A critical review of the development and demulsification processes applied for oil recovery from oil in water emulsions

Advancing oil-water separation: Design and efficiency of amphiphilic hyperbranched demulsifiers

HYPOTHESIS

An innovative strategy for designing high-performance demulsifiers is proposed. It hypothesizes that integrating mesoscopic molecular simulations with macroscopic physicochemical experiments can enhance the understanding and effectiveness of demulsifiers. Specifically, it is suggested that amphiphilic hyperbranched polyethyleneimine (CHPEI) could act as an efficient demulsifier in oil-water systems, with its performance influenced by its adsorption behaviors at the oil-water interface and its ability to disrupt asphaltene-resin aggregates.

EXPERIMENTS

Several coarse-grained models of oil-water systems, with CHPEI, are constructed using dissipative particle dynamics (DPD) simulation. Following the insights gained from the simulations, a series of CHPEI-based demulsifiers are designed and synthesized. Demulsification experiments are conducted on both simulated and crude oil emulsions, with the process monitored using laser scanning confocal microscopy. Additionally, adsorption kinetics and small angle X-ray scattering are employed to reveal the inherent structural characteristics of CHPEI demulsifiers.

FINDINGS

CHPEI demonstrates over 96.7 % demulsification efficiency in high acid-alkali-salt systems and maintains its performance even after multiple reuse cycles. The simulations and macroscopic experiments collectively elucidate that the effectiveness of a demulsifier is largely dependent on its molecular weight and the balance of hydrophilic and hydrophobic groups. These factors are crucial in providing sufficient interfacial active functional groups while avoiding adsorption sites for other surfactants. Collaborative efforts between DPD simulation and macroscopic measurements deepen the understanding of how demulsifiers can improve oil-water separation efficiency in emulsion treatment.

Nonionic Demulsifier for Smart Demulsification of Crude Oil Emulsion at Room and Moderate Temperatures

This study reports the demulsification activity of a newly developed nonionic demulsifier (NID) via the condensation of glycolic acid ethoxylate lauryl ether with amine. The demulsification performance of the developed NID was assessed under room and moderate temperatures (25 and 60 °C), while the concentrations of NID were varied from 100 to 700 ppm at both temperatures in order to observe their oil-water separation efficiency. The demulsification mechanism was expatiated by determining the viscosity and elastic modulus of emulsion in the presence and absence of the NID. Adsorption at the oil and water interface was analyzed through a series of interfacial tension measurements. Accordingly, under the aforementioned temperatures, the optimal demulsification efficiency of the NID was 95% (25 °C) and 99% (60 °C) at 500 ppm. Viscosity determination at both temperatures revealed a drastic reduction in emulsion viscosity in the presence of NID, and the viscosity drop was of high magnitude at moderate temperatures (60 °C). Likewise, the elastic modulus measurements in bulk rheology revealed that the presence of NID in the emulsion weakened the elastic strength. Again, the interfacial modulus test exhibited the percolation of NID at the oil-water interface and the displacement of asphaltenes. Interfacial tension (IFT) measurements of the oil-water system at different NID concentrations showed that the particles were adsorbed at the oil-water interface. The IFT values of the oil-water system in the presence of NID ranged from 1.84 to 3.02 mN/m as compared to that of the NID-free oil-water system recorded as 16.11 mN/m. It is envisaged that this new nonionic demulsifier would be very useful in oilfields and petrochemical industries.

Demulsification of Pickering emulsions: advances in understanding mechanisms to applications

Pickering emulsions are ultra-stable dispersions of two immiscible fluids stabilized by solid or microgel particles rather than molecular surfactants. Although their ultra-stability is a signature performance indicator, often such high stability hinders their demulsification, i.e., prevents the droplet coalescence that is needed for phase separation on demand, or release of the active ingredients encapsulated within droplets and/or to recover the particles themselves, which may be catalysts, for example. This review aims to provide theoretical and experimental insights on demulsification of Pickering emulsions, in particular identifying the mechanisms of particle dislodgment from the interface in biological and non-biological applications. Even though the adhesion of particles to the interface can appear irreversible, it is possible to detach particles via (1) alteration of particle wettability, and/or (2) particle dissolution, affecting the particle radius by introducing a range of physical conditions: pH, temperature, heat, shear, or magnetic fields; or via treatment with chemical/biochemical additives, including surfactants, enzymes, salts, or bacteria. Many of these changes ultimately influence the interfacial rheology of the particle-laden interface, which is sometimes underestimated. There is increasing momentum to create responsive Pickering particles such that they offer switchable wettability (demulsification and re-emulsification) when these conditions are changed. Demulsification via wettability alteration seems like the modus operandi whilst particle dissolution remains only partially explored, largely dominated by food digestion-related studies where Pickering particles are digested using gastrointestinal enzymes. Overall, this review aims to stimulate new thinking about the control of demulsification of Pickering emulsions for release of active ingredients associated with these ultra-stable emulsions.

