Hydrogenation of 2-phenyl-1-propene on platinum black modified with copper

1980 ◽  
Vol 45 (12) ◽  
pp. 3541-3545
Author(s):  
Ivo Paseka ◽  
Libor Červený ◽  
Josef Mach ◽  
Vlastimil Růžička
Keyword(s):  
Reaction Rate ◽  
Surface Coverage ◽  
Platinum Black ◽  
Hydrogenation Rate ◽  
Platinum Surface ◽  
Adsorption Sites ◽  
Pt Black

Copper deposited from a solution of copper(II) formate on Pt-black at surface coverage lower than unity is present on the platinum surface both in the form of ad-atoms and in the form of multiatomic layers. From the dependence of the hydrogenation rate on coverage by copper is followed that the reaction rate depended on the number of free pairs of the adsorption sites of platinum unoccupied by copper.

Hydrogenation of Para-Nitrotoluene on Catalytic Systems Containing Oxides of Rare Earth Elements

2021 ◽  
Vol 410 ◽  
pp. 389-393
Author(s):  
Galina M. Kurunina ◽  
Olga M. Ivankina ◽  
Gennady M. Butov
Keyword(s):  
Rare Earth ◽  
Reaction Rate ◽  
High Selectivity ◽  
Nitro Compounds ◽  
Aqueous Alcohol ◽  
Hydrogenation Rate ◽  
Catalytic Systems ◽  
Liquid Phase Hydrogenation ◽  
Aqueous Alcohol Solutions ◽  
Hydrogenation Reactions

This work is devoted to the study of the activity of 1% platinum catalysts containing rare earth element oxides (OREE) - Gd2O3, Ce2O3 and aluminum oxide as a carrier in the hydrogenation reactions of nitro compounds on the example of n-nitrotoluene. These catalytic systems in the conditions of liquid-phase hydrogenation provide high selectivity of the process and practically quantitative yield. The process was controlled by the potentiometric method, the reaction rate was judged by the amount of hydrogen absorbed per unit time. It is found that 20% and higher aqueous alcohol solutions can be used as a solvent during hydrogenation. It was found that the initial hydrogenation rate for 1% Pt/Gd2O3 is 3.2 times higher, and for 1% Pt/Ce2O3 Cerium it is 1.6 times higher relative to the 1% Pt/Al2O3 comparison catalyst.

scholarly journals A self-adjusting platinum surface for acetone hydrogenation

2020 ◽  
Vol 117 (7) ◽  
pp. 3446-3450 ◽  
Author(s):  
Benginur Demir ◽  
Thomas Kropp ◽  
Keishla R. Rivera-Dones ◽  
Elise B. Gilcher ◽  
George W. Huber ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Density Functional ◽  
Surface Coverage ◽  
Binding Energies ◽  
Microkinetic Modeling ◽  
Reaction Conditions ◽  
Platinum Surface ◽  
Kinetics Parameters ◽  
Supported Platinum Catalysts ◽  
Wide Range

We show that platinum displays a self-adjusting surface that is active for the hydrogenation of acetone over a wide range of reaction conditions. Reaction kinetics measurements under steady-state and transient conditions at temperatures near 350 K, electronic structure calculations employing density-functional theory, and microkinetic modeling were employed to study this behavior over supported platinum catalysts. The importance of surface coverage effects was highlighted by evaluating the transient response of isopropanol formation following either removal of the reactant ketone from the feed, or its substitution with a similarly structured species. The extent to which adsorbed intermediates that lead to the formation of isopropanol were removed from the catalytic surface was observed to be higher following ketone substitution in comparison to its removal, indicating that surface species leading to isopropanol become more strongly adsorbed on the surface as the coverage decreases during the desorption experiment. This phenomenon occurs as a result of adsorbate–adsorbate repulsive interactions on the catalyst surface which adjust with respect to the reaction conditions. Reaction kinetics parameters obtained experimentally were in agreement with those predicted by microkinetic modeling when the binding energies, activation energies, and entropies of adsorbed species and transition states were expressed as a function of surface coverage of the most abundant surface intermediate (MASI, C3H6OH*). It is important that these effects of surface coverage be incorporated dynamically in the microkinetic model (e.g., using the Bragg–Williams approximation) to describe the experimental data over a wide range of acetone partial pressures.

Dissociation of H2O molecule adsorbed on Si (001) 2×1 surface: a theoretical study

2008 ◽  
Vol 1145 ◽  
Author(s):  
Hyun-Chul Oh ◽  
Hwa-Il Seo ◽  
Yeong-Cheol Kim
Keyword(s):  
Water Molecule ◽  
Room Temperature ◽  
Surface Coverage ◽  
Theoretical Study ◽  
Surface Model ◽  
Water Molecules ◽  
First Principles Calculations ◽  
Adsorption Sites ◽  
Adsorption Surface ◽  
Adsorption And Dissociation

AbstractThe adsorption and dissociation behavior of water molecule below and above the critical dissociation temperatures were studied by first principles calculations. We found that water-molecule adsorption (surface coverage, θ=0.25) on the down Si atom of a Si dimer in two dimers surface model was 0.26 eV more favorable than that on the up Si atom. The activation energies of water molecule on the down Si atom for interdimer and intradimer dissociations were 0.17 eV and 0.20 eV, respectively. Due to the lower activation energy, the water molecule splits into H and OH immediately once it adsorbs on down Si atom of the Si (001) surface at room temperature. There were three different adsorption sites among four sites of the two dimers for the second water molecule (θ=0.5): one was preoccupied by OH of the first water molecule; up Si atom of the same-dimer with 76.3 % probability, up Si atom of the adjacent-dimer with 23.6 % probability, and down Si atom of the adjacent-dimer with 0.1 % probability. Thus, ½ monolayer of OH sites on the Si (001) surface are irregularly distributed when water molecules are adsorbed and dissociated at room temperature.

