17 research outputs found

    Catalytic-Dielectric Barrier Discharge Plasma Reactor For Methane and Carbon Dioxide Conversion

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    A catalytic - DBD plasma reactor was designed and developed for co-generation of synthesis gas and C2+ hydrocarbons from methane. A hybrid Artificial Neural Network - Genetic Algorithm (ANN-GA) was developed to model, simulate and optimize the reactor. Effects of CH4/CO2 feed ratio, total feed flow rate, discharge voltage and reactor wall temperature on the performance of catalytic DBD plasma reactor was explored. The Pareto optimal solutions and corresponding optimal operating parameters ranges based on multi-objectives can be suggested for catalytic DBD plasma reactor owing to two cases, i.e. simultaneous maximization of CH4 conversion and C2+ selectivity, and H2 selectivity and H2/CO ratio. It can be concluded that the hybrid catalytic DBD plasma reactor is potential for co-generation of synthesis gas and higher hydrocarbons from methane and carbon dioxide and showed better than the conventional fixed bed reactor with respect to CH4 conversion, C2+ yield and H2 selectivity for CO2 OCM process

    Co-Generation of C2 Hydrocarbons and Synthesis Gases from Methane and Carbon Dioxide: a Thermodynamic Analysis

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    This paper deals with thermodynamic chemical equilibrium analysis using the method of direct minimization of Gibbs free energy for all possible CH4 and CO2 reactions. The effects of CO2/CH4 feed ratio, reaction temperature, and system pressure on equilibrium composition, conversion, selectivity and yield were studied. In addition, carbon and no carbon formation regions were also considered at various reaction temperatures and CO2/CH4 feed ratios in the reaction system at equilibrium. It was found that the reaction temperature above 1100 K and CO2/CH4 ratio=1 were favourable for synthesis gas production with H2/CO ratio unity, while carbon dioxide oxidative coupling of methane (CO2 OCM) reaction to produce ethane and ethylene is less favourable thermodynamically. Numerical results indicated that the no carbon formation region was at temperatures above 1000 K and CO2/CH4 ratio larger than

    Methane-Carbon Dioxide: Conversions to Syngas and Hydrocarbons

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    This monograph describes the new innovation that has recently been developed for the CH4-CO2 conversions process. Optimization of CO2 reforming of methane to synthesis gas with the help of experimental design, empirical modeling and ANN modeling are developed for CORM in presence of oxygen. An overview on dynamic equilibrium analysis has shown that an increase of sweep factors induced more significant enhancement hydrogen permeation than permselective area. The NiO/CeO2 catalyst showed potential as catalyst for the CORM. The application of a hybrid catalytic DBD plasma reactor has the potential for the co-generation of C2+ hydrocarbons and synthesis gases from methane and carbon dioxide. Carbon dioxide as co-feed has important effects on the carbon suppression. It can be concluded that three factors, i.e. CH4/CO2 feed ratio, total feed flow rate, and discharge voltage, in the DBD plasma reactor system have significant effects on the reactor performance. The hybrid catalytic DBD plasma reactor is more suitable for CO2 OCM process than the conventional catalytic reactor over CaO-MnO/CeO2 catalyst. Further innovation and improvement of current research on CH4 and CO2 are required to increase conversion and selectivity and to commercialize the process

    Synergistic effect of catalyst basicity and reducibility on performance of ternary CeO2-based catalyst for CO2 OCM to C2 hydrocarbons

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    The present investigation focuses on the synergistic effect of catalyst basicity and reducibility on the catalytic activity of binary and ternary CeO2-based catalysts in the CO2 oxidative coupling of methane (CO2 OCM). Proper amount of medium and strong basic sites together with lower amount of very strong basic sites are identified as pertinent factors in increasing the catalytic performance. The CO2-TPD and H2-TPR studies indicate synergistic effect between the catalyst basicity and reducibility for the 12.8CaO–6.4MnO/CeO2 ternary metal-oxide catalyst in enhancing the CO2 OCM performance

    Cu/W/HZSM-5 for methane conversion to liquid hydrocarbons

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    The direct conversion of natural gas, and in particular, the principal component, methane to useful products has been intensely studied over the past decades. ZSM-5 zeolite has been known to be a suitable catalyst for olefin oligomerization, but it is known to be a suitable catalyst for olefin oligomerization, but it is not resistant to high temperatures. In this work, HZSM-5 was modified with copper and tungsten to develop a highly active and heat resistant bifunctional oxidative-acid catalyst. The performances of Cu modified W/HZSM-5 were compared with HZSM-5 for the oxidation of methane to liquid hydrocarbons. The characterization results revealed that the addition of tungsten to HZSM-5 zeolite improved its thermal stability. Response Surface Methodology (RSM) was employed to determine the optimum methane conversion and C5+ selectivity. Numerical results indicated the optimum methane conversion of 29.54% with the corresponding C5+ selectivity of 57.2% were achieved at 12.3 vol % of O2, 203.9 ml/min of total feed flow rate, and % W doped of 3.2 wt%. The optimum C5+ selectivity of 70.2% was attained at 7.6 vol % of O2, 208.9 ml/min of total feed flow rate, and 3.2 wt% of W content with the corresponding methane conversion of 26.7%. By means of variance analysis and additional experiments, the adequacy of this model was confirmed

