While the emissions of the greenhouse gases are reaching the alarming levels, fossil fuels still represent global major energy source. Burning fossil fuels releases enormous amount of CO2 which is attributed to main cause of global warming. Hence conversion of CO2 to chemicals especially synthetic fuels can be a promising path to solve these global problems. CO2 Hydrogenation offers unique path to transform the chemically stable CO2 to industrially important chemicals such as methanol. Methanol synthesis is an exothermic reaction while competing reverse water-gas shift reaction is endothermic. Hence, higher pressure and lower temperature are favourable conditions for higher methanol yield according to Le Châtelier's principle. We have recently demonstrated at H2 partial pressure than the stoichiometry (CO2:H2 = 1:3), &gt;95% CO2 conversion and &gt;98% methanol selectivity could be achieved. In this work, we examined advantages of high-pressure conditions (up to 442 bar) in stoichiometric CO2 hydrogenation by systematic study of temperature, pressure and space velocity using commercial Cu/ZnO/Al2O3 catalyst with aim to possibly avoid recycling of unreacted reactants and CO by achieving high methanol yield. Figure shows great impact of pressure and space velocity on CO2 conversion and methanol selectivity. Almost 90% CO2 conversion and &gt;95% methanol selectivity with high methanol weight time yield of ca. 1.0 gMeOH gcat-1 h-1 was obtained at 442 bar, 280 °C. The reaction mixture at high pressure is dense and internal mass transfer limitation arises. When this limitation could be overcome by using smaller catalyst particles, the high-pressure advantages given by kinetics, thermodynamics are evident (dotted lines in Figure). Under such a condition, extraordinary methanol weight time yield up to 15.3 gMeOH gcat-1 h-1 could be attained at 100,000 h-1 GHSV.

High pressure stoichiometric hydrogenation of carbon dioxide to methanol

253rd National Meeting (2017)

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