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
  • C10G25/00—Refining of hydrocarbon oils in the absence of hydrogen, with solid sorbents
  • C10G25/02—Refining of hydrocarbon oils in the absence of hydrogen, with solid sorbents with ion-exchange material
  • C10G25/03—Refining of hydrocarbon oils in the absence of hydrogen, with solid sorbents with ion-exchange material with crystalline alumino-silicates, e.g. molecular sieves
  • C10G25/05—Removal of non-hydrocarbon compounds, e.g. sulfur compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0222—Compounds of Mn, Re
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0225—Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt
  • B01J20/0229—Compounds of Fe
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0233—Compounds of Cu, Ag, Au
  • B01J20/0237—Compounds of Cu
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/024—Compounds of Zn, Cd, Hg
  • B01J20/0244—Compounds of Zn
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
  • B01J20/08—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04 comprising aluminium oxide or hydroxide; comprising bauxite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
  • B01J20/16—Alumino-silicates
  • B01J20/18—Synthetic zeolitic molecular sieves
  • B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
  • B01J20/2803—Sorbents comprising a binder, e.g. for forming aggregated, agglomerated or granulated products
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
  • B01J20/28052—Several layers of identical or different sorbents stacked in a housing, e.g. in a column
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J20/28057—Surface area, e.g. B.E.T specific surface area
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
  • C10K1/00—Purifying combustible gases containing carbon monoxide
  • C10K1/32—Purifying combustible gases containing carbon monoxide with selectively adsorptive solids, e.g. active carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2220/00—Aspects relating to sorbent materials
  • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
  • B01J2220/42—Materials comprising a mixture of inorganic materials

Definitions

• the present invention relates to a novel method for producing a substantially desulfurized hydrocarbon fuel stream, particularly for hydrogen generation, and more particularly utilized within a fuel cell processing train, by passing a nondesulfurized hydrocarbon fuel stream, particularly natural gas, propane or liquefied petroleum gas
• The. present invention further relates to a system for generating electricity within a fuel cell processing train from a substantially desulfurized hydrocarbon fuel stream, particularly desulfurized natural gas, propane or LPG, wherein the hydrocarbon fuel stream is desulfurized using the above-described sequential sulfur adsorbent bed system.
• the present invention further includes a desulfurization system used for hydrogen generation, particularly within a fuel cell processing train for desulfurizing hydrocarbon fuel streams, particularly natural gas, propane or LPG, at temperatures as low as ambient temperatures.
• the hydrocarbon fuel stream can be derived from a number of conventional fuel sources with the preferred fuel sources including natural gas, propane and LPG.
• a conventional hydrogen generation system particularly a fuel cell processing train
• the hydrocarbon fuel stream is passed over and/or through a desulfurization system to be desulfurized.
• the desulfurized hydrocarbon fuel stream for such fuel cell processing train then flows into a reformer wherein the fuel stream is converted into a hydrogen-rich fuel stream.
• the fuel stream passes through one or more heat exchangers to a shift converter where the amount of CO in the fuel stream is reduced.
• the fuel stream again passes through various heat exchangers and then through a selective oxidizer or selective methanizer having one or more catalyst beds, after which the hydrogen rich fuel stream flows to the fuel cell stack where it is utilized to generate electricity.
• Raw fuels in gaseous or liquid phase, particularly natural gas, propane and LPG, are useful as a fuel source for hydrogen generation, particularly for fuel cell processing trains.
• virtually all raw fuels contain relatively high levels, up to as high as 1,000 ppm or so, but typically in the range of 20 to 500 ppm, of various naturally occurring sulfur compounds, such as, but not limited to, carbonyl sulfide, hydrogen sulfide, thiophenes, such as tetra hydro thiophene, dimethyl sulfide, various mercaptans, disulfides, sulfoxides, other organic sulfides, higher molecular weight organic sulfur compounds, and combinations thereof.
• sulfur compounds such as, but not limited to, carbonyl sulfide, hydrogen sulfide, thiophenes, such as tetra hydro thiophene, dimethyl sulfide, various mercaptans, disulfides, sulfoxides, other organic sulfides
• hydrocarbon fuel streams particularly natural gas, propane and LPG
• the quantity and composition of the sulfur compounds that may be present in the fuel streams can vary substantially.
• the presence of these sulfur-containing compounds in a hydrocarbon fuel stream can be very damaging to components of the fuel cell processing train, including the fuel cell stack itself, and must therefore be substantially removed. If not substantially removed, the sulfur compounds shorten the life expectancy of components of the fuel cell processing train.
• adsorbent that has been useful as a desulfurization agent is a "chemical" sulfur adsorbent.
• chemical desulfurization normally requires the desulfurization bed to be heated to temperatures of about 150 0 C to 400 0 C before the nondesulfurized hydrocarbon fuel streams can be passed through the chemical adsorbent desulfurization system.
• other operational problems may occur when chemical desulfurization processes are utilized. While many different desulfurization processes have been suggested for hydrocarbon fuel streams, there is still a need for improved processes for desulfurization to achieve enhanced adsorption of sulfur components over an extended range of sulfur concentrations, especially at relatively low operating temperatures and pressures, for extended periods of time.
• the desulfurization system to adsorb substantial quantities of a wide range of sulfur compounds, including particularly hydrogen sulfide, carbonyl sulfide, tetra hydro thiophene, dimethyl sulfide, various mercaptans, disulfides, sulfoxides, other organic sulfides, various higher molecular weight sulfur-containing compounds and combinations thereof. Further, it is important that the desulfurization system absorb this broad range of sulfur compounds effectively for an extended period of time to delay "breakthrough" of sulfur compounds as long as possible. "Breakthrough" occurs when the level of any sulfur compound remaining in the feed stream after desulfurization is above a predetermined level.
