Enhancing the aromatic selectivity of cyclohexane aromatization by CO_(2)coupling

Improving the aromatic selectivity in the alkane aromatization process is of great importance for its practical utilization but challenge to make because the high H/C ratio of alkanes would lead to a serious hydrogen transfer process and a large amount of light alkanes.Herein,CO_(2)is introduced into the cyclohexane conversion process on the HZSM-5 zeolite,which can improve the aromatic selectivity.By optimizing the reaction conditions,an improved aromatic(benzene,toluene,xylene,and C9+)selectivity of 48.2%can be obtained at the conditions of 2.7 MPa(CO_(2)),450℃,and 1.7 h^(−1),which is better than that without CO_(2)(aromatic selectivity=43.2%).In situ transmission Fourier transform infrared spectroscopy spectra illustrate that many oxygenated chemical intermediates(e.g.,carboxylic acid,anhydride,unsaturated aldehydes/ketones or ketene)would be formed during the cyclohexane conversion process in the presence of CO_(2).13C isotope labeling experimental results demonstrate that CO_(2)can enter into the aromatics through the formation of oxygenated chemical intermediates and thereby improve the aromatic selectivity.This study may open a green,economic,and promising way to improve the aromatic selectivity for alkane aromatization process.