In situ combustion (ISC) process has drawn more and more attention in the development of heavy oil reservoirs as a result of its high recovery efficiency. Although numerous studies have been reported that oil properties exhibit significant changes during the combustion process, the reaction mechanisms and evolution of oil components are still not well understood. In this work, the compounds of produced oils collected from a three-dimensional simulated production model (container) at different duration times after combustion being initiated and the original oil were characterized at the molecular level using gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both aromatic and acidic components were analyzed. The aromatic components showed relatively more stable characteristics than those of acidic components, and no obvious changes in aromatic compound distributions were observed by the positive ion atmospheric pressure photoionization (APPI) FT-ICR MS analysis. Small aliphatic acids were detected in the ISC oils, which were responsible for the high total acid numbers (TANs). The acidic Ox (x = 1–3) compounds, which have major contributions to the increase in TAN, were generated in greater abundances compared to that of the original crude oil. The carbon number distributions of the O1 and O2 classes in the produced oils significantly shifted to a lower carbon number region, with the dominant distribution from 15–40 at the initial state to 10–30 at the longest duration time. The double bond equivalent (DBE) values decreased during the combustion process. The generated acidic O1 components with DBE values less than 4 were also found in negative ion electrospray ionization (ESI) analysis, indicating the oxidation of hydrocarbons to alcohols.

Sulfur compounds in deep hydrodesulfurization (HDS)-derived diesels were effectively separated into thiophenic and sulfidic fractions using the methylation/demethylation method and characterized by gas chromatography–mass spectrometry (GC–MS) and GC–sulfur chemiluminescence detector (SCD). Sulfidic fractions account for over 15 wt % of total residual sulfur, in which a series of refractory cyclic sulfidic compounds, 1,1-dimethylhexahydrodibenzothiophenes (1,1-DMH6DBTs) and 1,9b-dimethylhexahydrodibenzothiophenes (1,9b-DMH6DBTs), were found in the diesels, and larger molecular weight homologues were identified. Some homologue series of C1–C4 alkyl-substituted thiaadamantanes were detected in the HDS diesel. These cyclic sulfidic components are refractory to deep HDS, which require more prudent catalysis and reaction systems to achieve ultralow-sulfur diesel (ULSD) production.

•A SPE based separation method was proposed for wastewater DOM fractionation.•MAX and MCX SPE cartridges containing reversed phase retention and ion-exchange adsorbents were used.•The separation provides HOA, HON, HOB, and HIS fractions.•Hydrophobic fraction could be analyzed directly by ESI MS.•Molecular compositions of DOM in three extracts were characterized by ESI FT-ICR MS.Although the progress of high resolution mass spectrometry in the past decade has enabled the molecular characterization of dissolved organic matter (DOM) in water as a whole, fractionation of DOM is necessary for a comprehensive characterization due to its super-complex nature. Here we proposed a method for the fractionation of DOM in a wastewater based on solubility and acidic-basic properties. Solid phase extraction (SPE) cartridges with reversed phase retention and ion-exchange adsorption capacities, namely MAX and MCX, were used in succession to fractionate a petroleum refinery wastewater into four fractions: hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophobic base (HOB), and hydrophilic substance (HIS) fractions. According to the total organic carbon (TOC) analysis, 72.6% (in term of TOC) of DOM was extracted in hydrophobic fractions, in which HON was the most abundant. Hydrophobic extracts were characterized by negative and positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. Compounds with multiple oxygen atoms were predominant in the HOA, which were responded strongly in the negative ESI MS. Nitrogen containing compounds were the major detected species by positive ion ESI in all hydrophobic fractions. The molecular composition of the DOM were discussed based on the FT-ICR MS results. The fractionation provided salt free samples which enables the direct analysis of the fractions by ESI and a deep insight into the molecular composition of DOM in the wastewater. The method is potential for routine evaluation of DOM in industry wastewaters, as well as environmental water samples.

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.

Electrospray ionization (ESI) coupled with Fourier ion cyclotron resonance mass spectrometry (FTICR MS) has been successfully used for molecular characterization of petroleum. However, ESI can not ionize nonpolar components which generally are dominant in the petroleum fraction. Here, we introduce a novel approach for aromatic compounds molecular characterization. Aromatics in petroleum fractions were ionized to [M + H]+ by positive-ion ESI with HCOONH4 as an ionization promoter, and when ESI is combined with high resolution FTICR MS, aromatic hydrocarbons and heteroatoms in petroleum fractions can be simultaneously analyzed. The method is easily available and has potential for the characterization of aromatic compounds in any other matrix.

Thiols widely occur in sediments and fossil fuels. However, the molecular composition of these compounds is unclear due to the lack of appropriate analytical methods. In this work, a characterization method for thiols in fossil fuels was developed on the basis of Michael addition reaction derivatization followed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Model thiol compound studies showed that thiols were selectively reacted with phenylvinylsulfone and transformed to sulfones with greater than 98% conversions. This method was applied to a coker naphtha, light and heavy gas oils, and crude oils from various geological sources. The results showed that long alkyl chain thiols are readily present in petroleum, which have up to 30 carbon atoms. Large DBE dispersity of thiols indicates that naphthenic and aromatic thiols are also present in the petroleum. This method is capable of detecting thiol compounds in the part per million range by weight. This method allows characterization of thiols in a complex hydrocarbon matrix, which is complementary to the comprehensive analysis of sulfur compounds in fossil fuels.

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 the results derived from GC analysis. Normal and isomer alkyl carboxylic acids, as well as naphthenic acids, were quantitatively analyzed separately. The quantitative results of alkyl carboxylic acids from ESI FT-ICR MS agreed well with the GC results. The FT-ICR MS results indicate that additional compositional information could be obtained from RICO analysis. In addition, the method is instructive for the development of quantitative analysis technology for petroleum molecular characterization based on ESI FT-ICR MS.

The compositions of crude oils can vary significantly during thermal maturation through cracking and aromatization. In this study, an immature high sulfur crude oil was pyrolyzed in a closed gold-tube system with heating rates of 20 °C/h and 2 °C/h, respectively, to simulate the thermal maturation process of crude oil. The molecular compositions of heteroatom-containing compounds in crude oil were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) while the impact of thermal maturation on migration and maturity geochemical parameters were investigated by gas chromatography–mass spectrometry (GC-MS). Based on the analysis of pyrolysis products, the compositional variations of heteroatom-containing aromatic compounds and the validity of the aromatic geochemical parameters during thermal maturation were investigated. When the equivalent vitrinite reflectance value (Easy %Ro) was greater than ca. 0.85, alkyl chain cracking was the major reaction and led to the producing of a large amount of ca. 1.18) due to further secondary cracking. Polycyclic aromatic compounds (PAHs) gradually became the dominant compounds in pyrolysis products; the carbon number of alkyl chains attached to aromatic core decreased while the aromaticity increased. Simultaneously, polar heteroatom-containing species became more dealkylated and aromatic with the increasing of maturity. The valid maturity range of geochemical parameters relevant to oil migration and maturity based on heteroatom-containing aromatic compounds were also discussed.

