New insights into the thermal behavior and decomposition of sodium propionate

摘要

Na-propionate (NaC2H5CO2) was synthesized from Na2CO3 dissolved in propionic acid. Its thermal behavior was studied in argon and in air. In both atmospheres, two solid-solid phase transitions occur below 250 degrees C and are followed by melting near 290 degrees C. Thermal decomposition begins with release of CO2 attributed to the decomposition of a limited amount of propionyl radicals. Elemental carbon results from this process. This initial reaction is followed by a faster conversion reaction into Na2CO3 with evolution of 3-pentanone, CO2, CO, CH4 and C2H4 as found during pyrolysis in argon. In air, oxidative decomposition takes place with CO2 and H2O as main released gases. The stability of Na-propionate is reduced in air compared to argon atmosphere. The reaction paths are discussed and compared with previously published results on Na-propionate and other propionate metalorganic compounds. The potential of using the low temperature phase transitions of Na-propionate for thermal energy storage (Delta H approximate to 245 J/g) was evaluated by submitting samples to 25 heating/cooling cycles.