Showing papers on "Syngas published in 2004"

Atomic-scale imaging of carbon nanofibre growth

Abstract: The synthesis of carbon nanotubes with predefined structure and functionality plays a central role in the field of nanotechnology1,2, whereas the inhibition of carbon growth is needed to prevent a breakdown of industrial catalysts for hydrogen and synthesis gas production3. The growth of carbon nanotubes and nanofibres has therefore been widely studied4,5,6,7,8,9,10. Recent advances in in situ techniques now open up the possibility of studying gas–solid interactions at the atomic level11,12. Here we present time-resolved, high-resolution in situ transmission electron microscope observations of the formation of carbon nanofibres from methane decomposition over supported nickel nanocrystals. Carbon nanofibres are observed to develop through a reaction-induced reshaping of the nickel nanocrystals. Specifically, the nucleation and growth of graphene layers are found to be assisted by a dynamic formation and restructuring of mono-atomic step edges at the nickel surface. Density-functional theory calculations indicate that the observations are consistent with a growth mechanism involving surface diffusion of carbon and nickel atoms. The finding that metallic step edges act as spatiotemporal dynamic growth sites may be important for understanding other types of catalytic reactions and nanomaterial syntheses.

Adsorption Equilibrium of Methane, Carbon Dioxide, and Nitrogen on Zeolite 13X at High Pressures

Abstract: High-pressure adsorption of methane, carbon dioxide, and nitrogen on zeolite 13X was measured in the pressure range (0 to 5) MPa at (298, 308, and 323) K and fitted with the Toth and multisite Langmuir models. Isosteric heats of adsorption were (12.8, 15.3, and 37.2) kJ/mol for nitrogen, methane, and carbon dioxide respectively, which indicate a very strong adsorption of carbon dioxide. The preferential adsorption capacity of CO2 on zeolite 13X was much higher than for the other gases, indicating that zeolite 13X can be used for methane purification from natural gas or for carbon dioxide sequestration from flue gas.

Catalytic Conversion of Methane to Synthesis Gas by Partial Oxidation and CO2 Reforming

Abstract: The preparation of synthesis gas from natural gas, which is the most important step in the gas-to-liquid transformation, has attracted increasing attention in the last decade. Steam reforming, partial oxidation, and CO 2 reforming are the three major processes that can be employed to prepare synthesis gas. Because steam reforming was reviewed recently in this series [Adv. Catal. 47 (2002) 65], this chapter deals only with the latter two processes. The history of the development of methane conversion to synthesis gas is summarized as an introduction to the partial oxidation of methane, which is reviewed with emphasis on hot spots in reactors, major developments in the reduction of O 2 separation costs, and reaction mechanisms. The various catalysts employed in CO 2 reforming are examined, with emphasis on inhibition of carbon deposition.

Fermentation of biomass-generated producer gas to ethanol.

Abstract: The development of low-cost, sustainable, and renewable energy sources has been a major focus since the 1970s. Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The demonstration of the fermentation of biomass-generated producer gas to ethanol is the major focus of this article in addition to assessing the effects of producer gas on the fermentation process. In this work, producer gas (primarily CO, CO(2), CH(4), H(2), and N(2)) was generated from switchgrass via gasification. The fluidized-bed gasifier generated gas with a composition of 56.8% N(2), 14.7% CO, 16.5% CO(2), 4.4% H(2), and 4.2% CH(4). The producer gas was utilized in a 4-L bioreactor to generate ethanol and other products via fermentation using a novel clostridial bacterium. The effects of biomass-generated producer gas on cell concentration, hydrogen uptake, and acid/alcohol production are shown in comparison with "clean" bottled gases of similar compositions for CO, CO(2), and H(2). The successful implementation of generating producer gas from biomass and then fermenting the producer gas to ethanol was demonstrated. Several key findings following the introduction of producer gas included: (1) the cells stopped growing but were still viable, (2) ethanol was primarily produced once the cells stopped growing (ethanol is nongrowth associated), (3) H(2) utilization stopped, and (4) cells began growing again if "clean" bottled gases were introduced following exposure to the producer gas.

Introduction to Fischer-Tropsch Technology

Abstract: Publisher Summary This chapter describes the practical application of fischer-tropsch (FT) technology It is the means by which synthesis gas containing hydrogen and carbon monoxide is converted to hydrocarbon products The hydrocarbon products are mostly liquid at ambient conditions but some are gaseous and some may even be solid For the above definition, the term “hydrocarbons” includes oxygenated hydrocarbons, such as alcohols However, the sole production of an oxygenated hydrocarbon, such as methanol is excluded The chapter explores that interest in FT technology is increasing rapidly This is due to the recent improvements to the technology and the realization that it can be used to obtain value from stranded natural gas In other words, remotely located natural gas will be converted to liquid hydrocarbon products that can be sold in worldwide markets This is often referred to as the gas-to-liquids (GTL) industry The chapter also discusses the application of FT technology usually involves complex integration, it inevitably consists of three basic steps: synthesis gas preparation, FT synthesis, and product upgrading

