Highly Efficient CuPd<sub>0.1</sub>/γ-Al<sub>2</sub>O<sub>3</sub> Catalyst with Isolated Pd Species for CO<sub>2</sub> Hydrogenation to Methanol
Hongxin Pan, Baorun Ma, Lihui Zhou, Yongfeng Hu, Mohsen Shakouri, Yong Guo, Xiaohui Liu, Yanqin Wang
Abstract
CO 2 hydrogenation is one of the most effective solutions for mitigating excessive CO 2 emissions. In this work, CuPd x /γ-Al 2 O 3 ( x = 0.05–5.7 wt %) catalysts were prepared and applied in CO 2 hydrogenation to methanol. The results showed CuPd 0.1 /γ-Al 2 O 3 achieved excellent CO 2 hydrogenation activity. It is demonstrated that the Pd species of CuPd 0.1 /γ-Al 2 O 3 is highly dispersed on the γ-Al 2 O 3 support at the atomic level and separated from Cu nanoparticles by AC-HAADF-STEM, rather than forming CuPd alloy. Part of the hydrogen species activated by isolated Pd atoms overflows onto γ-Al 2 O 3 and influences the reduction of CuO, thus effectively increasing the Cu + /(Cu + +Cu 0 ) ratio which is correlated with the prominent CO 2 hydrogenation performance. On the other hand, we found that CH 3 OH retained on catalyst surface can be further reformed into CO, which significantly reduces the selectivity of CH 3 OH. To limit CH 3 OH reforming, the activity test of CuPd 0.1 /γ-Al 2 O 3 in a fixed bed at different weight hourly space velocity was performed, where the remarkable methanol yields of 5.9 mmol/g cat. /h were obtained.