Improvement on acid pyrolysis method for alkyl homolog and phenyl isomer distribution of alkylbenzene sulfonates

An acid pyrolysis method developed by H.L. Lew in 1967 has been further investigated and improved. Alkylbenzene sulfonates are pyrolyzed with phosphoric acid. This gives quantitative desulfonation. The resulting alkylbenzenes are online analyzed by gas chromatography. Lew's approach replaced the time-consuming reflux desulfonation gas chromatography methodology. While greatly reducing turnaround time, phosphoric acid used for acid pyrolysis in Lew's method resulted in deterioration of the gas chromatography column stationary phase and also corrosion of the pyrolysis tube. Improvement in these areas was studied. Column deterioration can be eliminated by using an acid trap, and pyrolysis tube corrosion can be minimized by using quartz wool to prevent phosphoric acid sputtering in the pyrolyzer. The method discussed in this paper produces results totally comparable with the reflux desulfonation gas chromatography and Lew's methods.