JP5042622B2 - Fischer-Tropsch Premium Diesel and Method for Producing Lubricating Base Oil - Google Patents

Abstract

A process for producing a premium Fischer-Tropsch diesel fuel which comprises (a) hydroprocessing a waxy Fischer-Tropsch feed to remove the oxygenates that are present in the feed, whereby a first Fischer-Tropsch intermediate product is produced with reduced olefins and oxygenates relative to the Fischer-Tropsch feed; (b) separating the first Fischer-Tropsch intermediate product in a separation zone into a heavy Fischer-Tropsch fraction and a light Fischer-Tropsch fraction under controlled separation conditions; (c) hydroisomerizing the heavy Fischer-Tropsch fraction to improve the cold flow properties of the heavy Fischer-Tropsch fraction and recovering an isomerized heavy Fischer-Tropsch fraction; (d) mixing the isomerized heavy Fischer-Tropsch fraction with at least a portion of the light Fischer-Tropsch fraction of (b); and (e) recovering from the blend a Fischer-Tropsch derived diesel product meeting a target value for at least one pre-selected specification for diesel fuel.

Description

  The present invention relates to a Fischer-Tropsch derivatized diesel fraction and a heavier isomerized Fischer-Tropsch derivatized base oil to meet at least one preselected target property for the diesel product. It relates to the production of Fischer-Tropsch derivatized premium diesel products produced by blending with fractions.

Transportation fuel intended for use in diesel engines must meet at least one of the current editions of the following standards:
ASTM D975- "Standard Specification for Diesel Fuel Oils"
European Grade CEN 90
Japanese fuel standard JIS K2204
US National Conference on Weights and Processing 1997 Guidelines for Premium Diesel Fuels [The United States National Conferences on Weights and Measurements (NCWM) 1997 guidelines for premier diesel fuel]
The United States Engine Manufacturers Association Recommended Guidelines for Premium Diesel Fuel (FQP-1A)

  These standards set a numerical value for the minimum technical requirements for diesel, so below that value, diesel fuel establishes a minimum quality value that is considered technically unfit for its purpose. Yes.

  Fischer-Tropsch derivatized transport fuels that meet the standards for diesel fuels have certain advantageous properties that make it possible to produce premium diesel fuels with very low sulfur content and excellent cetane numbers. However, due to the unique characteristics of Fischer-Tropsch derivatized synthetic crude oil, additional processing operations must be performed to produce a suitable diesel fuel. Since Fischer-Tropsch derivatized products generally contain a significant proportion of olefins, hydrotreating such as mild hydrotreating to saturate double bonds is required to improve oxidative stability. Operation is usually necessary. Also, the isoparaffin content must usually be increased by a dewaxing step in order to improve the cold flow characteristics of the fuel. Unfortunately, transportation fuels are characterized by high capacity, and the dewaxing step makes Fischer-Tropsch derivatized diesel fuel uncompetitive with conventional petroleum derivatized diesel fuel.

  Premium lube base oils can also be produced from Fischer-Tropsch derivatized hydrocarbons, but the product contains a high percentage of linear paraffins, so a dewaxing step is also required to improve cold flow properties before sale And However, lubricating base oils are generally produced in smaller amounts than transportation fuels and have a higher commercial value, so dewaxing operations are not commercially impractical.

  The present invention relates to an integrated process that can be combined with a Fischer-Tropsch derivatized premium lubricating base oil to produce a Fischer-Tropsch derivatized premium diesel fuel. In the process of the present invention, the properties of the base oil fraction recovered from the synthetic crude oil are returned to a product that can be blended into the diesel fraction after further processing to produce a diesel fuel having the desired properties. Carefully controlled to produce. The process of the present invention is advantageous because it is possible to produce premium diesel fuel without hydroisomerizing the entire diesel product. This reduction in feedstock represents a significant savings in capital costs due to the smaller vessel size required for the isomerization reactor. By significantly reducing the cost of processing Fischer-Tropsch derivatized diesel fuel, it is possible to produce premium products that are cost competitive with conventional petroleum derivatized diesel fuel.

  Fischer-Tropsch synthetic crude oil fractions that are processed into diesel fuel are typically about 150 ° F. (about 65 ° C.) to about 750 ° F. (about 400 ° C.), typically about 400 ° F. (about 205 ° F.). ° C) to about 600 ° F. (about 315 ° C.). Many of the hydrocarbons boiling in the diesel range have from about 9 to about 19 carbon atoms in their molecules. Lubricating base oils are generally produced from a portion of a Fischer-Tropsch synthetic crude oil that boils above about 600 ° F. (about 315 ° C.) and has at least 20 carbon atoms in its molecule. However, the initial boiling point of the base oil fraction can be higher, for example, about 750 ° F. (about 400 ° C.). Those skilled in the art will recognize that there is considerable overlap between the higher boiling point of diesel and the initial boiling point of the base oil fraction. The exact cut point chosen will depend on the desired properties in the final product. By carefully controlling the separation point between the diesel and the base oil, it is possible to adjust the properties of the two products, thus returning a portion of the hydroisomerized base oil to the diesel. When blended, the diesel product meets the premium diesel fuel standards without the need to isomerize the entire diesel stream.

Also, the naphtha produced by the process of the present invention has a boiling range that is lower than the boiling range of diesel, but normally higher than that of gaseous hydrocarbons such as butane and propane. Thus, naphtha generally has a boiling range between ambient temperature and about 150 ° F. (about 65 ° C.), and molecules boiling in this range contain about 5 to about 8 carbon atoms. Have. Naphtha produced by this method usually has a low octane rating due to the highly paraffinic nature of Fischer-Tropsch material. As a result, naphtha produced by this method is generally not suitable for use as a transportation fuel without further processing. However, the naphtha produced can be used as a feed to the ethylene cracker without additional processing. Hydrocarbons having less than 5 carbon atoms in the molecule are usually gases at ambient temperature and are included in the overhead gas, optionally before or after recovering the LPG (C ₃ and C ₄ ) fraction. It can be recirculated upstream in the Fischer-Tropsch processor after.

