Wenshuai Zhu

Commercially available molybdic compound-catalyzed ultra-deep desulfurization of fuels in ionic liquids

A simple liquid–liquid extraction and catalytic oxidative desulfurization (ECODS) system composed of molybdic compound, 30% H2O2 and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) has been found suitable for the ultra-deep removal of dibenzothiophene (DBT) in model oil. The precatalyst of molybdic compound was oxidized with H2O2 to form peroxomolybdic compound, which was soluble in ionic liquid and dissolved in oil. The sulfur-containing compounds, such as benzothiophene (BT), DBT and 4,6-dimethyldibenzothiophene (4,6-DMDBT), in model oil were extracted into ionic liquid phase and oxidized to their corresponding sulfones by peroxomolybdic compound. In the case of the system containing model oil (DBT), H2O2, Na2MoO4·2H2O and [bmim]BF4, extraction and catalytic oxidation increased the sulfur removal to 99.0%, which was remarkably superior to mere solvent extraction with IL (13.6%) or catalytic oxidation without IL (4.1%). The desulfurization system could be recycled five times with very little decrease in activity.

Deep oxidative desulfurization of fuels in redox ionic liquids based on iron chloride

Three redox ionic liquids based on iron chloride were synthesized and employed in extraction and catalytic oxidation desulfurization systems for removal of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in model oil. Sulfur removal selectivity for S-compounds followed the order of DBT > 4,6-DMDBT > BT. Due to the redox properties of 1-butyl-3-methylimidazolium chloride iron chloride ([bmim]Cl/FeCl3) with addition of hydrogen peroxide, DBT removal can reach 99.2% under mild reaction conditions, which is not only higher than mere extraction with ionic liquid (IL), but also superior to two other ILs based on iron chloride under the same reaction conditions. Herein, [bmim]Cl/FeCl3 played a dual role in the process of desulfurization, not only acting as catalyst but also acting as an extractant. [bmim]Cl/FeCl3 is insoluble in n-octane, and the solubility in the model oil is also negligible. The used ionic liquid could be recycled for six times with a slight decrease in activity.

One-pot extraction combined with metal-free photochemical aerobic oxidative desulfurization in deep eutectic solvent

Five low-cost deep eutectic solvents (DESs) were synthesized based on choline chloride (ChCl) and a series of straight-chain monobasic acids. Under UV light irradiation, one-pot extraction combined with the metal-free photochemical aerobic oxidative deep desulfurization of fuels in deep eutectic solvents was successfully achieved. This liquid-liquid extraction and photochemical oxidative desulfurization system (EPODS) comprised of air, isobutylaldehyde (IBA), DESs and model oil. The factors influencing sulfur removal were systematically investigated, including the amount of DES, volume ratio of model oil and IBA, different sulfur concentrations, different substrates and fuel composition. The sulfur removal of dibenzothiphene (DBT) could reach 98.6% with air as oxidizing agent under UV light irradiation. Sulfur removal by different sulfur compounds decreased as BT > DBT > 4,6-DMDBT. The possible photochemical oxidative desulfurization mechanism was researched by gas chromatograph-mass spectrometer (GC-MS), electron spin-resonance (ESR) spectroscopy and density functional theory (DFT).

Deep oxidative desulfurization of fuels by Fenton-like reagent in ionic liquids

The oxidation of dibenzothiophene (DBT), benzothiophene (BT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in model oil was studied in the extraction and catalytic oxidative desulfurization (ECODS) system at room temperature (30 °C). Various Fenton-like reagents, such as Co2+, Cu2+, Ni2+, Mn2+, Cr3+, Fe3+ and H2O2, were screened for desulfurization in ionic liquids. The experimental results demonstrated that the desulfurization system containing anhydrous FeCl3, H2O2, and [bmim]BF4 exhibited high catalytic activity. The sulfur removal of DBT-containing model oil could reach 96.1%, which was obviously superior to mere solvent extraction with [bmim]BF4 (28.5%) or catalytic oxidation without [bmim]BF4 (7.3%). In a combination of extraction and oxidation, the sulfur content decreased from 500 ppm to 5 ppm, when the hydrogen peroxide was added into the desulfurization system in four batches. The catalytic oxidation reactivity of the sulfur-containing compounds was found to be in the following order: DBT > BT > 4,6-DMDBT. Moreover, the desulfurization system could be recycled five times without a significant decrease in activity.

Catalytic oxidative desulfurization with a hexatungstate/aqueous H2O2/ionic liquid emulsion system

Three hexatungstates ([(C4H9)3NCH3]2W6O19, [(C8H17)3NCH3]2W6O19, [(C12H25)3NCH3]2W6O19) have been synthesized and characterized. The hexatungstates were dissolved in the hydrophobic 1-octyl-3-methylimidazolium hexafluorophosphoric ([Omim]PF6) ionic liquid (IL) forming a water-in-IL emulsion system with aqueous hydrogen peroxide. Catalytic oxidation of sulfur-containing model oil and real gasoline was studied under different conditions with this system. The multiphase reaction of the new IL emulsion system made for easy separation and exhibited good recycleability. As a stable macrocosm, the separated catalytic system could be directly added to fresh oil and H2O2 for the next run without any treatment and after recycling 15 times, the sulfur removal could still reach a high level without any decrease. The supposed mechanism is given to show the superiority of the new emulsion catalytic system.