Negative- and positive-ion direct analysis in real time (DART) ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was applied to characterize crude oil and its fractions. Crude oil samples dissolved in toluene were directly infused into a spray needle, which produced a continuous and long-time stable ion current for FT-ICR MS analysis to obtain mass spectra with a broad dynamic range and high signal-to-noise ratio. A comparison between negative-ion electrospray ionization [ESI(−)] and negative-ion DART for crude oil analysis was presented. The DART(−) ionized almost all of the compound classes found in ESI(−), while it exhibited high selectivity on naphthenic acids, which enabled the characterization of naphthenic acids in petroleum with a low total acid number (TAN). The method is suitable for the analysis of naphthenic acids in petroleum distillation cuts, even with a very high boiling point. Sulfides in petroleum were likely oxidized to sulfoxides and exhibited high selectivity in positive-ion DART, indicating that it can potentially be used for the molecular characterization of sulfides in petroleum.

N-Methyl-2-pyrrolidinone (NMP) is a capable solvent which could extract more substance from coals than any other solvents. However, the molecular composition of the extract was still unclear. In this study, a lignite was subjected to Soxhlet extraction using pyridine followed by NMP. The NMP extract and its hydrolyzed product were characterized by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results showed that the NMP extract and its hydrolyzed product had very high nitrogen contents and NxOy class species with multiple nitrogen and oxygen atoms dominant in the detected species. Relative abundance of 15N isotope and the molecular composition of extracts obtained from different extraction conditions indicated that the NMP involved into the extracts. Both self-polymerization of NMP and chemical reactions between NMP and coals occurred in the thermal extraction.

Detailed characterization of petroleum derived sulfur compounds has been challenging, due to the complex composition of the hydrocarbon matrix. A novel method was developed for selective separation of thiophenic and sulfidic compounds from petroleum. Sulfur compounds were methylated to sulfonium salts by AgBF4 and CH3I, then the polar salts were separated by precipitation from petroleum matrix. The thiophenic and sulfidic sulfonium salts were sequentially demethylated with 7-azaindole and 4-dimethylaminopyridine, obtaining original thiophenic and sulfidic compounds, respectively. The method was validated by model compounds, and applied to a diesel and a vacuum distillation petroleum fraction. Sulfur fractions were characterized by gas chromatography (GC) coupled with a sulfur chemiluminescence detector (SCD) and quadrupole mass spectrometry (MS), and high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The technique was effective to selectively obtain high-purity thiophenic and sulfidic compounds and showed rare discrimination among sulfur compounds with ranging molecular weights and degrees of unsaturation. The method would facilitate multifaceted detailed characterization of sulfur compounds in an organic complex matrix.

•Multi-walled CNTs were investigated as solid trapping material for SFE extraction.•This SFE-CNTs method was efficient for quantitative enrichment of trace level PAHs.•16 PAHs and 15 typical PAH derivatives in soil samples were extracted and analyzed.A supercritical fluid extraction (SFE) method with an online solid collection trap has been developed for the quantitative analysis of 16 polycyclic aromatic hydrocarbons (PAHs) and 15 typical PAH derivatives in solid matrix. Compared with liquid trapping and C18 solid-phase trapping, multi-walled carbon nanotubes (CNTs) were proved to be the most efficient trapping sorbent for the collection of PAHs and their nitro-, oxy- and alkyl-derivatives. The proposed extraction–collection procedure was systematically optimized in terms of pressure, temperature, extraction time, trapping materials, supercritical fluid flow rate, co-solvent type, and co-solvent percentage, taking into account the interaction between these variables. The whole extraction process could be completed in 15 min followed by GC–MS analysis. Quantitative recoveries of PAHs and their derivatives from spiked soil samples (50 ng g−1) were obtained in the range of 62.9–111.8% with the precisions (RSD, intra-day) ranged from 1.9% to 13.7%. The developed SFE method with online CNTs trapping followed by GC–MS analysis has been demonstrated to be an efficient way for quantitative analysis of trace-level PAHs and their nitro-, oxy-, and alkyl-derivatives in soil samples.

A set of wastewaters sampled in a stream-by-stream flow of the process in a refinery wastewater treatment plant were characterized to investigate the molecular composition and transformation of dissolved organic matter (DOM). The samples were separated into organic and aqueous phase DOMs by solvent extraction and solid phase extraction (SPE). Volatile and semivolatile compounds in the organic phase were characterized by gas chromatography–mass spectrometry (GC-MS); DOMs in the organic and aqueous phases were characterized by negative ion electrospray (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The aqueous phase DOMs exhibited a more complex molecular composition than other complex mixtures investigated by far, in which there were totally 76 compound class species identified in a single mass spectrum. Refinery wastewater DOMs have lower values of double bond equivalent (DBE) and O/C ratio than those of natural organic matter (NOM) in fresh and marine waters. The organic phase DOM occupied the major TOC value, but was liable to be degraded in the biological process. Some humic-like substances presented in the aqueous DOM were found resistant to the treatment processes by the ESI FT-ICR MS based semiquantitative results.

Dissolved organic matter (DOM) in oil refinery process water was fractionated by XAD-8 resin techniques into four subfractions: hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON), and hydrophilic substance (HIS) fractions. Negative and positive electrospray ion (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the composition of DOM and its subfractions. Compounds with multi-oxygen atoms were found to be predominant in DOM by either negative or positive ESI analysis, which are similar in composition to most other treated water samples. The DOM in the HOA fraction had a similar molecular composition to that of raw process water by negative ESI analysis. The DOM in the HOB fraction had a low molecular weight (MW) when analyzed by positive ESI, and basic nitrogen compounds, such as N1 class species, were found to be predominant. The DOM in the HON fraction was predominantly O2 class species. The DOM in the HIS fraction had a relatively wide MW distribution. All of the compounds of DOM in the HIS fraction exhibited low double bond equivalents (DBE) and low carbon numbers. The results showed that the use of the XAD-8 resin fractionation technique is valuable for characterizing trace quantities of DOM components in process water because their spectral peaks would otherwise be obscured by other abundant peaks. The origin and determination of chlorine-containing compounds, which are abundant in the negative ESI mass spectra of HOB, were discussed.

