Annex 6.D.26

Characterization of naphthenic acids in crude oils and refined petroleum products. 559

Characterization of Naphthenic Acids in Crude Oils and Refined Petroleum Products

Chun Yang, Gong Zhang, Mariam Serban, Graeme Koivu, Zeyu Yang, Bruce Hollebone, Patrick Lambert, and Carl E. Brown Emergencies Science and Technology Section Science and Technology Branch, Environment and Climate Change Canada Ottawa, Ontario, Canada [email protected]

Abstract Naphthenic acids (NAs) or naphthenic acid fraction compounds (NAFCs) are generally recognized as a family of aliphatic and alicyclic carboxylic acids naturally occurring in petroleum. NAs from petroleum industry activities and oil spills have led to increasing environmental concern in recent years due to their toxicity. This study presents a characterization of naphthenic acids of NA isomers in a number of crude oils and refined petroleum products including light and mid-range distillate fuels, heavy fuels, and lubricating oils collected from various sources. NAs with unsaturated degree of Z-2 to Z-24 and carbon number ranging from 6 to 60 were determined by liquid chromatography-high resolution mass spectrometry (LC­ HRMS). NA profiles vary from oil to oil. Conventional light oils generally contain low concentrations of NAs, while heavy crudes and oil sands bitumen contain significant levels of NAs. NAs in Federated and Alaska North Slope crude oils are relatively low with 0 2 NA species to be only 139 µgig and 419 µgig, respectively, while their abundances in bitumen are as high as 7,994 µgig in Venezuelan Orinoco bitumen. The ratio of even to odd (E/O) carbon number NAs in petroleum oils is all close to 1.0 for Z-2 to Z-24 NAs. Z-0 to Z-12 series in bitumen totally account for about 90% of total determined NAs and Z-14 to Z-24 NAs make up the rest of about 10%. Moreover, Z-4 (two rings) NAs are the most predominant in all oil samples. In terms of distribution according to carbon number, C6 to C.~4 NAs totally make up about 50% ofNAs in oil sands bitumen, and C~j to C60 account for about half of total NAs. Caustic extraction of oil sand bitumen partially transports NAs into oil sands process-affected water (OSPW). C6 to C24 NAs totally constitute about 95% of total NAs determined in an OSPW sample. Evaporation (up to 23.6% by weight) weathering increased total concentration but unlikely affected the distribution of NAs in dilbit.

1 Introduction Naphthenic acids (NAs) refers collectively to a family of cycloaliphatic carboxylic acids present in crude oil, which have an empirical formula of CnH2n+zOi, where n is the number of carbon and z is zero or negative even integer presenting the hydrogen deficiency (unsaturated degree) of a NA molecule. The definition has recently been expanded to the naphthenic acid fraction component (NAFC), which includes unsaturated and aromatic NA derivatives, increased oxygen content and compounds containing nitrogen and/or sulfur (Headley et al., 2009; 2013; Grewer et al., 2010). A recent study observed the formation of oxygenated residues in sediment due to oil weathering after the Deepwater Horizon disaster, and biodegradation and photooxidation likely contributed to the oxygenation (Aeppli et al., 2012). NAs could be applied as an indicator for oil contamination to in an oil-spilled area (Wan et al., 2014). A study on the Hebei Spirit oil spill in December 2007 found that concentrations ofNAs are many times greater than those of

Yang, C .• G . Zhang, M. Serhan, G. Koiw. Z. Yang, B.P. Hollebone, P.G. Lambert. and C.E . Brown. Characterization of Naphlhenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty-first AMOP Technical Seminar. Environment and Climate Change Canada. Ottawa, ON. Canada. pp. 559-575. 2018. 560

