Oxidative Removal Of Dibenzothiophene Research Articles

Oxidative removal of dibenzothiophene and related sulfur compounds from fuel oils under pressurized oxygen at room temperature with hydrogen peroxide and a phosphorus-free catalyst: sodium decatungstate

We investigated the removal of dibenzothiophene (DBT) and related compounds, 4-methyldibenzothiophene (4-MeDBT), 4,6-dimethyldibenzothiophene (4,6-DMeDBT), 2,8-dimethyldibenzothiophene (2,8-DMeDBT), and 1-benzothiophene (1-BT) from several oil media at room temperature under pressurized O2 (0.6 MPa) by means of a three-phase reaction system consisting of the oil phase, an aqueous phase containing the phosphorus-free polyoxotungstate catalyst Na4W10O32·8H2O, H2O2, and tetraoctylammonium bromide, and the gas phase. Under conditions in which the initial DBT concentration in octane was 10.1 mM, the desulfurization ratio reached 87% after reaction for 6.5 h. The sulfur atoms in the initial DBT were well accounted for by the sulfur atoms in the residual DBT, the dibenzothiophene sulfone and dibenzothiophene 5-oxide in the octane phase, and the dibenzothiophene sulfone that precipitated. Prolonged reaction time to 18 h resulted in 92% desulfurization. The desulfurization of octane decreased in the order 2,8-DMeDBT ~ DBT > 4-MeDBT >1-BT ~ 4,6-DMeDBT. Light oil and kerosene could also be desulfurized efficiently: after reaction for 6.5 h, the desulfurization ratios reached 77 and 78% for light oil and kerosene, respectively.

Extractive oxidative desulfurization of model oil/crude oil using KSF montmorillonite-supported 12-tungstophosphoric acid

12-Tungstophosphoric acid (PW) supported on KSF montmorillonite, PW/KSF, was used as catalyst for deep oxidative desulfurization (ODS) of mixed thiophenic compounds in model oil and crude oil under mild conditions using hydrogen peroxide (H2O2) as an oxidizing agent. A one-factor-at-a-time method was applied for optimizing the parameters such as temperature, reaction time, amount of catalyst, type of extractant and oxidant-to-sulfur compounds (S-compounds) molar ratio. The corresponding products can be easily removed from the model oil by using ethanol as the best extractant. The results showed high catalytic activity of PW/KSF in the oxidative removal of dibenzothiophene (DBT) and mixed thiophenic model oil under atmospheric pressure at 75 °C in a biphasic system. To investigate the oxidation and adsorption effects of crude oil composition on ODS, the effects of cyclohexene, 1,7-octadiene and o-xylene with different concentrations were studied.

Oxidative removal of dibenzothiophene from a model fuel using nanocrystalline Ti-beta catalyst

Dibenzothiophene (DBT) was oxidised by hydrogen peroxide in a batch operation using nano-crystalline Ti-beta catalyst. The catalyst was prepared and characterized by XRD, SEM, TEM and BET surface area analysis. The parametric studies of the reaction, effects of stirrer speed, catalyst concentration, initial DBT concentration, oxidant to substrate mole ratio and temperature were investigated. The kinetic study emphasised on the analysis of Langmuir Hinshelwood type rate model in the present work. Three rate models based on adsorption, dual site surface reaction and single site Eley-Riedel mechanism were compared by fitting with the experimental data and the surface reaction controlled rate model was found to be the appropriate one. The activation energy of reaction was obtained as 46.03 kJ/mol.

Heteropolyanion Substituted Layered Double Hydroxide as Recoverable Catalyst for the Oxidative Desulfurization of Simulated Fuel Oil and Diesel

Heteropolyanion substituted layered double hydroxide were synthesized and used as catalysts for oxidative desulfurization in simulated fuel oil (dibenzothiophene (DBT) inn-octane) or diesel. The catalysts are recoverable and operate with high conversion efficiency under mild conditions of atmospheric pressure and 60 °C in a biphasic system using peroxide hydrogen as oxidant and acetonitrile as extractant. Zn9Al3(OH)24PW12O40(ZnAlPW), Zn9Al3(OH)24PMo12O40(ZnAlPMo) and Zn12Al4(OH)32SiW12O40(ZnAlSiW) were identified as effective catalysts for the oxidative removal of DBT from simulated fuel oil. The order of decreasing catalytic activity is ZnAlPMo > ZnAlPW > ZnAlSiW. The results show that the best catalysts, ZnAlPMo, attained to a DBT conversion of nearly 100%. All the catalysts can be readily recycled by filtration after use. The recoverable ZnAlPMo retains nearly the same catalytic activity as the fresh. ZnAlPMo was found to exhibit an ideal catalytic activity in oxidative desulfurization of diesel with a total sulfur removal rate of 91.8%.