Sulfur compounds in two representative deep crude oils (Ha9, 6598–6710 m; ZS1C, 6861–6944 m) with distinct levels of maturity from Tarim Basin, China, were analyzed by positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The thiophenic and sulfidic compounds were selectively separated from the crude oils with high purity and recovery by the methylation/demethylation approach and further characterized in detail by gas chromatography (GC) coupled with a sulfur chemiluminescence detector (SCD) and GC–mass spectrometry (MS). The two crude oils have a large difference in sulfur compound composition, which are both unique compared to common crude oils. A homologue series of 1,1-dimethylhexahydrodibenzothiophenes, which has been found as highly resistant organic sulfur compounds in diesel hydrodesulfurization, was detected in Ha9 crude oil. This is the first time that these biomarker-like compounds have been identified in crude oil. Thiadiamondoids (1–3 cages) with more structural isomers than reported oils as well as various acyclic sulfides, which probably derived from alkyl sulfides, were identified in the sulfidic fraction of the ZS1C crude oil, which indicates that the crude oil has an unusual geological history. The selective separation technique would offer broad prospects for geochemical research on sulfur compounds in crude oils, including their compound-specific 34S and 13C analyses.

To reduce water usage and wastewater treatment in coal gasification processing, the use of non-aqueous quenching agents was proposed. The purpose of this study is to assess the potential of using coal tar as a quenching agent for the Luger coal gasification. A low-temperature gasification-derived coal tar and an ethylene tar obtained from the petroleum naphtha cracking process in ethylene production were subjected to thermal aging tests to determine the effect of thermal severity on their viscosity and chemical composition. The viscosities of coal tar and ethylene tar as a function of the aging time were similar and relatively constant at 200 °C. At 250 °C, the coal tar was more unstable and had a shorter viscosity increase onset time than the ethylene tar. The tar samples before and after thermal aging tests were subjected to gas chromatography–mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to determine the molecular composition. The results indicated that olefins, especially aromatic olefins in the coal tar, were unstable, which likely caused polymerization of coal tar species during thermal aging and resulted in a short viscosity increase onset time. By adding a polymerization inhibitor, the viscosity increase onset time of coal tar was prolonged. The coal tar is potential for use as a quenching agent for coal gasification.

•Carbon dioxide-based supercritical fluid extraction (CO2 SFE) was used to extract petroleum.•Compositional recovery and selectivity by different extraction methods were studied by SIMDIS, GC–MS and FT-ICR MS.•Most of CO2 SFE non-extractable components are not suitable for GC analysis.•CO2 SFE can be an alternative to Soxhlet solvent extraction for petroleum compositional analysis by GC–MS.Carbon dioxide-based supercritical fluid extraction (CO2 SFE) has been an excellent alternative to solvent extraction in many industries. In this study, a heavy crude oil was adsorbed to kieselguhr and performed for comparison of different extraction processes. The oil extract by dichloromethane Soxhlet extraction was used as a benchmark. Another batch of the sample was subjected to sequential short-time and longer-time CO2 SFE, and subsequent dichloromethane Soxhlet extraction, yielding three distinct extracts. All of these four extracts were then fractionated by a standard saturates/aromatics/resin/asphaltene (SARA) method. Each SARA fraction was then analyzed by high temperature gas chromatography simulated distillation (SIMDIS), gas chromatography–mass spectrometry (GC–MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It was found that CO2 SFE selectively extracts relatively low molecular weight compounds with low degrees of molecular condensation. The remaining un-extracted components are mainly in polar resin and asphaltene fractions, containing the chemical species with large carbon numbers and high degrees of molecular condensation. Most of these components are in low volatility with boiling points higher than 500 °C, beyond the upper temperature limit of common GC columns. CO2 SFE can serve as an environmental-friendly alternative to Soxhlet solvent extraction if the goal of the analysis is to determine petroleum biomarker or compositional analysis by GC–MS. In addition, CO2 SFE for extracts only volatile compounds of small molecular weight has an advantage of leaving most non-volatile components that would be detrimental to the GC systems.

Aromatic fractions derived from aerosol samples were characterized by gas chromatography and mass spectrometry (GC-MS), high temperature simulated distillation (SIMDIS), and positive-ion atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. It was found that about 27 wt % compounds in aromatic fractions could not be eluted from a GC column and some large molecule PAHs were neglected in GC-MS analysis. APPI FT-ICR MS was proven to be a powerful approach for characterizing the molecular composition of aromatics, especially for the large molecular species. An aromatic sample from Beijing urban aerosol was successfully characterized by APPI FT-ICR MS. Results showed that most abundant aromatic compounds in PM2.5 (particles with aerodynamic diameter ≤2.5 μm) were highly condensed hydrocarbons with 4–8 aromatic rings and their homologues with very short alkyl chains. Furthermore, heteroatom-containing hydrocarbons were found as the significant components of the aromatic fractions: O1, O2, N1, and S1 class species with 10–28 DBEs (double bond equivalents) and 14–38 carbon numbers were identified by APPI FT-ICR MS. The heteroatom PAHs had similar DBEs and carbon number distribution as regular PAHs.

The hindered stepwise aggregation (HSA) model was used to elucidate the molecular aggregation in heavy petroleum fractions which were derived from supercritical fluid extraction fractionation (SFEF) of Venezuela Orinoco vacuum residue (VR). The SFEF fractions consisted of multiple extractable narrow fractions and a nonextractable end-cut. The SFEF fractions were diluted with toluene, and their number-average molecular weights (MWs) were determined using vapor pressure osmometry (VPO). The initial molecular association constants (K1) and aggregation hindrance factors (H) of the HSA model for each SFEF fraction were calculated from the VPO MWs at various SFEF solution concentrations. The results showed that the HSA model fit well with VPO MW data and the parameters of the HSA model are physically significant. The values of MW and K1 increased as the SFEF fraction became heavier. The SFEF end-cut had the highest K1 and lowest H value, in which the aggregates were 2 to 8 monomers. Except for the initial fraction, all the SFEF fractions formed aggregates at solution concentrations higher than 30 g/L. The value of K1 was dependent on the number of aromatic rings, whereas H is dependent on the size of aromatic ring and side-chain length. The VPO MWs of light SFEF fractions were in agreement with those determined from electrospray ionization (ESI) mass spectrometry (MS) or gel permission chromatography (GPC). The VPO MWs of the highly aggregated SFEF fractions were higher than those of ESI MS due to low ionization efficiency but were much lower than those of GPC.

