INFRARED KINETIC STUDY OF HIGH-TEMPERATURE REACTIONS OF SYNTHETIC KAOLINITE

An infrared frequency shift method was used to follow the kinetics of conversion of dehydroxylated synthetic kaolinite to mullite. Comparison of the kinetic and activation thermodynamic data for natural and synthetic kaolinite suggests that the mechanism of high‐temperature reaction is similar, although the activation energy of synthetic kaolinite is larger than that of natural kaolinite because of the lack of nucleation‐promoting impurity cations in the former. The high‐temperature ir data indicate that there is little or no difference in the cation coordination of the phases intermediate to metakaolinite and mullite, but that the principal high‐temperature coordination change (probably the accommodation of aluminum in well‐defined tetrahedral sites) occurs during the later stages of mullite formation. Copyright © 1969, Wiley Blackwell. All rights reserved