Volume 3, No. 1, June 2003, Pages 61-73 PDF(288 KB)
Selective Catalytic Reduction of NO by Methane on Copper Catalysts: the Effects of Modifying the Catalysts with Acids on γ-alumina
Jie-Chung Lou, Chang-Mao Hung, Ling-Hsuan Huang
Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC
This work compares the performance of copper catalysts modified with that of acids. Hence, γ-alumina is used to support the catalyst in the selective catalytic reduction of nitric oxide by hydrocarbons (HC-SCR) using methane at temperatures from 623-1023 K in the presence of oxygen. The copper catalysts were prepared by the incipient wet impregnation of a modified support of γ-alumina with copper nitrate, and by modifying the using nitric, acetic and phosphoric acids, respectively. The effectiveness of the transformation with nitric oxide over the catalysts, determined by comparing the conversion of nitric oxide with non-modified Cu/γ-Al2O3, to that by modified Cu/γ-Al2O3, implied that the reduction of transformation nitric oxide was most efficient when the catalyst modified with nitric acid. Modifying a copper catalyst with nitric acid markedly was found to increase the efficiency of reduction, whereas treatment with acetic and phosphoric acids did not promote the reduction of NO. However, a higher concentration of nitric acid corresponds to a higher efficiency of transformation nitric oxide; thus, converting nitric oxide using the catalyst modified with nitric acid is favored. Pre-treating the support γ-alumina with a higher concentration of acid solution promotes higher activity and greater acidity of the transforming nitric oxide reaction over a copper catalyst, because such pretreatment with acid enlarges the pores in the support, increasing the internal mass transfer and the reactivity over the catalyst. Notably, the presence of Cu (I) and Cu (II) at active sites may also affect the efficiency of the transformative reaction with nitric oxide. When the inlet gas is methane, the corresponding efficiency of the transformation nitric oxide shows that methane is an effective reducing agent.
Nitric oxide; Acid modified; HC-SCR; Methane; Reducing agent.