不同形貌ZnO催化CO_(2)加氢性能研究

Study on catalytic performance of ZnO with different morphologies for CO_(2) hydrogenation

ZnO基催化材料可将CO_(2)选择性加氢转化为CH3OH等高附加值化学品,因而受到广泛关注,但其催化活性中心结构及构效关系仍有待进一步研究。以ZnO为模型催化剂,探究了催化性能与活性位点间的构效关系,通过水热合成方法制备了片状ZnO和棒状ZnO,其中,片状ZnO优先暴露(002)晶面,棒状ZnO优先暴露(100)和(101)晶面。在300℃时,片状ZnO的CO_(2)转化率和CH3OH生成速率分别为5.8%和0.220 mmol/(g·h),优于棒状ZnO(1.5%和0.095 mmol/(g·h))。原位红外光谱表征结果表明,孤立的Zn位点倾向于生成CO,而邻近的多Zn位点之间通过协同作用促进CH3OH的生成。ZnO(002)晶面中Zn位点呈空间六边形排布,使片状ZnO在CO_(2)加氢生成CH3OH的反应中表现出更高的活性。

ZnO based catalytic materials can selectively convert CO_(2) into high value-added chemicals such as methanol through hydrogenation,which has attracted wide attention,while their catalytic active center structure and structure-activity relationship still need further research.ZnO was used as a model to study the structure-activity relationship between the catalytic performance and the active sites.Plate ZnO and rod ZnO were prepared by hydrothermal synthesis method in which plate ZnO preferentially exposed(002)facets,while rod shaped ZnO preferentially exposed(100)and(101)facets.At 300℃,the CO_(2) conversion rate and methanol production rate of plate ZnO are 5.8%and 0.22 mmol/(g·h),respectively,higher than those of rod ZnO(1.5%and 0.095 mmol/(g·h)).The in situ IR results show that isolated Zn sites tend to produce CO,while adjacent multiple Zn sites promote the prodution of CH3OH through synergistic effects.The Zn sites in the ZnO(002)facets are arranged in a spatial hexagonal shape,so that the plate ZnO exhibits higher activity in catalyzing CO_(2) hydrogenation to generate CH3OH.