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981.
982.
983.
采用超声辐照柠檬酸络合法制备了复合氧化物SrFeO3,以苯酚为光催化探针分子,以450W高压汞灯为光源(主波长〉410nm),研究了SrFeO3光催化性能、研究表明,经过超声辐照制备的SrFeO3光催化活性提高一倍以上。XRD、TEM、DRS表征结果表明,超声辐照制备的SrFeO3粒径均匀、分散性好、粒径较小,光吸收红移显著。探讨了超声提高催化性能的机理。 相似文献
984.
Xiaobao Li Richard P. K. Wells Peter B. Wells Graham J. Hutchings 《Catalysis Letters》2003,89(3-4):163-167
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. 相似文献
985.
Short fibers and fine particles of β-SiC were obtained by pyrolysis of Colombian rice husk (RH). The synthesis of SiC was carried out in a gas furnace: a mathematical model was developed in order to design and build this equipment and the process was optimized using an experimental design that included variables such as temperature, pyrolysis time, type of catalyst, and process atmosphere. The obtained material was characterized by using FTIR, DRX and SEM for microstructural characterization and EDS technique for chemical analysis. 相似文献
986.
以水杨酸和间苯二酚为原料,无水氯化锌为催化剂,氯苯为溶剂,通过Friedel-Crafts反应合成了紫外线吸收剂2,2’,4-三羟基二苯甲酮。考察了反应温度、时间、原料配比对产品收率的影响。结果表明:在n(间苯二酚)∶n(水杨酸)=1∶1.2、反应温度120℃、反应时间3h的条件下,收率90%;产物经红外光谱、紫外光谱进行了表征,证明为二苯甲酮类物质,可用做紫外线吸收剂。 相似文献
987.
A series of poly(?‐caprolactone)‐b‐poly(ethylene glycol) (PCL‐b‐PEG) block copolymers with different molecular weights were synthesized with a salicylaldimine‐aluminum complex in the presence of monomethoxy poly(ethylene glycol). The block copolymers were characterized by 1H NMR, GPC, WAXD, and DSC. The 1H NMR and GPC results verify the block structure and narrow molecular weight distribution of the block copolymers. WAXD and DSC results show that crystallization behavior of the block copolymers varies with the composition. When the PCL block is extremely short, only the PEG block is crystallizable. With further increase in the length of the PCL block, both blocks can crystallize. The PCL crystallizes prior to the PEG block and has a stronger suppression effect on crystallization of the PEG block, while the PEG block only exerts a relatively weak adverse effect on crystallization of the PCL block. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
988.
氮化硅结合碳化硅管状制品的研制 总被引:1,自引:0,他引:1
简介了氮化硅结合碳化硅管状制品研制的必要性 ,确定了原材料及粒度配比 ,选择了合适的成型方法及添加剂 ,介绍了氮化烧成机理。研制出的制品其质量和使用性能接近同类进口产品 ,具有良好的市场前景和广泛的推广应用价值。 相似文献
989.
Natural amorphous polymer poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3HB4HB) containing 41 mol % of 4HB was blended with poly(3‐hydroxybutyrate) (PHB) with an aim to improve the properties of PHB. The influence of P3HB4HB contents on thermal and mechanical properties of the blends was evaluated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, stress–strain measurement and thermo gravimetric analyzer. Miscibility of PHB/P3HB4HB blends was mainly decided by the contents of P3HB4HB. When P3HB4HB exceeded 50 wt %, the two polymer phases separated and showed immiscibility. The addition of P3HB4HB did not alter the crystallinity of PHB, yet it diluted the PHB crystalline phase as revealed by DSC studies. DSC and FTIR results showed that the overall crystallinity of the blends decreased remarkably with increasing of P3HB4HB contents. Decreased glass transition temperature and crystallinity imparted desired flexibility for the blends. The ductility of the blends increased progressively with increasing of P3HB4HB content. Thus, the PHB mechanical properties can be modulated by changing the blend composition. P3HB4HB did not significantly improve the thermal stability of PHB, yet it is possible to melt process PHB without much molecular weights loss via blending it with suitable amounts of P3HB4HB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
990.
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 总被引:3,自引:0,他引:3
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%。 相似文献