Second nearest-neighbor modified embedded-atom method interatomic potentials for the Pd-M (M = Al,Co, Cu,Fe, Mo,Ni, Ti) binary systems

Palladium (Pd) has attracted attention as one of the major components of noble metal catalysts due to its excellent reactivity to a wide range of catalytic reactions. It is important to predict and control the atomic arrangement in catalysts because their properties are known to be affected by it. Therefore, to enable atomistic simulations for investigating the atomic scale structural evolution, we have developed interatomic potentials for Pd-M (M = Al, Co, Cu, Fe, Mo, Ni, Ti) binary systems based on the second nearest-neighbor modified embedded-atom method formalism. These potentials reproduce various fundamental properties of the alloys (the structural, elastic and thermodynamic properties of compound and solution phases, and order-disorder transition temperature) in reasonable agreements with experimental data, first-principles calculations and CALPHAD assessments. Herein, we propose that these potentials can be applied to the design of robust bimetallic catalysts by predicting the shape and atomic arrangement of Pd bimetallic nanoparticles.     

Heterogeneous Enantioselective Hydrogenation of Activated Ketones Catalyzed by Modified Pt‐Catalysts: A Systematic Structure‐Selectivity Study

A systematic structure‐selectivity study was carried out for the enantioselective hydrogenation of activated ketones with chirally modified Pt/Al₂O₃ catalysts. For this, 18 modifiers containing an extended aromatic system able to form a strong adsorption complex with the Pt surface, and a suitable chiral group with an amino function capable to interact with the keto group of the substrate ( HCd, Qd, HCn, Qn , and semi‐synthetic derivatives, as well as synthetic analogues) were prepared and tested on 8 different activated ketones in AcOH and toluene under standard conditions. It was found that relatively small structural changes of the substrate and/or modifier structures strongly affected the enantioselectivity, and that no “best” modifier exists for all substrates. The highest ees for all substrates were obtained with quinuclidine‐derived modifiers in combination with naphthalene or quinoline rings, either in AcOH (substrates 1 – 5 and 8 , all carrying an sp³ carbon next to the keto group) or toluene ( 6 and 7 , with an sp² carbon next to the ketone). The presence and nature of the substituent R' at the quinuclidine significantly affected the ee (positive and negative effects). Certain combinations of an aromatic system and an amino function were preferred: For the quinuclidine moiety, quinoline and to a somewhat lesser extent naphthalene were a better match, while for the pyrrolidinylmethyl group anthracene was better suited. Methylation of the OH group often had a positive effect for hydrogenations in AcOH but not in toluene. With the exception of 8 , higher ees were obtained for the Cd / Qn series [leading to (R)‐products] than for the Cn / Qd series [leading to (S)‐products]. In several cases, opposite structure‐selectivity trends were detected when comparing reactions in toluene and AcOH, indicating a significant influence of the solvent.     

磷酸酯改性淀粉的制备及在肉类中的应用

以糯玉米淀粉为原料,采用复合磷酸盐进行酯化,以取代度为指标,分别考察了pH、正磷酸盐添加量、磷酸盐配比、反应温度、反应时间对酯化的影响,并对其进行了优化,得到最佳工艺条件:糯玉米淀粉乳浓度40%,反应pH=5.5,正磷酸盐添加量37.5g,磷酸二氢钠与磷酸氢二钠的配比0.4,反应温度150℃,反应时间2h。将磷酸酯淀粉添加在火腿肠中时,其弹性、粘聚性、胶着性、咀嚼度等明显优于添加原淀粉的产品,其中取代度为0.1257,添加8%时最佳。     

蓖麻油基热稳定剂制备及其在聚氯乙烯制品中的作用行为研究

将蓖麻油酸与马来酸酐、六氢苯酐分别制备了2种蓖麻油基二元酸,并合成出相应的新型蓖麻油基钙/锌(Ca/Zn)盐。通过刚果红法、电导率法和热重分析等方法研究了蓖麻油基Ca/Zn盐与传统的石油基异辛酸Ca/Zn盐分别在聚氯乙烯制品中的热稳定性能。结果表明,改性蓖麻油基二元酸锌不易“锌烧”,锌离子含量为2 %时,静态热稳定时间分别为9.8、9.2 min,异辛酸钙/蓖麻油基二元酸锌盐之间协同效应较为显著,且热稳定效果随Ca/Zn离子含量比的变化而变化。     

