scholarly journals Heterogeneous Pd catalysts supported on silica matrices

RSC Advances ◽  
2014 ◽  
Vol 4 (110) ◽  
pp. 65137-65162 ◽  
Author(s):  
Maksym Opanasenko ◽  
Petr Štěpnička ◽  
Jiří Čejka
Keyword(s):  
Palladium Catalysts ◽  
Organic Transformations ◽  
Pd Catalysts ◽  
Different Types ◽  
Silica Matrices

Features, advantages and limitations associated with palladium catalysts deposited over various siliceous supports in different types of practically useful organic transformations are reviewed.

Pd catalysts supported on dual-pore monolithic silica beads for chemoselective hydrogenation under batch and flow reaction conditions

2020 ◽  
Vol 10 (18) ◽  
pp. 6359-6367
Author(s):  
Tsuyoshi Yamada ◽  
Aya Ogawa ◽  
Hayato Masuda ◽  
Wataru Teranishi ◽  
Akiko Fujii ◽  
...  
Keyword(s):  
Palladium Catalysts ◽  
Reaction Conditions ◽  
Pd Catalysts ◽  
Monolithic Silica ◽  
Chemoselective Hydrogenation ◽  
Different Types ◽  
Silica Beads ◽  
Flow Reaction

Two different types of palladium catalysts supported on dual-pore monolithic silica beads [5% Pd/SM and 0.25% Pd/SM(sc)] for chemoselective hydrogenation were developed.

Model reactions for the study of hydrogenation and acidic activity of palladium catalysts

1987 ◽  
Vol 52 (8) ◽  
pp. 2019-2027 ◽  
Author(s):  
Libor Červený ◽  
Nguyen Thi Du ◽  
Ivo Paseka
Keyword(s):  
Palladium Catalysts ◽  
Styrene Oxide ◽  
Side Reactions ◽  
Pd Catalysts ◽  
Variable Parameters ◽  
Acid Properties ◽  
Liquid Phase Hydrogenation ◽  
Acid Catalysed Reactions ◽  
Different Content ◽  
Model Reactions

Palladium catalysts have been used to study the hydrogenation of 1-phenyl-2-butene-1-ol which is accompanied by several side reactions considered to be acid-catalysed. Another model reaction studied was dehydration and subsequent hydrogenation or hydrogenolysis of 1-phenyl-1,3-propanediol to 3-phenyl-1-propanol, accompanied by formation of propylbenzene. The dehydration and propylbenzene formation can be again classified as acid-catalysed reactions. Another one is methanolysis of styrene oxide taking place under conditions of liquid phase hydrogenation due to the acid properties of Pd-H systems. Hydrogenation activity of Pd catalysts was tested by hydrogenation of cyclohexene. Sixteen Pd catalysts on different supports and with different content of active component were used, their activity and selectivity was determined and the effect of variable parameters in the synthesis of these catalysts on the activity and selectivity is discussed.

scholarly journals Development of palladium catalysts modified by ruthenium and molybdenum as anode in direct ethanol fuel cell

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Yonis Fornazier Filho ◽  
Ana Caroliny Carvalho da Cruz ◽  
Rolando Pedicini ◽  
José Ricardo Cezar Salgado ◽  
Priscilla Paiva Luz ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Palladium Catalysts ◽  
Carbon Support ◽  
X Ray Diffraction ◽  
Direct Ethanol Fuel Cell ◽  
Pd Catalysts ◽  
Bifunctional Mechanism ◽  
Catalytic Activities ◽  
Intrinsic Mechanism ◽  
Ternary Catalysts

AbstractPhysical and electrochemical properties of Pd catalysts combined with Ru and Mo on carbon support were investigated. To this end, Pd, Pd1.3Ru1.0, Pd3.2Ru1.3Mo1.0 and Pd1.5Ru0.8Mo1.0 were synthesized on Carbon Vulcan XC72 support by the method of thermal decomposition of polymeric precursors and then physically and electrochemically characterized. The highest reaction yields are obtained for Pd3.2Ru1.3Mo1.0/C and Pd1.5Ru0.8Mo1.0/C and, as demonstrated by thermal analysis, they also show the smallest metal/carbon ratio compared the other catalysts. XRD (X-ray Diffraction) and Raman analyses show the presence of PdO and RuO2 for the Pd/C and the Pd1.3Ru1.0/C catalysts, respectively, a fact not observed for the Pd3.2Ru1.3 Mo1.0 /C and the Pd1.5Ru0.8Mo1.0/C catalysts. The catalytic activities were tested for the ethanol oxidation in alkaline medium. Cyclic voltammetry (CV) shows Pd1.3Ru1.0/C exhibiting the highest peak of current density, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. From, chronoamperometry (CA), it is possible to observe the lowest rate of poisoning for the Pd1.3Ru1.0/C, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. These results suggested that catalytic activity of the binary and the ternary catalysts are improved in comparison with Pd/C. The presence of RuO2 activated the bifunctional mechanism and improved the catalytic activity in the Pd1.3Ru1.0/C catalyst. The addition of Mo in the catalysts enhanced the catalytic activity by the intrinsic mechanism, suggesting a synergistic effect between metals. In summary, we suggest that it is possible to synthesize ternary PdRuMo catalysts supported on Carbon Vulcan XC72, resulting in materials with lower poisoning rates and lower costs than Pd/C. Graphic abstract

scholarly journals Altervalent cation-doped MCM-41 supported palladium catalysts and their catalytic properties

