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41.
探针反应和FTIR法研究Pt与L型沸石的相互作用董家禄,朱建华,须沁华,张婕,刘大壮(南京大学化学系,南京,210008)(郑州工学院化工系,郑州,450002)关键词Pt/L沸石,沸石催化剂,异丙醇分解反应,Pt-载体相互作用Pt的分散度和电子状态... 相似文献
42.
Summary The advantages and disadvantages of high performance precipitation liquid chromatography have been demonstrated for polystyrene
homopolymers. Depending on the mobile phase composition at the dissolution point of the polymeric sample and surface properties
of the stationary phase, elution is governed either by a solution process or by adsorption. A contribution by adsorption was
noticed on silica as well as on reversed phases based on silica with a normal phase gradient of increasing polarity (heptane
to dichloromethane). Elution was solely governed by solubility of the polymers on both types of stationary phase for polystyrenes
with a molecular weight above 35 000 and reversed phase gradient of decreasing polarity (methanol to dichloromethane). Under
these conditions an identical dependence of elution solvent composition on sample size was found as for turbidity titrations.
Due to differences in the velocity of the eluent front and the polymeric sample with porous stationary phases the polymers
can be eluted as colloidal solutions Non-porous stationary phases are superior in this respect because the velocities of eluent
and solutes are identical. 相似文献
43.
Tsuneo Okubo 《Colloid and polymer science》2006,284(12):1395-1401
Sedimentation and drying dissipative structural patterns formed in the course of drying colloidal silica spheres (1.2 μm in diameter) in aqueous suspension have been studied in a glass dish and a polystyrene dish. The broad ring patterns are formed within a short time in suspension state by the convection flow of water and colloidal spheres. The broad ring patterns are not formed when a dish is covered with a cap, which demonstrates the important role of the convectional flow of silica spheres and water accompanied with the evaporation of water on the air-suspension interface. The sedimentary spheres always move by the convectional flow of water, and the broad ring patterns became sharp with time. Broad ring and microscopic fine structures are formed in the solidification processes on the bases of the convectional and sedimentation patterns. Drying patterns of the colloidal suspensions containing sodium chloride are star-like ones, which strongly supports the synchronous cooperative interactions between the salt and colloidal spheres. 相似文献
44.
45.
以正庚烷的转化为探针反应 ,研究了添加元素锆对铂重整催化剂性能的影响规律。结果表明 ,在 4 50℃和连续流动条件下 ,Pt/γ -Al2 O3催化剂中引入锆不仅能够提高铂催化剂的稳定性和芳构化产率、抑制氢解和异构化 ,而且能使铂催化剂保持初活性。锆含量在 0 .56%左右 ,其调变作用最为显著。 相似文献
46.
The effect of the calcination temperature of bifunctional Pt/zeolites on the isomerization ofn-hexane has been investigated. The catalyst calcined at 350°C showed the highest metal dispersity and the best activity. The higher selectivity of dimethylbutanes over Pt/H- than over Pt/H-MOR might be attributed to the combined effect of acidity, channel structure and pore size of zeolites. 相似文献
47.
Jaroslav Stejskal Otakar QuadratIrina Sapurina Josef ZemekAlicja Drelinkiewicz Magdalena HasikIvo K?ivka Jan Prokeš 《European Polymer Journal》2002,38(4):631-637
Silica gel microspheres 7 and 15 μm in diameter were coated with an overlayer of polyaniline camphorsulfonate or hydrochloride during the oxidative polymerization of aniline. Coated silica gel and polyaniline precipitate were separated using a difference in sedimentation rate. In an alternative approach, the microspheres were modified with polyaniline in the presence of 35 nm colloidal silica. This technique prevented the macroscopic precipitation of polyaniline. Coatings of neat, 3-aminopropyl- and octadecyl-modified silica gel with polyaniline hydrochloride were compared. The surface composition of coated microspheres was characterized by X-ray photoelectron spectroscopy. Potential applications of particles in electrorheology, organic catalysis, and in modeling of conductivity behavior in composites are demonstrated. 相似文献
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49.
用电化学方法研究了I-3和Ti3+在还原铂表面上的电极反应,由此计算出I-3与Ti3+在还原铂表面上的混合催化反应速率(νmix).当混合催化电位(Emix)位于极限电流区时,νmix对[Ti3+]为零级反应,对[I-3]为一级反应,且正比于电极旋转速率的平方根,H+浓度影响不大.由动力学方法研究的结果证实了电化学研究结果的正确性,致使可用电化学方法解释溶液中的异相催化问题 相似文献
50.
前驱体水解对纳米铂形状控制合成的影响 总被引:5,自引:1,他引:5
以聚丙烯酸钠(NaPA: M_w ≈ 2100)为保护剂,对比研究了H_2还原K_2PtCl_4 和K_2PtCl_6水溶液制备纳米铂晶粒的形状选择性,揭示了前驱体的水解对纳米铂 晶粒的形状控制合成具有显著影响。文献中通常采用的合成立方形状纳米铂的 K_2PtCl_4前驱体在水溶液中不稳定,避光静置一周会析出黑色沉淀。这种不稳定 性导致了以K_2PtCl_4为Pt前驱体的合成结果难以重复。相比而言,避光静墨的 K_2PtCl_6水溶液很稳定,以它为前驱体合成的纳米铂通常为削角八面体。 K_2PtCl_6水溶液暴露于室内光线中会出现[PtCl_6]~(-2)的光致水解。当[PtCl_6] ~(2-)的紫外特征吸收峰(260nm)由于光致水解完全消失后,以聚丙烯酸钠为保护剂 ,通过H_2还原可以有选择性地(约80%)合成由{100}晶面包裹的立方体形状的纳米 铂。 相似文献