Wet air oxidation of aqueous solutions of linear alkylbenzene sulfonates

The semibatch wet air oxidation of aqueous solutions of linear alkylbenzene sulfonate (LAS), an anionic surfactant, has been investigated at temperatu res of 453 and 473 K, total pressures of 2.8 and 3.3 MPa, and reaction time s varying from 40 to 390 min The concentration of total organic carbon, che mical oxygen demand, and active detergent were followed throughout the reac tion, the main intermediates formed were identified by means of electrospra y-MS and highperformance liquid chromatography, and a mechanism describing LAS oxidation was proposed. It was found that LAS could easily be oxidized at 473 K to yield a group of molecules with short alkyl chains that do not behave as active detergents. The segments of alkyl chains broken off the re action intermediates appear primarily as short-chain organic acids that are resistant to total oxidation. Oxidation experiments were also performed at 473 K with solutions of 4-hydroxybenzene sulfonic acid, an intermediate fo rmed during the oxidation of LAS, It was found that 4-hydroxybenzene sulfon ic acid could easily be oxidized.