Pd/c-Si界面反应研究

于2010-11-23批量导入

Pd/C-catalyzed hydrodehalogenation of aromatic halides in aqueous solutions at room temperature under normal pressure

The hydrodehalogenation of aromatic halides, catalyzed by Pd/C in aqueous solutions, yields arenes in short reaction times at room temperature under normal pressure. The nature of the solvents has an important influence on the reaction rates and the activity of the catalyst. The catalyst shows the highest activity in water. In the hydrodechlorination of 4-chlorohypnone, it was in water that C-Cl bond was easier to be hydrogenated, and in isopropanol that C=O was easier to be hydrogenated. (C) 2004 Elsevier B.V. All rights reserved.

固相反应法制备的Pd/C催化剂对甲酸氧化的电催化活性

催化剂中Pd粒子的粒径和相对结晶度对甲酸氧化峰峰电位基本没有影响.但在Pd/C-1和Pd/C-2催化剂电极上主要氧化峰峰电流分别为17·1和6·1mA/cm2,表明Pd/C-1催化剂对甲酸氧化的电催化活性要高于Pd/C-2催化剂,这是由于Pd/C-1催化剂中Pd粒子的平均粒径和相对结晶度比Pd/C-2催化剂的小而引起的.图3为Pd/C-1和Pd/C-2催化剂电极在0·5mol/LH2SO4+0·5mol/L HCOOH溶液中,电位恒定在0·1V时的计时电流曲线.由图可见,在Pd/C-1催化剂电极上(图3,曲线a),当电位恒定在0·1V下扫描1000s时,电流密度为2·35mA/c

Preparation of Pd/C catalyst for formic acid oxidation using a novel colloid method

A novel colloid method using (WO3)(n)center dot xH(2)O as colloidal source was developed to prepare Pd/C catalyst for formic acid oxidation. Transmission electron microscopy image shows that the Pd/C nanoparticles have an average size of 3.3 nm and a narrow size distribution. Electrochemical measurements indicate that the Pd/C catalyst exhibits significantly high electrochemical active surface area and high catalytic activity with good stability for formic acid oxidation compared with that prepared by common method.

Synthesis of Pd/C catalysts with designed lattice constants for the electro-oxidation of formic acid

Pd/C catalysts with designed lattice constants were synthesized for the electro-oxidation of formic acid. By changing the solvents in the preparation procedure, it was demonstrated that the different lattice constants of Pd crystallites could be controlled as desired. The varied lattice constants may be attributed to the difference in the interactions between solvents and PdCl2. it was found that the lattice constant had an obvious effect on the electro-catalytic performance of Pd.

Influence of compressed carbon dioxide on hydrogenation reactions in cyclohexane with a Pd/C catalyst

The potential of CO2-expanded liquid media for chemical reactions has been examined in this work, using cyclohexane as a solvent and Pd/C as a heterogeneous catalyst for hydrogenation of styrene, citral, and nitrobenzene with H-2. The rate of hydrogenation reactions is increased, and the product selectivity is altered in the CO2-expanded cyclohexane phase. In the hydrogenation of citral, the selectivity to citronellal decreases with CO2 pressure, which changes from similar to 80% in the neat cyclohexane to similar to 65% at 16 MPa.

Hydrogenation of o-chloronitrobenzene to o-chloroaniline over Pd/C in supercritical carbon dioxide

Hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) with Pd/C has been investigated in supercritical carbon dioxide (scCO(2)) at 308 K. The influences of several parameters such as CO2, H-2 pressures, Fd metal particle size and reaction time have been discussed. CO2 pressure presented markedly effects on the reaction rate and product selectivity under the reaction conditions used, the selectivity to o-CAN at CO2 pressure from 8 to 13 MPa (supercritical region) was larger than that at CO2 pressure below 6 MPa (subcritical region).

The size-controlled synthesis of Pd/C catalysts by different solvents for formic acid electrooxidation

The size-controlled synthesis of Pd/C catalyst for formic acid electrooxidation is reported in this study. By using alcohol solvents with different chain length in the impregnation method, the sizes of Pd nanoparticles can be facilely tuned; this is attributed to the different viscosities of the solvents. The results show that a desired Pd/C catalyst with an average size of about 3 nm and a narrow size distribution is obtained when the solvent is n-butanol. The catalyst exhibits large electrochemically active surface area and high catalytic activity for formic acid electrooxidation.

