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 .