The Effects of Thermal Modification on the Properties of Zeolitic Imidazolate Framework-8 (ZIF-8) Catalysts in Transesterification

Abstract

Abstract A simple and effective thermal method for modifying Zeolitic Imidazolate Framework-8 (ZIF-8) was introduced to enhance their catalytic activity toward the triglyceride transesterification. The modified ZIF-8 catalysts were characterized for their change in crystallinity and structure using X-ray diffraction (XRD) along with simultaneous thermal analysis (STA), nitrogen adsorption and desorption analysis, field emission scanning electron microscope (FE-SEM). X-ray photoelectron spectroscopy (XPS) was also used to investigate relevant chemical and physical changes that occur after thermal treatment both in air and nitrogen. Results showed that significant improvements in the catalytic activity and stability of the modified ZIF-8 were observed toward the targeted in transesterification. Interestingly, it was found that the catalysts could be used for at least 5 reactions and that the leaching of Zn2+ from modified ZIF-8 during transesterification reaction was negligible when compared to ZIF-8. This study provides a promising approach to enhance the catalytic performance of ZIF-8 by mean of oxidation and provided significant improvement when applied to the transesterification of triglyceride.