Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide. Magnesium hydroxide is obtained by the treatment of magnesium chloride solutions, typically seawater, with lime.
Mg2+ + Ca(OH)2 → Mg(OH)2 + Ca2+
Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures (1500 – 2000 °C) diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory. Calcining temperatures (1000 – 1500 °C) produces hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700 – 1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia. Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, the resulting material appears to reabsorb carbon dioxide from the air.
Minteq utilizes magnesium oxide as aggregate and matrix in a variety of products in the steelmaking industry as well as non-ferrous product, petrochemical, cement, and power generation industries. Its primary function is to provide thermal insulation and chemical stability.