Oxidative Desulfurization Performance Research Articles

In situ structural reconstruction triggers the hydrothermal synthesis of hierarchical Ti-Beta zeolites for oxidative desulfurization

Hierarchical Ti-Beta zeolite was hydrothermally synthesized via in situ structural reconstruction strategy, triggering unique catalytic performance in oxidative desulfurization.

Solvent-Free Synthesis of Mesoporous Zirconia-Supported Tungsten Oxide Composite and its Superior Oxidative Desulfurization Performance

Solvent-Free Synthesis of Mesoporous Zirconia-Supported Tungsten Oxide Composite and its Superior Oxidative Desulfurization Performance

Synthesis of amorphous mesoporous TiO2-SiO2 and its excellent catalytic performance in oxidative desulfurization

Amorphous mesoporous TiO2-SiO2 composites have been prepared by introducing n-propyltriethoxysilane (PTES) into the synthesis system of titanium silicalite-1 (TS-1). The hydrolysate of PTES can participate in the condensation between ‘Si(OH)4’ and ‘Ti(OH)4’, and generate the isolated ‘alkyl-rich regions’ and ‘inorganic TiO2-SiO2 regions’. Proper amount of ‘alkyl rich regions’ can highly separate titania–silica species and seriously retard the crystal growth, thereby producing the amorphous mesoporous structure. As the PTES/Si molar ratio is between 0.1 and 0.2, the resulting samples have plenty of three-dimensional connected mesopores, and they display outstanding catalytic performance in the oxidative desulfurization of bulky sulfur compounds.

Phosphomolybdic acid niched in the metal-organic framework UiO-66 with defects: An efficient and stable catalyst for oxidative desulfurization

The synthesis of highly efficient and stable catalysts for oxidative desulfurization is still a challenging task. Herein, a composite material (HPMo@UiO-66) of phosphomolybdic acid (HPMo) encapsulated in the metal-organic framework UiO-66 with missing-linker defects was prepared via a one-pot hydrothermal method. A series of as-synthesized catalysts were systematically characterized by XRD, FT-IR, SEM, BET, TGA, XPS, UV–vis and PL. Through oxidative desulfurization experimental evaluations, the catalyst 0.5-HPMo@UiO-66-D with defects shows the superior catalytic oxidative desulfurization performance and high reusability. 0.5-HPMo@UiO-66-D is able to completely remove DBT in the model fuel in 60 min, and the reaction system can be recycled 10 times with a high activity. In addition, the kinetics and the activation energy of the oxidative desulfurization were studied.

Synergistic Effect between Zr-MOF and Phosphomolybdic Acid with the Promotion of TiF4 Template.

Metal-Organic Framework (MOF) materials are often modified or functionalized, and then the crystal size and morphology of MOF materials are changed. In the process of preparing UiO-66 confined phosphomolybdic acid (PMA) composites (PU), the TiF4-modified PU (PMA + UiO-66) composite catalyst (TiF4-PU) was successfully synthesized by adding titanium tetrafluoride, and the catalytic desulfurization activity was excellent. Similarly, the reaction mechanism was investigated by means of infrared spectroscopy, Raman spectroscopy, XPS, and UV/Vis spectroscopy. The results show that the addition of TiF4 not only changes the appearance and color of the catalyst, but also changes the valence distribution of the elements in the catalyst. The number of oxygen vacancies in the MOF increases due to the addition of TiF4, and more electrons are transferred from the Zr-MOF to PMA to form more Mo5+, which improved the performance of oxidative desulfurization in comparison. Thus, a stronger strong metal-support interaction (SMSI) effect is observed for TiF4-modified PU catalysts. In addition, the quenching experiment of free radicals shows that ·OH radical is the main active substance in the oxidative desulfurization reaction over TiF4-PU catalyst.

