Electrospray Ionization FT-ICR MS Research Articles

Petroleomics by design of experiments in ESI(±)FT-ICR MS analysis

The Fourier Transform Ion Cyclotron Resonance mass spectrometer (FT-ICR MS) is an efficient and widely used analytical instrument for characterizing complex organic mixtures at the molecular level. The Electrospray ionization (ESI) source is commonly used for identifying heteroatomic compounds (N, O, S) in crude oil. The high complexity of the sample provides a wealth of information, and therefore, processing and visualization programs are used to facilitate data interpretation. Several experimental configurations of parameters exist for the acquisition of ESI(+)FT-ICR MS and ESI(-)FT-ICR MS of crude oils. In this context, the design of experiments can help obtain optimal test conditions. The objective of this work was to identify the most significant experimental parameters among the 11 available (concentration, skimmer, time of flight (TOF), flow rate, ion accumulation time (IAT), accumulated scans (scans), dry temperature, capillary, dry gas, nebulizer, and collision voltage (CV)) for the acquisition of ESI(±)FT-ICR MS in Petroleomics using design of experiments by Plackett Burman and full design. Global desirability was used as a response parameter obtained from MS data (resolution, signal-to-noise ratio, signal-to-charge ratio signal with highest absolute intensity, total signals, low mass error, and high mass error). Additionally, responses from the mass spectra processing program were also used (the number of molecular formulas, molecular formulas of the majority class, average error, assignment percentage, amount of DBE in the plot of DBE versus carbon number (CN), and the relationship between the number of zero intensities and the number of DBE values in the plot of DBE versus CN). The study found that concentration and flow rate were the most significant experimental parameters for ESI(+), while for ESI(-), TOF and CV were the most significant experimental parameters. Lower concentration (0.1–0.5 mg/mL) and higher flowrate (5–6 µL/min) improved the desirability by ESI(+), higher values of CV (50 V) improved the desirability by ESI(-) for crude oil analysis.

Effect of salinity on molecular characterization of dissolved organic matter using ESI FT-ICR MS

Solid-phase extraction (SPE) coupled with negative-ion Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been widely used for molecular characterization of dissolved organic matter (DOM). However, little attention has paid to test whether the salinity of the sample and the presence of chloride ions in water samples affect the molecular composition of DOM extracted by SPE (SPE-DOM). In this study, one natural organic matter standard and several natural waters were selected to investigate how salinity affects the molecular composition of SPE-DOM and the selectivity of chloride ion adducts formation with respect to the molecular structure of SPE-DOM in negative ion ESI FT-ICR MS analysis. The results show that the molecular composition of SPE-DOM varied in a sample made by different salinity; and the variation pattern of DOM composition was different among different water samples under the treatment of consistent salinity gradients. The chloride ions can't be completely removed from cartridges in conventional SPE, thus leading organic compounds in SPE-DOM to form [M+Cl]‾ adducts when performing ESI FT-ICR MS analysis. In addition, the molecules with high H/C and low O/C ratios were likely to form [M+Cl]‾ ions. The relative abundance of [M+Cl]‾ ions could increase with the increase of salinity. These results are instructive to guide the pretreatment and molecular characterization of DOM in water samples with different salinity. Overall, we proposed a modification to the SPE to minimum reduce the formation of chloride ion adducts during the isolation of DOM.

Molecular characterization of humic-like substances (HULIS) in atmospheric particles (PM2.5) in offshore Eastern China Sea (OECS) using solid-phase extraction coupled with ESI FT-ICR MS

