Synchronously constructing the optimal redox-acidity of sulfate and RuOx Co-modified CeO2 for catalytic combustion of chlorinated VOCs

Abstract

CeO2-based catalysts are highly active but easily deactivated for the catalytic combustion of chlorinated VOCs (CVOCs), and enhanced redox and acidity are also considered to be effective strategies. However, the screening of practicable modifiers and their preparation method to achieve the promotion and balancing of redox-acidity is still desired. In this work, sulfate and RuOx were simultaneously introduced into CeO2 by a simple co-precipitation method, and the optimal redox-acidity was constructed. The catalytic combustion of 1,2-dichloroethane (DCE) indicated that 2.5Ru-CeO2-S0.05 presented an outstanding oxidation activity and selectivity of chlorinated byproducts and superior cycle and long-term stability (at least 60 h at 280 °C), even in the presence of 5 % H2O. A series of control experiments, such as the introduction methods, the precursors and contents of Ru and sulfate, and their property characterization revealed that the bulk doping of Ru mainly contributed to the promoted activity and durability through more exposed Ce3+/4+ and oxygen vacancies and the rapid removal ability of the inorganic chlorine species via a semi-Deacon reaction pathway, as well as to the formation of chlorinated byproducts. Meanwhile, the synchronous introduction of sulfate as Brønsted acid sites efficiently inhibited these chlorinated byproducts, while its retained redox ability and the enhanced Lewis acid sites owing to the strong electron withdrawing of the sulfate also further promoted DCE oxidation. Moreover, 2.5Ru-CeO2-S0.05 showed a high activity and excellent durability for the catalytic oxidation of ethylene, vinyl chloride and their mixtures with 1,2-DCE. This work provided a demonstration for balancing the oxidation performance and acidity of CeO2-based catalysts, which contributed to the development of applicable catalysts for catalytic oxidation of CVOCs under actual working conditions.