    Hybrid Artificial Neural Network-Genetic Algorithm Technique for Modeling and Optimization of Plasma Reactor

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    A hybrid artificial neural network-genetic algorithm (ANN-GA) numerical technique was successfully developed to model, to simulate, and to optimize a dielectric barrier discharge (DBD) plasma reactor without catalyst and heating. Effects of CH4/CO2 feed ratio, total feed flow rate, and discharge voltage on the performance of noncatalytic DBD plasma reactor were studied by an ANN-based simulation with a good fitting. From the multiobjectives optimization, the Pareto optimal solutions and corresponding optimal process parameter ranges resulted for the noncatalytic DBD plasma reactor owing to the optimization of three cases, i.e., CH4 conversion and C2+ selectivity, CH4 conversion and C2+ yield, and CH4 conversion and H2 selectivity

    Multi-response optimization strategy for catalyst compositions and process parameters design for CO2-OCM process over CaO-MnO/CeO2 catalyst

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    The catalytic CO2-OCM (Carbon Dioxide Oxidative Coupling of Methane) reaction to produce C2+ hydrocarbons is considered to be one of the most effective uses of natural gas in the gas-based petrochemical industries. A new hybrid numerical approach, using Weighted Sum of Squared Objective Functions (WSSOF) algorithm, was developed for multi-response optimization of CO2-OCM. The hybrid approach combined the response surface methodology (RSM) and MATLAB optimization tools to produce a set of Pareto-optimal solutions. An additional criterion was proposed over the Pareto-optimal solutions to obtain a final unique solution. Maximum responses of any two combinations of C2+ selectivity, C2+ yield and CH4 conversion were obtained simultaneously at the corresponding optimal conditions of CO2/CH4 ratio, reactor temperature, as well as wt% CaO and wt% MnO in the Ce02-supported catalyst

    Screening of MgO- and CeO2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C2+ Hydrocarbons

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    The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO-and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2 2− ) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2 -based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively. Key words: catalyst screening, carbon dioxide, oxidative coupling, methane, ternary metal oxide, binary metal oxide, MgO, CeO2 , C2+ hydrocarbon

    Modelling and optimization of catalytic-dielectric barrier discharge plasma reactor for methane and carbon dioxide conversion using hybrid artificial neural network-genetic algorithm technique

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    A hybrid artificial neural network-genetic algorithm (ANN-GA) was developed to model, simulate and optimize the catalytic-dielectric barrier discharge plasma reactor. Effects of CH4/CO2 feed ratio, total feed flow rate, discharge voltage and reactor wall temperature on the performance of the reactor was investigated by the ANN-based model simulation. Pareto optimal solutions and the corresponding optimal operating parameter range based on multi-objectives can be suggested for two cases, i.e., simultaneous maximization of CH4 conversion and C2+ selectivity (Case 1), and H2 selectivity and H2/CO ratio (Case 2). It can be concluded that the hybrid catalytic-dielectric barrier discharge plasma reactor is potential for co-generation of synthesis gas and higher hydrocarbons from methane and carbon dioxide and performed better than the conventional fixed-bed reactor with respect to CH4 conversion, C2+ yield and H2 selectivity

    Catalyst screening for CO2 oxidative coupling of methane to C2 hydrocarbons

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    Basic metal oxides are suitable catalysts for the selective oxidative coupling of methane reaction using CO2 as an oxidant known as CO2 OCM hereafter. Catalysts screening for CO2 OCM was performed using CeO2- and MgO-based catalysts. The performance of the catalysts was tested in a fixed-bed quartz reactor. The CeO2 support was combined with alkaline earth metal oxide (CaO) and transition metal oxide (WO3 or MnO) to form a ternary metal oxide catalyst. The other catalyst tested was MgO doped with Li2O. The addition of WO3 to the CeO2 catalyst is able to enhance the C2 hydrocarbon selectivity, while the addition of MnO doping was able to increase the C2 hydrocarbons yield and CH4 conversion. The Li2O/MgO catalyst is a more promising catalyst for CO2OCM rather than CeO2-based catalysts. The C2 hydrocarbon yield of 5.7% and selectivity of 92.7% were obtained over Li2O/MgO catalyst. Raman spectroscopy was employed to characterize the catalysts
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