Hydrogen, on palladium

Figure Bl.26.1. Sorption isothemi for chemisorption of hydrogen on palladium film at 273 K (Stephens S J 19597. Phys. Chem.. 63 188-94).

Conrad FI, ErtI G and Latta E E 1974 Adsorption of hydrogen on palladium single crystal surfaces Surf. Sc/41 435-46... 

A -Pyrazolines are obtained by the reduction of pyrazoles with sodium and alcohol, by catalytic hydrogenation on palladium or by electrochemical means (B-76MI40402). In some cases the reduction proceeds further yielding pyrazolidines and open-chain compounds. 

Catalytic Reactivity of Hydrogen on Palladium and Nickel Hydride Phases... 

The catalytic system studied by Rennard and Kokes was in fact very complex. It can be expected that the satisfactory prolongation of the reaction should, however, result in a deviation from the formulated kinetics. Unfortunately no investigation comparable to that of Scholten and Kon-valinka has been done in the case of olefin hydrogenation. Such a study of the catalytic activity of the pure /3-phase of palladium hydride in comparison with the a- or (a + /3)-phases would supplement our knowledge concerning catalytic hydrogenation on palladium. 

In the reactions so far studied, the formation of an equilibrium distribution of olefins is more readily attained than is an equilihrium distribution of saturated products. But, if two or more isomeric olefins may be formed from a given substrate, the initial distribution may be far from the equilibrium value, as illustrated in Fig. 9 for the hydrogenation on palladium of 2-methylmethylenecyclohexane. This distrihution must in part be a consequence of the manner in which the half-hydrogenated... 

An improved route to milnacipran (2) and derivatives is described in Scheme 14.5. In this approach, lactone 20 was opened with lithium diethylamide to provide amide alcohol 25, which was readily transformed into azide 26. Hydrogenation on palladium-carbon directly led to the desired target in 86% yield over the three steps. 

Alcohol Synthesis from Carbon Oxides and Hydrogen on Palladium and Rhodium Catalysts... 

The mechanism of the evolution of hydrogen on palladium in alkaline medium and associated internal damage phenomena were discussed in a recent paper by Bockris and Minevski [141]. The aim of the paper was to get support for their belief concerning the occurrence of nuclear reaction inside the metal. However, the authors arrived at the conclusion that the results obtained could be explained by an atomic-molecular (nonnuclear) model. 

Triphenyl-4//-pyran 151c or its 2Hisomer was thought to be a product (mp 225 °C) after partial hydrogenation on palladium of enedione 40 in acetic acid in equilibrium with 2,4,6-triphenylpyrylium acetate.217... 

It can be hydrolysed with potassium hydroxide solution to yield potassium chlorate and phenol. When reduced with hydrogen on palladium it yielded benzene, HC1 and water [53]. 

The Metathesis of Unsaturated Hydrocarbons Catalyzed by Transition Metal Compounds J. C. Mol and J. A. Moulijn One-Component Catalysts for Polymerization of Olefins Yu. Yermakov and V. Zakharov The Economics of Catalytic Processes J. Dewing and D. S. Davies Catalytic Reactivity of Hydrogen on Palladium and Nickel Hydride Phases... 

In order to confirm the stmcture of the tricyclic thietane 60, it underwent several reactions <20040L1313>, which were performed on the substituent of the ring carbon atom. The thietane 60 underwent hydrogenation on palladium-on-charcoal to give the fully saturated compound 61. The presence of a double bond in compound 60 was also confirmed by [4+2] Diels-Alder cycloaddition of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate as well as of diphenyl-isobenzofuran, which led to the formation of cycloadducts 62 and 63, respectively (Scheme 10) <20040L1313>. 

Isoprene Hydrogenation on Palladium Black Influence of Diethylsulfide... 

Recently, Rooney and co-workers (23,58,59) have questioned the view that triadsorption by loss of 3 hydrogen atoms from the alkane is the minimum requirement for bond-shift reactions. They studied the isomerization of a series of caged hydrocarbons in excess hydrogen on palladium and platinum catalysts. The compounds were chosen in order to render difficult or totally exclude a mechanism involving aory-triadsorbed species. Thus, l,7,7-trimethyl[2,2,l]-heptane interconverts with its endo- and exo-2,3,3-trimethyl isomers, bicyclo-[3,2,2] octane changes to bicyclo[3,3,l] nonane, and protoadamantane to... 

The Economics of Catalytic Processes J. Dewing and D. S. Davies Catalytic Reactivity of Hydrogen on Palladium and Nickel Hydride Phases W. Palczewska... 

Methods for monitoring the amount of adsorbed hydrogen on palladium mesowire are described by Monty [6] and Penner [7]. 

A simple test of this suggestion is the comparison of a five-layer slab calculation for the Knight shift in platinum (70) with the spectral fits of the layer model (Fig. 48). In both cases the surface resonance is shifted about 4% to low field wuth respect to the bulk signal, and the subsurface signal is found at approximately the halfway point. Another test is qualitatively to compare experimental results for hydrogen chemisorption on platinum (Fig. 55) with a calculation for hydrogen on palladium (175) in both cases an important diminution of the surface LDOS on the metal is found. 

Interestingly, the same catalyst is used for the conversion of furfiiral to furan, so that the question may be asked why THF is not made directly from furfural. The explanation lies in the fact that the conversion of furfural to furan liberates carbon monoxide which has such a high heat of adsorption on palladium that hydrogen cannot be adsorbed simultaneously. The heat of adsorption of carbon monoxide on palladium exceeds the heat of adsorption of hydrogen on palladium by 14 kcal/mole (58.576 kJ/mole). 

Yasunobi T, Yasumoii I (1971) Pressure jump and isotope replacement studies of acetylene hydrogenation on palladium surface. J Phys Chem 75 880... 

Gua LZ, Kho KE (1988) Kinetics of acetylene hydrogenation on palladium deposited on alumina. Kinet Catal 29 381... 

Finally, dynamic Monte Carlo simulations are very useful in assessing the overall reactivity of a catalytic surface, which must include the effects of lateral interactions between adsorbates and the mobility of adsorbates on the surface in reaching the active sites. The importance of treating lateral interactions was demonstrated in detailed ab initio-based dynamic Monte Carlo simulations of ethylene hydrogenation on palladium and PdAu alloys. Surface diffusion of CO on PtRu alloy surfaces was shown to be essential to explain the qualititative features of the experimental CO stripping voltammetry. Without adsorbate mobility, these bifunctional surfaces do not show any catalytic enhancement with respect to the pure metals. 

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