Oxidation of dibenzothiophene by laccase or hydrogen peroxide and deep desulfurization of diesel fuel by the later

摘要

Enzymatic oxidation of dibenzothiophene(DBT)catalyzed by laccase in the presence of 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)(ABTS)was compared with the chemical oxidation with hydrogen peroxide catalyzed by phosphotungstic acid.Enzymatic oxidation with laccase(2.4 U/ml)of 25 uM DBT with 1.5 mM ABTS required a molar ratio [O2]/[ABTS]=140 and 72 h at 40 °C in a water-acetonitrile reaction mixture,showing a rate constant of kt=~ 6.3 x 10~ 4 min~ '.Whereas peroxide oxidation of 10 mM DBT with 39 uM phosphotungstic acid required only a molar ratio [H2O2]/[DBT]=2,showing a rate constant of fe=-6.1 x 10~ 2 min"'in a hexane-ethanol system.A sample of diesel fuel,containing 342 ppm of sulfur,was chemically oxidized by an excess of hydrogen peroxide and 119 uM phosphotungstic acid dissolved in ethanol,in less than 3 h at 60 °C and atmospheric pressure.No sulfur could be detected in these samples after an additional extraction with an equal volume of ethanol.