Mechanistic Investigation on Catalytic Deoxygenation of Phenol as a Model Compound of Biocrude Under Methane

Abstract

A novel hydrogen-free approach is developed to effectively convert phenolic compounds into aromatics including benzene, toluene, ethylbenzene, and xylene (BTEX), a very important and widely used class of petrochemical intermediates, and naphthalene. High yield and selectivity of BTEX are achieved over Zn modified zeolite catalyst during phenol deoxygenation under a methane environment at 400 °C and 2 MPa. Methane can greatly enhance the liquid yield and selectivity of BTEX, but also improve the catalyst activity. Experimental analysis and mechanistic studies reveal that methane is incorporated into both the methyl group and aromatic ring. The embedding of methane into aromatic compounds is achieved via C-alkylation of phenyl ring, coaromatization with hydrocarbon radicals, and a ring-expansion/contraction mechanism. Liquid- and solid-state NMR investigations make evident the phenyl ring-opening in the reaction. Our mechanistic understanding of this process will provide valuable insights into the chemistry...