Decomposition of tributhyl phosphate at supercritical water oxidation conditions: Non-catalytic, catalytic, and kinetic reaction studies

Abstract

Tributhyl phosphate (TBP) decomposition in supercritical water oxidation (SCWO) was performed with and without catalyst, at different temperatures ranging from 370 to 480°C, and different reaction times. Ag2O, CuO, Fe2O3, MgO, and ZnO synthesized by supercritical water were examined in TBP decomposition as the catalyst. TBP structure decomposed under the non-catalytic reaction; nevertheless, the results indicated that the use of catalysts improved the reaction efficiency, which calculated based on total organic carbon (TOC) removal, by far. However, TOC removal using Fe2O3 was 20% higher than the non-catalytic reaction. Having the ability in completion of the redox cycle, iron oxide catalytic nanoparticles preserve their stability and performance when used in a sequential TBP decomposition experiment. As for the estimation of the reaction rates, the kinetic constants were evaluated. Possessing a high predictive power with the accuracy more than 90%, the proposed kinetic equations can be applicable for further studies dealing with the TBP decomposition adopting SCWO.