The Study On Ni-Co Bimetallic Catalyst For CH₄-CO₂ Reforing Reaction

The dramatic climate change caused by the greenhouse effect has brought about wide attention, as a consequence, the way of decreasing the emissions of greenhouse gas has attracted the public. It is probable to transform two gases (CH4 and CO2) into hydrogen and carbon monoxide syngas at the same time by the method of methane reforming carbon dioxide reaction, in this situation, it is conducive to the industrial production. This reaction not only reduce the influence of the greenhouse effect, also can provide a large amount of chemical products. Furthermore, it brings considerable environmental and economic benefits. However, the process has not found wide industrial application due to severe catalyst deactivation, basically caused by carbon formation. Therefore, it is of great interest to develop stable catalysts without severe deactivation. This work is primarily focused on nickel-based catalysts to investigate the influence of preparation conditions、reduction conditions and reaction conditions on catalysts performance.The designed catalysts are prepared under different calcination temperature using co-precipitation method,the Ni-Co/AlMgOx catalysts are characterized using various techniques such as XRD, TPR to analyse the structure and reduction ability of catalysts, the result shows:calcination temperature has important impacts on the performance of Ni-Co/AlMgOx catalysts, along with the calcination temperature increasing, the interaction between metal component and support enhances, spinel structures appear, but the particle size also increases,a suitable calcination temperature not only make more reduction of active component, also can maintain stable reaction, so a calcination temperature of 800℃ is recommended.In order to research reduction condition on catalysts performance, we change the reduction time、temperature and methods. The research finds, compared with isothermal reduction, temperature programmed reduction is better; reduction temperature influences the active component and support properties, then affects the interaction between the two, when temperature is low, part of the active component can not be reduced, reactivity is low, on the contrary, high temperature can rise accumulation of active component and reduce the dispersion; reduction time also influences the performance, a right time can increase the metal dispersion and the stability.Further investigation on Ni-Co/AlMgOx catalysts shows that reaction conditions can significantly affect catalyst performance, including particle size、space velocity、 reaction temperature、feed gas ratio、stability and regeneration.The result indicates:to a certain extent,catalyst particle size distribution affects the spread of catalyst surface active species, thus affects catalytic reaction conversion rate and product selectivity; when the catalyst is fixed, the greater the import flow velocity, that means more gases per unit time through the catalyst, the shorter time on the bed, the reaction is inadequate, so reducing space velocity can improve conversion, but when the velocity is too low, in order to achieve the same capacity,the amount of catalyst needed is more, for the fixed device,the volume limitations are certain, so we should choose the suitable speed based on the equipment and wished conversion; methane reforming carbon dioxide reaction is highly endothermic, the higher the temperature is, the better performances are, but the chance of side reactions increases at higher temperatures, such as carbon formation reaction, so we should choose a better temperature to increase the conversion and control side reactions; when the reactants are increased, the reaction is tend to the direction of reducing the reactants, the conversion of CO2 improves with CH4 concentration increasing, but for CH4,concentration is high, reaction equilibrium motion can’t weaken the effect well, so the conversion of CH4 drops, and vice versa; a preliminary exploration on the feasibility of catalyst regeneration with reducing atmosphere carried out, after reducing atmosphere treatment, the catalyst activity has been improved to a certain degree, in order to achieve better results, however, it still need further detailed inspection.This catalyst has superior performance in terms of activity and stability in long-term research,no significant inactivation phenomenon is observed within 180h,it also remains high activity and good stability.