Effects of different methods of introducing Mo on denitration performance and anti-SO2 poisoning performance of CeO2

Abstract

Cerium-based catalysts are very attractive for the catalytic abatement of nitrogen oxides (NOx) emitted from stationary sources. However, the main challenge is still achieving satisfactory catalytic activity in the low-temperature range and tolerance to SO2 poisoning. In the present work, two series of Mo-modified CeO2 catalysts were respectively obtained through a wet impregnation method (Mo-CeO2) and a co-precipitation method (MoCe-cp), and the roles of the Mo species were systematically investigated. Activity tests showed that the Mo-CeO2 catalyst displayed much higher NO conversion at low temperature and anti-SO2 ability than MoCe-cp. The optimal Mo-CeO2 catalyst displayed over 80% NO elimination efficiency even at 150 °C and remarkable SO2 resistance at 250 °C (nearly no activity loss after 40 h test). The characterization results indicated that the introduced Mo species were highly dispersed on the Mo-CeO2 catalyst surface, thereby providing more Brønsted acid sites and inhibiting the formation of stable adsorbed NOx species. These factors synergistically promote the selective catalytic reduction (SCR) reaction in accordance with the Eley-Rideal (E-R) reaction path on the Mo-CeO2 catalyst. Additionally, the molybdenum surface could protect CeO2 from SO2 poisoning; thus, the reducibility of the Mo-CeO2 catalyst declined slightly to an adequate level after sulfation. The results in this work indicate that surface modification with Mo species may be a simple method of developing highly efficient cerium-based SCR catalysts with superior SO2 durability.