Study On Oxidative Desulurization Of Diesel Oil By MoO₃/mesoporous Al₂O₃Modified By K

With the increasingly stringent environmental regulations around the world, thedeep desulfurization of fuel oil has become a worldwide issue. Nowadays, thedesulfurization technologies for fuel oil are mainly classified into two kinds:Hydrodesulfurization and Nonhydrodesulfurization. Although hydrodesulfurizationtechnology could reduce the sulfur to a low content, under current conditions somedrawbacks are still inevitable which includes a demanding processing conditions, highoperating costs and great difficulty in removing the large steric sulfides. Therefore,some researchers committe to the reearch of Non-hydrodesulfurization technology.Because of its low investment, mild reaction conditions, and high efficiencies on theremoval of DBT sulfides. As an excellent supplementary method to thehydrodesulfurization technology, nonhydrodesulfurization is attracting moreconcerning among the researchers.At present, the oxidative desulfurization catalyst mainly includes homogeneouscatalysts and heterogeneous catalysts. The mesoporous alumina is widely used inoxidative desulfurization process due to its narrow pore size distribution and largersurface area..In this paper sol-gel method was employed in the preparation of the mesoporousAl₂O₃support and incipient wetness impregnation was applied in preparing theMoO₃/mesoporous Al₂O₃catalyst modified by K.The characterization results of XRD,TPD, XPS,showed that the addition of potassium in catalysts could help reducing theacidity of the carrier’s surface and promoting the even dispersion of acidicmolybdenum oxide in the M-Al₂O₃carrier’s surface. A small amount of potassiumcan promote the formation of multi-aggregation of octahedral molybdate, with theproportion of K to Mo is0.5, the number of octahedral molybdate reach the maximumpoint. However, excess potassium would lead to falling of polymerization in thepotassium molybdenum compounds while the number of octahedral molybdate wouldreduce correspondingly. The catalysts are used in the oxidative desulfurization ofdiesel oil and model oil. In the experiments, the influence of K precursors,impregnation sequences, oxidation temperature and time were investigated.From the experiment of Oxidative desulfurization of model oil and diesel we cansee the factors such as K precursor, proportion of potassium to molybdenum,oxidation temperature and time, the amount of catalyst have quite different effects onthe oxidative desulfurization rate.The optimum conditions are that K₂CO₃is theprecursor of K, the content of K and Mo is same, the impregnation method ispotassium molybdenum after impregnation method, the oxidation temperature is60℃,oxidation time is60min, the amount of catalyst is0.5%,[H₂O₂]/[S]=8, and extractantand diesel have a volume ratio of1to1. Sulfide reaction active sequence is DBT,4,6-DMDBT, BT.The results of the diesel oxidation-adsorption showed that the particle size ofsilica gel, adsorption temperature, and proportion of oil and solvent play a unnecessary role in desulfurization efficiency and the rate of recovery. The relativelysuitable experimental conditions are that Silica gel particle size is20-40mesh, theproportion of oil and solvent is5, the adsorption temperature is40℃, adsorptiontime is30min. Under these conditions, the removal efficiency could reach61.21%.