Stable CO2/water foam stabilized by dilute surface-modified nanoparticles and cationic surfactant at high temperature and salinity

CO₂ enhanced oil recovery and storage could see widespread deployment as decarbonization efforts accelerate to meet climate goals. CO₂ is more efficiently distributed underground as a viscous foam than as pure CO₂; however, most reported CO₂ foams are unstable at harsh reservoir conditions (22 wt% brine, 2200 psi, and 80°C). We hypothesize that silica nanoparticles (NP) grafted with (3-trimethoxysilylpropyl)diethylenetriamine ligands (N3), to improve colloidal stability, and dimethoxydimethylsilane ligands (DM), to improve CO₂-phillicity, combined with the cationic surfactant N¹-alkyl-N³, N³-dimethylpropane-1,3-diamine (RCADA), will develop viscous, stable CO₂ foams at reservoir conditions. We grafted NP with N3 and DM ligands. We verified NP stability at reservoir conditions with measurements of zeta potential, amine titration curves, and NP diameter. We measured NP water contact angles (θ_w) at the water–air and water–liquid CO₂ interfaces. In a high-temperature, high-pressure flow apparatus, we calculated the viscosity of CO₂ foams across a beadpack and determined static foam stability with microscope observations. Modified NP were colloidally stable at reservoir conditions for 4 weeks, and had higher θ_w in liquid CO₂ than in air. Addition of at least 0.5 μmol/m² DM silane (0.5DM) greatly improved foam stability. RCADA-only foam coarsening rates (dD_SM³/dt) decreased 16–17× after adding 1 wt/vol% 8N3 + 1.5DM NP, and 5–10× with a 0.1–1 vol/vol% increase in RCADA concentration (with or without NP). 1 vol/vol% RCADA foam exhibited coarsening rates of 900 and 2400 μm³/min with 1 and 0.2 wt/vol% 8N3 + 1.5DM NP, respectively. These results demonstrate impressive foam stabilities at harsh reservoir conditions.     

Stability improvement of CO2 foam for enhanced oil‐recovery applications using polyelectrolytes and polyelectrolyte complex nanoparticles

CO₂ foam for enhanced oil‐recovery applications has been traditionally used in order to address mobility‐control problems that occur during CO₂ flooding. However, the supercritical CO₂ foam generated by surfactant has a few shortcomings, such as loss of surfactant to the formation due to adsorption and lack of a stable front in the presence of crude oil. These problems arise because surfactants dynamically leave and enter the foam interface. We discuss the addition of polyelectrolytes and polyelectrolyte complex nanoparticles (PECNP) to the surfactant solution to stabilize the interface using electrostatic forces to generate stronger and longer‐lasting foams. An optimized ratio and pH of the polyelectrolytes was used to generate the nanoparticles. Thereafter we studied the interaction of the polyelectrolyte–surfactant CO₂ foam and the polyelectrolyte complex nanoparticle–surfactant CO₂ foam with crude oil in a high‐pressure, high‐temperature static view cell. The nanoparticle–surfactant CO₂ foam system was found to be more durable in the presence of crude oil. Understanding the rheology of the foam becomes crucial in determining the effect of shear on the viscosity of the foam. A high‐pressure, high‐temperature rheometer setup was used to shear the CO₂ foam for the three different systems, and the viscosity was measured with time. It was found that the viscosity of the CO₂ foams generated by these new systems of polyelectrolytes was slightly better than the surfactant‐generated CO₂ foams. Core‐flood experiments were conducted in the absence and presence of crude oil to understand the foam mobility and the oil recovered. The core‐flood experiments in the presence of crude oil show promising results for the CO₂ foams generated by nanoparticle–surfactant and polyelectrolyte–surfactant systems. This paper also reviews the extent of damage, if any, that could be caused by the injection of nanoparticles. It was observed that the PECNP–surfactant system produced 58.33% of the residual oil, while the surfactant system itself produced 47.6% of the residual oil in place. Most importantly, the PECNP system produced 9.1% of the oil left after the core was flooded with the surfactant foam system. This proves that the PECNP system was able to extract more oil from the core when the surfactant foam system was already injected. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44491.     

