CHARACTERIZATION OF VANADIUM COMPOUNDS IN SELECTED CRUDES I. PORPHYRIN AND NON-PORPHYRIN SEPARATION

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Abstract
We have applied size-exclusion chromatography (SEC-HPLC) and reversed-phase chromatography (RP-HPLC), with element specific detection, [Inductively coupled and direct current plasma atomic emission spectroscopy (ICP and DCP)], to selected crude oils –– Boscan, Beta, Morichal, Arabian Heavy, and Maya –– and their separated fractions. By these procedures, we have further characterized both the V porphyrin and the V non-porphyrin compounds. From the SEC-HPLC-ICP profiles of the heavy crude oils we found the V compounds generally have a bimodal distribution, with maxima at approx. 800 and 9000 polystyrene equivalent (PS) molecular weight (MW). Arabian Heavy, though, had relatively few of the small V compounds. The crude oils were separated into porphyrin and non-porphyrin fractions by methanol extraction. From the SEC-HPLC-ICP profiles of the porphyrin fraction, we Identified and quantitated the maximum at approx. MW 800 (PS) as being V porphyrins. The remaining V compounds are non-porphyrin.