Multiple important roles of phosphorus modification on the ZSM-5 in ethanol to olefin reaction: Acidity adjustment, hydrothermal stability and anti-coking

Abstract

The effects of phosphorus doping on the reaction of bioethanol to light olefins catalyzed by HZSM-5 were studied from both catalytic experiments and molecular simulations. P-doping promotes the highest yield of propylene up to 35.0 %. The propylene yield remained above 22.5 % even after 100 h. The introduction of P improves the catalyst acidity and the electronic environment of the active center of HZSM-5, which is beneficial to increase the selectivity of propylene, making the adsorption and conversion reaction of ethanol and the desorption of ethylene and propylene products more favorable. The framework aluminum is stabilized by the phosphate groups outside the framework, so that the framework dealumination is inhibited. The deep polymerization of ethylene is inhibited, and the anti-coking ability is enhanced. The presence of water enhances the hydrothermal stability and inhibit the carbon deposition of P-modified ZSM-5 catalyst, which makes the P-doping ZSM-5 the most promising catalyst for bioethanol conversion applications.