Zhi-min Sun

Desulfurization of dibenzothiophene by chemical oxidation and solvent extraction with Me3NCH2C6H5Cl·2ZnCl2 ionic liquid

Desulfurization of dibenzothiophene (DBT) by a combination of both chemical oxidation and solvent extraction was investigated. Me3NCH2C6H5Cl·2ZnCl2 ionic liquid was prepared from cheap starting materials and used as extractant for oxidative desulfurization of DBT in n-octane. DBT in oil phase was extracted into ionic liquid phase and then oxidized to its corresponding sulfone by H2O2 and equal volume of acetic acid. The desulfurization yield of DBT in n-octane was 94% at 30 min under the conditions of H2O2/DBT molar ratio at 6 and V (ionic liquid) : V (n-octane) = 1 : 5, which was remarkably higher than that by mere extraction with ionic liquid (28.9%). The Me3NCH2C6H5Cl·2ZnCl2 ionic liquid could be recycled six times without a significant decrease in activity. Kinetics of oxidative desulfurization of DBT by H2O2 and acetic acid was first-order with an apparent rate constant of 0.0842 min−1 and half-time of 8.23 min.

Deep extractive and oxidative desulfurization of dibenzothiophene with C5H9NO·SnCl2 coordinated ionic liquid

A new C5H9NO·SnCl2 coordinated ionic liquid (IL) was prepared by reacting N-methyl-pyrrolidone with anhydrous SnCl2. Desulfurization of dibenzothiophene (DBT) via extraction and oxidation with C5H9NO·SnCl2 IL as extractant, H2O2 and equal mol of CH3COOH as oxidants was investigated. The Nernst partition coefficients k(N) of C5H9NO·SnCl2 IL for the DBT in n-octane was above 5.0, showing its excellent extraction ability. During the oxidative desulfurization process, the optimal molar ratio of H2O2/DBT was six. Sulfur removal of DBT in n-octane was 94.8% in 30 min at 30 °C under the conditions of H2O2/DBT molar ratio of six and V (IL):V (oil)=1:3. Moreover, the sulfur removal increased with increasing temperature because of the high reaction rate constant, low viscosity, and high solubility of dibenzothiophene-sulfone in the IL. The kinetics of oxidative desulfurization of DBT was also investigated, and the apparent activation energy was found to be 32.5 kJ/mol. The IL could be recycled six times without a significant decrease in activity.

Photocatalytic oxidative desulfurization of dibenzothiophene under simulated sunlight irradiation with mixed-phase Fe2O3 prepared by solution combustion

Mixed-phase Fe2O3 was prepared from Fe(NO3)3 and (C2H5)3NHCl via solution combustion. Photocatalytic oxidative desulfurization of dibenzothiophene (DBT) under simulated sunlight irradiation using mixed-phases of α- and β-Fe2O3 as catalysts was investigated. The DBT in the oil phase was extracted into water phase and then photooxidized to CO2 and SO42− by Fe2O3 and O2 dissolved in water. The Fe2O3 containing 36.6% β-Fe2O3 and 63.4% α-Fe2O3 exhibited the highest photocatalytic activity. Sulfur removal of DBT in n-octane was 92.3% for 90 min irradiation under the conditions of V(water) : V(n-octane) = 1 : 1, air flow rate at 150 mL min−1, and Fe2O3 addition at 0.05 g. The kinetics of photooxidative desulfurization of DBT was a pseudo-first-order with an apparent rate constant of 0.0287 min−1 and half-time of 24.15 min. The sulfur content of the actual diesel could be reduced from 478 μg mL−1 to 44.5 μg mL−1 after 90 min. The radical scavengers experiments and terephthalic acid fluorescence technique indicated that ˙OH and O2˙− were the main reactive species in the DBT photocatalytic degradation. A potential photocatalytic desulfurization mechanism using mixed-phase Fe2O3 was proposed.

Optimization of Oxidative Desulfurization of Dibenzothiophene Using a Coordinated Ionic Liquid as Catalytic Solvent