Determination of Dodecanol and Short‐Chained Ethoxylated Dodecanols by LC–MS/MS (with Electrospray Ionization) After Their Derivatization (with Phenyl Isocyanate)

This report describes the application of LC–MS/MS for the separation of dodecanol (C₁₂OH) and homogenous fatty alcohols ethoxylated (AE) containing a dodecyl moiety and 1–9 ethoxy groups. These ethoxylates and free alcohol were derivatized for LC–MS/MS analysis with phenyl isocyanate (PIC). The derivatives of analytes with PIC were separated using a C18 column. Gradient elution with a mixture of ethyl acetate and acetonitrile (5 mM) was employed. The described determination method is characterized by low detection limits (range from 0.005 µg L^?1 for: C₁₂OH, C₁₂EO_2–7 to 1 µg L^?1 for C₁₂EO₁) and quantification limits (range from 0.01 µg L^?1 for: C₁₂EO_5–7 to 2 µg L^?1 for C₁₂EO₁). The developed and validated method was used in combination with liquid–liquid extraction (using ethyl acetate) in order to identify and quantitatively determine the C₁₂OH and C₁₂EO_1–9 present in environmental samples collected from Warta river water in Poznan.     

Performance of the hydrolyzation film bed and biological aerated filter (HFB–BAF) combined system for the treatment of low‐concentration domestic sewage in south China

The performance of the hydrolyzation film bed and biological aerated filter (HFB–BAF) combined system in pilot scale (with a daily treatment quantity of 600–1300 m³ d^?1), operated for 234 days, for low‐strength domestic sewage was assessed using different amounts of aeration, reflux ratios and hydraulic loading rates (HLR). In steady state it was found that the average removal efficiency of chemical oxygen demand (COD) and biological oxygen demand at 5 days (BOD₅) were 82.0% and 82.2% and the average effluent concentrations were 15.8 mg L^?1 and 9.4 mg L^?1 respectively as the HFB was running at an HLR of 1.25–1.77 m³ m^?2 h^?1 and the BAF was running at an HLR of 1.56–2.21 m³ m^?2 h^?1. In general, the removal efficiency of total nitrogen (TN) fluctuated with the HLR, gas–water ratio and reflux ratio, so the ratio of gas to water should be controlled from 2:1 to 3:1 and the reflux ratio should be as high as possible. The effluent concentration of TN was 10.4 mg L^?1 and the TN removal averaged 34.3% when the gas–water ratio was greater than 3:1 and the reflux ratio was 0.5. The effluent concentration and removal efficiency of NH₄⁺‐N averaged respectively 2.3 mg L^?1 and 78.5%. The overall reduction of total phosphorus (TP) was 30% and the average effluent concentration was 0.95 mg L^?1. The removal efficiency of linear alkylbenzene sulfonates (LAS) reached 83.8% and the average effluent concentration was almost 0.9 mg L^?1. The effluent concentration and removal efficiency of polychlorinated biphenyls (PCBs) were 0.0654 µ g L^?1 and 37.05% respectively when the influent concentration was 0.1039 µ g L^?1. The excess sludge containing water (volume 15 m³) was discharged once every 3 months. The power consumption of aeration was 0.06–0.09 kWh of sewage treated. The results show that the HFB–BAF combined technology is suitable for the treatment of low‐concentration municipal sewage in south China. Copyright © 2005 Society of Chemical Industry     

Carbon dioxide‐in‐water foams stabilized with nanoparticles and surfactant acting in synergy

Synergistic interactions at the interface of nanoparticles (bare colloidal silica) and surfactant (caprylamidopropyl betaine) led to the generation of viscous and stable CO₂‐in‐water (C/W) foams with fine texture at 19.4 MPa and 50°C. Interestingly, neither species generated C/W foams alone. The surfactant became cationic in the presence of CO₂ and adsorbed on the hydrophilic silica nanoparticle surfaces resulting in an increase in the carbon dioxide/water/nanoparticle contact angle. The surfactant also adsorbed at the CO₂–water interface, reducing interfacial tension to allow formation of finer bubbles. The foams were generated in a beadpack and characterized by apparent viscosity measurements both in the beadpack and in a capillary tube viscometer. In addition, the macroscopic foam stability was observed visually. The foam texture and viscosity were tunable by controlling the aqueous phase composition. Foam stability is discussed in terms of lamella drainage, disjoining pressure, interfacial viscosity, and hole formation. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3490–3501, 2013     

Synthesis and Assessment of a CO2‐Switchable Foaming Agent Used in Drilling Fluids for Underbalanced Drilling

