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Fixed-bed Reactor (fixed-bed + reactor)
Selected AbstractsEffects of NO2, CO, O2, and SO2 on oxidation kinetics of NO over Pt-WO3/TiO2 catalyst for fast selective catalytic reduction processINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2006Muhammad Faisal Irfan The selective catalytic reduction rate of NO with N-containing reducing agents can be enhanced considerably by converting a part of NO into NO2. The enhanced reaction rate is more pronounced at lower temperatures by using an equimolar mixture of NO and NO2. The kinetics of NO oxidation over Pt-WO3/TiO2 catalyst has been determined in a fixed-bed reactor with different concentrations of oxygen, nitric oxide, and nitrogen dioxide in the presence of 8% water. It has been found that the reaction is second order with respect to nitric oxide, first order for oxygen with a third-order rate constant. Also, it is found that there is no effect on the reaction order with an addition of NO2, CO, or SO2. It follows the same second order but the reaction rate is found to be changed. It is observed that in the case of NO2 and SO2, the reaction rate tends to decrease, but it increases with the addition of CO into the feed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 613,620, 2006 [source] Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silicaJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2007Abd El-Aziz A Said Abstract Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 °C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N2 adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration,dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas-phase estrification of acetic acid with ethanol was carried out at 185 °C in a conventional fixed-bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO2 is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Copyright © 2007 Society of Chemical Industry [source] Surface properties and catalytic behavior of MoO3/SiO2 in esterification of acetic acid with ethanolJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2006Abd El-Aziz A Said Abstract A series of MoO3/SiO2 catalysts was prepared by an impregnation method with Mo loadings ranging from 1 to 50 wt%. The original and calcined samples at 400 °C were characterized by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, and nitrogen adsorption measurements. The surface acidity and basicity of the catalysts were investigated by the dehydration,dehydrogenation of isopropanol and the chemisorption of pyridine. The catalytic esterification of acetic acid with ethanol was carried out at 220 °C in a conventional fixed-bed reactor at 1 atm using air as a carrier gas. The results clearly revealed that silica,molybdena catalysts were active and selective towards the formation of ethyl acetate. Moreover, the catalyst containing 20 wt% MoO3 was the most active and selective one. The results emphasize the importance of the surface acid sites together with the specific surface area of the prepared catalyst, towards ester formation. Copyright © 2005 Society of Chemical Industry [source] High resistance to aerial oxidation of an amorphous NiB/SiO2 catalyst: TP-XRD, TPR and related investigationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2004Yong-Zhen Wang Abstract An amorphous NiB/SiO2 catalyst, prepared by a reductive,impregnation method, was thoroughly studied as to its behavior in air and in benzene hydrogenation in a fixed-bed reactor at atmospheric pressure. The results showed that the amorphous NiB/SiO2 catalyst possessed long life and excellent resistance to aerial oxidation. Even after calcination at 400 °C, TP-XRD and TPR measurements revealed that the amorphous NiB/SiO2 catalyst was not oxidized, and could retain its activity in benzene hydrogenation. Copyright © 2004 Society of Chemical Industry [source] Biological treatment of saline wastewaters from marine-products processing factories by a fixed-bed reactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Neji Gharsallah Abstract Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30,g,dm,3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish-processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000,mg,COD,dm,3 day,1. Under low OLR (250,mg,COD,dm,3 day,1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000,mg,COD,dm,3 day,1. © 2002 Society of Chemical Industry [source] Light FCC gasoline olefin oligomerization over a magnetic NiSo4/,-Al2o3 catalyst in a magnetically stabilized bedAICHE JOURNAL, Issue 3 2009Ying Peng Abstract Magnetic NiSO4/,-Al2O3 catalysts were prepared by impregnating NiSO4 solutions onto the ,-Al2O3 support containing a magnetic material of Fe3O4. Characterization by XRD, NH3 -TPD, and thermal analysis showed that the magnetic NiSO4/,-Al2O3 catalyst with a nickel content of 7.0% by weight had a monolayer dispersion of NiSO4 and the largest number of moderate strength acid sites, and a high specific saturation magnetization. The magnetic catalyst was evaluated for light FCC gasoline olefin oligomerization in both fixed-bed and magnetically stabilized bed (MSB) reactors. Comparing with that in the fixed-bed reactor, the optimal reaction temperature in the MSB lowered to 443 K, and its space velocity ranged broadly from 2.0 to 6.0 h,1. The sulfur-free diesel distillate produced by operation of the MSB for 100 h had higher cetane number and good low-temperature flow property, which illuminates a promising application of the MSB to manufacture clean diesel fuels with high productivity and flexibility. