THERMAL ANALYSIS OF BASIC MAGNESIUM CARBONATE CONTAINING DIFFERENT ALKALI METAL CARBONATES

Abstract Thermal decomposition of basic magnesium carbonate impregnated with alkali metal (Li, Na, K, Rb and Cs) carbonate, in the preparation of alkali metal-doped MgO catalysts, has been investigated by TG, DTG and DTA techniques in the temperature range 30–1200°C. The exothermic DTA peak observed for the basic magnesium carbonate around 490 °C is found to be absent from the samples containing alkali metal carbonates, except for the sample with Na/Mg = 0.02. The solid products (i.e. alkali metal-doped MgO) of decomposition at different temperatures have been characterized for its alkali metal content, crystalline phases, surface area and surface basicity. The thermal decomposition of basic magnesium carbonate and properties of solid products of the decomposition are found to be strongly influenced by the addition of alkali metal carbonate to the magnesium carbonate, depending on the type of alkali metal and its concentration. The addition of alkali metal carbonate has resulted in a large decrease in the surface area, but an increase in the density of surface basic sites, of MgO obtained in the decomposition.