Heterogeneous Pd/C-catalyzed ligand-free Suzuki-Miyaura coupling reaction using aryl boronic esters

Heterogeneous Pd/C-catalyzed Suzuki-Miyaura cross-coupling reaction of aryl boronic esters with aryl bromides was successfully carried out in aqueous media at room temperature without the use of a ligand such as phosphine derivatives.     

Investigation of optical nonlinearities in Pd(po)2 by Z-scan technique

With nanosecond scale at a 532 nm wavelength, we firstly measured the nonlinear optical absorption and refraction coefficients of Pd(po)₂ complex by using Z-scan technique, here Hpo=1-hydioxy-2-pyridone. We describe an empirical expression for the case when nonlinear refraction is accompanied by nonlinear absorption to separately evaluate the nonlinear refraction and the nonlinear absorption by performing straightforward measurements with the aperture removed. The nonlinear optical response of Pd(po)₂ was determined by the linear decreasing irradiance-dependence. The nonlinear absorption originates from the near resonant two-photon absorption while the mechanism of the nonlinear refraction is the near resonant two-photon absorption transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant two-photon absorption.     

嵌入(或载在)Y型分子筛上Pd粒子的XPS研究

1前言早在70年代末80年代初，就有文献报道在载体上的金属Pd的某些性能，并注意到将其作为催化剂在甲醇合成上有很高的活性和选择性[1~3]，然而并没有继续进行系统研究．80年代末，Sachtler等人开始在这一领域进行更广泛、更细致、更深入的研究[4~8]．他们不仅研究了载在分子筛上的Pd，也研究了Pd与其他过渡金属所形成的合金的性能．它们的催化性质研究包括对CO加氢、新戊烷和氢解和异构化以及甲基环戊烷的开环和扩环反应[4~9]．对Pd的其他性质的研究，还包括采用TPR、TPD、TPO和TPMS等技术，分析了Pd或其合金等金属原子在NaY分子…     

Adsorption of methane and ethane, 2. Studies of metal blacks in a dynamic system

The irreversible adsorption of methane and ethane increases with increasing temperature on Pt, Pd and Rh blacks. Data indicate a one-carbon attachment of ethane on Pt and Pd. A two-carbon attachment of ethane is observed upon adsorption on Rh.     

Interaction of SO2 with O2 over mixed Pt, Pd, Pt?Pd and Pt?Ru oxidation catalysts and combined treatment of automobile exhaust gases

TPD, XPS IR methods were used to study how the composition of mixed Pt and Pd contacts over Al₂O₃ affects the nature of SO₂ complexes formed in the presence of O₂. Two types of sulfates of different structure and binding strength are formed in SO₂ oxidation by oxygen over Pt and Pd contacts. Introducing elements such as Co and Cr into the composition, one can significantly reduce the formation of weakly binding sulfate-1 as well as sulfate-2 too.     

Application of Pd-catalysed amines arylation for the synthesis of benzopolyazamacrocycles

Amination of 1,2- or 1,3-dihalobenzenes by linear polyamines in the presence of Pd(dba)₂/BINAP catalytic system can serve as a convenient one-pot procedure for the synthesis of benzopolyazamacrocycles.     

Phase transition in Pd_(40)Ni_(10)Cu_(30)P_(20) bulk metallic glass under HP & HT

Bulk metallic glass (BMG) can be regarded as a metallic solid with a frozen-in melt structure which lacks atomic periodicity. Generally, BMG is not in an internal equilib- rium state (IES) but may change to the IES when it obtains an appropriate energy to overcome the energy barrier. High pressure and temperature can be a driving force to cause various transitions in amorphous materials, such as a transition from the amor- phous to the crystalline[1―8] or from the crystalline to the amorp…     

Ultrasonic-assisted synthesis of two dimensional coral-like Pd nanosheets supported on reduced graphene oxide for enhanced electrocatalytic performance

Two dimensional (2D) Pd nanosheets supported on reduced graphene oxide (Pd/rGO) were prepared through a sonochemical routine induced by cetyltrimethylammonium bromide (CTAB). Coral-like porous Pd nanosheets (Pd/rGO-u) were obtained under the sonication condition (25 kHz, 600 W, ultrasonic transducer), while square Pd nanosheets (Pd/rGO-c) were produced via traditional chemical reduction. The size of Pd nanosheets of Pd/rGO-u and Pd/rGO-c are 69.7 nm and 59.7 nm, and the thickness are 4.6 nm and 4.4 nm, respectively. The carrier GO was proved to be partially reduced to rGO with good electrical conductivity and oxygen-containing groups facilitated a good dispersion of Pd nanosheets. The interaction between GO and CTAB made the alkyl chain assembles to a 2D lamella micelles which limit the growth of Pd atoms resulting in the formation of 2D nanosheets. A high ultrasonic power promotes the reduction and the formation of porous structure. Additionally, Pd/rGO-u exhibited a favorable electrocatalytic performance toward oxygen reduction reaction (ORR) in alkaline condition, which provided a potential synthetic strategy assisted by sonication for high-performance 2D materials.     

Effect of solution concentration on physicochemical and gas sensing properties of sprayed WO3 thin films

Sub-stoichiometric tungsten trioxide (WO₃) thin films are deposited onto the glass substrates by spray pyrolysis technique using ammonium metatungstate. Effect of solution concentration on structural, morphological, optical, electrical and NO₂ sensing properties of WO₃ thin films is studied. Films are polycrystalline with monoclinic crystal structure and sub-stoichiometric as observed form the XRD and XPS studies, respectively. The SEM and AFM images show micro grained structure and surface roughness increases with increase in solution concentration. The PL studies revealed that the majority of the defects are the oxygen vacancies. From XPS and PL studies it is observed that, oxygen vacancies decrease with increase in solution concentration. The dielectric constant of the films as a function of frequency is in concurrence with resistivity measurements. Films show reproducible and reversible gas response at various operating temperatures and gas concentrations. Highest sensor response (38%) towards 200 ppm NO₂ concentration is observed for the film with 15 mM solution concentration at moderate operating temperature (200 °C). Pd sensitization enhanced gas response to 68% and improved kinetics of the sensor. Films are highly selective towards NO₂ as compared with the various gases such as SO₂, LPG, NH₃ and H₂S.     

钯催化甲酸为氢源的芳硝基化合物直接加氢和一锅法酰胺化

Pd/C催化剂实现了甲酸为氢源的芳硝基化合物的直接加氢及甲酸为氢源和羰基源的一锅法芳硝基化合物的酰胺化.在芳硝基化合物的直接加氢过程中,该体系体现了很好的催化活性,实现了对同时带有其它可还原官能团的芳硝基化合物的选择性加氢,得到较高收率的胺类化合物.同时,通过提高反应温度和增加甲酸的量,实现了芳硝基化合物的加氢和甲酰化的串联反应,该体系体现了较高的催化活性.