生物质催化热解制取轻质芳烃

以轻质芳烃苯、甲苯、二甲苯和萘(BTXN)为目的产物,采用双颗粒流化床反应器对3种木材生物质进行了热解实验. 结果表明,木材生物质的初次热解终止温度低,有利于低温催化转化. 生物质中92%的挥发分在673 K时已释放完全,且生物质在初期热解得到的焦油经过二次分解反应可以转化为其它产物,通过有效控制生物质热解二次气相反应,能够改变其产物的分布,从而获得不同的目的产物. 生物质的催化加氢热解实验结果表明,催化剂种类和热解温度对加氢热解产物收率及其分布均有影响, BTXN是热解或加氢热解过程中二次气相反应的中间产物. 为了获得高产率的BTXN, 必须选择加氢活性适度的催化剂. 当CoMo-S/Al2O3催化剂作为流化介质进行加氢热解时,在863 K时, BTXN的收率可达6 3%(干燥无灰质量基准), 而NiMo/Al2O3催化剂表现出了很强的加氢活性, CH4的收率高达99 5%.     

水热条件下酸催化氧化木质纤维生物质制取乙酸

木质纤维基生物质是一类新的能够生产液体燃料和化学品的可再生资源. 本文研究了木质纤维生物质在水热条件下, 以少量无机酸作为酸催化剂, 氧气作为氧化剂(2.0 MPa), 经过"一锅两步法"转化成乙酸的反应. 以玉米秸秆作为反应原料时, 最高可以获得21.3 wt%的乙酸, 占据整个液体产物质量比例的84.6% (选择性). 同时, 将反应推广到玉米芯, 甘蔗渣, 竹子, 杨木和松木等多种生物质原料的转化, 同样取得了较高的乙酸产率. 最后, 我们对木质纤维生物质转化到乙酸的反应过程进行了研究. 研究表明木质纤维生物质中的碳水化合物六碳糖是乙酸的主要来源, 六碳糖经过脱水和水解生成乙酰丙酸中间体, 乙酰丙酸在氧化条件下断裂C-C键生成乙酸.     

Catalytic Biorefining of Plant Biomass to Non‐Pyrolytic Lignin Bio‐Oil and Carbohydrates through Hydrogen Transfer Reactions

Through catalytic hydrogen transfer reactions, a new biorefining method results in the isolation of depolymerized lignin—a non‐pyrolytic lignin bio‐oil—in addition to pulps that are amenable to enzymatic hydrolysis. Compared with organosolv lignin, the lignin bio‐oil is highly susceptible to further hydrodeoxygenation under low‐severity conditions and therefore establishes a unique platform for lignin valorization by heterogeneous catalysis. Overall, the potential of a catalytic biorefining method designed from the perspective of lignin utilization is reported.     

Synthesis of 2‐Arylbenzoxazoles from Flash Vacuum Pyrolysis of 2‐Methoxy‐N‐(arenylidene)anilines

Flash vacuum pyrolysis of 2‐methoxy‐N‐(arenylidene)anilines 2a‐g at 700 °C and 1 × 10^‐2 Torr gave the corresponding 2‐arylbenzoxazoles 1a‐g .     

Enhanced Catalytic Activity and Unexpected Products from the Oxidation of Cyclohexene by Organic Nanoparticles of 5,10,15,20‐Tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinatoiron(III) in Water by Using O2

The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20‐tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinato iron(III), ([Fe^III(tppf₂₀)]) and H₂O₂ is typical of the latter: the epoxide is 99 % of the product and turnover numbers are about 350. 1 – 4 Herein, we report that dynamic organic nanoparticles (ONPs) of [Fe^III(tppf₂₀)] with a diameter of 10 nm, formed by host–guest solvent methods, catalytically oxidize cyclohexene with O₂ to yield only 2‐cyclohexene‐1‐one and 2‐cyclohexene‐1‐ol with approximately 10‐fold greater turnover numbers compared to the non‐aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89 % water and O₂ is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports.     

