Atmospheric Hydrogen Pressure Research Articles

A POLYION COMPLEX-SUPPORTED PALLADIUM CATALYST FOR SELECTIVE HYDROGENATION OF CONJUGATED DIOLEFINS TO MONOOLEFINS

Abstract A colloidal palladium supported on the polyion complex composed of polyacrylic acid and polyethylene imine catalyzes highly selective hydrogenation of conjugated diolefins to monoolefins at 30°C under an atmospheric hydrogen pressure.

COLLOIDAL RHODIUM IN POLYVINYL ALCOHOL AS HYDROGENATION CATALYST OF OLEFINS

Abstract A colloidal rhodium has been prepared by reduction of rhodium(III) chloride with methanol in the presence of polyvinyl alcohol. The particle size distribution of the metallic rhodium is narrow ranging from 30 to 70 Å with a maximum at 35 Å. The colloidal dispersions in methanol-water solutions are effective for the hydrogenation of olefins at 30°C under an atmospheric hydrogen pressure.

SELECTIVE HYDROGENATION OF CONJUGATED DIOLEFINS TO MONOOLEFINS CATALYZED BY A POLYMER-PALLADIUM COMPLEX

Abstract A polymer–palladium complex prepared from palladium(II) chloride and styrene-divinylbenzene copolymer with iminodiacetic acid groups is found to catalyze the selective hydrogenation of conjugated diolefins to monoolefins at 30°C under an atmospheric hydrogen pressure.

Selectivity in the Catalytic Hydrogenation of 2‐Hydroxycyclohexanone

AbstractThe catalytic hydrogenation of 2–hydroxycyclohexanone has been investigated on ruthenium, nickel, rhodium, platinum and palladium. The reaction was completed usually within several hours under an atmospheric pressure of hydrogen at room temperature. It was found that ruthenium and nickel catalysts produce more cis–cyclohexane–1, 2–diol than trans‐diol; while platinum and palladium catalysts give rise to more trans–diol than cis– form.Two adsorbed models, weak and strong, for the substrate were presented to account for the observed hydrogenation selectivity.

A hydrogen-sensitive Pd-gate MOS transistor

An n-channel MOS transistor with palladium gate was fabricated. The threshold voltage of this transistor was found to depend on the partial pressure of hydrogen in the ambient atmosphere. At a device temperature of 150 °C, 10 ppm hydrogen in air is easily detected, and in nitrogen or argon the sensitivity is considerably larger. A model, based on hydrogen adsorption on the palladium–silicon dioxide interface, is proposed. This model explains the device behavior and is also able to predict the absolute sensitivity for hydrogen in argon.

A NOVEL POLYMER–RHODIUM COMPLEX AS HYDROGENATION CATALYST OF ALKENES

Abstract A polymer–rhodium complex prepared from rhodium(III) chloride and styrene-divinylbenzene copolymer with iminodiacetic acid groups is found to catalyze the heterogeneous hydrogenation of alkenes in polar solvents at 30°C under an atmospheric hydrogen pressure. The polymer complex hydrogenates selectively the ethylenic double bonds in the alkenes with carbonyl and aromatic groups. The rates of hydrogenation of alkenes by the polymer complex are found to be markedly affected by the steric hindrance of the substrates.

A hydrogen−sensitive MOS field−effect transistor

An MOS transistor in silicon with 10−nm silicon dioxide as gate insulator and 10−nm palladium as gate electrode was fabricated. The threshold voltage of this transistor was found to be a function of the partial pressure of hydrogen in the ambient atmosphere. At a device temperature of 150 °C it was possible to detect 40 ppm hydrogen gas in air with response times less than 2 min.

Hydrogenation of ferrocene

Ferrocene and derivatives can be hydrogenated in acidic medium at ambien temperature and atmospheric hydrogen pressure using supported palladium as the catalyst.

HYDROGENATION OF ALKENES BY THE COMPLEX OF CROSS-LINKED POLYACRYLIC ACID WITH RHODIUM(111)

Abstract The complex of cross-linked polyacrylic acid with rhodium(111) catalyzes the heterogeneous hydrogenation of terminal and internal alkenes in polar solvents at 30°C under an atmospheric hydrogen pressure. The C=C double bonds can be hydrogenated selectively by the complex catalyst for the hydrogenation of the alkenes with carbonyl and aromatic groups.

