NO20023683L - Quenching dewaxing reactor with recycling of heavily dewaxed product - Google Patents

Description

The invention relates to a method for quenching a dewaxing reactor with recovered heavy awaxed material. More specifically, the invention deals with catalytic awaxing of a highly paraffinic, Fischer-Tropsch synthetically produced waxy hydrocarbon fraction, in which the temperature of the exothermic awaxing reaction is regulated by recycling heavy dewaxed material back to the reactor as quench liquid.

The background of the invention

It has recently been found that premium, high-quality fuels, solvents and lubricating oils can be produced from Fischer-Tropsch wax and hydrotreated paraffin mud. Fischer-Tropsch wax is a term used to describe waxy hydrocarbons produced by a Fischer-Tropsch hydrocarbon synthesis process, in which the synthesis gas feed consisting of a mixture of H2 and CO reacts in the presence of a Fischer-Tropsch catalyst, under conditions effective to form hydrocarbons. Typical methods for producing these high-quality products from the wax include two or more of fractionation, hydroisomerization and awaxing, especially catalytic awaxing. Sometimes hydrogen treatment is necessary before hydroisomerization, especially with petroleum-derived paraffin muds. For example, the U.S. patent 4,963,672 discloses a process for converting waxy Fischer-Tropsch hydrocarbons into a high VI, low pour point lubricant base material by sequential hydrogenation, hydroisomerization and solvent awaxing. European patent publication EP 0 668 342 A1 proposes a method for the production of lubricant base oils by hydrogenation and then hydroisomerisation of a waxy Fischer-Tropsch raffinate, followed by awaxing. Hydrogenation is carried out without cracking, to lower the hydroisomerization temperature and increase catalyst life, both of which are adversely affected by the presence of oxidized compounds and heteroatoms in the waxy feed, as known to those skilled in the art.

Summary of the invention

The invention relates to catalytic awaxing of a waxy hydrocarbon feed (hereinafter "waxy feed"), in which the temperature of the exothermic awaxing reaction is regulated by recycling heavy awaxed material back to the reactor as quench liquid. The waxy feed is catalytically awoken by reaction with hydrogen in the presence of an awoken catalyst at elevated temperature and pressure. By waxy is meant inclusive hydrocarbons which solidify at standard conditions of room temperature and pressure of 24°C (75°F) and 1 atm. The heavy waxy material is that fraction of the dewaxed waxy feed having an initial boiling point in the range of about 427 to 510°C (800 to 950°F) and preferably at least 454°C (850°F) (454°C+ . At least a portion of this heavy awoken material is separated from the total awoken material and cooled to a temperature sufficient to regulate the temperature in the catalytic awoxin<g>s zone, but not to lower the cloud point. It has been found that the recovered heavy awoxed material reacts little, if at all, with the hydrogen in the awoking zone and therefore does not contribute significant heat to the exothermic awoking reaction. The waxy feed will contain at least 15, preferably at least 25 and more preferably at least 35% by weight hydrocarbons with an initial boiling point of about 427 to 510°C and preferably at least 454°C (850°F). At least 50% by weight and preferably at least 90% by weight of the waxy feed fed into the awaxing reactor will have an initial boiling point in the range of 343 to 399°C (650-750°F) (a 343 to 399°C+ fraction), with a final boiling point of at least 566°C (1050°F) and preferably greater than 566°C. A preferred waxy feed consists of highly paraffinic, Fischer-Tropsch synthetically produced hydrocarbons that have been hydroisomerized. Other, less preferred waxy hydrocarbons, such as those produced from paraffinic sludge and hydrocracked material, are treated by extraction and/or catalytic hydrorefining to remove non-paraffinic hydrocarbons such as aromatics and other unsaturated compounds, along with heteroatom compounds, to form a waxy food. The waxy feed resulting from these treatments is typically fed into the awoxer, without an intermediate hydroisomerization step. The dewaxed material is fractionated to separate and cool at least a portion of the heavy dewaxed material for recycling as coolant, along with useful lubricant and fuel product fractions.

Thus, the invention relates to a method for catalytic awaxing which consists of putting waxy, paraffinic hydrocarbon feed in contact with hydrogen, in the presence of a awaxing catalyst in a catalytic awaxing zone, under conditions of elevated temperature and pressure effective for the hydrogen to react with the feed and produce a reduced pour point awoken material, which includes a heavy fraction, separating and cooling at least a portion of the heavy fraction, and returning it to the awoken zone as a quench liquid for temperature control. More specifically, the invention relates to the process of catalytic dewaxing in which the waxy feed, consisting of hydrocarbons having an initial boiling point in the range of 343 to 399°F, which includes a 427°C+ fraction, is reacted with hydrogen in the presence of the dewaxing catalyst in a dewaxing zone at elevated temperature and pressure, to produce a reduced pour point awoken material containing a 427°C+ fraction, followed by separation of at least a portion of the 427°C+ fraction from the awoken material and cooling to a temperature above the cloud point and below the awoken temperature, and recycling the cooled awoxed material back to the awoxing zone as a quench fluid, to reduce the temperature in the awoxing zone. In a preferred embodiment, the invention relates to a process for awaxing Fischer-Tropsch synthetically produced waxy hydrocarbons by hydroisomerization of the hydrocarbons to form a hydroisomerate consisting of a waxy feed containing a 427°C+ fraction, catalytic awaxing of the feed to form an awxed material with a reduced pour point, separation of at least a proportion of heavy,

