Microwave-Assisted Biosynthesis of Ag/ZrO2 Catalyst with Excellent Activity toward Selective Oxidation of 1,2-Propanediol

In the biorefining process, polyols are important intermediates, and the oxidation of polyols toward other value added products is of great significance. This work describes a green and facile biosynthesis method for the preparation of Ag/ZrO2 catalyst for selective oxidation of 1,2-propanediol (a typical polyol). Cinnamomum comphora (CC) leaf extract was employed as the reducing and capping agent for the preparation of Ag nanoparticles (NPs) with the assistance of microwave irradiation. The main reducing agents were identified as polyphenols by Fourier transform infrared spectroscopic analysis of CC extracts before and after reaction. After electrostatic adsorption, the NPs were anchored onto the support ZrO2. The Ag/ZrO2 catalysts were found with good dispersity and showed excellent activity toward selective oxidation of 1,2-propanediol. The effects of the preparation conditions on catalyst activity were studied; the optimal condition was obtained (microwave time of 4 min, CC concentration of 12 g/L and Ag loading of 5%). Since the natural capping agents are easy to remove, the catalysts need no calcination treatment before catalytic reaction. Thus, the microwave-assisted biosynthesis appears to be environmentally benign as neither expensive chemicals nor intensive energy consumption is engaged.