Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G65/00—Treatment of hydrocarbon oils by two or more hydrotreatment processes only
  • C10G65/02—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only
  • C10G65/04—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only including only refining steps
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G47/00—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions
  • C10G47/02—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions characterised by the catalyst used
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/10—Lubricating oil

Definitions

• the invention relates to a multi-stage process for producing heavy lube oil from Fischer-Tropsch wax. More particularly the invention relates to producing a heavy lubricant base stock from wax synthesized by reacting H 2 and CO produced from natural gas in the presence of a cobalt Fischer-Tropsch catalyst, by hydrodewaxing the wax in multiple stages, with interstage separation and removal of the lighter material.
• the relatively pure waxy and paraffinic hydrocarbons synthesized by the Fischer-Tropsch process, particularly over a cobalt catalyst which maximizes higher molecular weight hydrocarbon production, are excellent sources of premium lubricant oils, including heavy lubricant oil.
• the sulfur, nitrogen and aromatics content of the waxy hydrocarbons is essentially nil and the raw hydrocarbons can therefore be passed to upgrading operations, without prior hydrogenation treatment.
• Fischer-Tropsch wax refers to the waxy hydrocarbon fraction typically removed from the synthesis reactor as liquid, but which is solid at ambient room temperature and pressure conditions.
• the heavy lubricant fraction requires deep dewaxing to produce a heavy lubricant base stock having acceptable cloud and pour points. Since it's solid wax at ambient conditions, solvent dewaxing processes cannot be used.
• the invention relates to a process for producing a heavy lubricant base stock, by hydrodewaxing Fischer-Tropsch wax having heavy hydrocarbons boiling in the heavy lubricant oil range in multiple (e.g., at least two) stages, with interstage separation and removal of the lighter material.
• a heavy lubricant base stock is made by (a) producing a synthesis gas from natural gas, (b) reacting the H 2 and CO in the gas in the presence of a cobalt Fischer- Tropsch catalyst, at reaction conditions effective to synthesize waxy hydrocarbons boiling in the heavy lubricant oil range, which are hydrodewaxed it at least two stages, with interstage separation and removal of the lighter material.
• the invention in another embodiment relates to (a) producing a synthesis gas from natural gas, (b) reacting the H 2 and CO in the gas in the presence of a cobalt Fischer-Tropsch catalyst, at reaction conditions effective to synthesize waxy hydrocarbons, including a fraction boiling in the heavy lubricant oil range, and (c) passing at least the heavy fraction to an upgrading facility in which the waxy, heavy lubricant oil hydrocarbon fraction is hydrodewaxed in at least two stages, with interstage separation and removal of the lighter material, to produce a heavy lubricant base stock.
• a process in which natural gas is converted to synthesis gas which, in turn, is converted to -hydrocarbons is referred to as a gas conversion process.
• this embodiment relates to a gas conversion process plus product upgrading by hydrodewaxing.
• the hydrodewaxing process comprises (i) hydrodewaxing the wax or waxy feed, to produce an isomerate comprising a partially dewaxed heavy lubricant oil fraction and a lower boiling hydrocarbon fraction, ( i) separating these two fractions, and (iii) further hydrodewaxing the partially hydrodewaxed heavy lubricant oil fraction in at least one additional stage, to produce a heavy lubricant base stock.
• hydrodewaxing By hydrodewaxing is meant the waxy feed and partially dewaxed heavy lubricant oil fraction are contacted with hydrogen and a hydrodewaxing , catalyst that dewaxes mostly by hydroisomerization, and not by hydrocracking. This excludes dewaxing catalysts such as ZSM-5, which dewax mostly by hydrocracking the waxy molecules, particularly a heavy lubricant fraction, to hydrocarbons boiling below the desired product range.
• a hydrodewaxing catalyst comprising a ZSM-48 zeolite (ZSM-48 zeolites herein include EU-2, EU-11 and ZBM-30 which are structurally equivalent) component and a hydrogenation component, has been found to be particularly useful in the process of the invention and is used in at least one, and preferably all of the hydrodewaxing reaction stages.
