Ammonia storage/release behaviors of the CeSn0.2Mo0.6Ox/TiO2 catalyst in selective catalytic reduction of NO

Abstract

• CeSnMoO x /TiO 2 obtained stable NO removal due to ammonia storage/release. • Excess NO induced ammonia release, the amount reached maximum during 250−300 °C. • Ammonia was mainly stored in physical form and partly by chemical adsorption. • High temperature enhanced ammonia activation and improved ammonia release. This work explored the ammonia storage/release behaviors of the CeSn 0.2 Mo 0.6 O x /TiO 2 catalyst in selective catalytic reduction of NO. Results displayed that the CeSn 0.2 Mo 0.6 O x /TiO 2 performed much higher NO removal rate than the theoretical maximum if the NH 3 /NO ratio was lower than one, which was due to the ammonia storage/release behaviors. The ammonia storing was more likely to occur at low temperatures, and the storage capacity of the catalyst reached 27 μmol m −2 at 50 °C. Moreover, ammonia exists mainly on physical form of temperatures below 250 °C and is adsorbed in weakly acidic sites; while high temperature strengthen activation of strong acid sites, resulting in increasing the ammonia storage at 350 °C. NH 3 -TPD results showed two peaks of ammonia desorption, indicating the weak and strong acid sites of the catalyst. The ammonia storage/release curves at Constant Temperature Flow Field were asymmetric and BET isotherm showed Type H3 hysteresis loop, which was caused by mass transfer in the plate-like pore structure formed by the particle polymerization. The porous structure and highly dispersed active components were beneficial for storing ammonia. The effective utilization ratio of the stored ammonia decreased with the increasing temperature and GHSV.