| The environmental problems that accompany the progress of human industrial civilization have become increasingly prominent.Restricting carbon dioxide emissions and finding new energy sources and supporting storage technologies have been widely agreed by governments.The carbon dioxide methanation technology is an energy storage technology that uses carbon dioxide as a carrier to generate methane,and converts the energy generated by intermittent clean energy sources such as solar energy into chemical energy for methane storage.This technology is the most mature technology route among many carbon dioxide conversion technologies.Although research on carbon dioxide methanation catalysts has made a lot of progress,there are still some problems to be solved to achieve industrialization.The noble metal ruthenium-based catalyst has better activity than other metals,but its higher loading and high price limit its universal application,and is only suitable for use in price-insensitive areas such as space exploration.The transition metal nickel has the catalytic activity second only to ruthenium,but also has the disadvantages of poor low temperature activity and poor catalyst stability.Therefore,it is of great significance to optimize the support of nickel-based catalysts,optimize the synthesis method,and enhance the methanation performance of the additives to achieve comparable or even better performance than the precious metal ruthenium-based catalysts.According to the above research background,based on the precursor of LDHs,the doping of the third element improves the dispersibility of nickel,adjusts the chemical environment of the surface elements,interacts with the metal support to prepare an efficient carbon dioxide methanation catalyst,and conducts the reaction Explore.The specific work is as follows:(1)Preparation of nickel-cobalt-aluminum catalyst and carbon dioxide methanation performanceThe NiCoAl ternary LDHs precursor was synthesized in one step by a simple and fast solvothermal method,and the cobalt element was successfully introduced into the nickel-based catalyst uniformly.A series of nickel-cobalt-aluminum catalysts were evaluated for their performance,and the influence of cobalt introduction was investigated.It was found that the introduction of cobalt brought incompletely reduced CoOx species,enriched the surface oxygen defects of the catalyst,and also increased the degree of nickel dispersion and reduction.Both of them enhanced the carbon dioxide adsorption activation ability and hydrogenation ability of the catalyst respectively The importance of coordinating these two capabilities,by adjusting the appropriate nickel-cobalt ratio and reduction temperature to make the two effects synergistically,thereby improving catalytic performance,and determine the optimal nickel-cobalt feed molar ratio and reduction temperature.(2)Preparation of nickel-aluminum-cerium catalyst and research on its CO2 methanation performanceUsing the special physicochemical properties of ethylene glycol,a nickel-aluminum-cerium ternary hydrotalcite precursor was synthesized in one step by a simple solvothermal method,and the cerium was in the form of Ce3+in the catalyst by reduction treatment.The introduction of Ce3+ regulates the strength of the metal carrier interaction,promotes the reduction of metals,changes the basic distribution of the catalyst surface,especially enhances the strength and content of medium-strength basic sites,and improves the carbon dioxide activation ability of the catalyst.There is a linear relationship between the content and the TOF value,which indicates that Ce3+is the key influencing factor to promote the low temperature activity of catalyst methanation.In addition,the Ni/Al1-aCesOx catalyst showed good stability in the 55 h stability test,which means that it has potential application value,and a possible reaction of the formate intermediate route without CO*is proposed.mechanism.Provide a new idea for the development of nickel-based catalysts for carbon dioxide methanation. |
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