• ZSM-48 zeolites herein include EU-2, EU-11 and ZBM-30 which are structurally equivalent component and a hydrogenation component
• heavy lubricant fraction is meant hydrocarbons having an initial boiling point in the range of from about 850- 950°F (454-510°C) and an end point above 1,000°F (538°C).
• a heavy lubricant base stock has an initial boiling point of at least about 850°F (454°C), an end point above 1,000°F (538°C), preferably above 1050°F (566°C), and cloud and pour points below those possessed by the raw, unprocessed, heavy fraction in the Fischer-Tropsch wax feed entering the first stage, and any other stages between the first and last hydrodewaxing stages, of the multistage hydrodewaxing process of the invention.
• the initial and end boiling points values referred to herein are nominal and refer to the T5 and T95 cut points obtained by gas (GCD)7using'the _ methOd set forth below.
• partially dewaxed heavy lubricant fraction is meant that the heavy lubricant fraction has been hydrodewaxed to lower its pour point below that which it had prior to being partially dewaxed, but not as low as the desired pour point, which is achieved by further dewaxing the partially dewaxed heavy fraction in the next one or more successive hydrodewaxing reaction stages.
• the hydrogenating component of the hydrodewaxing catalyst will comprise at least one Group VIII metal and preferably at least one noble metal, as in platinum and palladium.
• the use of at least two reaction stages and a hydrodewaxing catalyst that dewaxes mostly by isomerization e.g., a ZSM-48 component and a noble metal component
• the process of the invention is particularly useful for producing heavy lubricant base stock oils with low cloud and pour points.
• the process of the invention eliminates the need for one or more separate hydrocracking, hydroisomerization, and catalytic or solvent dewaxing steps prior to hydrodewaxing, which are taught in the prior art and which substantially reduce product yield, particularly of the desired heavy lubricant base stock.
• the hydrodewaxing process of the invention is described above as comprising at least two hydrodewaxing stages.
• the raw Fischer-Tropsch wax feed produced by a cobalt catalyst and preferably a non-shifting cobalt catalyst need not be treated to remove aromatics, unsaturates or heteroatoms (including oxygenates), before it is passed into the first hydrodewaxing stage.
• This wax or waxy, Fischer-Tropsch synthesized hydrocarbons (these terms are used synonymously herein) is hydrodewaxed in a first stage, to produce an isomerate effluent comprising a partially dewaxed heavy lubricant oil fraction, and a lower boiling hydrocarbon fraction.
• This partially dewaxed heavy lubricant oil which now has a cloud and pour point lower than the heavy lubricant fraction in the wax feed, is separated from the lower boiling hydrocarbons and passed into a second stage, in which it is further hydrodewaxed.
• the second hydrodewaxing stage produces an isomerate effluent comprising (i) a heavy lubricant oil fraction having cloud and pour points lower than that produced in the first stage and (ii) lower boiling hydrocarbons.
• the heavy lubricant fraction is separated from the lower boiling hydrocarbons.
• the heavy lubricant isomerate produced in the second stage comprises a heavy lubricant base stock having the desired cloud and pour points.
• stage is meant one or more hydrodewaxing reaction zones, with no interzone separation of reaction products and typically, but not necessarily, refers to a separate hydrodewaxing reactor.
• a heavy lubricant base stock produced by this process is typically dehazed and/or hydrofinished at mild conditions, to improve color and stability, to form a finished lubricant base stock.
• haze is cloudiness or a lack of clarity, and is an appearance factor. Dehazing is typically achieved by either catalytic or absorptive methods to remove those constituents that result in haziness.
• Hydrofinishing is a very mild, relatively cold hydrogenating process, which employs a catalyst, hydrogen and mild reaction conditions to remove trace amounts of heteroatom compounds, aromatics and olefins, to improve oxidation stability and color.
