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Hydrodesulfurization is a process whereby sulfur bound in organic compounds is removed as hydrogen sulfide, and is important to the control of sulfur dioxide emissions in the combustion of petroleum and coal fuels. It involves the...
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Hydrodesulfurization is a process whereby sulfur bound in organic compounds is removed as hydrogen sulfide, and is important to the control of sulfur dioxide emissions in the combustion of petroleum and coal fuels. It involves the cleavage of carbon sulfur bonds, and is catalyzed by layered disulfides such as molybdenum and tungsten disulfide. The simplest example is the reaction CH sub 3 SH + H sub 2 implies CH sub 4 + H sub 2 S. The mechanism of even this protypical reaction is unclear. In an effort to clarify it, the kinetics of methanethiol hydrodesulfurization over tungsten disulfide at low pressures was established, with partial pressures of methanethiol and hydrogen varied over a hundred fold. The kinetic order in each reactant was positive when its partial pressure was low negative when its partial pressure was high. The negative order in hydrogen had not been previously seen. The product gases, methane and hydrogen sulfide, each exhibited negative kinetic orders at high partial pressures, zero kinetic orders at low partial pressures. A dual site Langmuir-Hinshelwood type mechanism, which defines one active site as two adjacent edge sulfur vacancies and the second as a neighboring sulfur atom, describes these results quite well. Seventeen rare earth sulfides were surveyed for catalytic activity toward methanethiol hydrodesulfurization. These sulfides included both stoichiometric and nonstoichiometric compositions and four different morphologies. In general, nonconductors were inactive and conductors were active. This correlation extended to the nonstoichiometric gamma -phase sesquisulfides which exhibit both insulating and conducting properties. 96 refs. (ERA citation 10:031673)
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The effect of the ratio of hydrogen sulfide to quinoline on the HDN reaction has been explored in greater detail. Increasing the CS sub 2 /quinoline mole ratio to 2 caused a drop in total HDN activity from the maximum plateau leve...
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The effect of the ratio of hydrogen sulfide to quinoline on the HDN reaction has been explored in greater detail. Increasing the CS sub 2 /quinoline mole ratio to 2 caused a drop in total HDN activity from the maximum plateau level observed at a ratio of about 0.5. Throughout, an increase in this ratio causes a continuous enhancement of the hydrogenolysis reactions and inhibition of hydrogenation reactions in the reaction network. A large amount of kinetic data have been taken using quinoline, BzTHQ (5,6,7,8-tetrahydroquinoline) and orthopropylaniline as a feed with various partial pressures of hydrogen sulifde present. The computer modelling of these kinetic data is still underway. The catalytic activity for HDN reaction was found to increase with increased partial pressure of hydrogen sulfide during the initial sulfiding and resulfiding procedures. The effects of hydrogen sulfide to quinoline ratio on HDN and the increase in catalytic activity with pressure of hydrogen sulfide in the sulfiding procedure both suggest that the mechanism whereby hydrogen sulfide affects the HDN reaction is due to the formation of nonstoichiometric (excess) sulfur which is weakly bonded to the surface of the sulfided catalyst. (ERA citation 07:021118)
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Summary. H2S may play a role in mitigating onset of acute rejection in porcine VCA model in the absence of immunosuppression. Potential use for graft preservation strategies in a clinical setting that may require prolonged ischemic periods.
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A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse thro...
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A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatings appeared relatively stable in air and in a simple simulated gasification atmosphere at elevated temperature. Because the electron-beam coating instrument suffered irreparable breakdown, several alternative methods were tested in an effort to produce a nitrogen-impermeable, hydrogen-permeable membrane on porous sintered steel substrates. None of the preparation methods proved successful in sealing the porous substrate against nitrogen gas. To provide a nitrogen-impermeable ZnS material to test for hydrogen permeability, two ZnS infrared sample windows were purchased. These relatively thick ''membranes'' did not show measurable permeation of hydrogen, either due to lack of absorption or a negligible permeation rate due to their thickness. To determine if hydrogen was indeed adsorbed, thermogravimetric and differential thermal analyses tests were performed on samples of ZnS powder. A significant uptake of hydrogen gas occurred, corresponding to a maximum of 1 mole H{sub 2} per 1 mole ZnS at a temperature of 175 C. The hydrogen remained in the material at ambient temperature in a hydrogen atmosphere, but approximately 50% would be removed in argon. Reheating in a hydrogen atmosphere resulted in no additional hydrogen uptake. Differential scanning calorimetry indicated that the hydrogen uptake was probably due to the formation of a zinc-sulfur-hydrogen species resulting in the formation of hydrogen sulfide. The zinc sulfide was found to be unstable above approximately 200 C, probably with the reduction to metallic zinc with the evolution of hydrogen sulfide. The work has shown that ZnS is not a viable candidate for a high-temperature hydrogen separation membrane.
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We present data that allow us to make a careful comparison between fundamental reaction kinetics and observations of the ''time dependence'' of iron sulfidation. These data are weight gain measurements, microstructural observation...
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We present data that allow us to make a careful comparison between fundamental reaction kinetics and observations of the ''time dependence'' of iron sulfidation. These data are weight gain measurements, microstructural observations, and specimen geometry studies for iron reacting with sulfur vapor that has come either from H sub 2 /H sub 2 S mixtures or from pure sulfur vapor. We can report three facts: (a) the fundamental reaction of iron to iron sulfide is parabolic at high temperatures (550 to 800 deg C, 10 sup -3 to 10 sup 2 Pa); (b) the absolute reaction rate is the same whether the reaction occurs in pure sulfur vapor or in H sub 2 /H sub 2 S mixtures; and (c) weight gain measurements cannot be systematically corrected to ''parabolic'' rates using specimen or area correction arguments. (ERA citation 11:036251)
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Experimental results, which elucidate the factors which govern the equilibrium distribution of sulfur between organic sulfur in char and gaseous hydrogen sulfide, are presented. These experiments were conducted at between 1200 and...
