Kinetic and Thermodynamic Study of Corncob Hydrolysis in Phosphoric Acid with Low Yield of Bacterial Inhibitors

Abstract

In this work, high sugar yield and low bacterial inhibitor production in dilute phosphoric acid hydrolysis of corncob is reported, with 54.3 g of sugar/100 g corn cob the highest yield observed at the most severe conditions with a degradation factor of only 0.03. Hydrolyses were obtained at different acid concentrations, temperatures and reaction times to analyse the effect of these variables on sugar production and degradation into bacterial inhibitors. The paper focuses on the kinetics and thermodynamics of corncob phosphoric acid hydrolysis, a topic scarcely studied. Kinetic constants calculated from either Saeman or first-order models allowed us to determine thermodynamic parameters and understand the energetic changes during hydrolysis. Sugar production has anactivation energy of 52 kJ mol−1 and sugar decomposition 78 and 115 kJ mol−1. Fourier Transform Infrared Spectroscopy analyses showed that sugar production came mainly from hemicellulose degradation.