Abstract
The behaviour of a HZSM-5 zeolite (SiO2/Al2O3=30) in several time treatments with 0.2M NaOH solution has been studied for the transformation of bioethanol into hydrocarbons in an isothermal fixed bed reactor and in the 225–425°C range. A short treatment (for 10min) decreases the acid strength of the sites from 135kJ(mol of NH3)−1 to 125kJ(mol of NH3)−1, which is effective for increasing the selectivity of propene and butenes and for attenuating the deactivation by coke. This catalyst allows obtaining a yield of 30wt% of propene+butanes at 400°C with 136(g of catalyst)h(gethanol)−1 and a feed of ethanol/water with 5wt% water. The operation in reaction–regeneration cycles can be carried out continuously without irreversible deactivation of the catalyst, which means not exceeding extreme conditions in the reaction step: 375°C and 400°C for water contents in the feed of 75wt% and 5wt%, respectively. More severe treatments decrease the hydrothermal stability of the zeolite.
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