Hierarchical ZSM-5 Supported CoMn Catalyst for the Production of Middle Distillate from Syngas

Bifunctional catalysts using hierarchical ZSM-5 zeolite as a support have received more attention for their specific characteristic, which is in favor of producing middle distillate hydrocarbons in Fischer-Tropsch synthesis. The hierarchical structure together with the Bronsted acidity of ZSM-5 zeolites result in the secondary reaction for hydrocracking or isomerization of heavy hydrocarbons. Herein, hierarchical ZSM-5 zeolites with different acidities and mesopore volumes are synthesized by treating zeolites with TPAOH solution. The hierarchical zeolite supported CoMn catalysts are prepared by impregnation method, and all the catalysts are characterized by XRD, BET, XPS, CO/NH3-TPD, and Py-IR. The results show that the 0.5 M TPAOH solution treated ZSM-5 (Z5-0.5M) possesses the largest mesopore volume and a proper Bronsted acidity. In addition, the Z5-0.5M supported CoMn catalyst exhibits a selectivity of jet fuel range (C-8-C-16) as high as 50%, which is much higher than the maximum of 41% predicted by the Anderson-Schulz-Flory model. Moreover, the effect of cobalt loading indicates that the increased cobalt loading leads to the enhancement of CO conversion and the upshift to heavier hydrocarbons.