Venezuela Orinoco extra-heavy-crude-oil-derived vacuum resid (VR) was subjected to supercritical fluid extraction and fractionation (SFEF) to prepare multiple narrow fractions. The SFEF fractions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with various ionization techniques, including positive-ion electrospray ionization (ESI), negative-ion ESI, positive-ion atmospheric pressure photoionization (APPI), and sulfur methylation followed by positive-ion ESI. The results showed that the SFEF separates the VR species by their molecular weights and degrees of molecular condensation. The mass ranges of compounds determined by various ionization techniques were comparable. The FT-ICR MS data were in agreement with the elemental analysis and molecular weight determined by gel permeation chromatography (GPC) and vapor pressure osmometry (VPO) for the extractable fractions. The molecular compositions of SFEF fractions determined by FT-ICR MS provide important clues for the understanding of the molecular composition for the unextractable end-cut (asphaltenes). Each ionization technique favors identification of certain compounds in heavy petroleum fractions and discriminates against others. APPI allows for a general overview of species present in heavy petroleum fractions, because of its ability to ionize a wide range of species. ESI is more selective toward polar species. A thorough characterization of species in heavy petroleum fractions cannot be achieved by using an ionization technique; however, it can be performed by combining various ionization techniques.

Heavy petroleum fractions, which have distinct chemical and physical properties, are becoming important refinery feedstocks. In comparison to aromatic and heteroatom-containing compounds, the saturate compounds in heavy petroleum fractions have rarely been analyzed using recent advanced mass spectrometry methods. In this work, the compositions of saturate fractions derived from six vacuum residua (VR) of different geological origins were determined and compared. Saturate fractions were subjected to ruthenium-ion-catalyzed oxidation (RICO) derivatization and characterized with negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that the VR-derived saturates consisted of n-paraffins, isoparaffins, and naphthenes with 1–10 rings. The maximum double bond equivalent (DBE) values of species in various VR-derived saturates were similar. The maximum carbon number of VR-derived saturates was up to 100. The maximum carbon numbers of naphthenes in VR-derived saturates were generally greater than that of paraffins. The relative abundances and ranges of carbon numbers of the various species in VR-derived saturates differed depending upon their geological origin and the distillation temperature of samples. Compounds with 0–6 naphthenic rings were highly abundant in the VR-derived saturates. On the basis of the results of this study, the RICO/ESI FT-ICR MS method shows promise as a potential semi-quantitative analysis for saturates in heavy petroleum fractions.

•Systematic test of apodization on both simulated and actual complex mixture FT-ICR signals.•Effect of apodization on 13C isotope ratio is negligible.•Complex FT-ICR analysis should sacrifice dynamic range to increase resolving power.•Low dynamic window functions are recommended for less resolving power reduction while ensuring correct peak selection.Apodization is a generally applied signal processing method in FT-ICR MS (Fourier transform ion cyclotron resonance mass spectrometry) analysis for complex petroleum samples that is used to lower the spectral leakage and smoothen the spectrum line shape. Present study evaluates the effect of apodization on the FT-ICR MS results through a systematic examination on both simulated and actual heavy petroleum signals. The result shows that the resolving power, instead of the dynamic range, is the key factor for heavy petroleum FT-ICR MS analysis due to the severe peak overlapping. Window functions with high dynamic range will reduce the resolving power so that many of the species cannot be detected. The improvement on accuracy of apodization with peak intensity is negligible and all the window functions have similar intensity error. Low dynamic range window functions perform better for FT-ICR MS analysis since they have less resolving power reduction and the spectral leakage is eliminated to ensure correct peak selection. Sine-bell and low beta value Kaiser window functions are recommended for complex mixtures.

Coal tar has been considered as a potential energy alternative because of dwindling supplies of petroleum. To determine if the coal tar could be refined and upgraded to produce clean transportation fuels, detailed investigation of its composition is necessary, particularly for identifying the acidic components that account for about one-quarter of the weight of the coal tar. A middle-temperature coal tar (MTCT) and its fractions were characterized by gas chromatography–mass spectrometry (GC–MS) and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with different ion transmission modes for high- and low-mass ions. Analytical results of narrow distillation fractions from FT-ICR MS agreed reasonably well with those from GC–MS, although each technique has its own advantages and disadvantages. In this work, FT-ICR MS was demonstrated to be capable of characterizing small molecules of <100 Da using appropriate operation conditions, thus yielding mass distributions to compare to GC–MS results. A continuous distribution in double bond equivalent (DBE) and carbon number was observed with the distillates of increasing boiling point, while the composition of the distillation residue was much more complex than that of distillates. Acidic compounds containing 1–7 oxygen atoms were observed in the MTCT by FT-ICR MS, with O1 and O2 classes being dominant. Various phenolic compounds with 1–4 aromatic rings were identified on the basis of literature references, including some molecules having structures resembling known biomarkers in petroleum and coal.

Venezuela Orinoco heavy crude oil was fractionated into diesel, vacuum gas oil (VGO), vacuum residue (VR), and asphaltene fractions, which were subjected to molecular weight (MW) measurement by vapor pressure osmometry (VPO). The VPO is known to overestimate the average molecular weight (MW) of heavy hydrocarbons, because of molecular aggregation. This paper proposes a hindered stepwise aggregation (HSA) model to simulate the molecular aggregation and used the model to estimate the true MW of heavy petroleum fractions. A data regression procedure was developed to determine the model parameters, aggregation equilibrium constant, and aggregate distribution, using a fast simulated annealing (FSA) algorithm based on the VPO data. This data analysis method is self-tuned to fit the VPO data to the HSA models of various petroleum fractions using the optimized solution of the FSA algorithm. The results showed that the VPO data of heavy petroleum fractions at various solution concentrations were in good agreement with those predicted by the HSA model. The aggregation equilibrium constant and aggregate distribution data obtained from the HSA model suggested that various degrees of molecular aggregation occur in heavy petroleum fractions. The molecules of diesel and VGO were monomers, regardless of the solution concentration. The molecules of VR formed dimer aggregates at high solution concentrations; the number of dimer aggregates exceeded that of monomers as the solution concentration increased. The molecules of asphaltenes were polymer aggregates. The size of asphaltene polymer aggregates increased significantly with the solution concentration. The MW of asphaltenes determined by the HSA model was much lower than that by the conventional linear regression method.

