Abstract:
The durability improvement of Co/HZSM-5 catalysts under hydrothermal pretreatment for selective catalytic reduction of NO by methane was studied. Co/HZSM-5 catalyst is not durable under long steam aging in severe conditions. Therefore, the second metal was introduced into Co/HZSM-5 in order to improve the durability of Co/HZSM-5. It was found that Palladium and Cadmium increased the durability of Co/HZSM-5 more than the other metals because both metals prevent the framework dealumination of zeolite. In addition, the presence of Pd loading amount approximately 0.4 wt.% was appropriate for enhancing durability of Co/ZSM-5. Furthermore, The effect of crystal size on the durability of Co/HZSM-5 was investigated. It was found that the durability of small crystal sizes of Co/HZSM-5 was higher than that of large crystal sizes of Co/HZSM-5. After hydrothermal treatment, the small crystal size catalyst showed a slight decrease in crystallinity and tetrahedralaluminum while the large crystal size catalyst lost crystallinity and tetrahedral aluminum. This indicated that the occurrence of framework dealumination was higher in the large crystal size catalyst.
