Catalytic hydrolysis of monochlorodifluoromethane over ZnO/ZrO2 catalysts at low temperatures.

Abstract

Monochlorodifluoromethane (HCFC-22) has been identified as a significant contributor to the depletion of the Earth's ozone layer, garnering considerable attention within the scientific community. Consequently, the investigation of Freon degradation has become a central focus of current research efforts. In this study, we opted to employ catalytic hydrolysis as it offers numerous advantages for the degradation of HCFC-22. Specifically, we prepared ZnO/ZrO2 catalysts with hexahedral rod-like structures through citric acid complexation. We examined the impact of various preparation conditions (such as the molar ratio of ZnO to ZrO2, calcination temperature, and calcination time) as well as catalytic hydrolysis conditions (including the amount of catalyst, total flow rate, and catalytic hydrolysis temperature) on the hydrolysis rate of HCFC-22. Characterization of the catalysts was performed using techniques such as XRD, SEM, EDS, TG-DTG, FTIR, N2 adsorption-desorption, CO2-TPD, and NH3-TPD. Our experimental findings revealed the optimal preparation conditions: a catalytic hydrolysis temperature of 100°C, a molar ratio of ZnO to ZrO2 of 0.7, a water bath temperature of 90°C, a roasting temperature of 400°C, and a roasting time of 4h. At a catalytic hydrolysis temperature of 100°C, the hydrolysis rate of HCFC-22 reached 99.81%, with the main hydrolyzed products being HCl, HF, and CO2.