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1.
β环糊精(β-CD)具有特殊的空腔结构,将β-CD修饰的多壁碳纳米管(MWCNT)涂在钛基底上,采用电沉积的方法在修饰的钛基底上沉积纳米PdNi催化剂。SEM结果表明,PdNi纳米颗粒在β-CD/MWCNT修饰的钛片上有较好的分散度,粒径为90~130 nm。在碱性溶液中,测试了PdNi-β-CD/MWCNT/Ti电极分别对丙醇和丁醇不同异构体氧化的电催化活性;通过计算与-OH相连的碳原子上的Muliken净电荷,分析不同异构体的氧化机理。结果表明,不同异构体的氧化活性不同,PdNi-β-CD/MWCNT/Ti电极对正丙醇和正丁醇的氧化活性明显高于其异构体,-OH所在碳原子上的Muliken 净电荷越小,醇类分子越容易被氧化。  相似文献   

2.
采用硼氢化钠还原的方法合成了碳纳米管负载的钯基纳米催化剂(Pd/CNT,Pd7Ag3/CNT,Pd7Sn2/CNT,Pd7Ag1Sn2/CNT,Pd7Ag2Sn2/CNT和Pd7Ag3Sn2/CNT)。通过XRD,TEM和XPS对其进行了表征,结果表明,相比Pd/CNT和Pd-Ag(或Pd-Sn)催化剂的纳米颗粒,Pd-Ag-Sn催化剂展现出了更小的平均颗粒尺寸(2.3 nm)。此外,还通过循环伏安(CV)和计时电流法(CA)测试了这些催化剂对甲酸氧化的电活性,在酸碱介质中,Pd-Ag-Sn/CNT对甲酸氧化都表现出了更高的电流密度。其中,Pd7Ag2Sn2/CNT催化剂在酸碱介质中的电流密度分别是108.8和211.3 mA·cm-2,相应的Pd质量电流密度高达1 364和2 640 mA·mg-1,远远高于商业Pd/C,表明Pd-Ag-Sn/CNT催化剂对甲酸氧化表现出了极好的电催化活性。  相似文献   

3.
Tuning the electronic property of a transition metal plays an important role in the selective catalysis. Herein, the control synthesis of (PdxNiy)‐P nanoparticles is reported. The binding energy of Pd3d5/2 as a function of x/y ratio is well tunable from 335.3 to 335.9 eV. The composition‐induced electronic modulation was correlated with the selective catalysis of (PdxNiy)‐P in the reduction of halogenated nitrobenzenes. The electro‐deficiency of Pd helped to improve the selectivity. The amorphous (Pd38Ni26)P36/C performed an exceptional selectivity in comparison with other related (Pd‐Ni)‐P/C, Pd38Ni26/C, and Pd/C. Various halogenated nitrobenzenes (chlorides, bromides, and iodide) were tolerant and the corresponding halogenated anilines were obtained in high yields. This work provides some clues for the rational design of bimetallic phosphides with covalent interactions to boost the catalysis.  相似文献   

4.
Multi‐walled carbon nanotubes (MWCNTs) decorated with PdxCoy (the nominal atomic ratios of Pd to Co were 3:1, 3:1.5, 3:2, 3:3, respectively) nanoparticles (denoted as PdxCoy/MWCNTs ) were fabricated by a simple pyrolysis process, in which room temperature ionic liquids (RTILs) of butyl‐3‐methylimidazolium hexafluorophosphate (denoted as [BMIM]PF6) was used as the solvent. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were all used to characterize the PdxCoy/MWCNTs catalysts, showing that the PdxCoy particles were dispersed on the surface of the MWCNTs with an average particle size of ~25.0 nm. The electro‐catalytic activity of the PdxCoy/MWCNTs catalysts toward ethanol oxidation reaction (EOR) was examined by cyclic voltammetry (CV). It was revealed that the onset potential was ~90 mV lower and the peak current was about four times higher for ethanol oxidation for Pd3Co1.5/MWCNTs compared to those of Pd3Co1/MWCNTs. The possible catalysis mechanisms of the Pd3Co1.5/MWCNTs toward EOR were also discussed.  相似文献   

