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
  • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
  • C10G1/08—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal with moving catalysts
  • C10G1/086—Characterised by the catalyst used

Definitions

• the present invention relates to a catalytic process for converting coal to normally liquid and gaseous products, preferably liquid products.
• the catalysts are unsupported catalyst comprised of highly dispersed molybdenum sulfide, and a noble metal in an oxidation state greater than zero, preferably greater than one, and coordinated primarily to sulfur. Additionally, the catalysts may include a promoter metal sulfide, such as nickel sulfide, cobalt sulfide, iron sulfide, or a mixture thereof. It is critical that the sulfides of the various metals be intimately mixed and highly dispersed. This invention also relates to a method of preparing such catalysts from certain noble metals, molybdenum, and promoter metal complexes.
• Coal is the most readily available and most abundant solid fossil fuel, others being tar sands and oil shale.
• the United States is particularly richly endowed with well distributed coal resources. Additionally, in the conversion of coal to synthetic fuels, it is possible to obtain liquid yields of about three to four barrels per ton of dry coal, or about four times the liquid yield/ton of other solid fossil fuels such as tar sands or shale, because these resources contain a much higher proportion of mineral matter.
• a process for converting coal to primarily liquid products comprises contacting the coal at coal liquefaction conditions with a catalysts comprised of highly dispersed molybdenum sulfide promoted with a noble metal such that the noble metal is in an oxidation state greater than O and coordinated primarily to S.
• the molybdenum sulfide can, in addition, be promoted by sulfides of one or more of metals from Ni, Co, Fe, etc.
• the noble metal is selected from Pt, Pd, Rh, and Ir.
• the noble metal is platinum and is in an oxidation state greater than 1, and in an amount from about 0.05 to 25.0 wt.% of the total catalyst, with a molar ratio of platinum to molybdenum of about 0.0002 to 0.2.
• the amount of platinum present is about 0.25 to 5.0 wt.% of the total catalyst and the molar ratio of platinum to molybdenum is about 0.001 to 0.04.
• the molar ratio of Ni, Co, or Fe/Mo can vary over a wide range but would generally be from 0.1 to 0.5.
• the catalysts are prepared from: (a) one or more noble metal complexes; (b) one or more molybdenum complexes; and (c) optionally one or more soluble, or easily dispersible, complexes of Ni, Co and Fe, etc.
• the noble metal complexes are selected from those represented by the formula ML2, when the noble metal is Pt or Pd; and ML3, when the noble metal is Rh or Ir; where M is the noble metal and L is a ligand selected from dithiocarbamates, dithiophosphates, xanthates, thioxanthates, and further wherein L has organo groups having a sufficient number of carbon atoms to render the noble metal complex soluble or easily dispersible in oil.
• Ni complexes will be ML2 and Co and Fe complexes of the type ML3.
• the molybdenum complex is also oil soluble and/or highly dispersible and is selected from: MoO2(S2CNR2)2 where R is a C1 to C18 alkyl group, a C5 to C8 cycloalkyl group, a C6 to C18 alkyl substituted cycloalkyl group, or a C6 to C18 aromatic or alkyl substituted aromatic group. or and MoO2(S2CNR2)2 where R is a C6 to C18 alkyl group, a C5 to C8 cycloalkyl group, a C6 to C18 alkyl substituted cycloalkyl group, or a C6 to C18 aromatic or alkyl substituted aromatic group.
• the noble metal complex is bis(2-ethoxyethylxanthato)Pt and the molybdenum complex is dioxo bis(n-dibutyldithiocarbamato)MoO2 VI , sometimes herein referred to as dioxoMoDTC.
• coal is used herein to designate a normally solid carbonaceous material including all ranks of coal below anthracite, such as bituminous coal, sub-bituminous coal, lignite, peat, and mixtures thereof.
• the sub-bituminous and lower ranks of coal are particularly preferred.
• the coal first be reduced to a particulate, or comminuted form.
