Direct observation of olefin homologations on zeolite ZSM-22 and its implications to methanol to olefin conversion

Towards molecular control of elementary reactions in zeolite catalysis by advanced molecular simulations mimicking operating conditions

“…73 These findings are also clearly reflected in the free energy barriers for benzene and propene methylation reported in Table 1. Indeed, despite the relatively easy proton transfer reflected in the high probability to protonate methanol, the formation of favorable pre-reactive complexes for benzene methylation is hindered by spatial restrictions.…”

“…In the one-dimensional pores of H-ZSM-22 only alkenes were found to be active HP species resulting in the production of branched C 5+ alkenes, [72][73][74][75][76][77][78] whereas aromatics were found to be dominating HP species in H-SAPO-34 and large pore zeolites H-beta and H-SSZ-24. 22,24,[79][80][81][82] A high activity of aromatics is mostly coupled with a high selectivity towards ethene and propene.…”

“…Several experimental studies clearly pointed out that methanol conversion in H-ZSM-22 occurs through the alkene cycle and that aromatic HP species are not active. [73][74][75]77,78,125 Cui et al…”

Comparative study of MTO conversion over SAPO-34, H-ZSM-5 and H-ZSM-22: Correlating catalytic performance and reaction mechanism to zeolite topology

“…Because the olefins were the main products of this reaction and the olefins methylation or cracking reactions over zeolite catalysts have been suggested and proved by several research groups [21][22][23], methanol might be converted to olefins through the mechanism other than aromatic based hydrocarbon pool mechanism, i.e. the olefin methylationcracking reaction cycle.…”

Conversion of methanol over H-ZSM-22: The reaction mechanism and deactivation

“…The incorporation of 12 C atom into the products would predict that the reaction followed hydrocarbon pool mechanism [4,5] and these 12 C-coke species may work as the reaction centers of methanol conversion. Through another reaction route proposed for methanol conversion, olefin methylation-cracking [19,20,[25][26][27] without involving the 12 C-polymethylbenzenes retained in the catalysts, the products generation would be independent of the scrambling of isotopic distribution. However, if both of the two reaction mechanisms were allowed to operate on a specific catalyst, the products from the former reaction route would possibly serve as the initial olefins for the later reaction route, which makes the reaction route determination more difficult from the isotopic distribution.…”