Maltene Fractions Research Articles

Petrology and organic geochemistry of the Middle Devonian cutinitic liptobioliths from Luquan region, Yunnan Province, China

The majority of Middle Devonian coal samples from Wujing (WJ), Damo (DM), and Batang (BT) areas in the Luquan region of China have cutinite content exceeding 50%, classifying them as typical cutinitic liptobioliths. These coals are notable for their thinly-bedded texture, which allows them to split readily into leaf-like laminae. However, coals from these areas display distinct macroscopic, microscopic, and geochemical features. The split laminae from WJ and DM coals are black and ribbon-like, with those from WJ being notably longer and wider. In contrast, BT coal laminae are irregular, small fragments with golden or brown hues. Correspondingly, the cutinite in WJ coals is predominantly thick-walled, DM coals primarily contain a medium-walled type, and BT coals are characterized by a thin-walled type. Additionally, BT coals are rich in sporinite, with some classified as sporinite-rich durain or sporinitic liptobiolith. Abundant tetracyclic diterpenoids were detected in the maltene fraction of all the coal extracts. The concentration and composition of these diterpenoids are influenced by the content and type of cutinite present in the coals. The presence of tetracyclic diterpenoids, with beyerane, atisane and kaurane skeletons, had already evolved in early land plants. This implies that the precursors of these compounds were likely significant components of the cuticles of early land plants or, at least coexisted alongside plant cuticles. The spore assemblages in coals and the microscopic features of cutinite suggest that the coal-forming plants of the Luquan cutinitic liptobioliths were early land plants, predominantly herbaceous lycopsids, rhyniopsids, Orestovia and Spongiophyton. However, it is important to note that the specific types of these coal-forming plants may vary by areas. This variation leads to the distinctive macroscopic and microscopic characteristics observed in coals from different locations.Cutinitic liptobiolith appears to have been exclusive to the Middle Devonian period, especially during the Givetian. The emergence of this distinct coal type is likely due to the unique structure of Devonian land plants. Specifically, the combination of well-developed cuticles and less developed woody tissues in these early land plants might have played a key role in the formation of cutinitic liptobioliths.

Isolation and Characterization of Interfacially Active Molecules from Asphaltene and Maltene Fractions

Isolation and Characterization of Interfacially Active Molecules from Asphaltene and Maltene Fractions

Preliminary study of crude oils from Shabwah depression in the Central Sab'atayn Basin (Yemen): Revealing oil-oil correlation with organic matter input and maturity based on geochemical properties of maltene and asphaltene fractions

This study was investigated eleven crude oil samples from representing Jurassic reservoir sandstones from the Al–Uqlah Oilfield in the Shabwah depression, using physical and geochemical aspects for saturated, aromatic, and asphaltene fractions to gain information about their source rock characteristics, particularly the conditions of depositional environment, thermal maturity and organic matter (OM) character. The overall results show that the examined oils have API gravity values between 38° and 43°, indicating that most crude oils are light and not biodegradable; nevertheless, oil samples, sweet oils with a low sulfur content, with S of <1 wt%. The molecular structure of the asphaltene in these oils derived from Py–GC suggests mainly paraffinic oil exhibiting high to low wax content derived from Types I and II kerogens. This claim agrees with the high saturated HC of more than 38% and significant levels of aromatic HC and polar components. The studied oil were generated from clay-rich source rocks, containing a mixed OM origin of marine and terrestrial organic matter and deposited under sub-oxic depositional environmental conditions as indicated by their biomarker of the saturated and aromatic fractions. The Py–GC structure of the asphaltene together with the environment-related biomarker indicators reveals the existence of two oil families. The first oil family represented in the majority of the studied oils and characterised as waxy paraffinic oil and generated from a mixture of organic matter, with significant terrestrial land plant input and deposited in sub-oxic environmental conditions. Other oil samples belonged the second oil family; these samples are predominantly P–N-A oils with low wax content and were derived from marine-source rock, containing significant contributions from aquatic OM and little input from terrestrial OM and deposited under more reducing environmental conditions. The biomarker and non-biomarker maturity ratios indicate that thermally mature source rocks generated the investigated crude oils of both oil families, corresponding to the peak oil window.