polycyclic aromatic hydrocarbons (PAHs) in the same sediment samples (Wan et al., 2014). They reported that NAs (7.8- 130 mg kg- 1 dw) were 50- 100 times higher than the total PAHs concentrations (0.077- 2.5 mg kg- 1 dw) in the sediment samples collected in the affected area. Considering the high solubility ofNAs compared to those of PAHs, concentrations ofNAs in water samples would be much higher than those of PAHs in oil spill affected areas. Naphthenic acids released to the environment tend to bind to soil/sediments, with negligible fractions partitioning to air, water or biota (Rogers et al., 2002). However, low molecular weight naphthenic acid constituents, if present, would be expected to partition to some degree into water depending on their pKa characteristics and the pH of the water (API, 2012). There is a growing interest in the monitoring of naphthenic acids to assess their ecological risk in the environment. This surge is driven by the increased activity in oil sands environmental monitoring programs in Canada, the exponential increase in research studies on the isolation and toxicity identification of components in oil sands process-affected water (OSPW), and the analytical requirements for development of technologies for treatment ofOSPW (Brown and Ulrich, 2015; Zhang et al., 2016; Headley and McMartin, 2004; Frank et al., 2008, Headley et al., 2009; Grew er et al., 201 O; Jones et al., 2011 ). There has been additional impetus due to the parallel studies to control corrosion from naphthenic acids during the mining and refining of heavy bitumen and crude oils (Slavcheva et al., 1999; Headly et al., 2016). Naphthenic acid corrosion is a major concern for the oil refinery business. It was reported that naphthenic acid corrosion occurs over the temperature range of about 200-400°C, at higher temperature the naphthenic acids decompose (Slavcheva et al., 1999). It was also reported that the corrosivity of NAs is related to their molecular mass and the total acid number. NAs are furhter classified into a and p groups in this regard, the fom1er corresponding to low molecular weight (MW, - 125-425 amu, equivalent to -C7 to C30 NAs) NAs and exhibiting very high corrosivity and the latter having high MW (-325-900 amu)and low corrosivity (Kane and Chambers, 2011; Ramirez-Corredores, 2017). There are already extensive research on the analysis and environmental behaviorus of naphthenic acids, and some reviews addressed recent development on NA researches (Headley et al., 2004; 2009; 2013; 2016; Brown and Ulrich, 2015). Hughey et al. (2002) analyzed acidic NSO compounds in three crude oils of different geochemical origins by negative ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Compositional differences, other than sulfur content, also reflect geochemistry. Acids are common constituents in young and immature crude oils. Some of the naphthenic acids present in heavy crude oils are original components of the oil and retain biomarker skeletons (e.g., the hopane skeleton). Most acids, however, are formed by chemical or biochemical oxidation of the original crude molecules after migration into the reservoir (Hughey et al., 2002). Holowenko et al. (2002) found that the "C21+cluster"', the group ofNAs with carbon numbers 22- 33, in Z families 0 to -12", is a convenient means of measuring differences among NAs from various oil sands process-affected waters. This was particularly useful for comparing different NAs distributions in process-affected waters with various degrees of acute toxicity. In recent years, we have developed a solid phase extraction method to effectively isolate NAFCs from other petroleum components and have applied high resolution LC-Orbitrap mass spectrometry in the identification and quantitation of these compounds (Zhang et al., 2014; 2016). To gain better understanding of NA concentration and distribution profiles in crude oils and petroleum products, this study presents a quantitative analysis of NA isomers in a number of crude oils and refined petroleum products including light and mid-range distillate fuels, heavy

Yang, C., G. Zhang, M. Serhan, G Koivu, Z. Yang. BP. Hollebone. P.G. Lambert, and C.E. Brown, Characterization of Naphlhenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty-first AMOP Technical Seminar. Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559·575, 2018. 561

fuels, and lubricating oils collected from various sources. NAs with unsaturated degree of Z-4 to Z-24 and carbon number ranging from 6 to 60 were determined by liquid chromatography-high resolution mass spectrometry.

2 Experimental 2.1 Chemicals and materials Solvents ofHPLC grade methanol, isopropanol, and acetonitrile were supplied by Sigma­ Aldrich (St. Louis, MO). Hexane and dichloromethane (DCM) were used as purchased (Caledon Laboratory Chemicals, Ontario). Ultrapure water was prepared from a Milli-Q plus water purification system (Millipore, Billerica, MA). D21-myristic acid (d21-C 14:o) and 13 straight chain saturated fatty acids (SSFA) compounds from C6 to C30 (even number only) were supplied by Sigma-Aldrich (St. Louis, MO). The surrogate solution for oil fingerprinting analysis was custom-made by NSI lab solutions (Raleigh, USA), containing 200 µg/mL of o-terphenyl, 200 µg/mL of C24D50 and a mixture of deuterated naphthalene, acenaphthene, phenanthrene, benz[a]anthracene, and perylene (10 µg/mL each). Silica gel (Grade 644, 100- 200 mesh, 150 A) was supplied by Fisher Scientific (Fair Lawn, NJ, USA). Silica gel is successively cleaned with acetone, hexane and dichloromethane. Then, silica gel is activated for at least 20 hours at approximately 180°C ± 20°C prior to use.

2.2 Sample preparation All crude oil and refined petroleum products used in this work were selected from the oil archive of the Emergencies Science and Technology Section (ESTS) of Environment and Climate Change Canada (Table 1). The oils studied include conventional crude oil and oil sands bitumen from different regions, and various types of refined petroleum products such as diesel, heavy fuel oils and lubricating oil. An aliquot of oil solution containing about 16 mg of neat oil was loaded on a 3 .0 g silica gel column which was preconditioned with hexane. The sample was eluted sequentially using 12 mL hexane (Fl) and 15 ml DCM/hexane (1: 1, F2). These fractions were separately concentrated using a gentle flow of nitrogen to suitable volumes and spiked with d 14-terphenyl as an internal standard (final concentration of 1.0 µg/mL), and then adjusted to a volume of 1.0 ml for GC-MS analyses (results were not presented in this report). The polar fractions in the extract were then further eluted by 20 ml of DCM/acetone (98:2, F3) and DCM/methanol/formic acid (50:50:0.1, F4), respectively. F3 and F4 were dried gently under nitrogen stream. The residual was then reconstituted into 1.0 ml of isopropanol containing 1.0 mg/L of D27-myristic acid as internal standard for HPLC-Orbitrap MS analysis.