Inhibitor‐Induced Dimerization of an Essential Oxidoreductase from African Trypanosomes

Trypanosomal and leishmanial infections claim tens of thousands of lives each year. The metabolism of these unicellular eukaryotic parasites differs from the human host and their enzymes thus constitute promising drug targets. Tryparedoxin (Tpx) from Trypanosoma brucei is the essential oxidoreductase in the parasite's hydroperoxide‐clearance cascade. In vitro and in vivo functional assays show that a small, selective inhibitor efficiently inhibits Tpx. With X‐ray crystallography, SAXS, analytical SEC, SEC‐MALS, MD simulations, ITC, and NMR spectroscopy, we show how covalent binding of this monofunctional inhibitor leads to Tpx dimerization. Intra‐ and intermolecular inhibitor–inhibitor, protein–protein, and inhibitor–protein interactions stabilize the dimer. The behavior of this efficient antitrypanosomal molecule thus constitutes an exquisite example of chemically induced dimerization with a small, monovalent ligand that can be exploited for future drug design.     

A New and Sensitive Catalytic Resonance Scattering Spectral Assay for the Detection of Laccase Activity Using H2O2‐I−‐TDMAC System

In pH 3.8 acetic acid‐sodium acetate (HAC‐NaAC) buffer solution, laccase exhibited a strong catalytic effect on the H₂O₂ oxidation of I ^? to form I₂, and I₂ combined with excess I ^? to form I₃^? that reacted with cationic surfactants of tetradecyl dimethylbenzyl ammonium chloride (TDMAC) to produce the (TDMAC‐I₃)_n association complex particles, which exhibited a strong resonance scattering (RS) peak at 468 nm. Under the chosen conditions, as the concentration of laccase activity increased, the RS intensity at 468 nm (I_{468 nm}) increased linearly. The increased RS intensity ΔI_{468 nm} was linear to laccase activity in the range of 0.08–0.96 U/mL, with a regression equation of ΔI_{468 nm}?88.8U?1.9, and a detection limit of 0.02 U/mL laccase. This proposed method was applied to detect laccase activity in waste water, with satisfactory results.     

Green and Efficient Processing of Cinnamomum cassia Bark by Using Ionic Liquids: Extraction of Essential Oil and Construction of UV‐Resistant Composite Films from Residual Biomass

There is significant interest in the development of a sustainable and integrated process for the extraction of essential oils and separation of biopolymers by using novel and efficient solvent systems. Herein, cassia essential oil enriched in coumarin is extracted from Cinnamomum cassia bark by using a protic ionic liquid (IL), ethylammonium nitrate (EAN), through dissolution and the creation of a biphasic system with the help of diethyl ether. The process has been perfected, in terms of higher biomass dissolution ability and essential oil yield through the addition of aprotic ILs (based on the 1‐butyl‐3‐methylimidazolium (C₄mim) cation and chloride or acetate anions) to EAN. After extraction of oil, cellulose‐rich material and free lignin were regenerated from biomass–IL solutions by using a 1:1 mixture of acetone–water. The purity of the extracted essential oil and biopolymers were ascertained by means of FTIR spectroscopy, NMR spectroscopy, and GC‐MS techniques. Because lignin contains UV‐blocking chromophores, the oil‐free residual lignocellulosic material has been directly utilized to construct UV‐light‐resistant composite materials in conjunction with the biopolymer chitosan. Composite material thus obtained was processed to form biodegradable films, which were characterized for mechanical and optical properties. The films showed excellent UV‐light resistance and mechanical properties, thereby making it a material suitable for packaging and light‐sensitive applications.     

Synthesis and characterization of binary and ternary oxovanadium complexes of N,N′‐(2‐pyridyl)thiourea and curcumin: Catalytic oxidation potential,antibacterial, antimicrobial,antioxidant and DNA interaction studies

Two binary and two ternary mono‐oxovanadium (IV) complexes of acetylacetonate, curcumin and N ,N ′‐bis(2‐pyridyl)thiourea were synthesized. They were characterized using elemental analysis, infrared and UV–visible spectroscopies and magnetic and conductivity measurements. The formation constants K _f were determined from spectrophotometric measurements. The catalytic potential of the VO complexes was investigated for the oxidation of 1‐octene by aqueous H₂O₂ in acetonitrile. They display high catalytic potential for the conversion of 1‐octene with low chemoselectivity to the epoxy product. The VO complexes exhibit good antibacterial and antimicrobial activities. The antioxidant activity of the VO complexes and their ligands was investigated. The VO complexes show high DNA affinity and DNA cleavage ability.     

ChemInform Abstract: The Significance of Ionic Bonding in Sulfur Dioxide: Bond Orders from X‐Ray Diffraction Data.

Information on the S—O bond‐order in crystalline SO₂ is derived from wavefunction refinement of high‐resolution low‐temperature XRD data.     

