A study on the heterobinuclear site of Co(salen)/TiO2?SiO2 catalysts in the oxidative carbonylation of aniline

Titania‐silica immobilized Co(salen) complexes containing the heterobinuclear site were prepared by the sol–gel method for the catalytic synthesis of methyl N‐phenylcarbamate (MPC) by the oxidative carbonylation of aniline. It was found that the Ti:Si mole ratio had an important effect on the catalytic performance of Co(salen) complexes. When the Ti:Si ratio was 0.1, titania‐silica supported Co(salophen) showed the best catalytic activity. Under the reaction conditions, Co(salophen)/TS‐0.1, 0.5 g, aniline 11 mmol, methanol 25 ml, KI 2.2 mmol, CO:O₂ 9:1, total pressure 6 MPa, 150 °C, 3 h, the conversion of aniline and the selectivity of MPC were 60.7 and 88.1%, respectively. The XRD studies showed that titania was highly dispersed in the silica matrix. Co(salophen)/TS‐0.1 was reused five times with no significant loss of the activity, and no Co leaching was observed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd.     

Protective Effects of Gintonin on Reactive Oxygen Species-Induced HT22 Cell Damages: Involvement of LPA1 Receptor-BDNF-AKT Signaling Pathway

Gintonin is a kind of ginseng-derived glycolipoprotein that acts as an exogenous LPA receptor ligand. Gintonin has in vitro and in vivo neuroprotective effects; however, little is known about the cellular mechanisms underlying the neuroprotection. In the present study, we aimed to clarify how gintonin attenuates iodoacetic acid (IAA)-induced oxidative stress. The mouse hippocampal cell line HT22 was used. Gintonin treatment significantly attenuated IAA-induced reactive oxygen species (ROS) overproduction, ATP depletion, and cell death. However, treatment with Ki16425, an LPA1/3 receptor antagonist, suppressed the neuroprotective effects of gintonin. Gintonin elicited [Ca²⁺]_i transients in HT22 cells. Gintonin-mediated [Ca²⁺]_i transients through the LPA1 receptor-PLC-IP₃ signaling pathway were coupled to increase both the expression and release of BDNF. The released BDNF activated the TrkB receptor. Induction of TrkB phosphorylation was further linked to Akt activation. Phosphorylated Akt reduced IAA-induced oxidative stress and increased cell survival. Our results indicate that gintonin attenuated IAA-induced oxidative stress in neuronal cells by activating the LPA1 receptor-BDNF-TrkB-Akt signaling pathway. One of the gintonin-mediated neuroprotective effects may be achieved via anti-oxidative stress in nervous systems.     

A Study of Oxidative Degradation of Plastics by GC and GC-MS

Abstract

The behaviour of plastics, namely, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide and some copolymers, was studied in a combustion chamber in which the conditions of large-scale fires were simulated. Volatile combustion products were frozen-out or analyzed directly on two columns, one packed with Porapak Q and the other capillary column coated with squalane or CP Sil 5 CB. Carbonyl compounds were determined as the 2,4-dinitro-phenyl hydrazones on an OV-101 stationary phase. Thermal conductivity and flame ionization detectors were used. The decomposition products were identified either on the basis of retention data (retention indices) or by combined capillary GC-MS. The data obtained are used for the cataloguing of plastics from the point of view of their product toxicity during fires.     

介孔硅胶在柴油氧化-吸附组合脱硫中的应用研究

以硅胶(SG)为吸附剂,采用自制的双亲催化剂与H₂O₂组成的催化氧化体系将柴油进行氧化,利用固定床动态吸附法考察了硅胶性质、氧化过程及吸附条件等对硅胶吸附脱硫性能的影响,并对硅胶进行了表征。小角XRD和氮气吸脱附结果表明,实验所用硅胶具有介孔结构。吸附脱硫实验结果表明,在油剂比(柴油与吸附剂的体积比)相同时,氧化-吸附脱硫过程脱硫率明显高于吸附脱硫过程脱硫率;选用硅胶作吸附剂,吸附温度为40℃,吸附空速为6.0 h^-1时脱硫效果较好,当油剂比为1时,脱硫率高达94.57%,且该介孔硅胶具有较大的吸附硫容,随油剂比增大下降缓慢,当油剂比增大到15时,脱硫率仍达85.89%。     

Study of oxidative desulphurization process of coal with different metamorphism degrees

The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic matter.The medium-metamorphized coal,capable of turning into a plastic state and cake in the range of investigated temperatures(350～450 ℃),is desulphurized with the greatest difficulty.The chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.     

