Simultaneous Removal of COS and H_2S at Low Temperatures over Nanoparticle a-FeOOH Based Catalysts

Catalysts using a-FeOOH nanoparticles as the active ingredient were tested by a microreactor-chromatography assessing apparatus at atmospheric pressure between 25 and 60C with a gas hourly space velocity of 10,000 h-1, while the removal performance of H2S with catalysts was investigated using the thermal gravimetric method. The results show that the catalysts are highly active for COS hydrolysis at low temperatures (<60C) and high gas hourly space velocity, and the highest activity can reach 100%. The catalyst is particularly stable for 12 h, and no deactivation is observed. Nanoparticle a-FeOOH prepared using hydrated iron sulfate shows higher COS hydrolysis activity, and the optimum calcination temperature for the catalyst is 260C. In addition, the catalysts can remove COS and H2S simultaneously, and 60C is favorable for the removal of H2S. The compensation effect exists in nanoparticle-based catalysts.     

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over AlzO3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon(CAC) catalysts loaded by Al2O3were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide(COS) and carbon disulfide(CS2) at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2concentration, gas hourly space velocity(GHSV) and relative humidity(RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3calcined at 300 ℃ had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2decrease. A small amount of O2introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.     

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al2O3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon(CAC) catalysts loaded by Al2O3were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide(COS) and carbon disulfide(CS2) at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2concentration, gas hourly space velocity(GHSV) and relative humidity(RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3calcined at 300 ℃ had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2decrease. A small amount of O2introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.     

一氧化碳中选择氧化除氢催化剂的研究

Several supported Pd catalysts were prepared and their catalytic activity for selective oxidation of hydrogen was studied. The results show that the variety of the supports has great effect on the catalytic activity. The space velocity and the Pd loading show also certain influence. The most active catalyst Pd/C A can selectively remove H 2 at 170～200℃ and 1?800 h -1 from a feed gas consisting of H 2 (0 197%), O 2 (0 103%), CO (40%) and N 2 (balance). When CO content in the feed gas increases to 78%, the activity of the catalyst only decreases a little, indicating that the results obtained here seems applicable to the removal of H 2 from pure CO.     

Effect of diluent and reaction parameter on selective oxidation of propane over MoVTeNb catalyst using nanoflow catalytic reactor

The selective oxidation of propane to acrylic acid over an MoVTeNb mixed oxide catalyst, dried and calcined before reaction has been studied using high-throughput instrumentation, which is called nanoflow catalytic reactor. The effects of catalyst dilution on the catalytic performance of the MoVTeNb mixed oxide catalyst in selective oxidation of propane to acrylic acid were also investigated. The effects of some reaction parameters, such as gas hourly space velocity （GHSV） and reaction temperature, for selective oxidation of propane to acrylic acid over diluted MoVTeNb catalyst have also been studied. The configuration of the nanoflow is shown to be suitable for screen catalytic performance, and its operating conditions were mimicked closely to conventional laboratory as well as to industrial conditions. The results obtained provided very good reproducibility and it showed that preparation methods as well as reaction parameters can play significant roles in catalytic performance of these catalysts.     

CH4-CO2 reforming to syngas over Pt-CeO2-ZrO2/MgO catalysts: Modification of support using ion exchange resin method

Pt-CeO2-ZrO2/MgO (Pt-CZ/MgO) catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, BET, SEM, TEM, DTA-TG and CO2-TPD were used to characterize the catalysts. CH4-CO2 reforming to synthesis gas (syngas) was performed to test the catalytic behavior of the catalysts. The catalyst Pt-CZ/MgO-IE(D) prepared using ion exchange resin exhibits more regular structure, smaller and more unique particle sizes, and stronger basicity than the catalyst Pt-CZ/MgO prepared from commercial MgO. At 1073 K and atmospheric pressure, Pt-CZ/MgO-IE(D) catalyst has a higher activity and greater stability than Pt-CZ/MgO catalyst for CH4-CO2 reforming reaction at high gas hourly space velocity of 36000 mL/(g·h) with a stoichiometric feed of CH4 and CO2. Activity measurement and characterization results demonstrate that modification of the support using ion exchange resin method can promote the surface structural property and stability, therefore enhancing the activity and stability for CH4-CO2 reforming reaction.     

