Alkylation of Benzene with Methane over ZnZSM-5 Zeolites Studied with Solid-State NMR Spectroscopy

Abstract

Alkylation of benzene with methane was studied under oxidization condition over ZnZSM-5 zeolites by using in situ solid-state NMR spectroscopy and GC-MS analysis. The experimental results indicate that the alkylation reaction occurs with selective formation of toluene at temperatures of 523–623 K using O2 or N2O as the oxidant. Using 13C isotope labeled reactants, the conversions of methane and benzene were independently monitored, and their respective role in the reaction was determined. It was found by NMR spectroscopy that methane was first activated into methoxy species and zinc methyl intermediates. As an electrophilic agent, the methyl group of methoxy species could directly attack phenyl ring to produce toluene via electrophilic substitution reaction, while the zinc methyl species was not directly involved in the alkylation reaction. However, the similar nature of zinc methyl species (Zn–CH3) to organozinc compounds allowed the facile oxidization of zinc methyl species (Zn–CH3) into methoxy species. As confirmed by GC-MS experiments, methane exclusively provided the methyl group of toluene product while benzene afforded the phenyl ring. Experimental results also indicated that neither methane nor benzene alone could generate toluene.

Recent Advances in the Synthesis, Characterization and Application of Zn+‐containing Heterogeneous Catalysts

“…In addition to the activation of methane, ZnZSM-5 catalysts also show good catalytic ability for the alkylation of benzene with methane using O 2 or N 2 O as the oxidant at temperatures between 523-623 K ( Figure 18 A). [ 70 ] In situ solid-state NMR spectroscopy, 13 C isotope labeled reactants, and GC-MS analysis were used to explore the reaction process. In this reaction, methane was activated into methoxy species and zinc methyl intermediates on ZnZSM-5.…”

Promoting effects of MgO and Pd modification on the catalytic performance of hierarchical porous ZSM-5 for catalyzing benzene alkylation with methanol

“…[1][2][3] Studies showed that hierarchical porous ZSM-5 could overcome the limitation of micropores to achieve better catalytic performance. [1][2][3] Studies showed that hierarchical porous ZSM-5 could overcome the limitation of micropores to achieve better catalytic performance.…”

Catalytic Natural Gas Utilization on Unconventional Oil Upgrading

“…In addition to the aromatization of methane, other reactions such as the reaction between methane and CO 2 [67] and the one between methane and CO [68] have also been studied using SSNMR. The methane activation pathways in these scenarios help reveal the activation mechanism of methane.…”