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1.
D. Ferdous  J. Adjaye 《Fuel》2006,85(9):1286-1297
A detailed experimental study was performed in a trickle-bed reactor using bitumen derived gas oil. The objective of this work was to compare the activity of NiMo/Al2O3 catalyst containing boron or phosphorus for the hydrotreating and mild hydrocracking of bitumen derived gas oil. Experiments were performed at the temperature and LHSV of 340-420 °C and 0.5-2 h−1, respectively, using NiMo/Al2O3 catalysts containing 1.7 wt% boron or 2.7 wt% phosphorus. In the temperature range of 340-390 °C, higher nitrogen conversion was observed from boron containing catalyst than that from phosphorus containing catalyst whereas in the same temperature range, phosphorus containing catalyst gave higher relative removal of sulfur than boron containing catalyst. Phosphorus containing catalyst showed excellent hydrocracking and mild hydrocracking activities at all operating conditions. Higher naphtha yield and selectivity were obtained using phosphorus containing catalyst at all operating conditions. Maximum gasoline selectivity of ∼45 wt% was obtained at the temperature, pressure, and LHSV of 400 °C, 9.4 MPa and 0.5 h−1, respectively, using catalyst containing 2.7 wt% phosphorus.  相似文献   

2.
CuO-CoO-Cr2O3 mixed with MFI Zeolite (Si/Al = 35) prepared by co-precipitation was used for synthesis gas conversion to long chain hydrocarbon fuel. CuO-CoO-Cr2O3 catalyst was prepared by co-precipitation method using citric acid as complexant with physicochemical characterization by BET, TPR, TGA, XRD, H2-chemisorptions, SEM and TEM techniques. The conversion experiments were carried out in a fixed bed reactor, with different temperatures (225-325 °C), gas hourly space velocity (457 to 850 h−1) and pressure (28-38 atm). The key products of the reaction were analyzed by gas chromatography mass spectroscopy (GC-MS). Significantly high yields of liquid aromatic hydrocarbon products were obtained over this catalyst. Higher temperature and pressure favored the CO conversion and formation of these liquid (C5-C15) hydrocarbons. Higher selectivity of C5 + hydrocarbons observed at lower H2/CO ratio and GHSV of the feed gas. On the other hand high yields of methane resulted, with a decrease in C5+ to C11+ fractions at lower GHSV. Addition of MFI Zeolite (Si/Al = 35) to catalyst CuO-CoO-Cr2O3 resulted a high conversion of CO-hydrogenation, which may be due to its large surface area and small particle size creating more active sites. The homogeneity of various components was also helpful to enhance the synergistic effect of Co promoters.  相似文献   

3.
A novel plasma-treated Ni/MgO catalyst was prepared by treating coprecipitated NiCO3–MgCO3 with dielectric-barrier discharge plasma. The results by XRD, TEM and N2 adsorption analyses showed that the plasma-prepared Ni/MgO catalyst possessed smaller particle size, enhanced nickel dispersion, and higher specific surface area than a conventionally reduced Ni/MgO catalyst. The plasma-prepared Ni/MgO catalyst also exhibited better catalytic activity for carbon dioxide reforming of methane. More than 20% higher conversions of methane and carbon dioxide were obtained than those over the conventional Ni/MgO catalyst at 700 °C and a space velocity of 96,000 mL/(h?gcat).  相似文献   

4.
The performances of different promoters (CeO2, ZrO2 and Ce0.5Zr0.5O2 solid solution) modified Pd/SiC catalysts for methane combustion are studied. XRD and XPS results showed that Zr4+ could be incorporated into the CeO2 lattice to form Zr0.5Ce0.5O2 solid solution. The catalytic activities of Pd/CeO2/SiC and Pd/ZrO2/SiC are lower than that of Pd/Zr0.5Ce0.5O2/SiC. The Pd/Zr0.5Ce0.5O2/SiC catalyst can ignite the reaction at 240 °C and obtain a methane conversion of 100% at 340 °C, and keep 100% methane conversion after 10 reaction cycles. These results indicate that active metallic nanoparticles are well stabilized on the SiC surface while the promoters serve as oxygen reservoir and retain good redox properties.  相似文献   

