Cobalt Loading Effects on the Physico-Chemical Properties and Performance of Co Promoted Alkalized MoS۲/CNTs Catalysts for Higher Alcohols Synthesis

An extensive study of Higher Alcohol Synthesis (HAS) from synthesis gas using cobalt (Co) promoted alkalized MoS۲ catalysts supported on Carbon NanoTubes (CNTs) is reported. Up to  ۵wt.% of Co is added to the ۱۵wt.% Mo-wt.%K/ CNTs by incipient wetness impregnation method. Most of the metal particles were homogeneously distributed inside the tubes and the rest on the outer surface of the CNTs. The catalysts are extensively characterized by different methods and    the activity and selectivity of the catalysts were assessed in a fixed bed micro-reactor. Temperature Programmed Reduction (TPR) tests showed that addition of cobalt decreased the second TPR peak temperature from ۸۰۱ to ۶۶۰oC. The diffraction peaks that represent the characteristic K-Mo-O phase (i.e. K۲Mo۲O۷, K۲MoO۴, K۲Mo۷O۲۰, KMo۴O۶, and K۰.۳۳MoO۳; these species can enhances formation of higher alcohols) were observed in the X- Ray Diffraction (XRD) patterns of unpromoted Mo-K/CNTs and to a greater extent in the XRD patterns of Co-promoted Mo-K/CNTs catalysts.    Co addition to Mo-K/CNTs not only increased the number of surface sites, but also decreased      the average active metal particle sizes from ۷.۵۳ to ۵.۳۳ nm and increased the percentage dispersion from ۵۱.۱ to ۶۸.۲%. Among the catalysts with different Co loadings, catalyst with ۵ wt.% Co showed the highest %CO conversion of  ۳۸.۸%. The total alcohol selectivity reached a maximum of ۵۹.۷ wt.% on the catalyst promoted with ۳ wt.% cobalt. The catalyst with ۳ wt.% Co exhibited selectivity of ۴۱.۶۵ wt.% towards higher alcohols.

کلیدواژه ها:

Higher alcohols synthesis ، molybdenum ، Cobalt ، Carbon nanotubes ، physicochemical properties ، Activity ، Selectivity