Studies on the permeation of aromatic hydrocarbons through liquid surfactant membranes

Abstract

The effect of operating parameters on the batch scale permeation of hydrocarbons from benzene—heptane mixtures and a straight run naphtha through liquid membrane is reported. The thirteen operating parameters studied include: mixing intensity, surfactant concentration, treat ratios, contact times, temperature and additives. The variations observed in the two key properties of selectivity and aromatic recoveries as well as in product compositions with change in operating parameter is discussed. Surfactant concentration contact time during permeation, type and concentration of additive used appear to exert a marked effect on the enrichment obtained. The careful optimization of operating parameters give selectivities as high as 50 and aromatic recoveries of 75% in one stage at 30°C. Comparison of data with batch liquid—liquid extraction data from extraction of similar feed mixtures with the most widely used solvent, sulpholane, under typical industrial conditions, has shown that selectivities and aromatic recoveries in liquid membrane permeation (LMP) are much higher. Batch scale LMP experiments with straight run naphtha as feed show that under optimum conditions of membrane stability and operating parameters the dearomatization of naphtha from an initial aromatic level of 22 vol.% to 10.5 vol.% is possible in one stage at 30°C with a raffinate yield of 63%. The results obtained on benzene—heptane model mixture compare fairly well with those obtained on naphtha feed.