• Typical "breakthrough" levels for sulfur compounds occur at 1 ppm or so.
• breakthrough by virtually any one of the sulfur compounds present in the hydrocarbon fuel stream is disadvantageous as substantially all sulfur compounds cause damage to components of a hydrogen generation system, particularly for a fuel cell processing train.
• adsorbents While effective as adsorbents for some sulfur compounds, can synthesize the production of additional sulfur compounds even as they are removing some of the sulfur compounds that are present in the hydrocarbon fuel stream. (These additional sulfur compounds are referred to herein as "synthesized sulfur compounds.") It is important that the desulfurization system avoid the production of these synthesized sulfur compounds to the greatest extent possible and for the longest period of time possible.
• the present invention is a process for supplying a substantially desulfurized hydrocarbon fuel stream for hydrogen generation, particularly for use in a fuel cell processing train comprising providing a nondesulfurized hydrocarbon fuel stream, preparing a desulfurization system comprising a sequential sulfur adsorbent bed system comprising a calcium exchanged zeolite sulfur adsorbent and at least one selective sulfur adsorbent, and passing the nondesulfurized hydrocarbon fuel stream through or over the desulfurization system at a temperature optimally less than 100 0 C to produce a substantially desulfurized hydrocarbon fuel stream with desulfurization levels as low as about 50 ppb or so.
• the composition and choice of the selective sulfur adsorbent (s) and the sequence of use of the selective sulfur adsorbent (s) and the calcium exchanged zeolite within the desulfurization system depends on the composition of the sulfur compounds which are present in that fuel stream.
• the invention is also a system for generating electricity from a fuel cell processing train by use of a substantially desulfurized hydrocarbon fuel stream comprising preparing a fuel cell processing train containing the desulfurization system described above, passing a nondesulfurized hydrocarbon fuel cell fuel stream through the desulfurization system at a temperature preferably less than 100 0 C, and introducing the substantially desulfurized hydrocarbon fuel stream to the remaining components of the fuel cell processing train.
• the invention is also a desulfurization system for hydrogen generation, particularly for use in a fuel cell processing train, comprising an inlet for receiving a nondesulfurized hydrocarbon fuel stream, particularly natural gas, propane or LPG, the sequential adsorbent bed system described above, and an outlet for passing a substantially desulfurized hydrocarbon fuel stream downstream to the remaining components of the hydrogen generation system.
• a desulfurization system for hydrogen generation particularly for use in a fuel cell processing train, comprising an inlet for receiving a nondesulfurized hydrocarbon fuel stream, particularly natural gas, propane or LPG, the sequential adsorbent bed system described above, and an outlet for passing a substantially desulfurized hydrocarbon fuel stream downstream to the remaining components of the hydrogen generation system.
• the invention is also a sequential sulfur adsorbent bed system for hydrogen generation, particularly for use in a fuel cell processing train comprising selective sulfur adsorbent (s) and a calcium exchanged zeolite.
• selective sulfur adsorbent s
• a calcium exchanged zeolite The choice of the particular selective sulfur adsorbent or absorbents and the sequence of use of the selective sulfur adsorbent or absorbents and the zeolite within the sequential sulfur adsorbent bed depends upon the composition and quantity of the sulfur compounds that are present in the hydrocarbon fuel stream.
• One or more selective sulfur adsorbents can be utilized with the calcium exchanged zeolite to form the sequential adsorbent bed system of the invention.
• One particularly preferred selective sulfur adsorbent comprises one or more manganese compounds, iron oxide and a high surface area carrier, particularly alumina.
• An alternative preferred selective sulfur adsorbent comprises one or more manganese compounds, copper oxide and a binder material.
• Figure 1 is a graph showing the performance of the calcium exchanged zeolite discussed in Example 1 for the removal of certain sulfur compounds from a synthetic natural gas feed stream.
• Figure 2 is a graph showing the performance of the selective sulfur adsorbent of Example 2 for the removal of the sulfur compounds of Example 1 from the synthetic natural gas feed stream of Example 1.
• Figure 3 is a graph showing the performance, as discussed in Example 3, of a combination of the zeolite of Example 1 with the selective sulfur adsorbent of Example 2 for the removal of the sulfur compounds of Example 1 from the synthetic natural gas feed stream of Example 1.
• the invention includes a method for supplying a substantially desulfurized hydrocarbon fuel stream to a hydrogen generation system, particularly a fuel cell processing train.
• Raw fuel for use in such a hydrogen generation system, particularly a fuel cell processing train such as natural gas, propane and LPG, must be desulfurized prior to use because of the presence of relatively high levels of naturally occurring sulfur compounds, such as, but not limited to, hydrogen sulfide, carbonyl sulfide, thiophenes, such as tetra hydro thiophene, dimethyl sulfide, mercaptans (including ethyl, methyl, propyl and tertiary butyl mercaptan) , other sulfides, various higher molecular weight organic sulfur compounds and combinations thereof.
• sulfur compounds such as, but not limited to, hydrogen sulfide, carbonyl sulfide, thiophenes, such as tetra hydro thiophene, dimethyl sulfide,
• sulfur compounds can damage components of the hydrogen generation system and the fuel cell processing train. While numerous combinations and quantities of these sulfur compounds may be present in the fuel stream, in some situations, the sulfur compounds present in the fuel stream may be limited to only one or two such sulfur compounds.
