高分子负载钯催化剂中载体主链在催化加氢反应中的作用

报导几种以聚2,6-二甲基1,4-苯醚(PPO)和聚砜(PSu)为主链的负载钯催化剂对1-辛烯和环戊二烯在温和条件下的催化加氢活性与选择性。官能团化的PPO负载钯催化剂对1-辛烯的催化加氢活性大于官能团化的PSu负载钯催化剂的活性,但前者在加氢过程中的活性下降比后者快得多;官能团化的PPO负载钯催化剂在1-辛烯加氢过程中活性很快下降的原因与其强的异构化性能和异构化产物有关。相同配体的两种负载钯催化剂对环戊二烯的催化加氢表现在活性上,PPO低于PSu,而选择性PPO高于PSu。表明除了按预计与钯直接配位的配体外,载体主链结构对负载钯催化剂的加氢性能也有显著影响。     

高分子膦-钯络合催化剂的氢化催化活性和稳定性的考察

本文报道高分子膦-钯络合催化剂的合成及对催化剂催化加氢的活性、稳定性进行考察的结果。与文献对比表明,高分子膦-钯络合催化剂具有良好的稳定性和催化活性,膦化物不失为一类优良的配位体。     

烯烃加氢催化剂—聚丙烯腈-钯络合物

近年来出现了用过渡金属化合物和具有官能团的高聚物络合的所谓高分子催化剂.这种催化剂在催化某些反应上具有活性高,选择性好,容易分离及反应条件温和等优点.因此引起人们的重视. 我们用聚丙烯腈为配位体与带结晶水的氯化钯制备了聚丙烯腈-钯络合物.该络合物在催化庚烯-1的加氢时显示良好的催化活性,并且催化活性明显地受到络合物中N/Pd     

高分子钯络合物催化的亚胺化合物的加氢反应

制备了一系列以二氧化硅为载体的侧链上含有各种氮配位基团的聚硅氧烷-钯络合物,这些高分子钯络合物能够在常温常压下催化亚胺化合物的加氢反应并表现出不同程度的催化活性.对其中聚-(N,N-二乙酰基)-γ-氨丙基硅氧烷-钯络合物催化的亚苄基苯胺的加氢反应做了比较深入的研究,发现该催化剂在反应中是稳定的并给出唯一的加氢产物,络合物中的N/Pd原子比、反应温度以及不同底物对反应速度的影响也被报道.     

马来酸-苯乙烯共聚物-钯络合物催化剂在加氢反应中的变化及钯的回收利用

马来酸-苯乙烯共聚物-钯络合物在催化加氢过程中,络合在高分子配体上的钯离子易被还原为Pd(0),而部分地脱落下来,这可从XPS及电镜分析证实。催化活性中心可能是高分子络合(或隔离保护)的Pd(0)微粒。本文研究了高分子钯催化剂在硝基苯加氢过程中,钯的用量范围,溶剂对催化活性的影响,催化剂的回收与其活性及金属钯的回收与再利用。此外还测定了硝基苯催化加氢的活化能。     

高分子固载钯金属络合物在脱羰及芳基化反应中的催化行为

本文考察了高分子钯络合物在脱羰及芳基化反应中的催化行为。证实了对钯具有很强络合能力的巯基配位基与钯形成的络合物对于催化此反应具有良好的活性;並较常用的膦、胺、腈等配位基与钯形成的高分子络合物更为稳定。文章对反应中导致催化剂失活的可能因素进行了探讨;对胺类及其用量、温度等的影响及可能的副反应作了实验研究。     

聚乙烯吡啶二氯化钯络合物催化烯烃加氢

本工作合成和表征了聚乙烯吡啶二氯化钯络合物,并研究了其对烯烃加氢的催化性能。实验结果表明:该类催化剂的活性高于均相类似物,而且同催化剂的氮/钯原子比、载体的颗粒度和溶剂的溶胀及配位能力有明显的关系。对烯烃加氢具有选择性并随催化剂的氮/钯原子比而变化。还发现它们对空气稳定、可循环使用而不污染产物,对氢气还原的稳定性也优于均相类似物。     

