Kinetics of the thermal decomposition of sodium hydrogen carbonate evaluated by controlled rate evolved gas analysis coupled with thermogravimetry

Influences of the product gases on the kinetics of the thermal decomposition of sodium hydrogencarbonate, NaHCO3, were investigated by means of controlled rate evolved gas analysis coupled with TG (CREGA-TG). From a series of CREGA-TG measurements carried out under controlled gaseous concentrations of CO2 and H2O by considering the self-generated CO2 and H2O during the course of reaction, anomalous effects of CO2 and H2O on the kinetic rate behavior of the thermal decomposition of NaHCO3 were revealed, that the reaction is decelerated and accelerated by the effects of atmospheric CO2 and H2O, respectively. The kinetic rate behavior under controlled atmospheric condition of CO2 = 0.1 g m(-3) and H2O = 1.2 g m(-3) was characterized by the apparent fitting to a kinetic equation of Avrami-Erofeev type with the apparent activation energy of E-a = 111.5 +/- 4.8 kJ mol(-1) and pre-exponential factor of A = ( 1.29 +/- 0.01) x 10(11) s(-1). The effects of atmospheric CO2 and H2O on the apparent kinetic parameters were appeared as the decreases in both the Values of E,, and A and the increase in the value of A, respectively. (c) 2005 Elsevier B.V. All rights reserved.