ADSORPTION OF SODIUM MALEATE IN THE COURSE OF ITS HYDROGENATION ON SKELETAL NICKEL IN AQUEOUS-SOLUTIONS AND ITS INFLUENCE ON THE REACTION-RATE

The specific features of adsorption and the kinetics of hydrogenation of sodium maleate on skeletal nickel in aqueous solutions at various p H were studied by adsorption calorimetry under in situ conditions. The isotherms of adsorption and the enthalpy of adsorption of the hydroge nated compound were derived. The dependences of the hydrogenation rate on the reagent concentration in solution and on its adsorption on the catalyst surface were found. The reaction rate was shown to be propor tional to the coverage at the reagent concentrations below 5 x 10(-3) mol/l; the linearity was disturbed within the concentration range (5-9 )x 10(-3) mol/l; the rate of hydrogenation became independent of the c overage at concentrations above 10(-2) mol/l. Such behavior was explai ned by the complicated character of adsorption of the hydrogenated com pound, in particular, by the mechanism of filling of the catalyst pore volume during adsorption.