Experiment and multiscale molecular simulations on the Cu absorption by biochar-modified asphalt: An insight into removal capability and mechanism of heavy metals from stormwater runoff

Asphalt has been the primary material for pavements and other building components such as roof shingles and waterproofing systems, which can be the path for stormwater runoff pollutants such as heavy metals (HMs). In this study, the capability and mechanism of asphalt and biochar-modified asphalt (BMA) to remove Cu as the typical HM found in the road dust and surface runoff were fundamentally explored for the first time. Experiment and multiscale molecular simulations were performed. Molecular dynamics (MD) simulations showed the Cu absorption into the asphalts. Monte Carlo (MC) and density functional theory (DFT) revealed the detailed mechanism of Cu absorption. Biochar (BC) presence modified the spatial distribution of maltene and asphaltene fractions in asphalt and enhanced the absorption. Maltenes were absorbed into the porous structure of BC, leaving more asphaltenes in the asphalt part of BMA. Asphaltenes were the Cu adsorbing preference sites ascribed to the cation-π interaction between Cu and the aromatic plane. The DFT simulations also suggested favourable adsorption of other commonly found metals (e.g., Cr, Pb, Ni, Cd, and Zn) onto asphaltenes. The present study found the capability and mechanism of BMA and asphalt to remove HMs at the molecular scales, providing a path for designing asphalts with value-added functionality in minimizing environmental pollution.

Dilauryl thiodipropionate as a regeneration agent for reclaimed asphalts

Constructing asphalt pavements using reclaimed asphalt pavement (RAP) instead of exclusively virgin materials can significantly reduce environmental impacts and costs. However, the adverse effect of the aged RAP binder on asphalt mixtures’ workability and pavements’ performance restricts the percentage of RAP added to asphalt mixtures. As a solution, regeneration agents can be used to restore (even if partially) the physical, rheological, and chemical properties lost during the aging of the pavement in the field. Therefore, this paper evaluates the feasibility of using Dilauryl thiodipropionate (DLTDP) as a regeneration agent for RAP binders. This study considered two RAP binders (artificial and field). The impact of the DLTDP on the continuous performance grade of each RAP binder was investigated using the Dynamic Shear Rheometer (DSR). The antioxidant and regenerative effects of DLTDP on RAP binders were assessed by Fourier Transform Infrared spectroscopy (FTIR) and SARA fractionation. The adhesion between each RAP binder and granite aggregate (at dry and wet conditions) was evaluated using the bitumen bond strength (BBS) test. The rheological results indicated the softening effect of DLTDP on RAP binders. This softening effect may be explained by the increase of the maltene fractions (resins) and the reduction of the asphaltene fraction. Additionally, regenerated binders showed better oxidative aging and moisture susceptibility resistance than non-regenerated binders. Overall, the results indicated that adding DLTDP to RAP binders partially restored RAP binders' rheological and chemical composition to the target neat asphalt binder without significantly compromising the adhesion properties and rutting resistance. Moreover, the mentioned results verified the great potential of using DLTDP as a regeneration agent for RAP binders, making it possible to produce good-performing asphalt mixtures with a high RAP percentage.

Features of composition of heavy oil thermolysis products produced with addition of maltene fraction

A series of heavy oil (HO) thermolysis experiments in the presence of 2.5–10.0% maltene fraction recovered from oil has been performed. It has been shown that addition of maltene fraction provides HO conversion during thermolysis and a decrease in the viscosity of the products. An increase in the concentration of additive results in the decrease in coke content in the products as compared to reference experiment. Thermolysis conditions of HO of Ashal’chinskoe deposit (Russia), which give liquid products possessing viscosity of nearly 100 mm2/s in more than 97% yield in the presence of 5.0 and 10.0% of maltene fraction, have been determined, namely, 415°С and 30 atm in flow reactor.

