Oxalate - Hydrogen Peroxide - Water Ternary Phase Equilibrium And Peroxy Potassium Oxalate Thermal Decomposition Kinetic Study

Perhydrates are of considerable technical importance as carriers of hydrogen peroxide. Metal oxalate perhydrates are a new series of perhydrates , like other perhydrates, which are a type of inorganic salt adduct with hydrogen peroxide. These perhydrates have the same properties as hydrogen peroxide,e.g. washing, bleaching, and bactericidal effect, nontoxic and tasteless, moderate performance, and pollution-free. It can be used as source of oxygen, food preservative, oxidizers and other metal surface treatment agent.The preparing process of M₂C₂O₄·H₂O₂(M=K, Na, NH₄)are based on the phase diagram of the ternary M₂C₂O₄-H₂O₂-H₂O(M=K, Na, NH₄)system. We have found no data on the solubility or phase diagram for the ternary M₂C₂O₄-H₂O₂-H₂O(M=K, Na, NH₄)system in the literature. It is very important to study the system and construct the phase diagram of the ternary M₂C₂O₄-H₂O₂-H₂O(M=K, Na, NH₄)system. In this paper, the ternary system K₂C₂O₄-H₂O₂-H₂O and Na₂C₂O₄-H₂O₂-H₂O and(NH₄)₂C₂O₄-H₂O₂-H₂O were studied at a temperature of 283 K and 293 K, respectively. These phase diagram of ternary systems were constructed. The preparation technics of the oxlate perhydrates was studied, and ternary system phase diagarm was calculated theoretically. The effects of the reaction temperature and ratio of raw materials on the yield of the oxlate perhydrates were discussed.The system oxalate M₂C₂O₄(M=K, Na, NH₄)-hydrogen peroxide-water is a representative electrolyte-nonelectrolyte system, especially which includes unstable hydrogen peroxide. The empirical equation put forward by Beutier and Renon was applied to hydrogen-peroxide system, which is described asThe parameters value ofλAA andμAAA are obtained via regression using saturated vapor pressure of the hydrogen peroxide aqueous solution. Based on the results, the solubility data of the system oxalate M₂C₂O₄(M=K, Na, NH₄)-hydrogen peroxide-water were calculated and correlated using Pitzer equation, and the Pitzer parameters are obtained. Calculated value were well agreement with experimental data. Meanwhile, the solubility product constant of adducts at 283K and 293K are acquired, respectively. The results of regression and calculation of the ternary system provide fundamental data for designing and optimizing the preparing process of the metal oxalate perhydratesThe adducts K₂C₂O₄·H₂O₂ were characterized via infra-red spectrum and X-ray powder diffraction. Thermal analysis was further carried to investigate the thermal decomposition kinetics of the prepared adduct of K₂C₂O₄·H₂O₂ using both TG-DTG and DSC techniques with constant heating rate in nitrogen. The analysis results showed that the decomposition temperatures of the product measured were 405.48 K in nitrogen, The activity energy of thermal decomposition of K₂C₂O₄·H₂O₂ in nitrogen was obtained using Ozawa-Flynn-Wall(OFW) method, Kisinger-Akahira-Sunose(KAS)method without involving any decomposition mechanism of solid state. The multivariate non-linear regression is employed to optimize the activity energy. The activity energy of thermal decomposition of K₂C₂O₄·H₂O₂ was 119.5 KJ·mol^-1 in nitrogen.