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胶体钯活化液是美国学者Shipley于1961年首先研究成功的,它的催化活性和由此获得的化学镀层与非金属基体的结合力远优于敏化——活化两步法,取得了极其广泛的应用。胶体钯活化液的组成一般为: 氯化钯氯化亚锡盐酸(37%) 锡酸钠 1g/l 75~80g/l 300ml/l 7g/l Shipley的胶体钯活化液(也叫酸基型胶体钯)含有大量的盐酸,使用时工作条件差又污染了环境,因而提出了用氯化钠代替大部分盐而配制了盐基型胶体钯。这样便大大地改善 相似文献
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几种氯化物对胶体钯活化液稳定性及其催化活性的影响 总被引:1,自引:0,他引:1
胶体钯活化液的稳定性主要取决于Sn~(2+)、H~+和CΓ的浓度.NaCl、NH_4CI或KCl代替盐酸能增强活化液的稳定性,且可保持其催化活性. 相似文献
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本试验是一种评价影响钯—锡活化液性能的定量因素的新试验。在本试验中,比较了溶解的铜、氯化亚锡和活性钯的浓度与活化液的特性。在试验中特意用减小活化液稳定性的办法来加速活化液失效。实验的结果表明,盐基活化液比酸基活化液要好。钯—锡活化液是在化学镀之前用来催化非导体镀件。活性钯具有胶体的性质,用高浓度的二价锡作抗絮凝剂使之稳定。用卤化物,最好是氯化物来防止亚锡水解。浓缩活化液是用氯化亚锡和氯化钯之间的相互的化学作用来制备。实际上,在浓缩液中含有零价的钯、氯 相似文献
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以黄铜为基材,研究了吡啶添加剂-氨盐体系的电镀钯工艺,分析了钯盐、氯化铵、吡啶添加剂质量浓度,温度及pH对镀液和镀层质量的影响.在Pd(NH3)2Cl220 g/L,NH4Cl 15 g/L,NH3·H2O 35 mL/L,吡啶添加剂25 g/L,pH 7~8,温度25~35℃和电流密度0.4~0.5 A/dm2的条件下,获得了厚度达35 μm的光亮钯镀层.该镀层与基体结合力良好,能满足光电经纬仪的工作要求. 相似文献
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以氮杂碳包铁(Fe@NC)为载体、聚乙烯吡咯烷酮为稳定剂,通过液相还原H_2PdCl_4和后续焙烧法制备新型的磁可分离Pd/Fe@NC催化剂,并进行AAS、TEM、XRD和XPS表征,将制备的催化剂用于苯甲醇无溶剂需氧氧化反应,考察焙烧温度、反应温度、催化剂用量和碱性助剂对其催化性能的影响,研究催化剂的循环使用性能。结果表明,Pd负载质量分数为4.86%,Pd有效负载比例为97.2%;Pd颗粒在载体上分散均匀,平均粒径为5 nm;催化剂活性物种组成包括Pd~0和含量较低的络合Pd(Ⅱ)及PdO。在无溶剂、无碱性助剂、O_2分压101.325 kPa(O_2流量为20 m L·min~(-1))和低催化剂用量[n(Pd)∶n(苯甲醇)=1∶2 000]条件下,Pd/Fe@NC可高效催化苯甲醇的氧化反应,100℃反应24 h,苯甲醇转化率达86%,苯甲醛选择性为87%,反应过程中无任何有毒物质产生与排放。催化剂循环使用7次后,催化活性略有提高,催化过程中络合的Pd(Ⅱ)向Pd0的转化是其活性提高的主要原因。 相似文献
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SiO_2-TiO_2负载钯催化剂的制备及其催化Suzuki反应研究 总被引:1,自引:0,他引:1
以正硅酸乙酯和钛酸正丁酯作前体,通过均匀沉淀法制备了SiO2-TiO2复合氧化物,并采用X射线粉末衍射(XRD)对复合氧化物进行了表征。采用浸渍制备了复合氧化物负载的钯催化剂Pd/SiO2-TiO2,并考察了负载催化剂在Suzuki反应中的催化性能。当投料摩尔比n(Pd)∶n(PhBr)∶n[PhB(OH)2]∶n(K2CO3)为1∶70∶105∶140,Ti/Si摩尔比和钯质量分数分别为0.5和2.0%时,回流反应10 h,联苯产率达92.8%。负载催化剂通过简单过滤即可回收利用,在5次循环使用过程中,催化活性除第1次有明显降低外,其后基本保持不变。 相似文献
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M. García-Gabaldón V. Pérez-Herranz J. García-Antón J. L. Guiñón 《Journal of Applied Electrochemistry》2007,37(10):1145-1152
This paper presents an electrochemical study about the activating solutions of the electroless plating of polymers, containing
Pd(II), Sn(II) and Sn(IV) mixtures in HCl as main components. The objective of the study is the voltammetric characterization
of these solutions by cyclic and linear voltammetry in order to study the recovery of tin and palladium from these solutions.
