Asphaltene Fractions Research Articles

Thermodynamic and Experimental Substantiation of the Possibility of Formation and Extraction of Organometallic Compounds as Indicators of Deep Naphthogenesis

In this article, typomorphic associations of microelements in carbonaceous caustobioliths and oils are defined as indicators of naphthogenesis based on the analytical survey of the literature and our own research. Various approaches to the studying of crude oil genesis from the position of abiotic and complex approaches (polygenesis) are considered. Such approaches are relevant to the prospect and development of offshore oil deposits, localized at ultra-deep levels. For deep deposits, the most prominent hypothesis of oil origin is the abiogenious theory. In the foundation of that approach lays the assumption that hydrocarbons are formed mainly due to reactions of the formed mantle gases and the host rock. Key factors for these reactions to proceed are specific conditions concerning temperature, pressure, and specific catalysts. The article presents the results of thermodynamic and quantum-chemical modeling of the possibility of the organic and organometallic compound formation using the software package HSC Chemistry 6.0. Pointed out the possibility of a low molecular weight hydrocarbon formation due to the contact of ascending flows of mantle gases with cooling natural barriers. The primary synthesis proceeds with the interaction of fluid forms of H2, CO2, and H2S. The estimation of the bonding energy depending on the structure of organometallic compounds was performed using the Avogadro software package. The program used the method of bond potential energy minimization to find the most stable structure of molecules. The metals nickel and vanadium, as the main companion metals of oil, are of the most interest from the position of analysis of their form of existence in the possible formation of hydrocarbons. Vanadium’s and nickel’s accumulation in asphaltene fractions of oils, probably, is caused by complex compounds of metalloporphyrin’s formation. In addition, the high sulfur content is probably associated with polymerization of organic molecules due to the formation of di-sulphide bonds. The method of cavitation extraction of organometallic compounds from oil and complex mineral–oil raw materials has been developed for experimental confirmation of microelements the extraction capability from oil raw materials.

Changes in structural parameters of SARA fractions during heavy oil hydrocracking using dispersed catalysts

Most of the characterization of SARA fractions of heavy crude oils during hydrocracking reactions is focused only on asphaltenes, and scarce works are devoted to analyze the differences in the structural parameters of all SARA fractions. In this work, a heavy crude oil is upgraded by non-catalytic and catalytic hydrocracking in a batch reactor at low severity conditions (3.9 MPa H2 pressure, 380 °C temperature, 800 rpm stirring rate, and 4 h reaction time). Three ore catalysts (hematite, magnetite and molybdenite) and one analytical grade catalyst (iron oxide) are employed. After reaction, the upgraded oils are first distilled and then separated into SARA fractions by the ASTM D86-16a and ASTM D2007-11 methods, respectively. NMR (1H and 13C), FTIR and GPC analyses are used to characterize SARA fractions before and after hydrocracking. The hydrocracking products exhibited a reduction in the average molecular weight of all SARA fractions as function of the hydrogenation capacity of each catalyst in the following order: Fe2O3 (analytical grade) > Molybdenite > Hematite > Magnetite. The structural parameters of saturates fraction remains unchanged except for the production of small length aliphatic chains from heavier fractions. For aromatics, resins and asphaltenes fractions, the number of aliphatic carbons is reduced due to dealkylation reactions increasing their aromaticity. For resins and asphaltenes fractions, hydrogenation and ring opening reactions are also carried out. Mo-based catalyst is mainly aimed at the conversion of asphaltenes, while the Fe-based catalysts focused on the conversion of resins.

