硝基芳烃氢化还原反应中高分子负载催化剂的双金属协同效应

制备了聚Ｎ－乙烯基－２－吡咯烷酮ＰＶＰ负载钯催化剂Ｐｄ／ＰＶＰ及各种双金属催化剂（１－ｍ）Ｐｄ－ｍＭ／ＰＶＰ，并用于硝基芳烃的加氢还原中，其中Ｐｄ／ＰＶＰ中加入Ｈ２ＰｔＣｌ６的效果最佳，碱的用量、溶剂和Ｐｄ、Ｐｔ的比例都对催化剂的活性有明显的影响，双金属催化剂０．８０Ｐｄ－０．２０Ｐｔ／ＰＶＰ在温和条件下能高活性，高选择性地催化硝基芳烃还原，得到相应的芳胺。     

A homogeneous catalyst made of poly(4-vinylpyridine-co-N-vinylpyrrolidone)-Pd(0) complex for hydrogenation of aromatic nitro compounds

Poly(4-vinylpyridine-co-N-vinylpyrrolidone)(VPy-co-NVP) and its palladium complex (VPy–NVP–Pd) were prepared. The palladium complex was used as catalyst for the hydrogenation of some nitroaromatics. The molar content of VPy units in VPy-co-NVP was determined as 31.25% by ¹H NMR. VPy–NVP–Pd can be easily resolved in ethanol forming a homogeneous catalytic hydrogenation system together with substrates. The optimum catalytic activity for hydrogenation of nitrobenzene appeared when VPy/Pd molar ratio was 2. The catalytic behavior of the catalyst was found to be greatly affected by the type and concentration of added alkalies. The highest hydrogenation rate for nitrobenzene was found in a 0.1 mol/l ethanol solution of potassium hydroxide. The catalytic stability was examined by using nitrobenzene and 4-nitroanisole as substrates.     

硅胶负载的双高分子-钯催化剂的研究——Ⅰ.硅胶负载的聚[4(2)-乙烯吡啶]-聚[苯乙烯-顺丁烯二酸]-钯催化剂的合成及其催化加氢性能

合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO_2和P2VP-PSM-Pd/SiO_2),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。     

硅胶负载的双高分子-钯催化剂的研究——Ⅰ.硅胶负载的聚[4(2)-乙烯吡啶]-聚[苯乙烯-顺丁烯二酸]-钯催化剂的合成及其催化加氢性能

 合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO₂和P2VP-PSM-Pd/SiO₂),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。     

无配体水介质中可循环聚乙烯吡咯烷酮负载钯催化Suzuki反应

In the absence of any ligand, a recoverable palladium（O） on poly（vinylpyrrolidone） （PVP） catalyzed Suzuki reaction of aryl iodide and bromide with potassium aryltrifluoroborate was developed. The reaction conditions involved the use of water as the solvent, potassium carbonate as the base, and PVP supported palladium metal colloids as the catalyst. The palladium metal could be recovered and recycled for eight consecutive trials without significant loss of its activity.     

Association of copolymers of methacrylic acid and 4-vinylpyridine in comparison with an intermacromolecular complex of poly(methacrylic acid) with poly(4-vinylpyridine)

Solution properties of copolymers [C(MA-Py)x] of methacrylic acid and 4-vinylpyridine and intermacromolecular complexes of poly(methacrylic acid) (PMAA) and poly(4-vinylpyridine) (PVP) in the presence or absence of a proton-accepting water-soluble polymer such as poly(ethylene glycol) (PEG) in water/methanol mixed solvent are studied by potentiometric titration, turbidity and viscosity methods. These copolymers behave like polyampholytes and their solubilities are strongly dependent with pH changes. The pH regions where they are precipitated around their isoelectric points are narrower than those of the intermacromolecular complex of PMAA with PVP. The polyampholyte can form an intermacromolecular complex with PEG in acidic solution but this complex is soluble in the medium.     

