Separating close-boiling components using distillation is very common in industry. Considering the higher capital and energy intensity of the task, schematic selection of optimal distillation strategies becomes a significant decision of both industrial and methodological importance. In this sense, this paper introduces a reliable shortcut method of simplicity and robustness for optimizing the target of total annualized cost (TAC). In detail, selective analyses are carried out among four schematic candidates for three close-boiling systems. The schemes are conventional distillation column, mechanical vapor recompression (MVR), double-effect distillation, and distillation with a recycle process. The mixtures to be separated are methyltrichlorosilane/dimethylchlorosilane, methylcyclopentane/cyclohexane, and isobutanol/n-butanol. After the first round evaluation, hydraulic calculations through rigorous simulations are worked out to size the equipment, which is necessary for TAC analyses. In the second round comparison, MVR stands out to be a more attractive option for close-boiling separations than other configurations.

Novel core–shell structured ellipsoid-like BiVO4@g-C3N4 composites, with different amounts of g-C3N4, have been successfully prepared by a simple hydrothermal-chemisorption method. Their performance as photocatalysts was systematically evaluated during RhB degradation under visible light irradiation. The composite with 7 wt% g-C3N4 was found to be 7 times more efficient as a photocatalyst than pristine BiVO4. Its core–shell structure and activity were also found to be highly stable after it was used for 5 times in RhB degradation. The new composites were examined by various characterization techniques. The core–shell structure enhanced the contact area between the BiVO4 core and g-C3N4 nano-sheet shell, which provided more active sites and strengthened the chemical band interaction. The thin g-C3N4 nano-sheets reduced the charge carrier transfer distance, which further suppressed the recombination of the photo-induced electron–hole pairs and therefore enhanced the photocatalytic activity of the composites. A reaction mechanism of the photocatalytic RhB degradation was proposed and discussed in detail.

•A novel process superstructure for methanol distillation system is developed.•HEN and WEN are integrated into the optimized scheme simultaneously.•Significant saving in operating cost could be achieved in the optimized scheme.Despite the current methanol distillation system (MDS) touching a highly energy-efficient level, there are still opportunities to cut more corners when moving eyesight from heating media to electricity and work efficiency of rotary equipments. To simultaneously optimize this process for higher overall energy efficiency, methodologically an improved substitute pathway is herein proposed of corresponding process superstructure. In detail, it is an all-in-one integration of heat and work exchanger networks (HEN-WEN), exemplified by a 4-column double-effect methanol distillation scheme popular among Chinese coal-based factories. The completion of this work indicates a hope of potential reductions of pump electricity and reboiler steam consumption of the whole unit by further 68.38% and 15.83%, respectively.

Separation of heavy hydrocarbons from mineral surfaces is the key step for unconventional oil production and remediation of oil-contaminated soils. The presence of asphaltene and the coexistence of mineral rocks are considered as the most challenge during the above separation processes. Herein, the liberation of asphaltenes (and/or heavy oil) on the muscovite [KAl2(Si3Al)O10(OH)2)] surface has been systematically investigated through instrumental characterization and molecular dynamics (MD) simulation. It is observed that, quite different from that on the silica surface, asphaltenes can flake off from the muscovite surface as a result of the weaker adhesion force between asphaltenes and the muscovite surface. This liberation pattern was also found to be influenced by the addition of other oil fractions. The micro force measurements by atomic force microscopy show that the adhesion force between asphaltenes and muscovite is weaker than that between asphaltenes and silica in both air and water. Assisted by the MD simulation, it is found that the detachment of asphaltenes is highly dependent upon the mineral types and the presence of the water film on the mineral surfaces. Although the van der Waals force is found to be the main force between asphaltenes and mineral surfaces, the presence of potassium ions (K+) on the muscovite surface could increase the percentage of the electrostatic forces in the total force. Furthermore, the presence of a 0.4 nm water layer (in the air) between asphaltenes and the muscovite surface could reduce their interactions dramatically compared to that in a vacuum state. This finding suggests that the presence of water between the mineral surface and oil is beneficial for the separation of oil from the mineral surface. In addition, the asphaltene molecules are found to contact with the silica surface by face-to-face (aromatic ring) form, while a much more perpendicular orientation of the asphaltene molecules on the muscovite surface.

