The Development of Uncalcined Cu-Based Catalysts by Liquid Reduction Method for CO₂ Hydrogenation to Methanol

Abstract

CO₂ conversion to CH₃OH plays an important role for the development of energy and the environment, but the preparation of high-performance Cu-based catalyst with high Cu dispersion remains a great challenge. In conventional co-precipitation method, calcination procedure is necessary to acquire stable catalyst for the sake of decomposing precursors, enhancing interaction, improving mechanical strength, even though high temperature treatment may lead to the aggregation of Cu nanoparticles. Herein, a simple liquid reduction strategy without calcination procedure is adopted to alleviate Cu nanoparticles aggregation for boosting the catalytic reactivity. Specifically, we explore catalysts prepared by different preparation methods with various roasting treatments for the synthesis of CH₃OH, and the significance of calcination procedure on Cu-based catalysts obtained from different preparation methods is emphatically investigated. Cu–Zn–Al–Zr catalysts prepared by liquid reduction method have been decomposed to metal/metal oxides in the effect of NaBH₄ without high-temperature calcination, and theses stable Cu–Zn–Al–Zr catalysts are directly applied to the synthesis of methanol to avoid sintering of Cu species caused by thermal roasting. The uncalcined CZAZ sample exhibits better catalytic activity than the calcined CZAZ-573 sample due to a higher Cu specific surface area, a stronger reducibility and a larger number of basic sites. The uncalcined CAZA catalyst exhibits outstanding catalytic activity with CO₂ conversion of 23.2% and CH₃OH selectivity of 64.3% at 523 K, and it maintains a stable STY of methanol during continuous 500 h operation. Liquid reduction method towards the development of uncalcined catalyst will potentially guide the rational design of a broad range of highly dispersed metal nanoparticles catalysts.

Graphical Abstract