Performance and characterization of iron-nickel catalysts for light olefin production

A series of x (Fe, Ni)/Al2O3 catalysts (x = 2--12 wt%) were prepared using incipient wetness method and studied for the conversion of synthesis gas to light olefins. 6 wt%(Fe, Ni)/Al2O3 catalyst was found to be the optimal catalyst for the production of C2--C4 olefins. The effects of calcination behaviors and operational conditions on the catalytic performance of the optimal catalyst were investigated. The best operational conditions were molar feed ratio H2/CO = 2/1, T = 260 ℃, gas hourly space velocity (GHSV) = 2600 h-1 and the pressure of 3 bar. Characterizations of both precursors and catalysts were carried out using X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscopy (SEM), N2-adsorption-desorption measurement, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Novel Ni/CeO2-Al2O3 composite catalysts synthesized by one-step citric acid complex and their performance in catalytic partial oxidation of methane

A series of novel Ni/CeO2-Al2O3composite catalysts were synthesized by one-step citric acid complex method. The as-synthesized catalysts were characterized by N2physical adsorption/desorption, X-ray diffraction(XRD), Fourier transform infrared(FT-IR) spectroscopy, hydrogen temperature-programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and thermogravimetry analysis(TGA). The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity(GHSV) and inert gas dilution of N2on their performance of catalytic partial oxidation of methane(CPOM) were investigated. Catalytic activity test results show that the highest methane conversion(85%), the best selectivities to carbon monoxide(87%) and to hydrogen(95%), the excellent stability and perfect H2/CO ratio(2.0) can be obtained over Ni/CeO2-Al2O3with 8 wt% Ni content calcined at 700 ℃ under the reaction condition of 750 ℃, CH4/O2ratio of 2 : 1 and gas hourly space velocity of 12000 mL h-1 g-1. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area(～108 m2 g-1), small crystallite size, easy reducibility and low coking rate.     

Novel Ni/CeO2-Al2O3 composite catalysts synthesized by one-step citric acid complex and their performance in catalytic partial oxidation of methane

A series of novel Ni/CeO2-Al2O3composite catalysts were synthesized by one-step citric acid complex method. The as-synthesized catalysts were characterized by N2physical adsorption/desorption, X-ray diffraction(XRD), Fourier transform infrared(FT-IR) spectroscopy, hydrogen temperature-programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and thermogravimetry analysis(TGA). The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity(GHSV) and inert gas dilution of N2on their performance of catalytic partial oxidation of methane(CPOM) were investigated. Catalytic activity test results show that the highest methane conversion(85%), the best selectivities to carbon monoxide(87%) and to hydrogen(95%), the excellent stability and perfect H2/CO ratio(2.0) can be obtained over Ni/CeO2-Al2O3with 8 wt% Ni content calcined at 700 ℃ under the reaction condition of 750 ℃, CH4/O2ratio of 2 : 1 and gas hourly space velocity of 12000 mL h-1 g-1. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area(～108 m2 g-1), small crystallite size, easy reducibility and low coking rate.     

Influence of Gas Components on the Formation of Carbonyl Sulfide over Water-Gas Shift Catalyst B303Q

Water-gas shift reaction catalyst at lower temperature (200—400℃) may improve the conversion of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobalt-molybdenum/alumina catalyst for water-gas shift reaction. The influences of temperature, space velocity, and gas components on the formation of carbonyl sulfide over sulfided cobalt-molybdenum/alumina catalyst B303Q at 200—400℃were studied in a tubular fixed-bed quartz-glass reactor under simulated water-gas shift conditions. The experimental results showed that the yield of carbonyl sulfide over B303Q catalyst reached a maximum at 220℃with the increase in temperature, sharply decreased with the increase in space velocity and the content of water vapor, increased with the increase in the content of carbon monoxide and carbon dioxide, and its yield increased and then reached a stable value with the increase in the content of hydrogen and hydrogen sulfide. The formation mechanism of carbonyl sulfide over B303Q catalyst at 200—400℃was discussed on the basis of how these factors influence the formation of COS. The yield of carbonyl sulfide over B303Q catalyst at 200-400℃was the combined result of two reactions, that is, COS was first produced by the reaction of carbon monoxide with hydrogen sulfide, and then the as-produced COS was converted to hydrogen sulfide and carbon dioxide by hydrolysis. The mechanism of COS formation is assumed as follows: sulfur atoms in the Co9S8-MOS2/Al2O3 crystal lattice were easily removed and formed carbonyl sulfide with CO, and then hydrogen sulfide in the water-gas shift gas reacted with the crystal lattice oxygen atoms in CoO-MoO3/Al2O3 to form Co9S8-MoS2/Al2O3. This mechanism for the formation of COS over water-gas shift catalyst B303Q is in accordance with the Mars-Van Krevelen's redox mechanism over metal sulfide.     

