Premodification of Pt/γAl2O3 with Cinchonidine for the Enantioselective Hydrogenation of Ethyl Pyruvate: Effect of Premodification Conditions on Reaction Rate and Enantioselection

The premodification of a 5 wt% Pt/-Al₂O₃ catalyst with cinchonidine (0.01 and 0.2 g g^-1 _catalyst) is described and discussed. Premodification is carried out by treating the catalyst with a solution of cinchonidine followed by solvent removal. Catalysts premodified in this way give the same ee and initial rate of reaction for the enantioselective hydrogenation of ethyl pyruvate as those using the standard in situ modification procedure. Investigations of different solvents for premodification and reaction (dichloromethane, ethanol) show that it is the solvent used for the reaction that controls the observed enantioselection. Premodified catalysts also display the initial transient behavior typically observed with in situ modified catalysts in which the ee increases with conversion in the early part of the reaction. Premodified catalysts show an enhanced rate of reaction when ethanol is used as the reaction solvent compared with in situ modified catalysts under the same conditions. Premodification using aerobic conditions gives the best results and premodified catalysts can be stored prior to use for up to a week without loss of catalytic performance.     

固体超强酸SO2-4/TiO2-SiO2催化合成马来酸二辛酯

用H2SO4浸渍钛硅复合氧化物，制得固体超强酸SO4^2-/TiO2-SiO2，考察了催化剂对马来酸酐与正辛醇的酯化反应的催化作用及其制备条件对催化剂活性的影响，并与硫酸，对甲苯磺酸的催化效果比较，结果表明，对于给定反应，当n(Ti):n(Si)为15：1，用浓度0．6mol/L的硫酸浸渍8h，在550℃下焙烧3h时制得的催化剂SO4^2-/TiO2-SiO2具有最高的催化活性，用以催化马来酸酐和正辛醇的酯化反应，可得无色透明的酯化产物，3h内酯化率达99．1％，较SO4^2-/TiO2催化剂的酯化率提高了约6％。     

氟丙防腐涂料的耐候性研究

运用冷拼法制备氟丙树脂并配制了氟丙防腐涂料,比较研究了其与氟碳树脂涂料、含羟基丙烯酸树脂涂料性能及耐老化性能。结果表明:氟丙涂料比氟碳涂料具有更高的光泽度,比丙烯酸涂料有更好的耐候性,树脂含氟量与涂料的光泽度和失光率之间存在线性对应关系,含氟量增加,光泽度和失光率均线性降低。     

PS/SCCO_2发泡体系挤出胀大和泡孔平均直径预测模型

运用正交试验和统计相结合的方法,研究了温度、压力、剪切速率、发泡剂含量对聚苯乙烯/超临界CO2发泡体系挤出胀大和泡孔的影响;综合胀大比和毛细管数的关系,提出了聚苯乙烯/超临界CO2发泡体系挤出胀大和泡孔平均直径预测模型。与实验结果相比,发泡体系挤出胀大的预测值与实验测量结果的误差在5%左右,泡孔平均直径的预测值与实验测量值的误差在10%左右。     

皮革涂料用丙烯酸酯核-壳乳液的研制

采用种子乳液聚合法，以交联型软性聚合物为核，交联型硬性高聚物为壳，合成了具有优异耐寒性及高温抗回粘性聚合物。讨论了乳化剂种类及应用、核／壳比等对聚合物性能的影响。     

Chemical and microstructural investigation of Pt/CeO2 catalysts reduced at temperatures ranging from 473 to 973 K

The combined application of chemical techniques and HREM shows that platinum deactivation in Pt/CeO₂ catalysts steadily increases with the reduction temperature (T_r: 473–1173 K). Though no suppression of the H₂ adsorption was observed, the TPD-H₂ traces indicate the occurrence of significant chemical changes with T_r. As revealed by HREM, the metal decoration starts at T_r: 973 K, a temperature well above those at which the chemical effects can be observed.     

电子束辐照和氢氧化铝对LLDPE/EVA共混物凝胶含量和力学性能的影响

研究了电子束辐照剂量和氢氧化铝(ATH)的含量对线性低密度聚乙烯(LLDPE)/乙烯-醋酸乙烯酯(EVA)共混物凝胶含量和力学性能的影响。辐照剂量是影响LLDPE/EVA/ATH阻燃体系凝胶含量的主要因素,而ATH对其凝胶含量的影响较小。随着ATH含量的增加,LLDPE/EVA共混物的拉伸强度逐步增加,断裂伸长率迅速下降。所有阻燃体系的拉伸强度均是随着辐照剂量的增加而逐步增大,但辐照剂量对这些阻燃体系的断裂伸长率的影响却比较复杂。     

以稀土固体超强酸Gd^3＋-SO4^2-／ZrO2催化合成三氯水杨酸正戊酯

以不同配比的Gd3 -SO42-/ZrO2稀土固体超强酸合成三氯水杨酸正戊酯为探针反应,筛选出制备稀土固体超强酸Gd3 -SO42-/ZrO2的最佳工艺条件为:20 g ZrOCl2.8H2O1、.0%(质量分数)Gd2(SO4)3和0.8 mol.L-1H2SO4混合液,搅拌60 min后浸泡3 h,600℃焙烧3 h。以GSZ-1合成三氯水杨酸正戊酯的最佳反应条件为:72.8 g(0.3 mol)3,5,6-三氯水杨酸、17.6 g(0.2 mol)正戊醇、40 mL二甲苯和1.5 g的催化剂,电热套加热(105~110℃)回流反应2 h,酯化率可达93%。     

Binder effect on cycling performance of silicon/carbon composite anodes for lithium ion batteries

The cycling performance of a silicon/carbon composite anode has been significantly enhanced by using acrylic adhesive and modified acrylic adhesive as binder to fabricate the electrodes for lithium ion batteries. The capacity retentions of Si/C composite electrodes bound by acrylic adhesive and modified acrylic adhesive are 79% and 90% after 50 cycles, respectively. These two binders are electrochemically stable in the organic electrolyte in the working window. They also show larger adhesion strength between the coating and the Cu current collector as well as smaller solvent absorption in the electrolyte solvent than polyvinylidene fluoride (PVDF). Furthermore, sodium carboxyl methyl cellulose (CMC) plays an important role on improving the properties of acrylic adhesive, which increases the adhesive strength of acrylic adhesive and improves the activation of the electrodes.     

Advanced Sn/C composite anodes for lithium ion batteries

Metallic tin was deposited in fine particulate form on the surface of carbonaceous mesophase spherules (CMS) and in the pores of porous carbon by the decomposition and reduction of tin(II) 2-ethylhexanoate at 450 °C. The Sn/C composite powders obtained were used as anode materials for lithium ion cells. Electrochemical cycling tests of coin cells show that the dispersion of tin into the carbonaceous materials enhances the reversible capacity of the electrodes. The capacity retention at the 50th cycle is 91 % for Sn/CMS composite containing 22% tin, against 428 mAh g^–1 at the first cycle. With further increase in tin content, the capacity fade upon cycling is more rapid.