• the level of sulfur compounds such as carbonyl sulfide, hydrogen sulfide, tetra hydro thiophene, dimethyl sulfide, mercaptans, other organic sulfur compounds, and combinations thereof may be as high as about 100 ppm. The presence of such high levels of sulfur compounds, if not removed, results in the poisoning of components of the fuel cell processing train and may foul the fuel cell stack itself.
• the inventors have surprisingly discovered that substantial desulfurization of a hydrocarbon fuel stream for fuel cell processing trains down to levels as low as 50 ppb or so can be achieved when a sequential sulfur adsorbent bed system is used as the desulfurization system comprising one or more selective sulfur adsorbents used in combination with a zeolite adsorbent, particularly a calcium exchanged zeolite, more particularly a calcium exchanged X zeolite.
• the composition and sequence of use of the components of the sequential sulfur adsorbent bed system can be adjusted depending on the composition and quantity of the sulfur compounds that are present in the hydrocarbon feed stream.
• the selective sulfur adsorbent (s) of the invention is selected from a wide variety of adsorbents.
• a “selective sulfur adsorbent” is a material that preferentially absorbs at least one of the sulfur compounds that are commonly present in hydrocarbon fuel cell fuel streams, particularly natural gas, propane or LPG, such as hydrogen sulfide, carbonyl sulfide, tetra hydro thiophene, dimethyl sulfide, mercaptans, particularly ethyl, methyl, propyl, and tertiary butyl mercaptans and combinations thereof, at a temperature below 100 0 C and pressures of about 10-250 psig or so.
• Each selective sulfur adsorbent selectively adsorbs one or more of the sulfur compounds that are commonly present in the hydrocarbon fuel cell fuel stream, preferably natural gas. However, each of these adsorbents may be less or more effective than other of the selective sulfur adsorbents for the adsorption of particular sulfur compounds or combinations of these compounds. Further, additional problems can be created in the feed stream when some of the selective sulfur adsorbents are used alone as the sulfur adsorbent, as these selective sulfur adsorbents can synthesize existing sulfur compounds into different, higher molecular weight synthesized sulfur compounds that are not removed from the fuel stream by the particular selective sulfur adsorbent.
• the desulfurization system can be substantially enhanced by utilizing a zeolite adsorbent particularly a calcium exchanged zeolite, and more particularly a calcium exchanged X zeolite, in combination with the selective sulfur adsorbent.
• adsorption of a broader range of sulfur compounds from the hydrocarbon fuel cell fuel streams may occur when more than one selective sulfur adsorbent is used in combination with the zeolite adsorbent in the sequential sulfur adsorbent bed system.
• the combination of one or more selective sulfur adsorbents with the calcium exchanged zeolite adsorbent performs surprisingly better than the individual selective sulfur adsorbents or the calcium exchanged zeolite when used individually.
• the choice and arrangement of the selective sulfur adsorbent (s) and the zeolite within the sequential sulfur adsorbent bed system can reduce the likelihood of the production of synthesized sulfur compounds that are sometimes created when only a single selective sulfur adsorbent is utilized in the desulfurization system.
• Sulfur adsorption by this system is further enhanced because some sulfur compounds, which may be synthesized to larger and more difficult to remove sulfur compounds by a particular selective sulfur adsorbent, are removed from the feed stream by the zeolite adsorbent, particularly the calcium-exchanged zeolite adsorbent, prior to synthesis by the selective sulfur adsorbent.
• Suitable selective sulfur adsorbents are selected from a group of adsorbents including, but not limited to, a group of manganese-based adsorbents, such as an adsorbent comprising substantially manganese compounds, an adsorbent which includes manganese compounds, copper oxide and a binder and an adsorbent which includes manganese compounds, iron oxide and a high surface area carrier, particularly alumina.
• a group of manganese-based adsorbents such as an adsorbent comprising substantially manganese compounds, an adsorbent which includes manganese compounds, copper oxide and a binder and an adsorbent which includes manganese compounds, iron oxide and a high surface area carrier, particularly alumina.
• useful selective sulfur adsorbents for this desulfurization system may include, but are not limited to, zinc oxide with or without a carrier, such as alumina; activated carbon with copper oxide; a zinc oxide/copper oxide blend preferably containing small quantities of carbon and alumina; copper oxide with alumina; and a copper oxide/zinc oxide blend mixed with alumina.
• a carrier such as alumina
• Other useful selective sulfur adsorbents may include nickel on silica or alumina and other known selective sulfur adsorbents containing copper, zinc, molybdenum and cobalt compounds.
• each of these selective sulfur adsorbents can be utilized and the quantity of the individual components can be modified to enhance the adsorption capacity of the overall desulfurization system, depending on the particular sulfur compounds that are present in the hydrocarbon fuel cell fuel stream and the quantity thereof.
• the selective sulfur adsorbent contains one or more manganese compounds blended with iron oxide on a high surface area support, preferably a high surface area support comprising alumina, silica, silica-alumina, titania, and other inorganic refractory oxides, with a more preferred support being a high surface area alumina.
• a high surface area the inventors are describing a support with a surface area greater than 100 m 2 /g.
• the inventors have surprisingly discovered that the ability of the, manganese compound(s) /iron oxide selective sulfur adsorbent to adsorb sulfur compounds is enhanced when the high surface area support is a high surface area alumina.
• Adsorbents comprising manganese compound(s) /iron oxide materials with high surface area alumina perform better and adsorb higher levels of sulfur compounds than when the carrier comprises other inorganic materials, even with similar surface areas. Any type of alumina with a surface area above 100 m 2 /g is within the scope of the invention.
