Deep desulfurization of hydrodesulfurized diesel oil by Pseudomonas delafieldii R‐8

Biodesulfurization is a promising technology for deep desulfurization. The remaining alkylated DBTs (dibenzothiophenes) in the HDS‐treated (hydrodesulfurized‐treated) diesel oil could be selectively and efficiently desulfurized by resting cells of Pseudomonas delafieldii R‐8, a Gram‐negative bacterium. The desulfurization activities of resting cells were greatly affected by W/O ratio (the volume ratio of aqueous phase to oil phase) and cell concentration. The desulfurization activity increased with the increase in the W/O ratio. When the W/O ratio and cell concentration were 2 and 25 mg cm −3 , the desulfurization activity was as high as 0.41 mg(total sulfur) g −1 (dry cell weight, DCW) h −1 , ie higher than that reported previously. GC‐AED (gas chromatography with an atomic emission detector) analysis showed that the total reductions for all the C1DBTs and C2DBTs were approximately 100%, 94.63% for C3DBT, and 97.09% for C4DBT (designated C x DBT, where x is the number of alkyl groups attached). The rates of biodesulfurization relate to the number and position of alkyl groups attached to the DBT. Copyright © 2005 Society of Chemical Industry