Extraction of Dibenzothiophenes from Petroleum Feedstocks Using a Ruthenium Complex in Aqueous Solution

In an effort to demonstrate that Ru(NH 3 ) 5 (H 2 O) 2+ can be used to remove dibenzothiophene from hydrotreated petroleum feedstocks, this metal complex was reacted with a variety of thiophenes (Th*), including dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-Me 2 DBT) to give complexes of the type Ru(NH 3 ) 5 (Th*) 2+ . This ability of Ru(NH 3 ) 5 (H 2 O) 2+ to bind to thiophenes has been used in an extraction process in which a solution of Ru(NH 3 ) 5 (H 2 O) 2+ in 70% DMF and 30% H 2 O is contacted with a simulated petroleum feedstock (45% toluene/55% hexanes) containing 400 ppm of DBT. One extraction removes 50% of the DBT from the feedstock phase as Ru(NH 3 ) 5 (DBT) 2+, which is present in the DMF/H 2 O phase. Five successive extractions reduce the amount of DBT in the simulated feedstock from 400 to 25 ppm. The Ru(NH 3 ) 5 (H 2 O) 2+ extractant can be regenerated from the Ru(NH 3 ) 5 (DBT) 2+ either by air-oxidation followed by H 2 -reduction or by displacement of the DBT by adding H 2 O to the DMF/H 2 O phase. Extraction of 4,6-Me 2 DBT from the simulated feedstock using Ru(NH 3 ) 5 (H 2 O) 2+ in 70% N, N -dimethylacetamide and 30% H 2 O was less successful as the 4,6-Me 2 DBT concentration was only reduced from 400 to 340 ppm.