Synthesis and characterization of supported mixed oxides of Mo, Ni nanostructures on γ- Alumina as catalyst for oil residue hydrodesulphurization

Introduction: Oil residue is one of the cuts of oil refinery process, which has been consisted more than 4% sulfur. Sulfur in oil residue is a poison for catalysts of other process in a refinery. So we need to desulphurization. In this work, for improving of activity of desulphurization catalyst, MoO3 and NiO nanostructure on γ-Alumina as support has synthesized and effects of impregnation conditions such as media PH, organic additives on particles morphology, size and amount of active metals on support have precisely investigated. Material and method: At first, the supports of catalyst were prepared utilizing the Azarshahr Boehmite, Peptizing by nitric acid and using of SB1(Sudu Bohmite) and HPMC (Hydroxy Propyl Methyl Cellulose) as binder and rheology agents respectively. Prepared magma were then shaped and dried and the dried sample (support) were calcined and characterized by BET surface area and porosimetry. Impregnation and preparation of catalyst for hydrodesulphurization of oil residue were carried out with this support and nanostructure Ni-Mo simultaneously. So, molybdenum oxide and nickel oxide nanostructures were synthesized utilizing the solution combustion method in which the ammonium heptamolybdate powder, nickel nitrate.6H2O powder and urea were used as precursors. After preparation of impregnation solution and surfactant solution, both were poured on the support. Conditions of reaction are listed as follows: The molar ratio of surfactant/Mo was 1:1, pH of reaction media was adjusted on 3.5 – 5 by Sitric acid and the support was exposed to impregnation solution in room temperature and was heated to 60 °C to evaporate solution completely, after precipitation of Mo, Ni on the support, catalysts were dried in 120 °C , calcinated in 35 °C to 520 °C and characterized by BET( surface area), pore volume (P.V), pore diameter(P.D.), SEM, XRD, AAS.Results and conclusion: In this research, effects of two organic additives, EDTA and urea, on MoO3 and NiO nanoparticle growth, morphology and particle size of product and amount of active metal that was impregnated on support from impregnation solution were investigated. Also, in this research, the effect of reaction media PH on size and structure of MoO3 and NiO nanoparticles on support was studied. According to previous researches, the best reaction media pH to form spherical nanoparticle with great homogeneity from MoO3 is in an acidic solution (pH=3.5) when urea is used as additive but according to isoelectric point γ-Alumina and MoO3 , NiO and appropriate pH for best bonding of nanoparticle and support, optimization of pH is necessary. Outcomes were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction, surface area (BET), atomic absorption spectroscopy (AAS), performance test.

Keywords:

Molybdenum oxide , Nanostructures , Hydrodesulphurization , Scanning Electron microscopy , surface area