Selectivities of some hydrogenations on metal-modified platinum catalysts

1983 ◽  
Vol 48 (12) ◽  
pp. 3532-3538
Author(s):  
Libor Červený ◽  
Karel Surma ◽  
Vlastimil Růžička ◽  
Ivo Paseka
Keyword(s):  
Atmospheric Pressure ◽  
Surface Coverage ◽  
Platinum Catalysts ◽  
Hydrogenation Rate ◽  
Competitive Hydrogenation

The rates and selectivities of hydrogenation on platinum catalysts modified with monolayers of copper, thallium, lead, or bismuth were studied at 20 °C and atmospheric pressure for the competitive hydrogenation of 1-hexene and 1-undecene in cyclohexane and for the consecutive hydrogenation of 1,5-cyclooctadiene in cyclohexane or ethanol. For the former system, the selectivity was unaffected by the modifying metal and the degree of the surface coverage with the metal, and the relative specific hydrogenation rate decreased only slightly with the degree of surface coverage. For the latter system, the selectivity of hydrogenation to cyclooctene increased with the content of the modifying metal, while the relative specific hydrogenation rate decreased markedly.

scholarly journals Measuring Electric Charge and Molecular Coverage on Electrode Surface from Transient Induced Molecular Electronic Signal (TIMES)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ping-Wei Chen ◽  
Chi-Yang Tseng ◽  
Fumin Shi ◽  
Bo Bi ◽  
Yu-Hwa Lo
Keyword(s):  
Surface Coverage ◽  
Direct Method ◽  
Accurate Method ◽  
Blocking Agent ◽  
Double Layers ◽  
Molecular Electronic ◽  
Platinum Surface ◽  
Biochemical Sensing ◽  
Electrode Interface ◽  
Electronic Signal

Abstract Charge density and molecular coverage on the surface of electrode play major roles in the science and technology of surface chemistry and biochemical sensing. However, there has been no easy and direct method to characterize these quantities. By extending the method of Transient Induced Molecular Electronic Signal (TIMES) which we have used to measure molecular interactions, we are able to quantify the amount of charge in the double layers at the solution/electrode interface for different buffer strengths, buffer types, and pH values. Most uniquely, such capabilities can be applied to study surface coverage of immobilized molecules. As an example, we have measured the surface coverage for thiol-modified single-strand deoxyribonucleic acid (ssDNA) as anchored probe and 6-Mercapto-1-hexanol (MCH) as blocking agent on the platinum surface. Through these experiments, we demonstrate that TIMES offers a simple and accurate method to quantify surface charge and coverage of molecules on a metal surface, as an enabling tool for studies of surface properties and surface functionalization for biochemical sensing and reactions.

Hydrogenation of 2-phenyl-1-propene and 1-hexene on platinum black surface modified by Pb, Tl and Bi atoms

1982 ◽  
Vol 47 (4) ◽  
pp. 1222-1228 ◽  
Author(s):  
Ivo Paseka ◽  
Libor Červený ◽  
Dagmar Šmigolová ◽  
Vlastimil Růžička
Keyword(s):  
Organic Substance ◽  
Platinum Black ◽  
Hydrogenation Rate ◽  
Low Degree ◽  
Modified Surfaces ◽  
Black Surface ◽  
Surface Modified

Hydrogenation of 2-phenyl-1-propene and 1-hexene in ethanol, toluene and benzene was studied on platinum black modified by ad-atoms of lead, thallium, and bismuth. The experimental dependences of the specific hydrogenation rate on the degree of coverage by the metal ad-atoms are interpreted under the assumption that the substrate and hydrogen take part in the reaction and at low degree of the coverage, the organic substance is adsorbed on the modified and non-modified surfaces to the same extent.

Study of properties of copper-modified platinum catalysts

1981 ◽  
Vol 46 (8) ◽  
pp. 1958-1964 ◽  
Author(s):  
Libor Červený ◽  
Ivo Paseka ◽  
Vladimír Stuchlý ◽  
Vlastimil Růžička
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Hydrogen Adsorption ◽  
Platinum Catalysts ◽  
Platinum Black ◽  
Platinum Surface ◽  
Hydrogen Stream

The properties of catalysts based on platinum black modified with copper were studied. The free platinum surface area and the amount of the surface copper were determined by potentiodynamic measurements; the isosteric heats of hydrogen adsorption were also measured. The catalysts were tested in gas phase dehydrogenation of cyclohexanol; after the reaction, and also after mere thermal exposition of the catalyst to hydrogen stream, the surface of the catalysts was re-examined.

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