Characterization Of Asphaltenes Research Articles

Structure Elucidation and Sulfur Species Characterization of Asphaltenes Derived from Heavy Fuel Oil Using APPI (+) and ESI (+) FT-ICR Mass Spectrometry

Structure Elucidation and Sulfur Species Characterization of Asphaltenes Derived from Heavy Fuel Oil Using APPI (+) and ESI (+) FT-ICR Mass Spectrometry

Analytical investigation of asphaltene cracking due to microwave and ultrasonic radiations: A molecular insight into asphaltene characterization and rheology

Asphaltene is a fraction of crude oil that causes technical and environmental problems because of its instability and precipitation. Microwave and ultrasonic radiations have been proven to be efficient for oil viscosity reduction and removal of asphaltene precipitants. This research aims to investigate the alteration of the asphaltene molecular structure from a molecular point of view, as well as their rheological behavior, due to microwave and ultrasonic radiations. Nuclear Magnetic Resonance (NMR), Fourier Transformed Infrared (FTIR), Energy Dispersive X-ray (EDX) spectroscopies, and Elemental analysis were implemented to find the ultrasonic and microwave radiation effects on the molecular structure of two asphaltene samples. Based on the obtained results, the number of fused aromatic rings is reduced due to ultrasonic and microwave radiations, indicating aromatic core cracking. The number of aliphatic carbons is reduced, representing the aliphatic chain cracking. Besides, the increase in the aliphatic chain length, aside from aromatic core cracking, was a sign of the ring opening. The reduction of the polar groups, such as carbonyl, in the microwave-treated asphaltene, was explained by more vulnerability of materials with higher dielectric constants to the microwave. The ultrasonic radiation was more feasible for removing heavier elements, such as oxygen. The aggregation behavior of the untreated/treated asphaltenes was investigated through rheological tests. The viscosity of the oil sample bearing treated asphaltene was lower than the ones bearing crude asphaltene, representing reducing the ability for aggregation. Based on the structural parameters and chemistry of the treated asphaltenes, weakening of hydrogen bonding interaction and π- π stacking were recommended mechanisms for reducing asphaltene aggregation and oil viscosity. This research could be used to modify the asphaltene structure to hinder the technical and environmental issues, caused by the asphaltene precipitations.

Structural characterization of asphaltenes enriched in Island and archipelago motifs by LDI ( +) FT-ICR MS

Structural characterization of asphaltenes enriched in Island and archipelago motifs by LDI ( +) FT-ICR MS

Screening and Investigation on Inhibition of Sediment Formation in a Kuwait Light Crude Oil by Commercial Additives with Some Guidelines for Field Applications

The precipitation of asphaltene and waxes occurs when crude oil characteristics change as a consequence of pressure, temperature variations, and/or chemical modifications, etc. The costs associated with the cleaning of deposition on the production equipment and the loss of profit opportunities can go beyond hundreds of millions of USD. Thus, there is a strong incentive to search for ways to mitigate deposit formation during the crude production process. A light crude bottom hole fluid sample from a deep well with an asphaltene deposition problem was analyzed in the laboratory. Basic data on density, viscosity, bubble point, GOR, and asphaltene onset pressure were measured at a PVT laboratory. Asphaltene characterization, as a prescreening for appropriate inhibitors, has been conducted using asphaltene phase diagrams (APD). The APD generated from two developed software programs in both Matlab and Excel codes were favorably compared with the phase behavior of other oil samples available in the literature and has shown to be an excellent match. Various test methods were used to demonstrate the asphaltene instability of the oil samples. Eleven chemical inhibitors from five global companies were screened for testing to inhibit the precipitation. The optimum concentration and the amount of reduction in precipitation were determined for all of these chemicals to identify the most suitable chemicals. Finally, some recommendations are given for the field application of chemicals.

