Enhanced Selectivity to Methanol in CO2 Hydrogenation on CuO/ZrO2 Catalysts by Alkali Metal Modification

Abstract

In order to alleviate the influence of greenhouse effect on global climate change, the effective utilization of CO₂ to prepare fine chemicals should be paid more attention to, however, which is greatly blocked by the catalyst with low efficiency. Here, alkali metal (Li, Na, or K) are employed as a modification aid to prepare CuO/ZrO₂ catalyst for CO₂ hydrogenation to methanol. The effects of alkali metal on physicochemical properties and catalytic activities of CuO/ZrO₂ catalyst were studied in detail by the XRD, N₂-physisorption, ICP-OES, SEM/EDS, H₂/N₂O/CO₂/NH₃-chemisorption, and evaluation test. The results verified that the use of complex combustion method enabled the uniform combination of all components in precursor. High-temperature calcination (700 °C) further enhanced the strong interaction and synergistic effect between Cu and ZrO₂. Most importantly, the introduction of alkali metal effectively altered the structure and catalytic activity of CuO/ZrO₂ catalysts. However, the selectivity to methanol increased while the CO₂ conversion decreased regardless of different kinds of alkali metal being introduced to the CuO/ZrO₂ catalysts. For example, CuO/ZrO₂ catalyst modified by K exhibited excellent performance for methanol production that 98.9% selectivity of methanol based on 8.8% conversion of CO₂ after 48 h online reaction.