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Experimental results, which elucidate the factors which govern the equilibrium distribution of sulfur between organic sulfur in char and gaseous hydrogen sulfide, are presented. These experiments were conducted at between 1200 and 1600 exp 0 F, for values of the ratio (P/sub H sub 2 S//P/sub H sub 2 /) ranging from 1 to 100, atmospheric pressure and for several chars. The rank of the parent coals from which these chars were derived ranged from lignite to anthracite. It is shown that the partial pressure ratio (P/sub H sub 2 S//P/sub H sub 2 /) is the pressure-dependent parameter which governs the extent of char sulfidation. It is also shown that the extent of char sulfidation is not uniquely dependent upon char surface area, but decreases with increasing rank of the char, and the rank of the coal from which the char is derived. Char sulfidation is shown to be a reversible process. The kinetics of char desulfurization are shown to be a function of the physiochemical history of the char - i.e., char desulfurization is a path-dependent process. The analogy between the chemistries of oxygen and sulfur in char are explored, and the implications for coal sulfur management are outlined. (ERA citation 05:005228)
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The objective of this program is to develop an economical progress for hydrogen production, with no additional carbon dioxide emission, through the thermal decomposition of hydrogen sulfide (H2S) in H2S-rich waste streams to high-...
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The objective of this program is to develop an economical progress for hydrogen production, with no additional carbon dioxide emission, through the thermal decomposition of hydrogen sulfide (H2S) in H2S-rich waste streams to high-purity hydrogen and elemental sulfur. The novel feature of the process being developed is the superadiabatic combustion (SAC) of part of the H2S in the waste stream to provide the thermal energy required for the decomposition reaction such that no additional energy is required. The program is divided into two phases. In Phase 1, detailed thermochemical and kinetic modeling of the SAC reactor with H2S-rich fuel gas and air/enriched air feeds is undertaken to evaluate the effects of operating conditions on exit gas products and conversion efficiency, and to identify key process parameters. Preliminary modeling results are used as a basis to conduct a thorough evaluation of SAC process design options, including reactor configuration, operating conditions, and product/by-product separation schemes, with respect to potential product yields, thermal efficiency, capital and operating costs, and reliability, ultimately leading to the preparation of a design package and cost estimate for a bench-scale reactor testing system to be assembled and tested in Phase 2 of the program. A detailed parametric testing plan was also developed for process design optimization and model verification in Phase 2. During Phase 2 of this program, IGT, UIC, and industry advisors UOP and BP Amoco will validate the SAC concept through construction of the bench-scale unit and parametric testing. The computer model developed in Phase 2 will be updated with the experimental data and used in future scale-up efforts. The process design will be refined and the cost estimate updated. Market survey and assessment will continue so that a commercial demonstration project can be identified.
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摘要 :
The objective of this program is to develop an economical progress for hydrogenproduction, with no additional carbon dioxide emission, through the thermal decomposition of hydrogen sulfide (H2S) in H2S-rich waste streams to high-p...
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The objective of this program is to develop an economical progress for hydrogenproduction, with no additional carbon dioxide emission, through the thermal decomposition of hydrogen sulfide (H2S) in H2S-rich waste streams to high-purity hydrogen and elemental sulfur. The novel feature of the process being developed is the superadiabatic combustion (SAC) of part of the H2S in the waste stream to provide the thermal energy required for the decomposition reaction such that no additional energy is required. The program is divided into two phases. In Phase 1, detailed thermochemical and kinetic modeling of the SAC reactor with H2S-rich fuel gas and air/enriched air feeds is undertaken to evaluate the effects of operating conditions on exit gas products and conversion efficiency, and to identify key process parameters. Preliminary modeling results are used as a basis to conduct a thorough evaluation of SAC process design options, including reactor configuration, operating conditions, and product/by-product separation schemes, with respect to potential product yields, thermal efficiency, capital and operating costs, and reliability, ultimately leading to the preparation of a design package and cost estimate for a bench-scale reactor testing system to be assembled and tested in Phase 2 of the program. A detailed parametric testing plan was also developed for process design optimization and model verification in Phase 2. During Phase 2 of this program, IGT, UIC, and industry advisors UOP and BP Amoco will validate the SAC concept through construction of the bench-scale unit and parametric testing. The computer model developed in Phase 2 will be updated with the experimental data and used in future scale-up efforts. The process design will be refined and the cost estimate updated. Market survey and assessment will continue so that a commercial demonstration project can be identified.
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A series of reduced molybdenum sulfides known as Chevrel phases were used as catalysts for thiophene hydrodesulfurization and were determined to have desulfurization activities comparable to model molybdenum sulfide catalysts. Cob...
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A series of reduced molybdenum sulfides known as Chevrel phases were used as catalysts for thiophene hydrodesulfurization and were determined to have desulfurization activities comparable to model molybdenum sulfide catalysts. Cobalt, iron, copper, and holmium ternary compounds were prepared with unusual promotional activity for holmium and copper. Hydrogenation and cracking activities of all Chevrel phase catalysts were observed to be very low. Characterization by x-ray diffraction, laser Raman spectroscopy, and XPS demonstrated that the catalysts were stable under reaction conditions. Oxidation states for molybdenum less than that for MoS sub 2 were detected. (ERA citation 09:033821)
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