  A process scheme similar to the process of the present invention has already been presented and is commercially implemented for conventional petroleum derivatized products. See, for example, US Pat. Nos. 5,976,354, 5,980,729, 6,337,010 B1, and 6,432,297 B1. However, none of these process schemes is intended for the treatment of Fischer-Tropsch derivatized materials and their purposes are very different. Also, in most of these process schemes, the main product of interest is the lubricating base oil fraction. In the present invention, the lubricating base oil can be one of the recovered products, but the main product of interest is the diesel fuel product. Thus, to ensure that the portion of the isomerized base oil fraction that is blended back into the diesel fraction produces a diesel product with the desired properties, the separation of the diesel fraction and the base oil fraction. The temperature conditions under which are performed are carefully controlled. Also, most of these methods relate to treating petroleum derivatized feedstocks, and hydroprocessing operations where feedstock is subjected to separation of diesel and base oil fractions typically include: Hydrotreating operation to remove sulfur and nitrogen (see US Pat. No. 5,976,354) or hydrocracking operation to reduce the average molecular weight of the feedstock (see US Pat. No. 6,337,010 B1) ) For different purposes. In the process of the present invention, the hydrotreating operation is primarily intended to saturate olefins and remove oxygenates.

  As used in this disclosure, the term “includes” or “includes” refers to the inclusion of the indicated element, but does not necessarily exclude other not shown elements, and as an unscoped transition. Intended. The expressions “consisting essentially of” or “consisting essentially of” are intended to mean the exclusion of elements other than those critical to the composition. The expression “consisting of” or “consisting of” is intended as a transition that means the exclusion of all but the indicated elements, except for only trace amounts of impurities.

  The present invention provides: (a) in the hydrotreating zone, in the presence of hydrotreating catalyst in the presence of a hydrotreating catalyst intended to saturate olefins and remove oxygenates present in the feedstock. A first Fischer-Tropsch intermediate product that processes waxy Fischer-Tropsch feedstock recovered from Tropsch synthesis, thereby having reduced olefins and oxygenates compared to the Fischer-Tropsch feedstock (B) characterized by the boiling end point where the Fischer-Tropsch light fraction falls within the boiling range of diesel in the separation zone, and the Fischer-Tropsch heavy fraction is the boiling point of the Fischer-Tropsch light fraction. Under controlled separation conditions characterized by a boiling range higher than the first range, Separating the Tropsch intermediate product into a Fischer-Tropsch heavy fraction and a Fischer-Tropsch light fraction, (c) To improve the cold flow characteristics of the Fischer-Tropsch heavy fraction in the hydroisomerization zone Contacting a Fischer-Tropsch heavy fraction with a hydroisomerization catalyst under selected hydroisomerization conditions and recovering the isomerized Fischer-Tropsch heavy fraction, (d) Mixing a Fischer-Tropsch heavy fraction with at least a portion of the Fischer-Tropsch light fraction of step (b) and (e) at least one preselected specification value for diesel fuel from the blend Recovering a Fischer-Tropsch derivatized diesel product that meets the target value for It relates to a method for generating an Interview premium diesel fuel.

  Fischer-Tropsch heavy fractions generally have an initial boiling point within the low end of the lubricating base oil boiling range and the high end of the diesel boiling range. That is, the initial boiling point is typically about 550 ° F. (about 285 ° C.) to about 750 ° F. (about 400 ° C.). However, in order to meet the target value for the selected standard or standards for diesel products, under certain circumstances, it is lower than 600 ° F and perhaps as low as 450 ° F (about 230 ° C). Furthermore, it is desirable to produce more heavy fractions by lowering the initial boiling point of the heavy fraction. In that case, the amount of heavy fraction that is isomerized and blended back into diesel is significantly increased.

The hydroprocessing conditions in the first stage of the process used to saturate the olefin and remove oxygenates present in the Fischer-Tropsch feed are preferably mild and usually minimize molecular degradation. Chosen to do. However, by changing the conversion rate of the hydrotreating operation, the amount of diesel or lubricating base oil can be maximized. For example, by operating at higher conversion rates, typically higher than about 20% conversion, the amount of diesel produced by the process can be increased and C ₂₀ plus molecules present in the feedstock. Part of it will be broken down into products within the boiling range of the transportation fuel. Similarly, by minimizing the amount of conversion at this stage, typically less than 20%, the amount of base oil produced will be maximized due to the very low cracking rate.

  As used in this disclosure, the “conversion” of a hydrocarbon feedstock is the first higher than a predetermined reference temperature after conversion of the Fischer-Tropsch feed to a product boiling at a temperature below the predetermined reference temperature. Refers to the percent of hydrocarbons recovered from the hydroprocessing zone having a boiling point. See U.S. Patent No. 6,224,747. For the purposes of this disclosure, the reference temperature chosen is typically about 650 ° F. (340 ° C.).

  A portion of the produced isomerized Fischer-Tropsch heavy fraction is blended back to diesel to meet target values for one or more preselected standards for diesel. . One skilled in the art will recognize that the standard or standards chosen will depend on the nature of the operation and the market in which the diesel product is sold.

  In general, the selected diesel standard or specifications include one or more of a cold filter plugging point, cloud point, or pour point. Each of these standards can be easily controlled in the diesel product by blending back a portion of the isomerized Fischer-Tropsch heavy fraction.

  In most embodiments of the present invention, the separation zone comprises at least two separation zones described herein as a first separation zone and a second separation zone. To separate the Fischer-Tropsch heavy fraction from naphtha, diesel and gaseous hydrogen rich fractions, in most embodiments, a first separation zone containing a high temperature and high pressure separator is used, usually the temperature of the hydroprocessing zone. It is operated at temperatures lower than about 50 ° F. (about 28 ° C.). In most embodiments, a second separation zone containing a low temperature and high pressure separator is used to separate the overhead gas from the remaining hydrocarbon boiling in the range of the transport fuel. The separation of the Fischer-Tropsch heavy and light fractions is isomerized with the heavy fractions that are boiled back as part of the final diesel product, with much of the hydrocarbon boiling in the diesel range. Therefore, the operation of the separation zone is critical for the present invention.

  In order to facilitate separation in the high-pressure separator, it is preferable to use a stripping gas. In a high temperature and high pressure separator, for example, a stripping gas such as steam or hydrogen can be used. In general, hydrogen is preferred as the stripping gas in this scheme.

