Browsing by Author "Primet, Michel"

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    Infra-red Determination of the Isotherm of Hydrogen Adsorption on a Pt/Al2O3 Catalyst
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Primet, Michel; Basset, Jean-Marie; Mathieu, Michel-Vital
    Of the various forms of hydrogen adsorbed on platinum only hydrogen weakly and reversibly adsorbed is detected by an infra-red band at 2120 cm-1. The preparation of a well dispersed sample of Pt/ALO? catalyst containing 10 % platinum allows us to determine accurately the hydrogen adsorption isotherm of this weakly adsorbed species. Only a dissociative Langmuir model fits the experimental results in the pressure range of 10'1 to 700 Torr and temperature range of 27 to 95°C. The heat of adsorption (—5 x 104 J mol-1) and the isosteric heat of adsorption are in good agree ment with previous calorimetric data.
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    Infrared Study of CO Chemisorption on Zeolite and Alumina Supported Rhodium
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Primet, Michel
    The chemisorption properties of supported rhodium with respect to carbon monoxide are investigated by infrared spectrometry. Zeolite and alumina supported rhodium is obtained following hydrogen reduction. Highly dispersed rhodium is prepared on the zeolite support whatever the temperature of reduction over the range 200–600°C. For rhodium supported on alumina, the dispersion is less good and decreases when the conditions of reduction become more drastic. For particles of larger diameter than 20 Å, chemisorption of CO leads mainly to gem dicarbonyl species, the site of adsorption being one rhodium atom in the oxidized state. These gem dicarbonyl complexes are not formed at low temperature, but develop on warming up to room temperature. Dissociation of carbon monoxide is then assumed, CO in excess adsorbs on the surface Rh–O species to give gem dicarbonyl complexes, probably of RhI, which interact with the lattice in the case of zeolite support.