Apparent kinetic behavior of the thermal decomposition of synthetic malachite

The influence of self-generated gaseous products on the kinetics and mechan ism of the thermal decomposition of synthetic malachite, Cu2CO3(OH)(2), was investigated by means of conventional TG-DTA under various atmospheric con ditions, TG-MS and CRTA under a reduced atmospheric condition, and powder X -ray diffractometry of the partially decomposed sample. It was found that t he sample decomposes at a lower temperature under a higher partial pressure of self-generated gases. This interesting behavior, in contrast to the gen eral consideration of chemical equilibrium, results from catalytic action o f evolved H2O on the crystallization of the product CuO, and from an intera ction of evolved CO2 with poorly crystallized CuO under reduced pressure. ( C) 1999 Elsevier Science B.V. All rights reserved.