A facile and efficient method is adopted to intercalate promoter and few-layered MoS2 in Ti3C2Tx MXene for high hydrodesulfurization activity via an in situ thermal conversion process.
Sulfur removal is the most challenging task in petroleum refineries for upgrading clean fuel from crude oil. In this regard, an efficient Ni-MoS 2 catalyst was prepared using ammonium tetrathiomolybdate (ATM), (NH 4) 2 MoS 4 as a precursor for hydrodesulfurization (HDS) reaction. ATM was derived by sulfiding an aqueous ammoniacal ammonium heptamolybdate and impregnated on alumina support with and without nickel promoter to form a series of MoS 2 /Al 2 O 3 , and Ni-MoS 2 / Al 2 O 3 catalysts with controlled calcination temperature. The prepared ATM and catalysts were characterized by X-ray diffraction (XRD), Infrared spectroscopy and nitrogen adsorption-desorption. The phase transformation of ATM to MoS 2 was observed by TGA, and number of MoS 2 layer formation was calculated from the frequency difference between the redshift and blueshift by Raman spectrum. The catalytic properties of MoS 2 /Al 2 O 3 , and Ni-MoS 2 /Al 2 O 3 were investigated using thiophene as the model compound for HDS reaction. The HDS rate, C 4 hydrocarbon product distribution and selectivity were quantified by microreactor with refinery gas analyzer system. The prepared MoS 2 catalysts (MoS and NiMoS) at 350 °C showed a better conversion rate than another catalyst due to the synergy between the promoter and few-layered MoS 2 on support. Thus, ATM is a suitable candidate for the formulation of Ni-MoS 2 catalyst at 350 °C for improving thiophene HDS activity.
An emphasis has been placed on investigation spent hydroprocessing catalyst recovery due to environmental regulations which register spent catalysts as hazardous waste materials. Kuwait refinery produces ca. 6000 ton/year spent catalysts from the bottom of the barrel (ARDS) processes, which contain valuable metals such as molybdenum, vanadium, nickel or cobalt etc. These catalysts are not viable to regenerate mainly due to the metal deposition. The present study is carried out on industrial spent residue hydroprocessing (ARDS) catalysts that contain high levels of metals. The possibility of recycling total spent catalysts (TSC) was studied by using various steps such as deoiling, drying, grinding, sieving and decoking. In the subsequent steps, the digested spent catalysts were treated with acid-base reactions in order to separate the various components of the spent catalyst. Using various leaching reaction conditions such as acid-base concentration, reaction pH in aqueous as well as organic mediums were studied. The metals were leached out in the solution while alumina support was recovered as bulk solid in the form of boehmite. The recovered alumina is further treated hydrothermally and recovered as boehmite, samples were characterized by surface area, pore volume, and pore size distribution measurements. Hence, recovery of valuable metals from the spent catalysts is an attractive option for their recycling and utilization. Therefore, TSC recovery is not only important from an environmental point of view but also very vital from an economic viewpoint.
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