Calorimetric heats of sorption of gases on evaporated iron films

Abstract

Heats of sorption of hydrogen, carbon monoxide, nitrogen and oxygen on evaporated iron films have been determined calorimetrically ; in addition, the heats of sorption of some of these gases on films partially covered with another gas have been obtained. It is found that the sorptive ratio of carbon monoxide to hydrogen at 0.1 mm pressure is 1-60, and not 2 as previously suggested. Boudart's induced heterogeneity theory to account for the decrease of heat of sorption with coverage is shown to be invalid. Some possible applications to catalytic problems are briefly discussed.

Structure and Surface Chemistry of Industrial Ammonia Synthesis Catalysts

“…Preadsorbed CO inhibits Hz chemisorption [207,406], but has no effect on the enthalpy of chemisorption for Hz [389].…”

“…Preadsorbed N * has been reported to decrease [207,416,406,414] or to increase [417] the amount of chemisorbed hydrogen. Preadsorbed N * has been found to decrease [389], to increase [394] or to have no effect [414] on the heat of adsorption for Hz [389]. Presumably, the results of the coadsorption of N * and H * depends sensitively on the experimental conditions as both displacement to the gas phase and the formation of NH3 are realistic possibilities.…”

“…The enthalpy of chemisorption for CO on Fe surfaces is -9.3 to -4.2 kcaljmole at O°C [439] on (Fe, AI), -23.1 to -16.9 kcaljmole at O°C [439] on (Fe, AI, K), -8.0 to -4.2 kJ/mole at -183°C [439] on (Fe, AI, K), and -32 kcaljmole at 22°C [389] on (Fe, AI, K). For Fe supported on Alz03 a Freundlich isotherm has been found [160].…”

“…Preadsorbed N * partially inhibits CO chemisorption [207,447,448] and decreases the heat of adsorption for CO at 32°C [389].…”

“…For hydrogen adsorption on polycrystalline Fe, the enthalpy of chemisorption has been determined as -98 kJ/mole by calorimetry [385], -96 kJ/mole by calorimetry [386], -81.0 kJ/mole by electrical conductivity [387], -85.0 kJ/mole by volumetric chemisorption [388], -36 kcaljmole at zero coverage by volumetric chemisorption [389], -15 kcaljmole at 90% saturation [389], -20 kcaljmole at 140 K, zero coverage [390], -17.5 kcaljmole at 1 % of saturation calculated from the equilibrium pressure [391], and -5 kcaljmole at 10% of saturation calculated from the equilibrium pressure [391].…”