Optimizing parameters affecting synthesis of a novel Co–Mo/GO catalyst in a Naphtha HDS reaction utilizing D-optimal experimental design method

Abstract

In this research effects of important synthesis parameters upon catalytic performance of a novel graphene based catalyst for an HDS reaction were investigated. The graphene oxide (GO) used as a support was initially prepared through chemical exfoliation of graphite via modified Hummers method. In this venue the impregnation method, promoter/main metallic spices ratio, total metal loading of the active phase and amount of chelating agent were systematically understudied. Thus, GO was impregnated with active metallic phases through the hydrothermal and modified incipient wetness impregnation techniques. In both procedures, 1:2, 1:3 and 1:4 weight ratios of Co/Mo with the percentages of the total metals amounting to 5, 10, and 15, respectively, were utilized. This was done together with the citric acid (CA) as a chelating agent with a CA/Mo molar ratio varying in the range of 1–5. The synthesized materials were characterized through the X-ray diffraction (XRD) technique as well as; the BET–BJH surface area measurements, Field Emission Scanning Electron Microscopy (FESEM), Inductively Coupled Plasma (ICP) and Temperature programmed desorption of ammonia (NH3-TPD) analyses. After a thorough characterization of this material, the catalyst was evaluated in an HDS reaction through a fixed-bed reactor under industrial conditions for a Naphtha feed. Obtained results revealed 95–100% conversions. This rendered the prepared material very promising for the purpose at hand. Then the D-optimal experimental design software was utilized to optimize the preparation of the GO based catalysts. In this venue, although the hydrothermally prepared material provided a more economical catalyst, the wetness impregnation method prevailed as the preferred one to synthesize an optimum catalyst with 0.3 wt% Co/Mo ratio, 10% total metal loadings and CA/Mo molar ratio of 2.