Complete Kinetic and Mechanistic Decomposition of Zinc Oxalate with Characterization of Intermediates and Final Oxide

Nicholas D. Cooper

Abstract


Although the thermal decomposition of zinc oxalate was considered to follow a one-step mechanism, newer isoconversional methods indicate that the activation energy is a function of the extent of reaction and of the sample mass.  This suggests that the mechanism may actually have several steps.  Evolved gas analysis indicates that the gaseous products, CO and CO2, are produced at different rates supporting the conclusion from the isoconversional investigations. EGA indicates that CO is formed initially while CO2 forms later.  These results are consistent with the mechanism proposed by Boldyrev.1 He proposed that the initial step in the mechanism is an oxalate anion rearrangement to produce a carbonate-carbonyl intermediate.  This intermediate then loses CO to produce the carbonate.  Decomposition of the carbonate then produces the CO2.  No evidence for this intermediate has been found using either X-Ray diffraction or FTIR spectroscopy.


Keywords


Zinc; Oxalate; Thermal Decomposition; Isoconversional Methods; Mechanism

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