Tracking the Impact of Koch‐Carbonylated Organics During the Zeolite ZSM‐5 Catalyzed Methanol‐to‐Hydrocarbons Process

Abstract

A methanol‐based economy offers an efficient solution to current energy transition challenges, where the zeolite‐catalyzed methanol‐to‐hydrocarbons (MTH) process would be a key enabler in yielding synthetic fuels/chemicals from renewable sources. Despite its original discovery over half a century ago over the zeolite ZSM‐5, the practical application of this process in a CO2‐neutral scenario has faced several obstacles. One prominent challenge has been the intricate mechanistic complexities inherent in the MTH process over the zeolite ZSM‐5, impeding its widespread adoption. This work takes a significant step forward by providing critical insights that bridge the gap in our understanding of the MTH process. It accomplishes this by connecting the (Koch‐carbonylation‐led) direct and dual cycle mechanisms, which operate during the early and steady‐state phases of MTH catalysis, respectively. To unravel these mechanistic intricacies, we have performed catalytic and operando (i.e., UV‐Vis coupled with an online mass spectrometer) and solid‐state NMR spectroscopic‐based investigations on the MTH process, involving co‐feeding methanol and acetone (cf. a key Koch‐carbonylated species), including selective isotope‐labeling studies. Our iterative research approach revealed that (Koch‐)carbonyl group selectively promotes the side‐chain mechanism within the arene cycle of the dual cycle mechanism, impacting the preferential formation of BTX fraction (i.e., benzene‐toluene‐xylene) primarily.