Improving methanol selectivity in CO2 hydrogenation by tuning the distance of Cu on catalyst

• Published in: Applied catalysis. B, Environmental Environmental, 2021-12, Vol.298, p.120590, Article 120590
• Main Authors: Cui, Xiaojing, Chen, Shuai, Yang, Huanhuan, Liu, Yequn, Wang, Huifang, Zhang, He, Xue, Yanfeng, Wang, Guofu, Niu, Yulan, Deng, Tiansheng, Fan, Weibin
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Carbon dioxide; Catalysts; CO2 hydrogenation; Copper; Cu/ZnO catalyst; Distance effect; Hydrogen spillover; Hydrogenation; Methanol; Nanoparticles; Scanning transmission electron microscopy; Selectivity; Silica; Silicon dioxide; Species diffusion; Transmission electron microscopy; Water gas; Zinc oxide
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2021.120590

Hydrogen (H) spillover happened from Cu0 to SiO2, promoting RWGS reaction and thus CO formation. The contribution of H spillover to RWGS reaction can be controlled by the distance of Cu or coverage of surface hydroxyls on SiO2, which shifted the product selectivity from CO to CH3OH. [Display omitted] •A novel distance effect of Cu is discovered on Cu-based catalyst for CO2 hydrogenation, boosting CH3OH and CH3OCH3 selectivity from 36 to 89 mol%.•H spillover from Cu to SiO2 is identified, which can be regulated by the distance of Cu.•The regulation of H spillover restrains reverse water gas shift reaction and CO formation, which highlights CH3OH and CH3OCH3 selectivity. It is desirable but challenging to obtain high methanol selectivity in CO2 hydrogenation on Cu/ZnO catalysts. Herein, we dispersed a commercial Cu/ZnO/Al2O3 on a silica support for CO2 hydrogenation to methanol, and discovered by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM) that the distance between Cu nanoparticles on silica tuned the total methanol selectivity from 35.5 mol% to 88.9 mol%. This distance effect of Cu was elucidated by H2-TPR, FT-IR, in situ DRIFT, and catalyst silylation modification. It was identified that the active hydrogen species produced on Cu diffuse onto silica via the surface silanols, promoting reverse water gas shift (RWGS) reaction to produce CO. The average concentration of spilled hydrogen species was decreased along with the distance of Cu on silica, suppressing RWGS reaction and thus highlighting methanol selectivity. We anticipate that the distance effect observed here is prevalent on metal supported catalysts in other (de)hydrogenation reactions.