Oxidative removal of dibenzothiophene in a biphasic system using sol–gel Fe[sbnd]TiO2 catalysts and H2O2 promoted with acetic acid

FeTiO2 catalysts were synthesized with the sol–gel method and were characterized by X-ray diffraction, N2 adsorption measurement, Mössbauer spectroscopy, UV–vis spectroscopy, Raman spectroscopy, temperature programmed reduction, and temperature programmed desorption of NH3. The FeTiO2 catalysts chiefly consist of crystalline anatase. Fe3+ ions are highly dispersed on the surface and distributed in octahedral-coordinate sites within different environments in TiO2. The FeTiO2 catalysts were then evaluated for oxidation desulfurization of dibenzothiophene in a biphasic reaction mixture consisting of an acidified polar phase and a hexadecane model fuel phase. Compared to control tests, the catalytic activity for dibenzothiophene (DBT) oxidation is markedly improved by addition of acetic acid, typically at least doubling DBT conversion compared to that observed under control conditions. Under optimal conditions (10wt% Fe in the FeTiO2 catalyst and a pH adjusted to 0), 100% of the 300ppm DBT initially present in the reaction mixture could be completely oxidized within 5min. Oxidation of DBT formed sulfoxide/sulfones which were found to be enriched in the polar phase. The sol–gel FeTiO2 catalysts possess several attributes which may contribute to their activity for DBT oxidation: (1) their hydrophilic–hydrophobic character that facilitates DBT oxidation as a phase transfer catalyst; (2) coordination and activation of acetic acid and peroxyacetic acid with Fe3+ and Ti4+ present at the FeTiO2 surface, and (3) formation of superoxides at the FeTiO2 surface.

Efficient oxidative desulfurization (ODS) of model fuel with H 2O 2 catalyzed by MoO 3/γ-Al 2O 3 under mild and solvent free conditions

An efficient process to remove organic sulfur compounds from model fuel has been explored. Dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) can be completely oxidized into their corresponding sulfones by H 2O 2 over 14 wt.% MoO 3/γ-Al 2O 3 catalyst under mild conditions in 15 min. The effects of solvent, initial sulfide concentration, loading of MoO 3 and amount of catalyst on oxidative removal of DBT were studied. The employments of solvents have decreased the reaction rate of DBT, which can be attributed to the competitive adsorption between the sulfide and solvent. The oxidative reactivity increases in the order of thiophene (Th) < benzothiophene (BT) < DBT < 4, 6-DMDBT. The catalyst can be regenerated by methanol washing at 333 K.

Oxidative Removal of Dibenzothiophene by H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; over Activated Carbon-Supported Phosphotungstic Acid Catalysts

Phosphotungstic acid (HPW) supported on activated carbon (AC) combined with hydrogen peroxide formed an oxidative desulfurizaiton (ODS) system to oxidize sulfur-containing compounds in diesel fuel. Dibenzothiophene (DBT) dissolved in n-octane was selected as a model feedstock for studying this new ODS system. The HPW/AC catalysts were characterized with XRD, FTIR and N2 adsorption-desorption measurements. HPW was highly dispersed on the surface of carbon support. It was found that the DBT adsorption capacity decreased from 42 mg S/g to 33.13 mg S/g as HPW loading amount increased from 0 to 15 wt.%. Oxidative removal of DBT in the model oil significantly increased with increasing HPW loadings on the support from 0 to 10 wt.%. 100 % DBT was removed by using the catalysts with HPW content higher than 10 wt. %. At 80 °C, oxidative removal of DBT reached 100 % after 40 min of reaction when O/S molar ratio ranged from 4 to 10.

Removal of dibenzothiophene in diesel oil by oxidation over a promoted activated carbon catalyst

Oxidative removal of dibenzothiophene (DBT) in n-octane solution by H2O2 on a promoted activated carbon (AC) catalyst was studied. DBT adsorption and catalytic behaviors on AC were examined. Effects of pH in aqueous phase, amounts of AC and formic acid (HCOOH) for promotion as well as initial molar H2O2/S ratio were investigated. Experimental results led to conclusion that DBT was readily oxidized by H2O2 over an AC catalyst promoted by HCOOH. Suitable amount of AC can improve the activity of H2O2 resulting in a deeper extent of sulfur removal. A 100% conversion of DBT in an octane solution by H2O2 oxidation was attained on the HCOOH-H2O2/AC catalyst at 80°C for a reaction time of 30 min.