The nature of medium acidity in [CuO/ZnO/ZrO2]SAPO-34 hybrid catalyst for CO2 hydrogenation: study of the interactions between metal oxides and acid sites in zeolite

Abstract

This chapter presents the study of a direct synthesis of hydrocarbons through carbon dioxide hydrogenation over hybrid catalysts composed of methanol synthesis catalysts (copper (II) oxide or zinc oxide) and zeolites (HZSM-5, SAPO-34). New peak around 350°C due to the medium acidity appear during the ammonia (NH3)-temperature-programmed desorption (TPD) of hybrid catalyst, and the areas of these new peaks are well correlated with the hydrocarbon yields in CO2 hydrogenation. The appearance of the new NH3-TPD peak is ascribed to the interaction between copper (II) oxide or zinc oxide and SAPO-34, which leads to the mutual changes in the acidity of zeolite and the reducibility of metal oxides.