427°C+ fraction from the awoxed material, cooling of at least a proportion of the heavy fraction and returning this to the awoxing zones as a quench fluid. In a more detailed embodiment, the invention consists of an integrated process for the synthetic production of a waxy, paraffinic hydrocarbon fraction from a synthesis gas consisting of a mixture of H2 and CO, hydroisomerization of the waxy fraction to form a hydroisomerate and catalytic awaxing of the hydroisomerate in the awaxing zone, to form an awoken product with a reduced pour point containing a fraction of heavy awoken material, a portion of which is cooled and used as a quench liquid in the awoken zone, where the method consists of: a) reacting the mixture of H2 and CO in the presence of a Fischer-Tropsch hydrocarbon synthesis catalyst containing a catalytic cobalt component, at reaction conditions effective to form very pure, paraffinic, waxy hydrocarbons, at least a proportion of which is liquid at the reaction conditions; b) feeding the waxy hydrocarbons into a hydroisomerization reaction zone; c) reacting the waxy hydrocarbons with hydrogen in the presence of a bifunctional hydroisomerization catalyst in the hydroisomerization reaction zone to form a hydroisomerate consisting of hydrocarbons having an initial boiling point in the range of 343 to 399°C and a final boiling point of at least 566°C; d) catalytically awaxing the hydroisomerate in a catalytic awaxing zone to lower the pour point, by reacting it with hydrogen at elevated temperature and pressure, in the presence of a catalyst consisting of a Group VIII catalytic metal component and a crystalline-aluminosi-1 icate component, to forming an awoken material consisting of hydrocarbons having an initial boiling point above and below the range of 343 to 399°C, which includes heavy hydrocarbons having an initial boiling point in the range of 427 to 510°C; e) separating at least a portion of the heavy hydrocarbon awoken material from the rest of the awoken material; f) cooling at least a portion of the separated heavy hydrocarbon awoken material to a temperature below that in the catalytic awoken zone, and g) feeding the cooled awoken material back into the awoken reaction zone as a quench liquid.

In a preferred embodiment, the Fischer-Tropsch method is a slurry hydrocarbon synthesis process where H2 and CO react in a slurry consisting of a hydrocarbon slurry liquid, gas bubbles and a particulate hydrocarbon synthesis catalyst and the slurry liquid consists of synthetically produced hydrocarbons which are liquid at the reaction condition. The slurry liquid is withdrawn from the Fischer-Tropsch hydrocarbon synthesis reactor and introduced into the hydroisomerization reaction zone in step b).

Brief description of the drawings

Figure 1 is a schematic flow diagram of a method of awoxing which is useful in the practice of the invention. Figure 2 is a schematic flow diagram of a process for slurry Fischer-Tropsch hydrocarbon synthesis that includes an awaxing process according to the practice of the invention.

Detailed description

Hydroisomerization and other hydroconversion processes convert some of the 343 to 399°C+ hydrocarbons to hydrocarbons boiling below the 343 to 399°C (343 to 399°C-) range. While this lower boiling material may remain in the hydroconverted material (eg, the hydroisomerate), it is preferred to remove it prior to awaxing to minimize the size of the awaxing reactor and the amount of awaxing catalyst required. Removal of the lower-boiling components can be achieved, for example, by coarse rapid steaming and/or fractionation prior to awoxing. The choice is made by the professional. The lower boiling components can be used as fuel. The awoken material is separated into various desired fractions, as described above, which typically include, in addition to the 454°C+ fraction, more than one lubricant base stock (fraction). By lubricant basic raw material is meant all or a part of the 343 to 399°C+ awoken material produced by the method of the invention. As those skilled in the art know, a lubricant base material is an oil that has lubricating qualities and boils in the general range of lubricating oils and is useful for the production of various lubricants such as lubricating oils and greases.

The awoxing is performed to convert no more than 40 wt% and preferably limited to no more than 30 wt% of the 343 to 399°C+ hydroisomerate to 343 to 399°C- material. The extent of the conversion will depend on the awoxing catalyst, as well as the feed to the awoxer. In contrast to the method set forth in U.S. patent 4,963,672 referred to above, due to the very low or zero concentration of nitrogen and sulfur compounds and the very low oxygenate level in Fischer-Tropsch prepared waxy hydrocarbons, hydrogenation or hydrotreating for heteroatom removal, aromatics or other unsatd. materials not normally required prior to the hydroisomerization to form the waxy feed. Furthermore, oxygenates are the only hot rhoatom compounds present in any quantity in Fischer-Tropsch synthetically produced hydrocarbons. These oxygenates are present primarily and mostly in 204°C (400°F) hydrocarbons, which are readily separated from heavier hydrocarbons. If the waxy 343 to 399°C+ Fischer-Tropsch hydrocarbons contain less than, for example, 5% by weight of 204°C hydrocarbons, hydrotreating is usually not necessary prior to hydroisomerization to form a waxy feed. This is not the case for petroleum-derived paraffin muds, which can contain significant amounts of heteroatomic compounds, especially those containing sulfur and nitrogen, as well as aromatics and other unsaturated materials. Typical hydrotreating catalysts include well-known hydrotreating catalysts such as Co/Mo or Ni/Mo on alumina. Other hydrogen treatment catalysts include compositions of Co and/or Ni and Mo and/or W on a silica/alumina basis. Such catalysts are usually sulphide added. The hydrotreated hydrocarbons are stripped to remove H2S, water, nitrogen and other catalyst-deactivating compounds, prior to awaxing. Typical conditions for hydrotreating paraffin muds and hydrocracked hydrocarbons to form a waxy feedstock for awaxing include temperatures in the range of about 232 to 427°C (450 to 800°F), a hydrogen pressure of between about 28 to 172 bar (400 to 2500 psia) a space velocity of between about 0.5 and 3 V/V/hr (volume of feed/volume of catalyst per hour), and a hydrogen gas velocity of between 89 to 890 dm<3>/liter (500 to 5000 scf/b).