COMPOSITION OF THERMAL CRACKING PRODUCTS OF SARA FRACTIONS FROM HEAVY METHANE CRUDE OIL

Changes in the composition of SARA fractions (Saturated, Aromatics, Resins, Asphaltenes) of methane crude oil from the Zyuzeevo oilfield (the Republic of Tatarstan) during thermal cracking are investigated. Cracking was carried out at 450 °C for 120 min in the isothermal mode. The data on mass balance, the composition of liquid and gaseous products of cracking were obtained. It is shown that the composition of hydrocarbons in liquid products and the yield of gaseous and solid by-products depend on the composition of initial SARA fractions. Thus, the yield of solids is maximal from asphaltene fraction cracking, while the largest amount of gases are formed from resin fraction cracking. It has been established that cracking of SARA fractions involves the formation of new components that were absent in the initial feedstock. It is shown that the structural features of initial resin and asphaltene molecules affect the content and composition of their cracking products.

Influence of moisture on the migration of asphalt components and the adhesion between asphalt binder and aggregate

The performance degradation of asphalt pavement by moisture intrusion has been widely concerned. This paper investigated the effect of moisture on asphalt fractions and interface failure mechanism by moisture-induced using inclined shear test. Fourier transform infrared spectroscopy (FTIR) showed reduction of asphalt aromaticity by moisture led to the decline of asphalt cohesion. Fluorescence microscopy (FM) images indicated humid environment aggravated degradation of polymer particles in modified asphalt. Failure surface analysis confirmed moisture damage extended from asphalt to asphalt-aggregate interface. Although moisture enhanced the polarity of asphalt, moisture intrusion into the interface seriously weakened adhesion capability of asphalt and aggregate.

SAR-AD Method to Characterize Eight SARA Fractions in Various Vacuum Residues and Follow Their Transformations Occurring during Hydrocracking and Pyrolysis

Model compounds were used to provide some chemical boundaries for the eight-fraction SAR-ADTM characterization method for heavy oils. It was found that the Saturates fraction consists of linear and highly cyclic alkanes; the Aro-1 fraction consists of molecules with a single aromatic ring; the Aro-2 fraction consists of mostly 2 and 3-ring fused aromatic molecules, the pericondensed 4-ring molecule pyrene, and molecules with 3–5 rings that are not fused; and the Aro-3 fraction consists of 4-membered linear and catacondensed aromatics, larger pericondensed aromatics, and large polycyclic aromatic hydrocarbons. The Resins fraction consists of mostly fused aromatic ring systems containing polar functional groups and metallated polar vanadium oxide porphyrin compounds, and the Asphaltene fraction consists of both island- and archipelago-type structures with a broad range of molecular weight variation, aromaticity, and heteroatom contents. The behavior of the eight SAR-ADTM fractions during hydrocracking and pyrolysis was investigated, and quantitative relations were established. Intercriteria analysis and evaluation of SAR-ADTM data of hydrocracked vacuum residue and sediment formation rate in commercial ebullated bed vacuum residue hydrocracking were performed. It showed that total asphaltene content, toluene-soluble asphaltenes, and colloidal instability index contribute to sediment formation, while Resins and Cyclohexane-soluble asphaltenes had no statistically meaningful relation to sediment formation for the studied range of operation conditions.

Analysis of the interfacial tension of cationic imidazolium-based ionic liquid, twin-branched tailed anionic surfactant, and a non-ionic emulsifier in the presence of SiO2 nanoparticle and amphiphilic oleic components using response surface method

