Brief description of the de-oiling of aqueous solutions of detergent, in particular of sodium lauryl sulphate and stripping column, for its implementation

摘要

Free oil, often an objectionable impurity in synthetic organic detergents, such as sodium lauryl sulfate, is removed from aqueous solutions by extraction thereof with hexane in the presence of lower alkanol, with the proportion of the alkanol present being in a relatively narrow range with respect to the sodium lauryl sulfate, in which range it helps to promote efficient extraction of the free oil by the hexane without solubilizing the hexane in the aqueous medium to such an extent as to result in an extracted detergent containing an unacceptably high proportion of hexane. Separation of the free oil from the aqueous detergent solution is effected in an extractor, to which the hexane is added, in mixture with a minor proportion of lower alkanol, normally isopropanol, and extraction of the free oil takes place after a preliminary mixing of isopropanol with detergent acid or neutralized base in a neutralization vessel and/or in a mixer upstream of the extractor. In a preferred embodiment of the invention the hexane extractant feed to the extractor is that resulting from distillation separation from the free oil of the hexane with some isopropanol. Also, extracted product is evaporated and the evaporator overhead, including isopropanol, hexane and water, is fed to the mixer. The evaporator product is steam stripped, very preferably in a novel stripper described herein, and the stripper overhead, including isopropanol and water, is conveniently fed to a neutralization vessel in which detergent acid, comprising the product of sulfation of lauryl alcohol with sulfur trioxide (and containing objectionable free oil), is neutralized with aqueous sodium hydroxide. Preferably the deoiling process is a continuous one, with only free oil being removed from the extractor feed, and the hexane and isopropanol are continuously recycled.