Oil in the Sea IV Inputs, Fates, and Effects (2022) / Chapter Skim
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2 Petroleum as a Complex Chemical Mixture
2 Petroleum as a Complex Chemical Mixture
Pages 25-54
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From page 25... ...
This chapter provides a brief overview of the classification of petroleum oils used by industry as it produces, 2.1.2 Definitions and Classifications of Petroleum transports, and refines them by means of distillation and petroleum cracking; and the classifications of petroleum The fact that petroleum is a complex mixture of thousands oils relevant to oil spill response. Petroleum and many of of chemicals has been known for many decades.
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From page 26... ...
FIGURE 2.1 Components of typical crude oil types. NOTES: Names of the crude oil types on the x-axis and percentages on the y-axis of the four major commonly used categories of molecules in crude oils: saturates, aromatics, resins, and asphaltenes (identified as SARA within the petroleum industry and the scientific communities involved in responses to oil spills and for oil inputs, fates and effects)
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From page 27... ...
API gravity is have emerged recently or are of emerging importance for related to the specific gravity of an oil, by the formula API a variety of factors including ease of fulfilling demand for gravity = (141.5/specific gravity at 15.6°C)
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From page 28... ...
According environment and, it is therefore important to keep track of to a narrower definition, marine diesel oil is a blend of distillate chemical compositions and potential fates and effects of such fuels and a very low proportion of heavy fuel oil2. spills or chronic inputs.
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The information pressure and temperature conditions at the Earth's surface. in this figure should be used as a guide when viewing the In general, these include chemical compounds of carbon and more traditional representation of molecular structures used hydrogen atoms with relatively simple, or branched, shortin other figures in this report and in the scientific literature chain or cyclic molecules of low molecular weight.
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From page 30... ...
. These are very important compounds from the perspective FIGURE 2.5 Chemical structures of the group of monoaromatic of human health concern during oil spills, especially for hydrocarbons collectively known as BTEX (benzene, toluene, oil spill responders for at-sea oil spills (see Chapter 4)
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From page 31... ...
, resins (typically cyclic structures containing one or branched alkanes, so named because of their structural more heteroatoms in addition to carbon and hydrogen) , and relationship to a repeated unit of the isoprene moiety (e.g., asphaltenes (similar in chemical composition to resins but phytane, β-carotane, and lycopane)
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From page 32... ...
32 OIL IN THE SEA IV FIGURE 2.7 Three-dimensional rendering of the petroleum biomarker compound cholestane and comparison to two-dimensional drawing of the same molecule. NOTE: The positioning of the carbon-hydrogen bond at the three position points above the plane of the molecule is designated 3β and that at the five position points below the plane 5α.
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From page 33... ...
Asphaltenes The various configurations of the fused rings influence are high molecular weight compounds typically of undefined physical and chemical properties of the compounds such as structures, although some tentative structures or parts of volatility, solubility, and also the chemical and biological reac- structures have been proposed. A recent review of asphaltene tivity of the specific PAH or PAC.
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From page 34... ...
Elemental The molecular weights and various molecular configusulfur and H2S (hydrogen sulfide) are present in some crude rations of petroleum hydrocarbons (and any molecule for oils -- the "sour crude oils." that matter)
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-- are there biological indicators of adverse "The organic compounds in sediments, rocks, and crude oils whose health effects? carbon structures or skeletons can be traced back to a living organism • Susceptibility -- do variations in genes place a person at higher are called biomarkers.
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contained coal particles and analysis by gas chroma 2. Microbial biochemical and geochemical transforma- tography methods used to analyze petroleum hydro tions of natural organic matter in soils and surface carbons (see Analytical Chemistry Methods section)
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Hydrocarbons, resins, and asphaltenes present in the benzene molecule. As such they overlap in the jet natural oil seeps have a compositional complexity that fuel–fuel oil range of molecular weights for petroleum is the same as or similar to that of oil inputs from oil chemicals.
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From page 38... ...
Furthermore, all of the preceding coupled two decades in towed underwater vehicles, remotely operwith the appropriate analytical methods will provide the most ated underwater vehicles, autonomous underwater vehicles, useful data if there is attention to the details of appropriate and associated sensor developments. sampling plans to answer the questions about responses to The preceding applies not only to oil spill response and oil spills and inputs, fates, and effects of oil spills or chronic damage assessment but also to research activities focused inputs (individually or in combination)
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From page 39... ...