5.
Atul Sharma  Kouichi Miura 《Fuel》2006,85(2):179-184
A novel Ni/carbon catalyst recently developed by the authors was used to gasify organic compounds dissolved in the wastewater with TOC concentration from 0.2 to 2%. The process removes the organic compounds by gasifying them into high calorific gases like methane and hydrogen. The investigations were focused on the efficiency of the Ni/carbon catalyst in terms of carbon conversion, conversion of big organic molecules, and catalyst deactivation due to sintering. The preliminary results showed that up to 99% carbon conversion can be achieved at 360 °C, and 20 MPa. A conversion mechanism was suggested which consists of: first, decomposition of big molecules to small molecules on the metal surface, steam gasification of small molecules to produce CO and H2 followed by CO methanation and CO shift reaction to produce CH4 and CO2. The catalyst was found to be highly active and stable and no sintering was observed even after 100 h of reaction time.  相似文献   

6.
Supported nickel catalysts with core/shell structures of Ni/Al2O3 and Ni/MgO-Al2O3 were synthesized under multi-bubble sonoluminescence (MBSL) conditions and tested for dry reforming of methane (DRM) to produce hydrogen and carbon monoxide. A supported Ni catalyst made of 10% Ni loading on Al2O3 and MgO-Al2O3, which performed best in the steam reforming of methane (97% methane conversion at 750 °C) and in the partial oxidation of methane (96% methane conversion at 800 °C), showed also good performance in DRM and excellent thermal stability for the first 150 h. The supported Ni catalysts Ni/Al2O3 and Ni/MgO-Al2O3 yielded methane conversions of 92% and 92.5%, respectively and CO2 conversions of 95.0% and 91.8%, respectively, at a reaction temperature of 800 °C with a molar ratio of CH4/CO2 = 1. Those were near thermodynamic equilibrium values.  相似文献   

7.
This paper reports the catalytic performance of a PtRu/ZrO2 catalyst modified with Na and Mg in an oxidative steam reforming of ethanol (OSRE) reaction tested in the temperature range of 300–400 °C. The results show that the PtRuMg1/ZrO2 catalyst requires higher temperatures (TR ~ 400 °C) to achieve complete conversion than either the PtRuNa1/ZrO2 or PtRu/ZrO2 catalysts (TR ~ 300 °C). Also, an apparent coke deposit is found on the PtRuMg1/ZrO2 catalyst. The preferential PtRuNa1/ZrO2 catalyst shows active at temperatures as low as 300 °C and produces less CO (< 0.2%) at temperatures lower than 340 °C.  相似文献   

8.
Ni modified K2CO3/MoS2 catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H2/CO (molar radio) = 2.0, GHSV = 3000 h 1, and P = 10.0 MPa. Compared with conventional K2CO3/MoS2 catalyst, Ni/K2CO3/MoS2 catalyst showed higher activity and higher selectivity to C2+OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K2CO3/MoS2 was higher, however, it was close to that of K2CO3/MoS2 catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K2CO3/MoS2 catalyst.  相似文献   

9.
The investigation of hydro-conversion behavior of the heavy intermediate products derived from coal direct liquefaction is advantageous to optimize the technological conditions of direct coal liquefaction and improve the oil yield. In this paper, the hydro-conversion of preasphaltenes catalyzed by SO42−/ZrO2 solid acid was investigated based on the structural characterization of preasphaltenes and its hydro-conversion products, and the determination of products distribution and the kinetics of preasphaltenes hydro-conversion. The results indicated that the content of condensed aromatic rings increased, and the contents of hydrogen, oxygen and aliphatic side chains of preasphaltenes decreased with the increase of coal liquefaction temperature. The preasphaltenes showed higher hydro-conversion reactivity while SO42−/ZrO2 solid acid was used as catalyst. Higher temperature and longer time were in favor of increasing the conversion and the oil + gas yield. The conversion of preasphaltenes hydro-conversion under 425 °C, for 40 min reached 81.3% with 51.2% oil + gas yield. SO42−/ZrO2 solid acid was in favor of the catalytic cracking rather than the catalytic hydrogenation in the hydro-conversion of preasphaltenes. The activation energy of preasphaltenes conversion into asphaltenes was 72 kJ/mol. The regressive reactions were only observed at a higher temperature.  相似文献   