HOMOGENEOUS HYDROGENATION OF ALKENES BY THE COMPLEX OF POLYACRYLIC ACID WITH RHODIUM(III)

Abstract The complex of polyacrylic acid with rhodium(III) functions as a homogeneous catalyst for the hydrogenation of terminal alkenes in methanol solution at 30°C under an atmospheric pressure of hydrogen. The triethylammonium salt of the complex is effective for the hydrogenation of internal alkenes as well as terminal alkenes.

Hydrogenation and deuteration of conjugated isomers of linoleate and linolenate with palladium, platinum, nickel and lindlar catalysts

AbstractConjugated isomers of methyl linoleate and linolenate were reduced with palladium, platinum, nickel and Lindlar catalysts at atmospheric hydrogen or deuterium pressure. After the products were separated, positions of their double bonds were determined by ozonolysis. Palladium and platinum catalysts reduced β‐eleostearate directly to monoene. Nickel reduced β‐eleostearate to dienes chiefly by 1,2‐addition and to a lesser extent by 1,4‐ and 1,6‐addition, whereas Lindlar catalyst reduced by 1,2‐and 1,6‐addition only. All catalysts reduced conjugated linoleate isomers by both 1,2‐ and 1,4‐addition, with nickel being somewhat preferential for 1,2‐addition. Selectivity for the catalytic reduction of dienes to monoenes decreased in the order: nickel, palladium and platinum. Lindlar catalyst did not isomerize or reduce monoenes that formed during reduction. Palladium and platinum did not isomerize conjugated dienes and trienes during their reduction, whereas nickel and Lindlar catalysts isomerized them slightly. Some deuterium was found in unreacted conjugated diene and triene with nickel and Lindlar catalysts, but none with palladium or platinum. Deuterated products contained a wide range of isotopic isomers with some products having up to 31 deuterium atoms. This wide deuterium distribution resulted from (a) exchange followed by addition, (b) addition followed by exchange and (c) exchange‐addition‐exchange reactions.

Hydrogenation of carbons catalyzed by transition metals

The catalytic activities of transition-metal catalysts in methane formation from carbons were investigated at temperatures up to 1050 °C under atmospheric pressure of hydrogen. The studies in a thermobalance revealed that methane was produced in several stages and the temperature of maximal rate varied from one metal catalyst to another. When the most active metal was used, the methane formation from an active carbon occurred below 200 °C and the carbon was completely gasified upon heating up to 1050 °C at the rate of 100 °C/hr. Without catalyst, carbons of only 10% were gasified under the same condition. The order of activity at the lower temperature region was Rh ≳ Ru ≳ Ir > Pt > Ni ⪢ Pd ≳ Co ≳ Fe. The reactivity depended not only on the kind of catalyst, but on the kind of carbon and the preparative method of metal-carbon mixtures. The role of metal catalysis was discussed in connection with the spill-over phenomenon.

Measurement of collisional ionization cross-sections for metal atoms in flames

The rates of collisional ionization of gaseous metal atoms, M, in the temperature range 2000 to 2800 K have been measured by optical and electrostatic probe studies in over 100 fuel-rich, atmospheric pressure hydrogen + oxygen flames diluted with each of the gases argon, nitrogen, carbon monoxide and carbon dioxide. Individual cross-sections for the process M + X j → M + + e - + X j , with X j = Ar, H 2 , N 2 , CO, CO 2 and H 2 O, and M = Li, Na, K, Rb, Cs and Tl, have been determined from a detailed analysis of the dependence of the collisional ionization rate constants on burned gas composition. They lie between 10 and 145 nm2 and are given in table 4. They show no correlation with the corresponding optical quenching cross-sections for the first excited electronic states of M. The implications of these cross-sections are discussed with regard to both their large overall magnitude and their dependence on the nature of M and X j . Elastic collision, translational de-excitation of X j contributions appear to be at least as important as processes involving rotational or vibrational de-excitation of X j .

