Hydrolysis and oxidative decomposition of ethyl acetate in sub- and super-critical water

Abstract

Hydrolysis of ethyl acetate in sub-critical (633K, 200bar) and super-critical water (673K, 240bar) has been investigated in a tubular flow reactor as a model reaction for the depolymerisation of polyesters. Super-critical reaction conditions enable approximately a 10-fold hydrolysis rate in comparison to sub-critical process. The reaction products ethanol and acetic acid are stable under these conditions. Additionally, oxidative decomposition experiments were carried out using ethyl acetate, ethanol and acetic acid as feed in the presence of air, non-catalysed as well as in the presence of a heterogeneous MnO2–CuO/Al2O3 catalyst (Carulite 150®). The catalyst caused only slight increase of ethyl acetate conversion in oxidation compared to hydrolysis, but a noticeable increase in CO2 formation due to destruction of ethanol and acetic acid. In absence of catalyst, the degrees of conversion and selectivities were not affected by addition of oxygen. Fresh and spent catalysts were characterised with standard methods (BET, ICP), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalyst material was identified as chemically and mechanically stable under the applied reaction conditions, however, a significant sintering accompanied by a deep structural alteration and a slight reduction were observed. Additionally, the stability of reactor material regarding to corrosion was also tested.