• Hydrofinishing reaction conditions include a temperature of from 302 to 662°F (150 to 350°C) and preferably from 302 to 550°F (150 to 288°C), a total pressure of from 400 to 3000 psig. (2859 to 20786 kPa), a liquid hourly space velocity ranging from 0.1 to 5 LHSV (hr "1 ) and preferably 0.5 to 3 hr "1 .
• the hydrogen treat gas rate will range from 250 to 10000 scf/B (44.5 to 1780 m3/m 3 ).
• the catalyst will comprise a support component and one or more catalytic metal components of metal from Groups VIB (Mo, W, Cr) and/or iron group (Ni, Co) and/or noble metals (Pt, Pd) of Group VIII.
• the Groups VIB and VIII referred to herein, refers to Groups VIB and VIII as found in the Sargent- Welch Periodic Table of the Elements copyrighted in 1968 by the Sargent- Welch Scientific Company.
• the metal or metals may be present from as little as 0.1 wt. % for noble metals, to as high as " 3O wt.
• Preferred support materials are low in acid and include, for example, amorphous or crystalline metal oxides such as alumina, silica, silica alumina and ultra large pore crystalline materials known as mesoporous crystalline materials, of which MCM-41 is a preferred support component.
• MCM-41 is a preferred support component.
• the preparation and use of MCM- 41 is disclosed, for example, in U.S. patents 5,098,684, 5,227,353 and 5,573,657.
• the interstage separation during hydrodewaxing may not be exact and, as a consequence, the separated heavy fraction passed into the next hydrodewaxing stage may contain minor (e.g., less than 50, preferably less than 25 and more preferably less than 5 wt. %) amounts of lower boiling hydrocarbons. It is preferred that, after the first stage, the amount of lower boiling hydrocarbons remaining in the separated heavy fraction passed into the second any successive stages be as low as possible. This will be determined by the type of separation used (e.g., flashing or fractionation) and the requirements of the process. In each stage, a portion of the heavy lubricant fraction is lost due to conversion into hydrocarbons boiling below the heavy lubricant boiling range.
• minor e.g., less than 50, preferably less than 25 and more preferably less than 5 wt.
• the combination of the multi-stage hydrodewaxing process of the invention and the use of a dewaxing catalyst comprising a ZSM-48 zeolite component and a preferably noble metal hydrogenating component minimizes this valuable lubricant loss, as compared to the use of only a single stage.
• a heavy lubricant base stock of the invention comprises a dewaxed oil having a kinematic viscosity at 100°C of at least 8 cSt (centistokes), an initial boiling point in the range of at least about 850-950°F(454-510°C)), with an end boiling point greater than 1,000°F (538°C) and typically greater than 1050°F (566°C). It has low temperature properties able to meet target specifications or requirements. Its pour and cloud points are lower than those of the heavy lubricant oil fraction in the wax feed and in any hydrodewaxing stages upstream of the last stage. The pour point is lower than the cloud point.
• a heavy lubricant base stock will typically be a clear and bright oily liquid at room temperature and pressure conditions of 75°F (24°C) and one atmosphere (101 kPa) pressure. However, in some cases the cloud point may be higher than 75°F (24°C).
• a lubricant or finished lubricant product (these two terms are used herein synonymously) is prepared by forming a mixture of the heavy lubricant base stock described herein and an effective amount of at least one additive or, more typically, an additive package containing more than one additive.
• additives include one or i ⁇ re of a ⁇ detergent, a dispersant, an antioxidant, an antiwear additive, an extreme pressure additive, a pour point depressant, a VI improver, a friction modifier, a demulsif ⁇ er, an antioxidant, an antifoamant, a corrosion inhibitor, and a seal swell control additive.
• the heavy lubricant base stock used in forming the mixture is typically one that has been mildly hydrofinished and optionally dehazed after hydrodewaxing, to improve its color, appearance and stability.
• the waxy feed or wax fed into the first hydrodewaxing stage comprises all or a portion of the waxy hydrocarbon fraction produced in a Fischer-Tropsch hydrocarbon synthesis reactor, which is liquid at the reaction , conditions. It must contain hydrocarbons boiling above 1000°F (538°C) to produce the heavy lubricant base stock composition of the invention.
