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1.
文献[1—4]报导了在纯溶液中或在铂族金属存在下,用络合直接滴定或返滴定法测定钯。Raoot提出,用硫脲作掩蔽剂选择性络合滴定测定钯的方法,并应用于铜钯、钐钯、镍钯、钴钯合金以及其它合金中钯的测定。本文提出,大量银存在下的银钯焊料中钯的络合滴定法。方法简便、快速、准确,用于实际试样分析,结果满意。 相似文献
2.
纳米碳纤维负载钯催化剂在Heck反应中的应用——载体相互作用的影响 总被引:1,自引:0,他引:1
使用多元醇还原法制备了均匀分散的钯纳米颗粒.将钯纳米颗粒负载于板式、鱼骨式和管式纳米碳纤维,得到稳定、可重复使用的非均相催化剂.实验结果表明,钯纳米胶粒同载体之间的电位差对钯在载体上的负载量、粒子大小以及Heck反应中钯的溶失量有很大的影响.在制备过程中,增加钯纳米胶粒同纳米碳纤维表面的电位差能够大大降低钯在Heck反应中的流失.催化剂的反应活性随钯粒子的增大而降低. 相似文献
3.
分别以Pd(NO3)2,Pd(NH3)4(NO3)2和H2Pd Cl4为钯前驱体制备了Pd/Ce0.67Zr0.33O2(CZ)催化剂.以硝酸钯为钯前驱体制得的Pd/CZ(NO)催化剂具有较高的储氧量,存在较多的小的钯簇,其钯与载体间相互作用较强,因此在三种新鲜催化剂中对HC和CO的消除表现出了最好的催化活性.以硝酸四氨钯为钯前驱体制得的Pd/CZ(NH)催化剂具有较高的钯分散度,存在较多的大的钯簇,同时存在金属态和氧化态的钯,从而对NO和NO2的消除表现出了较好的催化活性.以氯钯酸为钯前驱体制得的Pd/CZ(Cl)催化剂由于钯分散度较小,钯与载体间作用较弱,存在的CeOCl抑制了氧空穴的生成,因此对各种反应物的催化活性都较低.但Pd/CZ(Cl)催化剂表现出了较好的热稳定性,这是由于老化处理消除了残余的氯物种并且促进了钯与载体间的作用. 相似文献
4.
建立健全测定银钯合金中银和钯含量的检测方法,对实现银钯合金中银和钯的高精度分析以及资源化利用有着重大意义。实验建立了电感耦合等离子发射光谱法(ICP-AES)同时测定银钯合金中银钯含量的分析方法。实验采用先加入10mL硝酸,再加入50mL过量盐酸混合,采用加热套混合消解银钯合金并混合定容在酸性浓度为18%HCl为介质中,然后通过控制不同的HCl浓度来测定银钯含量。实验结果表明:银的最佳检测酸性浓度为18%、钯的最佳酸性检测浓度为4%且该方法的加标回收率在97%-100%之间,相对标准偏差(RSD, n=10)小于2%。 相似文献
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本文提出在EDTA掩蔽下用对苯二酚还原金(Ⅲ)和铱(Ⅳ),无须过滤分离,即可络合滴定钯。测定5—20mg钯时,相对误差小于1%,适用于含金、钯冶金中间产品及金、钯合金中钯的分析。 相似文献
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通过测定加氢反应后反应溶液中金属的溶出量,考察了高分子负载催化剂的稳定性,研究了活性中心金属的种类、价态及分散程度对催化剂稳定性的影响。实验表明,在聚苯乙烯苄基氨茴酸树脂载体上,不同金属物种的催化剂稳定性次序为:Pd混合价态钯>二价钯。随着载体表面钯分散度的增大,钯盐中配体En值的减小,溶剂极性的减弱,钯的流失量也呈下降趋势。 相似文献
10.
铂钯属于贵金属,对于冶炼企业而言,有效回收铂钯,可以提高生产经营单位的经济效益。本文针对某铜冶炼企业工艺中产生的铂钯渣中铂、钯含量较高、难以溶解、不宜直接测定等问题,研究了一种测定铂、钯含量的新方法。首先对铂钯渣样品进行火试金熔融、富集,溶解,再用电感耦合等离子体原子发射光谱仪 (ICP-AES) 测定,方法精密度和准确度好。 相似文献
11.