Pt nanoparticles encapsulated on V2O5 nanosheets carriers as efficient catalysts for promoted aerobic oxidative desulfurization performance

Platinum group metals (PGMs) usually exhibit promising aerobic catalytic abilities, providing a green and feasible oxidative desulfurization method. However, often, the PGM nanoparticles (NPs) get leached, and the catalysts are deactivated. In this work, Pt NPs with particle sizes of approximately 4–5 nm were encapsulated effectively and uniformly on the surface of vanadium pentoxide (V2O5) nanosheets (with thicknesses of approximately six atomic layers) through strong metal-support interactions. The synthesized catalysts promote catalytic aerobic oxidation reactions, realizing deep desulfurization (99.1%, < 5 μg g−1) under atmospheric pressure and 110 °C reaction temperature. Remarkable degrees of sulfur removal could be achieved for oils with different initial S-concentrations and substrates. Additionally, the as-prepared catalysts could be recycled for reuse at least seven times.

Preparation, Characterization, and Kinetics Model of MoCo/γ-Al2O3 Catalysts for Oxidative Desulfurization of Light Naphtha

The subject of this work is to study the effect of pH, molybdenum content and some of the transition metals (such as Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel) on the catalyst properties and performance of oxidative desulfurization (ODS). To achieve this aim, the mesoporous 5%Co10%Mo/γ-Al2O3 catalyst was prepared by incipient wetness impregnation method. Then, the as-synthesized catalysts were characterized by X-Ray Diffraction (XRD), N2-adsorption/desorption, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Scanning Electron Microscopy (SEM) and NH3-Temperature Programmed Desorption (NH3-TPD). The catalytic activity was measured with catalytic ODS setup. The catalyst with 10wt%Mo (as an active metal) and 5wt%Co content (as a promoter) at pH=4 represented the optimum performance for oxidative desulfurization. The 5%Co10%Mo/γ-Al2O3 has the Surface Area =170.61 m2/g, Pore Volume =0.64 cm3/g, Average Pore Diameter = 15.18nm when these parameters were increased, it led to the best operation condition of sulfur removal. The SEM images showed that the application of Co and Mo metals reaches more homogenous impregnation. The NH3-TPD result introduced the strong acidic sites of 5%Co10%Mo/γ-Al2O3. The obtained results proved that the total sulfur (all kind of sulfur in the feed) of light naphtha decreased from 160ppm to 20ppm during ODS process with the optimized catalyst. In that case, the kinetics of oxidative desulfurization of the optimized catalyst (5%Co10%Mo/γ-Al2O3) was studied. Moreover, a kinetic affinity model was utilized to determine the kinetic parameters of this reaction and the modeling results showed good agreement with experimental data.

Oxidative Desulfurization of DBT with H2O2 over 3DOM H3PW12O40/Al2O3 Catalyst

A series of heteropoly acid (HPA) based Al2O3 catalysts with three-dimensional ordered (3DOM) structure were synthesized by colloidal crystal template method. Interconnected macropores (250 nm) could be clearly observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Mesopores could be detected by N2 adsorption-desorption isotherms which further confirmed the 3DOM structural characteristics of catalyst. Moreover, Keggin-type HPW was highly dispersed in the Al2O3 framework, which suggested by powder X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR) results. The oxidation desulfurization (ODS) performance of 3DOM H3PW12O40/Al2O3 of refractory sulphur compounds was evaluated in the presence of hydrogen peroxide. It oxidized 98.5% of dibenzothiophene (DBT) into corresponding sulfone within 3 h, which exhibited superior ODS performance than corresponding mesoporous and microporous H3PW12O40/Al2O3 catalyst. The enhancement of ODS efficiency is related to the improvement of mass transfer of DBT in the pore channel resulting from the interconnected 3DOM structure. Furthermore, the as-prepared catalyst still demonstrates outstanding cycle performance after 6 runs, which could be easily recovered from the model fuel.

In situ bridging encapsulation of a carboxyl-functionalized phosphotungstic acid ionic liquid in UiO-66: A remarkable catalyst for oxidative desulfurization