The waxy feed preferably consists of the entire 343 to 399°C+ fraction of either (i) a hydrotreated paraffinic slag or hydrocracked material from which heteroatom compounds, aromatics or other unsaturated compounds have been removed, and preferably hydroisomerized prior to dewaxing and (ii) hydroisomerized waxy hydrocarbons formed by a hydrocarbon synthesis process, with the first cut-point between 343 to 399°C, determined by the person skilled in the art, and the exact end point preferably above 566°C, determined by the feed, the catalyst and the process variables used in the synthesis. The waxy feed may also contain lower boiling materials (343 to 399°C-), if desired. While this lower boiling material is not useful as a lubricant feedstock, when prepared according to the process of the invention it is useful as a fuel. The waxy food also consists of more than 90% and typically more than 95% paraffinic hydrocarbons and this is what is meant by "paraffinic" in the context of the invention. Most of the hydrocarbons in Fischer-Tropsch wax are ordinary paraffins. Waxy feed derived by hydroisomerization of a Fischer-Tropsch waxy fraction has negligible amounts of sulfur and nitrogen compounds (eg, less than 1 ppm by weight). Fischer-Tropsch waxy feeds with these properties and which are useful for the process of the invention are derived from the wax fraction formed from a slurry Fischer-Tropsch process, with a catalyst with a catalytic cobalt component. In the practice of the invention, it is preferred that a slurry Fischer-Tropsch hydrocarbon synthesis process is used for the synthesis of the waxy feed and in particular one that uses a Fischer-Tropsch catalyst consisting of a catalytic cobalt component, to provide high alpha for the production of the more desired high molecular the paraffins.

The practice of the invention is not limited to the use of a particular de-waxing catalyst, but can be carried out with any de-waxing catalyst that will reduce the pour point of the waxy feed, and preferably a catalyst that achieves a satisfactory amount of the desired de-waxed fraction. Such catalysts consist of at least one catalytic metal component and an acidic refractory metal oxide component. The catalytic metal component may consist of one or more compounds or metals from group VIII of the periodic table and preferably at least one noble metal component, such as, but not limited to, platinum. The groups referred to hereafter refer to groups found in the Sargent-Welch Periodic Table of the Elements copyright 1968 by Sargent-Welch Scientific Company. The refractory metal oxide component preferably consists of at least one crystalline aluminosilicate and preferably at least one zeolite. These include shape-selective molecular sieves which, when combined with at least one catalytic metal component, have been demonstrated to be useful for the awaxing of Fischer-Tropsch and paraffin muds and include, for example, mordenite, ZSM-5, Ferrieritt, Zsm-11, Zsm-23, ZSM-35, ZSM-22 also known as theta one or TON, and silcoaluminophosphates known as SAPOs (5,135,638). The waxing can be achieved with the catalyst in a solid, fluidized or slurry state. Typical awaxing conditions include a temperature in the range of about 204 to 316°C (400 to 600°F), a pressure of between about 35 to 172 bar (500 to 2500 psig), a H2 treatment rate of between 89 to 890 dm<3>/ liters (500 to 5000 scf/b) for flow-through reactors and an LHSV (space velocity) of 0.1 - 10, preferably 0.2 to 2.0. The awoxing is usually carried out to convert no more than 40% by weight and preferably no more than 30% by weight of the 343 to 399°C+ hydroisomerate to lower boiling material.

A dewaxing catalyst consisting of a catalytic platinum component and a component consisting of the hydrogen form of mordenite (pt/H-mordenite) is preferred, especially for dewaxing a Fischer-Tropsch derived waxy feed. This is because it has been found that not all awaxing catalysts and conditions are equal when used to awax these very pure and highly paraffinic hydroisomers, due to the cracking conditions that occur during awaxing. These cracking reactions produce lower boiling material. For example, US Patent 3,539,498 shows that by using 0.5 wt% platinum on H-mordenite for awaxing light lubricating oil des-tillate feed (316 to 371°C (600 to 700°F)) down to a pour point at -12°C (10°F), the product yield was only 68% by volume. US Patent 4,057,488 states a 65.5 vol% yield, using platinum on H-mordenite, to awax a denitrogenated raffinate boiling between 393 to 510°C (740-950°F). It has been surprisingly and unexpectedly found that when using Pt/H mordenite to awax a hydroisomerized Fischer-Tropsch waxy feed boiling in the butter oil range (eg 343 to 399°C+), these high conversions to lower boiling hydrocarbons do not occur . When noble metal is used, the noble metal load, based on the combined weight of mordenite and noble metal, will vary from about 0.1 to 1.0 wt% and, preferably, from 0.3 to 0.7 wt%, where the noble metal preferably consists of Pt. Another noble metal, Pd, can be used in combination with Pt. It has been found that the combination Pt/H-mordenite dewaxing catalyst with a hydroisomerized waxy feed derived from a slurry Fischer-Tropsch process using a catalyst consisting of a catalytic cobalt component results in a lower pour point at a given conversion level than the same catalyst with a waxy raffinate derived from petroleum oil. This is unexpected.