5.
Ignition delay times of sec‐, iso‐, and tert‐butanol were measured behind reflected shock waves using both conventional operation and a new constrained‐reaction‐volume (CRV) strategy. This CRV filling method constrains the volume of reactive gases, thereby producing near‐constant‐pressure test conditions for reflected shock measurements. The initial reflected shock conditions cover temperatures ranging from 828 to 1095 K, pressures near 20 atm and an equivalence ratio of 1.0 in air mixtures. Additional data were also collected at 30 atm and at φ = 0.5 for iso‐butanol/O2/N2 mixtures. At 20 atm and φ = 1.0, the ignition delay time increases for the isomers in the following order: n‐butanol, iso‐butanol and sec‐butanol, and tert‐butanol. Modeling of all collected data using the Vasu and Sarathy (Energy Fuel 2013, 27, 7072–7080) mechanism showed overall good agreement with the experimental data.  相似文献   

6.
Chemoselective reduction of the C=C bond in a variety of α,β‐unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2: 1) nano‐Pd on a metal–organic framework (MOF: Pd0‐MIL‐101‐NH2(Cr)), 2) nano‐Pd on a siliceous mesocellular foam (MCF: Pd0‐AmP‐MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd0‐MIL‐101‐NH2(Cr) and Pd0‐AmP‐MCF were capable of delivering the desired products in very short reaction times (10–90 min) with low loadings of Pd (0.5–1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.  相似文献   

7.
PAL  Amalendu GABA  Rekha 《中国化学》2007,25(12):1781-1789
Excess molar volumes Vm^E and kinematic viscosities v have been measured as a function of composition for binary mixtures of propylene glycol monomethyl ether (1-methoxy-2-propanol), MeOCH2CH(OH)Me, propylene glycol monoethyl ether (1-ethoxy-2-propanol), EtOCH2CH(OH)Me, propylene glycol monopropyl ether (1-propoxy-2-propanol), PrOCH2CH(OH)Me, propylene glycol monobutyl ether (1-butoxy-2-propanol), BuOCH2CH(OH)Me, and propylene glycol tert-butyl ether (1-tert-butoxy-2-propanol), t-BuOCH2CH(OH)Me with 1-butanol, and 2-butanol, at 298.15 K and atmospheric pressure. The excess molar volumes are negative across the entire range of composition for all the systems with 1-butanol, and positive for the systems 2-butanol+ 1-methoxy-2-propanol, and +1-propoxy-2-propanol, negative for the systems 2-butanol+1-butoxy-2-propanol, and change sign for the systems 2-butanol+ 1-ethoxy-2-propanol, and + 1-tert-butoxy-2-propanol. From the experimental data, the deviation in dynamic viscosity η from ∑χiηi has been calculated. Both excess molar volumes and viscosity deviations have been correlated using a Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors.  相似文献   

8.
The atom‐transfer carbonylation reaction of various alkyl iodides thereby leading to carboxylic acid esters was effectively accelerated by the addition of transition‐metal catalysts under photoirradiation conditions. By using a combined Pd/ reaction system, vicinal C‐functionalization of alkenes was attained in which α‐substituted iodoalkanes, alkenes, carbon monoxide, and alcohols were coupled to give functionalized esters. When alkenyl alcohols were used as acceptor alkenes, three‐component coupling reactions, which were accompanied by intramolecular esterification, proceeded to give lactones. Pd‐dimer complex [Pd2(CNMe)6][PF6]2, which is known to undergo homolysis under photoirradiation conditions, worked quite well as a catalyst in these three‐ or four‐component coupling reactions. In this metal/radical hybrid system, both Pd radicals and acyl radicals are key players and a stereochemical study confirmed the carbonylation step proceeded through a radical carbonylation mechanism.  相似文献   

9.
Chiral secondary alcohols are very important building blocks and valuable synthetic intermediates both in organic synthesis and in the pharmaceutical industry for producing biologically active complex molecules. A series of new chiral Ru–phosphinite complexes ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) were prepared from chiral C2‐symmetric ferrocenyl phosphinites and corresponding chloro complex, [Ru(η6p‐cymene)(μ‐Cl)Cl]2. The complexes were characterized using conventional spectroscopic methods. The binuclear complexes were tested as pre‐catalysts and were found to be good pre‐catalysts for the asymmetric transfer hydrogenation of substituted acetophenones in basic 2‐propanol at 82°C, providing the corresponding optically active alcohols with almost quantitative conversion and modest to high enantioselectivities (46–97%). Amongst the all complexes, complex 6 gave the highest ee of 97% in the reduction of 2‐methoxyacetophenone to (S)‐1‐(2‐methoxyphenyl)ethanol at 82°C. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

