Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O<sub>2</sub> by Isotopic C<sup>13</sup>O Tracing Methods
Yarong Bai, Shan Gao, Yuxin Sun, Weilong Ouyang, Yi Zhou, Haiqiang Wang, Zhongbiao Wu
Abstract
The development of efficient catalysts for the selective catalytic reduction of NO by CO (CO-SCR) in the presence of O 2 is highly desirable for controlling the emission of toxic gases from tailpipes. Here, a bimetallic IrRu/ZSM-5 catalyst was prepared for the selective catalytic reduction of NO by CO in the presence of O 2 (5%) for the low-temperature treatment of exhaust gas. IrRu/ZSM-5 afforded 90% NO x conversion in the range of 225–250 °C and maintained 90% NO x conversion after 12 h of reaction. Ru addition inhibited agglomeration of the Ir particles during the reduction process and provided more active sites for NO adsorption. Isotopic C 13 O tracing and in situ diffuse reflectance infrared Fourier-transform spectroscopy experiments were used to elucidate the CO-SCR mechanism in the absence or presence of O 2 . NCO could easily form on the surface of catalysts in the absence of O 2, whereas NCO formation has been inhibited owing to the quick consumption of CO in the presence of O 2 . Moreover, some byproducts such as N 2 O and NO 2 are generated in the presence of O 2 . Finally, a possible mechanism for CO-SCR under different conditions was proposed based on in situ experiments and physicochemical analyses.