• liquid and gaseous hydrocarbon products are formed by contacting a synthesis gas comprising a mixture of H 2 and CO with a Fischer-Tropsch catalyst, in which the H 2 and CO react to form hydrocarbons under shifting or non-shifting conditions and, in the process of the invention, under non-shifting conditions in which little or no, and preferably no water gas shift reaction occurs, particularly when the catalytic metal comprises Co.
• the synthesis gas typically contains less than 0.1 vppm and preferably less than 50 vppb of sulfur or nitrogen in the form of one or more sulfur and nitrogen-bearing compounds.
• the cobalt Fischer-Tropsch catalyst comprises a catalytically effective amount of Co and optionally one or more of Re, Ru, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic support material, preferably one which comprises one or more refractory metal oxides.
• Preferred supports for Co containing catalysts comprise titania, particularly when " employing a ⁇ slurry hydrocarbon synthes s wesTin wMch ' higher molecular weight, mostly paraffinic liquid hydrocarbon products are desired.
• Useful catalysts and their preparation are known and illustrative, but nonlimiting examples may be found, for example, in U.S. patents 4,568,663; 4,663,305; 4,542,122; 4,621,072 and 5,545,674.
• Fixed bed, fluid bed and slurry hydrocarbon synthesis processes are well known and documented in the literature. In all of these processes the synthesis gas is reacted in the presence of a suitable Fischer-Tropsch type of hydrocarbon synthesis catalyst, at reaction conditions effective to form hydrocarbons.
• hydrocarbons will be liquid, some solid (e.g., wax) and some gas at standard room temperature conditions of temperature and pressure of 25°C and one atmosphere (101 kPa) pressure.
• Slurry Fischer-Tropsch hydrocarbon synthesis processes are often preferred, because when a cobalt catalyst, and preferably a non-shifting cobalt catalyst is used, they are able to produce more of the relatively high molecular weight, paraffinic hydrocarbons useful for lubricant and heavy lubricant base stocks.
• the synthesis reactor is operated under conditions to produce at least 14 pounds of 700°F+ (371°C) hydrocarbons per 100 pounds of CO converted to hydrocarbons and preferably at least 20 pounds of 700°F+ (371°C) hydrocarbons for every 100 pounds of CO converted to hydrocarbons. Preferably less than 10 pounds of methane are formed for every 100 pounds of CO converted.
• These high 700°F+ (371°C) hydrocarbon production levels have been achieved in a slurry hydrocarbon synthesis reactor, using a catalyst having a rhenium promoted cobalt component and a titania support component.
• non-shifting is meant that less than 5 wt. % and preferably less than 1 wt. % of the carbon in the feed CO is converted to C0 2 .
• the mole ratio of the H 2 to CO in the synthesis gas is preferably the stoichiometric consumption mole ratio, which is typically — about-2 i/l.
• the synthesis'gas comprising a mixture of H and CO is passed into the reactor (injected or bubbled up into the bottom of the slurry body in a slurry synthesis reactor), in which the H 2 and CO react in the presence of the Fischer- Tropsch hydrocarbon synthesis catalyst, at conditions effective to form hydrocarbons, a portion of which are liquid at the reaction conditions (and which comprise the hydrocarbon slurry liquid in a slurry reactor).
• the synthesized hydrocarbon liquid is separated from the catalyst particles as filtrate by means such as simple filtration, although other separation means can be used.
• Some of the synthesized hydrocarbons are vapor and pass out of the hydrocarbon synthesis reactor as overhead gas, along with unreacted synthesis gas and gaseous reaction products. Some of these overhead hydrocarbon vapors, are typically condensed to liquid and combined with the hydrocarbon liquid filtrate.
• the initial boiling point of the synthesized hydrocarbons removed from the reactor as liquid will vary depending on whether or not some of the condensed hydrocarbon vapors have been combined with it.
