Kinetics and Mechanism of the Reaction between Lithium Carbonate and Silica

Abstract

The reaction of equimolar mixtures between Li₂CO₃ and amorphous SiO₂ has been studied by means of DTA, X-ray diffraction and thermogravimetric techniques. The reaction was found to proceed in seven stages: Li₂CO₃+SiO₂(amorphous)→Li₂O⋅SiO₂+CO₂ (1)
Li₂CO₃+2SiO₂(amorphous)→Li₂O⋅2SiO₂+CO₂ (2)
2Li₂CO₃+SiO₂ (amorphous)→2Li₂O⋅SiO₂+2CO₂ (3)
Li₂CO₃+Li₂O⋅2SiO₂→2(Li₂O⋅SiO₂)+CO₂ (4)
2Li₂O⋅SiO₂+SiO₂(quartz, cristobalite)→2(Li₂O⋅SiO₂) (5)
2Li₂O⋅SiO₂→Li₂O⋅SiO₂+liquid (6)
Li₂O⋅2SiO₂→Li₂O⋅SiO₂+liquid (7)
The main part of the overall reaction concerning with the decomposition of Li₂CO₃ was best expressed by the contracting cube equation and the apparent activation energy was determined as 36.3 kcal/mol. This activation energy can be assigned to the overall reaction (1)-(3).