Decomposition of potassium hydrogen carbonate: Thermochemistry, kinetics, and textural changes in solids

Abstract

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 x 10(-4) 1/s. Taking advantage of the Schlomilch 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 cm(3)/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.