无溶剂及微乳液体系中脂肪酶催化红花油水解的动力学

 在无溶剂及二(2-乙基己基)丁二酸酯磺酸钠(AOT)/异辛烷/磷酸盐缓冲液微乳液体系中,研究了黑曲霉脂肪酶催化红花油水解反应的动力学. 结果表明,无溶剂及微乳液体系中反应的活化能分别为32.205和7.391 kJ/mol. 酶在无溶剂体系中的热稳定性高于微乳液中. 无溶剂及微乳液体系中的表观米氏常数分别为0.135和0.101 mol/L. 在两种体系中,乙醇对水解反应的抑制作用均为竞争性可逆抑制,且均在底物浓度大于0.819 mol/L时出现底物抑制现象. 结合胶团催化理论和酯键水解机理对两种体系中酶水解性能的差异进行了解释.     

Database Survey of Single-and-Half Phosphorus–Oxygen Bonds in Salts with the C2PO2 Segment: Crystal Structure of [NH2C5H4NH][(C6H5)2P(O)(O)]⋅2H2O

Crystallography Reports - For structures with a C2PO2 skeleton, a comparison of “single-and-half” phosphorus–oxygen bonds with single and double phosphorus–oxygen bonds is...     

Poly(styrene-co-p-(hexafluoro-2-hydroxy-2-propyl)-styrene) blends with syndiotactic and/or isotactic poly(methyl methacrylate)

A modified polystyrene, poly(styrene-co-p-(hexafluoro-2-hydroxy-2-propyl)styrene) (FPS), was blended with syndiotactic and/or isotactic poly(methyl methacrylate) (PMMA) in toluene. Blends were prepared under different conditions to control the self-aggregation of the PMMA segments. The formation of hydrogen bonding and the attendant changes in the aggregation or crystallization of PMMA segments were determined in the solid state by means of FTIR and DSC. The results indicate that for the binary blends, the aggregation of PMMA segments is diminished by hydrogen bonding interaction with either s-PMMA or i-PMMA, and that the interaction is stronger with the s-PMMA blends. For the ternary blends, FPS/s-PMMA/i-PMMA, the preference for stereocomplexation in the system with hydrogen bonding may be attributed to the “kink-nucleated” mechanism, which needs relatively short chain lengths of PMMA segments. Regardless of the order of addition of the components, the formation of crystalline stereocomplexes of s- and i-PMMA could be readily detected. Therefore, the miscibility of the polymer blends is dependent on the competition between the self-aggregation of the s- or i-PMMA segments, stereocomplexation and the hydrogen bonding interaction of PMMA segments with FPS.     

Cobalt‐Embedded Nitrogen‐Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values

Despite being technically possible, splitting water to generate hydrogen is still practically unfeasible due mainly to the lack of sustainable and efficient catalysts for the half reactions involved. Herein we report the synthesis of cobalt‐embedded nitrogen‐rich carbon nanotubes (NRCNTs) that 1) can efficiently electrocatalyze the hydrogen evolution reaction (HER) with activities close to that of Pt and 2) function well under acidic, neutral or basic media alike, allowing them to be coupled with the best available oxygen‐evolving catalysts—which also play crucial roles in the overall water‐splitting reaction. The materials are synthesized by a simple, easily scalable synthetic route involving thermal treatment of Co²⁺‐embedded graphitic carbon nitride derived from inexpensive starting materials (dicyandiamide and CoCl₂). The materials’ efficient catalytic activity is mainly attributed to their nitrogen dopants and concomitant structural defects.     

Conversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria–Zirconia Catalysts in a Single Reactor

The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value‐added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria–zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady‐state process at 723 K using O₂ as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO₂ as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox‐active CZ support, which also stabilizes the small NiO clusters.