脂肪酶在有机溶剂中催化酯合成和酯交换反应

报道了猪胰脂肪酶在冻干时的pH值、有机溶剂的极性、反应系统的含水量、温度以及底物碳链的长度和支链对酶在有机相中催化活性的影响规律。利用该酶合成了具有玫瑰香味的月桂酸香茅酯和辛酸香茅酯。     

Effects of metal ions and ligands on transesterification: synthesis,structures, and catalytic activities of a series of cation–anionic complexes with dipyridylamine ligands

A series of cation–anion complexes derived by 2,2′-dipyridylamine (Hdpa) and carboxylate ligands with formulas [Ni(Hdpa)₂(CH₃COO)]Cl(CH₃OH) (1), [Co(Hdpa)₂(CH₃COO)]Cl(CH₃OH) (2), [Ni(Hdpa)₂(CH₃CH₂CH₂COO)]Cl (3), [Co(Hdpa)₂(CH₃CH₂CH₂COO)]Cl (4), [Ni(Hdpa)₂(C₆H₅COO)]Cl (5), and [Co(Hdpa)₂(C₆H₅COO)]Cl (6), were synthesized and characterized by IR, elemental analysis, MS(ESI), TG analysis, UV-Vis, and fluorescence spectra. X-ray single crystal structural analysis showed that the coordination geometries of metal ions in these complexes are similar and they are cation–anion species. The hydrogen-bonding structures are 1-D chains through the N–H···Cl bonds. There are weak stacking interactions between pyridine rings in 1–4, while there are no stacking interactions in 5 and 6. We have investigated the transesterification of phenyl acetate with methanol catalyzed by 1–6 under mild conditions; 1–4 are homogeneous catalysts while 5 and 6 are heterogeneous catalysts due to their poor solubility in methanol. Cobalt complexes exhibit higher catalytic activities than corresponding nickel complexes. Complex 4 is the best catalyst of these six complexes.     

Studies of miscibility,transesterification and crystallization in blends of poly(ethylene terephthalate) and Poly(ethylene-2,6-naphthalene dicarboxylate)

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) were obtained by coprecipitation from solution followed by melt-pressing for different timest _mand quenching in iced water. When the melt-pressing time was 0.2 and 0.5 min, two glass transition temperaturesT _gwere observed by means of dynamic mechanical analysis (DMA), indicating that there are two phases present, a PEN-rich phase and a PET-rich phase. The differential scanning calorimetry (DSC) curves show two crystallization peaks and two melting peaks which, according to wide-angle x-ray scattering (WAXS) measurements, can be attributed to PET and PEN, respectively. In the case oft _m=2 min or longer, a single value ofT _gand thus a single phase is found to exist. Fort _m=10 min and 45 min no crystallization and melting at all is observed during heating with 10°C/min, indicating that a copolyester of PET and PEN has been formed by transesterfication during melt-pressing.Time-resolved WAXS measurements during isothermal crystallization show that, in the blend, the half-time of crystallization of PET is different from that of PEN, and not the same as that which is found in the pure polymer.Dedicated with best wishes to Prof. Dr. E.W. Fischer on the occasion of his 65th birthday     

煅烧温度对氧化硅负载磷钼酸铜催化剂结构及酯交换活性影响

以S iO2为载体用浸渍法制备了Cu3/2PMo12O40/S iO2催化剂,用于碳酸二甲酯和苯酚酯交换合成碳酸二苯酯,并用DTA-TG、IR和XRD等对催化剂进行了表征.煅烧温度低于400℃时,催化剂仍然保持了Keggin结构;高于450℃时,催化剂Keggin结构分解,分解产物为α-MoO3等.活性随煅烧温度升高而增加,在400℃达到最大值,甲基苯基碳酸酯和碳酸二苯酯总收率为25.0%,选择性99.2%;高于500℃催化剂活性降低,表明Keggin结构在催化剂活性中起到了重要作用.