超声作用下辛烯基琥珀酸淀粉酯合成工艺及反应机理研究

以木薯淀粉为原料,辛烯基琥珀酸酐为变性剂,采用湿法工艺,在超声作用下制备辛烯基琥珀酸淀粉酯.用单因素实验探索最佳制备工艺条件及酯化反应机理.结果表明,超声作用制备辛烯基琥珀酸淀粉酯的最佳工艺条件为：超声作用时间30 min,超声功率250 W,酯化pH 8.5,反应温度35℃,在最佳工艺条件下制备所得辛烯基琥珀酸淀粉酯取代度达0.0181,比未施加超声作用所制得的产品取代度提高了28.4％.超声波强化淀粉变性反应机理是超声波的空化效应对木薯淀粉的颗粒结构有一定影响,使淀粉颗粒表面变粗糙,增加了反应物之间的接触面积,强化了酯化反应的发生.     

Fluorometric detection of interaction between lipase and glyceride

Previously, we devised the efficient modification of lipase, which can be dissolved and still maintain its activity in organic solvents. In this work, the fluorescence of the modified lipase could be detected in chloroform. When glycerides were added to the modified lipase solution, the intrinsic tryptophan fluorescence of the modified lipase decreased, which suggests that the environment of the tryptophan residue was affected by the substrate. The interaction between the modified lipase and glyceride was studied kinetically in terms of fluorescence intensity of the tryptophan residue. Because glyceride is not subject to hydrolysis in nonaqueous solution, the dissociation constant of the enzyme-substrate complex could be determined. Thus, insight into the direct interaction between enzyme and substrate provided some structural information regarding the active site of lipase.     

Molecular thermodynamics of binary polymer solutions using modified double lattice model: Chain length dependence of primary lattice

In a previous study we modified a double lattice model by introducing a new interaction parameter, which improved the mathematical approximation defect, and gave a new expression for the Helmholtz energy of mixing. In the model the universal constants C_β and C_γ in the primary lattice were determined by comparing them with literature Monte Carlo simulation data, which is the only case for r₁ = 1 and r₂ = 100 (case I). In this study we introduce new universal constants, C_β and C_γ, as a function of the chain length of a polymer in a solvent (case II) by comparing them with other literature simulation data for various polymer chain lengths. The proposed model is compared with polymer–solvent systems. In an upper critical solution temperature phase behavior the theoretical results of case II were improved over those of case I. However, in a lower critical solution temperature phase behavior those of case I were not very sensitive to C_β and C_γ. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2627–2633, 1999     

Selective detection of dopamine using a functionalised polyaniline composite electrode

The behaviour of a poly (aniline boronic acid) (PABA) modified glassy carbon electrode (GCE) for the detection of dopamine (DA) in the presence of excess of ascorbic acid (AA) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques is investigated. On bare GCE, both DA and AA are oxidized at ~0.16 V, whereas on PABA modified GCE they are oxidized at 0.2 and 0.054 V, respectively. Though PABA favours DA oxidation through ester formation with boronic acid motif, the AA oxidation is also promoted by polyaniline backbone through the involvement of AA in the redox of polyaniline. Since both DA and AA undergo oxidation at closely spaced potentials at a PABA electrode, Nafion®-incorporation into the PABA film was examined for selective determination of DA in the presence of AA. The selectivity was due to accumulation of DA on the electrode surface through ester formation with the boronic acid group and suppression of AA oxidative current through charge discrimination by Nafion.     

改性钼镍粉在催化缩酮反应中的应用

用改性钼镍粉作催化剂。催化环己酮与乙二醇进行缩合反应。合成了环己酮乙二醇缩酮产物。通过实验选择出了改性钼镍粉催化缩铜反应的最佳条件:n(环己酮)∶n(乙二醇)=1∶2。环己烷作带水剂,其用量为15mL,催化剂用量为环己酮质量的7%,回流反应时间4h。环己酮乙二醇缩酮的总收率为90.5%。     

新型AGR管材的性能及应用前景

新型供水管材-AGR管(亚克力共聚PVC管)，采用超微粒子丙烯酸树脂弹性体与PVC接枝共聚而成，在保持原有PVC刚性性能基础上，提高了低温冲击性能及卫生性能，可用于供水管、抗震管及其他饮料和化工流体的输送。