Selection of solvents and process aids (i.e., ionic liquids (ILs)) is considered to be one of the key steps during solvent extraction for heavy hydrocarbon recovery from unconventional oil ores. In this study, the COSMOtherm software was applied to screen highly efficient solvents and ionic liquid systems based on oil fraction solubility and surface free energy calculations. It is found that the dispersion force parameter (δd) of solvents plays the dominant role in dissolving oil fractions compared with the roles of the polar force parameter (δp) and hydrogen bonding force parameter (δh). The simulation results also show that the surface free energy of oil fractions (SARA fractions) at the organic solvent-IL interface is significantly lower than that found at the IL-SARA fraction interface, which is favorable for unconventional oil dissolution in solvents. In addition, further interactive energy calculation shows that the interaction between IL and the silica surface is stronger than that between oil fraction and the silica surface. These results suggest that the presence of IL between the organic solvent and oil fraction is beneficial for the transfer of the oil fraction from the solid surface and bulk oil phase to the bulk organic solvent. Additionally, unconventional oil recovery has been found to be highly influenced by the mutual solubility between the solvent and IL, which increased the entrainments of oil components in the IL phase. Calculation of surface free energy and mutual solubility suggests that increasing the chain length of IL molecules is detrimental for bitumen extraction due to the higher mutual solubility of solvents and entrainments of bitumen in ILs. The above simulation results are confirmed by the bottle extraction tests and instrumental detection in which the oil sands ores are extracted by organic solvents with or without ILs. These findings suggest that the COSMOtherm simulation is a potential way for future solvent and IL screening as well as a way to reveal mechanism during unconventional oil exploitation, which would save time and cost.

With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply. Compared with the conventional reserves unconventional oil reserves are characterized by extremely high viscosity and density, combined with complex chemistry. As a result, petroleum production from unconventional oil reserves is much more difficult and costly with more serious environmental impacts. As a key underpinning science, understanding the interfacial phenomena involved in unconventional petroleum production, such as oil liberation from host rocks, oil–water emulsions and demulsification, is critical for developing novel processes to improve oil production while reducing GHG emission and other environmental impacts at a lower operating cost. In the past decade, significant efforts and advances have been made in applying the principles of interfacial sciences to better understand complex unconventional oil-systems, while many environmental and production challenges remain. In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed. In particular, the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail. This review also seeks to summarize the current state-of-the-art characterization techniques and brings forward the challenges and opportunities for future research in this important field of physical chemistry and petroleum.

Bitumen liberation is known to be an essential step for bitumen recovery from sand grains using the current warm/hot-water-based extraction process. This study aims at understanding the role of naphtha or toluene addition in enhancing bitumen liberation. Results from an in situ bitumen liberation visualization measurement indicate that soaking two oil sands ores by solvents at 10–30 wt % of the bitumen could significantly enhance not only the ultimate degree of bitumen liberation (UDBL) but also the rate of bitumen liberation (RBL) in the process water at ambient conditions. Although ore-type- and solvent-type-dependent, both the UDBL and RBL would increase sharply at 10–20 wt % solvent dosage. A further increase in solvent dosage showed a diminished increase in the UDBL. To understand the observed improvement, viscosities of bitumen directly extracted from the ores and its mixture with solvents were measured, as well as diluted bitumen–water interfacial tensions. Results showed that adding solvent into the bitumen reduced bitumen–water interfacial tension and more so for the reduction in bitumen viscosity. Interestingly, the viscosity and interfacial tension of diluted bitumen were found to be dependent upon the source of ores and type of solvents. The UDBL was found to be inversely correlated with the interfacial tension and bitumen viscosity, while the RBL correlated almost linearly with the interfacial tension/viscosity ratio, which acted as the balance of the interfacial tension driving force/adhesion drag force. These correlations were less dependent upon the types of ores and solvents.

The composition and distribution of saturates, aromatics, resins, and asphaltenes (SARA) fractions in the bituminous layer on the surface of Athabasca oil sands were identified using elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM) with an energy-dispersive spectrometer (EDS), and Fourier transform infrared spectrometry (FTIR). The contents of elements sulfur (S) and nitrogen (N) and the ratios of carbon/sulfur (C/S) and carbon/nitrogen (C/N) were characterized as potential indicators for evaluating the distribution of SARA fractions in the bituminous layer. Results indicated that saturates and aromatics tend to deposit at the outer bituminous layer, while asphaltenes and resins were inclined to distribute at the inner layer. Results also suggested that the distribution of SARA fractions was thermodynamically dependent and susceptible to thermal treatment. On the basis of the experimental results, a conceptual distribution model was proposed, which is supposed to serve as a basis for future studies on the liberation of bitumen from oil sands and the operation conditions for oil sands processing.