DME synthesis from synthesis gas on the admixed catalysts of Cu/ZnO/Al2O3 and ZSM-5

Abstract: Na-ZSM-5 and H-ZSM-5 catalysts with three different Si/Al ratios were prepared to investigate methanol dehydration and direct DME synthesis. The acid strength of ZSM-5 increased with a decrease in the Si/Al ratios and methanol dehydration rate was maximized on H-ZSM-5(30) with the highest acid strength. The direct DME synthesis was conducted on the admixed catalysts of Cu/ZnO/Al 2 O 3 and ZSM-5. The optimized solid acid composition on the admixed catalysts with Na-ZSM-5 for maximizing CO conversion was lowered with a decrease in the Si/Al ratio. The experimental results show that the overall DME synthesis rate can be determined by the intrinsic methanol synthesis rate on the admixed catalysts with the compositions higher than the optimized one and the overall rate can be controlled by the methanol dehydration rate on the admixed catalysts with the composition lower than the optimized one.

Carbon dioxide reforming of methane over Ni incorporated into Ce–ZrO2 catalysts

Abstract: A co-precipitation/digestion method was employed in a single step to prepare Ni–Ce–ZrO 2 catalysts useful for carbon dioxide reforming of methane. The loading amount of Ni and the ratio of CeO 2 to ZrO 2 were systematically varied to optimize the co-precipitated Ni–Ce–ZrO 2 catalysts. The prepared catalysts were characterized by various physico-chemical characterization techniques such as XRD, BET surface area, hydrogen chemisorption, SEM, TPR and XPS. It was found that 15% Ni (w/w) co-precipitated with Ce 0.8 Zr 0.2 O 2 having cubic phase gave synthesis gas with CH 4 conversion more than 97% at 800 ° C and such activity was maintained without significant loss during the reaction for 100 h. On the contrary, Ni–Ce–ZrO 2 having tetragonal phase (Ce 0.2 Zr 0.8 O 2 ) or mixed phase (Ce 0.5 Zr 0.5 O 2 ) deactivated during the reaction due to carbon formation. The enhanced catalytic activity and stability of the co-precipitated Ni–Ce 0.8 Zr 0.2 O 2 catalyst is attributed to a combination of the nano-crystalline nature of cubic Ce 0.8 Zr 0.2 O 2 support and the finely dispersed nano-sized NiO x crystallites, resulting in the intimate contact between Ni and Ce 0.8 Zr 0.2 O 2 particles.

Carbon Dioxide Reforming of Methane Using DC Corona Discharge Plasma Reaction

Abstract: Carbon dioxide reforming of methane via dc corona discharge plasma reaction at atmospheric pressure has been investigated. The effects of the CH4/CO2 ratio in the feed, flow rate, discharge power, and corona types have been systematically studied. The results show that the molar ratio of H2 to CO in the products strong depends on the molar ratio of CH4 to CO2 in the feed. The discharge power, flow rate, and corona types have slight influence on the syngas composition. When the CH4/CO2 ratio is 1/2, the syngas of lower H2/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. The conversions of methane and carbon dioxide increase with increasing the discharge power and decrease with increasing the flow rate. The conversions of reactants via positive corona are generally higher than that via negative corona, but the ratio of H2/CO in the products is the other way round. Besides syngas and water, other products including various hydrocarbons and oxygenates ar...

Catalytic investigation for Fischer: Tropsch synthesis from bio-mass derived syngas

Abstract: Hydrocarbon synthesis from biomass-derived syngas (bio-syngas) has been investigated as a potential way to use biomass. The Fischer–Tropsch reaction has been carried out using CO/CO 2 /H 2 /Ar (11/32/52/5 vol.%) mixture as a model for bio-syngas on co-precipitated Fe/Cu/K, Fe/Cu/Si/K and Fe/Cu/Al/K catalysts in a fixed bed reactor. The reaction with the model bio-syngas showed that only CO was converted to hydrocarbons while, in the reaction with a balanced (i.e. H 2 -enriched) feed gas, CO 2 was converted to hydrocarbons as well as CO. In the optimization of the catalyst composition that employed bio-syngas, alumina as a structural promoter gave much higher activity for hydrocarbon production than silica. K addition promoted the catalytic activity and the selectivities toward olefins and long-chain hydrocarbons, but too high K promotion caused the gradual deactivation of the catalysts. Some performances of the catalysts that depended on the syngas composition are also presented.

