Shamim, Mostofa and Molla, Atiar Rahaman and Mukhopadhyay, Tapas Kumar and Dana, Kausik (2014) Non-isothermal kinetic evaluation of pyrophyllite dehydroxylation. Transactions of the Indian Ceramic Society, 73 (2, SI). pp. 181-186. ISSN 0371-750X

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Abstract

Dehydroxylation of clay minerals is an important process with several applications. Despite the industrial use of several well defined clay minerals, only the dehydroxylation kinetics of kaolinite has been reported. Still, the kinetics of these solid state reactions is yet to be understood using unambiguous model. In the present work, we have performed detailed kinetic analysis of dehydroxylation of pyrophyllite clay using non-isothermal kinetics by thermogravimetry (TG) at different heating rates. The TG data has been analysed initially with model-free methods (ASTM E 698, ASTM 1641, Friedman analysis and Ozawa-Flynn-Wall method). Interestingly, both the model-free methods of analysis have unequivocally indicated that activation energy (E-act) changes very marginally with progress of reaction and a single activation energy barrier is present. This surmises that the dehydroxylation process is a single stage process. A multivariate non-linear regression on the dynamic thermal data at different heating rates has been performed to determine the most probable kinetic model based on statistical fit. It has been found that, TG data provides best fit with regression coefficient (r(2)) value of 0.994, when a single stage Avrami type diffusion reaction model is assumed, and an activation energy of 159 kJ.mol(-1).

Item Type:	Article
Subjects:	Structural Clay Products
Divisions:	Glass
Depositing User:	Bidhan Chaudhuri
Date Deposited:	15 Dec 2014 07:17
Last Modified:	15 Dec 2014 07:17
URI:	http://cgcri.csircentral.net/id/eprint/2629

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