Selective methanethiol-to-olefins conversion over HSSZ-13 zeolite

Abstract

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...

Mechanism of Hydrocarbon Formation in Methane and Methanol Conversion over Copper-Containing Mordenite

“…We speculate that the signal at 90 ppm corresponds to carbon atoms in ethylene adsorbed over Cu I sites. Notably, the chemical shift is lower as compared to typical values corresponding to carbon atoms in gaseous olefinic compounds (125–140 ppm). ,− At the same time, a strong shift toward a higher field in 13 C NMR is characteristic for complexes of Cu I with ethylene. − Such an assignment is also in line with the recent work by Lashchinskaya et al where signals at 88 and 112 ppm were attributed to propylene adsorbed over copper-containing zeolite . Possibly, ethylene, initially produced in the MTH process, adsorbs on Cu I sites, leading to the signal at 90 ppm (Scheme , Pathway V).…”

“…The formation of a HCP is an essential step required for the conversion of methanol to hydrocarbons, and we confirm that this process takes place during the conversion of methanol and methoxy species over Cu I ‑containing zeolite (Scheme , Pathway III). In contrast to the signals at 134 ppm and 154 ppm, a signal at 114 ppm was not observed before in any MTH process over copper-free zeolites, ,− while in the recent study by Lashchinskaya et al, signals at 88 and 112 ppm were attributed to propylene absorbed over Cu I sites . Based on this, we assign the signal at 114 ppm to propylene adsorbed over Cu I .…”

“…Finally, in the spectra measured after 1800 s of reaction at 773 K, pronounced broad signals at 154 and 114 ppm and a weak signal at 134 ppm are present. The first signal is characteristic of methyl-substituted cyclopentenyl cations ,− (Table S2). These compounds were identified as the key intermediates in the MTH process, as they act as co-catalysts forming the so-called HCP species. , The signal at 134 ppm corresponds to carbon atoms in methyl-substituted benzenes, ,,,, which can act as the active species in the HCP mechanism.…”

Methods for Studies of Reactions on Zeolite Catalysts Occurring by the Hydrocarbon Pool Mechanism

“…The HCP mechanism underlies the conversion of methanol into hydrocarbons (MTH) and olefins (MTO) [2,21,22]. Similar mechanisms have been also established for the transformations of methyl halides [3] and methanethiol [4] into higher hydrocarbons, conversion of ethylene into propylene [5], and aromatization of furans [6] and light alkanes [7,8] on zeolites. The general features of the chemistry of reactions proceeding according to the HCP mechanism are the appearance of cocatalytic hydrocarbon intermediates inside the microporous structure of zeolites, the presence of an induction period when these intermediates are formed, and strong dependence of the stability of intermediates and products on the catalyst pore topology [6].…”

“…It is worthwhile to note that the decrease in CH 3 SH conversion over time for H-SSZ-13 resulted in a decrease in the yield of light olefins and higher total coke build-up selectivity. Despite the similar distributions of the products obtained in the MTO and MtTO reactions on H-SSZ-13, the rate of its deactivation in the MtTO reaction is higher, which is associated with faster formation of deactivating particles, which are blocked inside the catalyst pores because of their size and cannot diffuse to the outer surface [4,15].…”