  The invention can be more clearly understood by referring to the drawings that represent one embodiment of a process scheme. In this figure, the Fischer-Tropsch condensate feed 2 and the Fischer-Tropsch waxy feed 4 before entering the hydroprocessing reactor 6 by a common conduit 8 are shown separately, Fischer-Tropsch condensate feed 2 and Fischer-Tropsch waxy feed 4 are mixed with hydrogen from line 11, this hydrogen being recombined by compositional hydrogen entering via lines 9 and 10 and from line 28. Supplied by circulating hydrogen. In the hydrotreating reactor 6, the olefins present in the feedstock are saturated and the oxygenates consisting primarily of alcohol are removed.

In the present disclosure, the effluent from the hydrotreating reactor described as the first Fischer-Tropsch intermediate is conveyed by line 12 to the first separation zone 14 having a high temperature and high pressure separator. In the Fischer-Tropsch heavy fraction, which mainly contains waxy substances boiling in the base oil range, but also contains at least some hydrocarbons boiling in the diesel range, hydrogen and C ₄ minus hydrocarbons As with the overhead gas containing, the Fischer-Tropsch fraction boiling at lower temperatures, including hydrocarbons boiling in both naphtha and diesel ranges. The high temperature high pressure separator is typically operated at a temperature that is at least 50 ° F. (28 ° C.) lower than the operating temperature of the hydroprocessing reactor 6. Fischer-Tropsch heavy fraction is collected in conduit 16 and conveyed to hydroisomerization unit 18. Hydrogen for the isomerization stage is added from composition hydrogen via lines 9 and 19. Returning to the high temperature high pressure separator 14, lower boiling hydrocarbons and overhead gas are recovered by conduit 20 and carried to a second separation zone having a low temperature high pressure separator 22. In a low-temperature high-pressure separator, the hydrogen-rich overhead gas is separated from hydrocarbons boiling in the range of transport fuel. In order to remove hydrogen sulfide or ammonia present before being sent via line 28 to recirculated gas compressor 30 which is returned to hydrotreating reactor 6 via line 11 and recirculated, It is transferred to an optional recirculating gas scrubber 26 by line 24. Hydrocarbons containing hydrocarbons boiling primarily in the naphtha and diesel range are recovered from the low temperature high pressure separator by line 32 and sent to low pressure separator 34.

  Returning to the hydroisomerization unit 18, in order to increase the isoparaffin content of the Fischer-Tropsch heavy fraction and to improve its cold flow properties such as cold filter clogging point, pour point and VI and cloud point, Fischer-Tropsch heavy fractions containing most of the Fischer-Tropsch wax are isomerized. The isomerized Fischer-Tropsch heavy fraction is collected in line 36 and sent to a hydrogen finishing reactor 38 where oxidation stability is further improved. The isomerized and hydrogen-finished heavy fraction is conveyed to high pressure separator 42 where the hydrogen-rich overhead gas is recovered via line 40, recovered via line 44, and recycled to the hydrogen treatment unit. To the low temperature and high pressure separator 22. The effluent from the low-temperature high-pressure separator containing the heavy fraction is separated by a line 46 through the low-pressure separation where the isomerized and hydrogen-finished heavy fraction is mixed with the light fraction sent from the low-temperature high-pressure separator 22. Carried to machine 34.

The overhead gas containing mainly C ₄ minus hydrocarbons is recovered from the top of the low pressure separator via line 47 and carried to the top of product stripper 48. A mixture of Fischer-Tropsch heavy and light fractions is recovered in line 49 from the bottom of the low pressure separator and additional C ₄ minus hydrocarbons are separated from C ₅ plus hydrocarbons in product stripper 48. Sent to the lower part. The C ₄ minus hydrocarbon is recovered from the stripper by conduit 50. Product stream containing C ₅ plus hydrocarbons is recovered in conduit 52, naphtha 56 and diesel 58, the C ₄ atmospheric distillation unit 54 from minus hydrocarbons are recovered separately remaining in the conduit 60 Sent. A vacuum distillation unit in which a heavy residual liquid fraction is recovered and a light base oil fraction 66, an intermediate base oil fraction 68, and a heavy base oil fraction 70 are separately recovered via line 62 Sent to device 64.

  By controlling the operation of the high temperature and high pressure separator 14, non-waxy molecules are removed from the feed and sent to the hydroisomerization unit 18 to prevent contact with the isomerization catalyst. Thus, the Fischer-Tropsch light fraction, which contains most of the diesel and substantially all of the naphtha fraction, avoids isomerization operations and handles smaller volumes of hydrocarbons than otherwise, so the isomerization stage Making it much more efficient. Only the fraction containing the majority of Fischer-Tropsch wax enters the hydroisomerization zone. This separation stage is also used to meet standards for diesel fuel produced by an integrated process.

  By blending a portion of the isomerized, hydrofinished Fischer-Tropsch heavy fraction with diesel, the overall low temperature flow characteristics of the diesel product without the need to hydroisomerize and hydrofinish the entire diesel product. And the cloud point is improved. Most of the heavy fraction recovered with the diesel product from atmospheric distillation column 54 is a lighter base oil fraction, ie, a base oil fraction having a higher boiling point lower than 750 ° F. (400 ° C.). Contains minutes. Thus, by controlling the cut point in the high temperature and high pressure separator and fractionation operation, the amount of isomerized and hydrogen finished base oil blended into the diesel product can be controlled. Also, the operation of the hydroisomerization unit can also be controlled to optimize the conversion of heavy fractions that contribute to the properties of the final diesel product recovered from that operation.

  As already described, the operation of the hydroprocessing unit shown in the figure as hydroprocessing unit 6 can be varied to boil more hydrocarbons in the range of transport fuel. By operating under more severe conditions to increase conversion, larger molecules are decomposed and more diesel product is produced.

As an integrated process, the method of the present invention also allows for efficient recycling of the hydrogen rich C ₄ minus overhead gas to the hydrotreating zone, catalytic dewaxing zone and hydrogen finishing zone. Operating hydroprocessing reactors, catalytic dewaxing reactors and hydrofinishing reactors at substantially the same pressure reduces capital costs by eliminating the need for additional pumps and compressors. So it is generally advantageous. However, hydroisomerization generally has an optimum reaction pressure that is lower than the optimum reaction pressure in hydrocracking, hydrotreating and hydrogen finishing. Thus, under certain circumstances, it may be advantageous to operate the catalyst dewaxing unit at a pressure lower than that of the hydroprocessing unit and the hydrogen finishing unit. See, for example, US Pat. No. 6,337,010 B1.