This work describes a novel approach for linking metal–organic frameworks (MOFs) to polyoxometalates (POMs) for use as effective heterogeneous catalysts in the oxidative desulfurization of fuel oil. A POM-based MOF was synthesized in situ with a carboxyl-functionalized ionic liquid as a bridge to combine the POM and MOF. The resulting [mim(CH2)3COO]3PW@UiO-66 was characterized by XRD, N2 adsorption–desorption, FT-IR, SEM and TGA. The results indicated that the heteropolyanion-based ionic liquid [mim(CH2)3COOH]3PW was successfully dispersed within the cages of UiO-66. The catalyst [mim(CH2)3COO]3PW@UiO-66, which had a high content of the active component and large specific surface area, exhibited remarkable catalytic performance in oxidative desulfurization (100% DBT removal in 60 min). Importantly, a synergistic catalytic mechanism involving W = O and the Lewis acid, in which the Lewis acid promoted the decomposition of H2O2 and the generation of peroxotungstate (W(O2)n), was proposed to explain the high oxidative desulfurization catalytic efficiency of [mim(CH2)3COO]3PW@UiO-66.

Preparation of a AgCl/PbMoO4 Composite and Investigation of Its Photocatalytic Oxidative Desulfurization Performance.

PbMoO4 materials were synthesized by the glycerol and hydrothermal methods, and AgCl nanoparticles were loaded onto the surface of PbMoO4 by using the precipitation–deposition method. Finally, a AgCl/PbMoO4 photocatalyst was successfully prepared. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy (UV–vis-DRS) were used to characterize the phase composition, morphology, and light absorption characteristics of the catalyst. An n-octane solution of dibenzothiophene (DBT) was used to simulate fluid catalytic cracking to make gasoline. The photocatalytic oxidation performance of DBT under visible light was studied in terms of the type of light source as well as of the catalyst, substrate, and AgCl content. The mechanism of photocatalytic oxidation was also studied. The results show that AgCl loading causes a red shift of the absorption edge of PbMoO4, which improves the photocatalytic activity of the material. When the AgCl loading was 25.0%, the amount of catalyst was 1.5 g/L, and the visible light irradiation time was 2.0 h, the highest desulfurization rate of DBT reached 97.0%.

Enhancement of oxidative desulfurization performance over 3DOM H3PW12O40/TiO2 by HF treatment

Three-dimensional ordered (3DOM) H3PW12O40/TiO2 nanocomposites with anatase TiO2 exposed {001} facets are fabricated by HF treatment and applied as effective catalyst in oxidative desulfurization (ODS) process. The structure characterization results including SEM, TEM, XRD, N2 adsorption-desorption isotherms, XPS, and FT-IR confirm the different percentage of exposed {001} facets of anatase TiO2 and highly dispersion of Keggin-type phosphotungstic acid (HPW) on the 3DOM TiO2 framework. The ODS performance of as-fabricated catalysts suggests that the optimal ratio of the exposed {001} facets on anatase TiO2 is determined to be 26.83%, which exhibits superior catalytic activity for dibenzothiophene (DBT) than other catalysts. In addition, density functional theory (DFT) calculation has been applied to illustrate the influence of exposed {001} surface of anatase TiO2 on catalytic activity of catalyst.

Synthesis of carbon nitride supported amphiphilic phosphotungstic acid based ionic liquid for deep oxidative desulfurization of fuels

Abstract The wettability and the electron migration are considered as significant factors that deeply affect the catalytic oxidative desulfurization (ODS) performance. Herein, a long carbon chain modified phosphotungstic acid ionic liquid [C12mim]3PW12O40 (C12PW) is immobilized on the graphitic carbon nitride (g-C3N4) to enhance the dispersion properties both in the oil phase and H2O phase. Besides, verified by control experiments and various characterization methods, the migration of electron from g-C3N4 to C12PW and electron-rich W can accelerate the formation of superoxide radical, which further increases ODS efficiency. The optimal reaction conditions and parameters are determined by continuous orthogonal experiments, showing the superior oxidative ability of the immobilized catalyst C12PW/g-C3N4 on refractory aromatic sulfides in fuels. The after-reaction detection of the catalyst is also conducted, manifesting the dibenzothiophene in the fuels totally oxidized into dibenzothiophene sulfone, the only product after the reaction. The corresponding mechanism and kinetic model fitting are also proposed in this work, and the regeneration test manifests the good stability of immobilized catalyst C12PW/g-C3N4 in ODS.

