Influence of the Composition of the Sulfuric Acid Cation Exchanger on the Efficiency of Chromatographic Purification of Petroleum Vanadyl Porphyrins

The development of efficient methods for preconcentration and purification of petroleum metal porphyrins is the necessary condition for further progress of basic and especially applied research concerning the properties of these compounds and their role in oil genesis and maturation. This study deals with chromatographic preparation of high-purity vanadyl porphyrins using a sulfuric acid cation exchanger that can be readily prepared from silica gel and sulfuric acid and is simple in use. At the silica gel : sulfuric acid : water weight ratio of 60 : 15 : 25, the suggested sulfuric acid cation exchanger retains most efficiently nonporphyrin impurities of the asphaltene polar extract, whereas a significant fraction of vanadyl porphyrins (up to ~50%) passes through the chromatographic column virtually without retention with the stationary phase. In contrast to traditional adsorbents, the suggested sulfuric acid cation exchanger allows preparation of spectrally pure vanadyl porphyrins in one chromatographic purification step, thus ensuring the minimal consumption of the eluent and adsorbent. High purity of the vanadyl porphyrins obtained was confirmed by mass-spectrometric and spectroscopic methods of analysis.