Direct synthesis of linear low‐density polyethylene of ethylene/1‐hexene from ethylene with a tandem catalytic system in a single reactor

Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η⁵‐C₅H₄CMe₂C₆H₅)TiCl₃ ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η⁵‐C₅Me₄)SiMe₂(^tBuN)]TiCl₂ ( 2 )/MMAO or rac‐Me₂Si(2‐MeBenz[e]Ind)₂ZrCl₂ ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004     

Reactivity and Catalytic Activity of Homobimetallic Vanadium(V) Complex Derived from Bis(5‐chlorosalicylaldehyde)oxaloyldihydrazone Ligand

Homobimetallic vanadium(V) complex of the composition [(CH₃)₂NH₂⁺]₂[(VO₂)₂(sloxCl)].4H₂O was synthesized from the reaction of V₂O₅ with bis(5‐chlorosalicylaldehyde)oxaloyldihydrazone ligand in a 1:1 molar ratio in methanol. The structure of the complex was established by X‐ray crystallography. Reactivity of the complex with H₂O₂ leads to bis (monooxidoperoxidovanadate(V)) [{VO(O₂)}₂(sloxCl)]^2? formation and with HCl, oxidohydroxido complex of composition [(VO (OH)(sloxCl)]^2? was formed. Binding interaction of the complex was also investigated toward protein (BSA) and it was found to be 2.21 x 10⁸ M^?1. The catalytic activity of the complex in the oxidation of alcohols and oxidative bromination of some organic substrates was also studied, and it showed a great potent as a catalyst.     

Preparation of poly(ether ketone)s derived from 2,5‐furandicarboxylic acid via nucleophilic aromatic substitution polymerization

From the viewpoint of the suppression of the petroleum consumption, aromatic poly(ether ketone)s (PEKs) were prepared by the nucleophilic aromatic substitution polymerization of 2,5‐bis(4‐fluorobenzoyl)furan (BFBF) synthesized from biomass and aromatic bisphenols. The model reaction of BFBF and p‐methoxyphenol revealed that BFBF possessed enough reactivity for the nucleophilic aromatic substitution reactions. The polymerizations of BFBF and aromatic bisphenols afforded high molecular weight polymers with good yields in N‐methylpyrrolidone and diphenyl sulfone for several hours. The longer polymerization time brought about the formation of insoluble parts in any solvents and reduction of molecular weight. The obtained PEKs were thermoplastics and exhibited good thermal stability, mechanical properties, and chemical resistance comparable to common high‐performance polymers. The thermal properties were tunable with the structure of bisphenols. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3094–3101     

Independence of the brittle–ductile transition from the rubber particle size for impact‐modified poly(vinyl chloride)

A series of acrylic impact modifiers (AIMs) with different particle sizes ranging from 55.2 to 927.0 nm were synthesized by seeded emulsion polymerization, and the effect of the particle size on the brittle–ductile transition of impact‐modified poly(vinyl chloride) (PVC) was investigated. For each AIM, a series of PVC/AIM blends with compositions of 6, 8, 10, 12, and 15 phr AIM in 100 phr PVC were prepared, and the Izod impact strengths of these blends were tested at 23 °C. For AIMs with particle sizes of 55.2, 59.8, 125.2, 243.2, and 341.1 nm, the blends fractured in the brittle mode when the concentration of AIM was lower than 10 phr, whereas the blends showed ductile fracture when the AIM concentration reached 10 phr. It was concluded that the brittle–ductile transition of the PVC/AIM blends was independent of the particle size in the range of 55.2–341.1 nm. When the particle size was greater than 341.1 nm, however, the brittle–ductile transition shifted to a higher AIM concentration with an increase in the particle size. Furthermore, the critical interparticle distance was found not to be the criterion of the brittle–ductile transition for the PVC/AIM blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 696–702, 2006     

Insights into the Catalytic Activity of Nitridated Fibrous Silica (KCC‐1) Nanocatalysts from 15N and 29Si NMR Spectroscopy Enhanced by Dynamic Nuclear Polarization

Fibrous nanosilica (KCC‐1) oxynitrides are promising solid‐base catalysts. Paradoxically, when their nitrogen content increases, their catalytic activity decreases. This counterintuitive observation is explained here for the first time using ¹⁵N‐solid‐state NMR spectroscopy enhanced by dynamic nuclear polarization.