• the preferred carrier comprises from 5 to 25% by weight, preferably from 5 to 20% by weight, and most preferably from 5 to 15% by weight of the total weight of this selective sulfur adsorbent.
• the primary function of the support material is to provide a large and accessible surface area for deposition of the active metal compounds.
• the metal compounds which are deposited on or with the high surface area support of this selective sulfur adsorbent, other than the one or more manganese compound(s), include iron oxide.
• the iron oxide and manganese compound(s) together comprise at least 60% by weight, preferably at least 70% by weight and most preferably at least 80% to 90% of this selective sulfur adsorbent, by weight.
• the quantity of iron oxide present in this selective sulfur adsorbent exceeds the quantity of the manganese compound(s) . It is preferred that the ratio of the iron oxide to the manganese compound(s) by weight, should be at least 1:1 and preferably from 1:1 to 6:1.
• the preferred loading of iron oxide on the support is in the range of 40 weight percent to 80 weight percent and, more preferably from 50 to 70 weight percent of the total weight of the selective sulfur adsorbent.
• Various forms of iron oxide may be used, such as FeO and Fe 2 Oa and mixtures thereof.
• the one or more manganese compound(s) comprise from 15 weight percent to 40 weight percent, preferably from 20 weight percent to 40 weight percent of the total weight of the selective sulfur adsorbent.
• Various forms of manganese compounds can be used including MnO 2 , Mn 2 O 3 , Mn 3 O 4 and Mn(OH) 4 and mixtures thereof.
• a promoter or promoters may also be added to this selective sulfur adsorbent, preferably an alkali or alkaline earth metal oxide and more preferably calcium oxide, in quantities from 5 to 15% by weight. While calcium oxide is the preferred promoter, other alkali or alkaline earth metal oxides, such as magnesium oxide, may also, or alternatively, be utilized with the calcium oxide.
• the iron oxide/manganese compound(s) selective sulfur adsorbent according to the present invention may be prepared by coprecipitation, decomposition, impregnation or mechanical mixing.
• this selective sulfur adsorbent is produced by coprecipitation or decomposition.
• the method chosen should guarantee that there has been an intensive blending of the components of the selective sulfur adsorbent.
• the specific pore volume of the iron oxide/manganese compound(s) adsorbent produced by those procedures determined by mercury porosimetry is preferably from 0.3 cc/g to 0.6 cc/g.
• this selective sulfur adsorbent preferably has a compacted bulk density of 0.4 to 1.1 g/cc.
• This selective sulfur adsorbent preferably is formed into moldings, especially in the form of spheres or pellets, preferably ranging in size from 0.1 cm to 1 cm in diameter.
• the surface area of this selective sulfur adsorbent is at least 100 m 2 /g and preferably from 100 m 2 /g to 300 m 2 /g.
• the ratio of this iron oxide/manganese compound(s) with alumina selective sulfur adsorbent to the calcium exchanged zeolite adsorbent is from 1:4 to 4:1, preferably 1:3 to 3:1, by volume.
• the sequence of utilization of this selective sulfur adsorbent in the sequential sulfur adsorbent bed system with the calcium exchanged zeolite adsorbent preferably places the calcium exchanged zeolite adsorbent prior to this selective sulfur adsorbent.
• This iron oxide/manganese compound (s) selective sulfur adsorbent when used alone has shown especially good sulfur adsorption when the sulfur compounds contained in a fuel cell fuel stream comprise hydrogen sulfide, carbonyl sulfide (COS) , tertiary butyl mercaptan (TBM) and ethyl mercaptan (EM) .
• COS carbonyl sulfide
• TBM tertiary butyl mercaptan
• EM ethyl mercaptan
• This selective sulfur adsorbent when utilized with the calcium-exchanged zeolite adsorbent, has shown enhanced utility for adsorption of additional sulfur compounds that are commonly present in a fuel cell fuel stream including tetra hydro thiophene (THT) and dimethyl sulfide (DMS), especially when the zeolite is placed in sequence before the iron oxide/manganese adsorbent compound(s) in the sequential sulfur adsorbent bed system.
• TAT tetra hydro thiophene
• DMS dimethyl sulfide
• some common hydrocarbon fuel streams do not contain these additional sulfur compounds.
• use of only the iron oxide ⁇ manganese compound(s) selective sulfur adsorbent without the calcium-exchanged zeolite adsorbent is an alternative preferred embodiment.
• selective sulfur adsorbents can be utilized in combination with this selective sulfur adsorbent and zeolite adsorbent for the adsorption of particular sulfur compounds from a hydrogen generation system, such as a hydrocarbon fuel cell feed stream.
• particularly useful combinations contain the calcium exchanged zeolite adsorbent with this iron oxide/manganese compound(s) with high surface area alumina selective sulfur adsorbent and also include a selective sulfur adsorbent containing carbon with copper oxide or copper oxide/zinc oxide with alumina.
• the sequence of utilization of these additional selective sulfur adsorbents with the zeolite adsorbent preferably places the zeolite adsorbent prior to the iron oxide/manganese compound(s) with high surface area alumina with the carbon/copper oxide or the copper oxide/zinc oxide with alumina selective sulfur adsorbent placed first in the sequence of the sequential sulfur adsorbent bed stream.