• Hydrocarbon synthesis process conditions vary somewhat depending on the catalyst, reactor and desired products.
• Typical conditions effective to form hydrocarbons comprising mostly C 5+ paraffins, (e.g., C5+-C 2 00) and preferably C 10+ paraffins, in a fixed bed or slurry hydrocarbon synthesis process employing a catalyst comprising a supported cobalt component include, for example, temperatures, pressures and hourly gas space velocities in the range of from about 320-600°F (160 to 315.6 °C), 80-600 psi (552 to 4137 kPa) and 100-40,000 V/hr/V, expressed as standard volumes of the gaseous CO and H 2 mixture (60°F (15.6 °C), 1 arm) per hour per volume of catalyst, respectively.
• the waxy hydrocarbons or wax feed may be produced in a slurry, fixed or fluidized bed Fischer-Tropsch reactor.
• the vaporous effluent from the Fischer-Tropsch hydrocarbon synthesis reactor may be cooled to condense and recover some of the synthesized hydrocarbons that are vapor at the reaction conditions, and all or a portion of this condensate may be combined with the liquid effluent.
• the initial boiling point of the wax will vary, depending on the reactor, catalyst, conditions, amount of condensate combined with the liquid effluent, and the desired product slate. This will also result in some variations in composition.
• the entire wax fraction removed from the synthesis reactor as liquid may be fed into the first hydrodewaxing stage.
• the wax fed into the first hydrodewaxing reactor may or may not boil continuously from its initial boiling point, up to its end boiling point.
• all, most or only a portion of the lower boiling material may be removed from the wax prior to hydrodewaxing. This means that the initial boiling point of the wax feed may range from about 400-450°F up to 800°F (427°C) or more.
• the wax was produced in a slurry Fischer-Tropsch reactor, containing a rhenium promoted cobalt catalyst having a titania support component, had an initial boiling point of between about 430-450°F (221-232°C).
• This wax comprised more than 90 wt. % paraffins, with from 2-4 wt. % oxygenates and 2-5 wt. % olefins, which vary depending on the reaction conditions. Aromatics were not detectable by NMR analysis.
• the wax contained less than 1 wppm sulfur and less than 1 wppm nitrogen.
• the wt. % oxygen from oxygenates is measured by neutron activation in combination with high-resolution 1H-NMR.
• the Karl- Fischer method in ASTM standard D-4928 is used.
• Aromatics are determined by X-Ray Fluorescence (XRF), as described in ASTM Standard D-2622. Sulfur is measured by XRF as per ASTM standard D-2622 and nitrogen by syringe/inlet oxidative combustion with chemiluminescence detection per ASTM standard D-4629.
• a Fischer-Tropsch wax feed and at least two hydrodewaxing reaction stages, with interstage removal of hydrocarbons boiling below the heavy lubricant oil range, are essential features of the invention.
• a hydrodewaxing catalyst comprising a hydrogenation component, a solid acid component and a binder (zeolite catalyst), preferably the hydrogen form, is used in at least one of the reaction stages.
• Illustrative, but nonlimiting examples of suitable catalyst components useful for hydrodewaxing include, for example, ZSM-23, ZSM-35, ZSM-48, ZSM-57, ZSM-22 also known as theta one or TON, and the silica alumino- phosphates known as SAPO's (e.g., SAPO-11, 31 and 41), SSZ-32, zeolite beta, mordenite and rare earth ion exchanged ferrierite. Also useful are alumina and amorphous silica aluminas.
• a matrix material also known as a binder, which is resistant to the temperatures and other conditions employed in the dewaxing process herein.
• matrix materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides e.g., alumina. The latter may including mixtures of silica and metal oxides.
• inactive materials suitably serve as diluents to control the amount of conversion in a given process so that products can be obtained economically and orderly without employing other means for controlling the rate or reaction.
