Spinel Nanostructures for the Hydrogenation of CO<sub>2</sub> to Methanol and Hydrocarbon Chemicals
Mengheng Wang, Lanling Zheng, Genyuan Wang, Jiale Cui, Gui-Ling Guan, Yu-Ting Miao, Jianfeng Wu, Pan Gao, Fan Yang, Yunjian Ling, Xiangxue Luo, Qinghong Zhang, Gang Fu, Kang Cheng, Ye Wang
Abstract
Composite oxides have been widely applied in the hydrogenation of CO/CO 2 to methanol or as the component of bifunctional oxide–zeolite for the synthesis of hydrocarbon chemicals. However, it is still challenging to disentangle the stepwise formation mechanism of CH 3 OH at working conditions and selectively convert CO 2 to hydrocarbon chemicals with narrow distribution. Here, we investigate the reaction network of the hydrogenation of CO 2 to methanol over a series of spinel oxides (AB 2 O 4 ), among which the Zn-based nanostructures offer superior performance in methanol synthesis. Through a series of (quasi) in situ spectroscopic characterizations, we evidence that the dissociation of H 2 tends to follow a heterolytic pathway and that hydrogenation ability can be regulated by the combination of Zn with Ga or Al. The coordinatively unsaturated metal sites over ZnAl 2 O x and ZnGa 2 O x originating from oxygen vacancies (OVs) are evidenced to be responsible for the dissociative adsorption and activation of CO 2 . The evolution of the reaction intermediates, including both carbonaceous and hydrogen species at high temperatures and pressures over the spinel oxides, has been experimentally elaborated at the atomic level. With the integration of a series of zeolites or zeotypes, high selectivities of hydrocarbon chemicals with narrow distributions can be directly produced from CO 2 and H 2, offering a promising route for CO 2 utilization.