Coke formation and distribution in catalytic conversion of methanol to propene

Coke deposits non-uniformly on zeolite catalysts along fixed bed reactors in MTO, resulting in inhomogeneous deactivation of catalysts. By sequentially connecting multi fixed bed reactors, we achieved mimicking the behavior of different H-ZSM-5 catalyst layers in a single fixed bed reactor. Detecting gas phase molecules over each reactor, and analyzing the coke as well as the catalyst after deactivation allowed us to correlate the coke formation rate over a certain catalyst layer with the local gas phase composition and the loss of catalyst active sites. It is found that most of the coke is formed on the catalyst layers where both olefin and methanol were present. Only small amounts of coke were detected on the catalyst top layers where only methanol/DME were present and on the bottom layers where only hydrocarbons were present. This coke distribution agrees with the hydrogen transfer rate along the catalyst bed, which is higher in presence of both olefin and methanol than in presence of only methanol/DME or only hydrocarbons.