Fractionations of Nonporphyrin Complexes of Vanadium and Nickel from Boscan Crude Oil

Samples containing vanadium and nickel nonporphyrin complexes were isolated from Boscan crude oil from Venezuela. Chromatographic studies indicated that a broad molecular weight range of components existed so that silica packings having a 300 Å average pore diameter were superior to those in the range 60 to 100 Å due to greater permeation. Solvents having widely different polarities and selectivities were needed for elution of nonporphyrins from 300 Å pore diameter silica derivatized with trimethylchlorosilane. Successive solvents eluted different percentages of the metals and of UV-visible absorbing components. Larger molecular-weight species, which contained the bulk of the metals, were eluted by chloroform, methylene chloride, and tetrahydrofuran. Results also suggested the existence of slow "equilibria" between high and low molecular weight species within a particular nonporphyrin fraction.