Co-reaction of methanol with butene over a high-silica H-ZSM-5 catalyst

Abstract

Co-reaction of methanol and butene was investigated over a high-silica H-ZSM-5 catalyst. It was found that the olefin methylation-cracking and butene dimerization-cracking routes co-occurred, and their contributions depended on the methanol/butene ratio. When more methanol was fed, the olefin methylation-cracking route played a dominant role, producing more propene. An increase in butene amount promoted butene dimerization and the subsequent cracking pathway, improving pentene yield at the expense of ethene, propene, and aromatics. A strong interaction of methanol with butene was observed at a methanol/butene molar ratio of 4:1, resulting in the highest propene selectivity. The spent catalysts were systematically studied by N2 adsorption/desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, diffuse reflectance UV–vis spectroscopy, Raman spectroscopy and temperature-programmed oxidation techniques. The results reveal that the coke species are mainly formed on the external surface through aromatics methylation and aromatics alkylation with alkene pathways. The increase in the catalytic stability from co-feeding butene is attributed to alleviation of aromatics formation and suppression of the aromatics methylation coking route.