Humic-like substances (HULIS) are organic macromolecular compounds (water-soluble brown carbon) that have an important effect on climate change due to their strong light absorption. However, the molecular composition of HULIS in atmospheric particles in the offshore Eastern China Sea (OECS) has scarcely been investigated. In this study, solid-phase extraction (SPE) was performed to collect HULIS from water extracts. The molecular compositions of samples were characterized by negative-ion electrospray ionization (ESI) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A total of 1197–1828 molecular formulas of HULIS were identified in collected samples, and three of them with higher intensities near Shanghai city, Zhejiang province, and Fujian province were discussed in detail. The identified molecular formulas were classified into four major subgroups, including CHO, CHNO, CHOS, and CHNOS compounds. S-containing formulas (CHOS and CHNOS) represented the dominant components (21.0–76.7% relative abundance), followed by CHO (16.5–64.3%), while CHNO compounds constituted 6.1–18.1% of the identified formulas. High fractions of CHO formulas were found in the list of α-pinene ozonolysis yields and S-containing formulas with olefinic structures were abundant in atmospheric particles, suggesting enhanced SOA formation. The samples had a relative abundance-weighted average O/C of 0.25–0.67 and a double bond equivalent of 3.49–4.96. Most identified formulas (>89%) were assigned to aliphatic and olefinic species. The CHNO and S-containing formulas identified in the samples were primarily contributed by –ONO2 functional groups and organosulfates. Biogenic volatile organic compounds (α-pinene or monoterpene) were the dominant precursors of HULIS in the samples. Lignin-like species (41–46%) and protein/amino sugars (28–30%) were the major species among substance classes. The results provide an improved understanding of the molecular composition of HULIS in the Eastern China Sea.

Comprehensive composition and comparison of acidic nitrogen- and oxygen-containing compounds from pre- and post-salt Brazilian crude oil samples by ESI (-) FT-ICR MS

The discovery of the pre-salt oil field renewed and expanded the outlook of the Brazilian petroleum industry due to the large volume of oil and its composition. The chemical composition characterization of crude oils from different reservoirs is crucial for the petroleum industry. In this study, comprehensive profiles of polar acidic nitrogen- and oxygen-containing compounds were accessed by electrospray ionization (ESI) in negative mode coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for a set of five Brazilian crude oil samples from the pre-salt layer, and these were compared to the chemical composition of four crude oils from post-salt reservoirs. The ESI (-) FT-ICR MS data showed that the N-containing compounds present high relative abundance among the heteroatomic compounds identified for pre- and post-salt crude oils, which was more notable for the pre-salt crude oils. Comparing the heteroatomic profiles of the pre- and post-salt crude oils, the N2, NO, and O classes were seen to decrease in relative abundance in the post-salt crude oil, whereas the NO2 and O2 classes increased in relative abundance. The acyclic to cyclic acid (A/C) ratio of the O2 class was used as a parameter to classify the pre- and post-salt crude oils. The high content of acyclic O2-containing compounds (A/C ratio > 1.2) indicated that the pre-salt crude oils are more preserved from microbial alteration, leading to the formation of O2-containing compounds, while an A/C ratio < 0.2 for post-salt crude oils categorized them as more biodegraded. A modified A/C ratio that included aromatic O2 compounds, analyzed in a ternary diagram, was also used to classify the oils according to their families: pre- and post-salt crude oils. Considering the O2-containing compounds with 1, 3, and 5 DBE (double bond equivalents), it was possible to group these oils according to their reservoirs. In addition, alkylphenols with DBE = 4, 5, and 6 also demonstrated a tendency to identify the oils according to their pre- and post-salt reservoirs. The petroleomic approach shown here by comprehensive FT-ICR mass spectrometry analysis is a powerful tool for differentiating crude oils from pre-salt and post-salt reservoirs.

Pyrolysis Temperature Effect on Compositions of Neutral Nitrogen and Acidic Species in Shale Oil Using Negative-Ion ESI FT-ICR MS.

