Enhancing stability and coaromatization of n-hexane and methanol over [Zn,Cr]/HZSM-5.

• Both Zn and Cr improved the formation of aromatics compared with HZSM-5. • Cr loading improved active centers number and tuned the acidity distribution. • Cr loading further enhanced n-hexane conversion, aromatics yield and stability. • Coaromatization of n-hexane and methanol over [Zn,Cr]/HZSM-5 was investigated. • Methanol addition enhanced the selectivity and yield of xylene due to methylation. The catalytic performance and properties of [Zn,Cr]/HZSM-5 were determined using XRD, py-FTIR, ICP, TG, and XPS and compared with those of Zn/HZSM-5 and HZSM-5 for the aromatization of n-hexane. A distinct role of Cr in enhancing n-hexane conversion, aromatic yield, and stability was observed. The catalytic performance of [Zn,Cr]/HZSM-5 and the effects of feed ratio, reaction temperature, and contact time on the coaromatization of n-hexane and methanol were investigated. Methanol addition increased the xylene yield due to methylation. Cofeeding provided high stability arising from the slow carbon deposition rate. At a feed ratio (n-hexane/methanol) of 3:7, reaction temperature 450 °C, and WHSV 2 h-1, the aromatic yield was 40.1%, with xylene selectivity of 40.4%. [ABSTRACT FROM AUTHOR]