2.3 LC-MS analysis of Naphthenic Acids The instrument employed for the analysis of naphthenic acids was an Accela HPLC - Exactive Orbitrap Mass Spectrometer System (Thermo Fisher Scientific, San Jose, CA) equipped with electrospray ionization interface (ESI). Chromatographic separation was performed on an Agilent lnfinitylab Poroshell 120 reversed-phase EC-C8 column (2.1 mm x 100 mm, 2.7 µm). Gradient elution was performed with a mobile phase of2 mM ammonium acetate in water (A), 95% methanol-5.0% water with 2 mM ammonium acetate (B) and 85% isopropanol-10% toluene-5% water with 2 mM ammonium acetate (C). The gradient LC program was conducted at a flow rate of0.4 mUmin and engaged three stages as follows: stage I, 95% A and 5% B for 5

Yang, C., G. Zhang. M. Serhan. G. Koivu. Z. Yang . B.P. Hollebone. P.G. Lambert and C.E. Brown. Characterization of Naphthenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technical Seminar, Environment and Climate Change Canada. Ottawa. ON. Canada , PP- 559·575. 2018. min, followed by a linear gradient ramp to 100% B at 20 min; stage II, ramp up linearly to 10% B-90% C at 40 min, held for 5 min; stage III, ramp back to 100% B in 1 min (between B and C), hold for 2 min, then linearly returning to 5% Bin 1 min (between A and B) and remaining for 5 min of equilibration prior to the next injection. Injection volume was set at 5 µL using a syringe flushed with isopropanol. The Orbitrap mass spectrometer was operated in ESI negative mode. Data was acquired in full scan mode from m/z 100 to m/z 1,600 and ultrahigh mass resolution was used (FWHM = 100,000 at 1 Hz, and a maximum ion injection time of 100 ms). The negative ion of dimer of acetic acid (m/z 119.03498) was used as lock mass for scan-to-scan calibration correction to get less than 1 ppm mass accuracy. ESI parameters were as follows: sheath gas, 30; auxiliary gas, 10; spray voltage, 4.0 kV; tube lens voltage, -85 V; skimmer, -18 V; capillary voltage, -30 V; and capillary temperature, 300°C. The identification of naphthenic acids was based on reference materials including Merichem and ESTS in-house Alberta Oil Sands bitumen extracted by DCM. NAs were identified and integrated at their monoisotopic mass of [M-Hr with a 5.0 ppm mass window. According to the NAs empirical formulae (CnH2n+z0 1), a custom database of NA formulae was generated by ExactFinder (version 1.0, Thermo Scientific) spanning n = 6-..60 and Z Cl 0 - -24 for all possible ions of 0 2 species. Total NAs were quantified based on integration of group ions by carbon numbers (C6 to C.m) and hydrogen atom deficiency (Z-0 to Z-24) using 50 µglmL Merichem (from Naphthenic Acids lnterlab Study Working Group, 2014) as the quantitation standard (Zhang et al., 2014; 2016).

3 Results and Discussion 3.1 NA profiles of Crude Oils Naphthenic acids are natural components of nearly all crude oils due to insufficient catagenesis of the deposit, the conversion of kerogens to hydrocarbons or in-reservoir incomplete aerobic biodegradation of petroleum hydrocarbons by bacteria (Kannel and Gan, 2012; Brown and Ulrich, 2015). Although the presence of naphthenic acids has been established in almost all types of crude oil, only certain naphthenic and asphalt based crudes contain amounts that are high enough to require treatment in order to meet product specifications (API, 2012). While there is no correlation with API gravity, the most acidic crude oils are also heavy (Ramirez­ Corredores, 2017). Heavy crudes have the highest acid content, while paraffinic crudes usually have low acid content. Table 1 summarizes the concentrations of NAs of 0 2 species with a carbon number from C6 to C60 and Z of0- -24 in studied crude oils and refined products determined by LC-MS. Conventional crude oils generally contain relatively low concentrations ofNAs, while heavy crudes and bitumen contain significant levels ofNAs. NAs in conventional Federated and Alaska North Slope crude oils are relatively low, only 139 µgig and 419 µgig, respectively, while their abundances in bitumen are as high as 7,994 µgig in Venezuelan Orinoco bitumen. Diluted bitumen or dilbit is a mixture of bitumen with one or more light petroleum products, typically natural-gas condensates such as naphtha. NAs in dilbit are largely attributed to bitumen and their concentrations vary depending on the portion of light diluent. Winter dilbit consists ofa higher percentage of light diluent, resulting in their NAs concentrations to be slightly lower than that of summer dilbit. As noted from Table 1, evaporation weathering was unlikely to decrease the abundance of NAs in the dilbits. Although the light component of diluent and some small NAs were removed by evaporation, the concentrations ofNAs in the weathered dilbits increased due to accumulation of larger NA isomers.

Yang, C, G. Zhang, M. Serhan, G. Koivu, Z. Yang. BP. Hol:ebone, P.G. lambert. and CE. Brown, Characterization of Naphlhenlc Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technical Seminar, Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559·575, 2018. 563