Photochemically promoted regiospecific P–C bond cleavage in the diruthenium compound Ru2(CO)2(bmf): X-ray diffraction structure of Ru2(CO)6[μ-C=C(PPh2)C(O)OCH(OMe)](μ-PPh2)

The ruthenium cluster Ru₃(CO)₁₂ reacts with the diphosphine ligand 3,4-bis(diphenylphosphino)-5-methoxy-2(5H)-furanone (bmf) in refluxing toluene to furnish the donor–acceptor compound Ru₂(CO)₂(bmf) as a 1?:?1 mixture of diastereomers. Photolysis of Ru₂(CO)₂(bmf) using 366?nm light leads to the oxidative cleavage of a P–C bond and formation of the phosphido-bridged complex Ru₂(CO)₆[μ-C=C(PPh₂)C(O)OCH(OMe)](μ-PPh₂). The regioselective Ph₂P–C(furanone ring) bond activation attendant upon optical excitation is traced to the phosphine group that was β to the furanone carbonyl group, as established by X-ray analysis of one of the diastereomers of Ru₂(CO)₆[μ-C=C(PPh₂)C(O)OCH(OMe)](μ-PPh₂). Both diruthenium products have been fully characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies and elemental analyses. The observed regioselectivity associated with the P–C bond activation in Ru₂(CO)₂(bmf) is discussed with respect to the chemistry of other bmf-substituted compounds prepared by our groups.     

Direct Oxidative Coupling of Arenes with Olefins by Rh‐Catalyzed C?H Activation in Air: Observation of a Strong Cooperation of the Acid

A [{RhCl(cod)}₂]/CCl₃COOH system was developed for the oxidative coupling of non‐chelate‐assisted arenes with olefins in the presence of catalytic amounts of Cu(OAc)₂ ? H₂O as a co‐oxidant and oxygen as the terminal oxidant. The acid was an indispensable component in this system and played a very important role in the coupling reaction. This catalytic system was applied to the direct oxidative coupling of a series of arenes and olefins and the corresponding products were afforded in high yields with special chemo‐ and regioselectivity. This reaction provides an atom‐efficient route to vinylarenes, which are widely used in various fine chemicals.     

Highly Efficient Extraction and Oxidative Desulfurization System Using Na7H2LaW10O36⋅32 H2O in [bmim]BF4 at Room Temperature

Highly efficient, deep desulfurization of model oil containing dibenzothiophene (DBT), benzothiophene (BT), or 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) has been achieved under mild conditions by using an extraction and catalytic oxidative desulfurization system (ECODS) in which a lanthanide‐containing polyoxometalate Na₇H₂LnW₁₀O₃₆ ? 32 H₂O (LnW₁₀; Ln=Eu, La) acts as catalyst, [bmim]BF₄ (bmim=1‐butyl‐3‐methylimidazolium) as extractant, and H₂O₂ as oxidant. Sulfur removal follows the order DBT>4,6‐DMDBT>BT at 30 ° C. DBT can be completely oxidized to the corresponding sulfone in 25 min under mild conditions, and the LaW₁₀/[bmim]BF₄ system could be recycled for ten times with only slight decrease in activity. Thus, LaW₁₀ in [bmim]BF₄ is one of the most efficient systems for desulfurization using ionic liquids as extractant reported so far.     

Synthetic Studies toward C‐Glucosidic Ellagitannins: A Biomimetic Total Synthesis of 5‐O‐Desgalloylepipunicacortein A

C‐glucosidic ellagitannins constitute a subclass of bioactive polyphenolic natural products with strong antioxidant properties, as well as promising antitumoral and antiviral activities that are related to their capacity to interact with both functional and structural proteins. To date, most synthetic efforts toward ellagitannins have concerned glucopyranosic species. The development of a synthetic strategy to access C‐glucosidic ellagitannins, whose characteristic structural feature includes an atropoisomeric hexahydroxydiphenoyl (HHDP) or a nonahydroxyterphenoyl (NHTP) unit that is linked to an open‐chain glucose core by a C‐aryl glucosidic bond, is described herein. The total synthesis of the biarylic HHDP‐containing 5‐O‐desgalloylepipunicacortein A ( 1 β ) was achieved by either using the natural ellagic acid bis‐lactone as a precursor of the requested HHDP unit or by implementing an atroposelective intramolecular oxidative biarylic coupling to forge this HHDP unit. Both routes converged in the penultimate step of this synthesis to enable a biomimetic formation of the key C‐aryl glucosidic bond in the title compound.     

Desulfurization kinetics of ZnO sorbent loaded on semi-coke support for hot coal gas

Zn-based sorbent (Z20SC) prepared through semi-coke support in 20 wt% zinc nitrate solution by high-pressure impregnation presents an excellent desulfurization capacity in hot coal gas,in which H2 S can not be nearly detected in the outlet gas before 20 h breakthrough time.The effects of the main operational conditions and the particle size of Z20SC sorbent on its desulfurization performances sorbent were investigated in a fixed-bed reactor and the desulfurization kinetics of Z20SC sorbent removing H2 S from hot coal gas was calculated based on experimental data.Results showed that the conversion of Z20SC sorbent desulfurization reaction increased with the decrease of the particle size of the sorbent and the increases of gas volumetric flow rate,reaction temperature and H 2 S content in inlet gas.Z20SC sorbent obtained from hydrothermal synthesis by high-pressure impregnation possessed much larger surface area and pore volume than semi-coke support,and they were significantly reduced after the desulfurization reaction.The equivalent grain model was reasonably used to analyze experimental data,in which k s=4.382×10-3 exp(-8.270×103/RgT) and Dep=1.262×10-4exp(1.522×104/RgT).It suggests that the desulfurization reaction of the Z20SC sorbent is mainly controlled by the chemical reaction in the initial stage and later by the diffusion through the reacted sorbent layer.