Towards full one-pass conversion of carbon dioxide to methanol and methanol-derived products

• Almost complete one-pass conversion of CO2 into methanol under optimized process conditions.
• The methanol stream rich in water and H2 can be directly used for further transformation.
• One-step transformation of CO2 into dimethyl ether with >86% selectivity maintaining the high CO2 conversion.
• Selective formation of alkane or alkene obtained by varying pressure of the secondary reactor with H-ZSM-5.
• A commercial methanol synthesis catalyst delivers the highest yield of 7.7gMeOHgcat-1h-1 with good CO2 conversion and methanol selectivity.

The rising concerns about global warming and imbalance in the carbon cycle urge rapid development of efficient CO2 conversion processes. We report an exceptionally productive process for the synthesis of methanol via continuous catalytic hydrogenation of CO2 under high-pressure conditions (up to 360 bar) over co-precipitated Cu/ZnO/Al2O3 catalysts. Outstanding one-pass CO2 conversion (>95%) and methanol selectivity (>98%) were achieved under an optimized range of reaction conditions. At a very high GHSV of 182,000 h−1 over a commercial methanol synthesis catalyst, the process delivers 7.7gMeOHgcat-1h-1, which is by far the highest yield value reported to date, at the expense of lowered CO2 conversion (65.8%) and methanol selectivity (77.3%). Using a mixed bed consisting of the Cu/ZnO/Al2O3 and H-ZSM-5 catalysts, one-step conversion of CO2 into dimethyl ether with remarkable selectivity (89%) was attained at the equivalent or higher CO2 conversion level. Furthermore, we demonstrate that the effluent stream of methanol, rich in H2 and water, from the methanol synthesis reactor can be directly fed to a reactor containing the H-ZSM-5 catalyst for selective production of alkane (85%) or alkene (42%), depending on the operating pressure of the secondary reactor.

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