Kinetic and FT-IR study for the mechanism of addition of hydrogen sulfide to methyl acrylate over solid basic catalysts

Addition of H2S to methyl acrylate was performed in a batch reactor at 413 K, 400 rpm and at different concentrations in methyl acrylate and H2S in the presence of a commercially available mixed magnesium-aluminum, basic oxide, namely the KW 2200 catalyst. Under chemical regime, the rate law was shown to follow a "poisoned" Eley-Rideal mechanism in which H2S reacts in the adsorbed state, whereas methyl acrylate, also capable of being adsorbed on the catalyst, would react in a physisorbed state. FT-IR study of methyl acrylate and H2S adsorption performed on MgO are in agreement with these kinetic results. Co-adsorption experiments showed that both methyl acrylate and H2S were strongly adsorbed on MgO. By varying the order of introduction of the two reactants, i.e. adsorption of H2S followed by methyl acrylate addition or methyl acrylate adsorption followed by H2S addition, it was shown that chemisorbed H2S species like HS- species which result from H2S dissociative adsorption were the active species and that strongly adsorbed methyl acrylate was not involved in the reaction. (C) 2002 Elsevier Science B.V. All rights reserved.