Adsorption and conductivity studies in oxychlorination catalysis. Part 2.—Gas-adsorption chromatography with catalytic copper(I, II) chlorides
- 1 January 1984
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 80 (10) , 2785-2802
- https://doi.org/10.1039/f19848002785
Abstract
Gas-adsorption chromatography has been used to calculate adsorption isotherms and isosteric heats of adsorption (qst) for the reactants and products of oxychlorination at low coverage on CuCl2 and CuCl. The heat of adsorption at zero coverage of ethylene on CuCl2 is 65 ± 5 kJ mol–1, indicating chemisorption. On CuCl, ethylene is only physically adsorbed (qst= 13 kJ mol–1, heat of liquefaction = 14.45 kJ mol–1). The adsorption of C2H4 is shown to be unaffected by the alumina support or by oxygen, but an excess of HCl appears to decrease the adsorption. The unsaturated nature of the adsorbate is evidently a vital factor; ethane and 1,2-dichloroethane give heats which are close to the heats of liquefaction, but with ethylene and propene (55 kJ mol–1) the heats are considerably higher and with acetylene and buta-1,3-diene chlorination occurs. The technique of gas-adsorption chromatography is successfully extended to the injection of liquids at sufficiently high temperature that vapourisation is instantaneous. The heat of adsorption of water vapour on CuCl2 is 64 kJ mol–1(the heat of liquefaction is 40.6 kJ mol–1).Keywords
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