Glucose is used in pharmaceutical applications as a filler and binder for tablets and sweetening agents. The thermal decomposition of Glucose is investigated by means of thermogravimetric analysis.  

Conditions of Measurements

Thermal decomposition of Glucose
The first thermal decomposition step produces mainly water. The mass loss of this step is independent from the heating rate. The mass loss of the second thermal decompostiton step of Glucose, however, is strongly dependent on the heating rate. This is sufficient proof that after the first step the later decomposition follows at least two competing reaction paths. 
Already now a proposal can be given for the kinetic model of the whole thermal decomposition process of Glucose (see result of model fit).

It should be emphasized once again that this model has a more formal character. In particular, no information on the proceeding chemistry can be given from thermogravimetric data only. Considerably more information would be obtained by coupling thermogravimetry with mass spectroscopy.

Model-free analysis according to Ozawa-Flynn-Wall
The energy-plot indicates for the first thermal decomposition step of Glucose an activation energy of approximately 110 kJ/mol and for the dominant path of the second step an activation energy of 180 kJ/mol.

Results of model fit

Model-fit of Thermal Decomposition of Glucose
The triple-step reaction of the thermal decomposition of Glucose, containing competitive reaction paths, allows a high quality fit of all TGA measurements. 

The branched reaction path results in a specific behavior: by changing of the reaction temperature the parts of product C and D are varied.

At temperature of 210 ¡C the largest part of B is transformed to the product D. Inversely, at a temperature of 280 ¡C the largest part is transformed to the product C. This behavior is caused by the large difference of the activation energies for step 2 and step 3, respectively.