Development of high performance Cu/ZnO-based catalysts for methanol synthesis and the water-gas shift reaction

Abstract

Our group's studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO 2 and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al 2 O 3 , ZrO 2 or SiO 2 improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO 2 and H 2 over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO 2 , but not via the hydrogenation of CO, and that H 2 O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as were highly active for methanol synthesis from CO 2 and H 2 . The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO 2 and H 2 . The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO 2 /Al 2 O 3 catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H 2 at high temperatures than that of the Cu/ZnO/Al 2 O 3 catalyst. Accordingly, the Cu/ZnO/ZrO 2 / Al 2 O 3 catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO 2 /Al 2 O 3 catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO 2 and H 2 .

Chemical Recycling of Carbon Dioxide to Methanol and Dimethyl Ether: From Greenhouse Gas to Renewable, Environmentally Carbon Neutral Fuels and Synthetic Hydrocarbons

“…[49][50][51][52] In view of our present understanding of the mechanism of the syngas based chemistry, this is not unexpected. Although still debated, it is now usually accepted that methanol is formed almost exclusively by hydrogenation of CO 2 contained in the syngas on the catalyst's surface.…”

Electrochemical Reduction of CO 2

“…Cuprous oxides in aqueous solution behave in the same way as Cu (I), favorably adsorbed CO and leads to the formation of methanol. Cu(I) species allowed valence band electron to participate in CO adsorption [20], [27], [47], [54], [64], [112].…”

“…Similarly, other researchers investigated that oxide defects on surface of electrocatalyst kept catalyst stable against hydrogenation reaction and thus play effective role in CO 2 reduction [47], [48].…”

Current progress on zeolite membrane reactor for CO2 hydrogenation

“…The catalyst used for CO2 hydrogenation is mainly Cu-based catalyst with various modifiers such as Zn, Zr, Ce, and Si [55][56][57]. Zinc oxide can improve the dispersion and stabilization of Cu [58,59].…”