Patent GB-666643-A (GB)
Title: Improvements in or relating to the production of sulfonated alkyl aromatic hydrocarbons
IPC: C07C303/44
Filed: 1948-09-07
Abstract: Sulphonated alkyl aromatic hydrocarbons are produced by reacting an alkyl aromatic hydrocarbon with an oleum containing at least 30 per cent by weight of free sulphur trioxide, in a proportion of the oleum to the hydrocarbon corresponding to at least 0.8 and not more than 1.6 mols. free sulphur trioxide per mol. hydrocarbon in a reaction zone in the presence of such a quantity of an inert diluent-refrigerant and at such a pressure within the range of from sub-atmospheric to 3.5 atmospheres <PICT:0666643/IV (b)/1> that a portion of the diluent-refrigerant is maintained in liquid phase throughout the reaction concomitantly with the dissipation of heat of the exothermic reaction by vaporization of the diluent-refrigerant in an amount maintaining the sulphonation reaction mixture at a temperature of from - 10 DEG  to + 15 DEG  C., introducing the resultant liquid reaction mixture containing alkyl aromatic sulphonic acid, sulphuric acid and inert diluent-refrigerant into the upper portion of a separate stripping zone and therein flowing the same downwardly as a descending film in indirect heat exchange relation with a heating medium at a temperature at which the diluent-refrigerant is vaporized from the liquid mixture and separately withdrawing said diluent refrigerant as a vapour steam from the upper portion and the unvaporized liquid from the lower portion of the stripping zone. The invention relates particularly to the production of alkyl aromatic sulphonic acids for use in the manufacture of synthetic detergents.  The alkyl aromatic hydrocarbons to be sulphonated generally contain an alkyl radical having 9-18 carbon atoms; suitable starting materials are obtained by alkylating an aromatic hydrocarbon having not more than two alkyl radicals each of not more than two carbon atoms, e.g. benzene, toluene, xylene, ethyl toluene or naphthalene, with olefinic hydrocarbons having 9-18 carbon atoms, e.g. propylene polymers or a selected fraction of olefinic pressure distillate boiling, for example, from about 170 DEG to 240 DEG  C., if desired in presence of a catalyst such as sulphuric acid or hydrogen fluoride.  Suitable inert diluent-refrigerants are sulphur dioxide and paraffinic hydrocarbons containing 3-8 carbon atoms and normally boiling substantially within the range of from - 42 DEG  to 126 DEG  C., and non-reactive cyclopentanes, cyclohexanes and halogenated hydrocarbons boiling in the same range such as propane, butane, pentane, trichlorethane, freon, carbon tetrachloride, perfluorpropane and the like.  Using the apparatus shown, the alkyl aromatic hydrocarbon is pumped from storage tank 1 to reactor 7, at the desired pressure depending on the diluent-refrigerant used and sulphonation temperature, via line 5 wherein it commingles with diluent-refrigerant pumped from tank 14. Oleum is led to the reactor 7 from storage 8.  The reactor and pipe lines may be lined with glass, stainless steel or ethylene polymer resin to prevent excessive corrosion.  The reactants are maintained in reactor 7 until substantially complete mono-sulphonation is effected, temperature being maintained at - 10 DEG  to 15 DEG  C. and the pressure controlled by a pressure-regulating valve, preferably located in the vapour outlet line from the stripping zone as described later.  After sulphonation the mixture is directed via line 25 and valve 26 to a falling film stripper 27.  The mixture is flowed down tubes 30 as a film in indirect contact with a heating medium, e.g., hot water circulated around the tubes via pipes 41 and 43 from a zone 37 wherein the water is maintained at the desired temperature, say 50 DEG -95 DEG  C., by steam introduced through line 45.  The stripped mixture of alkyl aromatic sulphonic acid and sulphuric acid is removed via line 32.  The diluent-refrigerant vaporizes in tubes 30, passes out through the upper portion of the stripper to a compressor suction surge drum 50 from which entrained liquid condensate is recycled to the stripper, remaining diluent-refrigerant being passed via valve 5 to compressor 55 where the diluent-refrigerant is liquefied.  This valve 54 may be regulated to maintain the desired pressure on reactor 7 or alternatively the compressor speed may be adjusted to give the desired reactor pressure.  The liquefied diluent-refrigerant is directed to receiver 61 from which it may be recycled via line 22 and expansion valve 62 to the reactor 7.  The stripping operation in stripper 27 may be facilitated by introduction of a little water into the reaction mixture being fed in via line 25 or an additional external inert stripping gas, e.g. nitrogen, air, flue gas or a light paraffin gas may be introduced into the stripper. An example describes a process utilizing apparatus of the type described wherein an alkylated toluene fraction B.P. 275 DEG -345 DEG  C. and obtained by alkylating toluene with propylene polymer, is sulphonated by means of 65 per cent oleum in presence of liquid butane as diluent-refrigerant at a temperature of about 1 DEG  C. and substantially atmospheric pressure; the product may be neutralized without the need for prior treatment to remove sulphuric acid.  In a modified form of stripper (not shown), the heating space of the stripper is divided into two separate zones; the lower zone being served by the circulating hot water or other heating medium from zone 37, liquefied diluent-refrigerant from receiver 61 being passed through the upper zone whereby it is further cooled in indirect heat-exchange with the material to be stripped and is then fed to reactor 7.  Specifications 539,281 and 666,642 are referred to.  The Specification as open to inspection under Sect. 91 is not restricted to the maintenance of a pressure of from sub-atmospheric to 3.5 atmospheres during the sulphonation.  This subject-matter does not appear in the Specification as accepted.