Figure 1 shows the relative intensity according to carbon number and Z value in different oil samples. Figure 2 illustrates the distribution of different acidic species in test crude oils and refined products in terms of carbon number and hydrogen deficiency. Naphthenic acids were determined in a very wide carbon and Z-range for both crude oils and petroleum products. Figure 1 also shows the NA distribution by carbon number. The oil sands bitumen was composed of a greater proportion of higher molecular weight naphthenic acid isomers than the other samples. For bitumen, C6 to C24 totally account for only about 50% of NAs, with C25 to C6o accounting for about the other half of total NAs. It is clear that refined petroleum products have very distinguishable profiles in terms of abundance, carbon range and Z value in comparison with studied crude oils. Predictably diesel No 2 was found to have a narrow carbon and Z range of NAs. Hughey et al. (2002) reported that Z-values for acids range from 0 to -38 in Chinese, North American and Middle Eastern crudes. Naphthenic acids (e.g. acids with fused cyclohexane rings) are likely the most prevalent acids in Chinese crude as evidenced by the relative high abundances of species with smaller Z-values (0 - -8). Based on Z-values, the acids should contain no more than five aromatic rings. The 0 2 species in studied oil samples range from Z-0 (saturated) up to Z-24 (polyaromatic) acids. As observed from Figures 1 and 2, NA profiles obviously vary from oil to oil. NAs in oils are dominated by Z-2 (one ring) or Z-4 (two rings) species. For instance, about 42.3% and 22.6%, and 23.6% and 28.1% of total NAs were determined in Mississippi Canyon crude oil and Cold Lake Bitumen were identified to be Z-2 and Z-4 series, respectively. For most oil studied, Z-0 to Z-12 NAs totally constitute about 90% ofNAs, while Z-14 to Z-24 series totally account for less than I 0%. Besides the unsaturated or cyclic NAs (with a negative Z-value), saturated carboxylic acids (Z = 0) were also detected in all studied oil samples in considerable concentration. Behar and Albrechi (1984) reported dominant chromatographic peaks of linear C16 and C 1s saturated acids. The occurrence of these saturated acids in oils which are not biodegraded may indicate a recent contamination during storage or production since these acids are usually not predominant in mature sediments. C7-Z-8 NA was found at high concentration in some oil with contribution of benzoic acid (C7H60 2). This chemical is used as drilling mud additive for crude oil recovery applications, but we are not sure if this is the explanation for the high content of benzoic acid. During analysis of environmental samples associated with petroleum contamination, a wide range of biogenic organic acids could be fit into traditional NA definition, which brought up a technique difficult to identify NAs derived resources: biogenic or petrogenic NAs. As summarized in Table 1, E/O ratio is around 1.0 for Z-2 to Z-24 species. Zhang et al. (2016) found that NA profiles of environmental sediment samples are significantly different from oils and OSPW. E/O ratio ranged from 2.1 to 9.7 for studied sediment samples. The dominated isomers could differentiate them from other commercial NA mixtures. The difference of carbon number distribution (especially the individual E/O isomers) could be used to reveal the NA source, i.e., petrogenic or biogenic contribution.

3.2 Distribution of NAs in Distillation Fractionation of Alaska North Slope Crude Oil The NA profiles of refined products are clearly distinguishable from those of crude oil. NAs in petroleum occur throughout the boiling ranges and have a decided tendency to exist in the higher boiling fractions and residua. Naphthenic acids in refined petroleum products originate naturally from the source crude oil and are unlikely formed during the refining process (API, 2012). In order to better understand the distribution of nitrogen-containing compounds in

Yang, C . G. Zhang, M. Serhan, G. Koiw, Z. Yang, B.P. Hollebone. P.G. Lambert and C.E. Brown. CharacterizaUon ofNaphlhenlc Acids In Crude Oils and Refined Petroleum Products. Proceed'ngs of the Forty·first AMOP Technical Seminar, Environment and Climate Change Canada , OHawa , ON, Canada, pp. 559·575, 2018. various petroleum products, the Alaska North Slope crude oil was divided into four fractions using the vacuum distillation technique, following the modified ASTM D 1160 method. Four distillation fractions were successively collected according to their boiling points, i.e., initial boiling point-l 74°C, l 74-287°C, 287-481°C, and >481°C, respectively. Fractions 1 and 2 contain the lightest hydrocarbons of :'.:: 11-C 1i and 11-C10 to 11-C16, respectively. Distillation fraction 3 corresponds to the carbon range of 11-C 11to11-C 34 and is roughly equivalent to medium fuels, totally making up 31.3% (w/w) of Alaska North Slope (ANS). The heaviest fraction 4 mostly contains compounds with a boiling point higher than that of 11-C34, accounting for 29.5% of the total weight of ANS crude. Our previous studies have revealed that smaller cyclic compounds of diamondoids and bicyclic sesquiterpanes were mostly found in fractions 2 and 3. It is apparent that these compounds were in low concentration in the lightest fraction 1 and were rarely found in the heaviest fraction 4 (Yang et al., 2016).To facilitate convenient comparison, the NAs in four distillation fractions are summarized in Figure 3. As seen in Figure 3, light fractions l and 2 only contain low MW NAs with smaller Z values. Most of the NAs were allocated into the heavier fraction 3, which accounted for about 90% of total NAs in the source oil. NAs in this fraction were enriched with a significantly higher concentration of 1,965 µgig compared with 419 µgig in the source crude oil. Only a small amount of NAs with high MW and larger Z values were detected in the heaviest fraction 4. Some small saturated carboxylic acids were also found in this fraction (Table 1 and Figure 3). These compounds could be generated during storage. NA concentration and profiles of refined products vary depending on the source of oil. In fact, NA profiles in terms of concentration and distribution do not simply agree with those observed from vacuum distillation. As noted in Table 1, intermediate fuel oil (IFO), Bunker and lubricating only contain relatively low concentration ofNAs, 533 µgig, 435 µgig and 81.2 µgig in these three oil samples, respectively. During the manufacture production of refined petroleum products such as diesel fuel, jet fuel, and lubricating oils, naphthenic acids in stock crude oil is purposely removed to improve the performance characteristics and storage properties of the finished products (API, 2012). Therefore, it is expected that high quality light petroleum products contain low concentrations ofNAs.

