CeO2-doped WO3 composite catalyst based on acid site enhancement for diesel exhaust gas denitration

Abstract

Based on the complicated preparation of current diesel vehicle exhaust gas denitration catalysts, an in-situ deposited composite oxide catalyst, CeO2-WO3 mixed oxide catalyst, was prepared by electrodeposition and hydrothermal methods, which was loaded on the titanium mesh and applied to the selective catalytic reduction denitration of diesel vehicle exhaust. Denitration performance of the catalysts was tested by a fixed bed reactor, and the influence of different electrodeposition time of CeO2 was investigated. The results demonstrate that 20 min is the best electrodeposition time of CeO2 (100% NOx conversion at 250–350 °C). The high dispersion of active CeO2 on WO3 promotes the synergistic effects among different components. The as-prepared catalysts were characterized by SEM, XRD, XPS, H2-TPR, NH3-TPD and in-situ DRIFTS. It is evident that Ce3+ is successfully introduced by loading CeO2, which enhances the chemisorption of oxygen. Meanwhile, the increased acidity including both weak acid and medium-strong acid sites of CeO2-WO3 composite catalyst is observed, which improves the co-adsorption of NH3 on Lewis acid and Brønsted acid simultaneously and facilitates the denitration process. Through the characterization by in-situ DRIFTS, it is elucidated that the NH3-SCR reactions are mainly carried out following the Eley-Rideal (E-R) pathway in a medium-temperature range (250–350 °C).