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971.
Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene
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Pd/C catalysts were prepared by deposited Pd nanoparticles (NPs) on different carbon supports including activated carbon (AC), graphite oxide (GO), and reduced graphite oxide (rGO) using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction. 相似文献
972.
水热合成MIL-101,过量浸渍法吸附Pd(OAc)_2,原位还原Pd~(2+)制得Pd/MIL-101催化剂.采用XRD、XPS、SEM、ICP、HRTEM和N_2吸/脱附实验对其结构进行表征,催化剂Pd纳米粒子尺寸在1.5~2.5 nm之间,含量为1.5%.催化实验表明,Pd/MIL-101能高效催化吲哚C_2位芳基化,对于活性较差的溴代芳烃,也能得到中等以上的收率,催化剂循环5次后仍能保持较高的反应活性,发展了吲哚C_2位衍生物的简单、高效的合成方法. 相似文献
973.
974.
采用密度泛函理论研究了Pd(111)面和Ru-Pd(111)面的性质及对糠醛的吸附.原子尺寸因素、相对键长、形成能及d带中心等计算结果表明,Ru-Pd(111)面比Pd(111)面稳定且活性强,Ru的修饰优化了Pd(111)面的几何构型.糠醛在Pd(111)面及Ru-Pd(111)面的初始吸附位分别为P(top-bridge)位及P(Pd-fcc-Ru-fcc)位时,吸附能最大,吸附构型最稳定.由电荷布局和差分电荷密度可得,糠醛在Ru-Pd(111)面上电荷转移数更多,相互作用更强烈,因此吸附能更大.分析态密度可知,产生吸附的主要原因是位于-7.34 eV处至费米能级处的p,d轨道杂化.吸附于Ru-Pd(111)面后糠醛分子的p轨道向低能级偏移程度更明显,使Ru改性后的Pd催化剂具有更好的催化活性. 相似文献
975.
采用液相还原法,以Na_2PdCl_4为钯源,PVP为还原剂和分散剂,碘离子作为晶面选择吸附剂和配位剂,硝酸根离子作为氧化蚀刻剂,水为溶剂,在n(Na_2PdCl_4)∶n(PVP)∶n(KI)∶n(NaNO_3)=1∶35∶10∶9和pH=11条件下,合成了形貌规整的纯度大于99%的钯三角双锥单孪晶.碘离子在合成体系中主要通过改变钯前驱体还原速率来影响钯晶种的生长转化和产物的形貌,对氧化蚀刻作用的影响在较高pH值下并不明显.钾离子和钠离子比例的变化显著影响了产物的形貌组成,此阳离子效应可归因于反应体系在钠离子存在时较钾离子存在时表现出更快的钯前驱体还原速率. 相似文献
976.
Meng-dan QIAN Ji-long XUE Sheng-jie XIA Zhe-ming NI Jun-hui JIANG Yong-yong CAO 《燃料化学学报》2017,45(1):34-42
采用密度泛函理论(DFT)研究糠醛在最稳定Pd/Cu(111)双金属表面上的吸附构型和糠醛脱碳及加氢的反应机理。结果表明,当糠醛初始吸附于O_3-Pd-top、O_7-Cu-hcp位时,吸附构型最稳定,其吸附能为73.4 kJ/mol。糠醛在Pd/Cu(111)双金属表面上更易发生脱碳反应。对于糠醛脱碳反应,所需活化能较低,各个基元反应均为放热反应,糠醛更易先失去支链上的H形成(C_4H_3O)CO,然后中间体脱碳加氢得到呋喃,其中,C_4H_3O加氢生成呋喃所需活化能(72.6 kJ/mol)最高,是反应的控速步骤。对于加氢反应,糠醛与首个氢原子的反应需要最大的活化能(290.4 kJ/mol),是反应的限速步骤。 相似文献
977.
Mohamed R. Shehata Shokry A. Shokry Mahmoud A. Mabrouk 《Journal of Coordination Chemistry》2015,68(17-18):3272-3281
Pd(BHEP)Cl2 was synthesized and characterized (BHEP = 1,4-bis(2-hydroxyethyl)piperazine). The complex decomposes in two steps, leaving a residue of palladium metal. Amino acid ester (L) reacts with [Pd(BHEP)(H2O)2]2+ (BHEP = 1,4-bis(2-hydroxyethyl)piperazine), giving mixed-ligand complexes, [Pd(BHEP)L]2+. The kinetics of hydrolysis of [Pd(BHEP)L]2+ have been studied by pH-stat technique, and rate constants were obtained. Rate acceleration observed for glycine methyl ester is high. The effect with methionine methyl ester is much less marked, as the mixed-ligand complexes with these ligands do not involve alkoxycarbonyl donors. Possible mechanisms for these reactions are considered. 相似文献
978.
979.
A promising electrochemical sensor was fabricated by electrodeposition of Pd nanoparticles (PdNPs) on poly(thiophene-3-acetic acid) (PTAA)-modified glassy carbon electrode (GCE), forming a PdNPs/PTAA composites-modified GCE (PdNPs/PTAA/GCE). Scanning electron microscope (SEM) and electrochemical techniques were used for the characterization of these composites. It was found that the PdNPs/PTAA layer was very uniform. Electrochemical experiments showed that this proposed PdNPs/PTAA composites-modified electrode exhibited excellent electrocatalytic activity towards the oxidation of hydrazine. Under the optimum conditions, the proposed sensor can be applied to the quantification of hydrazine with a wide linear range from 8.0?10-9 mol/L to 1.0?10-5 mol/L with a low detection limit of 2.67?10-9 mol/L. The experiment results also showed that the sensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other potential competing species. 相似文献
980.
L. M. Blinov Corresponding author S. P. Palto F. V. Podgornov H. Moritake W. Haase 《Liquid crystals》2013,40(1):61-70
The hysteresis-free electro-optical switching, or so-called V-shaped, regime has been studied in a commercial ferroelectric liquid crystal (FLC) mixture having a smectic C* phase with a very small value of spontaneous polarization. The FLC was introduced into commercial EHC cells with thin aligning layers. In such cells V-shaped switching could be observed only at very low frequencies, less than 1?Hz. However, when the same material is strongly doped with a conductive impurity, its conductivity markedly increases and hysteresis-free switching is observed over a wide range of applied frequencies and voltages. Experimental results are in good agreement with computer modelling carried out as part of this work. The modelling takes into account all the important parameters of smectic C* FLC: non-polar anchoring conditions, possible bookshelf and chevron structures, the capacitance of the aligning layers and the conductivity of a FLC. The last two factors appear to be the most crucial for hysteresis-free switching in the smectic C* phase. 相似文献