Decomposition of Potassium Hydrogen Carbonate: Thermochemistry, Kinetics, and Textural Changes in Solids

To determine unbiased rates of the decomposition of KHCO3, slowly increasing- and constant-temperature TGA methods were employed with small, finely ground samples. Such reaction provides a novel, porous, and highly reactive sorbent for noxious and/or malodorous gases. The bicarbonate commences decomposing at 364 K, and the maximum rate of reaction, attained at 421.9 K, amounts to 5.73 × 10–4 1/s. Taking advantage of the Schlömilch function, an Arrhenius-type relationship is developed by an integral method: the activation energy is as large as 141.3 kJ/mol and the order of reaction amounts to 1.145. While the pore volume made by calcination (0.2309 cm3/g) is not affected by temperature at 403–503 K, the mean pore diameter and the grain size augment with increasing temperature. The diagram presented makes it possible to conveniently predict the conditions to attain near-complete conversion of the bicarbonate and minimize undesirable sintering of the nascent carbonate.