10.
2‐Phenylquinolines, 2‐phenyl‐3‐methyl‐quinolines, and 2‐phenyl‐3‐ethylquinolines were synthesized in high yields (78–90%) by the reaction of aniline, benzylamine, aliphatic alcohols (ethanol, n‐propanol, n‐butanol), and CCl4 catalyzed by FeCl3·6H2O in tetrachloromethane.  相似文献   

11.
Phases with with a NiAs-based structure have been studied in Au-Pd-Sn and Cu-Pd-Sn systems at 500°C using powder X-ray diffraction, X-ray structure analysis, and energy-dispersive X-ray microanalysis. In the Cu-Pd-Sn system, binary phases γ-Pd2Sn and Cu6Sn5 both having the Ni2In structure form a phase region (Pd,Cu)2 − x Sn, which preserves the Ni2In structure and is confined at 500°C by an L + (Pd,Cu)2 − x Sn + ɛ-Cu3Sn three-phase region. In the Au-Pd-Sn system, the δ-AuSn phase with the NiAs structure and γ-Pd2Sn with the Ni2In structure form a single phase region (Pd,Au)2 − x Sn, which is bounded at 500°C by an L + (Pd,Au)2 − x Sn two-phase region; the structure of the ternary phase changes from Ni2In with incompletely filled trigonal-prismatic interstices to NiAs. The Pd20Sn13 phase, which crystallizes in the GaGe2Ni4 type structure, penetrates into both ternary systems up to ∼5 at % of the third component. The solubilities of copper and gold in PdSn and Pd2Sn phases, which have structures based on orthorhombically distorted NiAs and Ni2In lattices, respectively, do not exceed 2 at %.  相似文献   

12.
《中国化学》2017,35(9):1405-1410
Pd and Pdx Ni nanoparticles have been supported on reduced graphene oxide (Pd/rGO and Pdx Ni/rGO ) by using the microwave‐assisted heating method in glycol. The morphology, composition and electrochemical performance have been characterized by TEM , XRD , XPS and electrochemical methods. The XRD and XPS results show that there are no PdNi alloy particles formed in Pdx Ni/rGO and the composites exist mostly in the form of Pd0 and NiOOH species. The electrochemical results reveal that Pdx Ni/rGO synthesized from the feeding source of Pd and Ni with an atomic ratio of 4∶1 exhibits higher activity, better stability and smaller electron transfer resistance toward formic acid electro‐oxidation compared with commercial Pd/C, Pd/rGO and other Pdx Ni/rGO samples. The excellent electrocatalytic performance indicates that the addition of appropriate amount of Ni can greatly enhance the activity and stability of Pd catalysts for formic acid oxidation.  相似文献   

13.
The vapor absorbency of the series of alcohols methanol, ethanol, 1‐propanol, 1‐butanol, and 1‐pentanol was characterized on the single‐crystal adsorbents [MII2(bza)4(pyz)]n (bza=benzoate, pyz=pyrazine, M=Rh ( 1 ), Cu ( 2 )). The crystal structures of all the alcohol inclusions were determined by single‐crystal X‐ray crystallography at 90 K. The crystal‐phase transition induced by guest adsorption occurred in the inclusion crystals except for 1‐propanol. A hydrogen‐bonded dimer of adsorbed alcohol was found in the methanol‐ and ethanol‐inclusion crystals, which is similar to a previous observation in 2 ?2EtOH (S. Takamizawa, T. Saito, T. Akatsuka, E. Nakata, Inorg. Chem. 2005 , 44, 1421–1424). In contrast, an isolated monomer was present in the channel for 1‐propanol, 1‐butanol, and 1‐pentanol inclusions. All adsorbed alcohols were stabilized by hydrophilic and/or hydrophobic interactions between host and guest. From the combined results of microscopic determination (crystal structure) and macroscopic observation (gas‐adsorption property), the observed transition induced by gas adsorption is explained by stepwise inclusion into the individual cavities, which is called the “step‐loading effect.” Alcohol/water separation was attempted by a pervaporation technique with microcrystals of 2 dispersed in a poly(dimethylsiloxane) membrane. In the alcohol/water separation, the membrane showed effective separation ability and gave separation factors (alcohol/water) of 5.6 and 4.7 for methanol and ethanol at room temperature, respectively.  相似文献   

