2/g or less, or 70 m2/g or less. The amount of zeolite in a catalyst formulated using a binder can be from 30 wt % zeolite to 90 wt % zeolite relative to the combined weight of binder and zeolite. Preferably, the amount of zeolite is at least 50 wt % of the combined weight of zeolite and binder, such as at least 60 wt % or from 65 wt % to 80 wt %.
A zeolite can be combined with binder in any convenient manner. For example, a bound catalyst can be produced by starting with powders of both the zeolite and binder, combining and mulling the powders with added water to form a mixture, and then extruding the mixture to produce a bound catalyst of a desired size. Extrusion aids can also be used to modify the extrusion flow properties of the zeolite and binder mixture. The amount of framework alumina in the catalyst may range from 0.1 to 3.33 wt %, or 0.1 to 2.7 wt %, or 0.2 to 2 wt %, or 0.3 to 1 wt %.
Process conditions in a catalytic dewaxing zone can include a temperature of from 200 to 450° C., preferably 270 to 400° C., a hydrogen partial pressure of from 1.8 MPag to 34.6 MPag (250 psig to 5000 psig), preferably 4.8 MPag to 20.8 MPag, and a hydrogen circulation rate of from 35.6 m3/m3 (200 SCF/B) to 1781 m3/m3 (10,000 SCF/B), preferably 178 m3/m3 (1000 SCF/B) to 890.6 m3/m3 (5000 SCF/B). In still other embodiments, the conditions can include temperatures in the range of 600° F. (343° C.) to 815° F. (435° C.), hydrogen partial pressures of from 500 psig to 3000 psig (3.5 MPag-20.9 MPag), and hydrogen treat gas rates of from 213 m3/m3 to 1068 m3/m3 (1200 SCF/B to 6000 SCF/B). The liquid hourly space velocity (LHSV) can be from 0.2 hr−1 to 10 hr−1, such as from 0.5 hr−1 to 5 hr−1 and/or from 1 hr−1 to 4 hr−1.
The dewaxed effluent 122 is separated by distillation in column 130 into a naphtha product 132 having a boiling point range of less than about 350° F. (176° C.), a diesel product 134 having a boiling point range of about 350° F. (176° C.) to about 700° F. (371° C.), and a Group III lube base stock product 136 having a boiling point of greater than about 700° F. (371° C.). The naphtha product 132 has an octane value greater than 60, preferably greater than 65, more preferably greater than 70, and ideally greater than 75, allowing it to be directly blended into gasoline. The diesel product 134 has a T90 of between 650° F. (343° C.) and 700° F. (371° C.), a cloud point of less than 0° C., preferably less than −10° C., and more preferably less than −15° C., and qualifies as an ultra-low sulfur diesel product. The base stock product 136 is of Group III quality, having a viscosity index of more than 120, less than 300 ppm sulfur, and 10 wt % aromatics.
Hydrofinishing and/or Aromatic Saturation Process
In some aspects, the base stock product 136 is processed through a hydrofinishing and/or aromatic saturation stage 140. Hydrofinishing and/or aromatic saturation catalysts can include catalysts containing Group VI metals, Group VIII metals, and mixtures thereof. In an embodiment, preferred metals include at least one metal sulfide having a strong hydrogenation function. In another embodiment, the hydrofinishing catalyst can include a Group VIII noble metal, such as Pt, Pd, or a combination thereof. The mixture of metals may also be present as bulk metal catalysts wherein the amount of metal is 30 wt % or greater based on catalyst. Suitable metal oxide supports include low acidic oxides such as silica, alumina, silica-aluminas or titania, preferably alumina. The preferred hydrofinishing catalysts for aromatic saturation will comprise at least one metal having relatively strong hydrogenation function on a porous support. Typical support materials include amorphous or crystalline oxide materials such as alumina, silica, and silica-alumina. The support materials may also be modified, such as by halogenation, or in particular fluorination. The metal content of the catalyst is often as high as 20 weight percent for non-noble metals. In an embodiment, a preferred hydrofinishing catalyst can include a crystalline material belonging to the M41S class or family of catalysts. The M41S family of catalysts are mesoporous materials having high silica content. Examples include MCM-41, MCM-48 and MCM-50. A preferred member of this class is MCM-41. If separate catalysts are used for aromatic saturation and hydrofinishing, an aromatic saturation catalyst can be selected based on activity and/or selectivity for aromatic saturation, while a hydrofinishing catalyst can be selected based on activity for improving product specifications, such as product color and polynuclear aromatic reduction.
Hydrofinishing conditions can include temperatures from 125° C. to 425° C., preferably 180° C. to 280° C., a hydrogen partial pressure from 500 psig (3.4 MPa) to 3000 psig (20.7 MPa), preferably 1500 psig (10.3 MPa) to 2500 psig (17.2 MPa), and liquid hourly space velocity from 0.1 hr−1 to 5 hr−1 LHSV, preferably 0.5 hr−1 to 1.5 hr−1. Additionally, a hydrogen treat gas rate of from 35.6 m3/m3 to 1781 m3/m3 (200 SCF/B to 10,000 SCF/B) can be used.
The hydrofinished base stock 142 is then stripped to remove light hydrocarbons and separated in column 150 into two fractions—a light neutral base stock 152 having a low viscosity of 2-8 cSt (at 100° C.), preferably 3-5 cSt (at 100° C.), and a heavy neutral base stock 154 having a high viscosity of 6-30 cSt (at 100° C.), preferably 8-15 cSt (at 100° C.). Both Group III base stock fractions have a viscosity index of greater than 120 and pour point of −15° C. and the cloud point-pour point spread is less than 30° C.