3.3 Profiles of NAs in Oil Sands Bitumen Naphthenic acids from production of oil sands bitumen have led to increasing environmental concern in recent years due to their toxicity. These polar compounds are among the principal toxicants in oil sands process-affected water and are resistant to biodegradation by the indigenous microorganisms in tailings ponds. NAs are believed to be acutely toxic to a broad range of aquatic environments (Clemente and Fedorak, 2005; Kannel and Gan, 2012). In the Athabasca oil sands deposit, NAs constitute approximately 2%, by weight, of the total bitumen (Headley and McMartin, 2004). It was reported that a large amount ofNAFC/NA was detected in oil sands process-affected water (Pereira et al., 2013). To gain an understanding of the potential transport and distribution of naphthenic acids, we investigated the NAs in oil sands, commercial bitumen and oils sands process-affected water. To obtain oil bitumen, Alberta oil sands was extracted by DCM with sonication at a ratio of 1: 10 (oil sands/DCM, w/v). The resulting bitumen was assumed as complete extracts. TSEM (total solvent extracted materials) from triplicate extraction was determined as 15.8% :!::: 0.4% by weight. Oil sands was also extracted by caustic water (60 - 70°C) at a ratio of 1/4 (oil sands/water, wlw)

Yang, C., G. Zhang, M. Serhan. G. Koivu. Z. Yang, B.P. Hollebone. P.G. Lambert. and CE. Brown, Characterization ofNaphlhenlc Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technical Seminar, Environment and Climate Change Canada . Ottawa. ON. Canada. PP-559-575. 2018. according to Clark caustic hot water extraction process. The caustic water contained 0.01 % NaOH (w/v) which is equivalent to 0.04% NaOH to oil sands (w/w) was used to improve the bitumen liberation from the sands surface (Zhang et al., 2016). The bitumen extracted with caustic solution in our lab had a similar NA profile to the commercial Cold Lake bitumen (Figure 4). Naphthenic acids are weak acids, and under alkaline conditions their solubilities tend to increase; therefore, these components are partially removed during caustic extraction. NAs in oil sands DCM extract span from C6 to C611 , much broader than the range of in caustic extraction product. Figure 4 compared the distribution of different molecular NAs in various oil sands bitumen. Bitumen extracted from raw oil sands by caustic water contains lower NAs, especially short chain NAs, compared with that directly extracted by DCM. C6-C:m NAs in oil sands DCM extract account for - 37% of a total NA content of7,419 µgig, and in caustic extract about 19% of 6, 107 µgig. As seen in Figure 4, NAs in the OSPW from steam assisted gravity drainage (SAGO) process have relatively lower MW, and u-class C6 to C24 NAs totally make up about 95% of total NAs. The u-NAs which are more polar and more corrosive tend to partition to the wastewater in the tailings ponds. Z-4 to Z-8 isomers make up over 50% of total NAs in this OSPW. Grewer et al. (2010) reported that a majority of the classically defined NAs in OSPW were polycyclic isomers with Z numbers between -4 and -8. Holowenko et al. (2002) have postulated that microbial metabolism of the carboxylated side chains and the ring structure ofNAs would lead to methane production. They observed that the Z-4 and Z-6 families (accounting for 53 % of the acids) in OSPW NAs, and Z = 0, -2 and -4 families (accounting for 81 % of the acids) in the commercial NAs were the most abundant acids.

3.4 Hcteroatom Class Profiles of Crude Oils and Petroleum Products

Petroleum and its derivatives are largely composed of homologous series, C 0H2n+:r: X, in which X denotes heteroatoms (N, S, 0) in each molecule (Mapolelo et al., 2011). Except for 0 2 species, the North American crude contains a higher number of multiply oxygenated compounds: 0 3, 0 4, 0 3S, 0 3S2, 0 4S, OsS and NO;i. , but their presence is only at less than 1% relative abundance (Hughey et al., 2002). To obtain a thorough heteroatom profile ofNAs in petroleum, responses of all exact masses from a spectrum were exported by Xcalibur (Thermo Fisher Scientific Inc.). Furthermore, the value of the ring and double-bond equivalent (ROBE) was derived for each calculated chemical formula. Probable empirical formulae of each mass were derived based on a 3 ppm mass tolerance (the difference between the theoretical and experimental mlz values). Elemental compositions of the formulae were restricted to the main elements of crude oil: carbon, hydrogen, oxygen, nitrogen and sulfur. Method blank and instrumental system blank (spectra of first 2 min and last 2 min of each analysis) were both subtracted from each oil sample. The probable analyte can be overestimated using the response of its mass because this response is contributed by all compounds producing this specific mass in whole analysis without consideration of retention time. In addition, this approach is unable to provide confirmative speciation of derived formulae. As seen in Figure 5, Sli,N 10 ? (y = 0, 1, or 2) species are generally the most predominant in studied crude oils, IFO 180 and bunker C. The high relative abundance of the N02 species suggests that they could be monocarboxylic carbazoles, benzocarbazoles or dibenzocarbazoles (Mapolelo et al., 2011). For Mississippi Canyon crude and Cold Lake Bitumen, 0 2 group is about 70% percent of SyN102 species. The 03 and 0 4 class (presumably dicarboxylic acids) were observed only at very low abundance. In addition, highly degraded crude oils usually contain low

Yang, C., G. Zhang, M Seman. G. Koivu. Z. Yang . B.P. Hollebone. P.G. Lambert, and C.E. Brown. Characterization of Naphlhenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technlcal Seminar, Environment and Climate Change Canada. Ottawa. ON. Canada, PP- 559·575, 2018. concentrations of nonnal alkanes, and low levels of parent PAHs and APAHs with lower alkylation.

