Naphtha alkaline sweetening process was largely relevant before stricter standards Euro-4 and Euro-5 for total sulfur content were applied. In the naphtha fraction, mercaptan compounds are represented by C1-C5 mercaptans.
Today naphtha treatment remains relevant only in preparation of produced at mini refineries naphtha, to transportation for its further deep processing by hydrotreating.
At naphtha alkaline treatment light (C1-C2) mercaptans undergo alkaline extraction with subsequent regeneration of alkali and disulfides separation. If appropriate, high molecular (C3-C5) mercaptans in naphtha fraction are sweetened by oxidative treatment in the presence of phthalocyanine catalyst, alkaline solution, atmospheric oxygen – principle of deodorization.