• the zeolite adsorbent preferably comprises an amount equal to, or greater than, the quantity of the other components in the three component system in * the sequential sulfur adsorbent bed, with quantities of the zeolite adsorbent up to 80% of the total sulfur adsorbents present in the sequential sulfur adsorbent bed system with the iron oxide/manganese compound(s) with alumina selective sulfur adsorbent comprising up to 20% and the carbon/copper oxide or copper oxide/zinc oxide with alumina selective sulfur adsorbent also comprising up to 20% of the sequential sulfur adsorbent bed system, by volume.
• An additional preferred selective sulfur adsorbent that can be utilized with the zeolite adsorbent in the sequential sulfur adsorbent bed system is comprised of one or more manganese compound(s), copper oxide and small quantities of a binder.
• the manganese compound(s) of this selective sulfur adsorbent may be utilized in any of the forms previously described for the manganese compound of the selective sulfur adsorbent described above.
• the manganese compound(s) of this selective sulfur adsorbent comprise from 50 to 80% and preferably from 60 to 75% of this selective sulfur adsorbent, by weight.
• the copper oxide comprises from 15 to 40% and preferably from 15 to 30%, by weight, of this selective sulfur adsorbent.
• the binder comprises from 5 to 20%, by weight, of this selective sulfur adsorbent.
• the binder may be selected from a wide variety of clays including bentonite, diatomaceous earth, attapulgite, kaolin, sepiolite, illite and mixtures thereof. More preferably, the binder comprises bentonite clay. Promoters may also be added to this selective sulfur adsorbent to enhance its operating characteristics. This adsorbent is prepared by conventional procedures.
• the surface area of this manganese compound(s) /copper oxide with binder selective sulfur adsorbent ranges from 100 to 300 m 2 /g, preferably from 200 to 300 m 2 /g.
• This manganese compound(s) /copper oxide/binder selective sulfur adsorbent when used alone has shown great utility for the adsorption of hydrogen sulfide, carbonyl sulfide, tertiary butyl mercaptan, ethyl mercaptan and mixtures thereof.
• this manganese compound(s) /copper oxide/binder selective sulfur adsorbent when utilized in sequence with the zeolite adsorbent in the sequential sulfur adsorbent bed system, has shown significant adsorption for sulfur compounds contained in hydrocarbon fuel cell feed streams of the same type as those described above where the selective sulfur adsorbent composition comprises iron oxide, manganese compound(s) and small quantities of a high surface area alumina.
• the ratio of this selective sulfur adsorbent with the zeolite adsorbent for the removal of sulfur compounds from a fuel cell fuel stream, particularly natural gas, propane and LPG, is from 1:4 to 4:1 and preferably from 1:3 to 3:1, by volume.
• selective sulfur adsorbents particularly of the same type, in the same quantities, and in the same sequence that may be utilized with the iron oxide/manganese compound(s) with small quantities of high surface area alumina, may also be utilized with this selective sulfur adsorbent and the zeolite adsorbent to form a three component system to enhance the adsorption of particular sulfur compounds that are present in a fuel cell fuel stream.
• the choice of the particular selective sulfur adsorbent or adsorbents used can be adjusted depending on the particular sulfur compounds that are present in the feed stream and their quantity.
• An additional selective sulfur adsorbent that can be utilized with the zeolite adsorbent in the sequential sulfur adsorbent bed system in place of, or in addition to, the above described selective sulfur adsorbents comprises zinc oxide alone or in combination with a carrier. While alumina is the preferred carrier, other carriers with similar performance characteristics can be utilized.
• the zinc oxide comprises at least 60%, preferably from 60 to 95%, and more preferably from 70 to 90%, by weight, of the selective sulfur adsorbent with the remaining portion preferably comprising alumina.
• Additives may be added to this selective sulfur adsorbent to enhance its capacity to absorb sulfur compounds or other performance characteristics.
• the surface area of this selective sulfur adsorbent ranges from 5 to 75 m 2 /g and preferably from 10 to 50 m 2 /g.
• This zinc oxide/alumina selective sulfur adsorbent is prepared by conventional procedures.
• the zinc oxide alumina selective sulfur adsorbent when used alone as a sulfur adsorbent has shown good sulfur adsorption when the sulfur compounds contained within the fuel cell fuel stream comprise hydrogen sulfide and ethyl mercaptan and mixtures thereof.
• the inventors have discovered that enhanced adsorption of sulfur compounds occurs when this zinc oxide with alumina selective sulfur adsorbent is utilized in a sequential sulfur adsorbent bed system with the zeolite adsorbent of the invention.
• the order of the adsorbents in the sequential sulfur adsorbent bed system utilizes the zinc oxide with alumina selective sulfur adsorbent after the zeolite.
• the ratio of the zinc oxide with alumina selective sulfur adsorbent to the zeolite adsorbent is from 1:4 to 4:1 and in a more preferred embodiment, from 1:3 to 3:1, by volume.
• sequential sulfur absorbent bed system chosen may contain only the zinc oxide with alumina selective sulfur adsorbent with the zeolite adsorbent, depending upon the sulfur content and composition within the fuel cell fuel stream, additional selective sulfur adsorbents may also be utilized as part of the sequential sulfur absorbent bed system either prior to or after the zeolite adsorbent and this selective sulfur adsorbent.
• Another selective sulfur adsorbent that can be utilized with the zeolite adsorbent of the invention in the sequential sulfur adsorbent bed system is comprised of activated carbon containing small quantities of copper oxide.
• the activated carbon comprises from 80 to 95%, preferably 85 to 95%, by weight, of this selective sulfur adsorbent with the remaining portion comprising copper oxide.
• Additives may be added to the composition to enhance its performance.
• the activated carbon/copper oxide selective sulfur adsorbent is prepared by conventional procedures.