Experimental measurement and modeling of asphaltene adsorption onto iron oxide and lime nanoparticles in the presence and absence of water

Asphaltene precipitation and its adsorption on different surfaces are challenging topics in the upstream and downstream of the oil industries and the environment. In this research, the phenomenon of asphaltenes adsorption in the presence and absence of water on the surface of magnetite, hematite, calcite, and dolomite nanoparticles (NPs) was investigated. Five asphaltenes of different origins, four NPs as adsorbents and Persian Gulf water were used for three-phase (asphaltene/toluene solution + NPs + water) experiments. Characterization of asphaltenes and NPs was performed using Fourier transform infrared spectroscopic (FTIR), dynamic light scattering (DLS), elemental analysis, and field emission scanning electron microscopy (FESEM). Adsorption experiments were performed in two- (asphaltene/toluene solution + NPs) and three-phase systems. The results showed that the most effective parameters for asphaltene adsorption onto these NPs are the asphaltene composition, namely nitrogen content, and the aromaticity of asphaltenes. The significant effects of these parameters were also confirmed by the relevancy factor function as a sensitivity analysis. In the competition of asphaltene adsorption capacity by NPs, iron oxide NPs had the highest adsorption (Magnetite NPs > Hematite NPs > Calcite NPs > Dolomite NPs). From the results of the experiments in the presence of water phase, it could be pointed out that the asphaltenes adsorption onto the NPs was accompanied by a decrease compared to the experiments in the absence of water. The modeling also showed that physical adsorption has a significant contribution to the asphaltenes adsorption on the surface of iron oxides and lime NPs. The results of this research can assist in a better understanding of the asphaltene adsorption phenomenon and the role of iron oxide and lime NPs in solving this problem.

Molecular Structure: The First and Most Significant Factor in the Precipitation of Asphaltenes

SummaryFor decades, asphaltene deposits have been one of the most common problems in the oil industry in production, transportation, refining, processes, and storage. To find a solution, researchers have always faced three intertwined challenges of accurate structure determination, properties investigation, and precipitation prediction because asphaltenes in one oil sample are “a spectrum of complex molecular structures with very close masses.” Various models and theories of the inherent self-association of asphaltenes have been presented. All of them confirm the role of the unique molecular structure of asphaltenes as “the initiator” of the precipitation process. The driving factor for self-association is π-π stacking of aromatic rings. Recent advances in molecular dynamics (MD) calculations confirm the results of recent models. After the molecular structure, thermodynamic parameters (P, T, and composition) are the influencing agents on precipitation. Any change in these parameters causes an increase or decrease in the intensity of the precipitation. Due to the greater importance of molecular structure over other parameters, until the great challenge of characterization of asphaltenes is not specific, the validation of sediment prediction models will undoubtedly be accompanied by errors. In this paper, we review essential types of asphaltene self-association models and precipitation prediction methods. As an introduction and emphasis on the understanding of this inherent phenomenon, the weight, molecular structures, analysis methods, and ambiguities are investigated.

Investigating the Influence of n-Heptane versus n-Nonane upon the Extraction of Asphaltenes.

The composition of asphaltenes is of interest due to the challenges they pose for industry and their high complexity, encompassing a range of heteroatom contents, molecular weights, double bond equivalents (DBEs), and structural motifs. They are well-known for aggregating above critical concentrations, hindering the upstream and downstream processes. Asphaltenes are defined by solubility, as they are insoluble in light paraffins such as n-heptane and soluble in aromatic solvents such as toluene. Today, enormous efforts are being invested into the characterization of asphaltenes to shed light into their structural profiles to benefit the petroleum industry and environmental sustainability. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides molecular level analysis with unparalleled mass resolving power and mass accuracy, which is vital for the characterization of inherently complex crude oils and their asphaltene fractions. The aim of this research is to elucidate and compare the compositional profiles of asphaltene fractions of two petroleum samples, fractioned through two approaches: using n-heptane, as is typical practice, and n-nonane, for the purpose of testing extraction using higher molecular weight alkanes. The results highlight that the choice of solvents does indeed influence the accessibility of different species and therefore changes the observed molecular profiles of the extracted asphaltenes. n-Heptane afforded broader contributions of different heteroatomic classes and greater carbon number ranges of the observed components; the DBE distribution vs carbon number profiles were different, where the extracts produced using n-nonane displayed a greater prevalence of lower DBE species.

