image: The proximity of Cu and Ga species over Cu/Ga-SiO2-20Me catalyst could simultaneously realize tandem reactions of hydrogenation of CO2 to methanol and dehydration of methanol to DME, where further transportation and re-adsorption of methanol intermedia to the hydrophobic catalyst was avoided. Moreover, the methyl groups efficiently removed the water generated in these two reactions, shifting the reaction equilibrium forward. In this case, CO2 conversion and DME selectivity were both promoted over Cu/Ga-SiO2-20Me catalyst.
Credit: Chinese Journal of Catalysis
The selective conversion of CO2 and H2 into valuable chemicals and fuels is a promising route for carbon recycling. Multiple routes have been developed for the CO2 hydrogenation to methanol, higher alcohols, dimethyl ether (DME), aromatics, hydrocarbon, and olefins. Among these products, DME is attractive because it is nontoxic and noncorrosive and has been used as a platform chemical in industry, a carrier for hydrogen, and an additive for fuels.
A series of catalysts has been synthesized for the direct hydrogenation of CO2-to-DME via cascade catalysis involving methanol synthesis and methanol condensation to DME over a supported copper catalyst. However, high DME selectivity was only achieved at low conversion of CO2, resulting in poor one-pass productivity. When the CO2 conversion increased, abundant by-products of CO, methanol, and hydrocarbons were produced. A recent trend is CO2 to DME conversion over bifunctional catalysts, such as acid oxide-supported copper nanoparticles, but their performance is still unsatisfactory. In addition, the copper nanoparticles were sintered during catalysis, resulting in poor durability.
Recently, a research team led by Prof. Feng-Shou Xiao and Prof. Liang Wang from Zhejiang University, China, overcomes these limitations by developing a highly active, selective, and durable copper nanoparticle catalyst for converting CO2-to-DME. This was achieved by loading Cu nanoparticles onto hydrophobic and Ga-modified silica supports. The Ga-modified silica provided moderate acidity for methanol dehydration to DME, which hindered deep dehydration to hydrocarbons. Importantly, the hydrophobic catalyst surface efficiently hinders the sintering of the Cu nanoparticles, which is usually triggered by water and methanol. Consequently, under the following reaction conditions (6000 mL gcat–1·h–1, 3 MPa, 240 °C), the CO2 conversion of 9.7%, DME and methanol selectivities of 59.3% and 28.4%, and CO selectivity of only 11.3% were obtained. In a continuous evaluation for 100 h, the performance was well maintained without any deactivation trend, outperforming the general supported Cu catalysts. For more detailed information, please refer to their publication in the Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(23)64535-8).
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About the Journal
Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top one journals in Applied Chemistry with a current SCI impact factor of 16.5. The Editors-in-Chief are Profs. Can Li and Tao Zhang.
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Journal
Chinese Journal of Catalysis
Article Title
Selective hydrogenation of CO2 into dimethyl ether over hydrophobic and gallium-modified copper catalysts
Article Publication Date
22-Nov-2023