Negative-ion electrospray ionization (ESI) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to study the effect of the pyrolysis temperature (400, 430, 460, 490, and 520 °C) on acidic and neutral nitrogen species in Huadian shale oil. To more accurately analyze the influence, shale oils produced during the heat-up stage were abandoned. The results show that because of the influence of polymerization and cracking reactions, the increase in temperature increases the content of pyrrole, thiophene, furan, phenol, and aromatic ring cores and decreases the content of carboxylic acid, respectively. Among all the heteroatom compounds identified from negative-ion ESI FT-ICR MS, the relative abundance of N1O1, N1O2, N1O3, N2, N2O1, O1, O3, O1S1, and N1S1 species increases, whereas that of O2 and O4 species decreases as the pyrolysis temperature increases. The decrease in the O2 species can be attributed to carboxylic acid with a double-bond equivalence (DBE) value of 1, whereas the increase in the O2 species with DBE values of 7 and 9 can be attributed to the formation of furan, phenol, and aromatic ring by the polymerization reaction at higher pyrolysis temperatures. Although the effect of the reaction temperature on the molecular composition of acidic and neutral nitrogen species is complex, still characteristic rules are found in this study.

In-House Standard Method for Molecular Characterization of Dissolved Organic Matter by FT-ICR Mass Spectrometry.

Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been widely used for molecular characterization of dissolved organic matter (DOM). However, ESI FT-ICR MS generally has poor repeatability and reproducibility because of its inherent ionization mechanism and structural characteristics, which severely hindered its application in quantitative analysis of complex mixtures. In this article, we developed an in-house standard method for molecular characterization of DOM by ESI FT-ICR MS. Instead of obtaining reproducible results by determining the instrument parameters, we adopted an approach of object control on the mass spectrum to solve the problem of poor reproducibility. The mass peak shape, resolution, and relative intensity distribution of a natural organic matter standard were adjusted by optimizing the operating conditions to obtain a repeatable result. The quality control sample was run 26 times by the different operators in a 6-month-long period to evaluate the reproducibility. Results showed that the relative standard deviation (%) of repeatability and reproducibility are 1.02 and 2.35 for average H/C, respectively. The in-house standard method has been validated and successfully used for the characterization of more than 4000 DOM samples, which is transferable to other laboratories.

CYHPO oxidation followed by methylation for selective characterization of thiophenic and sulfidic compounds in petroleum via ESI FT-ICR MS

In the present paper, the molecular composition of sulfidic and thiophenic compounds in petroleum samples were selectively characterized by positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after cyclohexanone peroxide (CYHPO) oxidation followed by methylation. The sulfidic compounds in petroleum were mainly oxidized to sulfones by CYHPO while most of thiophenic compounds were not reacted. In the followed methylation process, the unreacted thiophenic compounds were converted to methylsulfonium. After using ammonium formate (HCOONH4) as a promoter, the obtained sulfidic sulfones (O2S1 class species) were selectively ionized in the form of N1O2S1 class species under positive-ion ESI FT-ICR MS. The thiophenic methylsulfonium salts in the oxidation-methylation products were also identified by positive-ion ESI FT-ICR MS as S1 class species. This analytical scheme was evaluated by a variety of model compounds and then applied successfully to diesel, VGO and crude oil samples to obtain the molecular composition of sulfidic and thiophenic compounds. In addition, the molecular type of biomarkers and other compounds in petroleum samples can be identified by this analytical scheme.

Molecular characterization of polar heteroatom species in oilsands bitumen-derived vacuum residue fractions by Fourier transform ion cyclotron resonance mass spectrometry

A Canadian in situ oilsands bitumen-derived vacuum residue (VR) was subjected to supercritical fluid extraction and fractionation (SFEF) into 13 extractable fractions and an unextractable end-cut and characterized by positive- and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results of negative-ion ESI FT-ICR MS showed that the N1 class species was the most abundant and the multifunctional group compounds, such as N1O1, N1O2, N1S1, N1S2, and N2 class species became abundant as the SFEF fraction became heavier. In positive-ion ESI mode, the relative abundance of N1 class species decreased gradually in the heavy SFEF fractions while that of multifunctional group compounds increased. The relative abundance of N4V1O1 increased dramatically in heavy fractions and the end-cut. The distributions of polar heteroatom species of VR derived from oilsands bitumen were similar with those of VR derived from the Venezuela Orinoco extra heavy oil.

