Zijiang Jiang

One-pot depolymerization of cellulose into glucose and levulinic acid by heteropolyacid ionic liquid catalysis

A series of heteropolyacid (HPA) ionic liquids [C4H6N2(CH2)3SO3H]3−nHnPW12O40 ([MIMPSH]nH3−nPW12O40, n = 1, 2 3, abbreviated as [MIMPSH]nH3−nPW) was used to catalyze one-pot depolymerization of cellulose into glucose. Their performances were much better than those of the previously reported HPAs, such as H3PW12O40, Cs2.5H0.5PW12O40. Besides cellulose, the HPA ionic liquids were able to catalyze the conversion of sucrose and starch into glucose. In addition, one-pot synthesis of levulinic acid (LA) directly from cellulose was realized using these HPA ionic liquid catalysts in a water–methyl isobutyl ketone (MIBK) biphasic system. The separation of the products and catalysts was easy, and the retrieved [MIMPSH]nH3−nPW could be repeatedly used without appreciable loss of performance.

Conversion of highly concentrated fructose into 5-hydroxymethylfurfural by acid–base bifunctional HPA nanocatalysts induced by choline chloride

A series of acid–base bifunctional heteropolyacids (HPAs) (C6H15O2N2)3−xHxPW12O40 (abbreviated as Ly3−xHxPW) have been designed using different ratios of HPAs with amino acid lysine in order to control their acid–base properties. The amino acid group facilitated the HPAs forming micellar assemblies in choline chloride–fructose deep eutectic solvents. In the dehydration of fructose to 5-hydroxymethylfurfural (HMF), Ly3−xHxPW exhibited different catalytic activities because of their different acid–base properties. Among all the HPA catalysts, Ly2HPW gave the best results with 93.3% conversion and 92.3% HMF yield within a very short time, i.e. 1 min under the conventional temperature of 110 °C using choline chloride (ChCl) as solvent, and this was almost the best result by far. The highest activity and selectivity of Ly2HPW came from the synergistic effect between certain acidic and basic capacities, which provides ready accessibility to the nucleophilic (–NH2) and electrophilic (H) sites. Moreover, this catalyst was tolerant to highly concentrated feedstock (∼66.7 wt%) with the additive ChCl. Ly2HPW performed as a heterogeneous catalyst in the ChCl system and could be recycled by simple washing treatment.

Acid–base bifunctional HPA nanocatalysts promoting heterogeneous transesterification and esterification reactions

A new catalytic system including acid–base bifunctional heteropolyacids (HPAs) nanocatalyst is presented, for the simultaneous transesterification of oil and esterification of free fatty acids (FFAs), to directly convert low quality feedstocks to biodiesel in a one-pot process.

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.

Degradation of phenol by air and polyoxometalate nanofibers using a continuous mode

Nanofibers were synthesized by an electrospinning technique using a polymer as a support and polyoxometalates (POMs) as dopants. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, 31P MAS NMR, scanning electron microscopy (SEM), and a high resolution transmission electron microscope (TEM) were used to characterize the resulting hybrids. These POM nanofiber catalysts could provide a continuous flowing mode to promote the oxidative degradation of phenol into simpler inorganic species using air (O2) as an oxidant at room temperature through nine cycles. The leaching of POMs from the nanofibers was minor, showing that the catalyst had excellent stability and could be used as a heterogeneous structure.

Incorporation of Ce3+ ions into dodecatungstophosphoric acid for the production of biodiesel from waste cooking oil

A series of cerium-exchanged dodecatungstophosphates CexH3-3xPW12O40 (CexH3-3xPW, x = 0.4, 0.6, 0.7, 0.8, 0.9, and 1.0) were designed and characterized by Fourier transform infrared spectroscopy (FT-IR), pyridine adsorption IR spectra, X-ray diffraction (XRD), and temperature programmed desorption of ammonia (NH3-TPD). The activity of these catalysts was evaluated for the generation of biodiesel from waste cooking oil (WCO) with 27 wt% of free fatty acids (FFAs) and 1 wt% of water. Compared to theri parent H3PW12O40, CexH3-3xPW showed higher activity for esterification of FFAs and transesterification of triglyceride to mono-alkyl esters of fatty acids (FAMEs) in one-pot. The acidic properties of CexH3-3xPW depended on the amount of Ce3+ ions in the secondary structure of Keggin heteropolyacids, while conversion of triglycerides and FFAs depended on their increasing acid contents. Among CexH3-3xPW, Ce0.7H0.9PW showed significant activity due to its high Brønsted acidity and Lewis acidity with 98% conversion of WCO and almost 100% selectivity to FAME at the molar ratio of methanol to WCO = 21:1 and 65 °C for 12 h. The reaction adhered to first-order kinetics with the activation energy (Ea) of 71 kJ/mol and the frequency factor (A) of 1.8 × 108 min-1, while the reaction rates were not influenced by the internal mass transport. The catalyst behaved as a heterogeneous catalyst, which can achieve the regeneration and be used more than five runs but without obvious decrease in activity. The characteristics of the WCO methyl ester were found to be close to the engine requirement.