Asphaltenes-free vacuum resid derived deasphalted oils (DAOs) from Chinese Liaohe (LDAO) and Venezuela Orinoco (VDAO) were subjected to catalytic hydrotreating. Electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses were performed on LDAO and VDAO before and after hydrotreating to determine the structural composition transformation of nitrogen-containing compounds as a result of hydrotreating. The results showed that the basic nitrogen contents of the two DAO before and after hydrotreating were relatively constant. However, the neutral nitrogen contents of hydrotreated LDAO and VDAO were dramatically reduced. The LDAO had a higher neutral nitrogen conversion than VDAO, even though LDAO had a higher neutral nitrogen content than VDAO prior to hydrotreating. The significant difference in nitrogen removal for the DAOs was due to the structural variation of the neutral nitrogen compounds. By plotting the double bond equivalent (DBE) value as a function of carbon number for N1 class species, the hydrodenitrogenation reactivities of nitrogen compounds could be classified as easy- and hard-to-convert nitrogen compounds. The easy-to-convert nitrogen compounds have more unsaturated cores and have less and/or shorter alkyl side chains than the hard-to-convert nitrogen compounds which have long alkyl side chains.

Venezuela Orinoco heavy crude oil was sequentially separated into several subfractions to determine the contents and types of vanadyl porphyrins contained in the products. Vanadium contents in each subfraction were detected using an atomic absorption spectrometer (AAS) combined with the characterization of vanadyl porphyrins by ultraviolet–visible (UV–vis) spectroscopy and positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Six types of petroleum vanadyl porphyrins, which have been identified previously, were well-characterized with the detailed fractionation. Three new series of vanadyl porphyrins corresponding to molecules of CnHmN4VO2, CnHmN4VO3, and CnHmN4VO4, respectively, were identified in addition to the six known types of vanadyl porphyrins.

We have investigated and established a preparative method of using a solid-phase extraction cartridge containing Ag+-exchange resin (Ag+-SPE) for separating olefins and paraffins in the saturate fractions of coal tar and petroleum coker oil. The successful separation of paraffins and olefins was confirmed by gas chromatography coupled with mass spectrometry (GC–MS). Proton nuclear magnetic resonance (1H NMR) spectroscopy was applied to determine the olefin structures for olefin-type distributions. None or negligible amounts of iso-α-olefins were detected by 1H NMR in the coal tar but were found significant in the coker oil. Gas chromatography coupled field ionization time-of-flight mass spectrometry (GC–FI-TOF MS) was employed to determine the molecular distribution of paraffins and olefins. With separate paraffin and olefin fractions, the differentiation between isomers, such as monocycloparaffins versus monoolefins, can be made.

An atypical distribution of steroids occurred in oilsand and oil samples in the Jinxian Sag, Bohai Bay Basin, northern China. It is featured by usually abundant C21–C26 short-chain steranes that are derived from the cleavage of the weak C–S bonds at the C-17 and C-20 positions. Sulfur-containing petroleum biomarkers were further analyzed in these sulfur-rich heavy oils by comprehensive two-dimensional gas chromatography (GC × GC) using sulfur-specific detection to locate and confirm sulfur species and GC × GC time-of-flight mass spectrometry (TOF MS) to identify previously unknown sulfur-containing biomarkers. Preliminary GC–MS analysis revealed a series of compounds yielding characteristic fragment ions consistent with thiophenic substructures. For confirmation, GC × GC–sulfur chemiluminescence detection (SCD) was used to confirm the sulfur moiety. The molecular structures of sulfur biomarkers were proposed as unsaturated isoprenoid thiophenes based on fragmentation patterns observed in their 70 eV electron-impact ionization (EI) mass spectra. There were constant neutral losses of 71 and 111 Da from the molecular ions in the 70 eV EI mass spectra throughout a whole series. The endeavor of sulfur-containing biomarker characterization may provide some clues of paleotransformation of biological precursors and geological products in oil/kerogen under thermal stress during burial and resolve some missing links between the biosphere and the geosphere.

Negative-ion electrospray ionization (ESI) enabled the direct mass spectrographic analysis of phenols, naphthenic acids, and neutral nitrogen compounds in petroleum fractions without prefractionation; however, ESI results provide few quantitative and structural information about the analytes: the composition of acidic compounds in heavy oil, such as distillate resid, is still unclear. In this study, extrography was used to fractionate oilsands bitumen-derived vacuum-topped bitumen (VTB) and its maltene and asphaltene fractions into multiple subfractions. The molecular compositions of acidic functional compounds in the VTB and its subfractions were analyzed by negative-ion ESI Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Extrographic separation was a necessary step to isolate acidic compounds of various acidities and/or polarities in vacuum resid fractions to achieve a systematic analysis. The results showed that the O2 class species in VTB were highly condensed phenols and carboxylic acids. The maltene fraction contained most of the less condensed naphthenic acids, whereas the asphaltene fraction contained highly condensed carboxylic acids and phenolic compounds with a bouble-bond equivalent (DBE) higher than 6. The presence of acids had no significant impact on the yield of asphaltenes in n-C7 solvent precipitation. Acid-free asphaltene fractions, which account for more than 90 wt % of the asphaltenes, cannot be ionized by negative-ion ESI.

Using heptane, toluene, and tetrahydrofuran (THF) as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both asphaltene and its fractions were analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The application of UV-vis spectrometer in characterizing asphaltene composition and measuring asphaltene concentration was discussed. About 11.9 wt% asphaltene components adsorbed permanently on silica gel in the extrography column after excessive elution with various solvents. In negative FT-ICR MS, the mass spectra show that acidic and neutral nitrogen-containing compounds such as N1 and N1S1 mainly existe in the first three less polar fractions, while oxygen-containing compounds such as O2, O2S, O2S2, O3, and O4 show high relative abundance in more polar fractions. These results suggest oxygen-containing compounds have stronger adsorption ability with silica gel. It was observed that the double bond equivalence (DBE) distribution of N1 class species in the fractions shifted to higher values while the carbon number shifted to smaller numbers as polarity of fractions increased. This indicates that acidic and neutral N1 compounds with longer carbon chain and less aromaticity have less polarity compared with those with shorter carbon chain and stronger aromaticity. UV-vis absorbance indicats that fractions containing the most aromatic and most polar asphaltene have better absorbance at long wavelength, while the fractions that consist of least aromatic and least polar asphatlenes show high absorbance at short wavelength.

