The methanol-to-hydrocarbons (MTH) process is an industrially relevant method to produce valuable light olefins such as propylene. One of the ways to enhance propylene selectivity is to modify zeolite catalysts with alkaline earth cations. The underlying mechanistic aspects of this type of promotion are not well understood. Here, we study the interaction of Ca2+ with reaction intermediates and products formed during the MTH reaction. Using transient kinetic and spectroscopic tools, we find strong indications that the selectivity differences between Ca/ZSM-5 and HZSM-5 are related to the different local environment inside the pores due to the presence of Ca2+. In particular, Ca/ZSM-5 strongly retains water, hydrocarbons, and oxygenates, which occupy as much as 10% of the micropores during the ongoing MTH reaction. This change in the effective pore geometry affects the formation of hydrocarbon pool components and in this way directs the MTH reaction toward the olefin cycle.

A methanethiol-to-olefins (MtTO) equivalent of methanol-to-olefins (MTO) chemistry is demonstrated. CH3SH can be converted to ethylene and propylene in a similar manner as CH3OH over SSZ-13 zeolite involving a hydrocarbon...

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Nanocrystals of zeolites with shortened diffusional pathways compared to bulk counterparts are attractive catalysts, but their direct synthesis often remains challenging and expensive. Here, we describe the utility of p-phenylenedimethylene−bis(trimethylammonium) dichloride, an organic diquaternary ammonium compound that can be easily prepared, as an effective organic structuredirecting agent (OSDA) for obtaining several zeolites composed of agglomerated nanocrystals. By modifying the gel composition (NaOH/ Si and Si/Al ratios) and crystallization time, synthesis can be tuned to obtain mordenite, EU-1, and ZSM-12 zeolites. 13 C NMR spectra of the occluded OSDA reveal subtle differences in host−guest interactions between the OSDA and the respective zeolites, which derives from the flexibility of the OSDA. The relatively strong interaction between the OSDA and inorganic aluminosilicate precursor species during the induction period explains how small zeolite nanocrystals are obtained. Nanosized EU-1 and ZSM-12 significantly outperform their corresponding bulk counterparts as acid catalysts in the methanol-to-hydrocarbons reaction and the alkylation of benzene with benzyl alcohol, respectively.

Direct nonoxidative coupling is a promising route for methane upgrading, yet its commercialization is hindered by the lack of efficient catalysts. Pt/CeO2 catalysts with isolated Pt species have attracted an increasing amount of interest in recent years. Herein, we studied the catalytic role and evolution of isolated Pt centers on CeO2 prepared by flame spray pyrolysis under the harsh reaction conditions of nonoxidative methane coupling. During the reaction at 800 °C, the isolated Pt sites sinter, leading to a loss of the ethylene and ethane yield. The agglomerated Pt can be redispersed by using an in situ regeneration strategy in oxygen. We found that isolated Pt centers are able to activate methane only at the initial reaction stage, and the CePt5 alloy acts as the active phase in the prolonged reaction.