Porphyrin fractions, demetallation

The separation of the extract into polycyclic hydrocarbons, and nickel and vanadium porphyrin fractions was accomplished using CCl /CHClo chromatography with Kieselgel (Merck). The vanadium porpnyrin fraction was then further separated into seven major fractions using a variety of column chromatography procedures. Demetallation of the porphyrin fractions was carried out with methanesulphonic acid (Merck) using published procedures (6). 

Attempts to demetallate the various porphyrin fractions appeared partly successful only in the case of the nickel porphyrins and for sample 3, while demetallation of samples 630, 422 and 4422 yielded no porphyrin type compounds at all. HPLC runs on the demetallated nickel porphyrins and the vanadium porphyrins from fraction 3 showed these to be significantly different. Similar observations have been made previously (12) and may explain why the nickel and vanadium porphyrins appear to have different distributions in the drill cores. However,... 

Therefore, heavy metals must be removed from crude oil fractions. Various processes are used chemical or adsorptive removal of the porphyrins, or demetallation by hydrogenation and binding the metals on AI2O3. Another effective method is the use of additives. For example, the heavy metals can be alloyed by adding antimony, after which they are deposited on the catalyst in a different form. 

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