Authors:Shi Xu, Sheng Li, Yun Wei, Li Zhang, and Fei Xu
Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.
A facile and reusable catalytic system for alcohol oxidation with hydrogen peroxide was designed based on a temperature-responsive catalyst. Several kinds of alcohols were efficiently oxidized in high yields under relatively mild conditions. The catalyst could be easily recovered and reused.
A novel temperature-controlled phase transfer catalytic system based on [(C18H37)2(CH3)2N]7[PW11O39] for olefin epoxidation was demonstrated. The reaction was conducted in a non-chlorinated solvent of ethyl acetate with hydrogen peroxide. The catalyst was easily recovered and reused even ten cycles without loss in activity and selectivity.
Authors:Zuguang Liu, Taishun Zhang, Wei Zeng, Hualong Zhu, and Xinnan An
Cationic polymerization of α-pinene with silicotungstic acid (SiW12) as a catalyst was investigated. The structure of polymers and the catalysts were characterized by FT-IR, 1H-NMR and GPC. The experiments show that SiW12 is more active than both phosphotungstic acid and phosphomolybdic acid. The protons dissociating from the catalysts are the reactive species. SiW12 is found to be both the polymerization initiator and the counter-anion of the growing cationic center. The polymerization conditions are optimized by the single factor method as follows: monomer concentration is 50% (v/v), the dosage of catalysts is 7 wt% referred to α-pinene, reaction temperature is 50 °C, reaction time is 1 h. Under these conditions, the overall conversion of α-pinene is up to 90.87%, the polymer yield is 62.46% and its average number molecular weight is about 600. GC–MS analysis shows that there are six isomers of α-pinene after the reaction, but their content is very low. Most of α-pinene are changed to poly(α-pinene).
A series of CuO–V2O5/Al2O3 catalysts were prepared and characterized by various techniques such as XRF, BET, XPS and XRD. These catalysts were used for liquid-phase amination of toluene to toluidines. It was found that adding copper species to V2O5/Al2O3 catalyst showed a peculiar behavior, maintaining a high activity toward toluene amination. An optimum CuO content appeared at 1.6 wt% with a CuO/V2O5 molar ratio of 0.25. More than 60% total yield of toluidines was obtained over 1.6%CuO–15%V2O5/Al2O3 catalyst under optimized conditions. Catalyst characterizations revealed that the addition of copper improved the formation of V5+ species, thus enhancing the activity of the catalyst.
Peroxynitrite is a potent oxidant in vivo which can result in serious diseases such as cardiopathy, acute inflammation and
even cancer. Iron porphyrins have been shown to catalyze the efficient decomposition of peroxynitrite and are therefore important
to detoxify the cytotoxic oxidant as therapeutic agents. A kinetic and theoretical study on peroxynitrite decomposition catalyzed
by iron porphyrins is carried on in order to search and synthesize more effective scavengers of peroxynitrite. Kinetic experiments
and quantum chemistry calculations were applied to iron porphyrins with different substituents for catalyzing peroxynitrite
decay. Kinetic experiments suggested that the catalytic ability of iron porphyrins for peroxynitrite decomposition were dependent
on the type and location of substituents on the porphyrin rings. Density functional calculations further reveal that the variation
of substituent leads to a difference in structure-related quantum chemical descriptors including charges of central metal
ion, energy of the highest occupied molecular orbital and energy of the lowest unoccupied molecular orbital.
Authors:Hualong Zhu, Zuguang Liu, Taishun Zhang, Wei Zeng, Xinnan An, and Fuhou Lei
New and efficient Keggin heteropolyacid (HPA) catalysts were explored for β-pinene (PI) cationic polymerization. Among them,
12-phosphotungstic acid (PW12) dehydrated at 200 °C exhibited high catalytic activity. The overall PI conversion was up to 96.53%, and the obtained polymer
product yield was 60.85%. In order to study this new catalyzed reaction, special techniques of FT-IR, 1H-NMR, XRD, and XPS were used in this paper, and it was shown that the crystal structure of the heteropoly anion was not destroyed
during the reaction. The protons dissociating from the catalyst played an important role in the polymerization and the HPAs
had two important functions: polymerization initiator, and the counter-anion of the growing cation center.
The catalytic properties of a novel MFI-type zeolite with different SiO2/Al2O3 ratio in the dehydration of glucose to levulinic acid (LA) were investigated in this work. The results demonstrate the strength
of acidic sites and the mesoporosity of the zeolites have significant effects on LA formation.
Asymmetric electro-epoxidation of olefins had been achieved with sodium hypochlorite (NaClO) as an oxidant, which was generated by electrolysis in two-phase systems of aqueous sodium chloride (NaCl) and ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4)). The electrolysis conditions by different current densities (0.8, 0.9, 1.0, 1.1 and 1.3 mA/cm2) and pH values (8, 9, 10, 11, 12 and 13) were optimized and 1.1 mA/cm2 and pH 11 were selected. The proposed reaction mechanism is also discussed. The performance of new catalytic systems in four kinds of reaction media in the presence or absence of ammonium acetate (NH4OAc) as a cocatalyst was investigated systematically. Compared to the chemical epoxidation systems, the enantiomeric excess (ee) values and yields for the epoxidation of styrene, α-methylstyrene and indene were acceptable in the electrocatalytic epoxidation systems.