Hydrogen-deuterium Equilibration Research Articles

Hydrogen–Deuterium Equilibration over Transition Metal Sulfide Catalysts: On the Synergetic Effect in CoMo Catalysts

H2–D2 equilibration was used to study the synergetic effect between Co and Mo in carbon-supported CoMo sulfide catalysts. The reaction was carried out in a recirculation apparatus with continuous on-line analysis of all gas-phase components (H2, D2, HD, H2S, D2S, and HDS) by a mass spectrometer. The low reaction temperature (423 K) allowed for the first time a comparison to be made of the catalytic activity between Co sulfide particles in low-temperature sulfided (373 K) carbon-supported Co and those in standard sulfided (673 K) carbon-supported CoMo, which have similar 57Co MES parameters. On the basis of the much higher activity of the bimetallic catalyst than of the monometallic catalysts (Co and Mo sulfide) it is concluded that the observed synergy is related neither to the effect of the high dispersion of the Co sulfide nor seemingly to spillover effects as put forward by the remote control model. The results indicate that the sulfur atoms that bridge between Co2+ and Mo4+ play a crucial role during the catalytic cycle. During the equilibration reaction also extensive exchange takes place between hydrogen (deuterium) atoms adsorbed on the sulfided phase and hydrogen atoms present at the carbon support surface. This spillover process is accelerated by admixture of H2S, which most probably leads to an increase of terminal SH groups by dissociative H2S adsorption. These SH groups are thought to form hydrogen bridges with the carbon support functional groups. Both H2 and H2S compete for adsorption on the same coordinatively unsaturated sites. While heterolytic dissociation of H2 is considered to lead to a hydride and a bridging SH group between Co and Mo, heterolytic dissociation of H2S would lead to the formation of two SH groups, one bridging SH group and one terminal SH group active in forming hydrogen bridges with the support surface functional groups.

The catalysis of hydrogen-deuterium equilibration by platinum-gold cluster compounds

The catalytic effects of platinum and gold cluster compounds have been studied for H{sub 2}-D{sub 2} equilibration under homogeneous conditions as molecular solids.

Catalytic properties of superconducting YBa2Cu3O7?x ceramics in reactions of low temperature para-orthoconversion and hydrogendeuterium equilibration of molecular hydrogen

Etude de l'activite du catalyseur YBa 2 Cu 3 O 7−x . Cette ceramique est preparee a partir de BaO 2 , Y 2 O 3 et du Cu sous forme de poudre. Utilisation de la diffraction des rayons X

Enhancing effect of hydrogen on the catalytic activity of trisilver dodecatungstophosphate for the isomerization of 1-butene

The catalytic activity of trisilver dodecatungstophosphate (Ag 3PW 12O 40) for 1 -butene isomerization is reversibly enhanced by the presence of hydrogen in the gas phase at 304 K, indicating that on Ag 3PW 12O 40 hydrogen molecules are reversibly transformed into protons, which are active sites for this reaction. Hydrogen is adsorbed dissociatively and reversibly on the reduced form of Ag 3PW 12O 40. This was confirmed by hydrogen chemisorption, hydrogen—deuterium equilibration and the hydrogen—deuterium isotope effect on the rate of 1-butene isomerization.

Para-Hydrogen conversion and hydrogen-deuterium equilibration catalyzed by diamagnetic iridium, platinum, and ruthenium complexes in nonaqueous solution (1)