4 Conclusions This study presents a comprehensive quantitative analysis of naphthenic acids in crude oils and refined products by LC-HRMS. In summary, we concluded that: 1) Naphthenic acids were detected in crude oils and heavy fuels in considerable abundance with the use of liquid chromatography-high resolution Orbitrap mass spectrometer. The overall distribution pattern and profiles ofNAs are, in general, different from oil to oil and from crude oils to refined products. 2) Naphthenic acids in conventional light crude oils are usually at low concentrations, w very high in heavy crudes and oil sands bitumen. 3) C6 to C24 isomers totally account for over 70% of total NAs in most of studied oils, and the NAs detected are generally dominated by Z = -2 - -6 NAs. 4) C6 to C24 NAs tally constitute about 50% ofNAs in oil sands bitumen, and C2s to C60 accounting for about half of total NAs. Z-0 to Z-12 series totally account for about 90% of NAs in bitumen, and Z-14 to Z-24 accounting for about 10% of total NAs. 5) Caustic extraction of oil sand bitumen transports small NAs into oil sands process-affected water. C6 to C24 NAs totally make up about 95% of total NAs detennined in an OSPW sample, and NAs in OSPW are dominant by Z-4 to Z-8 isomers. 6) Evaporation (up to 23.6%) increased total concentration ofNAs in dilbit but did not significantly affect the distribution of NAs. 7) The even to odd ratio for crude oil and refined products is all around 1.00 for Z-2 to Z-24 NA isomers. The E/O ratio could be significantly higher in environmental sediment samples. 8) NAs are rarely found in the lightest distillation fractions but likely tend to be concentrated in heavier petroleum fractions. 90% of NAs in Alaska North Slope crude oil were collected in the 287-481°C (equivalent to -n-C17 to 11-C34) during distillation fraction. However, intermediate fuel oil, bunker C and lubricating oils contain relatively low concentration of NAs as deleterious substance are removed during the manufactures of these oils in order to improve their performance characteristics and storage properties.

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Yang, C, G. Zhang. M . Serhan. G. Koiw, Z. Yang, B.P. Hollebone. P.G. Lambert. and C .E. Brown, Characterization of Naphlhenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty·first AMOP Technical Seminar. Environment and Climate Change Canada. Ottawa. ON, Canada, pp. 559·575, 2018. Jones, D., A.G. Scarlett, C.E. West, and S.J. Rowland, "Toxicity of Individual Naphthenic Acids to Vibrio fishe1y", Environmelllal Science and Technology, 45: 9776-9782, 2011.

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Yang, C., G. Zhang. M. Serhan, G. Kolvu, Z. Yang. 8 .P. Hollebone. P.G. Lambert, and CE. Brown, Characterization ofNaphthenic Acids In Crude Oils and Refined Petroleum Products, Proceedings of the Forty-first AMOP Technical Seminar. Environment and Climate Change Canada, Ottawa, ON. Canada, pp. 559-575, 2018. Table 1 Concentration of naphthenic acids determined in studied crude oils and refined products.

Sample code Oil samples NAs (µgig)" E/Ob Crmle oils FED Federated oil, Ari - 39, Alberta 139 1.05 ANS Alaska North Slope, Ari .. 31.0, Alaska 419 I.OJ MC Mississippi Canyon, Ari -= 27.5, GulfofMexico 3,057 1.01 OrB Orinoco Bitumen, Ari = 7.65, Venezuela 7,994 1.00 CLB Cold Lake Bitumen, Ari ""' 9.68, Esso Resources Canada 3,319 1.03 OS-Ext Alberta oil sands bitumen extracted by DCM 7,419 1.02 OS-ExtB Alberta oil sands bitumen extracted by caustic solution 6,107 1.03 AWB Acess Western Blend (AWB), Alberta 4,894 1.03 CLD-S Cold Lake dilbit (Summer), Alberta 3,534 1.05 CLD-S 6.5% Cold Lake dilbit (Summer), 6.5% weathered 3,388 1.04 CLD-S 13.0% Cold Lake dilbit (Summer), 13.0% weathered 3,589 1.03 CLD-S 19.5% Cold Lake dilbit (Summer), 19.5% weathered 3,246 1.07 CLD-W Cold Lake dilbit (winter), Alberta 2,807 1.04 CLD-W 7.9% Cold Lake dilbit (winter), 7.9% weathered 3,132 1.06 CLD-W 15.8% Cold Lake dilbit (winter), 15.8% weathered 3,317 1.05 CLD-W 23.6% Cold Lake dilbit (winter), 23.6% weathered 3,197 1.05 Petrole11111 prmiltcts Diesel No. 2 Diesel No. 2, Ottawa 170 1.09 IF0-180 IF0-180, Ottawa 533 1.02 BkC Bunker C, Alaska 435 1.02 Lube !Ow-30 I Ow-30 motor oil 81.2 ANS distillation Fl IBP-180°C, 20.6% (w/w) 37. 1 l.18 ANS distillation F2 180-287cc, 15.5% (w/w) 177 1.01 ANS distillation F3 287-481cc, 31.3% (wlw) 1,965 I.OJ ANS distillation F4 >481 QC, 29.5% (w/w) 132 1.01

•Concentration obtained from group integration by carbon numbers (µgig) from Cft to C(j!) and Z of0 ~-24 . b NAs concentration ratio of even carbon to odd carbon.

