Protagonists in the standard SCR reaction have been caught in the act by modulation excitation IR & XAFS spectroscopy.

The methanol-to-hydrocarbons (MTH) reaction refers collectively to a series of important industrial catalytic processes to produce either olefins (MTO) or gasoline (MTG). Mechanistically, methanol conversion proceeds via a 'pool' of hydrocarbon species. For MTO, these can broadly be delineated into 'desired' lighter olefins and 'undesired' heavier fractions causing deactivation in a matter of hours. The crux in further catalyst optimization is the ability to follow the formation of carbonaceous species during operation. Herein, we report the combined results of an operando Kerr-Gated Raman Spectroscopy study with state-of-the-art operando molecular simulations, which allowed to follow the formation of hydrocarbon species at various stages of methanol conversion. Polyenes are identified as crucial intermediates towards formation of polycyclic aromatic hydrocarbons, with their fate being largely determined by the zeolite topology. Notably, we provide the missing link between active and deactivating species, which allows us to propose potential design rules for future generation catalysts.

Mo/H‐ZSM‐5 has been studied using a combination of operando X‐ray absorption spectroscopy and High Resolution Powder Diffraction in order to study the evolution of Mo species and their location within the zeolite pores. The results indicate that after calcination the majority of the species present are isolated Mo‐oxo species, attached to the zeolite framework at the straight channels. During reaction, Mo is first partially carburized to intermediate MoCxOy species. At longer reaction times Mo fully carburizes detaching from the zeolite and aggregates forming initial Mo1.6C3 clusters; this is coincident with maximum benzene production. The Mo1.6C3 clusters are then observed to grow, predominantly on the outer zeolite surface and this appears to be the primary cause of catalyst deactivation. The deactivation is not only due to a decrease in the amount of active Mo surface but also due to a loss in shape‐selectivity which leads to an increased carbon deposition at the outer shell of the zeolite crystals and eventually to pore blockage.