Structural analysis by NMR and FIMS of the tar-sand bitumen of Bemolanga (Malagasy)

The detailed characterization of the tar-sand bitumen of Bemolanga (Malagasy) was performed with the aid of NMR and FIMS techniques. After precipitation of the asphaltenes an elaborate separation of maltenes was carried out by HPLC. The number average molecular weight measurements indicate that this bitumen is much heavier than American bitumens (MW = 900 against 534 for the Athabasca bitumen for example). The modeling shows that the average length of the alkyl chains and the ratio of the number of naphthenic rings to that of aromatic rings increase from the aromatic fractions to the resin fraction and then decrease for the asphaltenes. Moreover, the average length of the alkyl chains is always larger than that in the corresponding fraction of American bitumens.