2011 ◽  
Vol 76 (6) ◽  
pp. 923-932 ◽  
Author(s):  
Haihui Jiang ◽  
Ligang Gai ◽  
Yan Tian
Keyword(s):  
Electron Microscopy ◽  
Palladium Catalysts ◽  
Xrd Analysis ◽  
Molar Ratio ◽  
Pd Catalysts ◽  
Transmission Electron ◽  
Supported Pd Catalysts ◽  
Supported Palladium ◽  
Mcm 41 ◽  
Supported Pd

Metal cation-doped MCM-41 (M-MCM-41, M=Al, Ce, Co, V, or Zr) supported Pd catalysts (Pd/M-MCM-41) were prepared by a solution-based reduction method. The catalysts were characterized by Xray diffraction (XRD) analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and further evaluated by selective hydrogenation of parachloronitrobenzene (p-CNB) in anhydrous ethanol. The metal cationcontaining Pd catalysts can efficiently enhance the selectivity for parachloroaniline (p-CAN). The highest selectivity of 96.5 % in the molar distribution for p-CNB to p-CAN was acquired over Pd (1.8 wt. %)/VMCM- 41 (Si/V=30, molar ratio) catalyst, and the corresponding turnover frequency (TOF) was 1.24?10-2 mol p-CNB mol-1 Pd s-1. Water molecules adsorbed by the support have important effects on both the catalytic activity of the sample and the selectivity for p-CAN. A water molecule-mediated catalytic hydrogenation is discussed.

The Effect of Physicochemical Treatment on Pd Dispersion of Carbon-Supported Pd Catalysts

2008 ◽  
Vol 135 ◽  
pp. 57-60
Author(s):  
Yong Tae Kim ◽  
Eun Duck Park ◽  
Min Kang ◽  
Jae Eui Yie
Keyword(s):  
Palladium Catalysts ◽  
Activated Carbons ◽  
Palladium Chloride ◽  
Impregnation Method ◽  
Reduction Temperature ◽  
Surface Oxygen ◽  
Carbon Supports ◽  
High Concentration ◽  
Pd Catalysts ◽  
Pd Dispersion

Carbon-supported palladium catalysts were prepared by an impregnation method using palladium chloride and different carbon supports such as activated carbons with different surface oxygen concentrations and a mesoporous carbon, CMK-5.. The different degree of surface oxidation was achieved by the nitric acid and high-temperature heat treatment. The molecular PdCl2 species was stabilized by adding an HCl in an impregnation step.. As the reduction temperature increased, the Pd dispersion decreased for all Pd catalysts. There was no noticeable difference in Pd dispersion among Pd catalysts supported on carbon supports with different physicochemical properties when the reduction temperature was 423 K. Pd catalysts supported on the carbon support with a high concentration of surface oxygen groups showed a better dispersion than did other Pd catalysts when they were reduced at 573 K. The maximum Pd dispersion was observed over Pd catalyst supported on carbon supports with the highest surface area when the reduction temperature was higher than 573 K.

Metal nanoparticles embedded in AIEE active supramolecular assemblies: robust, green and reusable nanocatalysts

2019 ◽  
Vol 48 (15) ◽  
pp. 4769-4773 ◽  
Author(s):  
Harnimarta Deol ◽  
Gurpreet Singh ◽  
Manoj Kumar ◽  
Vandana Bhalla
Keyword(s):  
Visible Light ◽  
Metal Nanoparticles ◽  
Visible Light Irradiation ◽  
Supramolecular Assemblies ◽  
Light Irradiation ◽  
Organic Transformations ◽  
Different Types

Multi-functional AIEE-active supramolecular assemblies act as nanoreactors for the preparation of different types of metal NPs. The in situ generated metal NPs stabilized by supramolecular assemblies act as nanocatalysts for various organic transformations under thermal/visible light irradiation.