During hydroisomerization of the waxy hydrocarbons to obtain the waxy feed, conversion of 343 to 399°C+ hydrocarbons to 343 to 399°C- hydrocarbons will range from about 20 to 80% by weight, preferably 30 to 70% and more preferably from about 3 0 to 60%, based on a one-time flow of the feed through the reaction zone. The waxy feed may contain minor amounts of 343 to 399°C material prior to the hydroconversion and at least a portion of this lower boiling material will also be converted to even lower boiling components. Typical hydroisomerization reaction conditions include a temperature and pressure typically in the range of 149 to 482°C (300-900°F) and 0 to 172 bar (0-2500psig), with preferred ranges of 288 to 399°, respectively C (550-750°F) and 21 to 83 bar (300-1200psig). Hydrogen treatment rates are 89 to 890 dm<3>/liter (500-5000 SCF/B), with a preferred range of 356 to 712 dm<3>/liter (2000-4000 SCF/B). The hydroisomerization catalyst consists of one or more Group VIII catalytic metal components, and preferably one or more non-noble metals, such as Co, Ni, and Fe, which also include a Group VIB metal (eg Mo or W) oxide promoter, supported on an acidic metal oxide support to give the catalyst both a hydrogenation function for hydroisomerization of the hydrocarbons and an acid hydrocracking function. The catalyst may also have a group IB metal, such as copper, as a hydrogenolysis inhibitor. The cracking and hydrogenation activity is determined by its particular composition, as is known. In a preferred embodiment, the catalytically active metal consists of cobalt and molybdenum. The acidic oxide carrier may include silica, alumina, silica-alumina, silica-alumina phosphates, titanium oxide, zirconium dioxide, vanadium oxide and other Group II, IV, V or VI oxides, as well as Y sieves, such as ultrastable Y sieves. Preferred carriers include silica, alumina and silica-alumina and, more preferably silica-alumina where the silica concentration in the bulk carrier (as opposed to surface silica) is less than about 50% by weight, preferably less than 35% by weight and more preferably 15-30 weight %. As is known, if the support is alumina, small amounts of fluorine or chlorine can be incorporated to increase acid functionality. The surface of the support will be in the range from about 180-400 m<2>/g, preferably 230-350 m<2>/g, with respectively pore volume, bulk density and lateral compressive strength in the range of 0.3 to 1.0 ml/ g and preferably 0.35-0.75 ml/g; 0.5-1.0 g/ml, and 0.8-3.5 kg/mm. A particularly preferred hydroisomerization catalyst consists of cobalt, molybdenum and, alternatively, copper on an amorphous silica-alumina support containing about 20-30% by weight silica. The production of these catalysts is well known and documented. Illustrative but non-limiting examples of such catalysts, their preparation and use can be found, for example, in U.S. Pat. patents 5,370,788 and 5,378,348.

A hydroisomerization catalyst that is particularly preferred in the implementation of the invention consists of both cobalt and molybdenum catalytic components supported on an amorphous, low-silica, alumina-silica support, and most preferably one where the cobalt component is deposited on the support and calcined before the molybdenum component is added. This catalyst contains from 10-20% by weight MoO3 and 2-5% by weight CoO on an amorphous alumina-silica support, where the silica content varies from 20-30% by weight of the support. It has been established that this catalyst has good selectivity maintenance and deactivation resistance in the case of oxidized compounds found in Fischer-Tropsch produced waxy feeds. The preparation of this catalyst is disclosed in, for example, U.S. Pat. patents 5,757,920 and 5,750,819, the disclosure of which is incorporated herein by reference.

