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    Carbonylation of Methanol and Ethanol on a Rhodium-Zeolite Catalyst
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Christensen, Bjarne; Scurrell, Michael S.
    The carbonylation of methanol and ethanol on a rhodium-X zeolite has been studied. Particular emphasis has been placed on the effect of the concentration of the required alkyl iodide “promoter” on the selectivity of the reaction. A maximum in selectivity for carbonylation is observed for both alcohols as the alkyl iodide content of the reactant stream is increased. The side products are dimethyl ether and ethylene with methanol and ethanol respectively. Some comparative experiments with either rhodium-on-carbon or the unmodified NaX support show that at least for ethanol the zeolite support offers a sufficiently high activity to account for the rate of formation of side product under carbonylation conditions. For methanol carbonylation the necessity to employ near-stoichiometric quantities of methyl iodide and the effects which the absence of “promoter” has on catalyst behaviour are discussed. Comparison between the action of rhodium catalysts in homogeneous and heterogenised forms leads to the conclusion that close similarities in behaviour exist, probably due to the operation of a common mechanism.
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    Adsorption of Carbon Monoxide by Zeolite Y Exchanged with Different Cations
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (1), 1973) Egerton, T. A.; Stone, F. S.
    Adsorption of carbon monoxide has been studied on Zeolite Y in which Na* ions have been partially exchanged for Zn2+, Mn2\ Co2+, Ni2% Cu2+, Ba2+, UOf and Cc3+ ions. The divalent ions all produced sites for specific CO adsorption, even at low degrees of exchange. Thus, unlike Ca2^ studied in earlier work, these ions do not have a total preference for internal sites in the prisms or sodalite units inaccessible to CO. At approximately 30 % exchange the affinity of divalent ions for internal sites decreases in the order Ca2+ > Ni2i, Mn2+, UOr > Cu2+ > Zn2+. However, even on the Zn-exchangcd Y, only about 1 divalent ion in 10 acts as a site for specific adsorption of CO. Very little CO was specifically adsorbed on Ce-exchanged Y, even at high degrees of exchange. This confirms that cerium ions favour internal sites. With ZnY, MnY, BaY and CeY, CO adsorption was rapid and reversible. Isosteric heats were evaluated and, except for CeY, were substantially greater than on uncxchanged NaY, confirming the presence of specific adsorption. The heats correlate with the electrostatic field strengths of the cations and with the shifts of the C—O stretching frequency on adsorption. With NiY and CuY, adsorption was slow and is thought to reflect a gradual increase in the number of adsorption sites caused by adsorbate-induced migration of divalent cations. A number of the systems studied in this work have not previously been investigated from the standpoint of cation location. However, where comparisons arc possible, the present results derived from CO adsorption are shown to be in good agreement with those from other methods.