Thermal decomposition of mixed calcium oxalate hydrates – kinetic deconvolution of complex heterogeneous processes

Abstract

Whereas thermogravimetry monitors only a single-step CaOx decomposition reaction, DSC in addition reveals the complex competing CO oxidation kinetics.

Potentialities of mass spectrometry on activation energy and secondary reactions determination of calcium oxalate thermal decomposition

“…This enables to identify and quantify the volatile compounds CO and CO 2 evolving during this step, and, consequently, the contribution of the thermal effects of the indicated reaction within the global thermal balance of this II° event. These outcomes agree with the conclusions pointed out in an in‐depth analysis of the thermal behavior of the COM recently published 34 …”

“…The detection of CO 2 during the thermal decomposition of calcium oxalate unequivocally indicates the occurrence of a further secondary reaction during the second step. To the authors knowledge, this CO 2 formation, mentioned in some papers 30,34,55,56 is always led back to a partial (or total) oxidation of CO, yielded from reaction 2, following the stoichiometry: …”

“…In these studies, this is achieved by elaborating the TA information carried out, in particular, under constant heating rate constraint. 25,[31][32][33][34] Some of these works exploit the TA and MS techniques to identify the reaction mechanisms involved in the indicated steps. [35][36][37][38] As alternative approach, in this work, the E is determined, for each of the three reaction steps, by elaborating the MS signals through consolidated kinetic models as those of Kissinger, Ozawa, and Starink.…”

“…These outcomes agree with the conclusions pointed out in an indepth analysis of the thermal behavior of the COM recently published. 34…”

“…Focusing on proposals of item (1), it is well known that the thermal decomposition of COM, which occurs under an inert atmosphere following the three successive decomposition steps (Table 1), has been widely investigated in view of determining the values of E , preexponential factor, and kinetic model exponent. In these studies, this is achieved by elaborating the TA information carried out, in particular, under constant heating rate constraint 25,31–34 . Some of these works exploit the TA and MS techniques to identify the reaction mechanisms involved in the indicated steps 35–38 .…”