Fractionation and molecular characterization of natural organic matter (NOM) by solid-phase extraction followed by FT-ICR MS and ion mobility MS

Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been widely used for the characterization of dissolved organic matter (DOM) extracted by solid-phase extraction (SPE) from various environmental waters. It is known that common SPE generally has a relatively low recovery and the non-polar and weakly polar components are less likely to be ionized due to ionization discrimination. However, the molecular selectivity during SPE is not clear so far. In this study, the Suwannee River natural organic matter (SRNOM) was fractionated by multi-step SPE with different solvents and the fractions were characterized by negative ESI FT-ICR MS and trapped ion mobility spectrometry-mass spectrometry (IMS-MS). The sequential solvent elution increased the extraction recovery of DOM in water by SPE and enabled the characterization of a weakly polar component, which cannot be detected in common SPE separation. The weakly polar component accounts for 5.7% in TOC for the SRNOM, which has complex but different molecular composition with methanol- and/or water-eluted fractions. Lipid-like compounds were enriched in this fraction. Compared with the polar molecules directly eluted by one-step SPE from the SRNOM, the weakly polar fractions exhibit larger molecular size. The results are helpful for understanding of the molecular composition of SRNOM, as well as other environmental waters. In addition, the study demonstrates that the combination of FT-ICR MS and IMS-MS has potential to characterize the chemical composition of a complex mixture, like DOM, to a new depth. Graphical abstract.

Profiling Murchison Soluble Organic Matter for New Organic Compounds with APPI- and ESI-FT-ICR MS.

The investigation of the abundant organic matter in primitive meteorite such as carbonaceous chondrites is of major interest in the field of origin of life. In this study, the soluble organic fraction of the Murchison meteorite was analyzed by atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), in both detection modes. Such an approach ensured that we obtained an extensive description of the organic matter of the CM2 meteorite. Indeed, while in total close to 16,000 unique features were assigned, only 4% are common to all analyses, illustrating the complementarity of both the detection modes and the ionization sources. ESI FT-ICR MS analysis, in negative-ion mode, ensured to observe specifically CHOS and CHNOS species, whereas the positive-ion mode is more dedicated to the detection of CHNO and CHN species. Moreover, new organomagnesium components were observed in (+) ESI. Eventually, (+) APPI FT-ICR MS analysis was a preferred method for the detection of less polar or nonpolar species such as polycyclic aromatic hydrocarbons but also heteroatom aromatic species composing the organic matter of Murchison.

Molecular characterization of aldehydes and ketones in particle phase of mainstream and sidestream cigarette smoke.

Aldehydes and ketones (AKs) in cigarette smoke are risk to humans and environment. Due to the complexity of itself and the interference of the smoke tar matrix, the aldehydes and ketones in particle phase (AKPs) of mainstream smoke (MSS) and sidestream smoke (SSS) have not been well investigated. In this study, the AKPs of MSS and SSS were derivatized into polar products by reaction with Girard T reagent. The derivatives were isolated rapidly by column chromatography and analysed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Fifteen species of aldehydes and ketones were detected by positive ion electrospray ionization (ESI) FT-ICR MS: O1–6, N1O1–4, N2O1–3 and N3O2–3. The total number of AKPs obtained by ESI FT-ICR MS in MSS and SSS is about 1100 and 970, respectively. After hydrolysis, the original AKPs were obtained and 63 carbonyls were identified and quantified by gas chromatography–mass spectrometry (GCMS). The nitrogen-containing and high-oxygen AKPs were further characterized by Orbitrap mass spectrometry. Structures of compounds with high relative abundance in the mass spectrum were speculated (e.g. a series of degradants of cembrenediol) by comparison with the results of GCMS.