The inventive process provides several advantages over the typical base oil production process. Whole petroleum crude with a high concentration of waxy hydrocarbons can be efficiently upgraded to finished products without the difficulties waxy hydrocarbons generally present in processing. Because the waxy hydrocarbons are never concentrated, the need for heated tanks and transport lines in the process is eliminated. The finished products can be obtained in essentially two stages—hydroprocessing and catalytic dewaxing. In the two stages, the 350° F.−(176° C.−) molecules are upgraded by octane enhancement to a product high enough in octane to directly blend into gasoline. The 350° F.−650° F. (176-343° C.) distillate molecules are dewaxed, desulfurized, and hydrogenated into ultra-low sulfur diesel, and the 650° F.+(343° C.+) molecules are hydroisomerized and hydrogenated into Group III base stock. Further, the process minimizes distillation as no molecules are vaporized more than once and the high viscosity Group III base stock product is produced without vaporization.
The ability to simultaneously produce fuels and lubricants from a whole waxy crude oil without significantly over- or under-converting some fraction of the feedstock is surprising. The yield and selectivity benefits from processing whole waxy crude oil versus separately processing naphtha, distillate, and 650° F.+(343° C.+) fractions is also surprising. Without being bound by theory, it is believed that the stability and selectivity of the dewaxing catalyst described herein enables such conversion and achieves a sufficiently flat pour point versus boiling point profile to simultaneously upgrade naphtha range and 1050° F.+(565° C.+) paraffins. Also, use of the described dewaxing catalyst allows simultaneous production of low and high viscosity base stocks that meet or exceed Group III base stock specifications. Additionally, the 650° F.−(343° C.−) components of the feedstock reduce mass transport limitations in the dewaxing catalyst and keep the yield of C3— paraffin molecules to less than 2 wt %. Less than 25 wt %, preferably less than 20 wt %, more preferably less than 15 wt %, and ideally 10 wt % of the 650° F.+ lubricant range molecules are converted into 650° F.−(343° C.−) fuel range molecules.
Whole waxy crude oil having the properties listed below in Table 1 is provided. The octane value of the 350° F.−(176° C.−) fraction of the whole waxy crude oil is 40 and the cloud point of the 350-650° F. (176-343° C.) distillate fraction is 25° C.
The waxy crude oil is processed over a stacked bed of three commercially available nickel-molybdenum sulfided hydroprocessing catalysts at about 1800 psig, about 0.4 hr−1 LHSV, and about 340° C. start of cycle temperature. The yield of 650° F.+(343° C.+) product is about 28 wt %. The total liquid product has a sulfur content of <1 ppm and a nitrogen content of <1 ppm. The hydroprocessed effluent is subjected to dewaxing over an alumina-bound ZSM-48 having a silica to alumina ratio of about 70:1 with 0.6 wt % of platinum at about 0.675 LHSV, about 340° C., and 1800 psig. The dewaxed effluent is distilled to produce a 1 wt % yield of C3— paraffins, 44 wt % C4−350° F.+(176° C.+) gasoline with 73 octane, 30 wt % yield of ULSD with a cetane of 60 and a cloud point of −20° C., and a 25% yield of 650° F.+(343° C.+) base stocks.
The 650° F.+(343° C.+) base stocks is processed over an alumina bound MCM-41 catalyst with 0.3 wt % of palladium and 0.9 wt % of platinum at about 1.0 hr−1 LHSV, about 220° C., and 1800 psig, which produces negligible 650° F.−(343° C.−) products. The hydrofinished 650° F.+(343° C.+) base stocks is distilled into two fractions—66 wt % of a 4 cSt (at 100° C.) light neutral Group III base stock with a viscosity index of 122 and a pour point of −40° F., and 34 wt % of a 8 cSt (at 100° C.) heavy neutral Group III base stock with a viscosity index of 128 and a pour point of −20° F.
The inventive process yields 25 wt % of 650° F.+(343° C.+) Group III base stock product—meaning 83% of the 650° F.+(343° C.+) molecules from the crude oil feedstock are retained. More than half of the 17% conversion of the 650° F.+(343° C.+) molecules to 650° F.−(343° C.−) molecules is caused by the boiling point lowering effect of paraffin isomerization (n-C20 molecules converting to tri-methyl C17 molecules) and aromatics saturation (naphthalenes with a C6 to C8 side-chain hydrogenating to decalins with no change in side-chain structure). There is a large improvement in the octane value of the 350° F.−(176° C.−) fraction, from an initial octane value of the feedstock of 40, making it unsuitable for blending into gasoline, to 73 in the product, which is suitable for blending into gasoline without further processing. The 350° F.−(176° C.−) fraction (naphtha) is also sulfur free. The 350° F.−650° F. (176-343° C.) distillate fraction is upgraded by reducing the pour point from +15° C. to −30° C. and the sulfur content from 100 ppm to less than 1 ppm, producing a premium quality ultra-low sulfur diesel blendstock.
All patents, test procedures, and other documents cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent and for all jurisdictions in which such incorporation is permitted.
While the illustrative forms disclosed herein have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the example and descriptions set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty which reside herein, including all features which would be treated as equivalents thereof by those skilled in the art to which this disclosure pertains.
When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.
This application claims the benefit of U.S. Provisional Application No. 62/516,312, filed on Jun. 7, 2017, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62516312 | Jun 2017 | US |