When no gas phase is present, immiscible phase when in contact with water and/or air; all compounds are present in the liquid-phase petroleum, they may either be crude oils or refined products. NAPLs are and some of the lightest components, such as methane, may typically classified as either light nonaqueous phase liquids be thought of as fully dissolved in the liquid phase.
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From page 40... ...
free gas; hence, hydrate armoring may interfere with dissolu tion of natural gas bubbles in seawater. The implications of hydrates on marine oil spills are discussed in more detail in 2.2.1.2 Weathered Oil Section 5.3.3, on deep-water processes for acute marine oil Historically, the general term weathering has been used spills, and Section 5.4.1, on natural seeps.
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in sea water 2 years (GC-MS) coupled to computer systems for data processing after the DWH oil spill (Bianchi et al., 2014)
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DWH oil spill, provides references from numerous studies Given the complexity of the mixture of GC-amenable other than those focused on the DWH. compounds in fuel oils and crude oils, analysis by capillary Several of the advances in methodology have focused GC will not completely resolve all the compounds present.
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The UCM is especially off the top of the scale, then the UCM would be apparent prominent as a feature in some weathered and biodegraded in that chromatogram. That is, those UCM compounds are fuel oils and crude oils.
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. In fates and effects assessments and research, of crude oils and fuel oils are not amenable to conventional the method provides significantly better chemical composigas chromatography, that is, many of the resins and the tion data to unravel or support important aspects of these asphaltenes had not been analyzed to an appreciable extent assessments and research.
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spilled oil and to fate and effects assessments and research (e.g., the M/V Cosco Busan oil spill [Lemkau et al., 2010] , Fourier transform ion cyclotron resonance mass spectromthe Hebei Spirit oil spill [Yim et al., 2012]
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46 OIL IN THE SEA IV FIGURE 2.14 Comparison of three-dimensional surface rendering (mountain plot)
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Petroleum as a Complex Chemical Mixture 47 FIGURE 2.15 GC×GC FID chromatograms of petroleum biomarkers from Macondo crude oil. A zoomed in view of a GC×GC FID Mountain plot (see Figure 2.14)
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transform-ion cyclotron resonance-mass spectrometry (High There are some distinctive signatures for δ13C among and Mag FT-ICR-MS) has expanded the analytical chemistry between various hydrocarbons in petroleum that assist with window to encompass the higher molecular weight com- identification of the presence of petroleum hydrocarbons pounds of oil composition beyond the GC-amenable frac- and, on occasion, with forensics analyses of spilled oils.
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. Irrespective of what methods are used and which com The advances in analytical chemistry methods described pounds or summations of compounds are reported, there is previously require judicious choices, depending on the ques- a need for adequate quality assurances and quality control tions being asked related to the samples to be analyzed, such (QA/QC)
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. "Big Data" Issue Irrespective of the thermodynamic model used, oil composi tion is normally described by quantifying the abundance of both Sampling and analytical methods for forensic analyses individual molecules and groups of molecules having similar and for assessing the fates and effects of oil spills and other behavior.
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From page 51... ...
The PR EOS predicts the density of the gas and solubility for >C6 aromatics based on the molecular weight liquid phases of the mixture and the fugacities of each com- and component density. They then estimate the solubility of ponent in the mixture given the component properties of the each component from the whole petroleum liquid using the molecular weight, acentric factor, critical point temperature, oil–water partition coefficient, which they compute from a pressure and volume, and the binary interaction coefficients.
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From page 52... ...
Correlation equation methods to compute benzene solubility from These examples show the ranges of predicted benzene solubility petroleum mixtures include using the octanol-water partition coefficient from a light sweet crude oil using different modeling approaches. Despite Kow or the pure-compound solubilities with mole fractions and enhance the complex thermodynamics of the gas–liquid equilibrium, each of the ment factors.
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MS, GC-MS-MS-MS, FT-ICR-MS, and high magnetic field FT-ICR-MS have been tested in several studies and are ready Conclusion -- Modeling: Models to predict the properties for more routine use to provide much needed more detailed of petroleum fluids, including mixtures with gas, have chemical compositional data pertinent to the questions being improved recently, buoyed partly by the better elucidation asked in forensic analyses for spilled oil and chronic inputs, of the composition of petroleum mixtures using advanced and understanding fates and effects of various inputs of oil analytical methods. to the environment.
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