Catalytic Performance In Oxidative Desulfurization Research Articles

Controllable Synthesis of Titanium Silicon Molecular Zeolite Nanosheet with Short b-Axis Thickness and Application in Oxidative Desulfurization.

Titanium silicon molecular zeolite (TS-1) plays an important role in catalytic reactions due to its unique nanostructure. The straight channel on TS-1 was parallel to the orientation of the short b-axis and directly exposed to the aperture of the 10-member ring with a diameter of 0.54 nm × 0.56 nm. This structure could effectively reduce the diffuse restriction of bulk organic compounds during the oxidative desulfurization process. As a kind of cationic polymer electrolyte, polydimethyldiallyl ammonium chloride (PDDA) contains continuous [C8H16N+Cl-] chain segments, in which the Cl- could function as an effective structure-directing agent in the synthesis of nanomaterials. The chain of PDDA could adequately interact with the [0 1 0] plane in the preparation process of zeolite, and then the TS-1 nanosheet with short b-axis thickness (6 nm) could be obtained. The pore structure of the TS-1 nanosheet is controlled by regulating the content of PDDA. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 physical adsorption analysis, infrared absorption spectrum and ultraviolet-visible spectrum were used to determine the TS-1. The thinner nanosheets exhibit excellent catalytic performance in oxidative desulfurization of dibenzothiophene (DBT), in which the removal rate could remain at 100% after three recycles. Here, the TS-1 nanosheet with short b-axis thickness has a promising future in catalytic reactions.

Completely Inorganic Deep Eutectic Solvents for Efficient and Recyclable Liquid-Liquid Interface Catalysis.

Organic acid-based deep eutectic solvents (DESs) as catalysts always suffer from weak stability and low recyclability due to the accumulation of organic oxidative products in the DES phase. Herein, a completely inorganic deep eutectic solvent (IDES) ZnCl2/PA with zinc chloride (ZnCl2) and phosphoric acid (PA) as precursors is constructed to realize liquid-liquid interface catalysis for desulfurization of fuel and product self-separation for the first time. Owing to the inorganic nature, the organic oxidative products are accumulated at the interface between the IDES and fuel rather than the IDES phase. With this unique feature, the IDES can be reused for at least 15 times without any further treatment in oxidative desulfurization process, showing a state-of-the-art cycle-regeneration stability. Moreover, compared with the reported organic DESs, the IDES also reveals more attractive catalytic oxidative desulfurization performance. Experimental and theoretical studies indicate that the strong coordination Zn···O═P and the strong adsorption energy between IDES and sulfides enhance the activation of H2O2 to reactive oxygen species, leading to the superior catalytic performance in oxidative desulfurization of fuel.

Catalytic oxidative desulfurization performance of a modified nano-sized β zeolite loaded with different structural polyoxometalates

HPW/β-T+S has the best desulfurization activity among the composite catalysts supported by polyoxometalates with different structures.

Magnetically recyclable high-entropy metal oxide catalyst for aerobic catalytic oxidative desulfurization

High-entropy metal oxide catalysts have demonstrated exceptional performance in activating oxygen for catalytic oxidation reactions. However, ensuring their ease of cyclic usage is crucial to broadening their applications. To address this challenge, a magnetic and recyclable high-entropy metal oxide catalyst is designed and its potential in catalytic oxidative desulfurization of fuel oils with oxygen as the oxidant is also investigated. Through a mechanochemical-assisted calcination method, the magnetic high-entropy metal oxide catalyst (HEMO-900) is successfully synthesized, and the structure of the HEMO-900 catalyst is comprehensively characterized. In addition, it is found that the high-entropy structure facilitates charge modulation of the active components, thereby enhancing the oxygen activation performance. The HEMO-900 catalyst exhibits exceptional oxygen activation ability and catalytic oxidative desulfurization performance, and 96.9% of sulfur removal is achieved under optimal conditions. In addition, it achieves profound desulfurization of various fuel samples by efficiently oxidizing and eliminating diverse aromatic sulfur compounds. Additionally, the catalyst demonstrates outstanding magnetically recyclable properties, enabling rapid separation and recovery from the fuel oil phase through the application of an external magnetic field, making the HEMO-900 catalyst maintained a remarkable sulfur removal efficiency of 91.1% even in the 5th cycle. Therefore, this magnetically recyclable HEMO-900 catalyst possesses significantly promising research and application prospects in the field of catalytic oxidative desulfurization of fuel oils with oxygen as the oxidant, as well as some other heterogeneous catalysis.

Integrated oxidative-adsorptive desulfurization of model and real fuel oils over a Zn-impregnated hydroxyapatite-activated carbon (Zn/HA-AC) composite

Herein, a Zn-impregnated hydroxyapatite-activated carbon (Zn/HA-AC) composite catalyst was fabricated and was, in turn, applied for the desulfurization of a model and real oil samples via the integrated adsorptive-oxidative desulfurization strategy. Activity results revealed that Zn/HA and AC (25:75) realized 76.7% dibenzothiophene (DBT) adsorptive desulfurization at 50 °C in 60 min reaction time at an adsorbent dose of 0.14 g/20 mL of feed. Zn/HA-AC(25:75) composite catalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, and scanning electron microscopy analysis. In the oxidative desulfurization (ODS) combined with adsorptive desulfurization experiments, under the optimum conditions of 45 oC temperature for 60 min and a catalyst dose of 0.1 g/20 mL of feed using H2O2 and HCOOH, Zn/HA-AC (25:75) achieved 93% DBT conversion. Under these optimized experimental parameters, the adsorptive desulfurization and catalytic ODS performance (% DBT conversion) of Zn/HA-AC (25:75) for real gasoline, kerosene, and diesel oil reached 18, 31 and 15%, and 31.66, 55.31 and 11.19%, respectively. Contrary to this, under the integrated catalytic-oxidative-adsorptive experiments, the desulfurization performance of Zn/HA-AC (25:75) for gasoline, kerosene, and diesel oil reached 61, 41, and 34%, respectively.

Boosting Catalytic Oxidative Desulfurization Performance over Yolk-Shell Nickel Molybdate Fabricated by Defect Engineering.

Developing catalysts with optimized surface properties is significant for advanced catalysis. Herein, a rational architectural design is proposed to successfully synthesize yolk-shell nickel molybdate with abundant oxygen vacancies (YS-VO-NMO) via an acid-assisted defect engineering strategy. Notably, YS-VO-NMO with the yolk-shell structure shows complex nanoconfined interior space, which is beneficial to the mass transfer and active sites exposure. Moreover, the defect engineering strategy is of great importance to modulate the surface electronic structure and atomic composition, which contributes to the enrichment of oxygen vacancies. Benefiting from these features, the higher hydrogen peroxide activation is achieved by YS-VO-NMO to produce more hydroxyl radicals compared with untreated nickel molybdate. Consequently, the defect-engineered YS-VO-NMO not only features superior catalytic activity (99.5%) but also retains high desulfurization efficiency after recycling eight times. This manuscript provides new inspiration for designing more promising defective materials via defect engineering and architecture for different applications besides oxidative desulfurization.

Ti-MOF single-crystals featuring an intracrystal macro-microporous hierarchy for catalytic oxidative desulfurization.

For the first time, we demonstrate a Ti-MOF (Ti-metal organic framework) single-crystal featuring an intracrystal macro-microporous hierarchy (Hier-NTU-9) by a vapor-assisted polymer-templated method. This Hier-NTU-9 possesses macropores (100-1000 nm) derived from polymer templates and enhanced transport ability of bulky molecules, exhibiting almost double the desulfurization activity compared to the conventional NTU-9.

Construction of Mo-MOF-derived molybdenum dioxide on carbon nanotubes with tunable nitrogen content and particle size for oxidative desulfurization

The combination of distinctive properties of carbon nanotubes and metal oxides is expected to exploit novel catalysts offering high catalytic ability. Herein, a nano-sized MoO2 derived from molybdenum-based metal-organic framework was anchored on the surface of carbon nanotubes (CNT) with urea as a regulator. Powder X-ray diffraction analysis suggested that the nitrogen content and the MoO2 particle size of the as-prepared catalyst could be tuned by changing the urea dosage and the calcination temperature. Elemental mapping indicated the homogeneous dispersion of the nano-sized MoO2 on the surface of CNT for MoO2@CNT-U7.5 (U7.5 represents mass ratio of urea to CNT). Compared with MoO2@CNT treated in absence of urea, MoO2@CNT-U7.5 showed extremely higher catalytic performance in oxidative desulfurization of fuel. With H2O2 as an oxidant, the removal of refractory sulfur compounds including dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene can reach >99% within 40 min at the reaction temperature of 50 °C. In addition, the catalyst exhibited superior cycling stability and could be recycled for eight times with little loss of sulfur removal. The reaction mechanism was eventually proposed with the assistance of GC–MS and ESR analysis.

High temperature oxidizing-resistant magnetic high entropy catalyst for efficient oxidative desulfurization

Engineering a magnetic response catalyst for ultra-deep oxidative desulfurization of diesel is a valid strategy for recycling. However, for traditional magnetic response catalysts, high temperature is unfavorable, which will induce demagnetization. In this work, a high entropy structure was proposed to construct a magnetic response MoFeNiCuCoOx-1100 (HEO-1100) catalyst by the ion substitution method. Because of the high-entropy effect, the metallic elements in HEO-1100 showed electron-deficiency status, making the magnetism could be retained after 1100 °C treatment. Moreover, detailed characterizations showed that the oxidative desulfurization active sites, molybdenum oxide, were uniformly dispersed in the HEO-1100, which was beneficial to the promotion of oxidative desulfurization. Because of the electron-deficient structure along with the high dispersion of active sites, the HEO-1100 catalyst possessed significantly enhanced catalytic performance in oxidative desulfurization with oxygen as an oxidant. Especially, owing to the magnetism, the HEO-1100 catalyst could be readily separated and still exhibited high catalytic activity after 18 times recycling. Furthermore, the desulfurization product, sulfone, could be separated, which was a high-value-added product for medicine.

Synergistic effect of –COOH and Zr(IV) with a short distance in Zr-MOFs for promoting utilization of H2O2 in oxidative desulfurization

The effectiveness of the catalytic oxidative desulfurization (CODS) process crucially depends on the catalytic activity of the catalyst and the utilization of oxidizing agent. Catalyst with multiple active sites is an effective method to improve the CODS effectiveness. The Zr(IV) and –COOH-containing metal–organic framework, UiO-66-(COOH)2, was synthesized and used as an active and recyclable catalyst for CODS. The UiO-66-(COOH)2 shows higher catalytic activity and H2O2 utilization in the CODS process than UiO-66/–COOH, UiO-66, and H2BDC. And the high catalytic performance is derived from the synergistic effect between the Zr(IV) open site and free –COOH functionality within the framework. Experimental analysis and DFT calculations results indicate that the synergistic effect, which changes the reaction path and protects the *O2– radical, is a very effective strategy to promote desulfurization efficiency and the utilization efficiency of H2O2. In addition, it is essential to highlight that the active-site distance also has a significant influence on the effectiveness of CODS. This research may provide a new avenue for improving the CODS performance.

Electronic state tuning over Mo-doped W18O49 ultrathin nanowires with enhanced molecular oxygen activation for desulfurization

Developing catalyst with abundant surface active sites is the core issue to achieve efficient catalytic oxidative desulfurization performance. In this work, Mo doped W18O49 ultrathin nanowires is fabricated through solvothermal method to provide plentiful low coordinated metal atoms around oxygen vacancies to trigger oxidative desulfurization reaction. As a non-stoichiometric oxide, the discorded lattice microstructure in W18O49 endows the formation of O vacancies neighboring low-valence W atoms, while the ultrathin structure ensure the fully exposure of surface atoms. Moreover, the doped Mo atoms will tune the surface atomic structure and electronic state of W18O49 nanowires, leading to the higher oxygen vacancy concentration and strengthened interaction with target sulfide molecules. Benefiting from these features, the higher molecular oxygen activation capacity can be realized over Mo-W18O49 nanowires to yield more superoxide radicals, making it with greatly improved oxidative desulfurization performance. The optimized 2 %Mo-W18O49 catalyst shows nearly 100% removal of dibenzothiophene within 5 h and maintain the good cycle stability. This work supply new insights for the design of catalytic sites towards selective catalytic oxidative desulfurization.

Steam-assisted strategy to fabricate Anatase-free hierarchical titanium Silicalite-1 Single-Crystal for oxidative desulfurization

As an important heterogeneous catalyst, Titanium Silicalite-1 (TS-1) zeolite has been widely applied in various catalytic processes. Here, hierarchical TS-1 single-crystals were successfully synthesized by a steam-assisted crystallization strategy using hierarchically porous titanium-containing silica (Ti-NKM-5) as a precursor. Due to the presence of large mesopores (10–40 nm)， the microporous structure-directing agents penetrated the interstitial structure of silica particles, inducing the dissolution and crystallization process. During crystallization, the generated nanocrystals grew together to form a hierarchical structure. Titanium was fully incorporated into the zeolite framework, and no extra-framework anatase was formed. Compared with the traditional microporous TS-1 zeolite, the synthesized hierarchical TS-1 single-crystal exhibited superior catalytic performance in oxidative desulfurization (ODS) of dibenzothiophene (DBT) and 4, 6-dimethyl dibenzothiophene (4, 6-DMDBT) owing to the hierarchically porous and anatase-free structure. The recycling test revealed the durability of the obtained hierarchical TS-1 catalyst under moderate reaction conditions.

Advances in Oxidative Desulfurization of Fuel Oils over MOFs-Based Heterogeneous Catalysts

Catalytic oxidative desulfurization (ODS) of fuel oils is considered one of the most promising non-hydrodesulfurization technologies due to the advantages of mild reaction conditions, low cost and easy removal of aromatic sulfur compounds. Based on this reason, the preparation of highly efficient ODS catalysts has been a hot research topic in this field. Recently, metal-organic frameworks (MOFs) have attracted extensive attention due to the advantages involving abundant metal centers, high surface area, rich porosity and varied pore structures. For this, the synthesis and catalytic performance of the ODS catalysts based on MOFs materials have been widely studied. Until now, many research achievements have been obtained along this direction. In this article, we will review the advances in oxidative desulfurization of fuel oils over MOFs-based heterogeneous catalysts. The catalytic ODS performance over various types of catalysts is compared and discussed. The perspectives for future work are proposed in this field.

Oxidative Desulfurization Catalyzed by Phosphotungstic Acid Supported on Hierarchical Porous Carbons.

A hierarchical porous carbon material (HPC) with an ultra-high specific surface area was synthesized with sisal fiber (SF) as a precursor, and then H3PW12O40·24H2O (HPW) was immobilized on the support of SF-HPC by a simple impregnation method. A series characterization technology approved that the obtained SF-HPC had a high surface area of 3152.46 m2g−1 with micropores and macropores. HPW was well-dispersed on the surface of the SF-HPC support, which reduced the loading of HPW to as low as 5%. HPW/SF-HPW showed excellent catalytic performance for oxidative desulfurization, and the desulfurization rate reached almost 100% under the optimal reaction conditions. The desulfurization rate of HPW/SF-HPW could be maintained at above 94% after four recycles.

Controllable electronic effect via deep eutectic solvents modification for boosted aerobic oxidative desulfurization

Tuning electronic structure of metal catalysts by organic modification is an efficient strategy for domination of their catalytic performances. However, the electronic structure tuning over metal-free catalysts remains to be a challenge. In this work, an organic modification strategy with deep eutectic solvents (DES) as organic modifier over metal-free catalysts was proposed to tune the electronic structure of hexagonal boron nitride (h-BN). Detailed experiments showed that the electronic properties of h-BN was rationally tuned by the introduced DES, in which the B atoms in h-BN were positively charged. Meanwhile, the modulated electronic properties can lower the activation energy for the generation of hydroxyl radicals (•OH) from hydrogen peroxide (H2O2), thus leading to a promoted catalytic performance in oxidative desulfurization. This finding may pave a new strategy for tuning metal-free catalysts with highly-active catalytic performance.

Deep catalytic oxidative desulfurization process catalyzed by TBA-PWFe@NiO@BNT composite material as an efficient and recyclable phase-transfer nanocatalyst

The production of high-quality fuel with substantially lowered sulfur level has attracted a great deal of attention in recent years. Developing high-performance and recyclable catalysts for the desulfurization process remains largely a challenge. In this study, an efficient catalytic oxidative desulfurization (CODS) strategy has been developed using a new phase-transfer nanocatalyst. The TBA-PWFe@NiO@BNT nanocatalyst was fabricated from the mono Fe-substituted phosphotungstate with tetra (n-butyl) ammonium chains (TBA-PWFe), nickel oxide (NiO), and sodium activated bentonite (BNT) for the first time. The TBA-PWFe@NiO@BNT composite was utilized as a recyclable nanocatalyst for the desulfurization of simulated fuels and real gasoline using acetic acid/hydrogen peroxide (VCH3COOH/VH2O2 = 1/2). The best desulfurization results were attained with the TBA-PWFe@NiO@BNT phase-transfer nanocatalyst at 35 °C after just 60 min, showing identical CODS performance under mild reaction conditions. The total sulfur removal efficiency of real gasoline achieved a remarkable 98% and the concentration of mercaptans (RSH; R = alkyl group) was reduced from 98 to 3 ppm. On the other hand, thiophenes (Ts), benzothiophenes (BTs), and dibenzothiophenes (DBTs) were near completely removed from the simulated fuels phase with efficiencies of 96, 97, and 99%, respectively. Finally, the recycling capacity of TBA-PWFe@NiO@BNT nanocatalyst was confirmed for five consecutive desulfurization runs without remarkably decreases in its catalytic performance. The overall results obtained have been discussed in detail.

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.

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.

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.