An efficient way to use CO2 as chemical feedstock by coupling with alkanes

ABSTRACT The most promising method to eliminate CO 2 is to find large-scale and value-added applications of CO 2 as a carbon resource. However, the utilization of CO 2 as feedstock for basic chemicals has long been a great challenge owing to its high thermodynamic stability. Herein, we report the coupling conversion of CO 2 with light alkanes over the HZSM-5 zeolite with much higher aromatic selectivity than light alkanes as the only reactant. A CO 2 conversion of 17.5% and n -butane conversion of 100% with aromatic selectivity of 80% could be achieved by the coupling reaction at the CO 2 to n -butane ratio of 0.475, in which CO 2 not only acted as an agent for balancing hydrogen in the reaction but also partly (~25%) incorporated into the aromatic products. Methyl-substituted lactones (MLTOs) and methyl-substituted cycloalkenones (MCEOs) were identified as key intermediates during the coupling reaction. 13 C isotope labeling experiments, 13 C solid-state NMR, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory (DFT)calculations revealed that CO 2 could react with carbonium ions generated from alkane cracking to form MLTOs, which could further get converted into MCEOs, thus generating aromatic compounds . This coupling reaction provides guidance for the direct utilization of CO 2 to produce value-added chemicals with the simultaneous transformation of light alkanes.