In underbalanced drilling, a switchable foam fluid is essential to reduce the drilling cost. A switchable foaming agent was synthesized by carbonyl–amine condensation and characterized by Fourier transform infrared and ¹H nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis and differential scanning calorimetry showed that the tolerable temperature limit of the surfactant was 128 °C. The effectiveness of CO₂/N₂ switching was confirmed by analysis of the electrical conductivity and surface tension. Utilizing the foaming agent, 3 different foam systems (unstable, stable, and hard) were designed for drilling after formula optimization. Experimentally, the self‐circulation indicated that the foaming fluids still maintained great foaming performance even after multiple cycles. The experiment also indicated that the suspension of the foam systems was 50–90 times that of water and had a significant resistance to salts (NaCl, CaCl₂). Besides, the foam systems found that the suitable foaming temperature was 40–100 °C and that the hard foam system could maintain the foaming performance up to 120 °C. In the oil resistance experiment, the foaming ability of the foam systems decreased obviously above a kerosene content of 5% (w/v), whereas a certain foaming performance still could be ensured below 10% kerosene.     

Performance of a UV‐assisted Hydrogen‐peroxide‐fed Spray Tower for Sulfur Dioxide Abatement

Spray towers are widely used for controlling air pollution by gases such as SO₂, CO₂, NO_x, and HCl. Results of sulfur dioxide absorption in a spray tower using solutions of 1 g L^–1 and 2 g L^–1 of hydrogen peroxide are reported. For comparison, a water and sodium hydroxide solution was also used for SO₂ abatement. The results indicate that H₂O₂ may be an important alternative for SO₂ removal in spray towers. A set of experimental removal efficiency data was obtained as a function of gas and liquid flow rates. Volumetric mass transfer coefficients (k_ga) were calculated and an experimental relationship among k_ga, gas, and liquid flow rates was proposed. As a final experiment, an oxidation process assisted by UV radiation using a 1 g L^–1 solution of H₂O₂ was carried out to speed up the SO₂ removal rate. The results obtained in this condition are similar to those achieved with a solution of 2 g L^–1 H₂O₂.     

On the Effect of Surfactant on Mass Transfer to Water–Glycerol Solutions in a Pulsed Baffled Reactor

This paper describes the effect of surfactant (0·025%w/w octanol) on mass transfer of oxygen into water–glycerol solutions of viscosity up to 21 mPa s in a pulsed baffled reactor. We also report the effect of air entrainment on the volumetric mass transfer coefficient in the open reactor system. The results show that the presence of octanol in solutions increases the mass transfer rate for all the experimental conditions tested, in particular, a higher percentage increase in k_La was obtained for more viscous solutions. This behaviour can be attributed to the non-coalescing characteristics of the octanol that is added to the water–glycerol solutions. The results of air entrainment on k_La suggest that the effect of the surface air entrained into the system on k_La measurement is insignificant. © 1997 SCI.     

Synthesis and Surface Properties of a Novel Sodium 3‐(3‐Alkyloxy‐3‐oxopropoxy)‐3‐oxopropane‐1‐sulfonate at the Air–Water Interface

The present paper describes the synthesis and evaluation of surface properties of a novel series of anionic surfactant, namely sodium 3‐(3‐alkyloxy‐3‐oxopropoxy)‐3‐oxopropane‐1‐sulfonate with varying alkyl chain length (C8–C16). Synthesis involves initial formation of the 3‐alkyloxy‐3‐oxopropyl acrylate along with fatty acrylate during the direct esterification of fatty alcohol with acrylic acid in the presence of 0.5 % NaHSO₄ at 110 °C followed by sulfonation of the terminal double bond of the 3‐alkyloxy‐3‐oxopropyl acrylate. Synthesized compounds were evaluated for surface and thermodynamic properties such as critical micelle concentration (CMC), surface tension at CMC (γ_cmc), efficiency of surface adsorption (pC₂₀), surface excess (Γ_max), minimum area per molecule at the air–water interface (A_min), free energy of adsorption (?G°_ads), free energy of micellization (?G°_mic), wetting time, emulsifying properties, foaming power and calcium tolerance. Effect of chain length on CMC follows the classic trend, i.e. decrease in CMC with the increase in alkyl chain length. High pC₂₀ (>3) value indicates higher hydrophobic character of the surfactant. These surfactants showed very poor wetting time and calcium tolerance, but exhibited good emulsion stability and excellent foamability. Foaming power and foam stability of C14‐sulfonate were found to be the best among the studied compounds. Foam stability of C14‐sulfonate was also studied at different concentrations over time and excellent foam stability was obtained at a concentration of 0.075 %. Thus this novel class of surfactant may find applications as foam boosters in combination with other suitable surfactants.     