Cucurbit[7]uril-Modified Nano SiO2 for Efficient Separation of Crude Oil Emulsions: Properties and Demulsification Mechanism

Demulsification of crude oil emulsion is an obvious problem in the whole of petroleum engineering, which needs to be dealt with urgently. In this paper, a supramolecular material Cucurbit[7]uril-SiO2 (CB-SiO2) synthesized with excellent demulsification efficiency (DE) on O/W emulsion was synthesized by a simple thermal synthesis method. The microscopic morphology and structure were investigated through modern characterization techniques. Furthermore, its stability, dynamic interfacial tension (IFT), and wettability (three-phase contact angle (CA)) were systematically investigated, and the demulsification efficiency of different conditions on crude oil emulsion was also investigated. Reassuringly, these results showed that when the temperature was 70 °C, the demulsification dosage was close to 600 mg/L and remained unchanged for 90 min; the demulsification efficiency is 2.2 times compared with the unmodified material, up to 93.63%. In addition, a plausible demulsification mechanism was proposed, which is that CB-SiO2 can adsorb and disrupt the oil-water interface, leading to oil-water separation and promoting demulsification. It is a promising demulsification material for the oil industry demulsification.

Review on demulsification techniques for oil/water emulsion: Comparison of recyclable and irretrievable approaches

Since the establishment of the first global refinery in 1856, crude oil has remained one of the most lucrative natural resources worldwide. However, during the extraction process from reservoirs, crude oil gets contaminated with sediments, water, and other impurities. The presence of pressure, shear forces, and surface-active compounds in crude oil leads to the formation of unwanted oil/water emulsions. These emulsions can take the form of water-in-oil (W/O) emulsions, where water droplets disperse continuously in crude oil, or oil-in-water (O/W) emulsions, where crude oil droplets are suspended in water. To prevent the spread of water and inorganic salts, these emulsions need to be treated and eliminated. In existing literature, different demulsification procedures have shown varying outcomes in effectively treating oil/water emulsions. The observed discrepancies have been attributed to various factors such as temperature, salinity, pH, droplet size, and emulsifier concentrations. It is crucial to identify the most effective demulsification approach for oil/water separation while adhering to environmental regulations and minimizing costs for the petroleum sector. Therefore, this study aims to explore and review recent advancements in two popular demulsification techniques: chemical demulsification and magnetic nanoparticles-based (MNP) demulsification. The advantages and disadvantages of each technique are assessed, with the magnetic approach emerging as the most promising due to its desirable efficiency and compliance with environmental and economic concerns. The findings of this report are expected to have a significant impact on the overall process of separating oil and water, benefiting the oil and gas industry, as well as other relevant sectors in achieving the circular economy.

Efficient Demulsification Performance of Emulsified Condensate Oil by Hyperbranched Low-Temperature Demulsifiers

Focusing on the problem of poor demulsification performance of light crude oil emulsions in low-permeability oilfields at low temperatures, the composition of the emulsion samples, clay particle size distribution, and the viscosity-temperature relationship curve of samples were analyzed. Based on the results of emulsion composition analysis and characteristics, the bottle test method was used to analyze the demulsifying effect of different commercial types of demulsifiers, revealing the demulsification mechanism. The field tests confirm the demulsification capabilities of Polyoxyethylene polyoxypropylene quaternized polyoxyolefins surfactants (PR demulsifiers). The results reveal that PR demulsifiers combine the features of decreasing the interfacial tension between oil and water and adsorbing SiO2, allowing for quick demulsification and flocculation at low temperatures. This research serves as a theoretical and practical foundation for the study and advancement of low-temperature demulsification technology in oilfields.

Sequential Demulsification through the Hydrophobic-Hydrophilic-Hydrophobic Filtration Layer toward High-Performing Oil Recovery

Demulsification using membranes is a promising method to coalesce highly stable emulsified oil droplets for oil recovery. Nevertheless, a structure of the current filtration medium that is not efficient for oil droplet coalescence impedes rapid permeability, thereby inevitably restricting their practical applications. Herein, we report a hydrophobic-hydrophilic-hydrophobic (3H) demulsification medium that exhibits a benchmark permeability of ∼2.1 × 104 L m-2 h-1 with a demulsification efficiency of >98.0%. Remarkably, this 3H demulsification medium maintains over 90% demulsification efficiency in the oil-in-water (O/W) emulsions with a wide range of surfactant concentrations, which shows excellent applicability. Based on the combined results of quasi situ microscope images and molecular dynamics simulations, we show that the polydimethylsiloxane-modified hydrophobic layer facilitates the capture and coalescence of oil droplets, the hydrophilic inner layer assists in squeezing the coalescence of enlarged droplets, and the third hydrophobic layer accelerates the discharge of demulsified oil to sustain permeability. The sequential demulsification mechanism between this 3H filtration layer provides a general guide for designing a demulsifying membrane with high demulsification efficiency and high flux toward oil recovery.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe₃O₄ nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Bioremediation of Crude Oil by Haematococcus Pluvialis: A Preliminary Study

Nowadays, oil pollution is one of the main environmental problems. The current methods for recovering spills mainly involve chemical agents, but scientific research has focused on more natural and less harmful techniques for the environment, including a consortium of bacteria and microalgae to clean up water contaminated by hydrocarbons. The purpose of this preliminary study was to evaluate the ability of a microalga belonging to Chlorophyceae to grow in the presence of crude oil and remove the principal contaminants. H. pluvialis, which is usually used for nutraceutical purposes, thanks to the production of astaxanthin, was able to grow in anaerobic conditions, varying its metabolism from autotrophic to heterotrophic, exploiting the carbon present in the solution deriving from the presence of 1% of crude oil. Furthermore, the results of bioremediation showed a relevant reduction in chemical pollutants such as nitrate, fluoride, sulfate, and phosphate. The most important aspect of the study was the reduction after 160 days in the hydrocarbon concentration inside not only the culture medium (−32%) but also the algal biomass (−80.25%), demonstrating an optimized degradation rather than a simple absorption inside the alga.