Few-layered graphene-like boron nitride induced a remarkable adsorption capacity for dibenzothiophene in fuels

Metal-free graphene-like boron nitride (BN) samples were prepared and applied as adsorbents for removing dibenzothiophene (DBT) in model oil. The results showed that the graphene-like BN exhibited a remarkable adsorption performance. The adsorption capacity could reach 28.17 mg S g−1 adsorbent. Experiments have been carried out to investigate the effects of the number of BN layers, DBT initial concentration, and temperature on DBT adsorption. Langmuir and Freundlich isotherm models were used to study the adsorption of DBT on BN. The kinetic results showed that the adsorption process was best described by the pseudo-second-order kinetic model. Density functional theory (DFT) was employed to prove that the Lewis acid–base interaction plays an important role in removing DBT over graphene-like BN.

The dehydration of fructose to 5-hydroxymethylfurfural efficiently catalyzed by acidic ion-exchange resin in ionic liquid

The efficient dehydration of fructose to 5-hydroxymethylfurfural (HMF) was developed in ionic liquids (ILs) with acidic ion-exchange resins as catalyst. By screening different resins and ILs respectively, it was found that the structure of resins and ILs had a prominent effect on the dehydration of fructose. In 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), D001-cc resin showed a high activity. And then the effects of reaction temperatures, dosages of D001-cc, and different initial fructose loadings on the dehydration of fructose were studied in detail. The system of D001-cc resin and [Bmim]Cl exhibited a constant activity at 75°C for 20 min and a 86.2% yield of HMF was obtained after seven recycles. At 75°C for 20 min, a 93.0% yield of HMF from the dehydration of fructose was obtained.

Oxidative Desulfurization of Fuels Catalyzed by Fenton‐Like Ionic Liquids at Room Temperature

Oxidation of the sulfur-containing compounds benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) has been studied in a desulfurization system composed of model oil, hydrogen peroxide, and different types of ionic liquids [(C(8)H(17))(3)CH(3)N]Cl/FeCl(3), [(C(8)H(17))(3)CH(3)N]Cl/CuCl(2), [(C(8)H(17))(3)CH(3)N]Cl/ZnCl(2), [(C(8)H(17))(3)CH(3)N]Cl/SnCl(2), [(C(4)H(9))(3)CH(3)N]Cl/FeCl(3), [C(10)H(21)(CH(3))(3)N]Cl/FeCl(3), [(C(10)H(21))(2)(CH(3))(2)N]Cl/FeCl(3). Deep desulfurization is achieved in the Fenton-like ionic liquid [(C(8)H(17))(3)CH(3)N]Cl/FeCl(3) at 25 °C for 1 h. The desulfurization of DBT reaches 97.9%, in consuming very low amount of [(C(8)H(17))(3)CH(3)N]Cl/FeCl(3) (only 0.702 mmol). The reaction conditions, for example, the amount of [(C(8)H(17))(3)CH(3)N]Cl/FeCl(3) or H(2)O(2), the temperature, and the molar ratio of FeCl(3) to [(C(8)H(17))(3)CH(3)N]Cl, are investigated for this system. The oxidation reactivity of the different sulfur-containing compounds is found to decrease in the order of DBT>BT>4,6-DMDBT. The desulfurization system can be recycled six times without significant decrease in activity. The sulfur level of FCC gasoline could be reduced from 360 ppm to 110 ppm.

Fenton-like ionic liquids/H2O2 system: one-pot extraction combined with oxidation desulfurization of fuel

The extraction desulfurization (EDS) and extraction combined with oxidation desulfurization (EODS) for the removal of dibenzothiophene (DBT), benzothiophene (BT), and 4,6-dimethyldibenzothiphene (4,6-DMDBT) in a model oil were carried out in Fenton-like ionic liquids, such as [Et3NHCl]FeCl3, [Et3NHCl]CuCl2, [Et3NHCl]ZnCl2, [Et3NHCl]CoCl2, [Et3NHCl]SnCl2 and [Et3NHCl]CrCl3. The deep desulfurization could be achieved in [Et3NHCl]FeCl3 for only 5 min at room temperature. The reaction conditions such as temperature, the molar ratio of H2O2 and DBT and the amount of ionic liquid (IL) were investigated in the EODS system. By controlling the way of adding H2O2 into the desulfurization system, the sulfur content in the model oil could decrease from 500 mg L−1 to less than 10 mg L−1 at the IL/oil volume of 1 : 5. The oxidation reactivity of the different sulfur-containing compounds was found to be in the order of DBT > BT > 4,6-DMDBT. Moreover, the EODS system could be recycled ten times with a slight decrease in activity to model oil. EODS process was applied to prehydrotreated gasoline and the sulfur content could decrease from 150 to 15 mg L−1 after two rounds of reaction.

A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization

Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance.