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.

Confined Heteropoly Blues in Defected Zr-MOF (Bottle Around Ship) for High-Efficiency Oxidative Desulfurization

The Keggin-type polyoxometalates (POMs) are effective catalysts for oxidative desulfurization (ODS) and confining these POMs in metal-organic frameworks (MOFs) is a promising strategy to improve their performances. Herein, postsynthetic modification of POMs confined in MOFs by adding thiourea creates more unsaturated metal sites as defects, promoting ODS catalytic activity. Additional modification by confining 1-butyl-3-methyl imidazolium POMs in MOFs is performed to obtain higher ODS activity, owing to the affinity between electron-rich thiophene-based compounds and electrophilic imidazolium compounds. The ODS catalytic activities of four Zr-MOF-based composites (bottle around ship) including phosphomolybdate acid (PMA)/UiO-66, [Bmim]₃ PMo₁₂ O₄₀ /UiO-66, PMA/Thiourea/UiO-66, and [Bmim]₃ PMo₁₂ O₄₀ /Thiourea/UiO-66 are therefore investigated in detail. In order to explore the catalytic mechanism of these MOF composites, their microstructures and electronic structures are probed by various techniques such as X-ray diffraction, thermogravimetric analysis, Fourier transform infrared, Raman, scanning electron microscope, transmission electron microscope, BET, X-ray photoelectron spectroscopy, EPR, UV-vis, NMR spectra, and H₂ -temperature-programmed reduction. The results reveal that phosphomolybdate blues and imidazolium phosphomolybdate blues with different Mo⁵⁺ /Mo⁶⁺ ratios with the Keggin structure are confined in defected UiO-66 for all four composites. This approach can be applied to design and synthesize other POMs/MOFs composites as efficient catalysts.

Tungsten Nitride, Well-Dispersed on Porous Carbon: Remarkable Catalyst, Produced without Addition of Ammonia, for the Oxidative Desulfurization of Liquid Fuel

Polyanilines (pANIs), loaded with phosphotungstic acid (PTA), are pyrolyzed to get WO₃ or W₂ N (≈6 and ≈7 nm, respectively), which is well-dispersed on pANI-derived porous carbons (pDCs). Depending on the pyrolysis temperature, WO₃ /pDC, W₂ N/pDC, or W₂ N-W/pDCs could be obtained selectively. pANI acts as both the precursor of pDC and the nitrogen source for the nitridation of WO₃ into W₂ N during the pyrolysis. Importantly, W₂ N could be obtained from the pyrolysis without ammonia feeding. The obtained W₂ N/pDC is applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of liquid fuel for the first time, and the results are compared with WO₃ /pDC and WO₃ /ZrO₂ . The W₂ N/pDC is very efficient in ODS with remarkable performance compared with WO₃ /pDC or WO₃ /ZrO₂ , which is applied as a representative ODS catalyst. For example, W₂ N/pDC shows around 3.4 and 2.7 times of kinetic constant and turnover frequency (based on 5 min of reaction), respectively, compared to that of WO₃ /ZrO₂ . Moreover, the catalysts could be regenerated in a facile way. Therefore, W₂ N/pDC could be produced facilely from pyrolysis (without ammonia feeding) of PTA/pANI, and W₂ N, well-dispersed on pDC, can be suggested as a very efficient oxidation catalyst for the desulfurization of liquid fuel.

Fabrication of various morphological forms of a g-C3N4-supported MoO3 catalyst for the oxidative desulfurization of dibenzothiophene

The tubular structure of g-C₃N₄ supported-MoO₃ catalysts exhibits an excellent desulfurization performance due to full exposure of active sites.

Heteropoly acid supported on sodium dodecyl benzene sulfonate modified layered double hydroxides as catalysts for oxidative desulfurization

The HPW/MgAl-LDH-DBS catalyst was synthesized, and the removal of DBT was almost 100% under the optimal conditions.

Desulfurization of JP-8 jet fuel: challenges and adsorptive materials

This review describes ongoing efforts to remove the bulky organosulfur compounds from Jet Propellant 8 (JP-8) that cannot be removed by hydrodesulfurization.

TiO2-Containing Carbon Derived from a Metal-Organic Framework Composite: A Highly Active Catalyst for Oxidative Desulfurization

A new metal-organic framework (MOF) composite consisting of Ti- and Zn-based MOFs (ZIF-8(x)@H₂N-MIL-125; in brief, ZIF(x)@MOF) was designed and synthesized. The pristine MOF [H₂N-MIL-125 (MOF)]- and an MOF-composite [ZIF(30)@MOF]-derived mesoporous carbons consisting of TiO₂ nanoparticles were prepared by pyrolysis (named MDC-P and MDC-C, respectively). MDC-C showed a higher surface area, larger pore sizes, and larger mesopore volumes than MDC-P. In addition, the TiO₂ nanoparticles on MDC-C have more uniform shapes and sizes and are smaller than those of MDC-P. The obtained MDC-C and MDC-P [together with MOF, ZIF(30)@MOF, pure/nanocrystalline TiO₂, and activated carbon] were applied in the oxidative desulfurization reaction of dibenzothiophene in a model fuel. The MDC-C, even with a lower TiO₂ content than that of MDC-P, showed an outstanding catalytic performance, especially with a very low catalyst dose (i.e., a very high quantity of dibenzothiophene was converted per unit weight of the catalyst), fast kinetics (∼3 times faster than that for MDC-P), and a low activation energy (lower than that for any reported catalyst) for the oxidation of dibenzothiophene. The large mesopores of MDC-C and the well-dispersed/small TiO₂ might be the dominant factors for the superior catalytic conversions. The oxidative desulfurization of other sulfur-containing organic compounds with various electron densities was also studied with MDC-C to understand the mechanism of catalysis. Moreover, the MDC-C catalyst can be reused many times in the oxidative desulfurization reaction after a simple washing with acetone. Finally, composing MOFs and subsequent pyrolysis is suggested as an effective way to prepare a catalyst with well-dispersed active sites, large pores, and high mesoporosity.

Synthesis of mesoporous WO3/TiO2 catalyst and its excellent catalytic performance for the oxidation of dibenzothiophene

DBT could be completely oxidized to DBT sulfone (DBTO₂) with the help of WO₃/TiO₂ catalyst and H₂O₂.

A multicomponent assembly approach for the design of deep desulfurization heterogeneous catalysts

An assembly approach has been employed for the preparation of a multi-component heterogeneous catalyst showing high efficiency in deep desulfurization processes.

Nanocomposites of polymer brush and inorganic nanoparticles: preparation, characterization and application

We tackle in this review the use of a subset of polymer brushes (e.g., polyelectrolytes and polyampholytes) for the embedment of inorganic NPs to make composite surfaces/NPs with specific functions.

TiO2 microspheres supported polyoxometalate-based ionic liquids induced catalytic oxidative deep-desulfurization

A series of TiO₂ microspheres supported [SiW₁₂O₄₀]⁴⁻-based ionic liquids were successfully prepared and used as catalysts in oxidative desulfurization system. DBT was oxidized to DBT sulfone (DBTO₂) efficiently with the help of the catalyst and H₂O₂.

Supported ionic liquid [Bmim]FeCl4/Am TiO2 as an efficient catalyst for the catalytic oxidative desulfurization of fuels

Supported ionic liquid catalyst [Bmim]FeCl₄/Am TiO₂ was synthesized and showed excellent desulfurization efficiency and reuseable performance in the ECODS system.