Pd/离子交换树脂催化剂的制备及加氢性能

用各种离子交换树脂为载体制备的载钯催化剂可用于对不饱和化合物的常温常压加氢。其加氢活性既与载体功能基的性质有关也与载体的物理特性有关。其中以孔度大、表面粗糙的树脂作载体利于底物与氢的扩散,加氢活性高。载体功能基要求与钯有一定的配位能力,同一功能基的配位原子数最好≤2。催化剂活性中心的价态对加氢活性也有影响,两种以上价态的钯比例适当协同作用时活性高。     

硅胶负载聚乙烯吡啶-聚[苯乙烯-顺丁烯二酸]-钯催化剂的结构研究

利用X-光电子能谱、紫外-可见光谱、电子显微镜等技术研究了硅胶负载的聚乙烯吡啶-聚[苯乙烯-顺丁烯二酸]-钯催化剂的结构.发现催化剂中活性组分除钯(0)外,还存在少量钯(Ⅱ).第二种高分子的存在可以影响钯(Ⅱ)的相对含量.催化剂中钯以很小的粒子均匀分布在载体上,因此具有良好的催化加氢性能.     

杨梅形高分子载体的链结构对钯加氢催化剂活性的影响

制备了四种杨梅形高分子载钯催化剂,考察了它们对苯乙烯的催化加氢活性。结果表明、具有不同配位功能基的催化剂,其催化活性有较大差异,其中对金属离子吸附能力弱的分散钯催化剂表现出较高的催化活性。接枝链上嵌入丙烯酸甲酯单元抑制了催化剂的加氢活性。反应体系的酸度对催化剂的活性的影响比较复杂,有等进一步探讨。     

高分子负载催化剂在硝基苯加氢中的双金属协同效应

高分子负载催化剂在硝基苯加氢中的双金属协同效应＊郦海青廖世健＊＊徐筠余道容（中国科学院大连化学物理研究所，大连１１６０２３）关键词聚乙烯吡咯烷酮，负载型催化剂，双金属催化剂，协同效应，硝基苯，加氢，苯胺在多相催化中，双金属和多金属催化剂是常见的，但在...     

Preparation and catalytic properties of NR-stabilized palladium colloids

Palladium colloids revealing narrow particle size distributions can be obtained by chemical reduction using tetra–alkylammonium hydrotriorganoborates. Combining the stabilizing agent [NR] with the reducing agent [BEt₃H^?] provides a high concentration of the protecting group at the reduction centre. Alternatively, NR₄X (X = halogen) may be coupled to the metal salt prior to the reduction step: addition of N(octyl)₄Br to Pd(ac)₂ in THF, for example, evokes an active interaction between the stabilizing agent and the metal salt. Reduction of NR-stabilized palladium salts with simple reducing agents such as hydrogen at room temperature yields stable palladium organosols which may be isolated in the form of redispersible powders. The anion of the palladium salt is crucial for the success of the colloid synthesis. Electron microscopy shows that the mean particle size ranges between 1.8 and 4.0 nm. An X–ray–photoelectron spectrscopic examination demonstrated the presence of zerovalent palladium. These palladium colloids may serve as both homogeneous and heterogeneous hydrogenation catalysts. Adsorption of the colloids onto industrially important supports can be achieved without agglomeration of palladium particles. The standard activity of a charcoal catalyst containing 5% of colloidal palladium determined through the cinnamic acid standard test was found to exceed considerably the activity of the conventional technical catalysts. In addition, the lifespan of the catalyst containing a palladium colloid, isolated from the reduction of [N(octyl)₄]₂PdCl₂Br₂ with hydrogen, is superior to conventionally prepared palladium/charcoal (Pd/C) catalysts. For example, the activity of a conventional Pd/C catalyst is completely suppressed after 38×10³ catalytic cycles per Pd atom, whereas the colloidal Pd/C catalyst shows activity even after 96times;10³ catalytic cycles.     