Laser desorption ionization and collision induced dissociastion as powerful tools for FT-ICR mass spectrometric characterization of asphaltene fractions enriched in island and archipelago motifs

Due to advances in mass spectrometry, it is widely accepted that asphaltenes molecules from the island and archipelago motifs coexist in the samples. However, analyzing asphaltenes remains a challenging task mostly due to these species' high complexity and self-association tendencies. Herein we introduce laser laser desorption ionization (LDI) as an adequate tool to ionize even the most unstable samples. In addition, we demonstrate collision-induced dissociation (CID) experiments as a powerful tool to perform structural characterization of asphaltenes. Using these tools, it was possible to characterize asphaltene samples enriched in island and archipelago-type structures in a much easier way without any capillary obstructions and damages to the equipment. Also, it was possible to perform an in-depth analysis of asphaltene and propose structures to asphaltene detected in the most abundance in the selected samples. Finally, the relative percentages of product ions derived from the cleavage of alkyl bridges between aromatic nuclei in archipelago-type molecules were calculated, and we tried to establish correlations with the asphaltene structures with their stability.

The Impact of Carbonated Water on Wettability: Combined Experimental and Molecular Simulation Approach

Summary Carbonated water injection has gained wide interest as an enhanced oil recovery technique. The efficiency of oil displacement during an ordinary waterflood is dictated and governed mainly by the viscous and capillary forces between oil and water. These forces are controlled by the interfacial tension (IFT) between the fluids and the contact angle (CA) with the rock surface. In this study, the pendant drop technique and molecular dynamics (MD) simulation were combined to investigate the effect of adding carbon dioxide on the water/oil/rock interfaces. CA measurement is rather a macroscopic assessment of the wettability while molecular simulation can provide further microscopic insights. The multiscale approach involves direct wettability assessment of asphaltene-containing oil against pure water or carbonated water, both exposed to two types of carbonate rock samples. Molecular characterization of asphaltenes was carried out by analytical means and different asphaltene structures were recreated on a computational platform for asphaltene-water and asphaltene-carbonated water molecular simulations. The experimental data revealed that the carbonated water caused the CA to change from weakly oil-wet to intermediate to water-wet wettability. Molecular simulation was invoked to shed more light into the underlying mechanisms behind the observed wettability alteration. In particular, molecular simulation of IFT and asphaltene swelling effect driven by the interactions with carbon dioxide were analyzed. The results were found consistent with the experiments. The findings presented in this paper highlight the viability of carbonated water for enhanced oil recovery and provide in-depth insights into the underlying mechanisms.

Ultrahigh-Resolution Magnetic Resonance Mass Spectrometry Characterization of Asphaltenes Obtained in the Presence of Minerals

Ultrahigh-Resolution Magnetic Resonance Mass Spectrometry Characterization of Asphaltenes Obtained in the Presence of Minerals

Lab-on-a-Chip Systems in Asphaltene Characterization: A Review of Recent Advances

Lab-on-a-Chip Systems in Asphaltene Characterization: A Review of Recent Advances

A new insight to the assessment of asphaltene characterization by using fortier transformed infrared spectroscopy

This research aims to present asphaltene fraction of oil by FTIR spectrum technique. For this purpose, three different oil samples with various SARA contents and almost identical API degrees were utilized in this research. Two asphaltenic oil samples were referred to as ‘A’ and ‘B’, and the aliphatic oil sample was named as ‘C’. First of all, the asphaltene fraction was extracted through the IP-143 test. The possible chemical bonds and functional groups were identified through NMR tests. Then, the FTIR spectrums of the oil samples and the extracted corresponding asphaltene fractions were taken. The interpretations were used to find the functional groups in the FTIR of the oil samples that belong to the asphaltene fractions. Among the investigated oil samples, no asphaltene related peak with a unique assignment was observed for the FTIR for sample ‘A’. The FTIR of oil sample ‘C’ showed amine related peaks, which belonged to the asphaltene fraction. Also, the alcohol and amine related peaks, which correspond to the asphaltene fraction, were detected in the FTIR of the oil sample ‘B’. According to the oil samples' SARA contents, the ratio of the asphaltene content to the aromatic-based fraction seems to have a key role in this method. In other words, to detect the functional groups attached to the asphaltene fraction from the FTIR spectrum, the asphaltene fraction should have enough concentration compared to other aromatic-based components in the oil. The method's applicability is initially based on the specific functional groups existence in the asphaltene fraction. • A functional group in oil that is found in the asphaltene can be used to trace the asphaltene content changes. • Tracing asphaltene content of the oil by using the FTIR spectrum could not be performed in all of the oil samples. • The ratio of the asphaltene content to the aromatic-based fraction seems to have a key role in this method.