Although various surface active agents have been proposed, there is still no straightforward and clear understanding of the effect of cationic imidazolium-based ionic liquid (IL), twin-branched tailed anionic surfactant, and a non-ionic emulsifier in the presence of SiO2 nanoparticle and amphiphilic oleic components on the interfacial tension (IFT) reduction. So, in this work, the performance of cationic imidazolium-based IL ([C12mim][Cl], anionic surfactant (AOT)), and non-ionic surfactant (Tween 80) on the IFT value were studied through the design of experiment approach and the response surface method. Experiments were designed using a face-centered composite design (FCCD) with the independent variables of surfactant concentration (175–525 ppm) and nanoparticle concentration (25–75 ppm) as numerical ones, and surfactant type and synthetic oil (8 wt% of asphaltene and resin fractions dissolved in heptol (mixture of n-heptane: toluene with the volume ratio of 30:70)) with various volume ratios of asphaltene to resin (1:0, 2:1, 1:1, and 1:2) as categorical ones. According to the analysis of variance (ANOVA) and 156 measured IFT experimental data points, the effects of each factor were evaluated. As a result, the suggested quadratic model with R2 (0.9986) and adjusted R2 (0.9984) values indicated that the fitted model can accurately predict the response variable (IFT) values. The best performance (lower IFT and critical micelle concentration) was obtained for [C12mim][Cl] without being affected by the amphiphilic nature of asphaltene and resin fractions and the concentration of SiO2 nanoparticles. The appropriate surface activity of IL was attributed to the effective polar head group of imidazolium and the presence of nitrogen in the aromatic ring.

Role of rejuvenator properties in determining the activation effects on aged asphalt based on molecular simulations

Activating the aromatic aggregates by rejuvenators is essential to improve asphalt performance but sufficient understanding is further needed. This study provides a method to evaluate the activation state of aromatic aggregates and the activation effect of rejuvenators on asphalt performance through molecular simulations. Herein, seven types of aromatic aggregation are investigated to obtain representative types by measuring the number of monomers in aggregates at large aggregation determination distances to characterize the aggregates. Solvent accessible surface area is used to examine the aggregates at close distances. Thus, the activation state of aggregates and the effect of rejuvenators are determined. The activation mechanism of rejuvenators on their affinity to aggregates is clarified by radial distribution function (RDF) and interaction energy. Activation efficiency is evaluated by the diffusion coefficient. Viscosity and tensile properties are used to represent asphalt performance. Results show that asphaltenes and resins constitute the aggregate cores, and the aggregation of resins and aromatics determines the expansion of each core. The dispersion and expansion of aggregate cores contribute to forming the aggregation network in the asphalt system, which determines tensile properties and is enhanced by rejuvenators of plasticizer type. A less or weak network resulting from rejuvenators of saturated structures tends to improve the activation efficiency and viscosity. In addition, these activation effects of rejuvenators are determined by their interactions with asphalt fractions as revealed by RDF and energy results.

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.

Rapid and Direct Assessment of Asphalt Volatile Organic Compound Emission Based on Carbon Fiber Ionization Mass Spectrometry.

Due to the complicacy of asphalt fumes, the analytical methods for investigating volatile organic compounds (VOCs) are very limited. In this study, a direct and real-time analysis method based on carbon fiber ionization mass spectrometry (CFI-MS), an ambient mass spectrometric technique, was established and successfully applied in the analysis of asphalt VOCs. The asphalt VOCs can be directly detected in the open atmosphere without the collection step of asphalt fumes, and the mass spectra of one asphalt sample can be obtained in a few seconds in both positive and negative ion modes. By investigating the mass spectral changes of asphalt fumes at different heating temperatures ranging from 50 to 200 °C, the temperature factor of asphalt fume emission was demonstrated in this work. The research results demonstrate that the complexity of asphalt fumes is positively related to the applied temperature. Moreover, the VOCs of saturates, aromatics, resins, and asphaltenes fractions were also analyzed by the direct analysis method. The result shows that aromatics contribute most to the emission of VOCs. In addition, the obtained mass spectra combined with the principal component analysis method show the great potential to quickly screen VOC inhibitors of asphalt materials.

Evaluation of the state of practice asphalt binder and mixture tests for assessing the compatibility of complex asphalt materials

The present study aims to evaluate binder and mixture testing methods for capturing the compatibility of complex asphalt materials consisting of different virgin binder sources, reclaimed asphalt pavement (RAP) materials and recycling agents (RA). Binder evaluation methods include the saturate, aromatic, resin and asphaltene (SARA) fractionation, advanced polymer chromatography (APC) analysis, differential scanning calorimeter (DSC) and rheological measurements. Mixture performance tests include the complex modulus (E*), direct tension cyclic fatigue (DTCF), disk-shaped compact tension (DCT) and semi-circular bending (SCB) fracture tests. The results from the testing and analysis indicate that the rheological characterisation of asphalt binder or mixture may not capture the incompatibility between virgin binder, RAP and RA. Binder DSC analysis as well as mixture fracture tests have shown promise to evaluate the compatibility of complex asphalt materials with different virgin binders, RAP and RA, as well as the effect of incompatibility on mixture performance.