Hydrogenation of Aniline with Ruthenium-Palladium and Ruthenium-Platinum Alloy Catalysts Supported on Activated Carbon

Hydrogenation of aniline with Ru-Pd and Ru-Pt alloy catalysts supported on activated carbon was investigated under an atmospheric pressure of hydrogen in the temperature range from 30° to 60° C. Under these conditions the pure Ru and pure Pd catalysts had very low activity for this reaction, but the alloy catalysts of these metals were active and in these alloy series a maximum activity appeared at about 25 atom% of Ru content. At the maximum point the activity was about 15 times as great as that of the pure Pd catalyst which was prepared by the same method as these alloy catalysts. The selectivity for cyclohexylamine increased by 15 mol% as compared with that of pure Pd at the composition of 25% Ru. In order to study the influence of the amino group of aniline on the hydrogenation of the benzen ring, benzene was hydrogenated with these alloy catalysts. For this reaction a maximum activity appeared at about 75 atom% of Ru content. On Ru-Pt alloy series, the hydrogenation of aniline did not show a maximum activity and the activity decreased greately when Ru was added to Pt. On this Ru-Pt series, the selectivity for cyclohexylamine changed almost linearly between the both pure metals. The hydrogenation of benzene with this alloy series was also studied. This alloy catalysts had higher activity than that of the pure metal when the reaction was carried out at 30° C. On both Ru-Pd and Ru-Pt alloy series, the compensation effect for the hydrogenation of aniline was recognised except the pure Ru catalyst. The activity and selec-tivity of the catalysts which were prepared by the deposition of a small amount of Ru on Pd or Pt metal surface, were also investigated.

The Hydrogenation of Aniline over Supported Rhodium-Palladium Alloy Catalysts

Abstract The hydrogenation of aniline was investigated in the temperature range from 30° to 50°C over Rh-Pd alloy catalysts supported on activated carbon. The reactions were mainly carried out in acetic acid at an atmospheric pressure of hydrogen. The activity per unit weight of the catalysts was measured and plotted for the alloy composition. It showed a maximum at 75–85 wt% Rh. However, the activity per unit of surface area showed a maximum at about 25 wt% Rh, and the minimum activation energy of this reaction was observed at the same composition. The relationship between the selectivity and the alloy composition was also studied. The maximum selectivity to dicyclohexylamine was observed at 20–30% Rh, while the maximum formation of N-phenylcyclohexylamine appeared at 50–60% Rh. However, the selectivity to cyclohexylamine showed a minimum at about 25% Rh. The initial rates of the formation of cyclohexylamine and N-phenylcyclohexylamine were measured and plotted for the catalyst composition. The maximum activity was observed at about 85 wt% Rh for the formation of cyclohexylamine and at 50–60% Rh for the formation of N-phenylcyclohexylamine. Then the ratios of the two simple reaction rates were calculated. At a higher Rh content, (above about 25% Rh), the selectivity increased as the ratio increased. The reaction over the catalysts prepared by different methods and the hydrogenation of aniline in cyclohexane were also investigated.

The influence of crystalline anisotropy on neck growth during the sintering of zinc

Polycrystalline zinc wires of two grain sizes and zinc single crystal wires of four orientations all of them 0.010 in. in diameter were grown. Pairs of wires from each of the six groups were sintered together at 365°C for 8 hr in a pressurized dry hydrogen atmosphere and the widths of the necks formed between pairs were measured. In the single crystal pairs, the neck width depended upon the relative orientation of the basal planes in the wire with the largest width up to 2.7 times as large as the smallest. In the polycrystalline samples those with fine grain size, of the order of neck width, had small necks, while those with coarse grain size, of the order of the wire diameter, had large necks. The observed variations in the width of the neck with relative orientation and with grain size must be caused by the anisotropy of those properties of zinc which determine the rate of material transport during sintering. For sintering by diffusional flow these are specific surface free energy and diffusivity, for sintering by evaporation and condensation they are specific surface free energy and vapor pressure. Since for these mechanisms approximate equations for the rate of neck growth exist, the maximum ratios of neck width due to the anisotropies of specific surface free energies, diffusivities and vapor pressures can be estimated. They are considerably smaller than the observed ratio of up to 2.7. The remaining material transport mechanism for the early stages of sintering is plastic flow which, in zinc, is highly anisotropic, since even at temperatures near the melting point the critical resolved shear stress for slip on the basal slip system is five to ten times lower than for slip on any other system. The measured neck width of the single crystal wire pairs can be directly related to the ease of basal slip. Those pairs which are oriented so that no basal slip is possible have small necks, while those which are favorably oriented for basal slip have large necks. The small neck width in the fine-grained wires must be due to constraint which inhibits basal slip. No such constraint exists in the necks of the coarse grained wires. Material transport by plastic flow must play an important role in the sintering of the zinc wires.

