Patent GB-742631-A (GB)
Title: A process for the removal of solvents from aqueous solutions of higher sulphuric acid alkyl ester salts by distillation
IPC: B01D3/14
Filed: 1953-11-12
Abstract: Hydrocarbons boiling below 120 DEG C. and lower aliphatic alcohols or ketones are removed from aqueous solutions of secondary sulphuric acid alkyl ester salts containing at least 8 carbon atoms per molecule by submitting the solution to a two-stage distillation process; the first stage is interrupted after at least 95 per cent of the hydrocarbons have been distilled off, the vapours being condensed to yield a condensate comprising a hydrocarbon-layer and a separate layer consisting of an aqueous solution of the alcohol or ketone. The second stage of the distillation is performed on the bottom product of the first stage and effects vaporization of the alcohol or ketone together with water thus leaving a concentrated solution of the ester salt; the second-stage vapours are fed directly to a rectification column from which the alcohol or ketone is withdrawn overhead while the bulk of the water is withdrawn from the base of the column.  The process obviates the foam-formation experienced in the rectification associated with a one-stage distillation of the ester salt solution.  Alcohols referred to are ethanol, propanol and butanol.  Ketones referred to are butanone and 4-methyl-pentanone-2. In an example, a crude secondary sodium alkyl sulphate solution, prepared from a C8-18 cracked distillate of solid paraffin wax, was desalted by means of propanol-2, and subsequently extracted with a gasoline of boiling range 80 DEG -90 DEG C.  The raffinate thus obtained contained 14 per cent of ester salts, 19 per cent of propanol, 9 per cent of gasoline and 58 per cent of water.  The raffinate was distilled in two separate stages in four evaporators connected in series, the vapours from the first evaporator being conducted separately to a condenser.  The bottom product from the first evaporator was distilled in the three following evaporators, the vapours from which were conducted to a column provided with sieve plates equivalent to 10 theoretical plates.  The heat supplied to the first evaporator was adjusted so that the bottom product therefrom contained only 0.5 per cent of gasoline.  The concentrated solution discharged from the last evaporator contained 37 per cent of ester salt, no gasoline and only 0.5 per cent of propanol.  The vapours from the first evaporator gave, on condensation, a lower aqueous layer and an upper layer comprising gasoline together with a little dissolved propanol and water. This gasoline layer was suitable for the extraction of fresh ester salt preparation.  The vapours introduced into the colume consisted essentially of water containing 31 per cent of propanol and 0.9 per cent of gasoline.  Using a reflux ratio of about 5, a top product consisting of 8.5 per cent of propanol, 2.5 per cent of gasoline, and water, was obtained.  The bottoms consisted of water containing 3 per cent of propanol.  The top product from the column was combined with the aqueous layer produced in the first distillation stage, to give a resulting solution which was suitable for use in desalting fresh crude ester salt solutions.