Investigation of Island/Single-Core- and Archipelago/Multicore-Enriched Asphaltenes and Their Solubility Fractions by Thermal Analysis Coupled with High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Despite extensive research, the molecular-level chemical characterization of asphaltenes, a highly aromatic solubility fraction of petroleum, remains an analytical challenge. This fraction is relat...

Understanding Asphaltene Fraction Behavior through Combined Quartz Crystal Resonator Sensor, FT-ICR MS, GPC ICP HR-MS, and AFM Characterization. Part I: Extrography Fractionations

Multiscale characterization of asphaltenes and their extrography fractions titrated with n-heptane was performed. Chemical characterization via FT-ICR MS and GPC ICP HR-MS, stability monitoring via QCR, and AFM images of deposits indicate that “island”-enriched samples tend to form fewer, well-organized deposit aggregates, whereas samples with abundant “archipelago”-like molecules produce larger aggregates and less well-organized deposits. The combination of QCR and AFM leads to the conclusion that “island”-enriched samples lead to smaller deposits compared to “archipelago”-like molecules.

Detailed FTIR spectroscopy characterization of crude oil extracted asphaltenes: Curve resolve of overlapping bands

In recent years, characterization of asphaltenes as an appropriate way to deal with their related problems in the oil industry has been received considerable attention. The Fourier-transform infrared (FTIR) analysis, since its appearance in the 1880s, become one of the most applicable techniques to gain the valuable information about characteristics and functional groups of different samples especially petroleum related materials (e.g. asphaltenes). Despite these advantages, this technique suffers from a severe drawback especially in analyzing complex compounds such as asphaltenes. This problem is defined as overlapping related to the functional groups with the near occurrence bands which can hinder thorough qualitative and quantitative analyzing. A considerable number of studies were dedicated to FTIR analysis of asphaltenes, but the curve resolving of petroleum asphaltenes spectra has not yet been extensively studied. In this paper, four asphaltenes extracted from crude oils were analyzed by FTIR and then these spectra were completely resolved. The results, for the first time, provide a deep insight into the functional groups present in asphaltenes and their attaching substitutions. The comprehensive investigation of bands shifting and the relationship of their band area with elemental results reveal that carboxylic acids are linked to both saturate (band at about 1743 cm−1) and aromatic compounds (band at about 1698 cm−1); however, esters and alcohols (e.g., secondary and tertiary alcohols) are attached to saturated compounds in the studied asphaltenes (band at 1743 cm−1 for saturated esters and bands at 1347, 1160 and 1110 cm−1 for saturated alcohols). Ketones occur as diaryl and mixed (1616 and 1685 cm−1 bands), but ethers appear as alkyl/aryl (1018 cm−1). The sulfoxide (1033 cm−1), secondary amides (bands at 3239, 1649, 1575 and 1310 cm−1), polyaromatic (with different substitutions at region below 900 cm−1), phenols (3430 and 1229 cm−1) and aliphatic compounds (such as methyl, methylene, and methine in the 1460 and 1375 cm−1 bands and in the 3850-3000 cm−1 region) are also present in the studied asphaltenes.

Molecular Structure and Solubility Determination of Asphaltenes

Due to their complex chemical structure, identification and characterization of asphaltenes remain a big challenge for researchers in the oil industry. In the current contribution, solution-state t...

