Patent GB-656064-A (GB)
Title: Improvements in the manufacture of secondary alkyl sulphates
IPC: C07C305/04
Filed: 1948-07-22
Abstract: Secondary alkyl sulphates are manufactured by sulphation of olefines having more than six carbon atoms in the molecule, followed by neutralization of the esters so obtained, the non-aqueous phase of the reaction mixture, after separation from the aqueous phase, if desired with the aid of a solvent, being subjected to fractional distillation to produce a fraction containing the bulk of the olefines and secondary alcohols; this fraction is subjected to dehydration so as to convert the secondary alcohols to olefines and the olefines thus obtained are recycled for conversion into secondary alkyl sulphates.  The olefines used as starting materials in the production of the ester salts are those which yield products valuable as wetting, detergent and/or emulsifying agents, for example, those having more than six carbon atoms such as a mixture obtained by cracking petroleum wax or petrolatum.  Mixtures of olefines or individual olefines derived from other sources may also be used.  The process and apparatus for the sulphation and neutralization of the olefines may be those forming the subject of Applicants' co-pending Specification 655,459.  The solvent used for extracting the non-aqueous fraction from the reaction mixture may be a mixture of petroleum spirit and isopropyl alcohol or industrial methylated spirit.  The solution so formed is fractionally distilled to recover the solvent and a middle fraction containing the bulk of the olefines, secondary alcohols and unreactive hydrocarbons.  In the case of olefines having 8-18 carbon atoms, the fractions containing these are those boiling below about 330 DEG  C. at atmospheric pressure.  The fractions so obtained are dehydrated to convert the secondary alcohols into olefines.  The dehydration may be carried out in the liquid phase, for example, by boiling under reflux in the presence of a dehydration catalyst such as zinc chloride or para-toluene sulphonic acid.  Better results are, however, obtained by carrying out the dehydration in the vapour phase using, for example, alumina as a catalyst.  The temperature of such vapour phase dehydration is preferably about 300 DEG  C.  The dehydration product consists mainly of olefines together with unreactive hydrocarbons and the mixture can be recycled and sulphated in the normal way.  More drastic sulphation conditions are, however, desirable than for the sulphation of the original starting material.  In the example, a mixture of olefines obtained by cracking petroleum wax is sulphated and neutralized as described in Specification 655,459.  The non-aqueous phase of the product is extracted from the reaction mixture with a mixture of petroleum spirit boiling at 90-110 DEG  C. and isopropyl alcohol or industrial methylated spirit and the resulting solution is fractionally distilled.  The solvent and the fraction of the solution boiling below 330 DEG  C. at atmospheric pressure are separately distilled.  The latter fraction is vaporized and passed together with one-tenth of its weight of steam through a pre-heater, raising the temperature to 300 DEG  C. and then through a column of bauxite or g -alumina kept at 300 DEG  C.  The resulting mixture of olefines and unreactive hydrocarbons is sulphated.