Formation of HCHO, CO and H2 by methane oxidation with O2 over Cu catalysts stabilized in silicoaluminophosphates

Abstract

The catalytic performance of Cu catalysts supported on SAPO34 (denoted as Cu/SAPO) for methane oxidation with O₂ has been investigated in detail. Cu/SAPO catalysts formed H₂ in addition to CO and HCHO during methane oxidation in the temperature range from 773 and 923 K, while the other 3d transition metal catalysts such as V, Cr, Mn, Fe, Co and Ni were less active for the formation of these products. The formation of HCHO, H₂ and CO was also confirmed during the reaction over Cu catalysts supported on zeolites different from SAPO34, such as mordenite, faujasite, chabazite, and beta-zeolite, but the yields of these products, especially the H₂ yield in the reaction over the Cu/SAPO catalyst, were significantly higher than those over other zeolite-supported Cu catalysts. In the oxidation over Cu/SAPO catalysts at 923 K, the yields of H₂, CO, and HCHO reached 2.2, 5.4, and 0.7%, respectively, at a methane conversion of 8.2%. These Cu catalysts were characterized by XRD patterns and in situ UV-vis spectra. Highly dispersed Cu²⁺ species stabilized in SAPO34 were the active sites for methane oxidation, which were reduced to Cu⁺ species by methane and oxidized to Cu²⁺ by O₂ to facilitate the reaction.