Referring to Figure 1, a simple schematic flow diagram shows a waxing unit 10 and method useful in the practice of the invention. Thus, a hydroconversion reactor 12, a catalytic awaxing reactor 14 and a vacuum distillation tower 16 are shown. Associated with these are relief containers 18, 20 and 22, and two heat exchangers 24 and 26. A waxy, paraffinic hydrocarbon fraction is fed, via line 28, into a hydroconversion reactor 12. The waxy fraction has an initial boiling point in the range 343 to 399° C and boils continuously to a final boiling point greater than 566°C. Reactor 12 can be a hydrogenator, a hydrogen processor or a hydroisomer. In the hydroconversion reactor, the downflow waxy feed reacts with downflow hydrogen entering the reactor via line 30, in the presence of a suitable catalyst on a solid catalyst bed 32. For illustration, the waxy fraction will be that produced by a slurry Fischer-Tropsch hydrocarbon synthesis process and reactor 12 a hydroisomerization unit. The hydroisomerization catalyst in reactor 12 consists of 10-20 wt% MoO3 and 2-5 wt% CoO on an amorphous alumina-silica support, where the silica content varies from 10-30 wt%. The reaction conditions include a temperature and a hydrogen pressure of 378°C (713°F) and 50 (725 psig). During the hydroisomerization, about 40% by weight of the feed is converted to a lighter hydrocarbon fraction that boils below the initial boiling point of the waxy fraction, while the remaining 60% by weight consists of heavier hydroisomerized feed for the dewaxing operation. The hydroisomerized hydrocarbons are removed from the bottom of the reactor via line 34 and fed into a simple separation drum 18, where the lighter hydrocarbons are removed as vapor overhead fraction, via line 36. This separation may also include a fractionation column (not shown) for the separated liquid, leading it is fed into the downstream deoxidation unit. The heavier waxy feed is withdrawn from drum 18 as a liquid and fed, via line 38, into catalytic awaxing reactor 14. Reactor 14 contains a solid layer 40 with awaxing catalyst consisting of 0.5% by weight Pt on H-mordenite. Hydrogen or hydrogen-containing process gas is introduced into the reactor via line 42. The awaxing conditions in the reactor include a temperature of about 288°C (550°F) and hydrogen pressure of about 50 bar (725 psig). The waxy feed reacts with hydrogen in the presence of the dewaxing catalyst, which lowers the pour point and converts some of the feed to a lower boiling material. About 20% by volume of the waxy feed is converted to a lower-boiling material during awaxing. The awaxed hydrocarbons are removed from the awaxing reactor via line 44 and fed into a pressure relief evaporator 20, which operates at a lower pressure than the awaxing reactor. The pressure relief evaporator is also a simple drum type separator. The lighter material is removed as vapor top fraction, via line 46. The remaining 343 to 399°C+ awoken material is removed via line 48 and fed into distillation tower 16, where it is also fractionated into the desired amount of lubricant and fuel fractions, as shown. The steam top fraction is led, via line 55, through heat exchanger 24, in which a proportion of the hydrocarbon steam is condensed and the resulting liquid and steam mixture is fed, via line 25 inside the separation drum 22. The steam and liquid are separated, and the steam is removed in the top fraction, via line 27 , and the condensate is returned, via line 23, back to the top of the tower as a return flow. A portion of the top fraction liquid (23A) is withdrawn as a light product stream. Which can be used as a light lubricant basic raw material or as fuel. Less than 10% by volume of the feed is fed into the distillation tower via line 4 8 and converted into a light vacuum gas oil fraction, suitable for use in diesel. This is extracted from the tower via line 50. About 25% by volume is extracted, via line 52, as automatic transmission fluid basic raw material. About 50% by volume of the awoken distillate is extracted via line 54, as a lubricant fraction useful as a basic raw material for passenger car motor oils (engine housing motor oil). The remaining 25% by volume is a heavy lubricant basestock fraction, which is removed from the bottom of the tower via line 56. This has an initial boiling point in the range of 427 to 454°C (800-850°F) and a final boiling point of about 617°C ( 1142°F) . About 75% by volume of the heavy waxed material is fed, via line 58, for further processing into a heavy lubricant for industrial oil applications and/or heavy motor oils. The remaining 25% by volume is fed, via line 60, into and through heat exchanger 26, where it is cooled to a temperature below 288°C (550°F), and then via lines 62, 64 and 66 into reactor 14 as coolant. As shown in the example below, the quench fluid does not react with the hydrogen in the presence of the awaxing catalyst to any great extent, for reasons that are not well understood. Use of this cooled, reclaimed material maintains the awaxing reactor at a desired temperature of 288°C, without the need for cooler feed, cooling gas, other hydrocarbon coolant that will dilute the awaxed material and feed, or an indirect heat exchanger.

Figure 2 is a schematic flow diagram of an integrated hydrocarbon synthesis process useful in the practice of the invention, which includes hydroisomerization and awaxing of a Fischer-Tropsch synthetically produced waxy fraction. The same numbers in Figure 2 refer to the same reactors, heat exchangers, separators, lines and distillation towers as in Figure 1. Referring to Figure 2, integrated unit 100 consists of a slurry hydrocarbon synthesis reactor 110 which contains a three-phase slurry 112 inside, has a gas distribution bottom 114 and at the bottom in the slurry for injecting the synthesis gas from the air mixing chamber below, and liquid filtering means such as box 116, submerged in the slurry. The synthesis gas, which consists of a mixture of H2 and CO in a molar ratio of 2.1:1, is fed into the reactor via line 118, with the slurry liquid, which consists of the synthetically produced hydrocarbons which are liquid at the reaction conditions, continuously withdrawn as filtrate via line 12 0 and the gaseous reactor discharge removes the top fraction which

residual gas via line 122. The filtrate, which consists of the synthetically produced hydrocarbons which are liquid at the reaction conditions, and which contains the 343 to 399°C+ boiling fraction, is fed into hydroisomerization reactor 12, which is the same

like the one in Figure 1 and has the same catalyst in it. In the hydrocarbon synthesis reactor 110, H 2 and CO react the synthesis gas in the presence of the particulate catalyst to form the desired hydrocarbons, most of which are slurry liquid, together with the gas reaction products which are mostly water vapor and CO 2 . The circles in 112 represent the bubbles in the synthesis gas and gas products, while the filled circles represent the particulate Fischer-Tropsch hydrocarbon synthesis catalyst. The gaseous top fraction consists of water vapour, C02, gaseous hydrocarbon products, unreacted synthesis gas and smaller amounts of oxygenates. The top fraction is fed through hot and cold heat exchangers 124 and 126, respectively, where it is cooled to condense a portion of the water and hydrocarbons, and into hot and cold separators 12 8 and 13 0, respectively, to recover condensed hydrocarbon liquid. Thus, the gas top fraction is fed via line 122 through the hot heat exchanger 124 to condense out some of the water vapor and heavier hydrocarbons as liquid, with the gas and liquid mixture further fed via line 132 into separator 128, in which the water and hydrocarbon liquid are separated from the remaining the gas as a sepa-rate layer of liquid. The water layer is removed via line 134 and the hydrocarbon liquids are removed via line 136 and fed into the hydroisomerizer unit 12, together with the filtrate from filter 116. The separated hydrocarbon liquid from the hot separator 128 contains hydrocarbons that solidify at standard conditions of room temperature and pressure, and is useful as part of the waxy feed to hydroisomerization unit 12. The uncondensed gas is removed from separator 128 and passed via line 140 through the cold heat exchanger 126, to condense

