Reactivation of catalysts for methanol-to-hydrocarbons conversion with hydrogen

Abstract

Catalyst coking is one of the key challenges in hydrocarbons processing. Herein, we studied the potential of reacting coke deposits with hydrogen to regenerate the methanol–to–hydrocarbons (MTH) performance of archetypical ZSM-5 catalysts exhibiting low-to-medium Si/Al atomic ratios (14–39). The reactivation with hydrogen is substantially enhanced at elevated pressures (20–30 bar), restoring significant part of the MTH activity (>85%) and turnover capacity (>30%) at 753–823 K. Decoking is particularly efficient for the aluminum-rich catalyst, removing up to 96% of coke and attaining the performance comparable to conventional coke combustion. X-ray diffraction, Raman, infrared, nuclear magnetic resonance, and X-ray photoelectron spectroscopic analyses revealed that hydrogen eliminates internal and external coke from the catalyst with low Si/Al ratio, and internal coke from the silicon-richer materials. Hydrogen treatments yield light hydrocarbons (e.g., methane and ethane) and aromatics (e.g., methylated benzenes) offering thus a route for valorizing coke that can be exploited in other processes.