Abstract
The organic matter in sludges from two Libyan crude oils [Sedra, API = 37, S = 0.39%, N = 0.17%, n-C7 insolubles = 0.73%; and Hamada, API = 39, S = 0.08%, N = 0.06%, n-C7 insolubles = 0.3%] were sub-fractionated with light naphtha (LN, boiling range 20-50°C) and heavy naphtha (HN, boiling range 80-160°C). A reference fractionation with n-heptane (HEPT, boiling point 101°C) was also conducted for comparison purposes. Solvent to sludge ratio was 25:1 and agitation was performed supersonically. The separation of undissolved asphaltenes was achieved by centrifugation.
Results are presented on fractionation of organic matter, elemental analysis of maltenes, and determination of ash and heavy metal contents in the fractions. Average values of 65% and 79% of total sludge weight were separated as a maltene fraction from Hamada and Sedra sludges respectively, using heavy petroleum naphtha as a solvent. Extraction of organics from the asphaltic portion with tetrahydrofuran resulted in a several-fold increase in the expected yield of organics, indicating reaction with the solvent. No such reaction took place when the extraction was performed using toluene.