Speciation of Metals in Asphaltenes by High-Performance Thin-Layer Chromatography and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry

Asphaltenes are considered to be the most problematic components of heavy oils because they can self-aggregate which leads to precipitation and causes various problems during oil recovery, transportation, and refining. The contribution of the porphyrins present in asphaltenes to the aggregation was previously studied by gel permeation chromatography inductively coupled plasma-mass spectrometry (GPC-ICP MS). The molecular weight of asphaltene aggregates was shown to be increased by free metal-containing porphyrins (corresponding to the lower molecular weight fraction) interacting with the aggregate’s surfaces by weak forces. The characterization of free porphyrins within the asphaltenes is therefore for the understanding of the mechanism of the aggregation, coprecipitation, and demetalation processes. Here, we developed a method for the separation of free porphyrins from asphaltenes on the basis of their polarity using high-performance thin-layer chromatography (HPTLC). This technique, using disposable plates, is particularly well suited for asphaltene analysis since it eliminates the risk of clogging typical of column chromatography. Cellulose plates were used in this study. The lower polarity of their hydroxyl groups limit the irreversible adsorption and improves the detection limit by the ICP-MS. Two well-separated peaks were obtained from purified asphaltene (Asphaltene 2017; Asphaltene Characterization Interlaboratory Study for PetroPhase 2017. In Proceedings of the 18th International Conference on Pretroleum Phase Behavior and Fouling, Le Havre, France, June 11–15, 2017; Total, the University of Pau, and the University of Rouen-Normandy: Le Havre, France, 2017.) and its corresponding whole crude oil and C5 and C7 fractions. The distribution of vanadium due to migration was determined by laser ablation (LA) ICP MS. The eluted fraction contained the free porphyrins, whereas the major fraction did not migrate and corresponded to trapped porphyrins. A comparison with the signal obtained by UV densitometry allowed the ratio between the inorganic and organic material to be measured.

Multifrequency (9 and 95 GHz) EPR study of stable radicals in asphaltenes fractions of oils and bitumen

Structural characterization of asphaltenes in complex systems such as native hydrocarbons is in the focus of scientific and industrial interests since many years. Various analytical tools and approaches are used for that. We present the results of our study of asphaltene fractions A1 and A2 with the predominantly “island” type and “archipelago” type asphaltene molecules by conventional and pulsed electron paramagnetic resonance (EPR) at X-band (9 GHz) and W-band (95 GHz) with aim to expand the abilities of EPR technique for asphaltene characterization. Shift to the higher frequencies allows to separate spectrally the contributions from paramagnetic complexes of different origin, define the EPR parameters more accurately comparing to the conventional X-band EPR. Application of pulsed techniques allows (at least partially) to separate the radicals in time domain. Features of the obtained spectra are described. Electronic relaxation times are found to be different for stable “free” radical for A1 and A2 fractions. We suggest that the obtained results can be used for investigation of various petroleum systems.

Distribution of vanadyl complexes and free radicals in asphaltenes fractions from electron paramagnetic resonance

Structural characterization of asphaltenes in complex systems is in the focus of scientific and industrial interests since many years. Asphaltenes isolated from the high-viscous Ashal’cha oil (2500 mPa·s) were studied. Five asphaltene fractions were obtained by stepwise extraction with an alcohol-benzene solvent with different alcohol contents after precipitating the asphaltenes from the oil with hot isooctane. Redistribution of paramagnetic centers between the fractions of asphaltenes is revealed by electron paramagentic resonance (EPR) while no significant changes in EPR spectral parameters are found. The results can be used for tracking the asphatenes formation as well as following the changes of their supramolecular structure.

Molecular-Level Characterization of Asphaltenes Isolated from Distillation Cuts

Asphaltenes challenge nearly all analytical techniques because of their immense polydispersity in molecular composition and structure. This operationally defined fraction of crude oil, insoluble in n-alkanes but soluble in aromatic solvents, is known to concentrate in vacuum residues and islinked to fouling and deposition issues. However, presence and subsequent characterization of asphaltenes are seldom discussed in conventional/unconventional distillate fractions. Here, we isolate asphaltenes from conventional ( 593 °C) distillation cuts and provide molecular-level characterization by electrospray ionization and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry as a function of boiling point. Our results indicate that asphaltene molecular composition starts in the vacuum gas oil range and extends into vacuum residues. Moreover, we report that distillable asphaltene composition exists as both highly polar (heteroatom rich)...