Geochemical characteristics and significance of heteroatom compounds in lacustrine oils of the Dongpu Depression (Bohai Bay Basin, China) by negative-ion Fourier transform ion cyclotron resonance mass spectrometry

Abstract Saline and freshwater lacustrine oils from the Dongpu Depression (Bohai Bay Basin) were characterized by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). ESI-FT-ICR MS detected a large range of nitrogen and oxygen compounds in the oils, mostly comprising N1, O1, O2 and N1O1 species. The low mature oils are dominated by O1 species with double bond equivalent of 4 (DBE = 4; mainly alkylphenols), O2 species with DBE = 5–6 (i.e., hopanoid, secohopanoic and steroid acids) and DBE = 1 (i.e., fatty acids), indicating a genetic relationship between oxygen compounds and their precursors. The nitrogen and oxygen compounds were significantly influenced by maturity, with the lower maturity oils analyzed enriched in O2 species, particularly fatty acids and 4–5 ring naphthenes with biologically sourced hydrocarbon skeletons: ratios of O2/N1 > 0.7; C20–30/C15–45-DBE1-O2 > 0.4; and DBE5–6/DBE12–22-O2 > 6.0 may be useful indicators of low maturity. With increasing maturity, the condensation degree of the compounds increased and the carbon number decreased. The relative abundances of N1 and O1 species with the following specific DBE carbon number ranges were particularly sensitive to maturity: DBE9–12/DBE15–18-N1, C20–28/C29–40-DBE12-N1, C20–30/C31–50-DBE15-N1, DBE9–12/DBE4–20-O1 and C20–30/C31–50-DBE8-O1. In some instances the FT-ICR MS proxies provided a more reliable indication of high maturity levels than traditional sterane based maturity parameters. However, several of these species were also responsive to other influences, namely C20–28/C29–40-DBE12-N1 and C20–30/C31–50-DBE15-N1 ratios reflected an organofacies control and DBE9–12/DBE4–20-O1 and C20–30/C31–50-DBE8-O1 ratios changed with thermochemical sulfate reduction (TSR)– confirmed by δ34S variances of OSCs. In light of the multiple controls on the nitrogen and oxygen compounds, DBE9–12/DBE15–18-N1 ratio seems unaffected by organofacies or TSR and was considered the most reliable maturity proxy displaying a similar or better maturity relationship than Ts/(Ts + Tm). Aside from secondary alteration effects, the freshwater samples showed several compositional differences to the saline samples, albeit from a limited data set, including generally higher O2 and N1 (particularly low MW) product abundances, lower abundances and quite different distribution of O1 products. These distinctions suggest ESI FT-ICR MS analysis has potential for distinguishing these sample types.

Use of ESI FT–ICR MS to investigate molecular transformation in simulated aerobic biodegradation of a sulfur-rich crude oil

Achieving an understanding of the biodegradation of organic sulfur compound(s) (OSC) in crude oils has been hampered by limitations in separation methods and analytical techniques. In this study, a simulated aerobic biodegradation experiment was performed on a sulfur-rich crude oil, from which a series of biodegraded oils from slight to moderate degrees of biodegradation were obtained. Molecular transformations in these biodegraded oils were investigated by gas chromatography–mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT–ICR MS) under both positive- and negative-ion electrospray ionization (ESI) modes. The variations in the distributions of saturated hydrocarbons, OSCs, and acidic components during aerobic biodegradation were studied. A gradual decrease of OSCs with alkyl chains during biodegradation, especially in those with few sulfur-containing or naphthenic/aromatic rings, was observed. In addition, sulfur-containing phenols with alkyl chains also exhibited a trend of gradual decrease similar to alkyl phenols, with fewer ring numbers being more susceptible to biodegradation. The biodegradation pathways for OSCs and sulfur-containing acids, as well as certain other heteroatomic compounds, are discussed. Terminal oxidation, rather than sulfur-specific degradation, is the more likely biodegradation pathway of these OSCs, as in the case of n-alkanes in this study. Sulfur-containing carboxylic acids may be the biodegradation products of these OSCs.