We report herein the effect of palladium on the redox electrochemistry of ferrocene monocarboxylic acid encapsulated within an organically modified sol-gel glass network (ORMOSIL). It has been found that amount of palladium and its geometrical distribution significantly alter the redox electrochemistry of FcMCA. The geometrical distribution of palladium has been controlled by two methods: (i) palladium is allowed to link within nanostructured network of the ORMOSIL which was subsequently availed from the reactivity of palladium chloride and trimethoxysilane; (ii) palladium powder is encapsulated together FcMCA thus allowing the presence of palladium within the nanoporous domain. The content of palladium is varied by controlling the reaction dynamics of palladium chloride and trimethoxysilane interaction. For this we initially allowed to trigger hydrolysis, condensation and poly-condensation of trimethoxysilane and dimethyldiethoxysilane in acidic medium and subsequently partially dried ORMOSIL film was allowed to interact with palladium chloride. Even with partially dried ORMOSIL derived from trimethoxysilane and dimethyldiethoxysilane undergoes rapid interaction with palladium chloride and the transparent color of ORMOSIL changed to a black colour due to the formation of palladium silicon linkage. The palladium-silicon linkage has been identified by NMR, UV-VIS and transmission electron spectroscopy. The electrochemistry of FcMCA encapsulated within such an ORMOSIL matrix has been studied. Excellent redox electrochemistry of ferrocene monocarboxylic acid having peak potential separation tending to 0 for a multilayered electrode was investigated. The palladium content has been found to affect the redox electrochemistry of ferrocene as well as electrocatalytic efficiency of new ORMOSIL material. The electroanalysis of NADH is reported. The modified electrode is very sensitive to NADH with lowest detection limit of < 1 microM. 相似文献
12.
Abstract Colloidal palladium supported on a chelate resin containing iminodiacetic acid groups was prepared by refluxing the palladium chelate resin in methanol-water. Using the resin-supported colloidal palladium as a catalyst, cyclopentadiene was hydrogenated to cyclopentene in 97.1% selectivity at 100% conversion of cyclopentadiene under 1 atm of hydrogen in methanol at 30°C. Finely dispersed metal particles ranging from 10 to 60 Å in diameter were observed in the resin by electron microscopy. Both x-ray microanalysis for palladium and elution analysis of palladium ion with an aqueous solution of ethylenediaminetetraacetic acid disodium salt demonstrated the existence of large amounts of palladium ion complexes in the resin. The amount of palladium metal in the resin was estimated to be about 5% of the total palladium. Since the resin, after removal of most of the ionic palladium, exhibited almost the same catalytic activity as before, it was concluded that the finely dispersed metal particles are the active species in the catalyst. 相似文献
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To clarify the dissolving behavior of palladium, the effect of temperature on the amount of palladium dissolved in borosilicate glass was investigated. Glass and palladium oxide, selected as a starter material, were mixed and heated at prescribed temperature. The amount of dissolved palladium became higher with temperature increasing up to 850 °C, and lower above 850 °C. Above 850 °C, the reduction of palladium oxide was accelerated. For palladium dissolution in borosilicate glass, not only the viscosity and basicity of the glass but also the decomposition temperature of the initial palladium species seemed to affect the amount of palladium dissolved in glass. 相似文献
14.
Huancheng Qiao
Kenneth W. Jackson
《Spectrochimica Acta Part B: Atomic Spectroscopy》1991,46(14):1841-1859The effects of palladium and mixtures containing palladium on the absorbance characteristics of lead, thallium, cadmium, selenium, manganese and cobalt are described. These data, together with results of scanning electron microscopy showing the distribution of palladium on the graphite surface, indicate that palladium has a physical mechanism of analyte modification. During furnace heating, the analyte dissolves in molten palladium and may combine with it chemically. However, the rate limiting step leading to atomization appears to be diffusion of the analyte from palladium. The addition of magnesium, molybdenum or powdered carbon increases the speed of diffusion by causing palladium to form smaller droplets, and hence produces sharper absorbance peaks. Palladium becomes less effective as the atomization temperature increases, because the rate of diffusion is higher. This accounts for palladium having only a small stabilizing effect on less volatile elements such as manganese and cobalt. The addition of ascorbic acid to palladium has no significant effect on its modifying properties in a dilute nitric acid matrix. Results of kinetic studies on the atomization of gold are consistent with analyte diffusion out of palladium as the rate-limiting step leading to atomization. 相似文献
15.
氢氧化钠沉淀分离铜、钯的动力学研究及分析应用 总被引:2,自引:0,他引:2
进行了氢氧化钠沉淀分离铜钯的动力学研究,计算了用该法分离铜钯对测定引起的误差,将该法用于测定乙醛催化剂中的钯含量,获得满意结果。 相似文献
16.