Homogeneous solutions of several tertiary phosphine complexes of Ir, Pt, Ru, and Rh have been tested for their catalytic activity for (1) para-hydrogen conversion, p − H 2 ⇄ o − H 2, and (2) hydrogen-deuterium equilibration, H 2 + D 2 → 2 HD. The experiments were carried out in toluene under 1 atm of hydrogen and between 25 and 65°C. The following results were obtained. (1) para-H 2 conversion: (a) active complexes: trans-[Ir(A)(CO)(Ph 3P) 2] (A = Cl, Br, or I), [Pt(Ph 3P) 4], {Pt(Ph 3P) n }, [Pt(O 2)(Ph 3P) 2], [Pt(Cl) 2(Bu 3P) 2], and [Ru(Cl) 2(Ph 3P) 3]; (b) inactive complexes: [Pt(PC 2P) 2], [Pt(PCCP) 2], and [Fe(DPGH) 2(py) 2]. (2) H 2-D 2 equilibration: (a) active complexes: trans-[Ir(A)(CO)(Ph 3P) 2], {Pt(Ph 3P) n }, and [Pt(O 2)(Ph 3P) 2]; (b) inactive complexes [Pt(Ph 3P) 4], [Pt(Cl) 2(Bu 3P) 2], and trans-[Rh(Cl)(CO)(Ph 3P) 2]. The H 2-D 2 catalysis by the iridium complexes was accompanied by an exchange between D 2 and some bound hydrogens in the reaction system. It is proposed that the para-H 2 conversion proceeds via a chemical mechanism through a dihydrido intermediate M(H) 2. The H 2-D 2 equilibration is tentatively proposed to involve a tetra-(hydrido-deuterio) species, M(H, D) 4, representing a labile intermediate or an activated complex. Alternate mechanisms for the H 2-D 2 equilibrium are considered, and their relative merits are discussed.

Studies of the surface of titanium dioxide: IV. The hydrogen-deuterium equilibration reaction

The interaction of hydrogen with the surface of titanium dioxide has been studied in connection with the hydrogen-reduction mechanism of titanium dioxide, by means of such measurements as weight decrease, magnetic susceptibility, hydrogen uptake, and electrical conductance. It was postulated in the previous study that the rate-determining step of the hydrogen-reduction reaction may be the formation of surface hydroxyl groups, followed by the rapid removal of water molecules from the surface. In this study, the interactions between hydrogen and the surface of titanium dioxide were investigated by measuring the hydrogen-deuterium equilibration reaction, H/sub 2/ + D/sub 2/ = 2HD, at temperatures above 200/sup 0/C on both surfaces before and after hydrogen reduction to compare the differences in the reactivities.

Hydrogen-Deuterium Equilibration Reaction over Platinum Supported on Polyamide-6

Abstract Catalysis by platinum supported on polyamide-6 was examined for the H2-D2 equilibration reaction at 0 °C in the pressure range of 5–20 Torr (1 Torr=133.3 Pa). Three kinds of polyamides with different molecular weights were prepared as support; the concentration of platinum varied from 0.5 to 2.7 wt%. With preadsorption of hydrogen at 0 °C, the rate of the reaction was found to increase up to 10 times as high as the original level. The rate km (HD molecule s−1Pt atom−1) showed a maximum, depending on surface area of the polyamides used, in the range 0.8–1.0 wt% of Pt content and its dependence on total pressure is represented by km=K1P⁄(1+K2√‾P)2 irrespective of Pt content. No significant isotope effect was observed at 0 °C. It was found that a linear relationship exists between the enhancement of km and the amount of hydrogen preadsorbed, indicating an important role of the preadsorbed hydrogen in activation of the catalysts. In contrast to km, the turn-over frequency kt (HD molecule s−1 site−1) was nearly independent of Pt concentration. The exchange reaction is explained in terms of the Bonhoeffer-Farkas mechanism. XPS spectra provided the evidence for the presence of Pt(II) complexes on the surface. The structure of active sites is discussed.

Hydrogenation of 1, 3-Butadiene over LaCo5Nn

We have recently found that LaCo5 absorbs a considerable amount of nitrogenin an atomic form above about 250° C. The absorbed nitrogen is hardly desorbed from LaCo5 below 350° C. In the present study, several samples of LaCo5 Nn, (n=0, 0.06, 0.10, O.18 and 0.24) were prepared and the hydrogenation of 1, 3-butadiene was conducted over the LaCo5 Nn catalystsinthe temperature range-65 to-40°C. With the increase in n, the hydrogenation rate increased remarkably and the change of composition of the products from 1-butene-rich to 2-butene-rich (trans-2-butene cis-2v-butene) took place.The isomerization and hydrogenation reactions of 1-ndash; butene were also conducted over the LaCo5 Nn catalysts under similar conditions. The rate of the hydrogenation increased remarkably with the increase in n, while the rate of the isomerization was not affected by n. The hydrogen-deuterium equilibration reaction hardly took place during these hydrogenation reac-ndash; tions. These results led to the conclusions that the rate-determining step of these hydrogenations