Abstract Oxidative desulfurization (ODS) of dibenzothiophene (DBT) in n-octane with hydrogen peroxide/acetic acid using a quaternary ammonium coordinated ionic liquid (IL) (C4H9)4NBr · 2C6H11NO as catalytic solvent has been studied. The ODS mechanism by coordinated ionic liquid [(C4H9)4NBr · 2C6H11NO] was also carried out. The sulfur-containing compounds in model oil were extracted into ionic liquid phase and oxidized to their corresponding sulfones by H2O2. The effect factors for desulfurization of model oil were investigated in detail by means of monofactorial and orthogonal experiments (L16(4)4). The results showed that the desulfurization efficiency of model oil could reach 98.6% under the optimal conditions of oxidation time, oxidation temperature, molar ratio of H2O2/sulfur (O/S), and volume ratio of model oil to coordinated ionic liquid were 30 min, 50°C, 16, and 1, respectively. The influences to the desulfurization efficiency of DBT decreased in the following order: volume ratio of model oil to coordinated ionic liquid (C4H9)4NBr · 2C6H11NO (Vmodel oil/VIL) > molar ratio of O/S > oxidation temperature > oxidation time, according to extreme analysis of the orthogonal test. The coordinated ionic liquid (C4H9)4NBr · 2C6H11NO can be recycled 5 times without a significant decrease in desulfurization.

One-Step Oxidative Desulfurization of Dibenzothiophene Using Cyclohexanone Peroxide in N-Alkyl-imidazolium–Based Ionic Liquid Extraction Systems

Abstract One-step oxidative desulfurization of dibenzothiophene (DBT) using cyclohexanone peroxide (CYHPO) was performed in the presence of N-alkyl-imidazolium-based ionic liquids (ILs). CYHPO is an oil-soluble oxidant and ILs are employed as extractants. The effect of the ILs, the molar ratio of CYHPO/S (O/S), volume ratio (VIL/Vmodel oil), reaction time (T), and reaction temperature (t) were investigated in detail. The results showed that the desulfurization ability of the ILs followed the order [OMim]BF4 > [HMim]BF4 > [BMim]BF4, reversing the length of the alkyl group to the imidazolium ring. When IL [OMim]BF4 was used, O/S was 2 and VIL/Vmodel oil was 1:1, and 93.5% of DBT in the model oil was removed at 40°C for 30 min. The desulfurization rate of gasoline was 70.8% under optimal conditions. IL ([OMim]BF4) could be recycled for five times without a significant decrease in activity.

The Photooxidative Desulfurization of Thiophene with Tetrabutylammonium Bromide as a Phase Transfer Catalyst

Abstract Photochemical oxidative desulfurization of thiophene with tetrabutylammonium bromide (TBAB) as phase transfer catalyst was studied. The effects of the TBAB addition and pH on the desulfurization yield of thiophene were investigated. The cycle model of desulfurization of thiophene with TBAB was proposed. The results show that the desulfurization yield of thiophene in n-octane is 80.6% for a 2-hr photoirradiation under the conditions of air flow at 150 mL/min, V (n-octane):V (water) = 1:1, pH = 12, and 0.1 g of TBAB as catalyst. The photooxidation kinetics of thiophene is first-order with rate constant of 0.5702 hr−1 and half-life of 1.22 hr.

Photocatalytic Oxidation Kinetics of Thiophene with Nano-TiO2 as Photocatalyst

Photocatalytic oxidative kinetics of thiophene in n-octane/water extraction system was studied with nano-TiO₂ powders as photocatalyst and O₂ in air as oxidant. Influence of initial concentration of thiophene and addition of TiO₂ on reaction rate constant and half time were investigated. Kinetics equation was founded. The results showed that the approviate addition of TiO₂ was 0.1 g in 100 mL reaction system and the photooxidation kinetics of thiophene with TiO₂ was first-order with rate constant of 0.6405 h^-1 and half-time of 1.0822 h under the conditions with initial concentration of thiophene at 800 muLldrL^-1 and addition of TiO₂ at 0.1 g. The reaction rate constant increased with the decrease of initial concentration of thiophene.

Photochemical Oxidation of Thiophene Adsorbed on Na-ZSM-5 Zeolite by O2 in Oil/Acetonitrile Two-Phase Extraction System

Photochemical oxidation of thiophene in n-octane/acetonitrile extraction system using O2 as oxidant was studied. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. A 500 w high-pressure mercury lamp was used as light source for irradiation and air was introduced by a gas pump to supply O2. Thiophene dissolved in nopolar n-octane solvent was photodecomposed and removed into the polar acetonitrile phase. The desulfurization rate of thiophene in n-octane is 65.2% under photo-irradiation for 5 h. It can be improved to 96.8% by adding 0.15 g Na-ZSM-5 zeolite into 100 mL reaction system, which is the absorbent for O2 and thiophene. And the photooxidation kinetics of thiophene with O2 and Na-ZSM-5 zeolite is first-order with an apparent rate constant of 0.6305 h-1 and half-time of 1.10 h under the conditions of air flow at 150 mL-min-1 and V(n-octane): V(water)=1:1. The sulfur content can be depressed from 800 muL-L-1 to less than 26 muL-L-1.