Highly Selective and Stable Production of Aromatics via High-Pressure Methanol Conversion

Abstract

In the current petrochemical market, the global demand for aromatics, especially benzene, toluene, and xylenes (BTXs), has increased sharply. The methanol-to-aromatic conversion (MTA) over ZSM-5 is among the most promising routes to satisfy this ever-growing demand. In this work, we show that high-pressure operation during MTA leads to a large increase in aromatic selectivity while enhancing stability on-stream. Stable operation along with a very high selectivity to aromatics (up to 50%, with 20% BTXs) can be achieved on a commercial high-silica ZSM-5 (SiO2/Al2O3 = 280) at 400 °C, 30 bar total pressure, and WHSV = 8 h–1. The high partial pressure of primary olefins and the promoted methanol-induced hydrogen-transfer pathway result in an exponential increase in aromatization, while the high partial pressure of steam generated via dehydration of methanol leads to in situ coke removal and, therefore, to a much slower deactivation of the zeolite.