10.
Supported nickel catalysts with a core/shell structure of Ni/Al2O3 and Ni/MgO-Al2O3 synthesized under multi-bubble sonoluminescence (MBSL) conditions were tested for mixed steam and dry (CO2) reforming and autothermal reforming of methane. In the previous tests, the supported Ni catalysts made of 10% Ni loading on Al2O3 or MgO-Al2O3 had shown good performances in the steam reforming of methane (methane conversion of 97% at 750 °C), in the partial oxidation of methane (methane conversion of 96% at 800 °C) and in dry reforming of methane (methane conversion of 96% at 850 °C) and showed high thermal stability for the first 50-150 h. In this study, the supported Ni catalysts showed good performance in the mixed and autothermal reforming of methane with their excellent thermal stability for the first 50 h. In addition, very interestingly, there was no appreciable carbon deposition on the surface of the tested catalysts after the reforming reaction.  相似文献   

11.
A. Evdou  L. Nalbandian 《Fuel》2010,89(6):1265-1273
This work reports on the preparation and characterization of perovskitic materials with the general formula La1−xSrxFeO3 (x = 0, 0.3, 0.7, 1) for application in a dense mixed conducting membrane reactor process for simultaneous production of synthesis gas and pure hydrogen. Thermogravimetric experiments indicated that the materials are able to loose and uptake reversibly oxygen from their lattice up to 0.2 oxygen atoms per “mole” for SrFeO3 with x = 1 at 1000 °C. The capability of the prepared powders to convert CH4 during the reduction step, in order to produce synthesis gas, as well as their capability to dissociate water during the oxidation step, in order to produce hydrogen were evaluated by pulse reaction experiments in a fixed bed pulse reactor. The high sintering temperatures (1100-1300 °C) required for the densification of the membrane materials result in decreased methane conversion and H2 yields during the reduction step compared to the corresponding values obtained with the perovskite powders calcined at 1000 °C. Addition of small quantities of NiO, by simple mechanical mixing, to the perovskites after their sintering at high temperatures, increases substantially both their methane decomposition reactivity, their selectivity towards CO and H2 and their water splitting activity. Maximum H2 yield during the reduction step is achieved with the La0.7Sr0.3FeO3 sample mixed with 5% NiO and is 80% of the theoretically expected H2, based on complete methane decomposition. In the oxidation - water splitting step, 912 μmol H2 per gr solid are produced with the La0.3Sr0.7FeO3 sample mixed with 5% NiO. The experimental results of this work can be equally well applied for the “chemical-looping reforming” process since they concern using the lattice oxygen of the perovskite oxides for methane partial oxidation to syngas, in the absence of molecular oxygen, and subsequent oxidation of the solid.  相似文献   

12.
Gary Jacobs 《Fuel》2003,82(10):1251-1260
Modeling of the supercritical fluid mixture indicated that an important increase in density occurs above a threshold of approximately 4 MPa for the reaction temperature of 220 °C studied. While transport parameters of the fluid are largely retained, the observed improvement in wax solubility was noteable.A cobalt catalyst (25%Co/γ-Al2O3) was used in a fixed bed reactor under a pressure/density tuned supercritical fluid mixture of n-pentane/n-hexane. By using inert gas as a balancing gas to maintain a constant pressure, the density of the supercritical fluid could be tuned near the supercritical point while maintaining constant space velocity within the reactor. The benefits of the mixture allowed for optimization of transport and solubility properties at an optimum reaction temperature for Fischer-Tropsch synthesis with a cobalt catalyst. Indeed, above 4 MPa, increases in wax yields from sampling and carefully controlled gas measurements using an internal standard demonstrated an important increase in conversion due to greater accessibility to active sites after extraction of heavy wax from the catalyst. Additional benefits included decreased methane and carbon dioxide selectivities. Decreased paraffin/(olefin+paraffin) selectivities with increasing carbon number were also observed, in line with extraction of the hydrocarbon from the pore. Faster diffusion rates of wax products resulted in lower residence times in the catalyst pores, and therefore, decreased probability for readsorption and reaction to the hydrogenated product. Even so, there was not an observable increase in the alpha value for higher carbon number products over that obtained with just the inert gas.  相似文献   