Construction of 2D-2D V2O5/BNNS nanocomposites for improved aerobic oxidative desulfurization performance

In this study, 2D-2D nanocomposites were constructed based on V2O5 and exfoliated ultra-thin BN nanosheets (BNNS) via a facile solvothermal route. Detailed characterization results indicate the successful introduction of 2D V2O5 to the exfoliated BNNS carrier. The catalytic aerobic oxidation performance of the 2D-2D V2O5/BNNS nanocomposites was measured by catalytic oxidative desulfurization of oils with using molecular oxygen (O2) in the air as oxidant, providing an efficient desulfurization strategy to produce ultra-low S-content oils. Here, 99.6% removal of dibenzothiophene (DBT, ≤2 ppm) could be achieved under atmospheric pressure. Moreover, deep desulfurization of oils with different substrates and distractors could also be achieved. And the reaction system could be recycled for at least 7 times without any appreciable decrease of catalytic performance. The existence of BNNS could help to adsorb sulfides in oil phase, forming local high concentration of substrates on the surface of the catalyst, which could accelerate the reaction rate effectively. In addition, this study would also share new sights for the rational design and synthesis of binary nanocomposites for aerobic oxidation reactions.

Ionic liquid-based 3DOM meso/macroporous Mo/TiO2 materials with superior oxidation desulfurization performance at room temperature

Ionic liquid-based Mo/TiO2 catalyst with highly ordered meso/macroporous structure has been fabricated by two steps self-assembling and applied as catalyst for desulfurization in model fuel. The introduction of ordered secondary mesopores into interconnected macropores not only facilitates mass transfer efficiency of reactant molecules on pore channel, but also increases the internal exposed surface through ordered mesopores. Therefore, the catalytic activity of porous ionic liquid-based Mo/TiO2 catalyst on aromatic sulfur compounds has been significantly improved, 500 ppm of dibenzothiophene (DBT) in model fuel can be successfully removed within 100 min at room temperature. Furthermore, the selectivity for DBT oxidation of catalyst has also been explored in the presence of typical components in real fuel (alkane, olefine and aromatics). As-fabricated catalyst also exhibits excellent reusability even after 10 runs, which makes it a promising catalyst in industry.

Preparation of [EMIM]DEP/2C3H4O4 DESs and its oxidative desulfurization performance

ABSTRACT A series of [EMIM]DEP/nC3H4O4 (n = 1, 2, 3) deep eutectic solvents (DESs) were synthesized by heating and stirring the mixture of 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM]DEP) and propanedioic acid (C3H4O4). [EMIM]DEP/2C3H4O4 was characterized by Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA). Dibenzothiophene (DBT) in model oil was removed using the DESs as an extractant and catalyst, and H2O2 as an oxidant. The influence parameters of different systems, temperature, n(H2O2)/n(S), dosage of [EMIM]DEP/2C3H4O4, and the sulfide type on desulfurization were investigated. The experimental results show that removal rate of DBT can attach to 98.2%. FT-IR analysis of DBT, DESs, and the mixture (DBT-DESs) show that there is an interaction between DBT and DESs.

Oxidative Desulfurization Performance of CoAPO-5 Catalysts Synthesized by Novel Dynamic Hydrothermal Method

CoAPO-5 molecular sieves were synthesized by a novel dynamic method. Crystallization, morphology and surface acidity were investigated by XRD, SEM, and Py-IR in details, and compared with samples prepared by traditional static method. Synthesis conditions, reaction time, temperature and the amount of catalyst were optimized as important parameters. The desulfurization performance of CoAPO-5 catalysts synthesized by two different methods was evaluated and compared. Also, some experiments were carried out to test selectivity and regenerability of CoAPO-5 catalysts synthesized by the dynamic method. Finally, ODS reaction kinetics and mechanism using CoAPO-5 was studied and discussed. Results indicated that dynamic method greatly shortened crystallization time, while kept the same structure and sulfur removal capacity of CoAPO-5. The dynamic synthesis method could be considered as an alternative method to prepare porous molecular sieves.