The activity of reduced chromia on silica catalysts for the hydrogen-deuterium equilibration at low temperature

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe activity of reduced chromia on silica catalysts for the hydrogen-deuterium equilibration at low temperatureV. Indovina, A. Cimino, and M. InversiCite this: J. Phys. Chem. 1978, 82, 3, 285–289Publication Date (Print):February 1, 1978Publication History Published online1 May 2002Published inissue 1 February 1978https://doi.org/10.1021/j100492a007RIGHTS & PERMISSIONSArticle Views32Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (738 KB) Get e-Alerts

Catalysis of benzene deuterium exchange, and related reactions over NiX and NiY

Benzene deuterium exchange, and hydrogen deuterium equilibration were studied over a range of catalysts prepared by nickel ion exchange with samples of X, Y and intermediate composition, faujasite type zeolites. Experiments were also carried out on the water poisoning of both reactions. The results obtained were almost independent of the silicon to aluminum atom ratio in the zeolites. A mechanism which involves the heterolytic splitting of deuterium or hydrogen is proposed to explain both reactions. The active sites are thought to be associated with nickel ions located on the exterior faces of the crystallites.

Effect of ion bombardment on adsorption and exchange reaction of hydrogen by evaporated nickel films

The effect of an activating treatment of evaporated films of nickel has been investigated by hydrogen adsorption and hydrogen-deuterium equilibration reaction in the pressure range 10 −6-10 −3 Torr at room temperature. Adsorbed hydrogen can be divided into reversible and irreversible parts. The former can be removed easily by pumping at near room temperature, while the latter cannot. A Freundlich isotherm fits the reversible adsorption data while the irreversible adsorption is best described by a Langmuir isotherm (with dissociation). Argon ion bombardment gave drastic increase in hydrogen adsorption, although the surface area of the nickel film measured by xenon adsorption showed no change with either ion bombardment or annealing. The rate of equilibration was found to obey the rate law, V = kP 1.3 after either ion bombardment and annealing (the values of k were exactly the same on both the films). It is concluded that the rate of the equilibration is controlled by the reaction step, 2 H(a) irr + D 2(a) rev = 2 HD, and that only a small part of the dissociative hydrogen which is irreversibly adsorbed appears effective in the equilibration reaction near room temperature. It is also concluded that on these particular sites, there are no effects of bombardment or annealing on the overall rate of the equilibration near room temperature.

The Kinetics and Mechanism of Hydrogen Adsorption and Hydrogen–Deuterium Equilibration on the Copper Surface

Abstract The mechanism of H2–D2 equilibration reaction over the copper surface was studied in the 40–90 °C range of temperature and in the pressure range of 4–45 Torr. From the studies of the hydrogen adsorption and the reaction between gaseous deuterium and preadsorbed hydrogen, the reaction was confirmed to proceed via combination between hydrogen and deuterium atoms on the surface. The rate constants for the adsorption and the desorption were optimized by a computer simulation of the reaction-time course and were found to be in satisfactory agreement with the observed results. A marked isotope effect was found in these rates; its influence on the partial pressure dependence of the reaction was discussed.

Mechanism of Hydrogen Adsorption and Hydrogen-Deuterium Equilibration on Copper Surface

Behavior of hydrogen and deuterium on copper surface was studied in detail. Desorption spectra, adsorption isotherms and the kinetics of exchange reaction predicted that hydrogen is adsorbed dissociatively and the H2–D2 equilibration proceeds via the recombination between adsorbed atoms. The optimum values of rate constants for adsorption and desorption were determined by simulating the reaction time course. Obtained constants were found to coincide with those derived by the transition state theory. Influence of molecular motion on adsorption was examined by analyzing the computed trajectories of hydrogen on a dual Cu site.