羊毛负载钯络合物的合成及其加氢催化作用

以天然生物高分子羊毛为载体制备了羊毛－钯络合物催化剂。用ＸＰＳ、ＩＲ方法对羊毛－钯络合物进行了初步表征。证明羊毛－钯络合物在常温常压下能够催化各种化合物，如硝基苯、苯甲醛、丙烯醇、丁烯睛、醋酸乙烯酯、苯乙烯和１－己烯的加氢，分别以大约１００％的收率得到了苯胺、苯甲醇、正丙醇、丙胺、醋酸乙酯，乙苯和己烷。对于用以往的催化剂较难加氢的各种脂肪醛，如丙醛、丁醛、戊醛和己醛，在常温常压下也能够进行催化加氢，分别以大约１００％的收率得到正丙醇、正丁醇、正戊醇和正己醇。这种催化剂稳定性也很高，长时间反应也能保持高活性，钯不脱落。     

聚乙烯吡咯烷酮对Pt/Ru双金属纳米簇的结构和催化性能影响

以乙二醇为还原剂,通过微波热辐射制备得到稳定的Pt/Ru双金属胶体纳米簇,各颗粒粒径在1~2nm范围。考察了聚合物聚乙烯吡咯烷酮（PVP）对Pt/Ru双金属纳米簇表面原子组成及催化性能的影响。结果表明,PVP与金属前体之间的不同相互作用影响Pt/Ru双金属纳米簇的形成。在Pt/Ru双金属纳米簇形成之前加入PVP,Pt原子更容易富集在双金属表面,有利于增加Pt在催化反应中的作用。在PVP稳定的Pt/Ru双金属纳米簇中,除了零价态的Pt、Ru单质外,还存在氧化态的Pt化合物,归因于PVP与Pt前体的相互作用。在环己烯加氢反应中,PVP-Pt/Ru双金属纳米簇显示出比单金属纳米簇更优越的催化性能。     

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.     

Synthesis and applications of polyvinylpyridine-grafted silica containing palladium nanoparticles as a new heterogeneous catalyst for heck and suzuki coupling reactions

A new catalytic system based on palladium nanoparticles supported on poly(4-vinylpyridine) (P4VPy)-grafted silica is introduced. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica. Onto this functionalized silica, 4-vinylpyridine monomer was polymerized by free radical polymerization. The P4VPy-grafted silica was characterized by FT-IR spectroscopy and the amount of (P4VPy) grafted was determind by thermogravimetric analysis (TGA). The complexation of (P4VPy)-grafted silica with Pd(Cl)₂ was carried out to obtain the heterogeneous catalytic system. Transmission electron microscopy images (TEM) showed that palladium dispersed through polymer surface in nanoparticle size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides, with olefinic compounds in Heck-Mizoraki, and with benzylbronic acid in Suzuki-Miyaura reactions. The use of aryl chlorides in cross-coupling reactions is usually hardly successful, but excellent results were gained in the presence of terta-n-butylammonium bromide (TBAB) as an additive. The turnover number (TON) of this catalyst reaches up to 9 × 10⁴ in these C-C bond forming reactions. High efficiency of the catalyst along with short reaction time, high yields, easy purification, recyclability, large scale synthesis and simple procedure are among the advantages of this catalytic system     

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.     

树枝状钯纳米结构的控制合成及硝基苯加氢反应的催化活性

以氯钯酸为前驱体, 苯甲醇为还原剂和溶剂, 十六烷基吡咯烷酮(PVP)为稳定剂, 在微波辐射下制备了分散均匀、形貌均一的树枝状钯纳米结构. 产物用透射电子显微镜(TEM), X射线粉末衍射(XRD), X射线光电子能谱(XPS)进行了表征, 表明所制备的Pd纳米颗粒呈树枝状, 形貌单一, 分散均匀, 是由许多近似圆形的小颗粒自组装而成的二级结构. 对树枝状钯催化硝基苯加氢反应进行探究, 表明树枝状钯的催化活性比市售的钯碳催化剂的催化活性高.     

