https://pubs.acs.org/doi/10.1021/acs.est.1c05586

Abstract

Ru-based catalysts for catalytic combustion of high-toxicity Cl-containing volatile organic compounds are inclined to produce Cl2 instead of ideal HCl due to the Deacon reaction. We herein reported that the three-dimensionally ordered macroporous (3DOM) WOx-supported RuP nanocatalyst greatly improved HCl selectivity (at 400 °C, increased from 66.0% over Ru/3DOM WOx to 96.4% over RuP/3DOM WOx) and reduced chlorine-containing byproducts for 1,2-dichloroethane (1,2-DCE) oxidation. P-doping enhanced the number of structural hydroxyl groups and Brønsted acid sites. The isotopic 1,2-DCE temperature-programmed desorption experiment in the presence of H218O indicated the generation of a new active oxygen species 16O18O that participated in the reaction. Generally, P-doping and H2O introduction could promote the exchange reaction between Cl and hydroxyl groups, rather than oxygen defects, and then benefit the production of HCl and reduce the generation of other chlorine species or Cl2, via the reaction processes of C2H3Cl → alcohol → aldehyde → carboxylic acids.

Therefore, two strategies were proposed to enhance the stability of a catalyst: (i) Ru metal was used to remove the strongly adsorbed CVOCs from the catalyst surface in the form of chlorine; and (ii) doping some components (e.g., V/Mo/W/P/HZSM-5) increased the Brønsted acid sites of the catalyst and promoted desorption of HCl.(8−13) Among these methods, the doping of phosphorus in different ways could adjust the ratio of the Brønsted and Lewis acidity, and further, promote the catalytic reaction via decreasing the selectivities of the chlorine-containing byproducts.(14−19)