Fischer-Tropsch synthesis In Fischer-Tropsch synthesis, liquid and gaseous hydrocarbons are obtained by contacting a synthesis gas containing a mixture of hydrogen and carbon monoxide with a Fischer-Tropsch catalyst under suitable temperature and pressure reactive conditions. Is generated. The Fischer-Tropsch reaction is typically about 300 ° F to about 700 ° F (about 150 ° C to about 370 ° C), preferably about 400 ° F to about 550 ° F (about 205 ° C to about 230 ° C). ) Temperature, about 10 psia to about 600 psia (0.7 bar to 41 bar), preferably 30 psia to 300 psia (2 bar to 21 bar) and about 100 cc / g / hour to about 10,000 cc / g / hour. Preferably, it is carried out at a catalyst space velocity of 300 cc / g / hour to 3,000 cc / g / hour.

The product can largely range from C ₁ to C ₂₀₀ plus hydrocarbons, C ₅ -C ₁₀₀ plus by weight. The reaction can be carried out in various reactor types, for example, a fixed bed reactor having one or more catalyst beds, a slurry reactor, a fluidized bed reactor or a combination of different types of reactors. Such reaction processes and reactors are well known and described in the literature. The Fischer-Tropsch slurry process, which is a preferred method for producing the feedstock used to practice the present invention, utilizes the excellent heat (and mass) transfer characteristics for highly exothermic synthesis reactions, and cobalt When a catalyst is used, a relatively high molecular weight paraffinic hydrocarbon can be produced. In the slurry process, in the reactor, in a slurry containing a granular Fischer-Tropsch type hydrocarbon synthesis catalyst dispersed and suspended in a slurry liquid containing a hydrocarbon product of a synthesis reaction that is liquid at the reaction conditions. Then, as a third phase, a synthesis gas containing a mixture of hydrogen and carbon monoxide is blown. The molar ratio of hydrogen to carbon monoxide can range widely from about 0.5 to about 4, but more typically within the range of about 0.7 to about 2.75, preferably about 0. Within the range of .7 to about 2.5. A particularly preferred Fischer-Tropsch process is taught in EP 0609079 and is fully incorporated herein by reference for all purposes.

Suitable Fischer-Tropsch catalysts include one or more Group VIII catalytic metals such as Fe, Ni, Co, Ru and Re, with cobalt generally being one preferred embodiment. A suitable catalyst may also contain a promoter. Thus, in one embodiment, the Fischer-Tropsch catalyst comprises cobalt and Re, Ru, Pt, Fe on a suitable inorganic support material, preferably one containing one or more refractory metal oxides. , Ni, Th, Zr, Hf, U, Mg and La contain an effective amount. Generally, the amount of cobalt present in the catalyst is about 1 to about 50% by weight of the total catalyst composition. The catalyst _{also, ThO 2, La 2 O 3} , MgO, basic oxide promoters such as _{K 2} O and TiO _2, promoters such as ZrO _2, noble metals (Pt, Pd, Ru, Rh , Os Ir), coin cast metals (Cu, Ag, Au) and other transition metals such as Fe, Mn, Ni and Re. Suitable support materials include alumina, silica, magnesia and titania or mixtures thereof. Preferred supports for cobalt-containing catalysts include alumina or titania. Useful catalysts and their preparation are known and are described in US Pat. No. 4,568,663, but the description is illustrative and not limiting regarding catalyst selection.

Usually, the product from the Fischer-Tropsch process is composed of a waxy fraction containing the majority of Fischer-Tropsch wax, a condensate fraction containing hydrocarbons boiling in the range of transportation fuel, and unreacted hydrogen and It is separately recovered as a gas fraction containing carbon oxide and C ₄ minus hydrocarbons. The waxy fraction represents the fraction that is normally solid at ambient temperature and constitutes the majority of the material to be isomerized in the present process. The condensate fraction contains most of the boiling hydrocarbons in the naphtha and diesel range, as well as oxygenates that are mostly in the form of alcohol that must be removed before further processing. . All of these fractions contain a significant amount of olefin that must be saturated in the hydroprocessing stage.

Hydrotreating in the present invention is primarily a stage intended for the purpose of removing residual nitrogen, saturating olefins, and removing oxygenates that may be present in the Fischer-Tropsch feed. Say. By increasing the severity of the hydroprocessing stage, the amount of diesel recovered in the final expected product can be increased. For the purposes of this disclosure, the term hydroprocessing is intended to refer to either hydroprocessing or hydrocracking. Hydroisomerization and hydrogen finishing are one type of hydroprocessing, but are treated separately because of their different functions in the process scheme.

  When hydroprocessing is used to process conventional petroleum derived feedstocks, the main objectives are various metal contaminants such as arsenic; heteroatoms such as sulfur and nitrogen; and aromas from the feedstock. Refers to the catalytic process normally performed in the presence of free hydrogen, which is the removal of a group compound. In the present process, the main purpose is to saturate the olefin and remove oxygenates in the feed before the catalytic dewaxing operation. In general, in hydroprocessing operations, the decomposition of hydrocarbon molecules, i.e., breaking of larger hydrocarbon molecules into smaller hydrocarbon molecules is minimized. For the purposes of this disclosure, the term hydrotreating refers to a hydrotreating operation with a conversion of 20% or less.

  Hydrocracking refers to a catalytic process that usually takes place in the presence of free hydrogen, for which the main purpose of this operation is the cracking of larger hydrocarbon molecules. For the purposes of this disclosure, the conversion of hydrocracking is greater than 20% as opposed to hydroprocessing. Hydrogenation of olefins and removal of oxygenates are performed as well as denitrogenation of the feedstock. In the present invention, the decomposition of hydrocarbon molecules is desirable to increase the yield of diesel and minimize the amount of Fischer-Tropsch heavy fraction that undergoes a catalytic dewaxing operation.