Photoelectrocatalytic Reduction of CO<Subscript>2</Subscript> to Chemicals via ZnO@Nickel Foam: Controlling C–C Coupling by Ligand or Morphology

The CO₂ reduction is a very attracting research field in the environmental, material and chemical sciences in light of the energy crisis and greenhouse effect. A new photoelectrocatalytic system composed of a photoanode BiVO₄ and a photocathode of nickel foam supported ZnO semiconductor was designed, assembled and applied to CO₂ reduction in water. The photocathodes with different morphology could be made from electrochemical deposition method and well characterized by SEM, UV–Vis, XRD, and XPS. The photoelectrocatalytic cell of ZnO/Ni-30|KHCO₃|BiVO₄ can produce ethanol and acetic acid in a rate of 12.5 µM h^?1 cm^?2 with 100% selectivity for C₂ product, attributing to the controlling of 3D-spaces of nanorod. The cell of A-ZnO/Ni-15|KHCO₃|BiVO₄ produces ethanol and acetic acid with 75% selectivity for C₂ product under 100 mW cm^?2 simulated sunlight irradiation, attributing to controlling of both amine ligand and morphology of ZnO, which reveal a new way to increase the selectivity of products.     

Supercritical antisolvent micronisation of synthetic all‐trans‐β‐carotene with tetrahydrofuran as solvent and carbon dioxide as antisolvent

BACKGROUND: Supercritical antisolvent (SAS) micronisation of synthetic trans ‐β‐carotene was studied using tetrahydrofuran (THF) as solvent and supercritical carbon dioxide (CO₂) as antisolvent, with the objective of increasing its bioavailability and facilitating its dispersion in oil and emulsion formulations as a result of its smaller particle size. The micronised powder was analysed by scanning electron microscopy and high‐performance liquid chromatography. Micronisation experiments were performed in order to evaluate the effects of temperature (308.15–333.15 K), pressure (6.5–13 MPa) and concentration of the liquid solution (6–9 g L^?1). The effect of the supercritical CO₂/THF flow ratio in the range between 4 and 44 (on a mass basis) was also analysed. Determinations of equilibrium concentrations of β‐carotene in the CO₂/THF mixture were also performed. RESULTS: The particle size obtained ranged from 1 to 500 µm, with mean particle diameters around 100 µm. Three types of morphology were found in the precipitated powder: crystalline with superficial pores and leaf‐like appearance; crystalline with regular shapes and blade‐like edges; and crystalline without superficial pores and leaf‐like apearance. The Peng–Robinson equation of state was used to calculate the density of the CO₂/THF binary mixture, and the solubility of β‐carotene in this mixture was correlated with its density. CONCLUSION: The use of the SAS technique to micronise β‐carotene proved to be efficient, and the absence of degradation in the micronised powder allows the industrial application of this technique. Copyright © 2008 Society of Chemical Industry     

Synthesis,Characterization and Properties of <Emphasis Type="Italic">N</Emphasis>-Alkyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-di(2-hydroxyethyl) Amine Oxides

N‐Dodecyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₂DHEAO) and N‐stearyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₈DHEAO) were synthesized with N‐alkyl‐diethanolamine and hydrogen peroxide. Their chemical structures were confirmed using ¹H‐NMR spectra, mass spectral fragmentation and FTIR spectroscopic analysis. It was found that C₁₂DHEAO and C₁₈DHEAO reduced the surface tension of water to a minimum value of approximately 28.75 mN m^?1 at concentration of 2.48 × 10^?3 mol L^?1 and 32.45 mN m^?1 at concentration of 5.21 × 10^?5 mol L^?1, respectively. The minimum interfacial tension (IFT_min) and the dynamic interfacial tension (DIT) of oil–water system were measured. When C₁₈DHEAO concentration was in the range of 0.1–0.5%, the IFT_min between liquid paraffin and C₁₈DHEAO solutions all reached the ultra‐low interfacial tension. Furthermore, their foam properties were investigated by Ross‐Miles method, and the height of foam of C₁₂DHEAO was 183 mm. It was also found that they showed strong emulsifying power.     

