Optimisation of the Linear Alkyl Benzene Sulfonation Process for Surfactant Manufacture

Sulfonation of linear alkylbenzenes by reaction with sulfur trioxide is the predominant route to anionic surfactants other than soap. In the case study presented here, alkylbenzenes are contacted with sulfur trioxide in a short residence time falling film reactor following which the liquid reaction product mixture is aged. This work reviews a computational chemistry study, supported by an experimental relative rate study, on the reaction pathways occurring in the falling film reactor. It is concluded that the commonly accepted mechanism for aromatic sulfonation by sulfur trioxide does not apply, at least to alkylbenzene sulfonation, and an alternative reaction pathway consistent with the computational and experimental findings is proposed. A kinetic study on the ageing reactions is presented, indicating that there are several distinct stages leading to increase in conversion of linear alkylbenzene to linear alkylbenzene sulfonate. On the basis of these findings, process modifications leading to conversion...