Influence of metal particle size on the hydrogenation of maleic anhydride over Pd/C catalysts in scCO(2)

Hydrogenation of maleic anhydride (MAH) with Pd/C catalysts in supercritical carbon dioxide (scCO(2)) was investigated. The selectivity for gamma-butyrolactone (GBL) reached 97.3% in scCO(2) at 100% conversion of MAH, which was notably higher than that of 77.4% obtained in organic solvent of ethylene glycol dimethyl ether (EGDME). The particle size of Pd exhibited large influence on the reaction rate and selectivity of GBL. Higher selectivity of GBL was obtained with Pd/C catalyst of smaller Pd particle size, and the rate of GBL selectivity increase as a function of CO2 pressure was found to be significantly correlated with Pd particle size.

有机溶胶法制备直接甲酸燃料电池用Pd/C阳极催化剂

采用改进的有机溶胶法制备了用于直接甲酸燃料电池(DFAFC)中甲酸氧化的炭载Pd(Pd/C)催化剂。制备Pd/C催化剂时,以乙醇作溶剂,SnCl2作还原剂。控制溶剂的蒸发温度就能控制Pd/C催化剂中Pd粒子的平均粒径和相对结晶度。溶剂蒸发温度与Pd/C催化剂中Pd粒子的平均粒径和相对结晶度不成正比关系。在选择合适的溶剂蒸发温度时,能制得Pd粒子的平均粒径至6.5 nm和相对结晶度至2.85的Pd/C催化剂。比较了具有不同Pd粒子的平均粒径和相对结晶度的Pd/C催化剂对甲酸氧化的电催化性能。结果发现,Pd粒子的平均粒径小和相对结晶度低的Pd/C催化剂对甲酸氧化有好的电催化性能。

Pd/C催化剂在处理NO反应中的催化行为

研究了不同活性炭负载的Pd催化剂在NO＋CO反应中和单独处理NO时的催化行为．结果表明，Pd的引入可大大提高催化活性，且活性与Pd含量呈顺变关系．不同的载体对催化剂活性有很大影响．在NO＋CO反应中，由煤质炭为载体制得的催化剂活性很高，在低于550K时NO即可达到100%转化，而在单独NO时，由山桃核炭制得的催化剂有较高的活性，在低于650K时NO可达到100%转化．催化剂活性的差异与活性炭表面性质有关．当反应体系中有还原物质CO存在时，活性炭作为载体，Pd在其上的分散对活性有重要影响；当体系中没有还原物质时，活性炭作为还原剂参与反应，这时活性炭本身的性质变得十分重要.

Pd nanoparticles supported on WO3/C hybrid material as catalyst for oxygen reduction reaction

Pd nanoparticles supported on WO3/C hybrid material have been developed as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells. The resultant Pd-WO3/C catalyst has an ORR activity comparable to the commercial Pt/C catalyst and a higher activity than the Pd/C catalyst prepared with the same method. Based on the physical and electrochemical characterizations, the improvement in the catalytic performance may be attributed to the small particle sizes and uniform dispersion of Pd on the WO3/C, the strong interaction between Pd and WO3 and the formation of hydrogen tungsten bronze which effectively promote the direct 4-electron pathway of the ORR at Pd.

Kinetic study of formic acid oxidation on carbon supported Pd electrocatalyst

The oxidation of formic acid at the Pd/C catalyst electrode is a completely irreversible kinetic process with the reaction order of 1.0. The oxidation rate of formic acid is increased with increasing the concentration of formic acid and is decreased with increasing H+ concentration. The apparent negative reaction order with respect to H+ is about -0.18 or -0.04 in H2SO4 or HClO4 solution respectively, because bisulfate anions would inhibit formic acid oxidation at some extent. The kinetic parameters, charge transfer coefficient and the diffusion coefficient of formic acid were obtained under the quasi steady-state conditions.

A carbon-supported Pd-P catalyst as the anodic catalyst in a direct formic acid fuel cell

In this paper, it is reported for the first time that a carbon-supported Pd-P (Pd-P/C) catalyst for the anodic catalyst in the direct formic acid fuel cell (DFAFC) can be prepared. The Pd-P/C catalyst shows that its electrocatalytic activity and especially its stability for the oxidation of formic acid are much higher than that of a Pd/C catalyst. Therefore, the Pd-P/C catalyst may have practical applications in DFAFCs.