  Catalysts used to carry out hydroprocessing and hydrocracking are well known in the art. See, for example, U.S. Pat. Nos. 4,347,121 and 4,810,357. The contents of which are hereby fully incorporated by reference for a general description of typical catalysts used in hydroprocessing, hydrocracking and each of those processes. Suitable catalysts include noble metals of group VIIIA (according to International Union of Pure and Applied Chemistry 1975 rules) such as platinum or palladium on alumina or siliceous matrices, and nickel-molybdenum or nickel- on alumina or siliceous matrices. Non-sulfurized Group VIIIA and VIB metals such as tin are included. U.S. Pat. No. 3,852,207 describes suitable noble metal catalysts and mild conditions. Other suitable catalysts are described, for example, in US Pat. Nos. 4,157,294 and 3,904,513. Usually, the non-noble metal hydride such as nickel-molybdenum is used as an oxide, more preferably as a sulfide, or more preferably as a sulfide if it is easily generated from a specific metal contained in such a compound. Present in the composition. Preferred non-noble metal catalyst compositions are greater than about 5 wt.%, Preferably about 5 to about 40 wt.% Molybdenum and / or tungsten, and at least about 0.5 wt. About 1 to about 15% by weight of nickel and / or cobalt. Catalysts containing noble metals such as platinum contain more than 0.01%, preferably 0.1 to 1.0% metals. Combinations of precious metals such as a mixture of platinum and palladium can also be used.

  The hydrogenation component can be incorporated into the overall catalyst composition by any one of a number of operations. The hydrogenation component can be added to the matrix component by co-mixing, impregnation or ion exchange, and the Group VI components, ie, molybdenum and tungsten, can be combined with the refractory oxide by impregnation, co-mixing or co-precipitation. These components can be combined with the catalyst matrix as sulfides, which is generally undesirable because sulfur compounds interfere with the Fischer-Tropsch catalyst.

  The matrix component can be many types of materials including those having acidic catalytic activity. The active component includes amorphous silica-alumina or can be a zeolite or non-zeolite crystalline molecular sieve. Examples of suitable matrix molecular sieves include zeolite Y, zeolite X and so-called ultrastable zeolite Y and those described in US Pat. Nos. 4,401,556, 4,820,402 and 5,059,567. Such high structure silica: alumina ratio zeolite Y is included. Small crystal size zeolite Y such as that described in US Pat. No. 5,073,530 may also be used.

  Non-zeolitic molecular sieves that can be used are described, for example, in silicoaluminophosphate (SAPO), ferroaluminophosphate, titanium aluminophosphate and US Pat. No. 4,913,799 and references cited therein. Various ELAPO molecular sieves are included. Details regarding the preparation of various non-zeolitic molecular sieves can be found in US Pat. Nos. 5,114,563 (SAPO) and 4,913,799 and various references cited in US Pat. No. 4,913,799. Found. Mesoporous molecular sieves such as J.I. Am. Chem. Soc. 114: 10834-10843 (1992), M41S family materials, MCM-41; US Pat. Nos. 5,246,689; 5,198,203; and 5,334,368; MCM-48 [Nature 359: 710 (1992) by Kresge et al.] Can also be used. Suitable matrix materials also include synthetic or natural materials and metal oxides such as clay, silica and / or silica-alumina, silica-magnesia, silica-zirconia, silica-tria, silica-beryllia, silica-titania and Ternary compositions such as silica-alumina-tria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia can be included. The latter can be naturally occurring or can be in the form of a gelatinous precipitate or gel containing a mixture of silica and metal oxide. Naturally occurring clays that can be complexed with the catalyst include montmorillonite and kaolin series clays. These clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification.

  In performing hydrocracking and / or hydrotreating operations, more than one catalyst type can be used in the reactor. Different catalyst types can be separated into layers or mixed.

Hydrogenolysis conditions are well described in the literature. Generally, the total LHSV is from about 0.1 hour- ^{1 to} about 15.0 hour- ¹ (v / v), preferably from about 0.25 hour- ^{1 to} about 2.5 hour- ¹ . The reaction pressure is generally in the range of about 500 psig to about 3,500 psig (about 10.4 MPa to about 24.2 MPa), preferably about 1,500 psig to about 5,000 psig (about 3.5 MPa to about 34.5 MPa). It is. Hydrogen consumption is typically about 500 to about 2,500 SCF (89.1 to 445 m ³ H ₂ / m ³ feed) per barrel of feedstock. The temperature in the reactor ranges from about 400 ° F to about 950 ° F (about 205 ° C to about 510 ° C), preferably about 650 ° F to about 850 ° F (about 340 ° C to about 455 ° C).

  Typical hydroprocessing conditions vary over a wide range. Generally, the total LHSV is about 0.5 to 5.0. The total pressure ranges from about 200 psig to about 2,000 psig. The hydrogen recycle rate is typically greater than 50 SCF / barrel, preferably 1,000 to 5,000 SCF / barrel. The temperature in the reactor ranges from about 400 ° F. to about 800 ° F. (about 205 ° C. to about 425 ° C.).

Separation zone In the process of the present invention, the separation zone is transported from hydrocarbons boiling in the base oil range (referred to as Fischer-Tropsch heavy fraction) from the first Fischer-Tropsch intermediate product recovered from the hydroprocessing operation. It is used to separate hydrocarbons boiling in the fuel range, i.e., naphtha and diesel (referred to as the Fischer-Tropsch light fraction). In general, the cut point for the separation of the Fischer-Tropsch heavy fraction and the Fischer-Tropsch light fraction is in the temperature range of about 550 ° F. to 750 ° F. (about 285 ° C. to about 400 ° C.). . Typically, the cut point is about 600 ° F. (315) ° C. However, due to the unique nature of the Fischer-Tropsch derivatized product, the cut point can be as low as 450 ° F. (about 230 ° C.). The exact cut point chosen depends on how much of the base oil present in the initial Fischer-Tropsch intermediate product is chosen for isomerization. The choice of how much base oil is sent to the catalytic dewaxing zone depends on the target value chosen for one or more properties of the final diesel product. In general, the lower the cut point between the heavy and light cuts, the more Fischer-Tropsch wax is sent to the catalytic dewaxing zone. More wax isomerization results in improved cold flow characteristics in the diesel product. However, most Fischer-Tropsch wax is concentrated in the higher boiling fraction. Thus, reducing to a cut point below a certain temperature reduces the benefits in the nature of the diesel product. Also, the more Fischer-Tropsch heavy fraction sent to the catalyst dewaxing zone, the larger the reactor must be to handle the increased volume of material, which means higher capital Bring costs. Accordingly, those skilled in the art will recognize that a balance between the size of the catalytic dewaxing reactor and the properties of the final diesel product must be achieved. At the same time, the diesel product must meet the target value for the chosen specification while minimizing the amount of material sent to the catalytic dewaxing unit.