Insight into the oxidative desulfurization mechanism of aromatic sulfur compounds over Ti-MWW zeolite: A computational study

Abstract The mechanism of aromatic sulfur compounds oxidized on Ti-MWW zeolite with H2O2 was studied by density functional theory. The results show that the adsorption capacity of solvents on Ti-η2-OOH decreases in the order of CH3COCH3> CH3OH > CH3CN > H2O. The energy barriers of thiophene on different active centers are in the order of Ti-η2-OOH-CH3CN benzothiophene > dibenzothiophene >4, 6-dimethyldibenzothiophene, confirming that Ti-MWW could provide sufficient space for the aromatic sulfur compounds with relatively large molecular size and has an excellent oxidation desulfurization performance. Our results address the controversy over the oxidation desulfurization reactivity of aromatic sulfur compounds by Ti-MWW in experimental studies and provide insights to further studies.

Synthesis of hierarchical porous BCN using ternary deep eutectic solvent as precursor and template for aerobic oxidative desulfurization

Abstract Boron carbon nitride (BCN) has exhibited superior aerobic catalytic performance in oxidation reactions. Herein, the hierarchical porous BCN catalyst was synthesized using a ternary deep eutectic solvent (DES) composed of boric acid, urea and choline chloride as the precursor and template. The as-prepared BCN exhibited impressive catalytic performance in oxidative desulfurization of fuel. Under the optimized conditions, the BCN catalyst can reach 98.4% sulfur removal in 4 h and recycle 5 times with a little activity decrease. Experimental results revealed that the excellent catalytic activity was found to be originated from an improved electron delocalization. Combined with the density functional theory (DFT), the improved electron delocalization increased the electronic density of the BCN, promoting the activation of dioxygen. This strategy provides a novel approach for the design of high-performance catalyst in oxidative desulfurization.

In situ hydrothermal preparation and photocatalytic desulfurization performance of graphene wrapped TiO2 composites

Organosulfur impurities in fuels cause severe environmental pollution and poison the catalysts used in vehicle exhausts’ gas converters. Here we developed a facile “In suithydrothermal” method to prepare reduced graphene oxide (RGO) supported TiO2 catalyst and applied it for oxidative desulfurization of thiophene(T) in model fuel. The RGO/TiO2 catalysts were characterized by FT-IR, XPS, SEM, XRD and UV–Vis spectroscopy. The photocatalytic properties were evaluated by the degradation of thiophene in model fuel. The catalytic activity of RGO/TiO2 composites for the oxidation of thiophene in n-octane is relatively higher than those of pure GO or TiO2 power. Moreover, the thiophene conversion rate reached 94.3% with RGO/TiO2 composite catalyst after treatment for 100 min at atmospheric pressure. The graphene oxide is partially reduced during the “in situ hydrothermal” process. The photocatalysis mechanism indicated that RGO/TiO2 photocatalysts are facilitating to electron transfer fromTiO2 to RGO and enhance the adsorption of the target pollutants to improve the oxidative desulfurization (ODS) performance.

Boosting aerobic oxidative desulfurization performance in fuel oil via strong metal-edge interactions between Pt and h-BN

Platinum nanoparticles (Pt NPs) have long been regarded as efficient catalysts for numerous catalytic process, including catalytic oxidation, hydrogenation, etc. For Pt catalysis, tuning the electronic structure for a boosted catalytic performance and exploring a proper strategy for stabilization of the nanoparticles are the two central issues. In this work, we constructed strong metal-edge interactions (SMEI) between well-dispersed Pt NPs and hexagonal boron nitride (h-BN) support. The charge transfer between h-BN and Pt NPs was carefully studied, and it was found that the charge transfers from B atoms in h-BN to Pt NPs and from Pt NPs to N atoms in h-BN. The SMEI makes the Pt NPs positively charged for a boosted aerobic catalytic desulfurization activity with sulfur removals of 98.3%, 96.5%, 93.7% and 85.9% to dibenzothiophene, 4, 6-dimethyldibenzothiophene, 4-methylbenzothiophene, and benzothiophene, respectively. Additionally, the aerobic oxidative desulfurization system showed an excellent resistance performance to olefins and aromatic hydrocarbons. The SMEI also gives rise to an excellent stabilization of the Pt NPs without agglomeration after the reaction. Moreover, the catalyst can be recycled 5 times without a significant decrease in catalytic activity. Additionally, both the geometric structure and the SMEI were well investigated to illuminate the structure-activity relationship.