13.
A comprehensive kinetic model for oxidative coupling of methane (OCM) on Mn/Na2WO4/SiO2 catalyst was developed based on a microcatalytic reactor data. The methane conversion and ethylene, ethane, carbon monoxide and carbon dioxide selectivities were obtained in a wide range of operating conditions including 750 < < 875 °C, 4 < CH4/O2 < 7.5 and space time between 30 and 160 kg · s/m3 at = 657 mmHg. The reaction networks of five kinetic models with appropriate rate equation type were compared together. The kinetics rates parameters of each reaction network were estimated using genetic algorithm optimization method. After comparing the reaction networks, the reaction network presented by Stansch et al. was found to best represent the OCM reaction network and was further used in this work. This kinetic network considers both catalytic and gas-phase as well as primary and consecutive reaction steps to predict the performance of the OCM. Comparing the experimental and predicted data showed that presented model has a reasonable fit between the experimental data and the predicted values with average absolute relative deviation of ± 9.1%.  相似文献   

14.
O.C. Carneiro  R.T.K. Baker 《Carbon》2005,43(11):2389-2396
The growth of carbon nanofibers from Fe-Cu catalyzed decomposition of CO/C2H4/H2 mixtures at temperatures over the range 500-650 °C has been investigated. Based on analysis of the gas phase and solid products it is apparent that co-adsorption of CO and C2H4 induces major perturbations in the surfaces of the bimetallic catalyst particles. These features are reflected in an increase in the yield of solid carbon and subtle changes in the structural characteristics of the carbon nanofibers. Optimum performance with respect to the yield of carbon nanofibers is found for iron-rich particles treated in CO/C2H4/H2 (1:3:1) at 600 °C. Deactivation of the catalyst is observed to occur with high Cu concentrations and at reaction temperatures in excess of 600 °C. It is suggested that under these conditions the surface of the particles in contact with the reactant gas mixture become enriched in Cu, which does not possess the ability to dissociatively chemisorb either CO or C2H4.  相似文献   

15.
This paper presents the growth evolutions in terms of the structure, growth direction and density of rapid grown carbon nanotube (CNT) forests observed by scanning and transmission electron microcopies (SEM/TEM). A thermal CVD system at around 700 °C was used with a catalyst of Fe films deposited on thin alumina (Al2O3) supporting layers, a very fast raising time to the growth temperature below 25 °C/s, and a carbon source gas of acetylene diluted with hydrogen and nitrogen without water vapor. Activity of Fe catalyst nanoparticles was maintained for 5 min during CVD process, and it results in CNT forests with heights up to 0.6 mm. SEM images suggest that the disorder in CNT alignment at the initial stage of CNTs plays a critical role in the formation of continuous CNT growth. Also, the prolonged heating process leads to increased disorder in CNT alignment that may be due to the oxidation process occurring at the Fe nanoparticles. TEM images revealed that both double- and few-walled CNTs with diameters of 5-7 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. The number of experiments at the same conditions showed a very good repeatability and reproducibility of rapid grown CNT forests.  相似文献   

16.
Non conventional nickel (1%) and nickel (1%)-copper (0.2%-0.75%) catalysts supported on silica have been prepared by aqueous hydrazine reduction of nickel acetate at 70 °C. They were characterized by TEM, H2-adsorption, H2-TPD and tested in the gas phase hydrogenation of benzene at atmospheric pressure in the temperature range 75 °C-230 °C. The obtained results show that nickel is in a whisker-like shape or as a film of low density for the Ni/SiO2 and Ni-Cu/SiO2 catalysts respectively. Copper is in the shape of facetted particles in the mono or bimetallic systems with a mean particle size varying from 25 to 100 nm. The presence of copper decreased the nickel phase dispersion as well as the conversion whereas it increased carbon deposit in benzene hydrogenation. The results obtained are ascribed to nickel phase shape changes and Ni-Cu interactions. A kinetic reaction mechanism model is proposed. The comparative study of a pair of classical/non-classical Ni/SiO2 catalysts showed much higher surface and catalytic properties of the hydrazine catalyst.  相似文献   