Yang, C., G. Zhang, M. Seman, G. Koivu, Z. Yang. B.P. Hol ~ebone , P.G. Lambert, and C.E. Brown. Characterization ofNaphthenic Acids in Crude Oils and Refined Petroleum Products. Proceedings of the Forty-first AMOP Technical Seminar, Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559-575, 2018. 571

10.0 50.0 Mississippi Canyon Mississippi Canyon 8.0 40.0

6.0 30.0 ~ !: 8 " 20.0 Ii 4.0 "15 ...c ...c :I ...:I 10.0 ~ 2.0 < 0.0 0.0 N 0 N v ~ 0 v ''''I Iii''"'" 0 g .. ~ ijh~. ,, "'"" 8 8 ! ';' .... ';' 8~N~CDaV~B~~~N~~ ~~s .--: ~. ... ,.:., ..:, ,.:, N ,.:., N ;:; N "',.:, ..J "',.:., uuOGO Dd 0 ~53u~ ~u .:.. .:.. Carbon number Z Vll lue 10.0 30.0 Cold Lake Bitumen Cold Lake Bitumen 25.0 8.0 20.0 _ 6.0 .!. ~ .. i 15.0 ~ 4.0 ..c ...c 11 10.0 :I :I 2.0 ...< ~ 5.0

I I 0.0 ' . 0.0 I I I • - -r-.., 0 ' N ' v • CD ' 0 v -§§""~=av~~M~~N~~-MJ~ v~~ N ...... ';' - :::I ..... ~ij~IJJ»!Mt\\\'1"...= ';' .... ~ 9 ~ "' OOG DD 0 ~33u~~~u N N ~ N ~ ,.:i ,.:i N N ,.:i N ,:; ,.:., Carbon number Zv.11lue

20.0 so.a DleselNo. 2 Diesel No. 2 16.0 40.0

_ 12.0 30.0 .!. l 8 B fi 8.0 ..c 20.0 ...c ...c: :I :I .Cl 10.0 < 4.0 ~

0.0 I I I I 0.0 rn~jJ • o,, ' .1 11 Ii I I I' 111 I · I I; I l I I I I l I I' I l 11 l I I~0 -.--N - . -~ .00 0 '

~ 6.0 i 15.0 fl ..Cl Iii 4.0 Ii 10.0 ...c .... :I c: :i ~ .A 2.0 < 5.0

0.0 0.0 ~lW .ij ...... ,.. " N 0 N 0 N ~s"'~ av~~a~~~~~ ~~~ hJ_J.... ~IA~ ~ ~N N .. N ... uOOO.. ~lll~00 AIMOuuu~"""·· ... ~u e C? ~ ~ ~ ,.:, ,.:, .:,"... ,.:, N N N N N ...i ...i C.llrbon number Zv1lue "' °"

Figure 1 Distribution of C 1Hy02 in terms of carbon number and Z values

Yang, C., G. Zhang, M. Serhan, G. Koivu, Z. Yang, B.P. Hollebone, P.G. Lambert, and C.E . Brown, Characterization of Naphthenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technical Seminar, Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559-575, 2018 572

120 l\llsslsslppl Cnnyon 10 ANS 9 JOO 8 7 BO 6 ~ ~ 60 a. 5 .; -= 4 .§ 40 ~ 3 2 20 1 0 0

~o,.:,.J..O-.cio:S::: ~ oN J.. 0-,do~~ zvaluc zvalue

Cold Lnkc Dllblt (Summer) Cold Lnkc Dll[)ll C'Vlntcr)

80 70 70 60 60 so -;a 50 4 0 ~4 0 -;;;; ~ 30 ~ 30 a. ... 20 20 .§ 10 10 o 0

140 Dlesel No. 2 .14 IF0-180

12.0 12

10.0 10 =s 80 8 =.; 6 .0 .§ 4 .0

2 ,0 2

0 0 0

~=.:...J.O..Co:;::: ~o.,:... .b.. °"cio~ ;::; ZV•lue zvalue

Figure 2 Distribution of NAs (C1 Hy02) in selected crude oils and petroleum products.

Yang, C., G. Zhang. M. Serhan, G. Koivu, Z . Yang, B.P. Hollebone. P.G. Lambert, and C.E. Brown. Characterization ofNaphlhenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty-first AMOP Techn.cal Seminar, Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559· 575, 2018. 573

9 ANS Fl 18 Ai~S F2

8 16

7 14

6 12

~ 5 10 llD ~ -=tJ 4 -= 8 a 3

2

1 0 -.