Influence of Reaction Conditions on Methanol Synthesis and WGS Reaction in the Syngas-to-DME Process

A series of CuO-ZnO catalysts (with different Cu/Zn molar ratios) were prepared, and evaluated under the reaction conditions of syngas-to-dimethyl ether (DME) with three sorts of feed gas and different space velocity. The catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The experiment results showed that the reaction conditions of syngas-to-DME process greatly affected the methanol synthesis and WGS reaction. The influence caused by Cu/Zn molar ratio was quite different on the two reactions; increasing of percentage of CO2 in feed gas was unfavorable for catalyst activity, and also inhibited both reactions: enhancement of reaction space velocity heavily influenced the performance of the catalyst, and the benefits were relatively less for methanol synthesis than for the WGS reaction.     

Effect of Ni Loading and Reaction Conditions on Partial Oxidation of Methane to Syngas

The partial oxidation of methane to synthesis gas is studied in this paper over Ni/Al2O3 catalysts under atmospheric pressure. The effects of Ni loading on the activity and stability of catalysts with 5 mm α-Al2O3 and θ-Al2O3 pellets as supports were measured in a continuous fixed bed reactor. It is found that the optimum Ni loading is 10%. And the effect of reaction conditions on partial oxidation of methane is also studied. The methane conversion and CO selectivity increase with the increase of the reaction temperature and the space velocity on 10%Ni/α-Al2O3 catalysts. The best CH4/O2 mole ratio is 2 for CO selectivity, and the optimum space velocity is 5.4x105 h-1.     

温度和剂油比对汽油催化裂化脱硫的影响

Increasingly stringent regulations on environmental protection make gasoline desulfurization be a major concern for the present refineries. Accordingly, we proposed an original idea of sulfur reduction by catalytic cracking of FCC gasoline and simultaneously converting most sulfur of sulfides to H 2S. Some progress has been made in exploitation of the catalysts. In this paper, the effect of temperature and catalyst/oil ratio on the FCC gasoline desulfurization over two catalyst samples via catalytic cracking was discussed. The optimum temperature range is 400～420 ℃ for sulfur removal with relatively low cracking loss of gasoline. The highest sulfur removal percentage of 70% can be achieved with a liquid yield of more than 96%. The catalyst samples have higher desulfurization activity and selectivity for the sulfide cracking. In addition, both the gasoline yield and the sulfur content of the desulfurized gasoline decrease with the catalyst/oil ratio.     

Characterization and catalytic performance of CeO2-Co/SiO2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.     

Development of Cu foam-based Ni catalyst for solar thermal reforming of methane with carbon dioxide

Using solar energy to produce syngas via the endothermic reforming of methane has been extensively investigated at the laboratory- and pilot plant-scales as a promising method of storing solar energy. One of the challenges to scaling up this process in a tubular reformer is to improve the reactor's performance, which is limited by mass and heat transfer issues. High thermal conductivity Cu foam was therefore used as a substrate to improve the catalyst's thermal conductivity during solar reforming. We also developed a method to coat the foam with the catalytically active component NiMg_3AlO_x. The Cu foam-based NiMg_3AlO_x performs better than catalysts supported on SiSiC foam, which is currently used as a substrate for solar-reforming catalysts, at high gas hourly space velocity(≥400,000 mL/(g·h)) or at low reaction temperatures(≤ 720 °C). The presence of a γ-Al_2O_3 intermediate layer improves the adhesion between the catalyst and substrate as well as the catalytic activity.     

Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method. The catalysts were characterized by N2 physisorption, XRD, TPR, SEM and TEM. Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor. It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume, but decrease NiO crystallite size, leading to higher activity and stability. The effects of reaction temperature, pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied. High carbon oxides conversion, CH4 selectivity and formation rate were achieved at the reaction temperature range of 280 300℃.     