Surfactant flooding for enhanced oil recovery – Insights on oil solubilization through optical spectroscopic approach

Surfactant flooding is a proven method employed to improve the recovery of crude oil from subsurface reservoirs but the knowledge about microemulsion formation, factors related to their stability, and the trapping mechanism of crude oil components in a microemulsion is still not clear for designing of injection fluid for specific crude type. The interaction mechanisms of four crude oils with surfactant-brine solutions were studied in this work for better insight into the molecular level mechanisms during surfactant flooding. UV–visible absorption and fluorescence spectra of the separated maltene and asphaltene fractions indicate the structural difference of the components in the molecular level, particularly, the size of the fused aromatic rings (FAR) present within individual bulk crude sample. Moreover, the FTIR spectra of the separated asphaltenes from the crude samples clearly showed the subtle difference in the functional groups present in respective FAR structures. Well-characterized compositionally different crude oils were mixed with four different surfactant-brine solutions (anionic – SDS, AOS, cationic - CTAB, and neutral - TX-100) and examined using UV–visible absorption and fluorescence spectroscopic approach. Detailed analysis of the acquired absorption and fluorescence spectra of the crude oil-surfactant-brine solutions distinctly demonstrate the entrapment of different crude oil components within the micelles formed by surfactants of different charges while the synchronous fluorescence spectra show the entrapment of specific size FARs within the specific micellar microenvironment. The results exhibit that the anionic surfactant entraps the smaller size (2–4) FARs whereas cationic and neutral surfactants entrap small as well as medium size (2–6) FARs within the formed micelles in the microemulsions. The present spectroscopic study signifies the importance of molecular-level interaction mechanisms for customized designing of surfactant solutions for maximizing crude oil recovery from petroleum reservoirs.

Molecular representation of coal-derived asphaltene based on high resolution mass spectrometry

The asphaltene separated by solubility in small molecular alkanes and toluene is the most structurally diverse and complex components in heavy oil, such as vacuum residue and coal tar. The coal-derived asphaltene is always regard as a succession of maltene fraction from small molecules to large molecules, and also a continuum of island- and archipelago-type structures, which is difficult to be identified accurately through current characterization methods. This limits the further study of molecular dynamics and reaction dynamics simulation of asphaltenes. In this work, a representation model of molecular composition and structure for coal-derived asphaltene is developed mainly based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with collision induced dissociation (CID) and traditional methods of nuclear magnetic resonance spectroscopy (13C NMR), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). Island- and archipelago-type structures are considered qualitatively in the representation of asphaltene. The asphaltene molecules are systematic assembled using stochastic algorithms and optimized by simulated annealing algorithm according to the group contribution method. The bulk properties for simulating asphaltenes are in good agreement with the experimental results giving acceptable predictions for the composition and structure of the asphaltenes. Moreover, the representative average structure asphaltene molecules are obtained using the developed molecular similarity function, which could be applied in the further study of molecular aggregation simulation and reaction kinetics simulation.

Source of organic matter and paleoenvironment of deposition of crude oils from the Niger Delta Basin

The study employed thirteen (13) crude oil samples from thirteen (13) producing wells, with the aim of examining the source of organic matter and the paleoenvironment of deposition. The crude oils were deasphaltened and the maltene fraction fractionated to obtain the saturates. The saturates were subjected to gas chromatography mass spectrometer (GCMS) analysis for the steranes, Isoprenoids and n-alkanes, and triterpanes and hopanes biomarker chromatograms. The biomarker composition of the studied oils indicates weakly oxic and reducing environmental conditions for the studied samples, consistent with marine deltaic environment of deposition. The study shows that the oils are associated with a mix of terrestrial and marine organic matter with a comparatively higher terrestrial and lower marine algae organic matter input. The oleanane index of 1.8 and the presence of oleanane in the studied samples denote higher terrigenous plant input into the source rock the generated the crude oils.

