Removal of mercaptans from oil by hollow fiber membrane-based extraction

A hollow fiber membrane contactor consisted of highly hydrophilic asymmetric cellulose ultra-filtration membrane was used to remove the mercaptan (RSH) from simulated gasoline (RSH/n-octane system) via extraction. Effects of operation conditions including extractant species, its flowrate and concentration, feed flowrate and volume ratio of feed to extractant (0.5~3) on RSH removal efficiency and overall mass transfer coefficient were investigated. The experiment results indicate that the oil film resistance controls the overall mass transfer process when 3%(wt) NaOH solution is employed as extractant. Furthermore, the overall mass transfer coefficient increases with increasing extractant concentration and feed flowrate, while remains constantly with increasing extractant flowrate and volume ratio of feed to extractant. After treated with above membrane-based extraction, a high RSH removal efficiency over 99% could be achieved with almost no oil loss; the sulfur content in the mercaptan removed simulated gasoline is less than 10 ug•g^(-1). Finally, the operation process of the fiber membrane contactor shows excellent stability.