Cu/ZnO catalysts integrated with AlO and/or SiO for methanol synthesis; Deciphering the additive-induced boost in catalytic performance by XAFS

Iwasaki, Kosei*; Ashida, Yuya*; Matsumura, Daiju   ; Kawakami, Kotaro*; Shibuya, Kana*; Tazawa, Masaru*; Tsuji, Takuya  ; Shimizu, Hajime*

The development of active, long-lived methanol synthesis catalysts can be expedited by thoroughly understanding the operating mechanisms of promoter additives. SiO serves as an effective support and promoter for Cu/ZnO-type methanol synthesis catalysts; however, it has not been studied as extensively as the industrially predominant AlO, despite being similarly potent. Therefore, we conducted X-ray absorption fine structure predominant AlO, despite being similarly potent. Therefore, we conducted X-ray absorption fine structure studies to probe the effects of incorporating AlO and SiO additives into Cu/ZnO-based heterogeneous catalysts. The results revealed that the additive elements primarily affected the ability of the Zn species to generate oxygen vacancies by distorting the local structure around element-doped ZnO and that the number of oxygen vacancies correlated to the catalytic activity. Additionally, the oxygen vacancies in ZnO in the Al/Si-incorporated catalysts diminished under catalytic reaction conditions, thereby providing information on the deactivation of catalytic reactions. Our findings can facilitate the development of highly active industrial-grade methanol synthesis catalysts.