• the surface area of the composition ranges from 300 to 1000 m 2 /g, with the preferred surface area being from 500 m 2 /g to 1000 m 2 /g. This selective sulfur adsorbent is prepared by conventional procedures.
• This activated carbon with copper oxide selective sulfur adsorbent when used alone has shown great utility for the adsorption of tetra hydro thiophene, tertiary butyl mercaptan, ethyl mercaptan and mixtures thereof.
• the quantity of the activated carbon/copper oxide selective sulfur adsorbent to be utilized with the zeolite adsorbent is at a ratio of 1:4 to 4:1, preferably 1:3 to about 3:1, by volume. Further, the preferred sequence of utilization of the selective sulfur adsorbent and the zeolite adsorbent places the zeolite adsorbent ahead of the activated carbon/copper oxide selective sulfur adsorbent in the sequential sulfur adsorbent bed system.
• This activated carbon with copper oxide selective sulfur adsorbent has also shown good adsorption capability when used in combination with other selective sulfur adsorbents and the zeolite adsorbent for the adsorption of a broad range of sulfur compounds contained in a fuel cell feed stream.
• Another useful selective sulfur adsorbent that can be utilized with the zeolite adsorbent in a sequential sulfur adsorbent bed system comprises copper oxide and zinc oxide with alumina, preferably with small quantities of carbon.
• the copper oxide comprises from 50 to 65% and more preferably from 50 to 60% of the selective sulfur adsorbent, by weight.
• the zinc oxide comprises from 20 to 35% of the selective sulfur adsorbent and the alumina comprises from 5 to 20%, preferably from 10 to 20% of the selective sulfur adsorbent, by weight.
• the quantity of the carbon, if used, should be less than 10%, preferably from 1 to 10%, by weight.
• the surface area of this selective sulfur adsorbent containing copper oxide, zinc oxide, alumina, and preferably small quantities of carbon, is from 100 to 300 m 2 /g and preferably from 100 to 200 m 2 /g.
• the process for the preparation of this selective sulfur adsorbent is conventional.
• This copper oxide/zinc oxide/alumina preferably with small quantities of carbon, selective sulfur adsorbent when used alone is especially useful for the adsorption of hydrogen sulfide, tertiary butyl mercaptan, ethyl mercaptan, carbonyl sulfide and mixtures thereof.
• the ratio of this selective sulfur adsorbent to the zeolite adsorbent when used in the sequential sulfur adsorbent bed system is from 1:4 to 4:1, preferably from 1:3 to 3:1, by volume.
• the sequence for utilization of this selective sulfur adsorbent with the zeolite adsorbent requires the zeolite adsorbent to be placed prior to this selective sulfur adsorbent in the sequential sulfur adsorbent bed system.
• selective sulfur adsorbents may also be utilized, either prior to or after this selective sulfur adsorbent in the sequential sulfur adsorbent bed system of the invention.
• An additional selective sulfur adsorbent that can be utilized with the zeolite adsorbent in the sequential sulfur adsorbent bed system comprises manganese compound(s), used alone, which may be utilized in a number of forms including Mn ⁇ 2 , Mn 2 C> 3 , Mn3U 4 and Mn(OH) 4 or mixtures thereof.
• the surface area of the manganese compound(s) range from 100 to 300 m 2 /g, and preferably from 200 to 300 m 2 /g. Additional materials may be combined with the manganese compound (s) including calcium, silver and magnesium to promote the performance of the manganese compound(s) . Conventional methods are utilized for the formation of this selective sulfur adsorbent.
• the manganese compound(s) selective sulfur adsorbent when used alone has shown great utility for the adsorption of hydrogen sulfide, tertiary butyl mercaptan, ethyl mercaptan and mixtures thereof.
• the ratio of the manganese compound(s) utilized to the zeolite adsorbent is from 1:4 to 4:1 and preferably from 1:3 to 3:1, by volume.
• the sequence of utilization of this manganese compound(s) selective sulfur adsorbent in the sequential sulfur adsorbent bed system is preferably for the zeolite sulfur adsorbent to be placed prior to the manganese compound(s) selective sulfur adsorbent.
• An additional selective sulfur adsorbent that can be utilized with the zeolite adsorbent in the sequential sulfur adsorbent bed system, comprises copper oxide with alumina, wherein the quantity of the copper oxide is from 5 to 25%, preferably from 10 to 20%, by weight, and the quantity of the alumina is from 75 to 95%, preferably from 80 to 90%, by weight.
• the surface area of this selective sulfur adsorbent is from 100 to 300 m 2 /g and preferably from 150 to 300 m 2 /g. This selective sulfur adsorbent is prepared by conventional procedures .
• This selective sulfur adsorbent when used alone has shown particularly usefulness for the adsorption of hydrogen sulfide, carbonyl sulfide, tertiary butyl mercaptan, ethyl mercaptan and mixtures thereof.
• this copper oxide with alumina selective sulfur adsorbent when utilized in sequence with the zeolite adsorbent in the sequential sulfur adsorbent bed system, has shown significant adsorption for sulfur compounds contained in fuel cell feed streams of the same type as are described above.
• the ratio of the selective sulfur adsorbent to the zeolite adsorbent is from 1:4 to 4:1, preferably from 1:3 to 3:1, by volume.
• the sequence of utilization of this selective sulfur adsorbent with the zeolite adsorbent in the sequential sulfur adsorbent bed system is preferably for the zeolite adsorbent to be placed prior to the selective sulfur adsorbent.
• Other selective sulfur adsorbents may also be utilized with this selective sulfur adsorbent for the absorption of sulfur compounds in the sequential sulfur adsorbent bed system of the invention.