• the coal is suitably ground or pulverized in a conventional ball mill to provide particles of a size ranging from about 10 microns up to about 1/4 inch in diameter, typically about 8 mesh (Tyler).
• the catalyst is comprised of a highly dispersed molybdenum sulfide and a noble metal such that the noble metal is in an oxidation state greater than 0, preferably greater than 1 and coordinated primarily to S.
• the catalyst optionally contains a sulfide of a promoter metal such as Ni, Co, or Fe.
• a promoter metal such as Ni, Co, or Fe.
• the noble metal is present in an amount from about 0.05 to about 25.0 wt.%, based on the total weight of the catalyst. Preferably, about 0.25 to about 5.0 wt.% of noble metal is present. Also, the noble metal is present in the above amount such that the molar ratio of noble metal to molybdenum is from about 0.0002 to about 0.2, preferably from about 0.001 to about 0.04.
• the noble metal will be coordinated primarily to sulfur. By coordinated primarily to sulfur, we mean that the noble metal will be in an oxidation state greater than 0, preferably greater than 1, and most preferably greater than 2.
• This high oxidation state will be provided by coordination with S, which can be verified by an analytical technique such as X-ray photoelectron spectroscopy (XPS) and/or Extended X-ray Absorption Fine Structure (EXAFS).
• XPS X-ray photoelectron spectroscopy
• EXAFS Extended X-ray Absorption Fine Structure
• Noble metals suitable for use herein include platinum, palladium, rhodium, and iridium. Preferred are platinum and rhodium, and more preferred is platinum.
• the catalysts of the present invention are prepared from catalyst precursors.
• the noble metal precursor can be represented by: ML2 when M is Pt or Pd, and ML3 when M is Rh or Ir where L is a ligand selected from the dithiocarbamates, dithiophosphates, xanthates, and the thioxanthates, wherein L contains organo groups having a sufficient number of carbon atoms to render the noble metal complex soluble or highly dispersed in a hydrocarbonaceous solvent or feedstock.
• the organo group can be selected from alkyl, aryl, substituted aryl, and ether groups.
• the number of carbon atoms of the organo group will be from about 4 to 30.
• the dithiocarbamates and the xanthates are preferred.
• the alkoxyalkylxanthates represented by the formula: where R1 is an alkyl group (straight, branched, or cyclic); an alkoxy substituted alkyl group; an aryl group; or a substituted aryl group, R2 is a straight or branched alkylene group, M is the noble metal, n is an integer from 1 to 4, and is equal to the oxidation state of the metal
• R1 is a straight chain alkyl group, a branched alkyl group, or an alkoxy substituted alkyl group. Most preferably, R1 comprises a straight chained alkyl group. Although the number of carbon atoms in R1 can vary broadly, typically R1 will have from 1 to 24, preferably from 2 to 12, and more preferably from 2 to 8, carbon atoms. Typically, R2 will have from 2 to 8, preferably from 2 to 4, carbon atoms. Most preferably, R1 and R2 will each have from 2 to 4 carbon atoms. R1 and R2 together should contain a sufficient number of carbon atoms such that the metal alkoxyalkylxanthate is soluble in the oil. Examples of suitable substituted groups in R1 include alkyl, aryl, alkylthio, ester groups, and the like.
• M can be a variety of metals, but, in general, will be a metal selected from the group consisting of Pt, Pd, Rh, Ru and Ir.
• Examples of the various metal alkoxyalkylxanthates that can be used in the practice of the present invention are platinum bis(ethoxyethylxanthate), platinum butoxyethylxanthate, platinum propyloxyethylxanthate, platinum isopropyloxyethylxanthate, platinum 2-ethylhexyloxyxanthate, Rh trisethoxyethylxanthate, Rh trisbutoxyethylxanthate, Rh tris(2-ethoxyethalxanthate) etc.