Selective adsorption has demonstrated minimal influence on the quality of aromatics-containing fuels. Considering the exposed surface of fibers for mass transfer, metallic silver was supported on adsorbent cotton fibers via an aqueous reduction–dehydration method with virtues such as extra low silver loading (0.2 wt %), facile preparation, low energy consumption, and no toxic emissions. On the basis of adsorption tests, thermogravimetric analysis (TGA)/differential thermal analysis (DTA) and energy-dispersive X-ray spectroscopy (ESEM-EDX), it is confirmed that the active component of adsorption is Ag0 instead of Ag+. It is attributed to the distinct polarities of thiophene–octane (model oil) and AgNO3. Model oil (500 ppmw sulfur) was pressed into an adsorption column without solvent for degassing. Temperature and retention time dependencies on capacity were investigated below 60 °C and at flow rates of 0.2 and 0.3 mL/min. The adsorption is substantially coordinative reaction. Higher capacities were determined at 50 °C in 2 h with an average sulfur removal of 27.6%, and sulfur removal declined at temperatures above 60 °C.

Nonaqueous solvent extraction is a promising technology for bitumen recovery from oil sands. In this study, influences of temperature, contact time, stirring rate, and solvent-to-oil sands ratio (V/M) on bitumen recovery, using a mixture solvent of n-heptane and toluene (V/V, 3:1), were investigated by L9 (34) orthogonal design. Under the orthogonal experiment conditions, the overall impacts of factors were ranked: V/M > stirring rate > contact time > temperature. Profiles of bitumen fractions (saturates, aromatics, resins, and asphaltenes) in the dissolved bitumen, suspended particles, and residual bitumen were investigated in single factor experiments. Asphaltenes have higher temperature sensitivity than other fractions. About 3–7 wt % bitumen particles coexisted with clay minerals (50–70 wt % of the suspended particles) suspended in the solution, most of which were composed of asphaltenes. Approximately 75–90 wt % of SAR fractions (saturates, aromatics, and resins) were dissolved in the composite solvent under the experimental conditions. The amount of residual fractions varied with conditions, and multistage extraction enhanced the bitumen recovery by up to 99%. The evaluation method for bitumen recovery based on dissolved fraction outperformed the methods based on the sum of dissolved and suspended particles. The conceptualization of the solvent extraction process in this study would improve the knowledge base for bitumen recovery mechanism and serve for future work on the engineering applications.

An ionic liquid (IL) with low viscosity, 1-ethyl-3-methyl imidazolium tetrafluoroborate ([Emim][BF4]), was used to enhance bitumen recovery from oil sands by solvent extraction using a composite solvent of n-heptane and acetone. Results demonstrated that [Emim][BF4] increased the bitumen recovery by up to 95% at room temperature. Much less clay fines in the recovered bitumen than those using solvent extraction without IL, and organic residue was not observed in the spent sands. This technology circumvented the issue of tailing water because only a small amount of water was used to recycle IL, and organic solvent could be readily regenerated by distillation. The low viscosity of [Emim][BF4] made it outperform other alternative ILs for application in the oil sand industry. Results also highlighted the role of acetone in this technology (i.e., decrease IL viscosity and reduce IL consumption). The optimal solvent extraction conditions were found to be stirring for 10 min at 450 rpm at 25 °C. The optimized ratio of acetone to n-heptane in the composite solvent and the ratio of organic solvents to oil sands was determined as 2:6 (v/v) and 4:1 (v/w), respectively.

