Kinetics and mechanism of formation of monocalcium aluminate, CaAl2O4

Abstract

The kinetics of the reaction for the formation of monocalcium aluminate (CaAl ₂ O ₄ ) using 1:1 molar mixtures of A.R. grade calcium carbonate and A.R. α-Al ₂ O ₃ or gibbsite have been investigated in the range 1150–1400 °C using quantitative X-ray diffraction analysis. The phases Ca ₃ Al ₂ O ₆ and Ca ₁₂ Al ₁₄ O ₃₃ were found to be intermediates in the formation of CaAl ₂ O ₄ , whereas CaAl ₄ O ₇ was formed via an initial side reaction. The formation of CaAl ₂ O ₄ from the oxides was found to fit well with the diffusion controlled model of Ginstling and Brounshtein. The activation energy for the formation of CaAl ₂ O ₄ from the amount of CaAl ₂ O ₄ formed from the reaction of calcite with α-Al ₂ O ₃ was determined to be 205±10 kJ mol ^-1 .