Origin of polar organic sulfur compounds in immature crude oils revealed by ESI FT-ICR MS

Organic sulfur compounds (OSCs) are abundant in immature crude oils, including “polar” OSCs that are defined here as compounds containing one or more heteroatom(s) in addition to sulfur atoms having sufficient polarity to be analyzable by electrospray ionization (ESI) without derivatization. An understanding of the origins of polar OSCs in crude oils has been hampered by limitations in their analytical characterization. In this paper, we employed a high field (9.4 T) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with ESI to study the sulfur-rich immature crude oils from the Jianghan Basin in China. The results show that the polar OSCs usually have non-sulfur counterparts, i.e., heteroatom-containing compounds without sulfur, with similar carbon number ranges, but slightly lower DBE (double bond equivalence) distributions. The similar or even identical carbon number distributions of the polar OSCs and their non-sulfur counterparts indicate their inheritance from the same precursors. The sulfur rings in polar OSCs are formed by intramolecular sulfurization that leads to the increases in DBEs compared to their non-sulfur counterparts. The results also indicate that the number of sulfur rings that can be formed in polar OSCs is largely controlled by the number of available reactive functional groups in their precursors. This paper extends our knowledge of intramolecular sulfurization during early diagenesis, especially for polar heteroatom-containing compounds.

Transformation of nitrogen-containing compounds in atmospheric residue by hydrotreating

Atmospheric residue from Saudi Arabia light crude oil was subjected to the hydrotreating process in a continuous fixed-bed reactor with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) catalysts. The detailed molecular composition of the polar heteroatom species in the feedstock and products was determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with other analytical methods. The ESI FT-ICR MS analysis indicates that the N1 class species have the highest relative abundance. In the hydrotreating process, small neutral N1 class species with high aromaticity and short side chains showed the highest relative abundance and were defined as easily removable compounds. High aromaticity and small molecule basic N1 compounds exhibited higher catalytic activity towards hydrogenation. The N1S1 class species were converted to the N1 class species, or even hydrocarbons, by the preferential removal of the sulfur atoms. Most of the N1O1 class species were difficult to remove, because of their stable chemical structure.

Molecular Insights into the Transformation of Dissolved Organic Matter in Landfill Leachate Concentrate during Biodegradation and Coagulation Processes Using ESI FT-ICR MS.

Landfill leachate concentrate is a type of refractory organic wastewater with high environmental risk. Identification of refractory components and insights into the molecular transformations of the organics are essential for the development of efficient treatment process. In this report, molecular compositions of dissolved organic matter (DOM) in leachate concentrate, as well as changes after anaerobic/aerobic biodegradation and coagulation with salts, were characterized using electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). DOM in leachate concentrate were more saturated and less oxidized with more nitrogen and sulfur-containing substances (accounting for 50.0%), comparing with natural organic matter in Suwannee River. Selectivity for different classes of organics during biodegradation and coagulation processes was observed. Substances with low oxidation degree (O/C < 0.3) were more reactive during biodegradation process, leading to the formation of highly oxidized molecules (O/C > 0.5). Unsaturated (H/C < 1.0) and oxidized (O/C > 0.4) substances containing carboxyl groups were preferentially removed after coagulation with Al or Fe sulfate. The complementary functions of biodegradation and coagulation in the treatment of DOM in leachate concentrate were verified at the molecular level. Lignin-derived compounds and sulfur-containing substances in leachate concentrate were resistant to biodegradation and coagulation treatments. To treat leachate concentrate more effectively, processes aimed at removal of such DOM should be developed.