Influence of Pretreatment on the Interaction of Oxygen with Silver and the Catalytic Activity of Ag／SiO2 Catalysts for CO Selective Oxidation in H2

The interactions of oxygen with pre~reduced silver catalysts as well as their catalytic propertiesfor CO selective oxidation in H2 after oxygen pre-treatment are studied in this paper. It is found that the pretreatment exerts a strong influence on the activity and selectivity of the silver catalyst. A drop in activity and selectivity is observed after treating a pre-reduced catalyst with oxygen at low temperatures,whereas a converse result is obtained after an oxidizing treatment at high temperatures (T≥350℃). O2-TPD results show that surface oxygen species adsorbs on silver surface after the oxygen treatment at low temperatures. However, penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile the surface oxygen species disappear. No other silver species except metallic silver are observed on all the catalysts by XRD, and the size of silver particle is not changed after the treatment with oxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also be removed by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorption and diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing the decrease in CO oxidation activity, in other words, it is important to obtain a clean silver surface for increasing the catalyst activity in CO removal from H2-rich feed gas. The differences in activity and selectivity due to the oxygen pretreatment at different temperatures axe discussed in terms of the changes in the surface/subsurface oxygen species of the silver particles.     

Preferential Oxidation of CO in Excess Hydrogen over CuO-CeO2 Catalyst Prepared by Chelating Method

The CuO-CeO2 catalyst prepared by chelating method has a superior catalytic performance for the preferential oxidation of CO in rich hydrogen, compared with the CuO-CeO2 catalyst prepared by coprecipitation method. The CO conversions over these catalysts, at 120℃and 120000 ml/(g-h) in the absence of CO2 and H2O, are 99.6% and 88.6%, respectively, and the selectivity of O2 over these catalysts is very close (i.e. 51.3% and 55.8%, respectively). The influence of certain factors such as hydrogen concentration, carbon monoxide concentration, H2O, O2/CO ratios, and space velocity on the catalytic performance of CuO-CeO2 catalyst prepared by chelating method is also studied. The results show that the addition of hydrogen and H2O has a negative effect on the catalytic performance of CuO-CeO2 catalyst, however, the variation of space velocity and the O2/CO ratio causes a comparatively slight influence.     

Selective Oxidation of Isobutane over NH4CsFePVMoAs Heteropolycompound Catalysts

A series of NH4Cs1.5Fe0.08HxPVMo11AsαOy heteropolycompound catalysts for the selective oxidation of isobutane, having Keggin structure, were synthesized by using co-precipitation method. The catalysts were characterized by FT-IR, H2-TPR, TG-DTA, SEM and XRD. Effects of the As content,reaction time, reaction temperature and molar ratio of isobutane to oxygen in feedstock on the activity and selectivity of the catalyst were investigated. The activation energy of the catalysts was measured by kinetics researches. Results showed the introduction of Cs^ into the catalysts shortened the stable period of them and enhanced their catalytic activity for the selective oxidation of isobutane. The highest conversion of isobutane and the total selectivity to liquid products were 18.6% and 81.2%, respectively,which were obtained at 380 *(3 with a space velocity of 975h^-1 over the NH4Cs1.5Fe0.08HxPVMo11 As0.3Oy heteropolycompound catalyst. It is confirmed that completely oxidized products were controlled well.     

Simultaneous recovery of carbon and sulfur resources from reduction of CO_2 with H_2S using catalysts

An approach to the simultaneous reclamation of carbon and sulfur resources from CO_2 and H_2S has been proposed and effectively implemented with the aid of catalysts. A brief thermodynamic study reveals the potential of direct reduction of CO_2 with H_2S(15:15 mol% balanced with N_2) for selective production of CO and elemental sulfur. The experiments carried out in a fixed-bed flow reactor over the temperature range of 400–800 °C give evidence of the importance of the employment of catalysts. Both the conversions of the reactants and the selectivities of the target products can be substantially promoted over most catalysts studied. Nevertheless, little difference appears among their catalytic performance. The results also prove that the presence of CO_2 can remarkably enhance H_2S conversion and the sulfur yield in comparison with H_2S direct decomposition. A longtime reaction test on Mg O catalyst manifests its superior durability at high temperature(700 °C) and huge gas hourly space velocity(100,000 h-1). Free radicals initiated by catalysts are supposed to dominate the reactions between CO_2 and H_2S.