Spirulina platensis Culture with Flue Gas Feeding as a Cyanobacteria‐Based Carbon Sequestration Option

The scientific community is currently examining potential approaches in order to reduce the anthropical contributions to global warming. One approach is carbon capture and its storage, i.e., capturing CO₂ at its source and storing it indefinitely to avoid its release into the atmosphere. Conversion of CO₂ by microalgae or cyanobacteria is a sequestration option. Here, the application of an air‐lift reactor to flue gas treatment using cyanobacteria for the absorption of CO₂ was investigated, with the simultaneous abatement of NO_x. A Spirulina platensis culture was fed with CO₂ and NO_x, simulating a flue gas. The preliminary test yielded positive indications on the process feasibility, both in terms of cell productivity (86.8 mg L^–1d^–1) and CO₂ abatement (229 mg d^–1). Opportune dosages of flue gas used in fed‐batch test achieved a high abatement of CO₂ (407 mg d^–1), 90.0 % removal of NO_x, and a biomass production of 188.7 mg L^–1d^–1.     

Simultaneous oxidative conversion and CO2 or steam reforming of methane to syngas over CoO–NiO–MgO catalyst

CO₂ reforming, oxidative conversion and simultaneous oxidative conversion and CO₂ or steam reforming of methane to syngas (CO and H₂) over NiO–CoO–MgO (Co: Ni: Mg=0·5: 0·5:1·0) solid solution at 700–850°C and high space velocity (5·1×10⁵ cm³ g⁻¹ h⁻¹ for oxidative conversion and 4·5×10⁴ cm³ g⁻¹ h⁻¹ for oxy-steam or oxy-CO₂ reforming) for different CH₄/O₂ (1·8–8·0) and CH₄/CO₂ or H₂O (1·5–8·4) ratios have been thoroughly investigated. Because of the replacement of 50 mol% of the NiO by CoO in NiO–MgO (Ni/Mg=1·0), the performance of the catalyst in the methane to syngas conversion process is improved; the carbon formation on the catalyst is drastically reduced. The CoO–NiO–MgO catalyst shows high methane conversion activity (methane conversion >80%) and high selectivity for both CO and H₂ in the oxy-CO₂ reforming and oxy-steam reforming processes at ⩾800°C. The oxy-steam or CO₂ reforming process involves the coupling of the exothermic oxidative conversion and endothermic CO₂ or steam reforming reactions, making these processes highly energy efficient and also safe to operate. These processes can be made thermoneutral or mildly exothermic or mildly endothermic by manipulating the process conditions (viz. temperature and/or CH₄/O₂ ratio in the feed). © 1998 Society of Chemistry Industry     

An Alkaline Al–H2O2 Semi‐Fuel Cell Based on a Nickel Foam Supported Co3O4 Nanowire Arrays Cathode

The electrode of Co₃O₄ nanowire arrays directly grown on nickel foam is prepared via a facile one‐step method. The electrode is characterised by scanning and transmission electron microscopy and tested as the cathode of an Al–H₂O₂ semi‐fuel cell. We found that Co₃O₄ forms clusters of nanowires with length up to around 15 μm and diameter around 250 nm. The nanowire is composed of interconnected nanoparticles. Effects of H₂O₂ concentrations, catholyte KOH concentration, catholyte flow rate and operation temperature on the cell performance are investigated. The cell exhibited an open circuit voltage of 1.4 V, and peak power densities of 85 and 137 mW cm^–2 at 25 and 65 °C, respectively, while running on 0.4 mol L^–1 H₂O₂ at a flow rate of 80 mL min^–1.     

