Controlled electropositive catalytic sites on zeolites for achieving high CH3Cl selectivity via electrophilic CH4 chlorination using Cl2

Abstract

The spontaneous homolytic Cl₂ cleavage to two reactive chlorine radicals is useful for activating the C–H bond in CH₄ to produce various chlorinated products (CH₃Cl, CH₂Cl₂, CHCl₃, and CCl₄), but it is noncatalytic and uncontrollable. Herein, zeolites with controlled electropositive Lewis acidic sites originating from transition metal cations with various oxidation states successfully promote the electrophilic CH₄ chlorination with suppressing the radical pathway, which achieved nearly 100% selectivity to a desirable monochlorinated product (CH₃Cl). The experimental results were clearly interpreted based on the selected catalytic descriptors calculated by the DFT method, in which the calculated Cl₂ adsorption energy to the catalytic sites, and LUMO energy levels of transition metal cations showed strong correlations with conversion of reactants and the CH₃Cl selectivity. Consequently, Zn²⁺-incorporated zeolite (ZnHY) achieved nearly 100% CH₃Cl selectivity without deactivation. The comprehensive experimental and theoretical investigations offer valuable insights for the design of zeolite-based catalysts promoting electrophilic CH₄ chlorination using Cl₂.