14.
Monodisperse bimetallic Pd–Cu nanoparticles with controllable size and composition were synthesized by a one‐step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd85–Cu15, Pd56–Cu44, and Pd39–Cu61. The nanoparticles were separated from the solution mixture by extraction with non‐polar solvents, such as n‐hexane. Monodisperse bimetallic Pd–Cu nanoparticles with narrow size‐distribution were obtained without the need for a size‐selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as‐prepared nanoparticles were loaded onto a Vulcan XC‐72 carbon support. Supported bimetallic Pd–Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd–Cu catalyst that contained 15 % Cu, the activity was even comparable to the state‐of‐the‐art commercially available Pt/C catalysts. A STEM‐HAADF study indicated that the formation of random solid‐solution alloy structures in the bimetallic Pd85–Cu15/C catalysts played a key role in improving the electrochemical activity.  相似文献   

15.
Halfantiperovskites II: on the Crystal Structure of Pd3Bi2S2 The crystallographic structure of Pd3Bi2S2 was determined from x‐ray diffraction data and compared to parkerite (Ni3Bi2S2), shandite (Ni3Pb2S2), and a high pressure form of laflammeite (Pd3Pb2S2). For Pd3Bi2S2 the structure type of corderoite, Hg3S2Cl2 (I213) was found that represents a cubic variant (a = 8,3097(9) Å) of the parkerite structure. It turns out to be a structural antitype of the low temperature cubic modification of K2Sn2O3, analogously to the previously investigated type‐antitype relation of shandit to high‐temperature K2Sn2O3. The crystal structures are derived from perovskites ABO3 and antiperovskites M3AX with only half of the O‐ and M‐sites being occupied. The M = Ni, Pd site ordering in shandite and parkerite type compounds is discussed in terms of ordered half antiperovskite (HAP) structures M3/2AS (A = Bi, Pb). The electronic band structure of Pd3Bi2S2 is calculated within the framework of density functional theory. The compound is found to behave metallic while K2Sn2O3 and corderoite are semiconductors. The bonding is analysed in terms of covalently bond [Pd3S2]δ? networks as proposed for [Sn2O3]2? and [Hg3S2]2+.  相似文献   

16.
在乙二醇和水混合溶剂中,采用硼氢化钠还原的方法制备了多壁碳纳米管(MWCNT)负载的Pd和Pd-Ag纳米颗粒催化剂;在碱性介质中,用循环伏安法测试了这些催化剂对乙醇、正丙醇和异丙醇的电氧化性能。结果表明,Pd和Pd-Ag纳米颗粒均匀地分散在MWCNT表面;Pd/MWCNT、Pd4Ag1/MWCNT、Pd2Ag1/MWCNT和Pd1Ag1/MWCNT催化剂上金属颗粒的平均粒径分别为7、4、7和11 nm。相比乙醇和异丙醇,所制备的催化剂对正丙醇的氧化表现出较大的电流密度。与Pd/MWCNT催化剂相比,双金属PdnAg1/MWCNT(n=4、2、1)催化剂,尤其是Pd4Ag1/MWCNT上的电流密度更大,表明Ag的加入提高了Pd催化剂对醇氧化的电化学活性,其原因是因为醇氧化过程所产生的中间体物种在双金属Pd-Ag/MWCNT催化剂上的吸附力有所减弱。  相似文献   

17.
A novel azo dye ligand formed by the coupling of L‐histidine with 2‐hydroxy‐1‐naphthaldyhide(H2L) and its Ru3+, Pd2+ and Ni2+ nano‐sized complexes were obtained and described by elemental analysis, TGA, magnetic moment measurements, molar conductance, UV‐Vis, ESR, X‐ray powder diffraction, IR, SEM, TEM, 1H‐nmr, 13C‐nmr, and EI‐mass spectral studies. The analytical results and spectral studies detected that the H2L ligand acts as dibasic tetradentate via aldehyde oxygen, azo nitrogen and deprotonated OH and COOH groups. The data showed the paramagnetic Ru3+ complex has octahedral geometry while Pd2+ and Ni2+ have square planar structures. The molar conductance measurements display all complexes are nonelectrolyte. The crystallinity, morphology and average particle size data revealed the prepared complexes were formed in the Nano scale. The average particle size as calculated from TEM images are found to be 13.72, 64.52 and 115.00 nm for Ru3+, Pd2+ and Ni2+ chelates, respectively. The catalytic activities of these compounds were checked for oxidation of 2‐amino phenol to 2‐amino‐3H phenoxazine‐3‐one as heterogeneous catalysts. A 96, 31 and 21% catalytic conversion are found when using Ru(III), Pd(II) and Ni(II) complexes respectively.  相似文献   