• crystalline silicate materials have been incorporated into naturally occurring clays, e.g., bentonite and kaolin. These materials, i.e., clays, oxides, etc., function, in part, as binders for the catalyst. It is desirable to provide a catalyst having good crush strength since in a petroleum refinery the catalyst is often subject to rough handling which tends to break the catalyst down into powderlike materials which cause problems in processing.
• Naturally occurring clays which can be composited with the solid acid component include the montmorillonite and kaolin families which include the sub-bentonites, and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays, or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification.
• the solid acid component can be composited with a porous matrix material such as silica-alumina, silica- magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia.
• the matrix can be in the form of a cogel. Mixtures of these components can also be used.
• the relative proportions-offinely-divided solid acid-con ⁇ ponent ⁇ and inorganic oxide gel matrix vary widely with the crystalline silicate content ranging from about 1 to about 90 percent by weight, and more usually in the range of about 2 to about 80 percent by weight, of the composite.
• a hydrodewaxing catalyst comprising a ZSM-48 zeolite component and a hydrogenation component (ZSM-48 catalyst) in at least one stage.
• ZSM-48 catalyst is used in all of the stages.
• the ZSM-48 catalyst is used to hydrodewax the waxy feed which contains the heavy lubricant fraction and also the heavy lubricant isomerate produced in the one or more subsequent stages.
• the hydrogenation component will comprise at least one Group VIII metal component and preferably a noble Group VIII metal component, as in Pt and Pd.
• Noble metal concentrations will range from about 0.1-5 wt % of the metal, and more typically from about 0.2-1 wt. %, based on the total catalyst weight, including the ZSM-48 zeolite component and any binder used in the catalyst composite.
• the Group VIII referred to herein refers to Group VIII as found in the Sargent- Welch Periodic Table of the Elements copyrighted in 1968 by the Sargent-Welch Scientific Company. Hydrodewaxing experiments conducted with Fischer-Tropsch wax have revealed that the ZSM-48 catalyst is superior to others, including, for example, rare earth ion exchanged ferrierite, mordenite, zeolite beta, SAPO-11, TON and ZSM-23, all using a Pt hydrogenating component.
• the ZSM-48 catalyst was more selective to lubricant oil production, including heavy lubricant fraction production, which means less conversion to hydrocarbons boiling below the lubricant oil range (e.g., ⁇ 650-750°F-(343-399°C-)) and less conversion of the heavy hydrocarbons to hydrocarbons boiling below the heavy lubricant range (e.g., 900-l,000°F+ (482-538°C+)). Conversion is calculated according to the -f ⁇ ltowmg-arithmetic-relati conversion as a specific example.
• 700°F+ conversion [1 - (wt. % 700°F+ fraction in ⁇ roduct)/(wt. %
• ZSM-48 The preparation of ZSM-48 is well known and is disclosed, for example, in U.S. patents 4,397,827; 4,585,747 and 5,075,269, and EP 0 142 317, the disclosures of which are incorporated herein by reference.
• Other hydrodewaxing catalysts useful in the practice of the invention include any of the well known catalysts that dewax mostly by isomerization and not by cracking or hydrocracking. Zeolites comprising ten and twelve membered ring structures are useful as dewaxing catalysts, particularly when combined with a catalytic metal hydrogenating component.
• zeolites and other catalyst components useful for hydrodewaxing include, for example, rare earth ion exchanged ferrierite, mordenite, beta alumina, zeolite beta, ZSM-23, ZSM-35, ZSM-57, ZSM-22 also known as theta one or TON, and the silica aluminophosphates known as SAPO's (e.g., SAPO- 11, 31 and 41), and SSZ- 32. Also useful are alumina and amorphous silica aluminas.
• hydrogen and hydrogen treat gas are synonymous and may be either pure hydrogen or a hydrogen- containing treat gas which is a treat gas stream containing hydrogen in an amount at least sufficient for the intended reactions, plus other gas or gasses (e.g., nitrogen and light hydiocarbons such as methane) which will not adversely -mterfere-with ⁇ oraffecteife
• gas or gasses e.g., nitrogen and light hydiocarbons such as methane
• the treat gas stream introduced into a reaction stage will preferably contain at least about 50 vol. %, more preferably at least about 80 vol. % hydrogen.
