Direct synthesis of mesoporous (C19H42N)4H3(PW11O39)/SiO2 and its catalytic performance in oxidative desulfurization

Oxidative Desulfurization of Fuel Oil Catalyzed by Carbon Nitride Supported Phosphotungstic Acid Based Dicationic Ionic Liquid

In this study, a novel phosphotungstic acid based dicationic ionic liquid [C2(MIM)2]PW12O40 was successfully prepared and immobilized on graphitic carbon nitride (g-C3N4). The supported catalysts wt% [C2(MIM)2]PW12O40/g-C3N4 (wt=3%, 10%, 30%,...

Polyoxometalate Dicationic Ionic Liquids as Catalyst for Extractive Coupled Catalytic Oxidative Desulfurization

Wettability is an important factor affecting the performance of catalytic oxidative desulfurization. In order to develop an efficient catalyst for the extractive coupled catalytic oxidative desulfurization (ECODS) of fuel oil by H2O2 and acetonitrile, a novel family of imidazole-based polyoxometalate dicationic ionic liquids (POM-DILs) [Cn(MIM)2]PW12O40 (n = 2, 4, 6) was synthesized by modifying phosphotungstic acid (H3PW12O40) with double imidazole ionic liquid. These kinds of catalysts have good dispersity in oil phase and H2O2, which is conducive to the deep desulfurization of fuel oil. The catalytic performance of the catalysts was studied under different conditions by removing aromatic sulfur compound dibenzothiophene (DBT) from model oil. Results showed that [C2(MIM)2]PW12O40 had excellent desulfurization efficiency, and more than 98% of DBT was removed under optimum conditions. In addition, it also exhibited good recyclability, and activity with no significant decline after seven reaction cycles. Meanwhile, dibenzothiophene sulfone (DBTO2), the only oxidation product of DBT, was confirmed by Gas Chromatography-Mass Spectrometry (GC-MS), and a possible mechanism of the ECODS process was proposed.

Confining Polyoxometalate Clusters into Porous Aromatic Framework Materials for Catalytic Desulfurization of Dibenzothiophene

Removal of notorious sulfur compounds to produce low-sulfur-content (≤10 ppm) diesel is necessary and vital for modern industry and environmental protection. A new type of inorganic-organic hybrid material has been designed and synthesized via confining molybdenum-containing polyoxometalate (POM) clusters within porous aromatic framework-1 (PAF-1) cavities named POM-PAF-1. Deep oxidative desulfurization experiments reveal that POM-PAF-1 possesses excellent reactivity under mild conditions, exemplified by a sulfur removal degree of 98.5% dibenzothiophene within 30 min at 30 °C. The improvement in oxidative desulfurization reactivity from traditional porous POM-based catalysts is owing to uniform POMs and lipophilic and porous PAF-1. The high performance of POM-PAF-1 in terms of excellent reactivity and good stability means it has potential in new heterogeneous catalysis.

Recent Advances in Functionalized Mesoporous Silica Frameworks for Efficient Desulfurization of Fuels

Considerable health and climate benefits arising from the use of low-sulfur fuels has propelled the research on desulfurization of fossil fuels. Ideal fuels are urgently needed and are expected to be ultra-low in sulfur (10-15 ppm), with no greater than 50 ppm sulfur content. Although several sulfur removal techniques are available in refineries and petrochemical units, their high operational costs, complex operational needs, low efficiencies, and higher environmental risks render them unviable and challenging to implement. In recent years, mesoporous silica-based materials have emerged as promising desulfurizing agents, owing to their high porosity, high surface area, and easier functionalization compared to conventional materials. In this review, we report on recent progress in the synthesis and chemistry of new functionalized mesoporous silica materials aiming to lower the sulfur content of fuels. Additionally, we discuss the role of special active sites in these sorbent materials and investigate the formulations capable of encapsulating and trapping the sulfur-based molecules, which are challenging to remove due to their complexity, for example the species present in JP-8 jet fuels.

