Characteristics and catalytic properties of agli/sio2 catalysts on different silica supports for oxidative dehydrogenation of ethanol to acetaldehyde

Abstract

This work focuses on investigation of the oxidative dehydrogenation and non-oxidative dehydrogenation of ethanol over AgLi/SiO2 catalysts to produce acetaldehyde by having three different types of silica support, spherical silica particle (small particle size; SPS), medium silica particle size (MPS), and large silica particle size (LPS). The spherical silica particle (SSP) was synthesized using the sol-gel method, whereas SiO2 (MPS) and SiO2 (LPS) were obtained from commercial suppliers. AgLi/SiO2 catalysts were prepared by incipient wetness co-impregnation method. The physicochemical properties of catalysts were analyzed by using several technique such as X-ray diffraction (XRD), N2-physisorption, SEM-EDX, UV-visible spectroscopy, H2-TPR. Moreover, the basicity properties of catalysts were confirmed by CO2 Temperature-programmed desorption (CO2-TPD) technique. The catalytic activity and product distribution were tested by performing both non-oxidative and oxidative dehydrogenation of gas phase ethanol. The reactions were operated at atmospheric pressure with the temperature range of 200-400 °C. It was found that the AgLi/SiO2-SPS catalyst exhibited the highest ethanol conversion (58.35%) and acetaldehyde yield (56.89%) at the temperature of 400 °C for non-oxidative dehydrogenation. In addition, the basicity of catalyst play a strong influence for this reaction. In contrast, the AgLi/SiO2-LPS catalyst exhibited the highest acetaldehyde yield (76.81%) at the temperature of 300 °C for the oxidative dehydrogenation because its higher Agδ+ clusters and Ag0 species due to its high reducibility.