The Impact of Binder Activity on Methanol-to-Hydrocarbons Conversion

The performance of technical zeolite catalysts in industrial processes such as methanol-to-hydrocarbon (MTH) conversion is strongly influenced by their binder component, the mechanism of action of which remains incompletely understood. Through a combination of catalytic testing and analysis of surface and gas-phase intermediates using infrared and photoelectron photoion coincidence spectroscopies, we demonstrate that commonly used binder materials, alumina, silica, and kaolin, catalyze methanol transformations that affect the MTH conversion over zeolites. While alumina promotes deep dehydrogenation to carbon monoxide and hydrogen, silica and kaolin favor hydrogen transfer, yielding methane and formaldehyde. Furthermore, the formation of C2+ hydrocarbons was detected over all binders, suggesting that induction of the MTH reaction does not necessarily require micropore confinement and that it may involve Lewis acid sites. Importantly, the formaldehyde evolution activity of binders correlates with their impact on the coking propensity of a ZSM-5 catalyst and alteration of product distribution, indicating that the hydrogen transfer activity of binders has a substantial contribution to the binder effects in the MTH conversion. The findings reveal that binders are not mere spectators in the MTH conversion and that besides solid binder-zeolite reaction, the catalytic activity of binders has an impact on the performance of technical catalysts.