Study on spatio-compositional variations and source facies for oils from the Central Wrench Corridor of the Oriente Basin (Ecuador)

This research paper contains an integration of classical biomarker work with higher diamondoid examination to better characterize the petroleum systems in the north-central portion of the Sacha-Shushufindi Corridor in the Ecuadorian Oriente Basin. A set of crude oils, cuttings, and outcrop rock samples were analysed to address aspects such as source-rock lithology, paleo-depositional conditions, migration distances, as well as oil-oil and oil-source correlations. For this, gas chromatography-mass spectrometry (GC-MS), GC-triple-quadrupole MS (GC-MS/MS), and carbon isotope ratio mass spectrometry (IRMS) were performed on maltene fractions both from oils and rock extracts. GC-MS/MS analyses of oil-derived asphalthene hydrous pyrolysates were also included on the study. Classical biomarker results suggest mixing of pulses from distant siliciclastic and carbonate-rich Napo source rocks, with former oil charges being slightly biodegraded during the Paleogene and fresher Neogene pulses. These two types of Early-Late Cretaceous source rocks were deposited in shallow marine to nearshore and low-oxygen inner to middle neritic environments, respectively, with considerable and scarce contribution of land-plant material in both cases. Such differentiation of the two source facies types of the Napo Group is supported by results from quantitative extended diamondoid analysis (QEDA).

Behavior comparison of films of Mexican bitumen and its asphaltene and maltenes fractions at interfaces

The oil industry has been focused on bitumens and heavy oils due to the depletion of petroleum reservoirs. For this reason, we studied the interfacial behavior comparison of films of bitumen and their asphaltene and maltene fractions by means of the Langmuir balance and Brewster angle microscopy at the air–water interface. The films were transferred by Langmuir-Blodgett technique onto mica and grids to be further analyzed by AFM and SEM at different surface pressures. We found that the isotherm behavior of the bitumen depends on the amount of its asphaltene and maltene fractions, although the isotherm behavior of asphaltene and maltene fractions are quite different. BAM images of the bitumen and asphaltene samples show the formation of two- and three-dimensional domains, being the asphaltene domains the most rigid and compact structures. Maltenes seems to form large areas of mono- or bi-molecular films, and their structures are like those reported for lipid monolayers. The AFM images for the bitumen morphology exhibited polydisperse mesostructures with spherical and disk-like shapes, while asphaltene images revealed disk-like microstructures and some of these microstructures coalesce, resulting in the formation of worm-like and other small structures. AFM images of the maltene film revealed that they form a fine plaster that might agglutinates the asphaltenes. SEM images of bitumen film show a smooth and slightly porous surface with some layer detachments, holes and bright spots embedded, while asphaltene images presented porous surfaces with spherical- or drumstick-like structures. Maltene SEM images showed a surface with irregular pores. The results support a better understanding of the bitumen, asphaltene, and maltene fractions and suggest that the interfacial behavior of bitumen presents a synergy between its asphaltene and maltene fractions.

Variations in microbial ecology during the Toarcian Oceanic Anoxic Event (Early Jurassic) in the Qiangtang Basin, Tibet: Evidence from biomarker and carbon isotopes