Formation and Catalytic Functionality of Synthetic Polymer-Noble Metal Colloid

Colloidal dispersions of noble metals in synthetic polymers are prepared by reduction with alcohol. Reflux of a solution of rhodium(III) chloride and poly(vinyl alcohol) (PVA) in a methanol-water mixed solvent under argon or air for 4 hr gives a homogeneous solution of colloidal dispersion of rhodium (Rh-PVA-MeOH/H₂O). The particle size of metallic rhodium is distributed n a narrow range of 30-70 Å, and the average diameter is 40 A. The formation of colloidal rhodium proceeds through three steps: coordination of poly(vinyl alcohol) to rhodium(III) ion, reduction with methanol to form small particles (8 Å in diameter), and growth of the small particle to large particle (40 Å in diameter). Polyvinylpyrrolidone (PVP) and poly(methyl vinyl ether) (PMVE) can be used in place of poly(vinyl alcohol) and result in colloidal dispersions, respectively, similar to Rh-PVA-MeOH/H₂O. Colloidal dispersions in nonaqueous solvent can be prepared by using ethanol instead of methanol-water (Rh-PVP-EtOH) and by using methanol instead of methanol-water, with addition of small amount of methanol solution of sodium hydroxide (Rh-PVP-MeOH/NaOH). The average diameters of rhodium particles in Rh-PVP-EtOH and Rh-PVP-MeOH/NaOH are 22 and 9 Å, respectively. The colloidal dispersions of palladium, silver, osmium, iridium, platinum, and gold in aqueous or nonaqueous solvent are prepared by using polyvinylpyrrolidone. The colloidal dispersions are very stable even under air for 20 days. Those of rhodium, palladium, and platinum are effective catalysts for hydrogenation of olefins at 30°C under an atmospheric hydrogen pressure. The colloidal dispersion of palladium catalyzes highly selective hydrogenation of diene and dienoate to monoene and monoenoate, respectively.     

Selective hydrogenation by Pd nanoparticles embedded in polyelectrolyte multilayers

Alternating adsorption of poly(acrylic acid) and a polyethylenimine-Pd(II) complex on alumina and subsequent reduction of Pd(II) by NaBH4 yield catalytic Pd nanoparticles embedded in multilayer polyelectrolyte films. The polyelectrolytes limit aggregation of the particles and impart catalytic selectivity in the hydrogenation of alpha-substituted unsaturated alcohols by restricting access to catalytic sites. Hydrogenation of allyl alcohol by encapsulated Pd(0) nanoparticles can occur as much as 24-fold faster than hydrogenation of 3-methyl-1-penten-3-ol. Additionally, the nanoparticle/polyelectrolyte system suppresses unwanted substrate isomerization, when compared to a commercial palladium catalyst. Selective diffusion through poly(acrylic acid)/polyethlyenimine membranes suggests that hydrogenation selectivities are due to different rates of diffusion to nanoparticle catalysts. First-order kinetics are also consistent with a diffusion-limited mechanism. Further exploitation of the versatility of polyelectrolyte films should increase selectivity in hydrogenation as well as other reactions.     

Catalytic square-wave voltammetric detection of DNA with reversible metallopolymer-coated electrodes

Pyrolytic graphite electrodes with adsorbed poly(4-vinylpyridine) (PVP) with attached Ru(bpy)₂²⁺ gave reversible voltammetry, facilitating reusable DNA sensors. These electrodes gave catalytic voltammetric responses to poly(guanylic) acid and DNA at about 0.75 V vs SCE caused by catalytic oxidation of guanine moieties in these polynucleotides. ss-DNA gave twice the square-wave voltammetric catalytic current compared to an equivalent amount of ds-DNA, suggesting that the [Ru(bpy)₂–PVP]²⁺ polymer may be useful for detection of DNA hybridization and damage.     

