Modeling of the deactivation kinetics for the combustion of ethyl acetate and benzene present in the air stream over ZSM-5 catalyst loaded with chromium

Abstract

Deactivation kinetics of chromium exchanged ZSM-5 (Cr-ZSM-5, Si/Al=240) catalyst by coking during the combustion of ethyl acetate (EAc) and benzene (Bz) present in the air stream is reported. Lumped coking deactivation model (LCDM), monolayer–multilayer coking deactivation model (MMDM) and heterogeneous surface coking deactivation model (HSDM) are used for the analysis of deactivation process. Coked Cr-ZSM-5 was prepared by exposing the catalyst to 32,000 ppm of each organic at gas hourly space velocity (GHSV) of 3800 h −1 and temperature 400 °C for a period of 12 h. The activity data were obtained with 2000 ppm of each organic at 400 °C and GHSV of 78,900 h −1. HSDM accurately predicted progressive coke content, activity with time-on-stream and profiles of activity–coke content for both organics. In line with experimental observations, the model predicted faster activity drop with lower residual activity during the combustion of ethyl acetate. The combustion reaction of ethyl acetate and benzene could take place over both coking sites ( S c) and metal sites ( S t) but, the role of S t was more dominant especially in benzene combustion.