Ethanol conversion into olefins and aromatics over HZSM-5 zeolite: Influence of reaction conditions and surface reaction studies

Ethanol is an important renewable feedstock that represents an attractive alternative resource for petrochemical industry. In this work, the conversion of ethanol into hydrocarbons, particularly light olefins and aromatics, catalyzed by HZSM-5 was studied under different conditions of temperature (300-500 degrees C), partial pressure of ethanol (0.04-0.35 atm), and space velocity (165-0.65 g(ethanol) g(cat)(-1)h(-1)). At 500 degrees C and partial pressure of ethanol equal to 0.12 atm, the formation of propene was favored by an intermediate space velocity (6.5 g(ethanol) g(cat)(-1) h(-1)), whereas aromatics were favored by the lowest space velocity (0.65 g(ethanol) g(cat)(-1) h(-1)). The reaction route inferred from the catalytic tests was consistent with that found in the literature and was supported by the surface reaction studies performed by TPD of ethanol and TPSR. In situ DRIFTS of adsorbed ethanol confirmed that the alcohol is adsorbed as ethoxy species on the Bronsted acid sites of the zeolite. With the increase in temperature, the adsorbed ethoxy species form diethyl ether and subsequently ethene confirming that the conversion of ethanol into ethene involves two consecutive steps. (C) 2016 Elsevier B.V. All rights reserved.