•We examine the influence of chalk pore sizes on the fate of hydrocarbon fractions.•We determine distribution coefficient (Kd) for each hydrocarbon fraction.•We simulate the fate and transport of aliphatic and aromatic hydrocarbons in chalk.•Monte Carlo and sensitivity analyses identified key parameters and uncertainties.Although great efforts had been devoted to investigate the fate and transport of various hydrocarbon sources in major aquifers, there is still a need to better understand and predict their behaviour for robust risk assessment. In this study, the fate and distribution of the aliphatic and polycyclic aromatic hydrocarbons (PAHs) of diesel fuel in chalk aquifer was investigated using a series of leaching column tests and then modelled using the Contaminant Transport module of the Goldsim software. Specifically the influence of chalk particle size on the behaviour and fate of the hydrocarbons was investigated. Distribution coefficient (Kd) between the water and chalk solid phase according to chalk particle sizes was determined for each hydrocarbon group. The larger sizes of chalk particles have higher Kd values. After 60 d of leaching using a water flow of 45 mm d−1, most of the aliphatic and aromatic hydrocarbon compounds of the diesel were retained within the top 5 cm chalk layer and none of the targeted hydrocarbons were detected in the leachate from the four particles sizes chalk. Further to this, the results showed that the chalk is capable of holding more hydrocarbons than sand and chalk can limit their migration of hydrocarbons. The numerical results and the Monte Carlo analysis showed that the migration of the alkanes and PAHs is greatly retarded by the organic carbon in chalk. It is also observed that the initial mass of the alkanes and PAHs and their respective partition coefficients are important for the decaying of the source at the surface immediately after the spill and the rate-limited dissolution is responsible for entrapping the hydrocarbons in the top layer of the chalk. Overall these results can help to better inform risk assessment and help decision for the remediation strategy.

•Biodegradable ethyl cellulose (EC) enhanced bitumen liberation from solid surfaces.•EC reduced contact angle of bitumen droplet on solid surface in water (water wet).•EO/PO co-polymers enhanced liberate bitumen much faster than EC.Ethyl cellulose (EC) and EO/PO polymers are known as efficient demulsifiers for breaking oil–water emulsions, which are applied in this study as process aids to enhancing unconventional oil liberation from host rock surfaces. Their applicability in such a role was assessed by studying dynamic contact angle and liberation of bitumen from model solid surfaces. The addition of demulsifiers (EC and/or EO/PO blocked co-polymer, up to 300 ppm) into the solvent-diluted bitumen was found to significantly improve both bitumen liberation rate and ultimate degree of bitumen liberation (DBL) from glass surfaces. This finding suggests the potential combination of oil liberation and demulsification to develop more efficient process for recovering unconventional oils.Download high-res image (96KB)Download full-size image

This study aimed to evaluate the efficacy, practicality and sustainability of a combined approach based on solvent extraction and biodegradation to remediate the soils contaminated with high levels of weathered petroleum hydrocarbons. The soils used in this study were obtained from the Shengli Oilfield in China, which had a long history of contamination with high concentrations of petroleum hydrocarbons. The contaminated soils were washed using a composite organic solvent consisting of hexane and pentane (4:1, v/v) and then bioremediated in microcosms which were bioaugmentated with Bacillus subtilis FQ06 strains and/or rhamnolipid. The optimal solvent extraction conditions were determined as extraction for 20 min at 25 °C with solvent-soil ratio of 6:1 (v/w). On this basis, total petroleum hydrocarbon was decreased from 140 000 to 14 000 mg kg−1, which was further reduced to < 4 000 mg kg−1 by subsequent bioremediation for 132 d. Sustainability assessment of this integrated technology showed its good performance for both short- and long-term effectiveness. Overall the results encouraged its application for remediating contaminated sites especially with high concentration weathered hydrocarbons.

With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply. Compared with the conventional reserves unconventional oil reserves are characterized by extremely high viscosity and density, combined with complex chemistry. As a result, petroleum production from unconventional oil reserves is much more difficult and costly with more serious environmental impacts. As a key underpinning science, understanding the interfacial phenomena involved in unconventional petroleum production, such as oil liberation from host rocks, oil–water emulsions and demulsification, is critical for developing novel processes to improve oil production while reducing GHG emission and other environmental impacts at a lower operating cost. In the past decade, significant efforts and advances have been made in applying the principles of interfacial sciences to better understand complex unconventional oil-systems, while many environmental and production challenges remain. In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed. In particular, the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail. This review also seeks to summarize the current state-of-the-art characterization techniques and brings forward the challenges and opportunities for future research in this important field of physical chemistry and petroleum.