The nature, distribution and mode of association of vanadium and nickel complexes in the Alberta oil-sand bitumens were investigated using neutron activation analysis (NAA), ultra-violet spectroscopy (UV), liquid chromatography, and mass spectrometry (EI-MS).

The Athabasca, Peace River and Cold Lake bitumens were fractionated into three soluble extracts and an asphaltene solid.

Vanadium and nickel were distributed between the different components of the bitumen. All the vanadium in the extracts was present as vanadyl porphyrin but only a small fraction of the nickel is porphyrinic. The vanadyl porphyrin content of the Athabasca bitumen is 9.52 (mu)g/g (Peace River: 92 (mu)g/g; Cold Lake 77 (mu)g/g) corresponding to 47% of the total vanadium in the bitumen (51% and 40% of Peace River and Cold Lake respectively) the remaining still associated strongly in the asphaltenes.

All five types of porphyrins were present as homologous series with carbon numbers ranging from C(,27)-C(,40). The maxima occur at C(,32) for DPEP series, C(,29)-C(,32) for etio and C(,28) for the diDPEP, rhodo etio and rhodo DPEP. The relative abundance was in the following order: DPEP > etio > diDPEP > rhodo-etio > rhodo-DPEP.

The DPEP/other porphyrin ratios (etio, di-DPEP, etc.), in the bitumen extracts are similar and decrease in the order: Athabasca > Peace River > Cold Lake. The results confirm that biodegradation has no effect on porphyrin distributions and that the bitumens are related geochemically.

The porphyrins distribute in the bitumen extracts as shown by the porphyrin ratios: DPEP/etio ratio; maltenes < pentane extract < methanol-acetone extract. The DPEP/other porphyrin ratios decrease from maltenes to methanol-acetone extract confirming the fractionation of metal complexes in the bitumen which is governed by the relative polarities of the different types of porphyrins.