Investigation of asphalt oxidation kinetics aging mechanism using molecular dynamic simulation

Asphalt oxidative aging leads to pavement to become harder and brittle, resulting in the complex cracking and other diseases. However, the microscopic causes of oxidative aging and these changes are not clear. It is meaningful to investigate the complex aging process of asphalt from virgin state to aged state from a microscopic perspective. Molecular dynamics (MD) simulation was used to investigate the oxidation kinetic aging process from the microscopic point of view. Asphalt binders were aged in the oven at five different aging times to simulate the oxidative aging. Saturates, asphaltene, resin, and aromatic (SARA) fraction weights of binders as well as carbonyls and sulfoxides at different aging states were determined using the four fractions separation test and Fourier Transform Infrared Spectroscopy (FTIR). The virgin, fast-rate reaction, constant-rate reaction and full oxidation asphalt molecular models were established corresponded to the proportions of SARA fractions, carbonyl index and sulfoxide index. These models were simulated to investigate the microscopic properties, and the oxidation kinetic aging mechanism of asphalt were revealed.

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.

Chemical and mechanical analysis of field and laboratory aged bitumen

To predict the performance of bituminous products during their service life, an accurate simulation of the aging behaviour is required. Several laboratory methods are available, yet the correlation to field aging is mostly missing. In this study, an unmodified bitumen was exposed to laboratory aging with the Pressure Aging Vessel (PAV) using one to five aging cycles and the Viennese Binder Aging (VBA) method, followed by a comparison to a field sample of the same base binder. Measurements with the dynamic shear rheometer (DSR) and Fourier-transform-infrared (FTIR) spectroscopy showed that the field aging level could not be reached neither with VBA nor with multiple PAV cycles, but a better approximation compared to the standard aging procedure was achieved. The FTIR spectra displayed a high degree of correlation between the VBA and field aged sample, especially regarding carbonyl formation in the aromatic fraction and the intensity of the sulphoxide band in the resin and asphaltene fractions. Additionally, the VBA sample showed more similarities to the field sample regarding fluorescence excitation–emission maps. Although both laboratory aging methods are an improvement to the standard procedure, the VBA method allowed for a better qualitative simulation of the chemical properties of the investigated field sample.

Kinetics of the Thermal Decomposition of Oil Residue and Its SARA Fractions in the Presence of Vegetable Oil

Dynamic thermogravimetry was used to study the thermal degradation of the oil residue of Usinskaya oil and its saturated, aromatic, resin, and asphaltene (SARA) fractions in the presence of sunflower oil. Thermolysis experiments were carried out in an atmosphere of pure argon. Based on the data of thermogravimetric analysis, the activation energies of the thermal degradation of the oil residue, resins, asphaltenes, saturated and aromatic hydrocarbons, and their mixtures with sunflower oil were calculated in the temperature range of a maximum weight loss rate. It was shown that the addition of 10.0 wt % sunflower oil to the oil residue and its components led to a decrease in the activation energy. This fact indicates that the sunflower oil additive affected the mechanism of thermal degradation of crude oil and its components. The greatest change in the activation energy was observed for asphaltenes: ΔЕа = 48.4 kJ/mol.