• An additional selective sulfur adsorbent that can be utilized with the zeolite adsorbent in the sequential adsorbent bed system, comprises copper oxide, zinc oxide and alumina, with the quantity of copper oxide being from 15 to 25%, the quantity of the zinc oxide being from 5 to 15%, and the quantity of the alumina being from 65 to 85%, by weight.
• the surface area of this selective sulfur adsorbent is from 100 to 300 m 2 /g, preferably from 150 to 300 m 2 /g.
• This selective sulfur adsorbent catalyst is prepared by conventional procedures.
• This selective sulfur adsorbent when used alone is particularly useful for the adsorption of hydrogen sulfide, carbonyl sulfide, tertiary butyl mercaptan, ethyl mercaptan, and mixtures thereof.
• the preferred ratio of this selective sulfur adsorbent with the zeolite adsorbent is from 1:4 to 4:1 and preferably from 1:3 to 3:1, by volume.
• the sequence of use of this selective sulfur adsorbent with the zeolite adsorbent is preferably for the zeolite adsorbent to be placed prior to the selective sulfur adsorbent.
• This selective sulfur adsorbent may be utilized with other selective adsorbents as well as with the zeolite adsorbent and is a particularly preferred option, as discussed above.
• this selective sulfur adsorbent is utilized with the zeolite adsorbent and with the iron oxide, manganese compounds and alumina selective sulfur adsorbent, as previously described.
• the inventors have surprisingly discovered that the selective sulfur adsorbents described above work best when utilized within a sequential sulfur adsorbent bed system containing one or more of the selective sulfur adsorbents and the zeolite adsorbent. While several types of ion exchanged zeolites may be useful as the zeolite adsorbent, the preferred ion exchange zeolite is a calcium exchanged zeolite.
• While a number of calcium exchanged zeolites are known, including calcium exchanged zeolite A, zeolite X, zeolite Y, zeolite ZSM-5, zeolite Beta, synthetic mordenite and blends thereof, the preferred calcium exchanged zeolite is a calcium exchanged zeolite X.
• a particularly preferred calcium exchanged zeolite X is calcium exchanged, low silica zeolite X, known as "LSX", or calcium exchanged low silica faujasite, known as "LSF”.
• Zeolite X generally has a Si:Al equivalent ratio of 1.0 to 1.25.
• a conventional, non-calcium exchanged precursor synthesized LSF has the following anhydrous chemical composition: 2.0 SiO 2 :Al 2 O 3 : 0.73 Na 2 0: 0.27K 2 O, although the ratio between sodium and potassium cations can vary, sometime significantly, depending upon the process of manufacture of the LSF .
• a substantial percentage of the cations of the zeolite X are ion exchanged with calcium ions using conventional ion exchange procedures, such as by treatment of the zeolite X with calcium salts, such as, but not limited to, calcium chloride.
• ion exchange procedure with ion exchange preferably occurring after the zeolite adsorbent has been formed into its preferred final form, such as a bead or an extrudate.
• the zeolite X is ion exchanged to a level of at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably 85 to 95% of the exchangeable metal ions.
• the remaining ions may be sodium and/or potassium ions.
• the term "calcium exchanged zeolite X" means a zeolite X containing at least about 50% calcium cations.
• the calcium exchanged zeolite X of the invention generally contains sodium or potassium ions in addition to the calcium ions after the calcium ion exchange.
• sodium/potassium ions can be ion exchanged with other cations to enhance or modify the performance characteristics of the calcium exchanged zeolite X, especially for sulfur adsorption.
• additional cations that may be ion exchanged onto the zeolite X to enhance its performance include zinc, cadmium, cobalt, nickel, copper, iron, manganese, silver, gold, scandium, lithium and combinations thereof.
• the percentage of ion exchange of these additional metal ions can range from as little as 1% up to 40% or so, depending upon the level of calcium exchange of the zeolite X.
• the particular metal ions that are ion exchanged onto the calcium exchanged zeolite depend on the particular sulfur compounds which are intended to be removed from the fuel cell fuel stream by the sequential sulfur adsorbent bed system of the invention.
• the calcium exchanged zeolite when utilized above as a sulfur adsorbent, has shown significant capability for the adsorption of various sulfur materials, particularly tetra hydro thiophene (THT) , di-methyl sulfide (DMS) , tertiary butyl mercaptan (TBM) and ethyl mercaptan (EM) .
• THT tetra hydro thiophene
• DMS di-methyl sulfide
• TBM tertiary butyl mercaptan
• EM ethyl mercaptan
• the sequential sulfur adsorbent bed system of the invention can be utilized at temperatures lower than normally utilized for conventional sulfur adsorption. While conventional chemical sulfur adsorbents require temperatures of the feed stream of at least 150 0 C to 400 0 C, the sequential sulfur adsorbent bed system of the invention can be utilized effectively to adsorb the sulfur contaminants at temperatures below 100 0 C and is effective for removal of some sulfur compounds at temperatures as low as ambient temperatures. Further, because of the lower temperature of use, the sequential sulfur adsorption bed is easier to use than when higher temperatures are necessary.
• the pressure on the feed stream may be reduced to a range as low as from 1 bar to 18 bar, preferably from 1.7 bar to 7 bar, pressures lower than normally used for adsorption of sulfur compounds in a conventional fuel cell processing train.