Comparison of the Catalytic Activities of Metal Oxides for Hydrogen-Deuterium Equilibration and Ortho- Parahydrogen Conversion

Abstract The corrected activities, rates divided by square of spin magnatic moment of a metal ion, in ortho-parahydrogen conversion on first series transition metal oxides at 77°C were shown to give a very similar activity pattern to that obtain in hydrogen-deuterium equilibrtation.

Catalytic activity of organic semiconductors. Hydrogen conversion on triphenylene-alkali metal ion radical salts

An extensive study was made of the kinetics and the mechanism of the orthoparahydrogen conversion, the deuterium exchange reaction, and the hydrogen-deuterium equilibration over solid triphenylene-alkali metal ion radical salts (K-, Rb-, and Cs- salts). Two species, mono- and dinegative anion salts, were stoichiometrically prepared. Two different reaction paths, one through the chemisorption process and the other via the exchange process, were observed. With simultaneous measurements of the rate of hydrogen adsorption and also of the time course of ortho-parahydrogen conversion on the salt catalysts, a novel kinetic analysis, based on the two processes, was presented. In comparing these processes, the chemisorption process was found to be predominant in every reaction over the complexes in question. Further, it was observed that the catalytic activity depends strongly on the valency of anions and on the sort of alkali metal; the rate constant of the dianion salt was much larger than that of the monoanion salt, and the activity increased in the order of K, Rb, and Cs.

Hydrogen-deuterium equilibration reaction catalysed by graphite-potassium compounds

The activity pattern of the series of graphite–potassium compounds for the H2–D2 equilibration reaction was found to be C24K>C36KC8K-hydride C8K ∼ 0.

Catalytic activity of organic semiconductors and enzymes.

The catalytic activity and reactivity of the charge-transfer complexes and the ion radical salts have been investigated by means of the ortho-parahydrogen conversion, the deuterized reaction and the hydrogen-deuterium equilibration. The predominant reaction on the aromatics-alkali metal ion salt occurred through a chemisorption mechanism. These findings were confirmed by the electrical conductivity and also the photoemission measurements of unexposed and hydrogen-exposed ion salts. Hydrogenase activity in the dry state is also discussed.

Parahydrogen conversion on 5A molecular sieve and 5A molecular sieve containing neodymium ions

Parahydrogen conversion on 5A molecular sieve and 5A molecular sieve containing neodymium ions has been investigated over the temperature range 77–605 °K. Rates of orthodeuterium conversion at low temperatures and hydrogen-deuterium equilibration at high temperatures have been measured in order to interpret the mechanism of reaction. At low temperatures, conversion proceeds by a physical mechanism in which the activity is determined by paramagnetic impurities and neodymium ions. At high temperatures, conversion proceeds by a chemical mechanism, and both catalysts exhibit a pronounced activation effect on exposure to hydrogen. The low temperature activity is unaffected by the hydrogen treatment.

Sites active for catalytic hydrogen-deuterium equilibration over .alpha.-chromia

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSites active for catalytic hydrogen-deuterium equilibration over .alpha.-chromiaPierce W. SelwoodCite this: J. Am. Chem. Soc. 1970, 92, 1, 39–49Publication Date (Print):January 1, 1970Publication History Published online1 May 2002Published inissue 1 January 1970https://doi.org/10.1021/ja00704a007RIGHTS & PERMISSIONSArticle Views120Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Hydrogen reaction mechanisms on TiO 2

A kinetic study of the ortho-para hydrogen conversion and the hydrogen-deuterium equilibration reaction was made on the anatase form of TiO 2, over the temperature range 93 ° to 773 °K. The products of the conversion reaction were analyzed by microthermal conductivity and those of the equilibration reaction by mass spectrometry. Three distinct temperature regions of activity were found and the results are discussed in terms of a low-temperature physical mechanism, a high-temperature chemical mechanism, and the nature of the surface sites on TiO 2.