Improvement of Low-Temperature NH<sub>3</sub>–SCR Activity over CeVO<sub>4</sub> Modified by Sm
Yingjie Li, Jinpeng Du, Chunxi Lin, Jinhan Lin, Jianqi Liu, Jieying Cai, Congwei Liu, Zhihua Lian, Wenpo Shan
Abstract
In this study, the Ce 0.8 Sm 0.2 V catalyst, prepared using the coprecipitation method, exhibited excellent NH 3 –SCR activity in a wide temperature range from 175 to 375 °C, even under a high GHSV of 200,000 h –1 . Analysis using X-ray diffraction, Raman, and BET techniques revealed that doping Sm into CeVO 4 enlarged the specific surface area and reduced the crystallite size of the catalyst. The H 2 -TPR and X-ray photoelectron spectroscopy results indicated that the incorporation of Sm improved the redox ability and enhanced the interaction among Ce, Sm, and V. NH 3 -TPD results demonstrated that introducing Sm into CeVO 4 could increase the number of acid sites. All these factors contributed significantly to the enhancement of low-temperature NH 3 –SCR activity. Moreover, adding Sm could increase the number of Lewis acid sites, enhance the adsorption of NO x species, and promote the formation of –NH 2 and NH 4 NO 3 species, which play vital roles in enhancing the SCR activity. The NH 3 –SCR reaction on the Ce 0.8 Sm 0.2 V catalyst followed both Langmuir–Hinshelwood and Eley–Rideal mechanisms.