  Separation in the separation zone is usually performed at a temperature that is at least 50 ° F. (30 ° C.) lower than the operating temperature of the hydroprocessing reactor. This is necessary in this scheme because of the nature of the Fischer-Tropsch feed. This is in contrast to the operation of similar schemes described in the prior art for the processing of conventional petroleum derivatized feedstocks. See U.S. Pat. Nos. 5,976,354 and 6,432,297. The device configuration used in the prior art schemes is similar to the device configuration used for the schemes described herein, but the actual operation is very different. In processing conventional petroleum feedstocks, the separator is operated at substantially the same temperature as that of the hydroprocessing operation. Since the petroleum-derived fraction containing diesel is not waxy, substantially all of the diesel is recovered with the naphtha and overhead gas in the prior art process. In those schemes, substantially all of the final diesel product is not passed through the catalytic dewaxing unit. In the process of the present invention, due to the waxy nature of Fischer-Tropsch diesel, a significant amount of material contained in the final diesel product is isomerized. Typically, about 25 to about 75 volume percent of the final diesel product is passed through the catalytic dewaxing unit. The actual amount of final diesel product passed through the catalytic dewaxing unit will depend on the target value chosen for the diesel specification.

  Usually, the separation zone comprises at least two separation vessels. In the figure, the separation zone has a high temperature high pressure separator and a low temperature high pressure separator. In this scheme, the high-temperature high-pressure separator causes the initial separation of the Fischer-Tropsch heavy fraction and the Fischer-Tropsch light fraction. This separation occurs at a relatively high temperature, but is still usually at a temperature that is at least 50 ° F. (30 ° C.) lower than the temperature in the hydroprocessing reactor. In the low-temperature and high-pressure separator, the overhead gas is separated from hydrocarbons boiling in the range of transport fuel that does not pass through the catalytic dewaxing zone.

Catalytic dewaxing and hydroisomerization Catalytic dewaxing consists of three main types, conventional hydrodewaxing, full hydroisomerization dewaxing and partial hydroisomerization dewaxing. All three types are waxy hydrocarbons on catalysts containing acidic components to reduce normal and slightly branched isoparaffins in the feedstock and increase the proportion of other non-waxy species. Including passing a stream and a mixture of hydrogen. The method chosen to dewax the feedstock typically depends on the quality of the product and the wax content of the feedstock, and conventional hydrodewaxing is often used for low wax content feedstocks. preferable. The process for dewaxing can be achieved by the choice of catalyst. The general subject is outlined in Lubricant Base Stock and Wax Processing (Marcel Decker, Inc.), 194-223, by Abilino Sequeira. The decision between conventional hydrodewaxing, complete hydroisomerization dewaxing and partial hydroisomerization dewaxing is n-hexadecane as described in US Pat. No. 5,282,958. It can be done by using an isomerization test. N-Hexadecane conversion using a conventional hydrodewaxing catalyst, as measured at 96%, showed selectivity to isomerized hexadecanes of less than 10%, partially hydroisomerized dewaxing catalyst Shows selectivity to isomerized hexadecanes greater than 10% and less than 40%, complete hydroisomerization dewaxing catalyst is greater than 40%, preferably greater than 60%, most preferably 80% It shows selectivity for more isomerized hexadecanes.

In conventional hydrodewaxing, the pour point is increased by selectively cracking the wax molecules into mostly smaller paraffins using a conventional hydrodewaxing catalyst such as ZSM-5. Reduced. Metals can be added to the catalyst primarily to reduce adhesion fouling. In the present invention, conventional hydrodewaxing can be used to increase the yield of diesel in the final expected product by breaking down Fischer-Tropsch wax molecules. In the process of the present invention, paraffin isomerization is also used to improve the cold flow properties and cloud point of diesel fractions. Typical conditions for the hydroisomerization used in the present invention are temperatures of about 400 ° F. to about 800 ° F. (about 200 ° C. to about 425 ° C.), pressures of 100 psig to 2,000 psig, and about 0.2 to A space velocity of 5 hours ^-1 is included.

  Complete hydroisomerization dewaxing typically achieves high conversion levels of wax by isomerization to non-waxy isoparaffins while simultaneously minimizing conversion by cracking. Because the wax conversion can be complete or at least very sophisticated, this process is typically an additional dewaxing process to produce a lubricating base oil feedstock with an acceptable pour point. Does not need to be combined with. Complete hydroisomerization dewaxing uses a bifunctional catalyst consisting of an acidic component and an active metal component having hydrogenation activity. Both components are required to carry out the isomerization reaction. The acidic component of the catalyst used in complete hydroisomerization preferably includes mesoporous SAPOs such as SAPO-11, SAPO-31 and SAPO-41, with SAPO-11 being particularly preferred. Intermediate pore zeolites such as ZSM-22, ZSM-23, SSZ-32, ZSM-35 and ZSM-48 can also be used to perform complete hydroisomerization dewaxing. Typical active metals include molybdenum, nickel, vanadium, cobalt, tungsten, zinc, platinum and palladium. Metals, platinum and palladium are particularly preferred as active metals, with platinum being most commonly used.

  In partial hydroisomerization dewaxing, a portion of the wax is isomerized to isoparaffins using a catalyst capable of selectively isomerizing paraffins, but the wax conversion is relatively low (typically 50 % Only). At higher conversions, wax conversion by cracking becomes critical and yield loss of lubricating base oil feedstock becomes uneconomical. Like complete hydroisomerization dewaxing, the catalyst used in partial hydroisomerization dewaxing contains both an acidic component and a hydrogenation component. Acidic catalyst components useful for partial hydrodewaxing include amorphous silica aluminas, fluorinated alumina and 12-ring zeolites (such as beta, Y zeolite, L zeolite). The hydrogenation component of the catalyst is the same as already described for complete hydroisomerization dewaxing. Due to incomplete wax conversion, partial hydroisomerization dewaxing is an additional step to produce a lubricating base stock having an acceptable pour point (below about + 10 ° F. or -12 ° C.). Modern dewaxing techniques, typically solvent dewaxing, complete hydroisomerization dewaxing or conventional hydroisomerization.

