Yachun Liu

Aerobic Oxidation of Ethylbenzene Co-catalyzed by N-Hydroxyphthalimide and Oxobis(8-Quinolinolato) Vanadium (IV) Complexes

The mediation effect of vanadium compounds on the N-hydroxyphthalimide (NHPI)-catalyzed aerobic oxidation of ethylbenzene (EB) was investigated at 90 °C in benzonitrile. Among the vanadium mediators examined, a series of oxobis(8-quinolinolato) vanadium (IV) complexes (VIVOQ2), which were prepared by the coordination of 8-hydroxyquinoline or its derivatives with oxobis(2,4-pentanedionate) vanadium (IV) (VIV O(acac)2) showed a better mediation effect than VIVO(acac)2, NH4VO3, and V2O5 and they gave about 60%–69% EB conversion and 97% of acetophenone (AcPO) selectivity under optimum reaction conditions. This is due to the dual catalysis effects of these V mediators on the transformation of NHPI to the phthalimide-N-oxyl (PINO) radical and the decomposition of 1-phenylethyl hydroperoxide to AcPO, as supported by UV-Vis spectral characterization.

Biochar sulfonic acid immobilized chlorozincate ionic liquid: an efficiently biomimetic and reusable catalyst for hydrolysis of cellulose and bamboo under microwave irradiation

A chlorozincate ionic liquid-functionalized biochar sulfonic acid (BC-SO3H-IL-Zn) was designed and conveniently prepared via multistep processes, involving the syntheses of biochar sulfonic acid (BC-SO3H) and 1-trimethoxysilylpropyl-3-methylimidazolium chloride (IL)-ZnCl2 (IL-Zn), followed by grafting the IL-Zn onto BC-SO3H. The proposed catalyst was found to show a much higher turnover number (TON, 5.91 for cellulose and 1.78 for bamboo) for the microwave-assisted hydrolysis of cellulose and bamboo to reducing sugars (RSs) in water compared to the corresponding IL-functionalized BC-SO3H (BC-SO3H-IL, TON, 3.23 for cellulose and 0.46 for bamboo) and BC-SO3H (TON, 1.51 for cellulose and 0.15 for bamboo). Furthermore, it, like BC-SO3H-IL, possessed an excellent repeatability for cellulose hydrolysis. The excellent catalytic performance of BC-SO3H-IL-Zn is likely due to the following reasons: Firstly, the introduction of ZnCl2 bestows the catalyst with a delignification function. Secondly, in comparison with the OH groups of BC-SO3H, the IL and especially IL-Zn groups flexibly bound to BC-SO3H, like cellulose binding domain of cellulose, show an stronger affinity for cellulose molecules, on the other hand, they play a better synergistic role and improved acidity in the SO3H groups (as a catalysis domain of cellulase) catalyzing cleavage of the β-1,4-glycosidic bonds of cellulose, as supported by the adsorption experiments of catalysts to oligosaccharides, their thermogravimetric analysis and catalytic reaction results.Graphical AbstractChlorozincate ionic liquid functionalized biochar sulfonic acid (BC-SO3H-IL-Zn) proposed by us was found to be an efficiently biomimetic catalyst for the heterogeneous hydrolysis of cellulose and lignocelluloses to RSs and 5-hydroxymethyl furfural (5-HMF) under microwave irradiation.

Mild, one-step hydrothermal synthesis of carbon-coated CdS nanoparticles with improved photocatalytic activity and stability

Abstract Carbon-coated CdS (CdS@C) nanoparticles were conveniently prepared by a one-step hydrothermal carbonization method at temperature as low as 130 °C, in which cadmium acetate and glucose were used as the cadmium and carbon sources, respectively, and thiourea was used as the sulfur source and catalyst for the hydrothermal carbonization of glucose. The prepared CdS@C particles possess a smaller size, better dispersion, and more uniform distribution than pure CdS particles prepared under the same conditions. Furthermore, the hydrothermal carbonization of glucose easily induces the prior formation of metastable cubic CdS crystals. In addition, the carbonaceous species coated on the surface of CdS expands the range of absorption light and slightly decreases the band gap of CdS, as well as reduces the recombination of the photogenerated electron-hole pairs of CdS and its photo-oxidative corrosion, which can improve the photocatalytic activity and stability of CdS for the photo-oxidative degradation of methyl orange in aqueous solution under visible light irradiation.

Vanadium-Substituted Tungstophosphoric Acids as Efficient Catalysts for Visible-Light-Driven Oxygenation of Cyclohexane by Dioxygen

This paper discloses that the oxygenation of cyclohexane by dioxygen (O2) to cyclohexanol and cyclohexanone over three vanadium‐substituted tungstophosphoric acids (PW11V1, PW10V2, PW9V3) can occur in MeCN under visible‐light irradiation, but provides very low cyclohexane conversion (0.8–2.4 %) with modest cyclohexanone selectivity (51–58.3 %). Importantly, an HCl aqueous solution was found to drastically promote this photooxygenation catalyzed by PW10V2 and especially PW9V3 acids, respectively providing approximately 20.4 and 23.4 % cyclohexane conversion and approximately 82.5 and 87.1 % cyclohexanone selectivity, with a concomitant formation of a small amount of chlorocyclohexane. However, such promoting effect was negligible in the PW11V1‐ photocatalyzed oxygenation and the other acids and the chlorine‐containing salts did not show any promotion effect on the present photocatalysis reaction. Notably, the HCl‐promoted photocatalytic oxygenation was significantly influenced by the amount of water. The cyclohexanone selectivity continuously and significantly increased with water amount, but photooxygenation efficiency drastically decreased if a slight excess amount of water was added. Based on these findings and the UV/Vis spectral and cyclic voltammetric measurements, a free‐radical mechanism initiated by the Cl atoms generated in the present photocatalysis system was proposed.