Hierarchical porous HPW/titania–silica material with superior adsorption-catalytic oxidation activity for multi-ring thiophenic sulfur compounds

HPW/titania–silica catalysts with micro-meso-macroporous structures and high specific surface areas are prepared and applied as oxidative desulfurization catalysts.

Mesoporous Silica vs. Organosilica Composites to Desulfurize Diesel

The monolacunary Keggin-type [PW₁₁O₃₉]⁷⁻ (PW₁₁) heteropolyanion was immobilized on porous framework of mesoporous silicas, namely SBA-15 and an ethylene-bridged periodic mesoporous organosilica (PMOE). The supports were functionalized with a cationic group (N-trimethoxysilypropyl-N, N, N-trimethylammonium, TMA) for the successful anchoring of the anionic polyoxometalate. The PW₁₁@TMA-SBA-15 and PW₁₁@TMA-PMOE composites were evaluated as heterogeneous catalysts in the oxidative desulfurization of a model diesel. The PW₁₁@TMA-SBA-15 catalyst showed a remarkable desulfurization performance by reaching ultra-low sulfur levels (<10 ppm) after only 60 min using either a biphasic extractive and catalytic oxidative desulfurization (ECODS) system (1:1 MeCN/diesel) or a solvent-free catalytic oxidative desulfurization (CODS) system. Furthermore, the mesoporous silica composite was able to be recycled for six consecutive cycles without any apparent loss of activity. The promising results have led to the application of the catalyst in the desulfurization of an untreated real diesel supplied by CEPSA (1,335 ppm S) using the biphasic system. The system has proved to be a highly efficient process by reaching desulfurization values higher than 90% for real diesel during three consecutive cycles.

Catalytic Pyrolysis of Low Density Polyethylene Using Cetyltrimethyl Ammonium Encapsulated Monovacant Keggin UnitsC19H42N4H3(PW11O39)and ZSM-5

The effect of the catalysts on the pyrolysis of commercial low density polyethylene (LDPE) has been studied in a batch reactor. The thermal catalytic cracking of the LDPE has been done using cetyltrimethyl ammonium encapsulated monovacant keggin units (C19H42N)4H3(PW11O39), labeled as CTA-POM and compared with the ZSM-5 catalyst. GC-MS results showed that catalytic cracking of LDPE beads generated oilier fraction over CTA-POM as compared to ZSM-5. Thus, the use of CTA-POM is more significant because it yields more useful fraction. It was also found that the temperature required for the thermal degradation of LDPE was lower when CTA-POM was used as a catalyst while high temperature was required for degradation over ZSM-5 catalyst. Better activity of CTA-POM was due to hydrophobic nature of CTA moiety which helps in catalyst mobility and increases its interaction with hydrocarbons.

Ultra-deep desulfurization via reactive adsorption on peroxophosphomolybdate/agarose hybrids

A catalyst system composed of peroxophosphomolybdates as catalytic center and agarose as matrix material had been designed. The [C16H33N(CH3)3]3[PO4{MoO(O2)2}4]/agarose (C16PMo(O2)2/agarose) hybrid was found to be active for oxidation desulfurization (ODS) of dibenzothiophene (DBT) or real fuel into corresponding sulfone by H2O2 as an oxidant, while the sulfur content could be reduced to 5ppm. The higher activity comes from its components including [PO4{MoO(O2)2}4] catalytic sites, the hydrophobic quaternary ammonium cation affinity to low polarity substrates, and agarose matrix affinity to H2O2 and sulfone. During the oxidative reaction, the mass transfer resistance between H2O2 and organic sulfurs could be decreased and the reaction rate could increase by the assistance of agarose and hydrophobic tails of [C16H33N(CH3)3]3[PO4{MoO(O2)2}4]. Meanwhile, the oxidative products could be adsorbed by agarose matrix to give clean fuel avoiding the post-treatment. In addition, the hybrid was easily regenerated to be reused.

Novel catalyst by immobilizing a phosphotungstic acid on polymer brushes and its application in oxidative desulfurization

In the study, an HPW–PDMAEMA–SiO₂ (phosphotungstic acid (HPW); poly-N,N-dimethylaminoethyl methacrylate (PDMAEAM)) catalyst was successfully synthesized.