New insights into effect of the electrostatic properties on the interfacial behavior of asphaltene and resin: An experimental study of molecular structure

Regardless of many attempts to identify asphaltene and resin interfacial phenomena, the complexity of their molecular structure increases the uncertainty about their interfacial behavior. This study aims to examine the effect of physicochemical properties of asphaltenes and resins and the concentration and type of dissolved ions in the aqueous phase on the interfacial interactions. First, the molecular structure parameters of the examined asphaltene and resin were compared using FTIR-ATR and elemental analyses. These results illustrate that the resin molecules rapidly occupy the interface because of the lower relative molecular mass and size. Next, the electrostatic properties of asphaltene and resin molecules were studied via zeta potential and (Isoelectric point) IEP measurements. From the generated laboratory data, new indexes were developed to provide a new understanding of polar sites on their surfaces. We showed that the activity of negative polar sites on the asphaltene and resin structure was higher than positive sites, which confirms that the effect of cations is crucial in the interfacial mechanisms. The interfacial tension (IFT) and zeta potential of the resin and asphaltene fraction were measured in solutions with different concertation of the MgCl2, CaCl2, and Na2SO4. It was observed that the ability of Mg2+ to reduce the IFT of the resin was more than that for Ca2+. This behavior was vice versa for asphaltene fractions.

Molecular Characterization of Aged Bitumen with Selective and Nonselective Ionization Methods by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. 3. Investigation on Molecular Fractions Obtained by Gel Permeation Chromatography

Long-term aging of bitumen causes formation of oxidation products that can be associated with polar and strongly interacting functional groups leading to a tremendous influence on bitumen properties. This can lead to an aggregation of the most polar molecules in the asphaltene fraction. Other types of aggregation have also been described in the literature, with larger and more aliphatic compounds through wax interactions. These aggregate phases can be studied using gel permeation chromatography (GPC) for the separation of heavy petroleum products based on their molecular weight. Three molecular weight fractions of native bitumen and its aged state by a long-term pressure aging vessel (PAV-72h) were obtained with low molecular weight (LMW), medium molecular weight (MMW), and high molecular weight (HMW) fractions. To characterize oxidative aging on each fraction at the molecular level, Fourier transform ion cyclotron resonance (FTICR) was used. Indeed, the ultrahigh resolution and mass accuracy of this analyzer allow to attribute molecular formulas to each signal of complex matrices unambiguously. An electrospray ionization (ESI) source was used to selectively ionize acid molecules, while atmospheric pressure photoionization source (APPI) was used to have a nonselective ionization of low polarity molecules from bitumen. With both ionization sources, the LMW fraction exhibited the most aromatic and heteroelement-enriched molecules. In terms of variation with aging, the LMW fraction showed the most pronounced variations. Molecular maps evidenced the occurrence of low DBE oxidation markers for Oz and OzSy families. Low variations were observed on distributions of MMW and HMW fractions. Concerning HMW, these unexpected results, obtained by ESI and APPI ionization sources, may be due to a protection of the molecules against oxidation within aggregates. In addition, APPI results underlined that the higher molecular weight distribution containing most of the aggregate molecules was mainly composed of large aliphatic molecules. Overall, this study demonstrated that oxidation products corresponded to small and aliphatic molecules majorly found in the LMW fraction and that aggregated molecules form HMW fraction were relatively protected from oxidation.

The role of reservoir fluids and reservoir rock mineralogy on in-situ combustion kinetics