more water and lighter hydrocarbons as liquid, with gas and

the liquid mixture is then led via line 142 to cold separator 130, in which the liquid is separated from the uncondensed gas as two separate layers. The water is removed via line 144 and the hydrocarbon liquid via line 146 and into line 34. The uncondensed steam

is removed in the overhead fraction via line 150. Hydrogen or hydrogen-containing process gas is fed into the tip of the hydro-isomerization unit via line 30. The hydrocarbons are hydroisomerized and the mixture of hydroisomerized hydrocarbons and gas is removed from the reactor via line 34 and fed, together with lighter hydrocarbons from line 146, into fractionating column 156, operating at atmospheric pressure or more, in which the lighter components are separated as fuel fractions, such as a naphtha fraction removed via line 158, and a jet/diesel fuel fraction removed via line 160, with the unreacted hydrogen from 13 8 and light hydrocarbon gas removed as residual gas via line 162. The heavier hydroisomerate, consisting of the desired hydrocarbons boiling in the range of lubricating oil having an initial boiling point in the range of 343 to 399°C, is removed from the bottom of the fractionating column via line 164. Thus , in this embodiment, the lighter portion of the hydroisomerate is separated from the lubricating oil the material before awoksing. This significantly reduces the load on both the awok sing unit and the subsequent vacuum tube furnace. The lubricating oil fraction with an initial boiling point of approximately 371°C and an end point above 566°C is fed via line 164 into a catalytic awaxing unit 14, which contains a solid layer 40 with an awaxing catalyst consisting of Pt/H mordenite. Hydrogen or a hydrogen-containing process gas is introduced into the top of dewaxing reactor 14, via line 42, and reacts with the hydroisomerate to lower the pour point and produce a wax

material consisting of a lubricating oil base feedstock, which is removed, together with unreacted hydrogen and gas products from the awaxing reaction, via line 44, is passed through a simple pressure relief fractionation column 20 to remove steam and gas as an overhead fraction, and then to vacuum distillation tower 16, via line 48. As is the case with the hydroisomerization, results

also catalytic awoking in that some of the basic raw material is cracked into lower-boiling material, to form a light fraction. In the vacuum tube furnace, the light fraction is separated from the dewaxed base stock and removed from the unit via line 56. While only a single base stock stream is shown for simplicity, it is more common for several base stocks of different viscosities to be produced by vacuum fractionation. Light hydrocarbon gases and any remaining unreacted hydrogen are removed in the top fraction via line 80. Most (for example more than 50%) of the heavy base material is removed via line 58 and sent for further processing into various lubricating oils. The remainder is fed, via line 60, into and through heat exchanger 26,

in which it is cooled to a temperature sufficiently below the temperature in the awaxing reactor to be used as a quench liquid. This cool quench liquid is fed, via lines 62, 64 and 66, back to the awaxing reactor, where it does not react sufficiently with hydrogen in the reactor to inhibit its action as a quench liquid.

While suitable Fischer-Tropsch reaction catalysts consist, for example, of one or more group VIII catalytic metals such as Fe, Ni, Co, Ru and Re, it is preferred in the method of the invention that the catalyst consists of a catalytic cobalt component. In one embodiment, the catalyst consists of catalytically effective amounts of Co and one or more of Re, Ru, Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic support material, preferably one consisting of one or more refractory metal oxides. Preferred supports for Co-containing catalysts consist in particular of titanium. Useful catalysts and their preparation are known and illustrative, but non-limiting examples can be found, for example, in U.S. Pat. patents 4,568,663; 4,663,305; 4,542,122; 4,621,072 and 5,545,674. In a slurry hydrocarbon synthesis process, which is a preferred method for Fischer-Tropsch type hydrocarbon synthesis in the practice of the invention, a synthesis gas consisting of a mixture of H2 and CO is bubbled up as a third phase through a slurry in the reactor consisting of a particulate Fischer-Tropsch type of hydrocarbon synthesis catalyst finely divided and suspended in a slurry liquid consisting of hydrocarbon products from the synthesis reaction which is liquid under the reaction conditions. The molar ratio between the hydrogen and the carbon monoxide can vary widely from about 0.5-4, but is more typically within the range from about 0.7 to 2.75 and preferably from about 0.7 - 2.5. The stoichiometric molar ratio for a Fischer-Tropsch hydrocarbon synthesis reaction is generally about 2.0, but in a slurry hydrocarbon synthesis process it is typically about 2.1/1 and can be increased to obtain the desired amount of hydrogen from the synthesis gas for other than the synthesis reaction. Slurry process conditions vary somewhat, depending on the catalyst and desired products. In the practice of the invention, it is preferred that the hydrocarbon synthesis reaction is carried out under conditions where little or no water gas conversion reaction occurs and more preferably with no occurrence of water gas conversion reaction during the hydrocarbon synthesis. It is also preferred to carry out the reaction under conditions to achieve an alpha of at least 0.85, preferably at least 0.9 and more preferably at least 0.92, in order to synthetically prepare more of the more desirable high molecular weight hydrocarbons. This has been achieved in a slurry process by using a catalyst containing a catalytic cobalt component. Those skilled in the art know that by alpha is meant Schultz-Flory kinetic alpha. Typical conditions effective for forming hydrocarbons consisting of mostly C5+ paraffins, (eg C5+- C2oo) and preferably C10+ paraffins, in a slurry process using a catalyst consisting of a supported cobalt component include, for example, temperature, pressure, respectively and space velocity (GHSV) in the range from about 160 - 316°C (320-600°F), 6-41 bar (80-600 psi) and 100-40,000 V/h/V, expressed as standard volumes of the gaseous CO and H2 mixture (0°C, 1 atm) per hour per volume of catalyst. The hydrocarbons which are liquid under the reaction conditions are removed from the reactor by filtration.

