Sulfur specificity in the bench-scale biological desulfurization of crude oil by Rhodococcus IGTS8

Biological removal of organic sulfur from petroleum feedstocks mag offer an attractive alternative to conventional thermochemical treatment due to the mild operating conditions and greater reaction specificity afforded by the nature of biocatalysis. Previous investigations have either reported the d esulfurization of model sulfur compounds in organic solvents or gross desul furization of crude oil without data on which sulfur species were being rem oved. This study reports initial sulfur speciation data for thiophenic sulf ur compounds present in crude oil which may be used as a guide both as to w hich species are treated by the biocatalyst investigated as well. as to whe re biocatalyst development is needed to improve the extent of biological de sulfurization when applied to whole crudes. Biodesulfurization of two diffe rent crude oils in the 22-31 degrees API specific gravity range with total sulfur contents between 1 and 2% is demonstrated in 1-dm(3) batch stirred r eactors using wild type Rhodococcus sp IGTS8, while analysis of the crudes before and after biodesulfurization did not reveal a decrease in total sulf ur, GC-I;IS did reveal significant (43-99%) desulfurization of dibenzothiop henes (DBT) and substituted DBTs. Fractionation of the whole crude, followe d by analysis using gas chromatography-sulfur chemiluminescence detection ( GC-SCD) of the aromatic fraction of the Van Texas crude oil, demonstrated a reduction of sulfur in this fraction from 3.8% to 3.2%. This research indi cates that IGTS8 may be capable of biodesulfurization of refined products s uch as gasoline and diesel whose predominant sulfur species are dibenzothio phenes, Further biocatalyst development would be needed for effective treat ment of the spectrum of sulfur-bearing compounds present in whole crudes.