The Study On Characteristics Of Vanadium Porphyrins Compound In Middle East Crude Oil

In the recent years, the demands for crude oil are rapid increasing with economic development in China, thus the occurrence probability of oil spills is more frequent, the marine environment was seriously damaged. Petroleum porphyrins are the intermediates during crude oil formation process, they have the characteristics of "microfossils". Therefore, it is significance to use petroleum porphyrins as a chemical fingerprint parameter to identify oil spills source, and investigate the perpetrators responsibility and protect marine life.In this study, Middle Eastern crude oil from Saudi Arabia Arabia, Kuwait and Iraq were selected as samples. They were extracted by Soxhlet extraction using acetonitrile as solvent, and then the extracts were separated by elution with different gradient of cyclohexane:dichloromethane (V:V=2:1;1:9;0:1) in column chromatography. Nickel or vanadium porphyrin in extracts and fractions were detected using ultraviolet-visible spectrophotometry (UV-VIS), and the type of vanadium porphyrin and the distribution of carbon number were analyzed by high performance liquid chromatography mass spectrometry (HPLC-MS).The experimental results were obtained as follows:(1) The recovery of vanadium porphyrin in Saudi Arabia Arabia, Kuwait, Iraq was49.6%,56.5%,62.5%, respectively, using acetonitrile as solvent.(2) Nickel porphyrin obtained from column separation concentrated in fraction1(cyclohexane:dichloromethane (V:V=2:1)), vanadium porphyrin obtained from column separation concentrated in fraction2(cyclohexane:methyl chloride (V:V1:9)).(3) According to UV-VIS spectra, vanadium porphyrin in crude oil of Saudi Arabia Arabia belong to ETIO type. The majority of vanadium porphyrin in crude oil of Kuwaiti and Iraq belong to ETIO type, accounting for85.7%and88.6%, respectively, and followed by the DPEP type, accounted for14.3%and11.4%, respectively.(4) According to mass spectrum of average molecular weight of vanadium porphyrins, vanadium porphyrin at m/z495is C29-RHODO-ETIO-VO type in Saudi Arabia crude oil, vanadium porphyrin at m/z555is C33-DPEP-VO type in Kuwait crude oil, and vanadium porphyrin at m/z537is C32-RHODO-ETIO-VO type in Iraqi crude oil.In addition, in contrast with China’s Tahe and Venezuela380crude oil, the contents of ETIO vanadium porphyrin in Saudi Arabia and Iraq crude oil are much more than them.