The invention will be better understood with reference to the example below.

Example

Fischer-Tropsch synthetic waxy hydrocarbons were formed in a slurry reactor from a synthesis gas feed consisting of a mixture of H2 and CO with a H2 and CO molar ratio of between 2.11-2.16. The slurry consists of particles from a Fischer-Tropsch hydrocarbon synthesis catalyst consisting of cobalt and rhenium and supported on titanium finely divided in a hydrocarbon slurry liquid, with the synthesis gas bubbled up through the slurry. The slurry liquid consisted of hydrocarbon products from the synthesis reaction which were liquid at the reaction conditions. These include a temperature of 218°C (425°F) and pressure of 20 bar (290 psig) and a gas feed linear velocity of from 12 to 18 cm/sec. The alpha of the synthesis step was greater than 0.9. The waxy hydrocarbons, which were liquid under the reaction conditions and which make up the slurry, were extracted from the reactor by filtration. Boiling point distributions of this waxy hydrocarbon liquid are given in Table 1.

Hydroisomerization

The waxy liquid was hydroisomerized without fractionation and therefore included 29% by weight of the material boiling below 371°C as shown in Table 1. The waxy liquid was hydroisomerized by reacting with hydrogen in the presence of a bifunctional hydroisomerization catalyst consisting of cobalt (CoO, 3.2 wt%) and molybdenum (MoO 3 , 15.2 wt%) supported on an amorphous silica alumina acid co-gel component, of which 15.5% by weight was silica. The catalyst had a surface area of 266 m<2>/g and a pore volume (P.V.H2o) of 0.64 ml/g. This catalyst was prepared by depositing and calcining the cobalt component on the support prior to depositing and calcining the molybdenum component. The conditions for the hydroisomerisation are set out in Table 2 and were chosen to achieve the target of 50% by weight conversion of the 371°C+ fraction, which is defined as:

As shown in the table, 50% of the 371°C+ waxy feed was converted to 371°C- boiling products. The hydroisomerate was fractionated to separate 371°C+ from 371°C- fractions, and the separated 371°C hydroisomerate was fractionated to produce fuel products with reduced cloud point and freezing point.

Table 3 shows the properties of the 371°C+ hydroisomerate which consists of 86.8% by weight of hydrocarbons boiling in the range of 371 to 510°C (700-950°F) and 11.6% by weight of 510°C+ hydrocarbons.

Catalytic awoksing

The 3 71°C+ hydroisomerate shown in Table 3 was catalytically dewaxed using 0.5 wt% Pt/H-mordenite catalyst to lower the pour point and form a high VI lubricant fraction base stock. In this experiment, a small up-flow pilot plant was used. The waxing conditions include an H2 pressure of 52 bar (750 psig), with a nominal process gas rate of 445 dm<3>/liter (2500 SCF/B) at 1 LHSV and a temperature of 288°C (550°F). The awoken product exiting the reactor was fractionated by standard 15/5 distillation to remove the lower-boiling fuel components produced in the awoken reactor and the 371°C+ product subjected to Hivac distillation to obtain narrower fractions, with low temperature properties measured at 388-510° C (730-950°F) and 510°C+ (950°F+) portions. The results are summarized in table 4.

The data in Table 3 respectively show yields of 86.8% by weight hydroisomerate boiling in the range 371-510°C and 11.6% by weight of the 510°C+ hydroisomerate. Thus, of the 371°C+ hydroisomerate, the 371°C+ material is 88.2 wt% and the 510°C+ material is 11.8 wt%. After awaxing, of the approx. 371°C+ awaxed material, table 4 shows that only 59.9% by weight is 371°C+, while 23.5% by weight is 510°C+ awaxed material. This thus shows a significant conversion of the 371-510°C hydroisomerate feed into the awoxer to lower boiling hydrocarbons, with virtually no conversion of the 510°C+ (950°F+) awoxed material to lower boiling hydrocarbons.

This therefore demonstrates that virtually none of the recovered heavy 510°C+ (950°F+) awoxed material used as a quench reacts with the awoxing catalyst.

