The Oxidative Desulfurization And Denitrogenation Of Liquid Fuel

The automobile exhaust pollution becomes more and more serious, most countries establish very stringent sulfur and nitrogen level for liquid oil to reduce the pollution emission, and the traditional HDS technology is facing a great challenge to produce ultra-low sulfur level fuel. So it is necessary to find an economical and efficient process to obtain low sulfur and nitrogen level fuel.The oxidative desulfurization technology is focused widely, because the advantages of mild reaction conditions, hydrogen free, simple operational conditions, and the sulfur compounds have the best reactivity in oxidative processes which are the most refractory in hydrodesulfurization. Our group had worked on oxidative desulfurization under Titanium silicalite/H2O2 system for some years, sulfur containing compounds can be removed successfully in our oxidative system, but the N-containing compounds co-exist with S-containing compounds in the liquid fuel, so we investigate the effect of N-containing compounds on oxidative desulfurization over Titanium silicalite catalysts. Considering the high cost of the Titanium silicalite catalysts and the loss caused by the use of solvent, the oxidative desulfurization or denitrogenation are investigated over MoO3/Y-Al2O3 catalyst under mild and solvent free conditions. The paper includes major three parts:1. The effect of N-containing compounds on oxidative desulfurization of model liquid fuelThe effect of N-containing compounds (pyridine, pyrrole, quinoline, indole and kabazole) on oxidative removal of organosulfur compouds (Thiophene/Th, Benzothiophene/BT and 4, 6-Dimethyl dibenzothiophene/4,6-DMDBT) in model fuel is studied over Titanium silicalite with hydrogen peroxide, and get the following results:1. In the TS-1/H2O2/H2O system, the effect of pyridine and pyrrole on oxidative removal of Th is due to the competitive adsorption between sulfides and nitrides on the active centers of TS-1, the effect from pyridine is worse than that of pyrrole; quinoline and indole have no influence on the final removal rate of Th.2. In the Ti-HMS/H2O2/methanol system, BT initial removal rate decreases by the introduction of quinoline, indole or carbazole, and their oxidized products, no effect on the final BT removal rate. The effect from carbazole with three rings is less than that of quinoline and indole.3. The competitive adsorption between S and N-containing compounds on the active centers result in the decrease of removal rate of 4,6-DMDBT, the effect from Quinoline is worse than that of indole. 2. Efficient oxidative desulfurization (ODS) of model fuel with H2O2 catalyzed by MoO3/γ-Al2O3 under mild and solvent free conditionsTh, BT, DBT (Dibenzothiophene) and 4,6-DMDBT is dissolved in n-octane separately as model fuel. The oxidative removal of S-containing compounds in model fuel is carried out with H2O2 over MoO3/γ-Al2O3 and solvent free conditions, the results are:1. The trend of oxidative reactivity of sulfur containing compounds is:4,6-DMDBT> DBT> BT> Th,4, 6-DMDBT can be oxidized in 5 min completely with initial sulfur concentration of 150μg/g, DBT and BT can be oxidized efficiently over MoO3/γ-Al2O3. The oxidized products of BT and DBTs are their corresponding sulfones under the conditions described above, and sulfoxides were not detected in the products, the product of Th is H2SO4.2. The employments of solvents (methanol and acetonitrile) have decreased the reaction rate of DBT, DBT removal rate is 91.5% after reaction 120 min when methanol was used as the solvent, and the efficient removal can be achieved under solvent free conditions, the technology is applied to process low sulfur fuel. The catalyst with 14.2 wt.% MoO3 loading shows the best activity on oxidative removal of DBT.3. The activity of spent catalyst is as well as the fresh one which is washed by methanol at 333 K and dried at 373 K in air over night, the regeneration processing have no influence on the activity of the catalyst.4. Pyridine and quinoline dreacrse the removal rate of Th under solvent free conditions.3. Oxidative denitrogenation with MoO3/y-Al2O3 and H2O2 under solvent free conditionsIn this part, the oxidation of N-containing compounds is studied with H2O2 over MoO3/γ-Al2O3 under solvent free conditions, there are several findings as results:1. The reactivity of the N-containing compounds trend as follow:pyrrole≈indole> pyridine≈quinoline, the neutral compounds can be oxidized easier than the basic ones.2. Removal rate of quinoline can be achieved at 74.9% over 0.1 g MoO3/γ-Al2O3 at 333 K with a molar ratio H2O2 to N is 4.3. The removal rate of quinoline increases over MoO3/γ-Al2O3 with keggin structure Mo precursor, which is due to the formation of well disperately Mo-O particles. The catalyst calcined at 873 K shows best oxidative denitrogenation activity.4. The oxidative denitrogenation of real gasoline and diesel with H2O2 over MoO3/γ-Al2O3 under solvent free conditions are investigated. The result of oxidative denitrogenation of diesel is better than that of gasoline, which removal rate is 87.5%, and that of gasoline is 37.8%. The neutral N-containing compounds ones can be oxidized completely in this oxidative processing, and the basic are the most refactory ones.