• the synthesis gas is produced from natural gas and contacted with a cobalt Fischer-Tropsch catalyst to produce the waxy hydrocarbons, which are dewaxed by the multi-stage hydrodewaxing process.
• natural gas it is not unusual for natural gas to comprise as much as 92+ mole % methane, with the remainder primarily C 2+ hydrocarbons, nitrogen and C0 2 .
• the methane has a 2: 1 H 2 :C ratio and is ideal, for producing a synthesis gas having an H 2 :CO mole ratio of nominally 2.1:1 by a combination of partial oxidation and steam reforming.
• nitrogen can form HCN and NH 3 , both of which are poisons to a cobalt Fischer-Tropsch catalyst and must therefore be removed down to levels below 1 ppm. If nitrogen is not removed from the natural gas, and/or if air is used as the source of oxygen, before converting it into synthesis gas, HCN and NH 3 must be removed from the synthesis gas, before it is passed into the one or more hydrocarbon synthesis reactors.
• a synthesis gas generator the natural gas reacts with oxygen and/or steam to form synthesis gas, which then serves as the feed for the hydrocarbon tithesis— nOwn-pro ⁇ esses f ⁇ rsy ⁇ thesis gas production include partial oxidation, catalytic steam refonriing, water gas shift reaction and combinations thereof.
• These processes include gas phase partial oxidation (GPOX), autothermal reforming (ATR), fluid bed synthesis gas generation (FBSG), partial oxidation (POX), catalytic partial oxidation (CPO), and steam reforming.
• ATR and FBSG employ oxygen and form the synthesis gas by partial oxidation and catalytic steam reforming.
• ATR and FBSG are preferred for producing synthesis gas in the practice of the invention.
• the Fischer-Tropsch wax feed comprised either the (i) 430°F+ (232°C+) waxy fraction obtained from a slurry Fischer- Tropsch reactor, in which the H 2 and CO were reacted in the presence of a titania supported cobalt rhenium catalyst to form hydrocarbons, most of which were liquid at the reaction conditions or the (ii) 1000°F+ (538°C+) fraction of the 430°F+ (232°C+) waxy fraction.
• the synthesis reactor was operating at conditions to produce at least 14 pounds (6.4 kg) of 700°F+ (371°C+) hydrocarbons per 100 pounds (45.4 kg) of CO converted to hydrocarbons.
• the raw (untreated) wax was fed into the first stage of the two and three stage runs below.
• the interstage separation cut point was 950°F (510°C). This means that only the partially hydrodewaxed 950°F+ (510°C) isomerate recovered from the proceeding stage was passed into the second stage of the two stage process and into the second and third stages of the three stage process.
• the boiling point distribution for the waxy feed used in the two and three stage runs is given in the table below.
• the hydrogen treat gas used in all the examples was pure hydrogen.
• a ZSM-48 catalyst was used for hydrodewaxing the waxy feed in all the examples. It comprised 0.6 wt. % Pt as the hydrogenating component, on a composite of the hydrogen form of the ZSM-48 zeolite and an alumina binder.
• the hydrogen form of the ZSM-48 zeolite was prepared according to the procedure in U.S. patent 5,075,269, the disclosure of which is incorporated herein by reference.
• the Pt component was added by impregnation, followed by calcining and reduction, using known procedures.
• Gas chromatograph distillations (GCD) were conducted using a high temperature GCD method modification of ASTM D-5307.
• the column consisted of a single capillary column with a thin liquid phase, less than 0.2 microns. External standards were used, consisting of a boiling point calibrant ranging from 5 to 100 carbons. A temperature programmed injector was used and, prior to injection, the samples were gently warmed using hot water. Boiling ranges were determined using this method and the T5 and T95 GCD results. Cloud point values were measured using ASTM D-5773 for Phase Tec Instruments, under the lubricant procedure method. Pour point was measured according to ASTM D-5950 for ISL Auto Pour Point measurement. Cloud and pour points in the Tables below are given in °C. Viscosity and viscosity index were measured according to the ASTM protocols D-445 and D-2270, respectively.