It is understood that several embodiments and modifications in the practice of the invention will be obvious to, and can be easily realized by, those skilled in the art without deviating from the scope and spirit of the invention as described above. Accordingly, it is not intended that the scope of the appended claims be limited to the exact description presented above, but rather that the claims be interpreted as including all properties of patentable novelty inherent in the present invention, including all properties and embodiments who would be treated as equals thereof by those qualified in the technique that the invention encompasses.

Claims (22)

1.Catalytic awaxing process consisting of contacting a waxy paraffinic hydrocarbon with hydrogen, in the presence of a awaxing catalyst in a catalytic awaxin <g>'s zone, under conditions of elevated temperature and pressure effective for the hydrogen to react with the feed and produce an awoken material with a reduced pour point, which includes a heavy fraction, separation and cooling of at least a proportion of the heavy fraction, and returning this back to the awoken zone as a quench liquid for temperature regulation. 2. The process of claim 1 wherein the heavy awoke fraction has an initial boiling point in the range of 427-510°C (800-950°F). 3. The method of claim 2 wherein the waxy feed consists of hydrocarbons with an initial boiling point in the range of 343-399°C (650-750°F). 4. The method of claim 3 wherein the waxy feed has a final boiling point of at least 566°C (1050°F). 5. Method according to claim 4, in which the waxy food consists of a hydroisomerate. 6. Method according to claim 5, in which the awaxing catalyst consists of at least one catalytic metal component and at least one acidic, microcrystalline aluminosilicate component. 7. Method according to claim 7, in which the catalytic metal component consists of at least one metal from Group VIII. 8. Method according to claim 7, in which the metal component consists of a precious metal component. 9. Method according to claim 8, in which the waxy feed is derived from Fischer-Tropsch synthetically produced hydrocarbons. 10. Method according to claim 8 in which the waxy feed is derived from paraffin sludge or hydrocracked material which has been treated to remove non-paraffinic hydrocarbons and hero atom compounds. 11. Method according to claim 10 in which the waxy food has been hydroisomerised. 12. Method according to claim 8, in which the catalyst consists of Pt and H-mordenite. 13. An integrated process for the synthetic preparation of a waxy paraffinic hydrocarbon fraction from a synthesis gas consisting of a mixture of H2 and CO, hydroisomerization of the waxy fraction to form a hydroisomerate and catalytic awaxing of the hydroisomerate in the awaxing zone to form an awaxed product with a reduced pour point containing a fraction of heavy awoken material, where a portion is cooled and used as a quench liquid in the awoken zone, where the method consists of: a) reacting the mixture of H 2 and CO in the presence of a Fischer-Tropsch hydrocarbon synthesis catalyst containing a catalytic cobalt component, at reaction conditions effective to form very pure, paraffinic, waxy hydrocarbons, at least a proportion of which is liquid at the reaction condition; b) feeding the waxy hydrocarbons into a hydroisomerization reaction zone; c) reacting the waxy hydrocarbons with hydrogen i the presence of a bifunctional hydroisomerization catalyst in the hydroisomerization reaction zone to form a hydroisomerate consisting of hydrocarbons having an initial boiling point in the range of 343 to 399°C (650-750°F) and a final boiling point of at least 566°C (1050° F); d) catalytically awaxing the hydroisomerate in a catalytic awaxing zone to lower the pour point, by reacting it with hydrogen at elevated temperature and pressure, in the presence of a catalyst consisting of a Group VIII catalytic metal component and a crystalline-aluminosi-1 icate component, to form an awoken material consisting of hydrocarbons having an initial boiling point above and below the range of 343 to 399°C (650-750°F), which includes heavy hydrocarbons having an initial boiling point in the range of 427 to 510°C (800 to 950°F); e) separating at least a portion of the heavy hydrocarbon dewaxed material from the remainder of the dewaxed material; f) cooling at least a portion of the separated heavy hydrocarbon awoken material to a temperature below that of the catalytic awoken zone, and g) feeding the cooled awaxed material back into the awaxing reaction zone as a quench liquid. 14. Process for slurry hydrocarbon synthesis according to claim 13, in which H2 and CO react in a slurry consisting of a hydrocarbon slurry liquid, gas bubbles and a particulate hydrocarbon synthesis catalyst and in which the slurry liquid consists of synthetically produced hydrocarbons which are liquid at the reaction condition, and in which the slurry liquid is drawn from the slurry and fed into the hydroisomerization reaction zone in step b). 15. Method according to claim 14, in which the quench liquid reduces the temperature in the awoking zone. 16. The method of claim 15 wherein the waxy synthetically produced hydrocarbon fraction consists of hydrocarbons with an initial boiling point in the range of 343-399°C (650-750°F) and a final boiling point of at least 566°C (1050°F). 17. Method according to claim 16, in which the hydroisomerization catalyst consists of a Group VIII non-noble metal catalytic component on an acidic support. 18. Method according to claim 17, in which the awoken catalyst consists of a zeolite component and a noble metal component. 19. Method according to claim 18, in which the awoken catalyst consists of Pt and H-mordenite. 20. Method according to claim 18 in which the hydroisomerized catalyst consists of a cobalt and molybdenum catalytic metal component and the support consists of alumina-silica with less than 30% by weight of silica. 21. Method according to claim 14, in which the slurry liquid consists of 343-399°C (650-750°F) hydrocarbons, where at least a portion is removed before the liquid is hydroisomerised. 22. The process of claim 13 wherein the heavy awoke fraction has a final boiling point above 566°C (1050°F).