Oxidation of ethylene at a palladium electrode

Abstract

The electrochemical oxidation of ethylene to acetaldehyde and carbon dioxide is investigated at a palladium electrode in 2 N sulphuric acid at 8O"C, as a first step towards the partial oxidation of higher olefins. Results on the corrosion of a palladium electrode in the absence of ethylene show features not previously reported, and a possible mechanism is given to account for the results. In the presence of ethylene at electrode potentials above 0.75 V EH, it is shown that two reaction schemes are likely to be in operation to' account for the products observed, as well as the appearance of a considerable amount of palladium metal in the electrolyte. / Preparative runs were carried out in the larger cell. In this case the anode was folded into a W shape to get a large surface area. The anolyte was stirred by gas bubble agitation.Both cells had platinum counter electrodes. 912889

The electrodissolution of base palladium in relation to the oxygen electroadsorption and electrodesorption in sulphuric acid solution

“…Reactions (4b) and (6) denote complex overall reactions where ageing, disproportionation and peroxide formation processes discussed in a previous publication [13] are not considered here. This reaction pathway (3)(4)(5) is, in principle, formally similar to that proposed for the stationary and non-stationary electrodissolution of many metals in aqueous acid electrolytes [25]. The non-stationary electrodissolution of palladium occurs, however, in three potential regions related to the electroformation of oxygen-containing species [7,13], as expressed by the following overall reactions:…”

Criteria for selective path promotion in electrochemical reaction sequences

“…The same equations apply to the gas phase convective transport and reaction of gaseous reactants that are in local equilibrium with the electrolyte. Such gas-catalyst-electrolyte reactions are often encountered in fuel cells (Bockris et al, 1965;Vielstich, 1970) and in elertrogenerative processing (Goodridge and King, 1970;Langer and Landi, 1963; Sakellaropoulos and Langer, 1 9 7 6~) . In this case, Cjo and Cj, are the gas phase concentrations, while Tcm is evaluated at the liquid concentration Cjcl) of each species (Sakellaropoulos and Francis, 1979u, b ) .…”

“…Figure 9 exemplifies this behavior for an irreversible oxidation reaction with a relatively slow second step. This system is quite typical of the electrocatalytic oxidation of hydrocarbons and alcohols in fuel cells (Vielstich, 1970) or of selective oxidations to aldehydes (Goodridge and King, 1970).…”

Instrumental effects on in situ electrochemical STM studies: An investigation of a current surge induced Pd deposit on HOPG

“…Taking into account the amount of charge passed both by the surge and in the anodic treatment, the fact that a substantial amount of the Pd deposit still remained undissolved (Figures 2 and 3) again provides an indication of a considerable degree of irreversibility (Goodridge and King, 1970;Tong et al, 1995) even though anodic Pd dissolution is favoured in acid electrolytes containing C1- (Goodridge and King, 1970;Sashikata et al, 1991).…”