The effect of concentration and rotation rate on the current−potential curves was studied using the RDE technique. The electrochemical
behaviour of solutions prepared in the laboratory was performed as a prior step to the further study of real activating rinsing
solutions. The electrochemical reduction of Pd(II) takes place in two one-electron transfer steps which are mass transport
controlled. The electrochemical reduction of Sn(II) and Sn(IV) is also mass transport controlled and takes place with direct
formation of metallic tin, although the electrochemical reduction of Sn(IV) only takes place in solutions with HCl concentrations
higher than 1 M. The presence of additives in the real solutions prevent the chemical reduction of Pd(II) and the formation
of Sn(IV) hydroxylated complexes. This causes the appearance of well defined diffusion waves attributable to the electrochemical
reduction of Pd(II) and Sn(IV). Hence, the recovery of both species simultaneously as well as separately could be carried
out, if appropriate conditions are selected. 相似文献
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以植酸钙(PA-Ca)为载体、H2Pd Cl4为前驱体、甲醇为还原剂,制备了PA-Ca负载Pd的Pd/PA-Ca催化剂,对其进行XRF、BET、SEM、TEM、XRD和XPS表征,并用于苯甲醛氧化制备苯甲酸反应,考察催化剂用量、反应温度和溶剂种类对催化剂催化性能的影响。结果表明,催化剂中负载Pd质量分数为1.03%,钠质量分数为1.05%;合成的PA-Ca载体为晶化程度较低的介孔材料,比表面积为18.85 m~2·g~(-1);催化剂活性物种为Pd0和PdO。在催化剂用量n(苯甲醛)∶n(Pd)=2 000∶1、乙腈作溶剂、O_2压力101.325 k Pa(流速20 m L·min~(-1))、反应温度30℃和反应时间4 h条件下,苯甲醛转化率为83%,苯甲酸选择性为100%;催化剂具有较好的稳定性,可循环使用3~4次。 相似文献
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The anions of PdCl(2)L(2) and Pd(OAc)(2), precursors of palladium(0) used in cross-coupling and Heck reactions, play a crucial role in these reactions. Tricoordinated anionic complexes Pd(0)L(2)Cl(-) and Pd(0)L(2)(OAc)(-) are the effective catalysts instead of the usually postulated Pd(0)L(2) complex. The anion ligated to the palladium(0) affects the kinetics of the oxidative addition to ArI as well as the structure and reactivity of the arylpalladium(II) complexes produced in this reaction. Thus, pentacoordinated anionic complexes are formed, ArPdI(Cl)L(2)(-) or ArPdI(OAc)L(2)(-), the precursor of neutral trans-ArPd(OAc)L(2), instead of the usually postulated trans-ArPdIL(2) complex (L = PPh(3)). 相似文献
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以琥珀酸二异辛酯磺酸钠(AOT)为表面活性剂,分别以抗坏血酸、硼氢化钠(NaBH4)、七水硫酸亚铁(FeSO4.7H2O)为还原剂,成功地制备了球状的钯纳米粒子。采用扫描电镜和X射线衍射仪对产物进行了表征,钯纳米颗粒的平均粒径约50~150nm。结果表明,当琥珀酸二异辛酯磺酸钠的浓度为15g/L,氯化钯的浓度为0.0025mol/L,抗坏血酸的浓度为0.05mol/L,40℃反应2h时,可制得大小均匀、粒径小、分散性好的钯纳米颗粒。 相似文献
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The stability of composite palladium membranes is of key importance for their application in hydrogen energy systems. Most of these membranes are prepared by electroless plating, and beforehand the substrate surface is activated by a SnCl_2–PdCl_2 process, but this process leads to a residue of Sn, which has been reported to be harmful to the membrane stability. In this work, the Pd/Al_2O_3 membranes were prepared by electroless plating after the SnCl_2–PdCl_2 process. The amount of Sn residue was adjusted by the SnCl_2 concentration, activation times and additional Sn(OH)_2coating. The surface morphology, cross-sectional structure and elemental composition were analyzed by scanning electron microscopy(SEM), metallography and energy dispersive spectroscopy(EDS), respectively. Hydrogen permeation stability of the prepared palladium membranes were tested at450–600 °C for 400 h. It was found that the higher SnCl_2 concentration and activation times enlarged the Sn residue amount and led to a lower initial selectivity but a better membrane stability. Moreover, the additional Sn(OH)_2coating on the Al_2O_3 substrate surface also greatly improved the membrane selectivity and stability.Therefore, it can be concluded that the Sn residue from the SnCl_2–PdCl_2 process cannot be a main factor for the stability of the composite palladium membranes at high temperatures. 相似文献
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以丁基苯乙烯(BS)为疏水单体,采用自由基胶束聚合法合成了丙烯酰胺(AM)/丁基苯乙烯(BS)疏水缔合水溶性共聚物(PSAM),来解决该类聚合物热稳定性较差的难题。研究得到了适宜的反应条件:n(K2S2O8)∶n(Na2SO3)=3∶1,引发剂和BS相对于单体总量的摩尔分数分别为0.06%和1.45%,总单体在水里的质量分数为20%,SDS在水里的质量分数为5.5%,pH=6~7,反应温度50℃。采用该反应条件得到PSAM的临界缔合质量浓度为1 g/L,对应的水溶液表观黏度为21 mPa.s;质量浓度为2 g/L时,对应的水溶液表观黏度为78 mPa.s;质量浓度为1 g/L和2 g/L的PSAM在浓度为0.137 mol/L的NaC l水溶液中,于80℃老化120 d后的表观黏度分别为11.8 mPa.s和49.3 mPa.s,黏度保留率分别为42.1%和45.1%。通过元素分析、UV、FTIR表征了PSAM的分子结构;DSC分析表明PSAM为嵌段共聚物,两个玻璃化转变温度分别为BS链段的106℃和丙烯酰胺链段的203℃。 相似文献