Investigation of thermal decomposition of ascorbic acid by TG-FTIR and thermal kinetics analysis

The thermal behavior of dry solid ascorbic acid in nitrogen atmosphere in the temperature range of 25-800 degrees C was investigated by TG-FTIR. During the thermal decomposition process, five evolved gaseous species, including H2O, CO2, CO, CH4 and HCOOH, were identified and monitored, in which HCOOH was detected for the first time. The results indicated that ascorbic acid began to decompose at 191 degrees C. Its decomposition process consisted of three stages, and dehydration and decarboxylation to form furfural were the possible principal mechanism. The kinetic analysis for the first decomposition stage was also carried out by the isoconversional method and the master plots method. The results indicated that this process can be described by the model of 1st order reaction. (c) 2013 Elsevier B.V. All rights reserved.