Preparation of Polyoxometalate-Stabilized Colloidal Solutions of Palladium Metal and Catalysts Supported on Them

Sols containing Pd(0) clusters with polyoxo anions are prepared by the reduction of colloidal solutions of polyhydroxo complexes of Pd(II) in the presence of Mo(VI), W(VI), V(V), and Nb(V) polyoxo anions. The cluster sizes varied within the limits of 1–10 nm depending on the nature of the polyoxo anion. The stability of sols toward coagulation depends on the ratio between the palladium and polyoxo anion amounts in solution and on the composition of the solvent. Supported Pd catalysts are obtained by the adsorption of particles from sols; Pd can exist in these catalysts as individual particles or associates or form filamentary structures.     

Microwave-assisted Suzuki reaction catalyzed by Pd(0)-PVP nanoparticles

Suzuki cross-coupling reaction was successfully carried out in ethanol utilizing a palladium colloidal solution stabilized by polyvinylpyrrolidone (PVP). High isolated yields (75-97%) to biaryls were obtained using different bases, aryl halides, and aryl boronic acids with a small loading of the palladium catalyst. Pd(0)-PVP nanoparticles with 3-6 nm of medium diameter were prepared from Pd(OAc)₂ in the presence of the stabilizer PVP using methanol as the reducing agent.     

A colloid "digesting" route to novel, thermally stable high surface area ZrO2 and Pd/ZrO2 catalytic materials

Zirconia having high thermal stability and high surface area (up to 160 m(2)/g at 700 degrees C) has been prepared by a colloidal "digesting" process. This material having demonstrated high surface areas at elevated temperatures was then applied as a catalyst support. A Pd colloid with diameter of approximately 12 nm has been successfully deposited on the high surface area zirconia material. All systems have been well characterized by TEM, X-ray diffraction, N2 adsorption isotherms, FTIR, elemental analysis and dynamic light scattering techniques. The colloidal Pd particles have been found homogeneously well dispersed in the hydrous zirconia matrix without aggregation. The Pd/ZrO2 catalysts have been screened for cyclohexene and 1-hexene hydrogenation activity and it was found that the catalyst is extremely active.     

环烷酸钴-氯二异丁基铝催化体系相态的研究

研究了Co(naph) 2 Al(i Bu) 2 Cl催化体系的相态 .通过Tyndall效应、电镜观察和超过滤实验 ,证明了Co(naph) 2 Al(i Bu) 2 Cl催化体系在溶有丁二烯的苯溶剂中以纳米级小颗粒分散 ,在较佳配比时 ,粒径在 1～10 0nm之间 ,为胶体催化剂 ,属于高度分散的多相催化体系 .催化剂的活性位位于胶粒表面 ,催化剂颗粒是无定形的 .以较佳配比得到的催化剂颗粒较小、分布均匀 ,催化丁二烯聚合反应活性高 .归纳出胶体催化剂的制备特点为外观类似于均相催化体系 ,但是制备方法 (各组分配比、加入顺序、陈化等 )对催化活性有明显的影响 .并给出将胶体催化动力学作均相动力学近似的条件 ,在聚合反应初期 ,且单体浓度比烷基铝以及其他填加物浓度大 2～ 3数量级     

Synthesis and characterization of Sibunit-supported Pd–Ga,Pd–Zn,and Pd–Ag catalysts for liquid-phase acetylene hydrogenation

Pd/Sibunit and Pd–M/Sibunit (M = Ga, Zn, or Ag) catalysts have been synthesized, and their catalytic properties in liquid-phase acetylene hydrogenation have been investigated. Doping of the palladium catalyst with a metal M leads to the formation of the Pd₂Ga, PdZn, or Pd_0.46Ag_0.54 bimetallic compound. The bimetallic particles are much smaller (1.6–2.0 nm) than the monometallic palladium particles (4.0 nm). Doping with zinc raises the ethylene selectivity by 25% without affecting the activity of the catalyst. Specific features of the effect of each of the dopants on palladium are reported.     