Reduced animal diversity during mass extinctions is commonly associated with resurgence of microbial abundances. The Toarcian Oceanic Anoxic Event (T-OAE) was a critical interval characterized by dramatic perturbations to the environment and life in the oceans and on land. A comprehensive organic geochemical study was performed on 19 samples from the upper Pliensbachian-lower Toarcian interval of the Quse Formation across the T-OAE at the Bilong Co outcrop section (also known as Biluo Co) in the Qiangtang Basin. Bulk geochemical analysis [total organic carbon contents (TOC): 2.0–8.0% wt., S2: 11–37 mg hydrocarbon/g bulk rock, Tmax: 435–441 °C] consistently suggests a narrow thermal maturity range of the Quse shale samples. The δ13C of maltene (δ13Cmaltene) and kerogen (δ13Ckerogen) fractions generally agree with the previously published δ13Corg curves, demonstrating the global T-OAE negative carbon isotope excursion (N-CIE). The elemental composition suggests a predominance of Type II kerogen, indicating the kerogen composition casts minimal effect on carbon isotopic signals. Petrographic examination demonstrated that the kerogens are mainly composed of alginate and amorphous organic matter, suggesting that a dominant source of kerogen originated from primary producers such as marine photosynthetic species that recorded the carbon fixation isotopic signature, whereas the bulk maltene represents a mixture of diversified organisms. By comparing the offset between δ13Corg, δ13Cmaltene and δ13Ckerogen in the T-OAE interval, two phases separated by the nadir of δ13C were recognized: early N-CIE and late N-CIE. In general, Phanerozoic δ13C values for preserved maltene and bulk organic matter in sediments are equal to or more negative than syngenetic kerogen; in the early N-CIE, however, δ13Ckerogen is more negative than δ13Cmaltene. Such isotopic inversions were previously attributed to the proliferation of 13C-enriched cyanobacteria and heterotrophic bacteria, which have been reported in Precambrian and Permo-Triassic transitional records. Moreover, the corresponding low sterane/hopane values in early N-CIE indicate an ecological shift reflecting microbial response to catastrophic environmental change that caused the extinction and initiated ecosystem changes during the early stage of T-OAE.

A Review on the Durability of Recycled Asphalt Mixtures Embraced with Rejuvenators

Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to predict future challenges in rejuvenating aged asphalt.

New evidence on the origin of ‘bee structures’ on bitumen and oils, by atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM)

Bitumen is a complex mixture whose composition–structure-property relationships are not well-understood. Therefore, it is essential to understand which components may develop microstructures, how and when these features appear, and if they are initiated or influenced by other components. Many studies have reported so-called bee structures as well as other phases on bitumen surfaces. A large number of observations point towards the crystallinity of waxy compounds as an explanation for the bees. However, doubt remains about the origin of the other phases and the possibility of other bitumen components as promoters of the bee formation. In this study, bee structures were investigated using two microscopy techniques: atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). By using model wax compounds, especially blends of waxes differing in melting points and chain lengths, bee structures and surrounding islands were created on featureless bitumen surfaces. Structures very similar to what is observed on a paraffinic bitumen were obtained. This indicates that bees and the surrounding areas both consist of crystallisable components. Moreover, bee structures were also generated on other surfaces, such as mineral oil and a maltene fraction. Bee formation is not limited to bituminous materials and bitumen components are not needed as promotors. Furthermore, CLSM offers possibilities to scan through transparent layers and to investigate surfaces under glass, for example. In contact with such a solid substrate, as well as after water submersion, no microstructural features were observed. Adding a combination of n-alkanes, to transparent oil, induced bee structures at the oil-air interface. The transparency of the oil allowed the visualization of wax crystallization in the bulk, where the added waxes crystallize as small particles. These small crystals are expected to influence the mechanical properties, such as low-temperature stiffening effects, which have been reported for paraffinic bitumen.

Treatment of petroleum refinery sludge by petroleum degrading bacterium Stenotrophomonas pavanii IRB19 as an efficient novel technology

