Alkylbenzenes and alkylbenzene sulfonates

Monoalkylbenzenes with a long alkyl chain ( 5) in the form of alkylbenzene sulfonates are the most important raw materials for the production of ionic detergents. 

Production of alkylbenzene derivatives in the 1940 s was linked to the Fischer-Tropsch synthesis. In 1941, IG Farbenindustrie began to produce chloroparaffins by chlorination of a Fischer-Tropsch alkane mixture rich in n-paraffins with an average chain length of C14 the chloroparaffin was made to react with benzene under Friedel-Crafts conditions and subsequently sulfonated to yield an alkylbenzene sulfonate. The product was given the trade name Tgepal NA . 

Modem benzene-based surfactants have alkyl groups with 10 to 14 carbon atoms, since with fewer than 6 carbon atoms in the alkyl group the alkylbenzene sulfonates are not sufficiently surface active, and alkylbenzene sulfonates with 15 and more carbon atoms in the alkyl group are difficult to dissolve in water, although they are soluble in organic media. 

There are two types of alkylbenzene sulfonates, namely alkylbenzenes with linear alkyl groups (LAS) and alkylbenzenes with branched alkyl groups (ABS or TPS). 

The branched alkylbenzenes, produced predominantly between 1950 and 1970, were obtained from propylene tetramer and benzene at temperatures from 20 to 50 °C, with a reaction time of a few minutes, using Friedel-Crafts catalysts (HF or AICI3). To avoid polyalkylation as far as possible, the operation was carried out with a 5 to 10-fold excess of benzene. The yield of dodecylbenzene was 70 to 80%. 

---