Low-Temperature Oxidative Removal of Formaldehyde Using Oxygen-Vacancy Enhanced Silver-Based Catalyst

Abstract

In this paper, a highly active silver-based catalyst, K-Ag/La-CeO2/Al2O3, was developed for low temperature formaldehyde oxidative removal based on oxygen vacancy theory, as an endeavor to bridge one of the gaps between the laboratory research and practical applications. Oxygen vacancies were generated by doping La2O3 into the CeO2 surface modification layer on an alumina support. They raised the fraction of Ag2O on CeO2 surface, reduced the activation energy from 111 to 74 kJ/mol, enabled the low temperature activity, and increased active sites for fast reaction. The catalyst demonstrated a decent adsorption capacity of 0.39 mmol HCHO/g_cat. in the presence of air at 25 ºC. It completely converted formaldehyde into CO2 and H2O at a temperature higher than 85 ºC and a residence time less than 0.1 second and achieved 4-10% formaldehyde conversion at 25 ºC. In situ DRIFTS suggested that formaldehyde combusted in the presence of the catalyst through a pathway with formic acid and CO as intermediate species. Besides formaldehyde oxidation, this catalyst design approach can also be applied to low temperature combustion of other volatile organic compounds.

Keywords: Formaldehyde, silver-based catalyst, oxygen vacancy, Ceria