Petroleum hydrocarbons (PHCs) in petroleum refinery sludge (PRS) are the most adverse components because of their toxic nature, which are harmful to human health and the aquatic ecosystem. This study aimed to identify and characterize an indigenous bacterium isolated from PRS of Indian oil corporation ltd. (IOCL), Haldia, India, and evaluate its performance for biodegradation of total petroleum hydrocarbon (TPH) of PRS. The bacterium molecularly characterized as Stenotrophomonas sp. IRB19 by 16S rRNA sequencing and phylogenetic analysis. The strain IRB19 showed a significant ability to utilize four different oils (kerosene, diesel, petrol and hexadecane) in-vitro. IRB19 could able to degrade up to 65 ± 2.4% of TPH in 28 d of incubation. Solvent extraction study showed that PRS contain 180.57 ± 3.44 g kg−1 of TPH and maltene fraction composed of aliphatic, aromatics and polar components of 52 ± 4, 39 ± 2 and 9 ± 1%, respectively. The TPH degradation best fitted for the Gompertz model and followed the first-order kinetics having the rate constant (k) and half-life period (t 1/2) of 0.036 d−1 and 19 d, respectively. Results of this study verified the suitability of the novel strain IRB19 for the biodegradation of PHCs.

Modified bituminous binders for road construction in the Republic of Sakha (Yakutia)

Take into the account climate and environmental conditions of this region are necessary during modern road construction technologies introduction in the Republic of Sakha (Yakutia). This region’s climate and environmental conditions in many ways are identified as extreme. First of all, it should be noted that Yakutia is the coldest region of the Russian Federation, its territory is completely located in the permafrost zone. At the constructional materials testing center of the Pacific National University, were executed experimental studies to develop technological regulations for the modified bituminous binder manufacturing intended for paving the Lena highway (Yakutsk – Never). In this work, for the polymer-bitumen binder manufacturing, was used bitumen petroleum viscous for road building, grade BND 130/200. In the course of the research, the polymer-bitumen binders PBV 200 and PBV 300 with a brittle temperature not exceeding -35 °C and -40 °C with the thermoplastic elastomers SBS LG 502 (South Korea) and SBS R 30-00A (JSC «Voronezhsintezkauchuk») additives use the formula selecting problem were solved, as well as plasticizer – industrial oil I-40A. To optimize the composition of the binder and further improve its characteristics, it is proposed to use bitumen with increased content of maltene fractions and to include in its composition an adhesion additive of the amphoteric type DAD-1. The resulting polymer-bitumen binder is characterized by a wide performance range – an increased softening temperature and a low brittleness temperature, elasticity (ability to reversible deformations), high adhesion to various rocks. Achieving these goals will improve the asphalt concrete pavement quality and durability in difficult climatic conditions.

Comparison of molecular properties of saturate and aromatic fractions of Turkish and Iraqi crude oil residues

The chemical characterization of crude oil fractions is important for the petroleum research and complex structure of crude oil residue keeps studies ongoing. An analytical method which gives the composition of residue is not available yet and a combination of facile methods that elucidates the structure of residue is the most important in the petroleum research.This work reveals the detailed analyses of saturate and aromatic fractions of the selected crude oil atmospheric residues (ARs). Molecular structure of the saturate and the aromatic fractions was investigated by a combination of High-Performance Liquid Chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy techniques. In this study, saturate and aromatic fractions were physically divided into sub-fractions by HPLC and sub-fractions were examined in depth according to the hydrogen type using 1H NMR. Moreover, AR maltenes and their saturates were analyzed by High Temperature-Simulated Distillation (HT-SIMDIS), in order to deduce carbon number (CN) ranges of the AR distillation cut points in weight percentages. The study revealed the distribution of aliphatic and aromatic hydrogen types in sub-fractions of the saturates and the aromatics of the selected ARs. Mono, di- and tri-aromatic hydrogen types of each sub-fraction were also disclosed. For all sub-fractions, total aromaticity increases in the order of increasing elution sequence. Celikli AR maltene fraction has molecules that have CN in the range of 14–30 or less for half of its total weight and contains mostly low boiling structures.

