Process-product studies on starch acetylation reactions in pressurised carbon dioxide

An in-depth study on the effect of process conditions (pressure, temperature and type of catalyst) on the acetylation of starch with acetic anhydride in pressurised carbon dioxide is described. A total of 22 experiments were performed and the experimental data were analysed using non-linear multivariable regression. The highest degree of substitution (DS) value (0.46) was obtained using K(2)CO(3) as the catalyst at 90 degrees C, 15 MPa pressure, and a catalyst to starch ratio of 0.5 mol/mol anhydroglucose units (AGUs). Important product properties of the acetylated starch prepared in CO(2) like viscosity in water and relevant thermal properties were determined and compared with typical products prepared in an aqueous system.