A vacuum topped Canadian oilsands bitumen (VTB) was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph (GPC), 1H-NMR spectroscopy and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Effects of experimental conditions such as solvent types (n-C5, n-C6, and n-C7), solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular composition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The O2 species exhibited two different double bond equivalents (DBE) distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphaltenes. Compound class distributions are similar for maltenes derived from n-C5, n-C6, and n-C7, as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecular composition. A portion of neutral N1 species and acidic O2 species adsorbed on asphaltenes could be dissolved by increasing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.

The Liaohe crude oil with high total acid number (TAN) was subjected to thermal reaction at 300 °C to 500 °C. Reaction products were collected and analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to determine acid compounds in the crude oil. The double-bond equivalence (DBE) versus carbon number was used to characterize the oxygenated components in the feed and reaction products. The O2 class which mainly corresponds to naphthenic acids decarboxylated at 350–400 °C, resulting in a sharply decrease in TAN. Phenols (O1 class) are more thermally stable than carboxylic acids. Carboxylic acids were also thermally cracked into smaller molecular size acids, evidenced by the presence of acetic acid, propanoic acid, and butyric acid in the liquid product. These small acid species are strong acids likely responsible for corrosion problems in refineries.

This paper examined the bond dissociation behavior and aromatic ring architecture of basic nitrogen compounds in Sudan heavy petroleum fraction. Both broadband and quadrupole isolation modes positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with collision induced dissociation (CID) techniques were used to characterize a low sulfur crude oil derived vacuum residuum (VR). The appropriate CID operating condition was selected by comparing the molecular weight distributions of the basic nitrogen compounds under various CID operating conditions. Both odd- and even-electron fragment ions were observed from the mass spectrum, indicating that the heterolytic and homolytic bond cleavages occurred simultaneously during the CID process. The odd-electron fragment ions were predominant in each class species, indicating preferential heterolytic bond cleavages. At the optimal CID condition, the alkyl groups decomposed deeply and just left the aromatic cores of the nitrogen compounds. No significant variation in double bond equivalent (DBE) value was observed between the fragment and parent ions, revealing that the domination of single core structure.

A Venezuela Orinoco petroleum vacuum residue (VR) was subjected to supercritical fluid extraction fractionation (SFEF) and separated into 13 extractable fractions and an unextractable end-cut. Detailed molecular composition of polar heteroatom species in the SFEF subfractions were determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The SFEF subfractions were also subjected to high-temperature gas chromatography (GC) for their simulated distillation analysis, gel permeation chromatography (GPC) for their molecular distributions, and open column liquid chromatography for their saturates, aromatics, resins, and asphaltenes (SARA) compositions. In ESI FT-ICR analysis, the mass spectra showed that the mass range and maximum peak of the SFEF subfraction increased as the SFEF subfraction became heavier. Multifunctional group compounds, such as N1S1, N1S2, N1O1, and N2, show high relative abundance in heavier subfractions. The double bond equivalence (DBE) values and carbon numbers of all class species increased steadily as the SFEF subfraction became heavier. This indicated that the molecules in various SFEF subfractions are separated by their aromaticity and molecular weight. The SFEF end-cut could not be thoroughly characterized by ESI because of its low intensity, while basic species detected by positive-ion ESI were suppressed by a strong response of metal porphyrin species. Results from GPC and SARA compositional analysis show that the end-cut enriches most of the asphaltene in feedstock and has the highest apparent molecular size.

A middle-temperature coal tar (MTCT) was distilled into multiple narrow boiling point fractions. The MTCT and its distillate fractions were subjected to bulk property analysis and molecular compositional characterization by gas chromatography–mass spectrometry. Acid/basic liquid extraction was performed to separate the MTCT into acidic, basic, and neutral fractions, which were characterized by positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The dominant compounds in MTCT were aromatics, phenols, and normal alkanes. The number of carbon atoms in the substituent chains varied over a relatively broad range for each homology. The composition of narrow distillate fractions varied: light naphtha (<100 °C) had a high benzene content, which is an unsuitable gasoline blending stock; middle distillates (160–240 °C) enriched with phenols, which is a good extraction feedstock for chemical products; and heavy distillates (>240 °C) are a hydrotreating feedstock for clean fuel production. The MTCT had large amounts of acidic and basic components, consisting of oxygen- and nitrogen-containing molecules. The basic fraction accounted for 2.68 wt % MTCT. Only nitrogen compounds in the MTCT could be detected by positive-ion ESI. Most of the oxygen-containing molecules exhibited a weak acidity and were partially extracted into the acidic fraction. Basic nitrogen compounds co-existed in the acidic, basic, and neutral fractions of MTCT. However, the molecular compositions of basic nitrogen compounds were different among these fractions: molecules with low carbon numbers and high aromaticities were found in the acidic and basic fractions, whereas mono-nitrogen basic compounds were abundant in the neutral fraction.

A commercial lignite gasification-derived middle-temperature coal tar (MTCT) was subjected to acid–base extraction to obtain acidic, basic, and neutral fractions. The neutral fraction was characterized by mass spectrometry (MS) for hydrocarbon-group-type analysis and further fractionated by extrography into six subfractions, which were characterized by gas chromatography–mass spectrometry (GC–MS). Saturate, aromatic, and resin fractions of the neutral fraction accounted for 16.4, 47.6, and 36.0 wt %, respectively. The GC–MS analysis showed that the first neutral subfraction (15.7 wt %) contained alkanes, alkenes, and cycloalkanes; the second subfraction (52.0 wt %) contained 1–6-ring aromatics; the third subfraction (4.6 wt %) contained neutral nitrogen compounds, such as indoles, carbazoles, and benzocarbazoles; the fourth subfraction (8.2 wt %) contained neutral polar compounds, such as C8–C28 alkyl nitriles and aliphatic and aromatic ketones, such as 4-, 5-, and 6-ketones and phenyl ketones, derived from a series of propiophenone to decanophenone; the fifth subfraction (14.9 wt %) contained 2-ketones and aromatic ketones, such as acetophenones, indanones, and acetonaphthones; and most of the sixth subfraction (1.3 wt %) cannot be eluted from GC. Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze the third neutral subfraction, which was enriched with neutral nitrogen compounds. In addition to indoles, carbazoles, and benzocarbazoles, FT-ICR MS analysis showed that dibenzocarbazoles and tribenzocarbazoles with various carbon numbers were present in the third neutral subfraction.