Gaikwad AV Holuigue A Thathagar MB ten Elshof JE Rothenberg G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(24):6908-6913
Leaching of palladium species from Pd nanoparticles under C--C coupling conditions was observed for both Heck and Suzuki reactions by using a special membrane reactor. The membrane allows the passage of palladium atoms and ions, but not of species larger than 5 nm. Three possible mechanistic scenarios for palladium leaching were investigated with the aim of identifying the true catalytic species. Firstly, we examined whether or not palladium(0) atoms could leach from clusters under non-oxidising conditions. By using our membrane reactor, we proved that this indeed happens. We then investigated whether or not small palladium(0) clusters could in fact be the active catalytic species by analysing the reaction composition and the palladium species that diffused through the membrane. Neither TEM nor ICP analysis supported this scenario. Finally, we tested whether or not palladium(II) ions could be leached in the presence of PhI by oxidative addition and the formation of [Pd(II)ArI] complexes. Using mass spectrometry, UV-visible spectroscopy and 13C NMR spectroscopy, we observed and monitored the formation and diffusion of these complexes, which showed that the first and the third mechanistic scenarios were both possible, and were likely to occur simultaneously. Based on these findings, we maintain that palladium nanoparticles are not the true catalysts in C--C coupling reactions. Instead, catalysis is carried out by either palladium(0) atoms or palladium(II) ions that leach into solution. 相似文献
17.
Tetsushi Kijima Irakli Javakhishvili Katja Jankova S?ren Hvilsted Shun Kodama Masashi Sugiya Hideo Sawada 《Colloid and polymer science》2012,290(7):589-597
Fluoroalkyl end-capped betaine-type cooligomeric nanocomposites-immobilized palladium nanoparticles were prepared by the reactions
of palladium chloride with sodium acetate in the presence of sodium chloride and the corresponding fluorinated cooligomers.
Outer blocks of poly(2,3,4,5,6-pentafluorostyrene)-containing ABA-triblock copolymeric nanocomposites-immobilized palladium
nanoparticles were prepared by the use of the corresponding block copolymers under similar conditions. TEM images showed that
palladium nanoparticles can be immobilized outside the fluorinated cooligomeric nanocomposite cores; in contrast, palladium
nanoparticles can be effectively immobilized inside these fluorinated ABA-triblock copolymeric nanocomposite cores. Thus,
these two different fluorinated copolymers enabled the controlled immobilization of palladium nanoparticles in the fluorinated
nanocomposite cores. These fluorinated nanocomposites-immobilized palladium nanoparticles were also applied to the catalysts
for Suzuki-Miyaura cross-coupling reaction, and the different reactivity between these nanocomposites was observed. 相似文献
18.
Patil KR Hwang YK Kim MJ Chang JS Park SE 《Journal of colloid and interface science》2004,276(2):333-338
A new approach to the formation of palladium nanoparticulate films with diameter between 6 and 50 nm by the solid-liquid interface reaction technique (SLIRT) has been presented. A solid film of palladium nitrate was formed by the modified spin coating method. This film is subsequently immersed in a reducing solution to initiate a reaction at the interface and ultimately transforms it to a palladium metal film. The kinetics of palladium reduction has been studied by UV-visible spectroscopy. The characterization of the palladium film has been performed by various physicochemical techniques such as XRD, ED, XPS, SEM, EDX, TEM, and UV-visible spectroscopy. The texture and morphology of the materials has been investigated by atomic force microscopy (AFM). At a constant palladium nitrate concentration, the average diameter of palladium nanoparticles decreases with an increase of hydrazine concentration. The effect of concentration of hydrazine on the particle size has been discussed. The palladium film formation mechanism has been proposed for the SLIRT. 相似文献
19.
G. N. Altshuler L. A. Sapozhnikova O. G. Altshuler N. V. Malyshenko G. Yu. Shkurenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(4):663-667
Redox reactions involving hydrogen and oxygen in the presence of hybrid nanocomposites containing palladium and copper or
palladium and silver in a cis-tetraphenylcalix[4]resorcinarene polymer matrix were studied. In the composites containing palladium and copper, the redox
transformations involved copper. In the composites with palladium and silver, the redox reactions involved the polymer matrix.
The reductions in the metal-polymer nanocomposites were catalyzed by palladium. 相似文献
20.
本文使用自制的负载有巯基碳粉的泡塑分离富集钯。试验了该富集到对钯的最佳吸附与解脱条件以及23种共存离子的影响。对低钯管理样进行加标回收实验,结果表明,钯的平均回收率为89.65%,RSD=3.71%。 相似文献