GB758848A - Improvements in or relating to process for sweetening a sour petroleum naphtha - Google Patents

Abstract

Sour petroleum naphtha is sweetened by (a) contacting the naphtha, containing mercaptans and phenols, with aqueous caustic alkali solution, (b) separating naphtha from the aqueous solution, (c) contacting the aqueous solution containing mercaptides and phenolates with free oxygen to convert mercaptides to disulphides, (d) removing disulphides from the aquesous solution, (e) contacting naphtha from step (b) with regenerated solution from step (d) and free oxygen, and (f) separating the sweet naphtha from the aqueous caustic alkali solution. The treatment of sour thermally cracked naphtha, e.g. naphtha obtained from the thermal cracking of gas oils, is described; the naphtha separated as in (b) above is given an additional treatment (g) with a caustic alkali solution containing phenolates extracted from the sour naphtha. The combined caustic alkali solutions from steps (b) and (g) are regenerated, separated from disulphides, and recycled partly to (g) and partly to a treatment (h) wherein naphtha separated from step (g) is contacted as in (e) above. The oxidation of mercaptides to disulphides may be accelerated by oxidation catalysts such as di- and trihydroxybenzenes, e.g. hydroquinone. The disulphides may be extracted with solvents such as hydrocarbon oils, e.g. catalytically cracked cycle oil boiling in the gas oil range. Caustic alkalis referred to are sodium and potassium hydroxides. The aqueous solution of step (a) may contain 10-35 per cent caustic alkali and that of step (g) 5-15 per cent free caustic alkali and 10-30 per cent phenolates.