17.
Methane and CO2 are the main components of biogas; therefore its direct conversion into a higher added value gas as syn-gas (mixture of CO and H2) is a very interesting alternative for the valorisation of such renewable resource. In this work, firstly a thermodynamic analysis of the decomposition of CH4:CO2 mixtures at different temperatures and CH4:CO2 ratios simulating the biogas composition, has been carried out. Secondly, the decomposition of a mixture with a molar ratio of 1:1 has been studied in a fixed-bed reactor by using a Ni/Al2O3 based catalyst, at the temperature range in which according to the thermodynamic study, carbon formation is favoured. Results obtained have been compared to those of methane decomposition carried out under the same experimental conditions. Co-feeding of CO2 and CH4 avoids catalyst deactivation substantially, allowing to obtain a syn-gas with H2:CO ratio close to 1. Moreover, the carbon obtained from mixtures of CH4 and CO2 is deposited as fishbone carbon nanofibres at 600 °C and ribbon carbon nanofibers at 700 °C, both being materials with high added value which can be used in multiple applications.  相似文献   

18.
Rh, Pt, and Pt-Rh catalysts on modified commercial zirconia support (m-ZrO2) were screened for the clean-up of gasification gas from tar, methane, and ammonia both in the absence and presence of H2S while varying the Rh metal content from 0.5 to 5 w-%. Our goal was to optimize the composition of the Rh/m-ZrO2 catalyst in view of the production of ultra clean gas applicable for liquid biofuels synthesis. In the presence of 100 ppm sulfur, increasing Rh concentration from 0.5 to 5 w-% did not greatly improve the activity of the catalyst. The bimetallic Pt/Rh/m-ZrO2 catalyst was also less active than the 0.5 w-% Rh/m-ZrO2 catalyst. Furthermore, the Rh/m-ZrO2 catalyst regained its performance at the set point of 800 °C when the sulfur feed was turned off even after exposures to 500-1000 ppm sulfur. Our data allow us to suggest that in the presence of sulfur, the active sites responsible for the reforming reactions are poisoned, but less impact occurs on sites responsible for oxidation reactions. Furthermore, the screening experiments allow to suggest that the Rh/m-ZrO2 catalyst could be applicable to hot gas cleaning in the presence of sulfur (> 50 ppm) at above 800 °C using a moderate gas hourly space velocity of approximately 3400 1/h. Since biomass gasification gas generally contains sulfur, the 0.5 w-% Rh/m-ZrO2 catalyst could be a promising option for gasification gas clean-up applications at temperatures above 800 °C where it reduces tar to very low levels.  相似文献   

19.
Cu/SiO2 catalysts have been successfully prepared via urea hydrolysis method. The catalysts have been systematically characterized by X-ray diffraction, high-resolution transmission electron microscopy, N2-physisorption and H2 temperature-programmed reduction. The results demonstrated the presence of copper nanoparticles and their high dispersion on the SiO2 support. Catalysts with different copper loadings were prepared, and their performances in the hydrogenation of dimethyl oxalate to ethylene glycol were studied. A 100% conversion of dimethyl oxalate and maximum 98% selectivity of ethylene glycol were reached with 15.6 wt.% copper loading at 200 °C and 2 MPa. Furthermore, under the same reaction conditions, the catalyst can maintain the selectivity of 90% when the reduction temperature reduced from 350 °C to 200 °C. The high activity and selectivity over the catalyst may be ascribed to the homogenously distribution of copper nanoparticles on the large surface.  相似文献   

20.
Impedance spectroscopy was used to study the electrochemical performance of pure and ion-impregnated La0.7Sr0.3MnO3 (LSM) cathodes on YSZ (Y2O3-stabilized ZrO2) electrolytes in single chamber fuel cell conditions, i.e. a mixture gas with oxygen as oxidant, methane as fuel and nitrogen as dilute gas. Measurements were taken at the furnace temperature range of 550-750 °C and the CH4/O2 ratios from 1 to 2. Polarization resistances (Rp) for pure and impregnated LSM cathodes increased obviously as the CH4/O2 ratio increased at 650-750 °C. Polarization resistances of Sm0.2Ce0.8O1.9 (SDC) impregnated LSM cathode were much smaller than the ones of pure LSM cathode under the same conditions. Overtemperatures were occurred at both cathodes due to the partial oxidation of methane.  相似文献   

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