Patent GB-755643-A (GB)
Title: Improvements in or relating to the preparation of hydrazine salts
Inventor: WEILER JOHN E
IPC: C01B21/16
Filed: 1954-02-11
Abstract: Hydrazine salts are prepared by reacting hydrazine with one or more acids, e.g. acetic acid, in countercurrent in a reaction column, by introducing a mixture of hydrazine and water at an intermediate point in the column, withdrawing from the bottom of the column an aqueous solution having a pH not above 6.0 and containing at least 10 per cent hydrazine salt, adding one or more acids to a portion of the aqueous solution withdrawn and returning the acidified portion to the top of the column at pH <PICT:0755643/IV(a)/1> not over 5.0, and maintaining an elevated temperature in the column sufficient to remove water vapour from the top of the column such that the solution withdrawn from the bottom contains at least 10 per cent hydrazine salt.  Mixtures of sulphuric, hydrochloric, hydrobromic, phosphoric, nitric and acetic acids may be used.  A salt-free hydrazine-steam mixture containing say up to 3 per cent hydrazine enters at 14, column 10, which has a packing of glass beads, porcelain, or Raschig rings 12 on grid 11. The temperature in the column is indicated as between 100 DEG  and 105 DEG  C., and the hydrazine salt solution in the column, below grid 11, is maintained at a temperature to evaporate water by steam coil 15.  Hydrazine salt solution is withdrawn from the base of the column at pH 5.5 preferably not below 3.0, and containing up to 50 per cent salt, and some is recycled through pipe 107 to the top of the column.  Acid is added at 106 to give pH 3.5.  Some of the salt solution is passed to storage 110 and may pass batchwise to vacuum, steam-jacketed dehydrator 113.  After treatment, e.g. 1 hour at above 116 DEG  C., say 120-125 DEG  C. at 50 mm. Hg., dry air is admitted and the fused salt passes to cooled flaking drum 115, whence it may be scraped by knife 116 to hopper 117.  The fused salt may alternatively be cooled in trays.ALSO:<PICT:0755643/III/1> Hydrazine salts are prepared by reacting hydrazine with one or more acids in countercurrent in a reaction column, by introducing a mixture of hydrazine and water at an intermediate point in the column, withdrawing from the bottom of the column an aqueous solution having a pH not above 6.0 and containing at least 10 per cent hydrazine salt, adding one or more acids to a portion of the aqueous solution withdrawn and returning the acidified portion to the top of the column at pH not over 5.0, and maintaining an elevated temperature in the column sufficient to remove water vapour from the top of the column such that the solution withdrawn from the bottom contains at least 10 per cent hydrazine salt.  Acids may be sulphuric, hydrochloric, hydrobromic, phosphoric, nitric, acetic or mixtures thereof.  A salt-free hydrazine-steam mixture containing say up to 3 per cent hydrazine enters at 14, column 10, which has packing of glass beads, porcelain, or Raschig rings 12 on grid 11.  The temperature in the column is indicated as, between 100 DEG  and 150 DEG C, and the hydrazine salt solution in the column, below grid 11 is maintained at a temperature to evaporate water by steam coil 15.  Hydrazine salt solution is withdrawn from the base of the column at pH 5.5 preferably not below 3.0, and containing up to 50 per cent salt, and some is recycled through pipe 107 to the top of the column.  Acid is added at 106 to give pH 3.5. Some of the salt solution is passed to storage 110 and may pass batchwise to vacuum, steam-jacketed, dehydrator 113.  After treatment, e.g. 1 hour at above 116 DEG C. say 120-125 DEG C. at 50 mm Hg, dry air is admitted and the fused salt passes to cooled flaking drum 115, whence it may be scraped by knife 116 to hopper 117.  The fused salt may alternatively be cooled in trays.ALSO:A solution of hydrazine hydrochloride and hydrazine phosphate in a weight ratio 95 : 5, prepared by the action of a mixture of hydrochloric and phosphoric acids on hydrazine [see Group III], or the dry solid obtained from such solution, may be used as soldering fluxes.