Preparing L‐α‐Glycerophosphocholine in a Phase‐Transfer Catalytic Reaction: Kinetic Study

The transesterification of phosphatidylcholine with methanol was successfully carried out using a promising solvent methyl tert‐butyl ether instead of traditional ether, and the reaction was dramatically enhanced in the presence of tetrabutylammonium hydroxide as the phase‐transfer catalyst. Kinetics of the reaction including the effects of the reaction conditions on the conversion of phosphatidylcholine and the apparent rate constant (k_app) were investigated in detail. On the basis of the experimental evidence, the transesterification mechanism was proposed and a kinetic model was developed, and the experimental data were well described by the pseudo–first‐order equation.     

氮气吹扫和费托合成的脉冲过程以提高α-烯烃的选择性

费托合成可以将煤炭或者生物质气化得到的合成气转化为α-烯烃等重要的化工产品。研究将费托合成和氮气吹扫操作组合成一脉冲过程,在稳定的操作状态下保证费托合成和氮气吹扫交替进行。在传统的费托合成条件下(反应气速为2 000 h^-1,温度为497 K, 压力为 2.0 MPa, 氢碳体积比为2.0)考察了Fe-Co催化剂在脉冲过程中费托合成的活性和选择性。结果表明,N₂吹扫温度和压力分别为517 K和0.2 MPa下的费托合成的C₃烯烷比是未脉冲的相同反应条件下的九倍左右。同时,反应过程中CH₄的选择性和CO的转化率有所下降。在此基础上,通过间歇反应在固定床反应器中进行该脉冲过程,实验结果表明,利用脉冲操作在费托反应中可以获得更高的烯烃选择性。     

A Terbium Metal–Organic Framework for Highly Selective and Sensitive Luminescence Sensing of Hg2+ Ions in Aqueous Solution

A series of isomorphic lanthanide metal–organic frameworks (MOFs) Ln(TATAB)?(DMF)₄(H₂O)(MeOH)_0.5 (LnTATAB, Ln=Eu, Tb, Sm, Dy, Gd; H₃TATAB=4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoic acid) have been solvothermally synthesized and structurally characterized. Among these MOFs, TbTATAB exhibits good water stability and a high fluorescence quantum yield. Because mercury ions (Hg²⁺) have a high affinity to nitrogen atoms, and the space between multiple nitrogen atoms from triazine and imino groups is suitable for interacting with Hg²⁺ ions, TbTATAB shows highly selective and sensitive detection of Hg²⁺ in aqueous solution with a detection limit of 4.4 nm . Furthermore, it was successfully applied to detect Hg²⁺ ions in natural water samples.     

NHC‐Pd complex‐catalyzed double carbonylation of aryl iodides with secondary amines to α‐keto amides

A series of palladium–NHC compounds were prepared and their catalytic activity in the double carbonylation of aryl iodides to synthesize α‐keto amides were examined. Palladium complexes bearing mixed NHC–phosphine exhibited high efficiency for the double carbonylation reaction. The effects of different solvents, base, temperature, carbon monoxide (CO), pressure, various amine and aryl iodides were investigated. Both electron‐rich and electron‐deficient aryl iodides afforded the corresponding substituted α‐keto amides in moderate to good yields. A possible mechanism was also proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

Higher integrability for nonlinear elliptic equations with variable growth and discontinuous coefficients

In this paper, based on the theory of variable exponent spaces, we study the higher integrability for a class of nonlinear elliptic equations with variable growth and discontinuous coefficients. Under suitable assumptions, we obtain a local gradient estimate in Orlicz space for weak solution.     

Growth and spectral properties of Yb:Ca0.28Ba0.72Nb2O6 disordered crystal

The growth, XRD patterns, spectral properties, and fluorescence decays of Yb:Ca_0.28Ba_0.72Nb₂O₆ (Yb:CBN) with doping concentration of 1 at.% and 5 at.% were studied. The peak absorption cross-section and the emission cross-section were calculated. Larger Stark splitting of Yb:CBN offers the prospect of the quasi-four level laser operation.     

Histidine‐modified organic‐silica hybrid monolithic column for mixed‐mode per aqueous and ion‐exchange capillary electrochromatography

A novel organic‐silica hybrid monolith was prepared through the binding of histidine onto the surface of monolithic matrix for mixed‐mode per aqueous and ion‐exchange capillary electrochromatography. The imidazolium and amino groups on the surface of the monolithic stationary phase were used to generate an anodic electro‐osmotic flow as well as to provide electrostatic interaction sites for the charged compounds at low pH. Typical per aqueous chromatographic behavior was observed in water‐rich mobile phases. Various polar and hydrophilic analytes were selected to evaluate the characteristics and chromatographic performance of the obtained monolith. Under per aqueous conditions, the mixed‐mode mechanism of hydrophobic and ion‐exchange interactions was observed and the resultant monolithic column proved to be very versatile for the efficient separations of these polar and hydrophilic compounds (including amides, nucleosides and nucleotide bases, benzoic acid derivatives, and amino acids) in highly aqueous mobile phases. The successful applications suggested that the histidine‐modified organic‐silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar and hydrophilic compounds.