Kinetic analysis of isothermal, non-isothermal and catalysed thermal decomposition of malonic acid

A comparative study of the isothermal and non-isothermal decompositions of malonic acid has been carried out using the gasometric technique at atmospheric pressure. Under isothermal conditions, the results indicate two different mechanisms. At lower operating temperatures the decomposition process is governed by first-order kinetics, while at higher temperatures it is controlled by the random nucleation Erofeev equation. Analysis of the non-isothermal TG curves proved the advantageous use of this technique. It provides quick and valid information about the thermal decomposition kinetics of malonic acid, both in the pure state and when catalysed by solid 12-molybdophosphoric acid and its bismuth salts. Via the applicability of a non-isothermal kinetic equation, it was demonstrated that the factor causing the enhancement effect of these catalysts is mainly electronic in nature.