To obtain a low-sulfur gas oil having a high lubricity by oxidizing a gas oil fraction contg. at least a specified amt. of naphthalenes with naphthalenes-oxidizing bacteria to thereby bring the sulfur content and alkali extractable content each into a specified range.
Naphthalenes-oxidizing bacteria are planted in a multiplication medium contg. specified amts. of glucose, ammonium sulfate, sodium phosphate hydrate, disodium phosphate heptahydrate, MgCl2, KCl, FeSO4, MnCl2.2H2O, CaCl2, and naphthalene and are cultured under specified conditions. The medium is then centrifuged, and the resultant precipitate is suspended in a phosphoric acid buffer soln. to give a bacteria suspension. The suspension is added to a gas oil fraction produced at a petroleum refinery, contg. 0.005mass% naphthalenes represented by the formula (wherein R1 to R8 are each H, a 1-8C alkyl, etc.), and having a b.p. of about 150-360°C. The fraction is then put into a container and is shaked at about 30°C for about a day, and a gas oil layer formed is separated. Thus is obtd. a low-sulfur gas oil contg. up to 0.05wt.% sulfur and 0.005-1wt.% alkali extractables.
SEKIMOTO MASANORI
NASUNO KAZUYA
YOSHIMURA TADASHI
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