GB419567A - Improved manufacture of alkali sulphides - Google Patents

Abstract

Anhydrous alkali sulphides free from carbonates or hydroxides are obtained by treating an alkali carbonate or an alkali carbonate containing alkali hydroxide with hydrogen sulphide or carbon oxysulphide in the presence of a reducing or inert gas such as carbon monoxide, hydrogen, methane, or nitrogen at an elevated temperature which may be 400--800 DEG C. As initial material, an alkali sulphide containing alkali carbonate or hydroxide may be used, or materials adapted to give rise to such sulphide such as sodium sulphate and water gas, whilst instead of hydrogen sulphide or carbon oxysulphite components giving rise to these gases, such as hydrogen or carbon monoxide and sulphur vapour may be employed. When using hydrogen sulphide, gas mixtures containing 5--15 per cent thereof are generally employed, but in operating under reduced pressure concentrations of 15--25 per cent may be used. Technical gas mixtures containing both hydrogen sulphide and hydrogen and/or carbon monoxide may be used. In one example, sodium carbonate is treated at 650 DEG C. with a mixture of 90 per cent hydrogen and 10 per cent hydrogen sulphide. In a second example sodium carbonate is treated at 600 DEG C. with a mixture of 7,5 per cent of hydrogen sulphide and 92,5 per cent of hydrogen, with recirculation of spent gas after removal of water and carbon dioxide and addition of further hydrogen sulphide. In this way a ratio CO : H2 = 0,38 in the circulating gases is ultimately obtained. In a third example, treatment is effected with a gas mixture containing, in addition to hydrogen sulphide, hydrogen, and carbon monoxide, small percentages of methane, carbon dioxide, nitrogen, and water vapour. In a further example the gas mixture used is a mixture of water gas with gases obtained by the distillation of crude mineral oil. In a fifth example, sodium sulphate reduced with coal at 750 DEG C. in the presence of carbon monoxide, is treated at 650 DEG C. with hydrogen sulphide containing reducing gases. Alternatively \ba1/2\be--1 per cent of hydrogen sulphide may be added to the carbon monoxide in the reducing step. In a further example, sodium sulphate reduced by water gas at 700 DEG C. is treated with gases containing hydrogen sulphide. Alternatively, 1--2 per cent of hydrogen sulphide may be added to the water gas in the reducing step. When potassium carbonate is used higher temperatures and lower concentrations of hydrogen sulphide are required.