US Patent 7588741 Cyclical vacuum chlorination processes, including lithium extraction

Cyclical batch processes for halogenation, such as chlorination, of minerals in a fixed bed using a plurality of cycles which include the steps of at least partially evacuating the bed, charging the bed with reactant gas, maintaining the reactant gas in the bed for a predetermined time, and exhausting reaction products under vacuum. Also disclosed is the chlorination of spodumene in its beta crystalline form produced by calcining spodumene in its naturally-occurring alpha crystalline form to preferentially extract lithium as lithium chloride.