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Catalysts for water,gas shift processing of coal-derived syngases,ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010San Shwe Hla Abstract Although the gasification of coal is an efficient means of producing syngas, the carbon content of coal is such that gasification produces significantly higher ratios of carbon oxides to hydrogen than those obtained by the steam reforming of natural gas. The CO:H2 ratio can be adjusted, and more hydrogen produced, by the subsequent application of the water,gas shift (WGS) reaction. This article presents a review of technologies associated with the catalytic WGS reaction in a fixed-bed reactor that might be incorporated into a coal gasification-based system for H2 production with CO2 capture. The main output from this review is the identification of key project areas requiring further research. The performance of existing, commercially available catalysts,designed for use in natural gas reforming processes,with coal-derived syngases is an important aspect of developing technologies for coal-based H2 production. This article presents an experimental assessment of the performance of selected commercially available WGS catalysts, two high-temperature catalysts (HT01 and HT02) and a sour shift catalyst (SS01), with such syngases. For the three commercial catalysts investigated in this study, CO reaction order is found to be in a range of 0.75,1. The effect of changes in H2O concentration over HT01 is insignificant, whereas H2O reaction orders determined using HT02 and SS01 are found to be significantly positive even at high H2O:C ratios. The CO conversion rate is significantly reduced by increasing CO2 concentration, whereas increasing H2 concentration also causes a slight reduction in CO conversion rate for the three commercial catalysts investigated. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Pd,Ag membranes for auto-thermal ethanol reformingASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Silvano Tosti Abstract The auto-thermal ethanol reforming was carried out at 200 kPa by a two-step process consisting of a traditional reformer operating at high temperature (700,740 °C) and a Pd,Ag multitube membrane module where the separation of hydrogen took place at 350,380 °C. The membrane module was a bundle of 11 thin-wall Pd,Ag tubes of wall thickness 50,60 µm, diameter 10 mm, and length 270 mm: permeation tests were performed at 300,395 °C with lumen pressure of 150,200 kPa, and nitrogen sweep flow rates in the shell side ranged from 10 to 30 l min,1 at atmospheric pressure. A hydrogen permeance Pe = 1.317 × 10,2 exp (,3.622 × 103/T(K)) mol m,2 s,1 Pa,0.5 was measured and complete hydrogen selectivity was verified. A water/ethanol mixture of molar ratio 2.50/1.00 was used as feed stream for carrying out ethanol reforming in the traditional fixed-bed reactor filled with a Ni on alumina catalyst. As a second step, the water gas shift (WGS) membrane reaction was carried out in the multitube membrane reactor: the Pd,Ag alloy of the membrane tubes worked for both catalyzing the reaction and for separating all the hydrogen produced in the reformer and in the membrane reactor itself. The hydrogen separated through the membrane was collected in the shell side of the membrane module: by operating with a water/ethanol feed flow rate of 200 g h,1, up to 1.2 l min,1 of pure hydrogen was produced. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Research on alkali-catalyzed gasification of coal black liquor slurry cokes made up by five different coals,ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007Kuang Jian-ping Abstract The black liquor from paper mills contains large quantities of sodium compounds and other organic matter, such as lignin and cellulose. The sodium compounds will provide the catalytic action in coal black liquor slurry (CBLS) gasification, while lignin and cellulose can enhance the heat value in the process of gasification. Five black liquor slurries were made from coals from different regions: Xin Wen, Huang Ling, Zao Zhuang, Shen Mu and Shen Hua. Alkali-catalyzed gasification experiments on the different samples of CBLS and coal water slurry (CWS) were made on a thermobalance and a fixed-bed reactor. The residues of gasification were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results reveal that many mesopores and micropores exist on the surface of the CBLS coke, which play a key role in the catalytic gasification process, and sodium as a catalyst can quicken the gasification reaction rate. XRD shows that NaCl and sodium silicate are the main crystal components in dry samples of CBLS and CWS. The C-O stretching vibration peak shifting to a lower wavenumber means that the energy for the C-O stretching vibration in the CBLS carbon matrix decreases after partial gasification. Not only the coal rank but also the oxygen-containing groups and minerals influence coal coke's gasification activity. Of the five different CBLS, the gasification reactivity of CBLS made by the Huang Ling coal was found to be higher than that of the others. The higher the degree of coalification, the lower the activity of the coke. