One-step conversion of lignin-derived alkylphenols to light arenes by co-breaking of C–O and C–C bonds

Abstract

The conversion of lignin-derived alkylphenols to light arenes by a one-step reaction is still a challenge. A ‘shortcut’ route to transform alkylphenols via the co-breaking of C–O and C–C bonds is presented in this paper. The catalytic transformation of 4-ethylphenol in the presence of H₂ was used to test the breaking of C–O and C–C bonds. It was found that the conversion of 4-ethylphenol was nearly 100%, and the main products were light arenes (benzene and toluene) and ethylbenzene under the catalysis of Cr₂O₃/Al₂O₃. The conversion of 4-ethylphenol and the selectivity of the products were significantly influenced by the reaction temperature. The selectivity for light arenes reached 55.7% and the selectivity for overall arenes was as high as 84.0% under suitable reaction conditions. Such results confirmed that the co-breaking of the C–O and C–C bonds of 4-ethylphenol on a single catalyst by one step was achieved with high efficiency. The adsorption configuration of the 4-ethylphenol molecule on the catalyst played an important role in the breaking of the C–O and C–C bonds. Two special adsorption configurations of 4-ethylphenol, including a parallel adsorption and a vertical adsorption, might exist in the reaction process, as revealed by DFT calculations. They were related to the breaking of C–O and C–C bonds, respectively. A path for the hydrogenation reaction of 4-ethylphenol on Cr₂O₃/Al₂O₃ was proposed. Furthermore, the co-breaking of the C–O and C–C bonds was also achieved in the hydrogenation reactions of several alkylphenols.