Production of ethylene from hydrous ethanol on H-ZSM-5 under mild conditions

Due to the dramatic rise in the use of ethers as fuel oxygenates, an alternative process far the production of ethyl tert-butyl ether (ETBE) based solely on biomass-derived ethanol feedstock is proposed. The first step in this process is ethanol dehydration an H-ZSM-5 to produce ethylene. Hydrous ethanol is a particularly attractive feedstock for this step since the production of anhydrous ethanol is very energy/cost intensive. in fact, the presence of water in the ethanol feed enhances the steady-state activity. and selectivity of M-ZSM-5 catalysts, Reaction kinetic data were collected in a microreactor at temperatures between 413 and 493 K, at ethanol partial pressures of less than 0.7 atm, and at water feed molar ratios of less than 0.25, A sharp initial decline in catalyst activity observed within a few minutes on stream was attributed to the formation of ''low-temperature coke'' from ethylene oligomerization. Deactivation occurred at a much slower rate after 100 min on stream, allowing near-steady-state data to be collected, Water in the ethanol feed enhanced the steady-state catalytic activity and ethylene selectivity by moderating the acidity of the catalytic sites, resulting in less extensive deactivation due to caking.