Properties of Pd–Ag/C catalysts in the reaction of selective hydrogenation of acetylene

Samples of Pd/C and Pd–Ag/C, where C represents carbon nanofibers (CNFs), are synthesized by methane decomposition on a Ni–Cu–Fe/Al₂O₃ catalyst. The properties of Pd/CNF are studied in the reaction of selective hydrogenation of acetylene into ethylene. It is found that the activity of the catalyst in hydrogenation reaction increases, while selectivity decreases considerably when the palladium content rises. The obtained dependences are caused by the features of palladium’s interaction with the carbon support. At a low Pd content (up to 0.04 wt %) in the catalyst, the metal is inserted into the interlayer space of graphite and the catalytic activity is zero. It is established by EXAFS that the main share of palladium in catalysts of 0.05–0.1 wt % Pd/CNF constitutes the metal in the atomically dispersed state. The coordination environment of palladium atoms consists of carbon atoms. An increase in the palladium content in a Pd/CNF catalyst up to 0.3 wt % leads to the formation of highly dispersed (0.8–1 nm) Pd particles. The Pd/CNF samples where palladium is mainly in the atomically dispersed state exhibit the highest selectivity in the acetylene hydrogenation reaction. The addition of silver to a 0.1 wt % Pd/CNF catalyst initially probably leads to the formation of Pd–Ag clusters and then to alloyed Pd–Ag particles. An increase in the silver content in the catalyst above 0.3% causes the enlargement of the alloyed particles and the palladium atoms are blocked by a silver layer, which considerably decreases the catalytic activity in the selective hydrogenation of acetylene.     

Structure and catalytic properties of nanosized alumina supported platinum and palladium particles synthesized by reaction in microemulsion

Mixtures of nanosized platinum and palladium particles have been prepared by reduction of salt-containing microemulsion droplets using hydrazine as the reducing agent. To avoid possible negative effects of the presence of sulfur compounds during the preparation the microemulsion was made using the sulfur-free nonionic polyoxyethylene 4 lauryl ether surfactant. Transmission electron microscopy showed that the as-prepared mixtures contained crystalline platinum particles of fairly homogeneous size (20 to 40 nm) with adsorbed amorphous palladium particles 2 to 5 nm in size. Catalyst samples were prepared by depositing the nanoparticles on a gamma-Al(2)O(3) support followed by heating in air at 600 degrees C. Alloyed particles of platinum and palladium with sizes ranging from 5 to 80 nm were obtained during the heating. The majority of the particles had the fcc structure and their compositional range was dependent upon the Pt:Pd molar ratio of the microemulsion. A catalyst prepared from a microemulsion with a 20:80 Pt:Pd molar ratio showed the highest catalytic activity for CO oxidation, while pure platinum and palladium catalysts showed higher sulfur resistance. These results differ from the performance of conventional wet-impregnated catalysts, where a 50:50 Pt:Pd molar ratio resulted in the highest catalytic activity as well as the highest sulfur resistance.     

THE EFFECT OF MODIFICATION OF COORDINATING GROUPS ON THE CATALYTIC BEHAVIORS OF POLYMER CATALYSTS

Several polymer-supported palladium complex catalysts containing two different coordinatinggroups were prepared and the cooperative effect of the coordinating groups on the catalytic behaviorsof polymer catalysts was studied. It was found that poly(acrylic acid-co-acrylonitrile)-Pd complex(PAA-AN-Pd) is a more active and stable catalyst for hydrogenation than both poly(acrylic acid)-Pd and poly(acrylonitrile)-Pd complexes. A marked change of catalytic behaviors of poly(N-substituted maleamic acid-co-styrene)-Pd complexes was observed in comparison with poly(maleicacid-co-styrene)-Pd complex. Acetophenone was reduced to 1-phenyl ethanol by poly(N-phenylmaleamic acid-Co-styrene)-Pd complex (N-1-Pd), but ethylbenzene was obtained using poly(maleicacid-co-styrene)-Pd complex as a catalyst. The influence of solvents, additives and N/Pd gramatomic ratio on the catalytic behaviors of the polymer complexes was investigated.