In-situ combustion (ISC) is a complex process with great potential. This study aims to simplify some of the complications associated with the reaction kinetics of ISC and investigate the impact of reservoir rock composition and crude oil fractions on the reaction kinetics of ISC.Sixty-six reaction kinetics experiments were conducted using Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) on two heavy crude oil samples and two types of porous media (clays and carbonates). In these experiments, a 5 °C/min heating rate was used to simulate the low-temperature-oxidation (LTO) region, and a 20 °C/min heating rate was used for the high-temperature-oxidation (HTO) region. The role of crude oil composition on the reaction kinetics of combustion was also investigated through saturates, aromatics, resins, and asphaltenes (SARA) fractionation. The two crude oils were first separated into their SARA fractions, and then the reaction kinetics of individual fractions and their two and three component pseudo-blends were studied.‘To understand the contribution of aquathermolysis reactions, the crude oils and their SARA fractions were mixed with water, and the reaction kinetics tests were repeated in the presence of water. The chemical reactions occurring in the presence and absence of water in crude oil and their fractions were discussed using control experiments conducted on known simple hydrocarbons: n-decane (C10H22), n-decanal (C10H20O), n-decanol (C10H22O), and decanone (C10H20O). Additionally, the reactivity of the mineralogy of the porous media was examined, and both clay and carbonates were tested. All experiments were analytically modeled to obtain reaction kinetics parameters in terms of activation energy (Ea) and heat generation (ΔH).The results show that while emulsified water decreases the effectiveness of the combustion process, the presence of initial water increases it. This is due to the increase in heat generation and decrease in activation energy, which is mainly caused by the interaction between water and aromatics fractions (aquathermolysis reaction) at elevated temperatures. The amount of clay in the reservoir is critical for the success of the ISC process. If the reservoir has a higher clay content than a certain threshold, the combustion performance will be compromised. Resins fractions have a higher tendency to interact with carbonates during ISC in the HTO region.Overall, this study provides simplified analytical approaches based on experimental results to better understand the ISC chemical reaction kinetics for different types of crude oil and reservoir rocks.

Geochemistry of hydrocarbons-biomarkers and carbon isotopes of organic matter in the Domanik Deposits of the Timan-Pechora Basin

It has been established that the average values of some hydrocarbons biomarker coefficients of bitumens from the Domanik deposits and oils from the Domanik–Tournaisian complex coincide. These are the proportions of C27–C29 steranes, tri-/pentacyclanes ratio, and coefficients 2 × С17/С16 + С18 and 2 × С27/С26 + С28 calculated from n-alkane composition. Such indicators as the Pr/Ph, (Pr + Ph)/(n‑C17 + n‑C18), dia-/reg-steranes, and the sterane/hopane ratios in oils are slightly lower than in the bitumen. The average values of δ13C in asphaltene, resin, aromatic hydrocarbons, and aliphatic hydrocarbons fractions from oils of the Domanik genotype and in the studied bitumens are similar. The carbon isotope composition of asphaltenes in oils is depleted in 13С compared to those of resins and aromatic hydrocarbons, and vice versa in bitumens. A heterogeneous composition of the bacterial flora in the sediments of the Domanik Sea is suggested. In some places, species with high concentrations of diplopterol or hexafunctional bacteriohopanes likely dominated over bacteriohopantetrol.

Gas hydrate nucleation and growth in a micro-reactor: Effect of individual component separated from the crude oil in the South China Sea

Gas hydrate has been a major problem for flow assurance due to its potential to cause pipelines clogging inside subsea multiphase transportation systems. Of special interest is that polar components in crude oil should play a significant role in the hydrate formation kinetics, but the detailed understanding of their interaction remains unclear. Here, the individual component in the crude oil collected from the South China Sea was for the first time separated through the saturates, aromatics, resins, and asphaltenes (SARA) fractionation method. The promotion effect of saturates on hydrate nucleation and growth, and the surprising inhibition effect of aromatics and resins were discovered. Specifically, the average induction time was shortened by 45.13 % with the addition of the saturates; while the aromatics and resins would prolong the induction time by 2.20 and 20.83 times, respectively. Results also indicated that gas flow direction determined the behavior of hydrate growth; hydrates preferentially nucleated at the cell walls with a higher subcooling. It was further illustrated that the average growth rate of hydrate films was enhanced by 32.65 % with the addition of the saturates; while it was reduced by 54.01 % and 84.52 % with aromatics and resins, respectively. Our findings provided the first knowledge on the effect of single polar component in crude oil on hydrate formation kinetics; natural fraction such as resins was also suggested for a potential application in preventing hydrates plugging in pipelines.

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.