Laboratory sulfonation methods for detergent alkylbenzenes

Abstract Laboratory methods are described for evaluation of alkylbenzenes by three different sulfonation techniques: batch oleum sulfonation, continuous oleum sulfonation, and batch sulfur trioxide‐air sulfonation. Sulfonation conditions such as temp, mixing, and reaction time are carefully controlled; and the resulting sulfonates are reproducible in quality. Of particular interest is the close control of the sulfonating agent feed rate. In the batch oleum method, this is accomplished by flow through a calibrated capillary under constant head and in the SO 3 ‐air method, by constant rate injection of liquid SO 3 into the vaporizer. In the continuous oleum method, both alkylate and oleum feed rates are kept at desired levels with a duplex positive displacement pump which pumps against spring‐loaded ball check valves in the lines to the mixing pump. Sulfonation data (including solution colors and unsulfonated oil contents of the products) are presented for several commercial detergent alkylbenzenes varying in average mol wt from 241舑267. Quality of the alkylbenzene is more critical for the continuous oleum and batch SO 3 ‐air methods than for the batch oleum sulfonation.