A coker heavy gas oil (CHGO) was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The resin fraction was separated into six subfractions by high-performance liquid chromatography (HPLC). The CHGO and its subfractions were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The mass spectra showed that the mass range of basic and neutral nitrogen compounds was 200−450 and 160−400 Da, respectively. Five nitrogen class species, N1, N2, N1O1, N1O2, and N1S1, were assigned in the positive-ion spectrum. Six nitrogen class species, N1, N2, N1O1, N1O2, N2O1, and N1S1, were assigned in the negative-ion spectrum. Among the identified nitrogen compounds, the N1 class species was dominant. The N1 class species were enriched in the resin fraction. The N2 class species are likely amphoteric molecules and were enriched in the asphaltene fraction. The composition of nitrogen compounds in the resin subfractions varied significantly in double-bond equivalence (DBE) and carbon number. As the polarity of the resin subfraction increased, the average molecular weights of the nitrogen compounds decreased, DBE values for each heteroatom class species increased, and the N2 class species became the dominant nitrogen compounds at the expense of the N1 class species.

Detailed characterization of oil sludge obtained from an electric dehydrator was performed using various analytical techniques and compared with that of its parent crude oil. The findings showed that the oil sludge was a stable emulsion consisting of oil, water, solids, and polyethers, which are chemical additives commonly used in the oilfield and refinery operations. Spectral peaks derived from positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) were assigned to sodium adducts [M + Na]+ for four types of polyethers that are nonionic surfactants. The Na1Ox class species found in the sludge at the bottom section of an electric dehydrator were likely due to their low solubility in oil as the number of oxygen atoms in these compounds increased. Polyethers were likely involved in the formation of oil sludge in the electric dehydrator. Sodium adducts, such as [M – 2H + Na]−, [M – 3H + 2Na]−, and [M – 4H + 3Na]−, of both C80 and C60+ ARN acids found in the fractions derived from acidified toluene extraction of oil sludge solids ionized by negative-ion ESI were also identified that confirm the assignment of ARN acids.

Detailed elemental composition and distribution of sulfides and thiophenic compounds in four subfractions of Kazakhstan vacuum gas oil (VGO) were determined by positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The sulfides in VGO subfractions were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI). The sulfur compounds in the oxidized VGO subfractions were reacted by methylation to form methylsulfonium salts and were then characterized. Elemental composition and distribution of sulfides and thiophenic compounds in the VGO subfractions were characterized by their double bond equivalents (DBE) values and carbon numbers before and after the oxidation reactions. The results showed that the S1 class species with DBE values of 6 and greater are likely thiophenic compounds, while those with DBE values less than 6 are sulfides. As boiling point of VGO increased, the abundance of thiophenic compounds increased. DBE value and carbon number of the compounds also increased.

Crude oil was subjected to extrography to obtain various acid compounds in multiple subfractions. Negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography–mass spectrometry (GC–MS) were used to determine the acid compounds in the crude oil subfractions. Isoprenoidyl phenols with molecular formulas of C27H48O and C28H50O, which were previously deduced as sterol-type compounds, were highly enriched in a subfraction and confirmed by GC–MS. The mass peak with a molecular formula of C27H46O2 was identified as δ-tocopherol. The eluting sequence of the various compounds in crude oil was N1 carbazoles, followed by O1 class acid compounds, then O2 class acid compounds, and finally, N1O2, O3, and O4 class acid compounds. The results show that extrography is an adequate separation technique for partitioning crude oil acid compounds into various subfractions.

A novel analytical method for identifying sulfides in petroleum and its fractions was developed. Sulfides in petroleum were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI) and identified by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). A variety of model sulfur compounds were examined to evaluate the selective oxidization and ionization efficiencies for sulfur compounds in petroleum. Two fractions, straight-run diesel and saturates of Athabasca oilsands bitumen were investigated using this approach. The oxidization process was highly selective for sulfides from thiophenes and aromatic hydrocarbons. Oxidation generated sulfoxides were ionized by positive-ion ESI and analyzed by FT-ICR MS. Mass spectra revealed the composition characteristics of sulfides in the diesel by contrasting the double bond equivalence (DBE) and carbon number distribution of sulfur compounds before and after oxidation. The abundant sulfides in the straight run diesel and saturates fraction of oilsands bitumen had DBE values of 1−3 and 1−4, respectively.

A Chinese crude oil was distilled into multiple narrow boiling fractions. The crude oil, 39 narrow distillate fractions (up to 560 °C), and atmospheric and vacuum residues were analyzed using negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The heteroatoms, N1, N2, N1O1, N1O2, O1, and O2 class species, were identified and characterized by double-bond equivalent (DBE) values and carbon numbers. The composition of crude oil was correlated with increased boiling point. Most abundant O1 and O2 class species had DBE values and carbon numbers corresponding to biological skeleton structures, such as hopanoic acid, secohopanoic acid, and sterol. The distribution of acids and neutral nitrogen compounds in the various fractions were determined. At higher carbon numbers, the amount of the compounds and DBE values increased gradually with the boiling point for most oil fractions. The abundant N1 class species were centered at DBE values of 9, 12, 15, and 18. These were likely pyrrolic compounds with various numbers of aromatic rings. Species such as hopanoic acids and secohopanoic acids were highly abundant in fractions above 500 °C. Sterol-like compounds were enriched in the 460−500 °C fractions. These are likely the major species causing a high total acid number (TAN) in the crude oil.

Six coker gas oils (CGOs) and three basic fractions extracted from one of the CGOs by 0.1, 0.4, and 1 M HCl hydrochloric acid were characterized by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and compared to those analyzed by gas chromatography mass spectrometry (GC-MS). The ultra high mass resolving power and high mass accuracy of FT-ICR MS allow the assignment of a unique elemental composition to each peak in the mass spectrum. Basic nitrogen species were characterized by class, type, and carbon number. The mass spectra of the CGOs at the 200−500 Da mass range were similar, but the distribution of double bond equivalence (DBE) versus carbon number were different. Among the N, N2, NO, and NS that were identified in CGOs, the N class nitrogen species were dominant. The results showed that hydrotreating reduced the relative abundance of all class species, except for the N class species. This suggests that some N class species are refractory to hydrotreating. The molecular weight of nitrogen species in the acid-extracted basic nitrogen fraction of CGO was lower than that of its parent CGO. The N3, NO2, and N2O class species were clearly identified and concentrated in the basic nitrogen fraction, but were not detected in their parent CGO. The N class species with ring plus DBE value of 4−16 in the basic nitrogen fraction were also identified by GC-MS analysis.