18.
The supported bimetallic Fe—Pd/SiO2 catalysts with the different Fe (0.025—8 mass.%) and Pd (0.05—3.2 mass.%) loadings were synthesized by the incipient wetness impregnation of support. The samples were heat-treated under different conditions (calcination in air at 240—350 °C or reduction in an H2 flow at 400 °C). The X-ray phase analysis revealed the formation of Pd0, α-Fe2O3 and Fe3O4 phases after calcination of the samples at 240—260 °C. The reduction of the calcined Fe—Pd samples in an H2 flow at 400 °C enables the formation of Fe0 nanoparticles of size 17—20 nm. The synthesized catalytic systems were studied in the selective hydrogenation of phenylacetylene at room temperature and atmospheric pressure in a solvent (ethanol, propanol). The catalytic properties of the Fe—Pd catalysts depend on the nature of solvent, catalyst composition, and thermal treatment conditions. The application of the Fe—Pd bimetallic catalysts with a low Pd loading of 0.05—0.1 mass.% made it possible to reach the high activity and selectivity to styrene (91%) at the complete conversion of phenylacetylene.  相似文献   

19.
以甲酸为燃料、 Fe3+为氧化剂组成了一种新型的甲酸/铁离子燃料电池, 阳极催化剂为多壁碳纳米管(MWCNT)或β-环糊精修饰的MWCNT(β-CD-MWCNT)负载的金属钯或钯锡纳米颗粒: PdSn/MWCNT, Pd/β-CD-MWCNT和PdSn/β-CD-MWCNT. 运用循环伏安(CV)和计时电流(CA)等技术研究了各催化剂在碱性条件下对甲酸氧化反应的电催化活性. 结果表明, 加入适量的金属锡能促进钯对甲酸的电催化氧化, 甲酸氧化电位提前, 电流密度增加; 环糊精的改性对催化剂电催化活性有一定提升. 将上述催化剂制成电池阳极片, 碳粉制成电极阴极片, 组成甲酸/铁离子燃料电池并测试其放电性能. 结果表明, 电池的开路电压在0.981.20 V之间; 以PdSn/β-CD-MWCNT为阳极时, 其最大放电电流密度达50 mA/cm2, 最大功率密度达12.6 mW/cm2, 远优于以Pd/C为阳极的电池性能.  相似文献   

20.
The syntheses and characterisation of a series of chiral and achiral 2‐(aminophenyl)‐2‐oxazolines and some related compounds is reported. All of the derivatives have been produced by a one‐step procedure involving the treatment of isatoic anhydride (i.e. [2H]‐3, 1‐benzoxazine‐[1H‐2,4‐dione: 1 ) or its 5‐chloro analogue with a slight excess of appropriate amino‐alcohols. In most cases, anhydrous ZnCl2 is shown to be an effective Lewis acid catalyst for this reaction at reflux temperature in high boiling aromatic solvents (PhCl or PhMe). Oxazolines have been readily formed using rac‐2‐amino‐1‐butanol, (S)‐phenylglycinol, 2‐methyl‐2‐amino‐1‐propanol and (1S,2R) or (IR,2S)‐cis‐ 1 ‐amino‐2‐indanol; yields range from 85% to 22%. The use of aminoalcohols such as 2‐ethanolamine, (±)‐2‐amino‐1‐phenyl‐1‐propanol or 3‐amino‐1‐propanol (to give the corresponding 4,5‐dihydro‐1,3‐oxazine) results in poor yields. The use of other Lewis acid catalysts (silicic acid, Cd(acac)2·2H2O, CuCl2·2H2O, InCl3) or higher temperatures did not improve the yields with these latter two substrates. Benzoxazoles and N‐substituted benzoxazoles can also be obtained in reasonable yields from 1 using 2‐aminophenol (36%) or 2‐amino‐3‐hydroxypyridine (45%).  相似文献   

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