Development of high performance Cu/ZnO-based catalysts for methanol synthesis and the water-gas shift reaction

Abstract: Our group’s studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO2 and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al2O3, ZrO2 or SiO2 improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO2 and H2 over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO2, but not via the hydrogenation of CO, and that H2O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as Cu/ZnO/ZrO2/Al2O3 and Cu/ZnO/ZrO2/Al2O3/Ga2O3 were highly active for methanol synthesis from CO2 and H2. The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO2 and H2. The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO2/Al2O3 catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H2 at high temperatures than that of the Cu/ZnO/Al2O3 catalyst. Accordingly, the Cu/ZnO/ZrO2/Al2O3 catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO2/Al2O3 catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO2 and H2.

Process for pyrolytic heat recovery enhanced with gasification of organic material

Abstract: This invention is a reactor and a process for the conversion of organic waste material such as municipal trash, sewage, post-consumer refuse, and biomass to commercially salable materials. The invention produces the following: 1. Maximum energy conversion from the organic material 2. High volume consumption of the organic feed material 3. Less pollution of gaseous products than prior art systems 4. Solid residuals for disposal are minimal and non-hazardous. The conversion is accomplished by combining anaerobic gasification and pyrolysis of the feed organic material and making it into synthetic gas. The synthetic gas is a mixture of hydrocarbons (CxHy), hydrogen, and carbon monoxide with small amounts of carbon dioxide and nitrogen. An essential feature of the invention is a hot driver gas, devoid of free oxygen and rich in water, which supplies the entire thermal and chemical energy needed for the reactions. This hot driver gas is produced by complete sub-stoichiometric combustion of the fuel (CxHy) before it enters the reactor . . .

The addition of HZSM-5 to the Fischer–Tropsch process for improved gasoline production

Abstract: The combination of an alkali-promoted iron-based Fischer–Tropsch catalyst and an acidic co-catalyst (HZSM-5) for syngas conversion to hydrocarbons was studied in a Berty microreactor. It was found that a physical mixture of the two catalysts resulted in severe alkali migration from the iron catalyst to the zeolite, so that this mode of the bifunctional process does not seem viable. However, by separating the catalytic layers by means of a wire mesh inside the microreactor, it was confirmed that the addition of HZSM-5 to the Fischer–Tropsch process improved both the selectivity and the quality of the gasoline product fraction. The deactivation behaviour of the acidic co-catalyst is also reported.

Gasification of different biomasses in a dual-bed gasifier system combined with novel catalysts with high energy efficiency

Abstract: Syngas has been produced from the gasification of various biomasses such as jute stick, bagasse, rice straw, and saw dust of cedar wood using a dual-bed gasifier combined with a novel catalyst The gasification conditions were 150 mg/min of biomass feeding, ER=025, catalyst (3 g) at temperature range of 823–923 K The carbon conversion to gas and yield of useful gases such as CO, H 2 , and CH 4 were dependent on the properties of biomass In terms of the formation rate of useful gases, the biomass quality was in the order of cedar wood > jute stick > bagasse > rice straw Although the rice straw gasification is comparatively difficult in a single-bed gasifier due to its high ash content (226%), it becomes possible in a dual-bed reactor system The dual-bed gasifier using Rh/CeO 2 /SiO 2 catalyst that has been developed gave higher conversion to gas and higher yield of CO+H 2 +CH 4 than did the single-bed gasifier In the case of cedar wood gasification, although a small amount of coke was formed on the catalyst surface, the tar was not formed at all even at 823 K However, in the case of other biomass, especially for rice straw, a significant amount of coke on the catalyst surface and tar was formed even at the high temperature (923 K)

Chapter 7 – FT catalysts

Abstract: Publisher Summary This chapter reviews that only the four group VIII metals, Fe, Co, Ni, and Ru have sufficiently high activities for the hydrogenation of carbon monoxide to warrant possible application in the fischer-tropsch (FT) synthesis. Of the four metals ruthenium is the most active, but its high cost and low availability rules it out for large scale application. Being a powerful hydrogenating catalyst it produces much more methane than Co or Fe catalysts. Nickel forms volatile carbonyls resulting in continuous loss of the metal at temperatures and pressures, at which practical FT plants operate. From the above, it is clear that only cobalt and iron based catalysts can be considered as practical FT catalysts. The chapter highlights that for the production of the high value linear alkenes, iron catalyst, operating at high temperatures in fluidized bed reactors remains the catalyst of choice. The LTFT iron catalyst may also find future applications for the conversion of coal-derived syngas.