Venezuela crude oil was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The sulfur compounds in the crude oil and its SARA fractions were reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 class species were identified in crude oil derived methylsulfonium salts. The molecular composition and mass distribution of sulfur compounds in the subfractions were distinctly different. Small amounts of S1 class species (cyclic-ring sulfides) were present in the saturates fraction. Thiophenic sulfur compounds were dominant in the aromatics fraction. Complex multiheteroatoms (N1Sy, OxSy, and N1OxSy class species) were present in the resins and asphaltenes fractions. The relative abundance plots of double-bond equivalence (DBE) versus the carbon number of S1, S2, O1S1, and O2S1 class species showed that as the molecular polarity of the fraction increased, the DBE values of the abundant Sy class species increased. SARA fractionation isolates the highly aromatic sulfur species in the resins and asphaltenes fractions, which are not observed in the parent crude oil sample.

Dihydroxy aromatics in coal tar undergo rapid coupling reactions with each other and with some coal-derived species during coal pyrolysis and liquefaction. However, only limited information on the structure of dihydroxy aromatics is known. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography−mass spectrometry (GC−MS) were used to characterize the dihydroxy aromatics in a low-temperature pyrolyzed coal tar and its distillate and residue fractions. Negative-ion electrospray ionization (ESI) FT-ICR MS spectra of coal-tar-derived samples had low molecular masses and narrow mass ranges. Negative-ion ESI is extremely selective for the dihydroxy aromatics present in coal tar. The O2 class species had the highest ion intensity among the species in the negative-ion FT-ICR mass spectrum for each sample. Dihydroxy compounds with an aromatic core structure of benzene, indan, biphenyl (and/or acenaphthene), and naphthalene were identified in the distillate fractions. Dihydroxy compounds in the residue fraction were dihydroxy fluorenes and phenanthrenes (and/or anthracenes). The O2 class species with relatively high molecular masses were likely dihydroxy acenaphthylenes and/or hydroxy dibenzofurans but could not be distinguished from each other because these compounds have the same molecular mass.

Neutral nitrogen compounds have been used as molecular markers for tracking secondary oil migration in geochemistry. However, the distribution of neutral nitrogen compounds in the separation process is not well-characterized because the conventional analytical technique, such as gas chromatography−mass spectrometry (GC−MS), is non-selective for neutral nitrogen and not capable of detecting non-volatile high-molecular-weight compounds. In this paper, a crude oil was subjected to the traditional two-step open-column liquid chromatography (LC) technique to prepare subfractions, which were characterized for their molecular composition of neutral nitrogen compounds by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results showed that the two-step LC technique produced a low yield of carbazole in the neutral nitrogen fraction. The neutral nitrogen fraction was enriched with low-molecular-weight neutral nitrogen compounds. Most N1 class species with relatively low double-bond equivalent (DBE) values and high carbon numbers were eluted into the aromatic fraction, and a portion of neutral nitrogen compounds was eluted into the amino fraction, which was not expected. Because the neutral nitrogen compounds detected by GC−MS analysis only account for a fraction of total neutral nitrogen compounds, caution should be exercised in interpreting the analytical data obtained from the two-step LC technique. The analytical bias of the separation technique could lead to erroneous geochemical interpretations when a low yield of carbazole in the neutral nitrogen fraction was derived. Negative-ion ESI FT-ICR MS was an effective tool to monitor and evaluate the separation technique for neutral nitrogen compounds in crude oil.

Nitrogen-, sulfur-, and oxygen-containing hydrocarbons in a residue fluid catalytic cracking (RFCC)-derived diesel were characterized by a gas chromatograph equipped with a pulsed flame photometric detector and an electron impact, ammonia chemical ionization mass spectrometer. Caustic and acid extractions on RFCC diesel were performed to isolate the phenolic and basic nitrogen compounds, respectively. The fraction of RFCC diesel that contained the basic nitrogen compounds was reacted with acetic anhydride to allow for chromatographic separation of amino-aromatic compounds from the rest of the non-reactive basic nitrogen compounds. The majority of basic nitrogen compounds were anilines, as expected. Non-basic nitrogen compounds in RFCC diesel were alkyl indoles and alkyl carbazoles. Double-ring and poly-aromatic amines were identified in RFCC diesel by the acetylation reaction. The majority of sulfur compounds in RFCC diesel were alkyl benzothiophenes and dibenzothiophenes, after being isolated by Pd2+ ligand-exchange chromatography. Dihydrobenzohiophenes and dihydronaphthanthiophenes, despite a low concentration, were also identified in the subfractions. The majority of oxygen compounds in RFCC diesel were phenolic compounds. In addition to alkylphenols, bicyclic and polycyclic phenols were identified and characterized in the acidic fraction.

Acephenanthrylene and aceanthrylene in aromatic fraction of aerosols were identified by means of online hydrogenation gas chromatography mass spectrometry(GCMS). Compared aerosols from various sources, acephenanthrylene and aceanthrylene were ubiquitously present in urban aerosol. High concentration of acephenanthrylene and aceanthrylene were found in agricultural biomass and coal combustion particles. However, it is difficult to detect in exhaust from gasoline and diesel engine, dustfall, waste water, soil, and sediment. Combustion emissions were considered the major source of acephenanthrylene and aceanthrylene, which can be used as a potential molecular marker for the source pollution in urban aerosols.

A red pine fast pyrolysis bio-oil was subjected to sequential solvent fractionation into n-hexane soluble (HS), ether soluble (ES), ether insoluble (EIS), dichloromethane soluble (DS), and methanol soluble (MeS) fractions. The volatile components of bio-oil were analyzed by gas chromatography–mass spectrometry (GC–MS), indicating the presence of acids, aldehydes, ketones, alcohols, phenols, and anhydromonosaccharides, which consisted of methoxy, hydroxy, and carbonyl functional groups. These results imply that the bio-oil was similar to the most reported fast pyrolysis bio-oil samples in molecular composition. The bio-oil and its five subfractions were analyzed by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The predominant compounds in bio-oil were O2–O17 class species with 1–22 double-bond equivalent (DBE) values and 4–39 carbon numbers. The most abundant class species in biocrude oil, HS, ES, EIS, DS, and MeS subfractions were O7, O6, O8, O10, O7, and O8 class species, respectively. The predominant EIS subfraction presented an obvious relative low DBE value, sustaining the tentative identification as “sugar fraction”. The predominant compounds in DS subfraction were likely lignin dimers, whereas those in MeS subfraction should be lignin dimers and trimers. The number of oxygen atoms of the bio-oil compounds was negatively correlated with the average DBE value, indicating that oxygen atoms were present in various functional groups of the bio-oil compounds. The N1Ox class species were also identified, which contained 1–16 DBE and 6–30 carbon numbers.