Esterification of acetic acid by isoamylic alcohol over catalytic membranes of poly(vinyl alcohol) containing sulfonic acid groups

In this study, poly(vinyl alcohol) (PVA) membranes crosslinked with sulfosuccinic acid (SSA) were used for the esterification of acetic acid by isoamylic alcohol. In order to study the effects of the crosslinking degree and, simultaneously, the amount of sulfonic groups, different membranes were prepared with SSA:PVA ratios in the range of 5-40 mol%. Aiming at to eliminate the dependence between the amount of acid sites and the crosslinking degree, were also prepared PVA membranes in which the -SO₃H groups were introduced by anchoring 5-sulfosalisilic acid (SA) on the PVA chains. The conversion of isoamylic alcohol increases when the amount of sulfosuccinic acid used in the polymer crosslinking is increased from 5 to 20%. However, when crosslinking degree increases from 20 to 40%, the conversion of isoamylic alcohol increases only slightly, probably due to the increase of molecules mobility restrictions, in the PVA matrix. In the case of the PVA membranes where the -SO₃H groups were introduced by esterifying 5-sulfosalisilic acid on the PVA -OH groups, it was observed that membrane activity increases with the polymer crosslinking. It was also observed an increase of the activity of these membranes with the amount of -SO₃H groups in the polymeric matrix. Catalytic stability of PVA membranes, prepared with SSA and SA, was evaluated by performing consecutive batch runs with the same membrane being observed, after the third run, a trend to stabilization of catalytic activity. An experiment with a membrane reactor operating under sweep gas pervaporation conditions is described.