Abstract: It is important to develop cheap, environmentally friendly and efficient transition metal molecular sieve system for catalytic dehydrogenation of ethane in order to supplement the traditional petroleum route for olefin production. Metal ions anchored to Br?nsted acid sites in zeolite by ion exchange method showed unique C—H and C—C bond-selective activation. The effects of the compatibility of a series of transition metals (Fe, Co, Ni, Cu, Zn and Mn) with different types of molecular sieves (MOR, β, Y, MCM-22, MCM-41, SAPO-11, SAPO-34, USY and ZSM-5) on the catalytic dehydrogenation of ethane were investigated by ion exchange method. The results of X-ray diffraction, ultraviolet and visible spectrophotometry and H2-temperature programmed reduction characterizations showed that the metal ions at the Bronsted acid site were highly dispersed and resistant to reduction. The experimental results and density functional theory calculations showed that Co had excellent potential for selective activation of C—H bonds, but the product distribution still depended on the type and properties of molecular sieve. The selectivity of ethylene could be close to 100% on the zeolite with suitable pore size, otherwise the dehydrogenated products were prone to secondary reaction at the remaining Bronsted acid site to form aromatics and carbon deposits.

Key words: transition metal, zeolite, ion exchange, ethane catalytic dehydrogenation, C—H bond activation