Oxalic acid-mediated regeneration strategy and mechanism of phosphorus poisoned CeO2/TiO2 catalysts for selective catalytic reduction of NOx with NH3

Abstract

The development of the regeneration strategies can extend the service life of deactivated catalysts and improve resource efficiency. In this work, an acid treatment method was proposed to regenerate the P-poisoned CeO2/TiO2 (PCeTi) catalyst for ammonia selective catalytic reduction (NH3-SCR) of NOx. Catalytic activity test results showed that acid treatment could achieve the efficient regeneration of PCeTi catalyst, the regenerated PCeTi mediated with oxalic acid (PCeTi-OA) catalyst showed a 90% mineralization temperature (T90) of 236 °C (T90 for fresh CeTi was 232 °C) and retained the promotional effect of P species at the high temperature (>350 °C). The characterization results showed that most of the P species on the PCeTi catalyst were removed after regeneration, which restored the majority of the original Ce-O active structure, thereby promoting the Ce4+/Ce3+ redox cycling and inducing the formation of new oxygen vacancies. At the same time, the residual P-O structures and new oxygen vacancies could provide a large amount of acid sites, which was favorable for the adsorption and activation of NH3. The recovered redox properties and the increased surface acidity of the PCeTi-OA catalyst were responsible for its recovered low temperature activity and superior high temperature activity, respectively.