• the molybdenum complex is also oil soluble and oil dispersible, and can be selected from any of a large number of such complexes commonly known to be useful as lubricant additives (see for example Y. Yamamoto, et al. Wear (1986), p. 79-87, M. Umemura, et al. U.S. 4,692,256 (1987) and A. Papay, et al. U.S. 4,178,258 (1979).
• Preferred molybdenum complexes are those containing dithiocarbamate, dithiophosphate, xanthates, or thioxanthate ligands.
• Mo complexes selected from those represented by the formulas: MoO2(S2CNR2)2 where R is a C1 to C18 alkyl group, preferably for C3 to C12 alkyl group; a C5 to C8 cycloalkyl group, a C6 to C18 alkyl substituted cycloalkyl group, or a C6 to C18 aromatic or alkyl substituted aromatic group or and MoO2(S2CNR2)2 where R is a C6 to C18 alkyl group, a C5 to C8 cycloalkyl group, a C6 to C18 alkyl substituted cycloalkyl group, or a C6 to C18 aromatic or alkyl substituted aromatic group.
• Ni and Co complexes can be selected from the xanthate or dithiocarbamate group given above; Ni, Co and Fe can also be selected from dithiocarbamates as given for noble metals.
• Suitable hydrocarbon liquids include, but are not limited to, various petroleum and coal liquid distillate fractions such as naphtha, mid-distillate or vacuum gas oil. Pure liquids such as 1-methylnaphthalene, xylenes and tetralin can also be used.
• active catalysts can be carried out in an inert atmosphere or preferably under a hydrogen pressure ranging from about 250 to 2500 psig, preferably between about 500 to 1750 psig, and at temperatures between about 200° C to 480° C, preferably between about 340 to 425° C. Ratios of solvent to catalyst precursors are not critical, but are generally chosen to be between about 3:1 to 25:1.
• a source of sulfur such as elemental sulfur, CS2, H2S, mercaptan and organic sulfides, etc. can be included.
• the final catalyst is in the form of fine powder, with an average particle size of ⁇ 500 nm, and surface areas, as measured by the B.E.T. method, in excess of 200 m2/g.
• a critical feature of the catalysts of this invention is the presence of the noble metal in an oxidation state of greater than zero, and preferably greater than 1, as indicated by XPS, and in a sulfur coordination environment, as indicated by both XPS and EXAFS studies.
• the noble metal In the absence of molybdenum sulfide, the noble metal is subject to reduction to the metallic state under the conditions used in hydrotreating catalysis, this reduction being most noticeable for Pt leading to its poisoning and less activity.
• the stability of the noble metal sulfide is highly unexpected in view of the published tables of thermodynamic properties, such as those given in "S. R. Shatynski, oxidation of Metals, 11 (No.6) , 307 - 320 (1977)" which indicate that the Gibbs free energy of formation of PtS at 750° F and 10/1 H2/H2S is approximately zero.
• reduction of the noble metal leads to redistribution and growth of the particles with decreased surface area. This should lead to the loss of the beneficial effects of synergy between noble metal and molybdenum sulfides.
• the present invention can also be practiced by introducing the catalyst precursors, either as a mixture in concentrate form, or simply as the precursor complex, into the liquefaction solvent, or directly into, the reaction zone. Under reactive conditions, the catalyst of the present invention will form in situ. That is, under liquefaction conditions, the catalyst of the present invention will form as an unsupported slurry catalyst from the metal complexes used herein.
• the coal is converted, or liquefied, in accordance with the present invention by introducing the coal into a liquefaction zone in the presence of a suitable solvent and the previously described catalyst.
• the solvents employed are solvents which may contain anywhere from 1/2 to about 2 weight % donatable hydrogen, based on the weight of the total solvent.
• Preferred solvents include coal derived liquids such as coal vacuum gas oils (VGO) and coal distillates or mixture thereof, for example, a mixture of compounds having an atmospheric boiling point ranging from about 175° C to about 600° C, more preferably ranging from about 340° C to less than about 540° C.
