Patent GB-687714-A (GB)
Title: Improvements in or relating to the production of surface active agents
IPC: C11D1/14
Filed: 1948-10-20
Abstract: Surface-active crude sulphonated hydrocarbons containing sulphuric acid and organic impurities are purified by admixing the crude material with water and a solvent inert to sulphuric acid under the conditions employed and consisting essentially of one or more hydrocarbons and/or halogenated hydrocarbons, the water and solvent being added in such proportions that, after admixing, two and only two layers are formed, the upper layer comprising solvent and sulphonated hydrocarbon and the lower layer comprising sulphuric acid of 80-87 per cent by weight concentration and organic impurities, and thereafter separating the upper layer and removing solvent from the required surface-active sulphonates. Suitable starting materials are obtained by sulphonating alkyl substituted aromatic hydrocarbons, e.g. alkyl benzenes, the alkyl substituent having at least 9 carbon atoms such as toluene alkylated with propylene trimers or tetramers. The amount of solvent added is preferably 100-160 gms. per mole of sulphonated hydrocarbon.  The purified sulphonates may be recovered by extracting the separated solvent layer with an aqueous medium preferably containing sufficient of a lower alcohol to prevent emulsification; the aqueous medium may contain an inorganic base or this may be added to the aqueous extract to obtain the sulphonic acid salt.  The solution of acid or salt may then be distilled to remove alcohol and if desired water.  Alternatively the original solvent layer may be neutralized and solvent distilled off.  The solvents preferably boil within the range 60-200 DEG  C. and include petroleum fractions (paraffinic), in particular kerosines and white spirits, and chloroform and carbon-tetrachloride.  In examples: (1) toluene is alkylated with propylene tetramer using HF as catalyst, an alkylate of initial B.P. 260 DEG  C. is recovered, sulphonated with sulphuric acid and oleum, two-layer formation effected by addition of water and n-heptane, kerosine, nonane or white-spirit, the lower layer of 82 per cent sulphuric acid removed and the upper layer washed with fresh solvent and extracted with aqueous-methanol or isopropanol solution, the extract neutralized with soda and the sodium sulphonate recovered as a dry solid; (2) a similar alkylate is sulphonated with oleum and two-layer formation effected by addition of various amounts of water and an aromatic-free petroleum fraction B.P. 112-125 DEG  C. and data is given showing the effect in the final product of using too little or too much water, illustrated by a graph (not shown); (3) dodecyl toluene is sulphonated with oleum, two-layer formation effected by means of water and a refined petroleum, the upper layer is run into aqueous caustic soda and the product dried by passage through a climbing film evaporator.  According to the Provisional Specification the crude material may not contain sulphuric acid, the solvent may be any substantially water-immiscible inert solvent and the proportion of water and solvent such as will produce formation of two immiscible layers.  Ethers are further specified solvents.