The Study on Petroporphyrins in Crude Oil and Marine Fuels
|School||Dalian Maritime University|
|Course||Environmental Science and Engineering|
|Keywords||Crude oil Marine fuels Petroporphyrins UV-Vis HPLC-MS|
With the increase in demand and consumption of petroleum, the accidents of marine oil spill frequently occur more and more, which seriously damage marine ecological environment and even endanger human health. Petroporphyrins is called as "micro-fossil" in crude oil and oil rock, and is the product in the process of oil formation, and have two main forms such as nickel porphyrins and vanadium porphyrins. During the processing of oil, most of the nickel and vanadium porphyrins turn into heavy residues from the distillate unit. Consequently, there are more petroporphyrins in relative oil products. Therefore, petroporphyrins as "oil fingerprint", plays an important role in identification of spilled oil sources, can be used for investigating perpetrator responsibility. It is significative for protection of the marine environment.In this work, three crude oils such as Iraq oil, United Arab Emirates oil, Malaysia oil and marine fuels were used as study object. The metalloporphyrins in oils were separated from a large number of oil matrixes composed of colloid, asphaltene, hydrocarbon and aromatic hydrocarbon by solvent extraction and column chromatography purification. The metalloporphyrins were qualitatively and quantitative-ly analyzed using graphite furnace atomic absorption spectrometry (GF-AAS), ultraviolet-visible spectrophotometry (UV-Vis) and high performance liquid chromatography combining with mass spectrometry (HPLC-MS). The results were obtained as follows:1. Nickel and vanadium porphyrins of the four oil samples can be effectively extracted from the matrixes by acetonitrile. The extraction ratios of vanadium porphyrins are higher than those of nickel porphyrins. Besides, the extraction effect on metalloporphyrins in marine fuels is better than that in crude oils.2. The rough extracts of petroporphyrins were analyzed by UV-Vis. Only the vanadium porphyrins in Iraq and United Arab Emirates crude oil can be detected. While no characteristic absorbtion band of petroporphyrins appears in Malysia crude oil and marine fuels. After purified by column chromatography, three kinds of crude oil and marine fuels contain nickel and vanadium porphyrins. The nickel porphyrins of the four oil samples are enriched in which eluent was cyclohexane/dichloromethane (4:1, v/v). The vanadium porphyrins of Iraq and United Arab Emirates crude oils are enriched in the eluent with cyclohexane/dichloromethane (1:1,1:4and0:1, v/v), while the ones in Malaysia crude oil and marine fuels are only enriched in the eluent with cyclohexane/dichloromethane (1:4, v/v).As shown in UV-Vis spectra results, in Iraq crude oil, the nickel porphyrins of ETIO and DPEP types account for89.0%and11.0%, respectively, the vanadium porphyrins of ETIO and DPEP types account for73.8%and26.2%, respectively. In United Arab Emirates crude oil, the nickel porphyrins types are all ETIO, the vanadium porphyrins of ETIO and DPEP types account for79.5%and20.5%, respectively. In Malysia crude oil, the nickel and vanadium porphyrins types are all ETIO. While in marine fuels, the nickel porphyrins types are all ETIO, the vanadium porphyrins of ETIO and DPEP types account for70.0%and30.0%, respectively.3. HPLC-MS analysis indicates that the types of the three crude oils are apparently more than those of marine fuels.The nickel porphyrins as ETIO type in crude oils is dominate, followed as DPEP type. In addition, Iraq crude oil also contains Rhodo-ETIO, Rhodo-DPEP and Di-DPEP types. United Arab Emirates crude oil contains a little Rhodo-ETIO and Rhodo-DPEP types. Malaysia crude oil contains Rhodo-ETIO type. The vanadium porphyrins as ETIO type in crude oils are also dominate, followed as DPEP type. The vanadium porphyrin types are the most in Iraq and United Arab Emirates crude oil, such as Rhodo-ETIO, Rhodo-DPEP, Di-DPEP and Rhodo-Di-DPEP types. Malaysia crude oil contains Rhodo-ETIO type.The types of nickel and vanndium porphyrins are only two in marine fuels, dominated as ETIO and followed as DPEP.