Effect of copper surface area and acidic sites to intrinsic catalytic activity for dimethyl ether synthesis from biomass-derived syngas

Abstract

The crucial effects of copper surface area and acidic sites to intrinsic catalytic activity on the bifunctional catalysts such as Cu-ZnO/Al2O3 and Cu-ZnO-Al2O3/Zr-modified ferrierite catalysts have been investigated to find out the correlation between these two characteristics for the direct synthesis of dimethyl ether (DME) from biomass-derived syngas. The well-dispersed copper particles with a high reducibility as well as a large amount of weak acidic sites on bifunctional catalysts are responsible for their high catalytic performance. The high activity for methanol synthesis could be obtained by designing a high surface area of metallic copper with a low aggregation character, however, the quantity of the acidic sites on solid-acid components is also crucial factor for a high DME yield than the surface area of copper, which could be obtained by preparing proper bifunctional catalysts. It is mainly due to the fast reaction rate of methanol dehydration to DME compared to CO hydrogenation to methanol. The two important characteristics of the metallic surface area of copper and the amount of acidic sites are well correlated with the intrinsic catalytic activity on this consecutive reaction. The intrinsic activity for the direct DME synthesis from syngas on bifunctional catalysts initially decreases and maintains at constant value with the increase of the values of the copper surface area multiplied by the amount of acidic site.