~ o N :, a, 0:i ~ ~ zva\ue

40 ANSF3 10 ANSF4 9 35 8 30 7

25 6 ~ ~:I. 20 :I. s -.; -.; s 4 8 15 u 3 10 l

5 1

0 0

I 1. .:....eo~~ ,.\.., ~ ~ 0 N-"" w• 0 N II\ 0 ' w• - ..:..0 N ::!'.: C\ N ~ z Va\ue ZValue

Figure3 Distribution of NAs (C1 H).0 2) in ANS distillation fractions.

Yang, C, G. Zhang, M. Seman, G. Koivu, Z. Yang , B.P. Hollebone. P.G. Lambert, and CE. Brown. Characterization of Naphthenic Acids In Crude Oils and Refined Petroleum Products. Proceedings of the Forty-first AMOP Technical Seminar, Environment and Climate Change Canada, Ottawa. ON , Canada , pp. 559·575 , 2018 . 574

10.0 10.0 Alberta 011 Sands Extract OS Extract (caustlcl

8.0 8.0

g 6.o ~ 6.0 .. fl ...,ii ..,Ii c c ~ 4.0 ~"' 4.0 .

2.0 2 .0

, , I ,, . 0.0 . ' .lllf 0.0 ~.1 1 , ,0 ; ,',• ,t,l ,1.\. 1 . .. . . lilll11J.u1111 oo.· .., · · ~ •• $gN~ma~~oa~~~~~-~~~liJHll•11µ,~,.,,,~ uuOOO~~~ ·l" 00 Ouuu~ ~u §§Eaoaaa~a~as~sa~B§ '. C.rbon numb•r carbon number 10.U zu.u Cold Lake Bitumen OSPW

8.0 16.0

g 6.0 l 12.0 !j u ..,Ii "c c ...,.. c 8.0 .il 4.0 :r < .a ct 4.0 2.0

0.0 .l1u .. ~..,l,l~':'-.'f~"i" 1 , I I , I I I I I I I I I I I I I I I I I I I 0.0 ... ,•• , ~~1 .•Jl '' ',, , I ; .. .111 ~ )J ).1111 1.1w ... ~ ". " •. ~~ N~~av~O~~~N~~~~~ g §gN~~a~~o~~~N~~-~~§ uOOO 00 0 0~~ ~ ~ uuOOO~·~ DD 0 O~~u~ ~u carbon number Carbon number

Figure 4 Distribution of C 1 Hy02 in oil sands extract (by DCM and caustic solution), commercial oil sands bitumen and oil sands processing water in terms of carbon number and Z values

Yang, C., G. Zhang, M. Serhan, G. Koiw, Z. Yang, B.P. Hollebone, P.G Lambert, and C.E. Brown. Characterization ofNaphthenic Acids in Crude Oils and Refined Petroleum Products, Proceedings of the Forty.first AMOP Technical Seminar. Environment and Climate Change Canada, Ottawa, ON, Canada, pp. 559-575, 2018. 575

100 - federated crude 100 - --Alaska-North-Slope 1 90 -+------< 90 +------··------·-- 80 +•------..---i 80 +------··-----··-- ~ 70 e- 70 +------•1-----.. -- ..a !iO - -- -- fl 60 ----- Ii c: "Cl so c: - ~ so +------•1-----··-- ;i § ..Cl 40 - - ..Cl 40 +------•1------,-- < - < 30 ------30 +--- 20 - - - 20 +------11----· ·- --- - 10 -1------10 j - 0 11.-- 0 ll-.-~ .,..-.,.--..-,,--,-~- ,..-..,..--ro.,.....,1 ...... , .. .. N~Vr.t\t,D 0 0 000... "'"' 00 00 00 00000 00 00 ..., N ,.., N ...... N zz ~~ zz "'"' ~~ "'"' "'"' ~~ 100 - Mrsstsstppr canyo_n_ -- - Cold Lake Bitumen- 90 lOO E BO -e 70 a - u 60 ~ ~ \------··- Ii "Cl so c: +•------··-----,..·•-- ~ so ;i § ..Cl 40 < 30 -- 20 +·-~.-~-~~-----·-~-;J-j-·.-= ~ ~ !·-..-- ·- -- - - 10 - - 0 I . N tt"l 'l:t LI'\ \C .... 00000 0 0 0 0 00 ,... N co.... N ..., N ..., N ~~ co,.., N VI VI 22 zz "'"' ~~ ~~ 100 ----- IF0-180------~- • 100 ---- Bunker c;

90 90 +------··-----··-- 80 80 +------•1 -----~-- e- 70 e- 70 +------·-----·· -- ..a !iO Ii ~ ro I "Cl 50 "Cl 50 ~ ----·------c: ;i ..Cl 40 < ~ : -I--- ·---·­ : +--. r--r----.--r-~~~T--.--r-tE t ~~c;~tS 00 co - ,...... -t N "'"' z z

Figure 5 Heteroatom class distribution for (CcHh0oS$Nn) in crude oils and refined products, based on ESI- analysis.

Yang, C., G. Zhang, M. Seman. G_Koivu . z_Yang , B.P. Hollebone, P_G, Lambert, and C.E. Brown, Characterization of Naphthenic Acids In Crude Oils and Refined Petro:eum Products, Proceedings of the Forty-first AMOP Technical Seminar, Environment and Climate Change Canada, Ottawa. ON. Canada , PP- 559-575, 2018.