• suitable solvents include aromatic compounds such as alkylbenzenes, alkylnaphthalenes, alkylated polycyclic aromatics, heteroaromatics, unhydrogenated or hydrogenated creosote oil, tetralin, immediate product streams from catalytic cracking of petroleum feedstocks, shale oil, or virgin petroleum streams such as vacuum gas oil or residuum, etc. and mixtures thereof.
• aromatic compounds such as alkylbenzenes, alkylnaphthalenes, alkylated polycyclic aromatics, heteroaromatics, unhydrogenated or hydrogenated creosote oil, tetralin, immediate product streams from catalytic cracking of petroleum feedstocks, shale oil, or virgin petroleum streams such as vacuum gas oil or residuum, etc. and mixtures thereof.
• the 540° C+ bottoms are also recycled to the liquefaction zone.
• the preferred catalyst particles containing a metal sulfide in a hydrocarbonaceous matrix formed within the process, are uniformly dispersed throughout the feed. Because of their ultra small size, 0.002 to 3 microns, there are typically several orders of magnitude more of these catalyst particles per cubic centimeter of oil than is possible in an expanded or fixed bed of conventional catalyst particles. The high degree of catalyst dispersion and ready access to active catalyst sites affords good reactivity control of the reactions.
• the catalyst loading is flexible, ranging from parts per million (ppm) to weight percents (the latter limited by pumping constraints in a slurry reactor). Higher catalyst loadings increase conversion to low boiling liquids, and decrease heteroatom content, with better selectivity to liquid over gas.
• the catalyst may be used in the slurry mode or, with an essentially ash free extract, in a fixed bed. Conditions may be varied to produce a more or less saturated/hydrocracked product suitable as (or for conversion to) diesel or mogas, respectively. Mild hydroconversion temperatures in the range of 340 to 425° C are preferably used.
• the oil-soluble metal-containing compound make-up (not including additional amounts from recycle) is added in an amount sufficient to provide from about 10 to less than 5000 wppm, preferably from about 25 to 950 wppm, more preferably, from about 50 to 700 wppm, most preferably from about 50 to 400 wppm, of the oil-soluble metal compound, calculated as the elemental metal, based on the weight of coal.
• Catalyst make-up rates are suitably from about 30 ppm to 500 ppm on coal. The remainder will normally be supplied from recycling the catalyst-containing 340° C+ bottoms.
• a catalyst precursor in the coal-solvent-bottoms slurry, to an active catalyst. It is usually better to form the catalyst after dissolving the soluble precursor in order to obtain better dispersion.
• One method of forming the catalyst from the precursor or oil-soluble metal compound is to heat in a premixing unit prior to the hydroconversion reaction, the mixture of metal compound, coal extract and solvent to a temperature ranging from about 260° C to about 450° C and at a pressure ranging from about 250 to about 2500 psig, in the presence of a hydrogen-containing gas.
• a sulfur-containing reagent such as H2S, CS2 (liquid), or elemental sulfur can also be introduced.
• the hydrogen-containing gas may be pure hydrogen but will generally be a hydrogen stream containing some other gaseous contaminants, for example, a hydrogen-containing stream produced from the effluent gas in a reforming process.
• the hydrogen sulfide may suitably comprise from about 1/2 to about 10 mole % of the hydrogen-containing gas mixture.
• Hydrogen sulfide may be mixed with hydrogen gas in an inlet pipe and heated up to reaction temperature in a preheater, or may be part of the recycle gas stream.
• High sulfur coals may not require an additional source of sulfur.
• the catalyst precursor treatment is suitably conducted for a period ranging from about 5 minutes to about 2 hours, preferably for a period ranging from about 10 minutes to about 1 hour, depending on the composition of the coal and the specific catalyst precursor used.
• Another method of converting a catalyst precursor or oil-soluble metal compound to a catalyst for use in the present process is to react the mixture of metal compound, coal extract and solvent with a hydrogen-containing gas in the hydroconversion zone, itself at coal hydroconversion conditions.