聚4-乙烯基吡啶/SiO~2纳米杂化材料负载茂钛催化剂的制备 及苯乙烯聚合

以聚4-乙烯基吡啶(PVP)为有机组分,正硅酸乙酯(TEOS)为无机组分,利用sol-gel方法制得PVP/SiO~2纳米杂化材料,以此为载体制备了杂化材料负载单茂钛催化剂。利用XPS和IR分析了载体与CpTiCl~3的结合方式,确认对苯乙烯聚合有两种活性中心,苯乙烯聚合结果表明在50℃左右间规度达到最大;在70℃,n(Al)/n(Ti)=1500时活性最高可达1.09×10^6gPS/(molTi·h),GPC结果表明产物分子量分布呈双峰分布。     

Effect of support on activity of palladium catalysts in nitrobenzene hydrogenation

The effect of two types of catalysts on the activity of the catalytic hydrogenation of nitrobenzene was studied. Catalysts were prepared by the surface deposition of palladium hydroxide with a simultaneous reduction with formaldehyde in a basic environment and were characterised by X-ray powder diffraction, transmission electron microscopy, adsorption-desorption, and catalytic tests — hydrogenation of nitrobenzene in methanol. The influence of the supports’ (activated carbon and a mixture of activated carbon and multi-walled carbon nanotubes) surface area is discussed. Despite having a size comparable (4–5 nm) to crystallites of metallic palladium, the catalyst prepared on a mixture of activated carbon and nanotubes (Pd/C/CNT) was significantly less active than the catalyst prepared on pure activated carbon (Pd/C); the rate of this reaction was approximately 30 % lower than the initial reaction rate. This feature could be attributed to the lower specific surface area of the Pd/C/CNT (531 m² g^?1) in comparison with the Pd/C (692 m² g^?1).     

Hydrogenation of nitroaromatics by polymer-anchored bimetallic palladium-ruthenium and palladium-platinum catalysts under mild conditions

Polymer-achored monometallic palladium catalyst PVP-PdCl₂ (PVP = poly(N-vinyl-2-pyrrolidone)) exhibits very high activity for the hydrogenation of p-chloronitrobenzene (CNB) to aniline (AN) in the presence of base at 65°C and atmospheric pressure. In this case, the substrate is rapidly hydrodechlorinated to nitrobenzene (NB) which is then reduced to AN. Using the polymer-anchored bimetallic palladium-ruthenium catalyst, PVP-PdCl₂-RuCl₃, and in the presence of 1.0 mol% of sodium acetate, a strong synergic effect gives rise to a remarkable increase of the selectivity for p-chloroaniline (CAN) and the maximum selectivity of CAN is up to 94%. For the hydrogenation of the non-halo-substituted nitroaromatics to the corresponding aromatic amines, the monometallic PVP-PdCl₂ catalyst only shows mild or poor activity, but the colloidal polymer-anchored bimetallic palladium-platinum catalyst, PVP-Pd-1/4Pt, exhibits very high activity and selectivity.     

几种聚合物改性硅胶对苯胺的吸附性能研究

研究了聚乙烯基吡啶改性硅胶(PVP/SiO2)、聚苯乙烯改性硅胶(PS/SiO2)、胺化聚苯乙烯改性硅胶(PS-NH2/SiO2)等3种有机-无机复合材料吸附剂对苯胺的吸附行为。吸附动力学研究表明,3种吸附剂对苯胺的吸附均符合准二级动力学方程。对其粒内扩散模型模拟的结果表明,在3种吸附过程中液膜扩散为主要速率控制步骤。用Langmuir等温吸附方程式和Freundlich等温吸附方程式对其吸附等温线进行了拟合,结果表明,PVP/SiO2、PS/SiO2对苯胺的吸附符合Freundlich等温吸附方程式。     

膦化聚2,6—二甲基1,4—苯醚负载钯催化剂的表征及其催化性能

报道了四种不同P/Pd摩尔比的膦化聚2,6-二甲基1,4-苯醚负载把催化剂的加氢和异构化性能;通过XPS、电镜和远红外对催化剂进行了表征;并考察了溶剂和温度对催化剂活性的影响.