  In preparing a catalyst containing a non-zeolite molecular sieve and having a hydrogenation component for use in the present invention, it is usually preferred that the metal be deposited on the catalyst using a non-aqueous method. Catalysts, particularly those containing SAPOs having metals deposited thereon using non-aqueous methods, exhibit greater selectivity and activity than catalysts using aqueous methods for depositing active metals. It was. Non-aqueous deposition of active metals on non-zeolitic molecular sieves is taught in US Pat. No. 5,939,349. In general, the method involves dissolving the active metal compound in a non-aqueous, non-reactive solvent and depositing the active metal on the molecular sieve by ion exchange or impregnation.

Hydrogen Finishing The hydrogen finishing operation is intended to improve the UV stability and color of the product. This operation is performed by saturating the double bonds present in the hydrocarbon molecule, including the double bonds found in aromatic compounds, particularly polycyclic aromatic compounds. As shown in the figure, only the Fischer-Tropsch heavy fraction that passed through the catalyst dewaxer is sent to the hydrogen finisher. A general description of the hydrogen finishing process can be found in US Pat. Nos. 3,852,207 and 4,673,487. As used in this disclosure, the term UV stability refers to the stability of a lubricating base oil or other product when exposed to ultraviolet light and oxygen. Instability means that upon exposure to ultraviolet light and air, a recognizable sediment is formed or a darker color develops resulting in haze or floc in the product. It is desirable that the diesel product produced by the process of the present invention be UV stabilized before being sold, in which case the distillate can also be hydrogen finished.

  Typically, the total pressure in the hydrogen finishing zone is from about 200 psig to about 3,000 psig, with pressures in the range of about 500 psig to about 2,000 psig being preferred. The temperature range in the hydrogen finishing zone is typically in the range of about 400 ° F. (about 205 ° C.) to about 650 ° F. (about 345 ° C.). LHSV is typically in the range of about 0.3 to about 5.0. Hydrogen is typically supplied to the hydrogen finishing zone at a rate of about 1,000 to about 10,000 SCF per barrel of feedstock. Typically, hydrogen is fed at a rate of about 3,000 SCF per barrel of feedstock.

  Suitable hydrogen finish catalysts typically contain a Group VIII metal component with an oxide support. In the hydrogen finishing catalyst, metals or compounds of metals including nickel, ruthenium, rhodium, iridium, palladium, platinum and osmium are useful. Preferably, the one or more metals are platinum, palladium or a mixture of platinum and palladium. The refractory oxide support usually consists of alumina, silica, silica-alumina, silica-alumina-zirconia and the like. The catalyst can optionally contain a zeolite component. Typical hydrogen finishing catalysts are disclosed in US Pat. Nos. 3,852,207, 4,157,294, and 4,673,487.

Diesel product In the present invention, the final diesel product is produced by blending the lower boiling fraction of the isomerized heavy fraction back to the diesel fraction recovered from the separation zone. . As shown in the figure, the isomerized heavy and light fractions are blended together in a low pressure separator. Diesel product comprising a portion of the heavy fraction is isomerized at atmospheric pressure by a unit device is illustrated as being separated lighter naphtha, from C ₄ minus fraction and the base oil. If desired, the various lubricating fractions can be further separated in a vacuum fractionation column.

  In the present invention, the nature of the diesel product can be controlled at several points in the process. The first and most important control point is the point in the separation zone. As already indicated, it controls how much waxy material contained in the diesel product undergoes the hydroisomerization operation. The second point of control is in the hydroisomerization unit. By controlling the wax conversion, the cold flow characteristics of the diesel can also be adjusted. Finally, the characteristics of the diesel product can be controlled in the fractionation stage. How much of the isomerized base oil fraction remains as part of the diesel product helps determine what the final characteristics of the diesel product will be. Those skilled in the art will recognize that there are other schemes that are not shown in the figures to perform the entire process without departing from the spirit of the invention.

  In the present invention, a diesel fraction and an isomerized base oil fraction are blended to achieve a target value for at least one diesel specification. The diesel standard is usually selected from one or more of a cold filter plugging point, cloud point and pour point. In the case of the low temperature filter clogging point, the target value is usually a temperature of −10 ° C. or lower, preferably −20 ° C. or lower. The target value of the cloud point is usually a temperature of −8 ° C. or lower, preferably −18 ° C. or lower. The target value for the pour point is typically -15 ° C or lower, preferably -25 ° C or lower.

  The cold filter clogging point (“CFPP”) is a standard test used to determine the ease with which fuel moves under suction with a filter grade that is representative of on-site equipment. The measurement is repeated periodically during stable cooling of the fuel sample, and the lowest temperature at which the minimum acceptable filterability is still obtained is recorded as the “CFPP” temperature of the sample. Details of the CFPP test and cooling configuration are specified in ASTM D-6371.

  The pour point is the temperature at which a sample of diesel fuel begins to flow under carefully controlled conditions. In this disclosure, pour point is determined by standard analytical method ASTM D-5950, unless otherwise noted.

In addition to producing a Fischer-Tropsch derivatized lubricating base oil premium diesel product, the present invention can be used to produce a Fischer-Tropsch derivatized premium lubricating base oil. Fischer-Tropsch derivatized base oils recovered from the process of the present invention typically contain only very low sulfur and aromatic content, and have excellent oxidative stability and excellent cold flow properties. In general, the lubricating base oil recovered from the process has a kinematic viscosity at 100 ° C of at least 3 cSt, preferably at least 4 cSt, a pour point lower than 20 ° C, preferably lower than -12 ° C and usually higher than 90, preferably Has a VI greater than 100. Usually, lower boiling base oils are included in the final diesel blend, so there are very low amounts of low viscosity material recovered from the vacuum distillation column.

1 is a schematic diagram illustrating a process scheme representing one embodiment of the present invention.

