Hydroformylation of ethylene via spontaneous cell reactions in the gas phase
- Tokyo Institute of Technology, Meguro-ku (Japan)
A new method for the hydroformylation of ethylene using a gas cell composed of (C{sub 2}H{sub 4}, CO, cathode {vert_bar}H{sub 3}PO{sub 4} aq.{vert_bar} anode (Pt-black), H{sub 2}) has been examined at ca. 373 K and atmospheric pressure. Among many cathode electrocatalysts tested, H{sub 2}PtCl{sub 6} showed the highest selectivity and high activity for the formation of C{sub 2}H{sub 5}CHO. However, H{sub 2}PtCl{sub 6} did not catalyze the reaction at all under a gas mixture of C{sub 2}H{sub 4}, CO, and H{sub 2}. H{sub 2}PtCl{sub 6} was specifically active for the electrocatalytic hydroformylation by separating H{sub 2} from C{sub 2}H{sub 4} and CO with a H{sub 3}PO{sub 4}-electrolyte membrane. The addition of Na{sub 3}PO{sub 4} to the cathode enhanced the rate of C{sub 2}H{sub 5}CHO formation as well as the selectivity. The cell reaction does not require electrical energy input but takes place spontaneously and most efficiently under short-circuit conditions. The results from kinetic and electrochemical studies have suggested that the catalytic active species is the Pt{sup 2+}-chloride supported on the host graphite. A stronger coordination of CO compared to those of C{sub 2}H{sub 4} and hydride reduces both the hydrogenation and hydroformylation of C{sub 2}H{sub 4}. Therefore, a low partial pressure of CO and higher partial pressures of C{sub 2}H{sub 4} and H{sub 2} are recommended for the conversion of C{sub 2}H{sub 4}. The optimum temperature for the hydroformylation was 373 K. The results of transition response experiments have suggested a rapid reversible coordination of C{sub 2}H{sub 4} but a slow conversion of the precursor of C{sub 2}H{sub 5}CHO on Pt{sup 2+} the sites. A tentative reaction mechanism assuming the formations of ethyl-carbonyl, ethyl-carbonyl hydride and acyl-carbonyl Pt complexes has been proposed on the bases of the results in this work. 15 refs., 13 figs., 2 tabs.
- OSTI ID:
- 476806
- Journal Information:
- Journal of Catalysis, Vol. 165, Issue 2; Other Information: PBD: 15 Jan 1997
- Country of Publication:
- United States
- Language:
- English
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