The remarkable promotional effect of Sn on CeVO4 catalyst for wide temperature NH3-SCR process by citric acid-assisted solvothermal synthesis and post-hydrothermal treatment

A series of CeVO4 catalysts were prepared by citric acid-assisted solvothermal synthesis and hydrothermal methods. The Sn-CeVO4 exhibited superior NH3-SCR performance since abundant of cerium vanadate coexisting with a spot of CeO2 and a mass of surface acid sites forming in the solvothermal synthesis process. A number of structural defects increased after Sn was doped into the CeVO4 system, and the electron transfer between cerium and vanadium was also accelerated significantly. Thus the temperature window of Sn-CeVO4 was broadened and its tolerance to H2O and SO2 was improved dramatically. In addition, post-hydrothermal treatment was essential for the fresh CeVO4 catalyst to achieve better catalytic activity. The results illustrated that surface reconstruction and the chemical states of surface active species occurred slight changes after the post-hydrothermal treatment, which was conducive to expose more active sites to enhance its catalytic activity. Totally, the large surface area of cerium vanadate, strong interaction among tin, cerium and vanadium, large number of acid sites and oxygen vacancies, structural defects as well as exposed active sites were beneficial to the improvement of Sn-CeVO4 catalytic performance in NH3-SCR process.