Electrocatalytic dechlorination of atrazine

2002 ◽  
Vol 80 (2) ◽  
pp. 200-206 ◽  
Author(s):  
Naomi L Stock ◽  
Nigel J Bunce
Keyword(s):  
Palladium Catalysts ◽  
Catalyst Concentration ◽  
Lag Time ◽  
Vitreous Carbon ◽  
Reticulated Vitreous Carbon ◽  
Hydrogen Atoms ◽  
Pd Catalysts ◽  
Noble Metal Catalysts ◽  
Catalytically Active ◽  
Electrocatalytic Dechlorination

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), a photosynthetic inhibitor that is used in large quantities for weed control in corn and sorghum, is dechlorinated in aqueous solution upon electrolysis at a reticulated vitreous carbon cathode in the presence of noble-metal catalysts. Electrocatalytic hydrogenolysis to 2-ethylamino-4-isopropylamino-s-triazine occurs in quantitative yield, and is most efficient with palladium-based catalysts. Current efficiency increases with atrazine and catalyst concentration, and decreasing current density. A previously unobserved phenomenon with Pd catalysts is that current must be passed for a certain time before dechlorination commences. This lag time is explained in terms of the palladium lattice absorbing a finite amount of hydrogen before catalytically active hydrogen atoms appear on the catalyst surface.Key words: electrocatalytic hydrogenoloysis, dechlorination, atrazine, palladium catalysts.

Modelling of the Deactivation of Polymer-Supported Palladium Catalysts in the Hydrogenation of 4-Nitrotoluene

1998 ◽  
Vol 63 (7) ◽  
pp. 1074-1088 ◽  
Author(s):  
Milan Králik ◽  
Roman Fišera ◽  
Marco Zecca ◽  
Angelo A. D'Archivio ◽  
Luciano Galantini ◽  
...  
Keyword(s):  
Palladium Catalysts ◽  
Spin Echo ◽  
Polymer Network ◽  
Reaction Rates ◽  
Gradient Field ◽  
Model Parameters ◽  
Simultaneous Treatment ◽  
Pd Catalysts ◽  
Before And After ◽  
Exclusion Chromatography

The kinetics of the hydrogenation of 4-nitrotoluene over Pd catalysts supported on sulfonated polystyrene and simultaneous deactivation of these catalysts were investigated. Reaction rates of both the hydrogenation and the dissolution of Pd crystallites were related to the total Pd surface. The average radius of ideal spherical crystallites, as determined by X-ray powder diffraction analysis, was taken as the starting value of the crystallite size. Stability of the polymer network was checked by Inverse Steric Exclusion Chromatography (ISEC). The ESR and Static Gradient field Spin Echo (SGSE) NMR spectroscopies were used to assess the accessibility and diffusivity before and after deactivation experiments. Langmuir-Hinshelwood type kinetic models were applied to describe the hydrogenation of 4-nitrotoluene. The kinetic law was incorporated into a more comprehensive model involving also diffusion of reactants inside catalytic particles. Simultaneous treatment of a few sets of kinetic data from batch hydrogenation carried out at 0.25-0.75 MPa yielded reliable values of model parameters. The model showed an increasing rate of dissolution of palladium with decreasing concentration of hydrogen and increasing concentration of 4-nitrotoluene. The latter fact supports the hypothesis that the nitro compound is the oxidant responsible for the dissolution of palladium.

A Single Turnover (STO) Characterization of Supported Palladium Catalysts

1987 ◽  
Vol 111 ◽  
Author(s):  
Robert L. Augustine ◽  
David R. Baum
Keyword(s):  
Palladium Catalysts ◽  
Active Sites ◽  
Pt Catalyst ◽  
Catalyst Characterization ◽  
Pt Catalysts ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Pd Catalysts ◽  
Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

scholarly journals Pd Catalysts Supported on Bamboo-Like Nitrogen-Doped Carbon Nanotubes for Hydrogen Production

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1501
Author(s):  
Arina N. Suboch ◽  
Olga Y. Podyacheva
Keyword(s):  
Carbon Nanotubes ◽  
Hydrogen Production ◽  
Metallic Nanoparticles ◽  
Palladium Catalysts ◽  
Fold Increase ◽  
Maximum Activity ◽  
Pd Catalysts ◽  
Nitrogen Doped ◽  
Supported Palladium ◽  
Nitrogen Doped Carbon

Bamboo-like nitrogen-doped carbon nanotubes (N-CNTs) were used to synthesize supported palladium catalysts (0.2–2 wt.%) for hydrogen production via gas phase formic acid decomposition. The beneficial role of nitrogen centers of N-CNTs in the formation of active isolated palladium ions and dispersed palladium nanoparticles was demonstrated. It was shown that although the surface layers of N-CNTs are enriched with graphitic nitrogen, palladium first interacts with accessible pyridinic centers of N-CNTs to form stable isolated palladium ions. The activity of Pd/N-CNTs catalysts is determined by the ionic capacity of N-CNTs and dispersion of metallic nanoparticles stabilized on the nitrogen centers. The maximum activity was observed for the 0.2% Pd/N-CNTs catalyst consisting of isolated palladium ions. A ten-fold increase in the concentration of supported palladium increased the contribution of metallic nanoparticles with a mean size of 1.3 nm and decreased the reaction rate by only a factor of 1.4.

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