Development of catalysts for the synthesis of higher hydrocarbons from carbon dioxide

Abstract

The paper is devoted to the development of a catalyst for the synthesis of the higher hydrocarbons from carbon dioxide and hydrogen. The conversion of greenhouse gas CO2 into value-added chemicals contributes not only to sol-ving environmental problems, but also to obtaining valuable fuel. Catalysts that are active in the hydrogenation reaction of CO are also active in the process of CO2 hydrogenation. The most active catalysts in the hydrogenation of carbon dioxide are based on transition metals, in the presence of which mainly methane and a small amount of carbon monoxide are formed. Investigation of the kinetics of hydrocarbons synthesis by hydrogenation of carbon dioxide in the presence of transition metals allowed establishing the mechanism of the process and no perspective of such catalytic systems for hydrocarbons synthesis via intermediate formation of carbon monoxide. It is established that the optimal method of synthesis of higher hydrocarbons is the indirect path, through the intermediate formation of methanol with its further dehydration. The synthesis of methanol from gas mixtures of H2, CO, and CO2 with different composition in the presence of industrial catalysts takes place along the same macroscopic route, by reducing CO2, and is accompanied by a reverse water-gas shift reaction. Therefore, gas mixtures of different composition can be used as raw material for methanol production. Based on our own and literature data, the general peculiarities of the carbon dioxide hydrogenation reaction were obtained, which allowed developing a complex multifunctional catalyst for the synthesis of higher hydrocarbons from carbon dioxide and hydrogen. The proposed catalyst combines the properties of ones for the synthesis of oxygenates from carbon dioxide, and catalysts for the processes of hydrocarbons synthesis from me-thanol and other alcohols. The synthesis of higher hydrocarbons with a predominant content of branched hydrocarbons on the developed bifunctional catalyst was carried out and the optimal conditions for the process were determined.