Effect of MgO additive on catalytic properties of Co/SiO2 in the dry reforming of methane

Abstract: The dry reforming of methane to syngas was studied in the temperature range 500–800 °C on a series of Co/SiO2 catalysts modified by MgO (5–35 wt.%). The materials have been prepared by successive incipient wetness impregnation and characterised by BET, XRD, H2-TPR, CO2 adsorption and in situ-DRIFT. The formation of a silicate adlayer Mg2SiO4 is observed at high MgO content (30–35 wt.%), which corresponds to a much improved catalytic stability under the severe dry reforming conditions. This phase favours the development of small metallic cobalt particles, preventing their coalescence under reaction conditions. A bi-functional mechanism is proposed which combines the accumulation of oxidizing agents like carbonates and hydrogeno-carbonate adspecies on the catalyst support due to a medium basicity of the layer and the reactivity of small metal particles for methane activation. This concerted process tends to limit coke formation and therefore contribute to the observed catalytic stability.

Dry Reforming of Methane Using a Solar-Thermal Aerosol Flow Reactor

Abstract: Research has focused on dry reforming because it offers a sink for CO2 and relative to steam methane reforming produces a more desirable ratio of H2 to CO for feed to a Fischer−Tropsch synthesis process. To form synthesis gas by dry reforming in a rapid, environmentally benign manner, a fluid-wall aerosol flow reactor powered by concentrated sunlight has been designed. Operating with residence times on the order of 10 ms and temperatures of approximately 2000 K, CH4 and CO2 conversions of 70% and 65%, respectively, have been achieved in the absence of any added catalysts. Methane to carbon dioxide feed ratios greater than unity were fed in order to prevent reaction of CO2 with the graphite tube. The carbon black particles formed by reaction were amorphous carbon black with a primary particle size of approximately 20−40 nm.

Solar Gasification of Biomass: A Molten Salt Pyrolysis Study

Abstract: A novel solar process and reactor for thermochemical conversion of biomass to synthesisgas is described. The concept is based on dispersion of biomass particles in a molteninorganic salt medium and, simultaneously, absorbing, storing and transferring solarenergy needed to perform pyrolysis reactions in the high-temperature liquid phase. Alab-scale reactor filled with carbonates of potassium and sodium was set up to study thekinetics of fast pyrolysis and the characteristics of transient heat transfer for celluloseparticles (few millimeters size) introduced into the molten salt medium. The operatingconditions were reaction temperatures of 1073–1188 K and a particle peak-heating rateof 100 K/sec. The assessments performed for a commercial-scale solar reactor demon-strate that pyrolysis of biomass particles dispersed in a molten salt phase could be afeasible option for the continuous, round-the-clock production of syngas, using solarenergy only. @DOI: 10.1115/1.1753577#Keywords: Biomass, Pyrolysis, Molten salt, Kinetics, Solar reactor, Thermal storage

Cobalt supported on carbon nanofibers- a promising novel Fischer-Tropsch catalyst

Abstract: The potential of carbon nanofibers supported cobalt catalysts for the Fischer-Tropsch reaction is shown. Using the wet impregnation method cobalt on carbon nanofiber catalysts were prepared with cobalt loadings varying from 5 to 12 wt%. The cobalt particle size of the catalysts varied with increasing loading from 3 to 13 nm. Cobalt particles were localized both at the external and at the internal surface of the fibers. The activity at 1 bar syngas varied with increasing loading from 0.71 to 1.71 10−5 molco·gco−l·s−1. This might indicate that smaller particles are less active in the Fischer-Tropsch reaction, but may also be provoked by different fractions of cobalt present inside the fibers. Stable activity of 225 gCH2·1cat−1·h−1 for 400 h was obtained at pressures of 28–42 bar syngas. A C5+ selectivity of 86 wt% was found, which is remarkably high for an unpromoted catalyst.

Pressure swing reforming for fuel cell systems

Abstract: The present invention provides an improvement in the process of producing hydrogen from hydrocarbon-containing streams. A cyclic reforming process, referred to as pressure swing reforming, provides an efficient means for producing a hydrogen containing synthesis gas for fuel cell applications. Pressure swing reforming may be integrated with shift reactions, preferential oxidation, and membrane separation, achieving thermal and material efficiencies relative to conventional hydrogen production. In one embodiment, at least some synthesis gas which is first produced in the pressure swing reforming process is combusted with air to provide the heat for the regeneration step of the pressure swing reforming process.

Process and apparatus for the production of useful products from carbonaceous feedstock

Abstract: A carbonaceous feedstock to alcohol conversion process in which carbon dioxide is removed from the syngas stream issuing from a feedstock reformer, to yield a carbon dioxide depleted syngas stream including hydrogen, carbon monoxide and methane. This carbon dioxide depleted syngas stream is then passed through a Fischer-Tropsch reactor ultimately yielding a mixed alcohol product which is preferably largely ethanol. The removed carbon dioxide stream is passed through a methane reformer along with methane, which is produced in or has passed through a Fischer-Tropsch reactor, to yield primarily carbon monoxide and hydrogen. The carbon monoxide and hydrogen stream from the methane reformer are passed through the alcohol reactor. Also disclosed are a unique catalyst, a method for controlling the content of the syngas formed in the feedstock reformer, and a feedstock handling system.