• the inventors have also discovered a method for supplying a substantially desulfurized hydrocarbon fuel stream to a fuel cell processor using the sequential sulfur adsorbent bed system described above. In this process a sulfur contaminated hydrocarbon fuel stream is passed over or through the sequential sulfur adsorbent bed system of a fuel cell processor of the invention at a temperature from about ambient to 100 0 C, preferably less than 60 0 C, and more preferably at ambient temperatures.
• a hydrocarbon fuel stream comprising, for example, natural gas, propane or LPG, containing sulfur components at levels up to 500 ppm
• a substantial reduction in the quantity of those sulfur compounds preferably down to a level of less than about 50 ppb, can be achieved.
• the inventors have also discovered that the above- described sequential sulfur adsorbent bed system of the invention can be used in a desulfurizer, particularly for use in a fuel cell processing train.
• This desulfurizer includes an inlet for receiving the nondesulfurized hydrocarbon fuel stream, such as natural gas, propane or LPG, the sequential sulfur adsorbent bed system of the invention, as described above, which is placed in a location to desulfurize the hydrocarbon fuel stream, and an outlet where the desulfurized hydrocarbon fuel stream is passed down stream for further processing.
• the desulfurized hydrocarbon fuel stream can be passed through the fuel cell processing train to the fuel cell stack for the production of electricity.
• this method for supplying a substantially desulfurized hydrocarbon fuel stream is more advantageous than conventional desulfurization systems as it permits desulfurization of a broader range of sulfur compounds, increases the breakthrough time for the system, reduces the production of synthesized sulfur compounds, reduces the required temperature and pressure of the feed stream and permits the choice of different combinations and quantities of selective sulfur adsorbents to be used in the sequential sulfur adsorbent bed system depending on the sulfur compounds that are present in the particular feed stream.
• the compositions and methods of the invention also permit the production of a substantially desulfurized hydrocarbon fuel stream to levels of sulfur below those of conventional desulfurizing processes.
• the inventors have also discovered that the sequential sulfur adsorbent bed system of the invention can be used in fuel cell processors for a longer period of time than conventional adsorbents and still achieve high levels of sulfur absorbency.
• a synthetic natural gas feed stream comprising 93% methane, 3% ethane, 2% propane, 0.2% butane, 1% carbon dioxide and 0.75% nitrogen.
• 10 ppm as sulfur
• itiercaptan tert-butyl mercaptan or ethyl mercaptan
• THT tetra hydro thiophene
• the quantity of the adsorbents is 7.5 cc of the zeolite sulfur adsorbent, as described in Example 1, and 2.5 cc of the selective sulfur adsorbent, as described in Example 2.
• the zeolite adsorbent is in the form of 2 mm spheres.
• the selective sulfur adsorbent is a 1.18 mm x 0.85 mm mesh particulate typically produced from 1.6 mm extrudates by grinding.
• the adsorbents are sized and loaded into the reactor and the synthetic natural gas feed stream is passed through the reactor. The temperature of the feed stream is maintained at 38°C with a space velocity of 1500 hr "1 at a pressure of 2 bar.
• “Breakthrough” for this test occurs when greater than 50 ppb of sulfur is observed in the natural gas feed stream after passage through the adsorbent bed.
• analysis was performed using an Agilent 6890 gas chromatograph attached to an Antek 7090 sulfur analyzer.
• the gas chromatograph utilizes a 60 m X 320 micron DB-I capillary column for sulfur compound separation.
• the Antek 7090 utilizes a sulfur chemiluminescense detector (SCD) for sulfur detection.
• SCD sulfur chemiluminescense detector
• the operational detection limit for the system is approximately 50 ppb (mole) .
• the test unit is controlled by automation software.
• Example 1 The synthetic natural gas containing mercaptan and THT is passed through a reactor containing only calcium exchanged zeolite X.
• the zeolite X has an Si:Al equivalent ratio of 1.17 and a calcium exchange of 70% with the remaining metal ions comprising sodium and/or potassium.
• the temperature of the reactor is maintained at 38 0 C and the pressure is maintained at about 2 bar.
• the sulfur adsorbency of the calcium exchanged zeolite is shown in Figure 1, which shows a first breakthrough for the mercaptan at 268 hours.
• Example 2 Example 2
• the synthetic natural gas containing mercaptan and THT is passed through a reactor containing only a selective sulfur adsorbent comprising 34% by weight manganese compounds, 54% iron oxide comprising Fe 2 U3 and 12% alumina with a surface area of 294 m 2 /g.
• the performance of this selective sulfur adsorbent is shown in Figure 2, wherein the first breakthrough occurs at less than 25 hours.
• the sulfur compound(s) that is produced at that time is a "synthesized sulfur compound" as the breakthrough for THT does not occur until after 100 hours. It is believed that the "synthesized sulfur compounds" is at least one higher molecular weight sulfur compound produced from the interaction of the THT and/or the mercaptan with the selective sulfur adsorbent.
• Example 3 A further test was run wherein the calcium exchanged zeolite of Example 1 is used in combination with the selective sulfur adsorbent of Example 2 in the reactor. Seventy-five percent of the sulfur adsorbents by volume comprised the zeolite and 25% comprised the selective sulfur adsorbent. 10 ccs of the combined adsorbents are used. The zeolite was placed ahead of the selective sulfur adsorbent in the reactor. Otherwise, the operating conditions and the composition of the feed stream are the same as for Examples 1 and 2. When the feed stream is passed through the reactor, breakthrough does not occur until 496 hours as shown in Figure 3.
• the combination of the calcium exchanged zeolite with the selective sulfur adsorbent increases the time of sulfur breakthrough, prevents the formation of synthesized sulfur compounds and extends the lifetime of the sequential sulfur adsorbent bed system.

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