Rheology-morphology relationships of new polymer-modified bitumen based on thermoplastic polyurethanes (TPU)

The present study reports a new type of polymer-modified bitumen (PMB) which considers the use of a thermoplastic polyurethane (TPU) as an alternative to conventional thermoplastic elastomers such as poly(styrene-b-butadiene-b-styrene) block copolymers. As for other block copolymers, the structure of the TPU, made of two types of segments which can microphase-separate, leads to its selective swelling by the oily fractions of bitumen. The poor compatibility of hard segments (HS) with bitumen is responsible for this partial swelling of the TPU by the maltene fractions. By varying the TPU content in the bitumen-TPU blend a dramatic change in viscoelastic properties for a TPU content close to 11 wt% is shown, with the appearance at high temperatures of an elastic response due to the percolation of the TPU-rich phase. This percolation phenomenon is highlighted by multiscale morphology characterizations and well described by a conventional mechanical percolation model. Different TPU architectures, i.e. different hard to soft segments ratios, are studied. The best compromise is found for a blend containing TPU with 13 wt% of HS as it displays a favorable swelling of percolated TPU rich phase while maintaining its viscoelastic behavior.

Fourier transform ion cyclotron resonance mass spectrometric analysis of NSO-compounds generated in hydrothermally altered sediments from the Escanaba Trough, northeastern Pacific Ocean

To date little is known about the functionalized and heteroatomic compounds present in hydrothermal petroleum and how these compounds are affected by high temperature vent fluids. To address this, the maltene fractions of three hydrothermal petroleum samples spanning the shallow depth of a sediment core collected in the Escanaba Trough of the Gorda Ridge in the northeast Pacific were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in both negative electrospray ionization (ESI) and negative atmospheric pressure photoionization (APPI) ionization modes. These polar compounds were structurally similar to asphaltenes, but did not exceed a nominal mass range of ∼800 Da. They were derived primarily from terrestrially sourced organic matter (OM) with common heteroatom arrangements of CaHbOc, CaHbOcNd, CaHbNd, CaHbOcSe, CaHbOcNdSe, CaHbNdSe, and CaHbSe. The samples included compounds containing up to 19 oxygen heteroatoms and ranged in size from 10 to 53 carbon atoms with double bond equivalent (DBE) values of 1–38. Molecular formulae with N and S heteroatoms were minor. Within this sulfidic environment the formation and preservation of sulfur heterocyclic compounds was very low, which could be due to sulfurization being out-competed by the high concentrations of metals in the vent fluids or as a result of the thermal instability of C–S bonds. The dominance of oxygenated, and not thiolated, compounds was primarily source-dependent with secondary alteration by aromatization in this system proceeding by H abstraction and reduction of sulfate to H2S. We identified differences in the distributions of heteroatomic compounds caused by the expulsion, thermochemical oxidation, and differentiation of petroleum products during the migration of fluids to the sediment–water interface.

Mechanism behind the paper spray chemical ionization phenomenon and the choice of solvent.

Paper spray chemical ionization (PSCI) combined with mass spectrometry has been proposed as a sensitive method for the analysis of nonpolar aromatic compounds; however, the mechanism behind PSCI is not well understood. In the present study, the evidence for the occurrence of corona discharge is provided and its mechanism is proposed. Photographs taken with a highly sensitive camera evidently demonstrate the occurrence of corona discharge at the end of the triangular shape tip when a nonpolar solvent such as hexane was used at an applied potential of 6-7 kV. Nevertheless, corona discharge was not observed in the presence of a polar solvent. The occurrence of the corona discharge was attributed to charge accumulation in the dielectric layer generated by the nonpolar solvent on the fibers of the paper tip. Specifically, corona discharge was generated at the tip end when the charge approached a critical threshold. In the presence of a polar solvent, however, the dielectric layer was not generated and, hence, corona discharge was not observed. Based on this information, three nonpolar solvents were selected and their sensitivity for analyzing the phenanthrene and maltene fractions of crude oil was evaluated. Chlorobenzene provided the highest signal abundance; therefore, it was suggested as the optimum solvent for PSCI. Notably, the fundamental understanding of corona discharge in PSCI acquired in this study provides a basis for further improvement of this technique by way of surface modification.