Coking Characteristics of Chromium-Exchanged ZSM-5 in Catalytic Combustion of Ethyl Acetate and Benzene in Air

Abstract

The coking characteristics during ethyl acetate and benzene combustion, in the presence and absence of water vapor, are reported. Coked Cr−ZSM-5 was prepared by exposing the catalyst to 32000 ppm of respective VOC at a GHSV of 3800 h-1 at 400 °C and with the addition of 9000 ppm of water vapor in humid feed. Stable residual activity at longer time on stream suggested that organic combustion and coking occurred at different sites. More coke was formed during ethyl acetate combustion than benzene. Water vapor promoted monolayer coke formation but weakened the formation of whisker-type coke in the combustion of ethyl acetate. Coke obtained from ethyl acetate reaction was made up of oxygenated aromatics which were softer but caused higher deactivation. It formed on Bronsted acid sites and silanols while that of benzene reaction formed preferentially on Bronsted acid sites. Softer coke formed was below 300 and 400 °C for ethyl acetate and benzene, respectively.