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Formation of Furfural in Catalytic Transformation of Levoglucosan over Mesoporous MaterialsCHEMCATCHEM, Issue 5 2010M. Käldström Abstract Catalytic transformations of levoglucosan (1-6-anhydro-,- D -glucopyranose) and furfural were carried out in a fixed-bed reactor at 573,K over mesoporous materials. Proton forms of MCM-41, MCM-48, SBA-15, and platinum form of MCM-48 catalysts were tested in the reaction, whereas H-Beta and quartz sand were used as reference materials. The yield of the transformation products was substantially influenced by the catalyst structures. Oxygenated species were the main liquid products, consisting mainly of aldehydes and furfural. The formation of furfural was the highest over MCM-41 catalyst followed by SBA-15, MCM-48, and H-Beta catalyst. All catalysts were to some extent deactivated due to coke formation. However, it was possible to successfully regenerate the spent catalysts without changing the structure. [source] Estimation of Kinetic Parameters for Hydrogenation Reactions Using a Genetic AlgorithmCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2009A. Kadiva Abstract The kinetics of acetylene hydrogenation in a fixed-bed reactor of a commercial Pd/Al2O3 catalyst has been studied. The hydrogenation reactor considered in this work is an essential part of a vinyl chloride monomer (VCM) plant. Three well-known kinetic models were used to simulate the hydrogenation reactor under industrial operating conditions. Since none of the models provide appropriate prediction, the industrial data and calculated values were compared and optimum kinetic parameters were evaluated utilizing a genetic algorithm (GA) technique. The best kinetic parameters for the three models were determined under specified industrial operating conditions. The hydrogenation reactor was simulated using the estimated optimum kinetic parameters of the three models. Simulation results from the three models were compared to industrial data and the best kinetic model was found. This kinetic model with the evaluated optimum kinetic parameters can well predict the behavior of the industrial hydrogenation reactor to improve the performance of the process. [source] Preparation of Ni-Based Metal Monolithic Catalysts and a Study of Their Performance in Methane Reforming with CO2CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 6 2008Kai Wang Abstract A series of Ni/SBA-15/Al2O3/FeCrAl metal monolithic catalysts with Ni loadings varying between 3,% and 16,% were prepared, and their structure was characterized by various techniques. The catalytic activity of the catalyst for methane reforming with CO2 leading to synthesis gas was evaluated using a fixed-bed reactor. The results indicate good catalytic activity of the Ni/SBA-15/Al2O3/FeCrAl samples under the reaction conditions. The catalyst with a Ni loading of 8.0,% displays excellent activity and stability at 800,°C over 1400,h time on stream. After reaction, the hexagonal mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. Interactions between NiO, SBA-15, and the Al2O3/FeCrAl support modify the redox properties of the Ni/SBA-15/Al2O3/FeCrAl catalysts. [source] Catalytic Performances of Binder-free ZSM-5 Catalysts for Dehydration of Crude Methanol to Dimethyl EtherCHINESE JOURNAL OF CHEMISTRY, Issue 2 2010Jing Wang Abstract A series of binder-free ZSM-5 catalysts and a binder-containing catalyst were prepared and characterized with X-ray diffraction (XRD), X-ray fluorescence (XRF), 27Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR), N2 sorption and ammonia temperature-programmed deposition (TPD) methods. The catalytic activity and selectivity in the dehydration of crude methanol to dimethyl ether (DME) were evaluated in a fixed-bed reactor for the catalysts. The outstanding structural characters such as high zeolite contents, sufficiently open channels and richness in mesopores have been proved on these binder-free catalysts. The influence of the solid-acidity, which is closely related to the framework silica alumina ratio (SAR) of the catalysts, on the catalytic properties has been discussed. A binder-free catalyst with a better potential in application has been selected for its high activity and selectivity, long life-time and non-sensitivity to water contents in the feed. The reason for its excellent performance of the catalyst was discussed. [source] | ||||||||||