• reaction conditions were 635°F (336°C), 250 psig (1724 kPa), and 2300 SCF/B of H 2 and a LHSV of 1. These reaction conditions were used to achieve a target cloud point of 5°C for the 1000°F+ (538°C+) heavy lubricant base stock. The results of this run are shown in Table 1 below.
• the 430°F+ (232°C+) waxy feed was hydrodewaxed by reacting it with hydrogen over the ZSM-48 catalyst described above, to the same 1000°F+ (538°C+) heavy lubricant base stock cloud point of 5°C in two stages, according to the practice. of the invention.
• the waxy feed was hydrodewaxed in the first stage at 587°F (308°C), 250 psig. (1724 kPa) of hydrogen at a treat rate of 2300 SCF B of H 2 and a waxy feed LHSV of 1.
• the first stage isomerate was fractionated to separate the 700°F- (371°C-) fraction, to determine the extent of the 700°F+ (371°C+) feed conversion to lower boiling material and then further fractionated to separate and recover a 950°F+ (510°C+) heavy oil fraction.
• the 950°F+ (510°C) heavy oil fraction was then hydrodewaxed in a second stage at 614°F (323°C), 250 psig. (1724 kPa) H 2 at a treat gas rate of 2500 SCF/b and a heavy oil LHSV of 1.
• the second stage isomerate was fractionated to recover the final 1000°F+ (538°C+) heavy lubricant base stock. The results of this run are also shown in Table 1.
• a lubricant stock cut point is typically about 700°F (e.g., ⁇ 700°F/371°C + material)
• the total 1000°F+ (538°C+) fraction conversion to lower boiling, 1000 F- (538 C-) hydrocarbons for the single stage process was 61 %, as opposed to only 52 % using the two stage process of the invention.
• a greater yield of the heavy lubricant base stock at the same target cloud point was achieved using the process of the invention, with no loss in VI and with a lower pour/cloud point spread.
• the first stage isomerate was fractionated to separate and remove the 950°F- (610°C-) fraction, with the remaining 950°F+ (610°C-) fraction then passed into the second stage.
• the temperature was 607°F (321°C).
• the remaining, further partially dewaxed 950°F+ (610°C+) fraction was passed into the third stage, in which it was further hydrodewaxed at a temperature of 600°F (316°C).
• the third stage isomerate was fractionated to separate and recover the 1000°F+ (538°C+) heavy lubricant base stock. The results of this run are shown in Table 4, with the results from the single stage hydroisomerization of Comparative Example 1 shown for comparison. Table 4
• the amount of the desired 1000°F+ (538°C+) heavy lubricant base stock product was slightly higher using three stages, than that obtained using two stages (compare to Example 1 in which the same 1000°F+ (538°C+) heavy lubricant base stock had the same cloud point of 5°C).
• the amount of feed conversion to 700°F- (371°C-) boiling hydrocarbons using three stages was about the same as that resulting from using two stages, with both substantially less than that using only one stage. This further demonstrates the greater amount of heavy lubricant base stock yields obtained using the multiple stage hydrodewaxing process of the invention, because the waxy feed to the first stage contained substantial amounts of 950°F- (610°C-) boiling hydrocarbons.
• the first stage isomerate was fractionated to separate and remove the 950°F- (610°C-) fraction, with the remaining, partially dewaxed, heavy 950°F+ (610°C+) fraction then passed into the second stage.
• the temperature was 607°F (319°C).
• the remaining 950°F+ (610°C+) fraction was passed into the third stage, in which it was further hydrodewaxed at a temperature of 610°F (321°C).
• the third stage isomerate was fractionated to separate and recover the 1000°F+ (538°C+) heavy lubricant base stock. The results of this run are shown in Table 5, with the results from the Comparative Example 3 single stage hydrodewaxing shown for comparison.

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