GB756545A - Improvements in or relating to manufacture of hydrazine - Google Patents

Abstract

Aqueous hydrazine is distilled in contact with a dehydrating agent and a saturated hydrocarbon whose boiling temperature at atmospheric pressure is within the range of about 90 DEG C. to about 150 DEG C. Mineral oils in which a minor amount of an aromatic or olefinic hydrocarbon may be present, and aliphatic and cycloaliphatic hydrocarbons are specified. Presence of hydrocarbon in the distilland stabilizes the anhydrous hydrazine. The dehydrating agent may be sodium hydroxide, barium hydroxide, or calcium oxide. At least one mole of sodium hydroxide should be used per mole of water to be removed. The process may be continuous, the dilute aqueous hydrazine, sodium hydroxide and hydrocarbon being fed continuously to the still while continuously removing sodium hydroxide monohydrate from the still and separately removing hydrazine and hydrocarbon, which form separate layers, from the distillate receiver. The hydrocarbon can be returned to the still and a portion of the sodium hydroxide monohydrate enriched and returned to the still with the aqueous hydrazine, the remainder of the monohydrate being dehydrated. A portion of the hydrocarbon may be retained with the hydrazine to reduce hazards in store or in transport. In an example 99 per cent of the hydrazine was recovered at 96.3 per cent cencentration by distilling a 54.5 per cent aqueous hydrazine at about 105 DEG C. with sodium hydrazine and 40 per cent by weight of the aqueous hydrazine of a crude oil fraction boiling between 121 and 143 DEG C. In a modfication the hydrocarbon is metered to the still as a vapour, some liquid hydrocarbon being present in the still throughout the distillation.