• oil-soluble metal compound (catalyst precursor) is preferably added to a solvent, and the catalyst formed within the mixture of coal and solvent, it is also possible to add already formed catalyst to the solvent, although as mentioned above, the dispersion may not be as good.
• a mixture of catalyst, solvent, bottoms, and coal is sent to the liquefaction zone which will now be described.
• the coal liquefaction zone is maintained at a temperature ranging from about 340° to 510° C, preferably from about 340° to 450° C, more preferably from between about 385° and 425° C, and a hydrogen partial pressure ranging from about 500 psig to about 5000 psig, preferably from about 1200 to about 3000 psig.
• the space velocity defined as the volume of the coal, bottoms, and solvent feedstock per hour per volume of reactor (V/H/V), may vary widely depending on the desired conversion level. Suitable space velocities may range broadly from about 0.1 to 10 volume feed per hour per volume of reactor, preferably from about 0.25 to 6 V/H/V, more preferably from about 0.5 to 2 V/H/V.
• the 540° C+ bottoms from the liquefaction zone may be recycled, in part, back to the liquefaction zone, if desired, to increase conversion by bottoms reaction to extinction.
• the bottoms which are purged are preferably gasified, for example by partial oxidation, along with the residue from the extraction, to produce hydrogen, carbon monoxide and heat.
• a suitable solvent:coal:bottoms ratio by weight to the hydroconversion zone will be within the range of about 2.5:1:0 to about 0.5:1:2.5. Reducing the solvent to solids ratio improves the thermal efficiency of the process because the reactor size is reduced for a given coal throughput, or allows for more throughput.
• a conversion of greater than 70% to various products based on wt% DAF (dry-ash-free) coal is achieved.
• the novel catalyst combination can offer significant improvements, for example, better liquids selectivity and conversion with a corresponding decrease in gas yield.
• the process of the invention may be conducted either as a batch or as a continuous type process.
• there are on-site upgrading units to obtain finished products for example transportation fuels.
• This example illustrates formation and characterization of an active Pt/Mo catalyst.
• a 300 cc. autoclave equipped with a magnadrive stirrer was set up to permit a continuous flow of hydrogen at elevated temperature and pressure.
• the autoclave was charged with 75 groups of coal vacuum gas oil (VGO), and then di oxo-MoDTC (3.99g.) and PtEEX (0.101g.) were added.
• the total amount of metals added corresponded to 1 wt.% on feed (0.75 g).
• the mixture was stirred at 1500 rpm, and heated to 425° C under 2000 psi H2 and held at that temperature for 4 hours. Hydrogen flow was maintained at 320 cc per min. After the run the autoclave was allowed to cool to room temperature and the catalyst collected by filtration, washed with toluene, and dried at 110° C overnight in a vacuum desiccator.
• EXAFS Extended X-ray Absorption Fine-Structure
• Liquid product from the autoclave was characterized by elemental analysis and GC distillation. Under the conditions described, 96.2% HDN and 97.8% HDS were achieved. The H/C of the product was improved to 1.290 (vs. 1.019 for the feed).
• coal conversion was determined by distillation at 540° C. From the foregoing it is believed apparent that coal conversion is promoted with small amount of Pt, and C1-C4 selectivity is also improved.
• the C1-C4 gas selectivity is defined as C1-C4 divided by conversion and multiplied by 100. It is also evident that Pt-alone at 1000 PPM is not as good as any of the Pt promoted Mo cases.

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• 1992
  • 1992-09-01 CA CA 2077328 patent/CA2077328A1/en not_active Abandoned
  • 1992-09-08 AU AU22182/92A patent/AU2218292A/en not_active Abandoned
  • 1992-09-08 BR BR9203483A patent/BR9203483A/pt not_active Application Discontinuation
  • 1992-09-09 JP JP26648292A patent/JPH05214345A/ja active Pending
  • 1992-09-09 EP EP92308168A patent/EP0532287A1/en not_active Ceased

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