Hydrogenation and Hydrogenolysis. XIII. The Hydrogenation of Ethyl 4-Methyl-1-cyclohexenyl Ether over Platinum Metal Catalysts

Abstract The hydrogenation and hydrogenolysis of ethyl 4-methyl-1-cyclohexenyl ether (I) have been investigated with six unsupported platinum metals as catalysts at 25°C under atmospheric pressure of hydrogen. The hydrogenation of I in ethanol was accompanied by the formation of 4-methylcyclohexanone diethyl acetal (II), the extent of which depended on the nature of the catalyst metals. The ratio of the acetal formation to hydrogenation increased with respect to the catalyst metals in the sequence Os<Ru<Ir<<Rh<Pd<Pt. The amount of the hydrogenolysis to give methylcyclohexane increased in the order Pd≅Ru<<Os<Rh<Ir<<Pt at an initial stage of the hydrogenation in ethanol. This order in hydrogenolysis was explained in terms of the action of the ionized hydrogen on the catalyst surface and the olefin isomerization activity of the catalyst metals. The stereochemistry of the hydrogenation of I was also studied and the results were interpreted on the basis of the proposed mechanism. I was also hydro-genated in t-butyl alcohol and isopropyl ether as solvents and, except in a few cases, the proportion of hydrogenolysis decreased with solvent in the order ethanol>t-butyl alcohol>isopropyl ether. The stereoselectivity in ether formation did not differ much among the solvents except over palladium.

The determination of transport properties from arc experiments: Methods and results

The electrical and thermal conductivities at atmospheric pressure of nitrogen and hydrogen as determined from arc experiments are reviewed for temperatures up to 26 000°K. First results of a high pressure argon program applying similar experimental and analytical techniques are included.

The Wall-Stabilized Hydrogen Arc as a Radiation Standard in the Vacuum UV

Extensive calculations of the radiative emission of an atmospheric pressure hydrogen arc in the temperature range from 8000 to 15000 K have been undertaken, which show that a partly ionized hydrogen arc plasma may serve as an intense and accurate spectral radiation standard in the ultraviolet. The principal features of the spectrum are: Between 1215 Å and 3600 Å the hydrogen arc emits only continuous radiation, dominated by the Balmer recombination continuum. Between 1215 Å and 930 Å the lower members of the Lyman series appear strongly Stark-broadened and optically thick in their central parts. The higher Lyman lines merge into a quasi-continuum, which leads into the very strong Lyman continuum. Between 930 and about 400 Å the continuum is optically thick, i.e., it represents blackbody radiation at typical arc temperatures of 12000 to 15000 K.

Selective hydrogenation with copper catalysts: I. Isolation and identification of isomers formed during hydrogenation of linolenate

AbstractMethyl linolenate was hydrogenated with 10% copper chromite catalyst at 150 C and atmospheric hydrogen pressure. The product was separated into monoene, diene and triene fractions by countercurrent distribution. These fractions were further separated into various geometrical isomers. The double bond location in the various fractions was determined by reductive ozonolysis. Double bonds in bothcis andtrans monoene fractions, as well as incis,trans andtrans,trans conjugated dienes, were extensively isomerized. A monoene containing vinylic unsaturation was one of the major products. The nonconjugated dienes were mostly dienes whose double bonds were widely separated. Results are explained on the basis of conjugation of the double bonds in linolenate followed by hydrogen addition.