Petroleum heteroatom compounds in various commercial delayed coking liquids: characterized by FT-ICR MS and GC techniques

Delayed coking is an important petroleum resid conversion process. The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids. Eight commercial delayed coking liquids were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatographic techniques. High relatively abundant heteroatom compounds in the coking liquids were 1–4 aromatic-ring pyridinic nitrogen compounds, carbazoles, benzocarbazoles, phenols, mercaptans, benzothiophenes, dibenzothiophenes, and naphthobenzothiophenes. Coking liquids derived from various feeds had similar compound class types, molecular weight distribution ranges, and double bond equivalents (DBE). However, the concentration of individual compounds and the distribution of DBE versus carbon number of heteroatom compounds varied. A comparison of heteroatom compounds in coker feeds and products revealed the various reaction mechanism of heteroatom compounds occurred during the coking process. The results suggested that molecular-level process models can be developed for optimization of unit operation to obtain desirable products that meet the environmental specifications and quality requirements.

Quantitative Molecular Characterization of Petroleum Asphaltenes Derived Ruthenium Ion Catalyzed Oxidation Product by ESI FT-ICR MS

Molecular structure of heavy petroleum could be investigated by the composition of its ruthenium ion catalyzed oxidation (RICO) products. However, the interpretation of the results was not comprehensive due to the limited compositional information obtained solely by gas chromatography (GC) analysis. In this study, a semiquantitative method based on electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was established and applied for the molecular characterization of RICO products. Thousands of polar compounds were detected by negative-ion ESI FT-ICR MS in the RICO products of the Canadian oil sands bitumen derived asphaltenes. Besides alkyl carboxylic acids, naphthenic acids with one to five naphtha rings, nitrogen- and sulfur-containing carboxylic acids, and acidic compounds with multioxygen atoms were observed. The upper carbon number limit of alkyl moieties connected to the aromatic cores of the asphaltenes was found up to 60, which is much higher than th...

Resolution and Identification of Petroleum Sulfonate by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

In this study, a petroleum sulfonate (PS) and its sulfonating raw oil were directly detected without pre-separation by using negative ion electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), in order to resolve and identify polar heteroatomic compounds in complex PS as well as to study the changes of various compounds from raw oil to PS before and after sulfonation. There were roughly 8500 and 6100 peaks positively resolved by mass spectrometry in PS and raw oil, respectively. Thirteen heteroatom classes in raw oil were identified as follows: N1, N1O1, N1O2, N1O3, N1O4, N1O5, O1, O2, O3, O3S1, O4, O5, and O5S1. As for those in PS, there are 19 classes, including N1, N1O1, N1O1S1, N1O2, N1O2S1, N1O3, N1O3S1, N1O4, N1S1, O1, O1S1, O2, O2S1, O3, O3S1, O4, O4S1, O5, and O5S1. Dominated O3S1, O2, O3, O4, N1O2, and O4S1 classes were classified and discussed in terms of double-bond equivalent (DBE) and carbon numbers. Significant O3S1 class species were centered at a DBE value of 4–10 with a carbon number of 23–34, corresponding to various alkyl aryl sulfonates, such as alkyl benzene and alkyl indanesulfonate. In summary, this paper introduced ESI FT ICR-MS to comprehensively characterize PS at the molecular level.

Detailed Characterization of Petroleum Sulfonates by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Petroleum sulfonates obtained from heavy vacuum gas oil (HVGO) were characterized by negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry [(−) ESI FT-ICR MS] to better understand the chemical nature of their surface-active components. Electrospray ionization (ESI) analysis showed that sulfonates contain mainly O3S, O3S2, O4S, and NO3S classes, which means that the sulfonation reaction does not occur selectively for aromatic hydrocarbon (HC) class compounds because it also reacts with N, S, and O heteroatom classes. Because sulfonates were separated by solubility into lipophilic and hydrophilic categories, it was confirmed that the same classes compose hydrophilic and lipophilic sulfonates. Moreover, this procedure revealed that lipophilic sulfonate extracts contain organic acids (O2 class) that are related to the total acid number of the starting HVGO. However, selective isolation of the surface-active species using the “wet-silica” procedure allowed for detection t...