A comparative study of products derived from Rundle and Stuart shale oils and petroleum lubricating oil base stocks (based on n.m.r., molecular weight and elemental analysis)

As part of a study to evaluate the potential of shale oils for lubricating oil production, samples from the Rundle and Stuart oil shale deposits in Australia have been processed to produce a range of products which were then characterized by 1H and 13C high resolution nuclear magnetic resonance (n.m.r.) techniques, molecular weight determination and elemental analysis. The data have been compared with that obtained for two petroleum derived lubricating oil base stock samples. The comparison shows that the products derived from Rundle and Stuart shale oils in the lubricating oil boiling range have lower molecular weight and a lower hydrogen content. The lubricating oil samples are shown to contain monoaromatic rings, with one or more branched, long, alkyl side chains per ring, some naphthenic but no olefinic structure. The shale oil samples show distinct differences, with the distillate being monoaromatic with some polyaromatic and naphthenic structures, but with less alkyl substitution. The alkyl side chains are unbranched and contain some olefinic bonds. The maltenes are in turn less substituted and have less naphthenic structure. The alkylation and dewaxing processing steps did not significantly modify the structures of the shale oil products, while in the hydrogenation process some of the olefinic material was modified to paraffinic. Further reduction of the aromatic content of the shale oil is required to improve the prospects of producing a lubricating oil base stock.