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A Novel Demetalation Process for Vanadyl- and Nickelporphyrins from Petroleum Residue by Photochemical Reaction and Liquid-Liquid Extraction


A New Methodology Towards Demetalation of Petroleum Residue Based on a Combination of UV Irradiation and Liquid-Liquid Extraction



A new demetalation process for residue oil has been investigated, based on a combination of UV irradiation and liquid-liquid extraction. A simultaneous photoreaction and extraction process, using an oil/water system, was first studied. The demetalation results, for vanadyl(IV)tetraphenylporphyrin (VOTPP) and nickel(II)tetraphenylporphyrin (NiTPP) dissolved in tetralin, were compared with those obtained for actual atmospheric residue (AR). ESR analysis showed that this first process was able to demetalize "free"-type metalloporphyrins, but had difficulty in the demetalation of "bound"-type ones, which are associated strongly with the asphaltenic molecules in AR. To weaken this association and thus convert the bound-type metalloporphyrins to the free-type ones, polar 2-propanol solvent was added to the AR and photoirradiated. The 2-propanol was then removed by evaporation, and the resulting AR was contacted with aqueous HCl solution, into which the resulting vanadium and nickel were successfully removed. According to this latter development of the process, 93% vanadium and 98% nickel were recovered from AR.


Petroleum residue, produced during atmospheric and vacuum distillation of crude oil, contains a high proportion of sulfur, nitrogen, and the heavy metals. Vanadium and nickel are most concentrated in residue oils and are known to occur naturally as vanadyl(IV)- and nickel(II)porphyrins [1]. These metalloporphyrins are difficult to be demetalized during current hydrodemetalation process and leave a metal sulfide deposit on the catalyst, thus causing a corresponding loss in the catalyst activity [2]. An alternative demetalation process, able to be operated under moderate conditions and without the requirements for hydrogen and catalyst, is therefore strongly required. In the present work, a new demetalation processes for residue oil, based on photodecomposition of vanadyl- and nickelporphyrins using UV light and extraction of the resulting materials, is studied, as one of our series works for desulfurization and denitrogenation of light oil and gasoline feedstocks [3, 4].


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