Claims (7)

(a) in the hydrotreating zone, under hydrotreating conditions, from Fischer-Tropsch synthesis in the presence of a hydrotreating catalyst intended to saturate olefins and remove oxygenates present in the feedstock. Treating the recovered waxy Fischer-Tropsch feed, thereby producing a first Fischer-Tropsch intermediate product with reduced olefins and oxygenates compared to the Fischer-Tropsch feed The process of
(b) The first Fischer-Tropsch intermediate product is separated into a Fischer-Tropsch heavy fraction and a Fischer-Tropsch light fraction in the separation zone, and the Fischer-Tropsch light fraction is 232 ° C to 399 ° C (450 ° C). A controlled boiling point characterized by a boiling range that is higher than the boiling range of the Fischer-Tropsch light fraction. A separation step under separation conditions;
(c) subjecting the Fischer-Tropsch heavy fraction to a hydroisomerization catalyst and hydroisomerization conditions selected to improve the low temperature flow characteristics of the Fischer-Tropsch heavy fraction in the hydroisomerization zone. The step of contacting and collecting the isomerized Fischer-Tropsch heavy fraction,
(C ′) blending the isomerized Fischer-Tropsch heavy fraction with the Fischer-Tropsch light fraction in a hydrogen finishing zone under hydrogen finishing conditions with the Fischer-Tropsch heavy fraction. Before intermediate process to finish hydrogen,
(d) mixing the isomerized and hydrogen-finished Fischer-Tropsch heavy fraction with a portion of the Fischer-Tropsch light fraction of step (b); and
(e) recovering, from the blend, a Fischer-Tropsch derivatized diesel product and a lubricating base oil that meet a target value for at least one preselected specification value for diesel fuel;
The conversion of Fischer-Tropsch feed in the hydrotreating zone is 20% or less, the hydrotreating conditions are 1.48 MPa to 13.9 MPa (200 psig to 2,000 psig) hydrogen partial pressure, 205 ° C to 427 ° C (400 At least one active metal selected from group VIIIA of the periodic table of elements and VIB of the periodic table of elements, including a temperature in the range of ° F to 800 ° F, LHSV of 0.5 to 5.0 Containing at least one active metal selected from the group, the active metals being present on the refractory support,
The pressure in the hydrogen treatment area and the hydrogen finishing area are the same,
The hydroisomerization zone is operated at a lower pressure than the hydroprocessing zone and the hydrogen finishing zone.
A method for producing Fischer-Tropsch premium diesel fuel and lubricating base oil. (a) in the hydrotreating zone, under hydrotreating conditions, from Fischer-Tropsch synthesis in the presence of a hydrotreating catalyst intended to saturate olefins and remove oxygenates present in the feedstock. Treating the recovered waxy Fischer-Tropsch feed, thereby producing a first Fischer-Tropsch intermediate product with reduced olefins and oxygenates compared to the Fischer-Tropsch feed The process of
(b) In the separation zone, the first Fischer-Tropsch intermediate product is separated into a Fischer-Tropsch heavy fraction and a Fischer-Tropsch light fraction at a Fischer-Tropsch light fraction of 232 ° C to 399 ° C (450 ° C). A controlled boiling point characterized by a boiling range that is higher than the boiling range of the Fischer-Tropsch light fraction. A separation step under separation conditions;
(c) subjecting the Fischer-Tropsch heavy fraction to a hydroisomerization catalyst and hydroisomerization conditions selected to improve the low temperature flow characteristics of the Fischer-Tropsch heavy fraction in the hydroisomerization zone. The step of contacting and collecting the isomerized Fischer-Tropsch heavy fraction,
(C ′) blending the isomerized Fischer-Tropsch heavy fraction with the Fischer-Tropsch light fraction in a hydrogen finishing zone under hydrogen finishing conditions with the Fischer-Tropsch heavy fraction. Before intermediate process to finish hydrogen,
(d) mixing the isomerized and hydrogen-finished Fischer-Tropsch heavy fraction with a portion of the Fischer-Tropsch light fraction of step (b); and
(e) recovering, from the blend, a Fischer-Tropsch derivatized diesel product and a lubricating base oil that meet a target value for at least one preselected specification value for diesel fuel;
The conversion of Fischer-Tropsch feed in the hydrotreating zone is 20% or less, the hydrotreating conditions are 1.48 MPa to 13.9 MPa (200 psig to 2,000 psig) hydrogen partial pressure, 205 ° C to 427 ° C (400 At least one active metal selected from group VIIIA of the periodic table of elements and VIB of the periodic table of elements, including a temperature in the range of ° F to 800 ° F, LHSV of 0.5 to 5.0 Containing at least one active metal selected from the group, the active metals being present on the refractory support,
The pressure in the hydrogen treatment area and the hydrogen finishing area are the same,
The hydroisomerization zone is operated at a lower pressure than the hydroprocessing zone and the hydrogen finishing zone.
A method for producing a Fischer-Tropsch premium diesel fuel and a lubricating base oil, comprising:
The separation zone of step (b) is divided into at least a first intermediate separation zone and a second intermediate separation zone, and the separation of said step (b) is carried out from the first intermediate separation zone with a Fischer-Tropsch heavy fraction and a Fischer fraction. Tropsch light fraction and a hydrogen-rich C ₄ mixture with the additional step of recovering separately containing a negative fraction (i), the mixture of the second containing Fischer-Tropsch light fraction and a hydrogen-rich C ₄ minus fraction An additional step (ii) for feeding to the intermediate separation zone and an additional step (iii) for separately collecting the Fischer-Tropsch light fraction and the hydrogen-rich C ₄ minus fraction from the second intermediate separation zone,
Hydrogen rich C ₄ minus fraction is recycled to the hydrotreating zone, sent to the hydroisomerization zone, or sent to the hydrogen finishing zone,
A stripping gas is used in the first intermediate separation zone to assist in recovering the mixture containing the Fischer-Tropsch light fraction and the hydrogen rich C ₄ minus fraction.
Method.   The hydrotreating catalyst contains a molecular sieve selected from the group consisting of ZSM-22, ZSM-23, SSZ-32, ZSM-35, ZSM-48, SAPO-11, SAPO-31 and SAPO-41. Or the method of 2.   4. A process according to claim 3, wherein the hydroisomerization catalyst contains an active metal selected from platinum, palladium or a combination of platinum and palladium.   3. A method according to claim 1 or 2, wherein the preselected standard for diesel fuel with which the Fischer-Tropsch diesel product is blended is a cold filter clogging point.   3. A method according to claim 1 or 2, wherein the preselected standard for diesel fuel with which the Fischer-Tropsch diesel product is blended is cloud point.   3. A method according to claim 1 or 2, wherein the preselected standard for diesel fuel with which the Fischer-Tropsch diesel product is blended is the pour point.

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