Experimental investigation and modelling of CO2-foam flow in heavy oil systems

In this work, the C_14-16 alpha olefin sulphonate (AOS) surfactant, octylphenol ethoxylate (TX-100), and methyl bis[Ethyl(Tallowate)]-2-hydroxyethyl ammonium methyl sulphate (VT-90) surfactant were selected as representatives of anionic, nonionic, and cationic surfactant to stabilize foam. The effects of surfactant concentration and gas/liquid injection rates on foam performance were examined by performing a series of oil-free foam flow tests by injecting CO₂ and a foaming surfactant simultaneously into sandpacks. Foam flooding was conducted as a tertiary enhanced oil recovery (EOR) method after conventional water flooding and surfactant flooding. Furthermore, a new method was proposed to determine the residual oil saturation. The foam stability in the presence and absence of heavy oil was studied by a comparative evaluation of the mobility reduction factor (F_MR) in both cases. The foam fractional flow modelling by Dholkawala and Sarma^[36] was modified based on experimental results obtained in this study. The range of the ratio of two important model parameters (C_g/C_c) at various foam qualities was determined and could be used for large-scale predictions. The results showed that during the oil-free foam displacement experiments higher foam apparent viscosities () were attained at lower gas flow rates and the maximum was attained at a total gas and liquid injection rate of 0.25 cm³/min with a gas fractional flow ratio of 0.8 for the foam in the absence of oil. The presence of oil reduced the foam mobility reduction factors (F_MR) to different degrees with F_MR-_{without oil} / F_MR-_{with oil} ranging from 4.25–13.69, indicating that the oil had a detrimental effect on the foam texture. The foam flooding successfully produced an additional 8.1–21.52 % of OOIP, which can be attributed to the combined effect of increasing the pressure gradient and oil transporting mechanisms.     

The pyrolysis behaviors of polyimide foam derived from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride/4,4′‐oxydianiline

The thermal stability and pyrolysis behaviors of polyimide (PI) foam derived from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA)/4,4′‐oxydianiline (4,4′‐ODA) in air and in nitrogen were studied. The decomposition products of PI foam were analyzed by thermogravimetry‐Fourier transform infrared spectroscopy (TG‐FTIR). Several integral and differential methods reported in the literatures were used in decomposition kinetics analysis of PI foam. The results indicated that the PI foam was easier to decompose in air than in nitrogen, with ～ 55% residue remaining in nitrogen versus zero in air at 800^oC. The main pyrolysis products were CO₂, CO, and H₂O in air and CO₂, CO, H₂O, and small organic molecules in nitrogen. The different dynamic methods gave similar results that the apparent activation energies, pre‐exponential factors, and reaction orders were higher in nitrogen than those in air. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optimization of growth operational conditions for CO2 biofixation by native Synechocystis sp.

BACKGROUND: A fundamental step in assessing the viability of a CO₂ biofixation system based on microalgae is to identify the maximum CO₂ biofixation yield that can be achieved for this microorganism when it is cultivated under optimum operational growth conditions. Response surface methodology was applied to determine optimum culture conditions for CO₂ biofixation by a recently isolated freshwater cyanobacterium Synechocystis sp. The strain was cultivated in a 1 L bubble column photobioreactor, in semicontinuous mode. RESULTS: Statistical analysis showed that temperature (from 22 to 39 °C), pH (from 7.2 to 8.8) and light intensity (from 928 to 2272 µE m^?2 s^?1), in addition to some of their interactions, had a significant effect on CO₂ biofixation. An optimum CO₂ biofixation rate of 2.07 gCO₂ L^?1culture day^?1 was found within the experimental region, at an average light intensity 686 µE m^?2 s^?1, pH 7.2 and temperature 35.3 °C. CONCLUSIONS: Based on these results, it is concluded that Synechocystis sp. presents a good tolerance to both high temperature and light intensity, characteristics which facilitate its application in outdoor CO₂ biofixation systems. Copyright © 2011 Society of Chemical Industry     

CO2‐Switchable Oil/Water Emulsion for Pipeline Transport of Heavy Oil

By mixing an aqueous solution of tertiary amine, N,N‐dimethylethanolamine (DMEA), with naphthenic acid (RCOOH) derived from heavy oil, a CO₂ switchable zwitterionic surfactant (RCOO^?DMEAH⁺) aqueous system was constructed. The CO₂ switchability of this zwitterionic surfactant was confirmed by visual inspection, pH measurements, and conductivity tests, i.e., the RCOO^?DMEAH⁺ decomposed into RCOOH, DMEAH⁺ and HCO₃^? after bubbling CO₂ through but switched back to its original state by subsequent bubbling N₂ through at 80 °C to remove the CO₂. The interfacial tension tests of heavy oil in DMEA aqueous solutions indicated that the solution containing 0.5 wt% of DMEA and 0.2 wt% of NaCl resulted in the lowest interfacial tension. The O/W emulsion formed when aqueous solutions of DMEA were used to emulsify heavy oil exhibited the best performance when the oil/water volume ratio, DMEA concentration, and NaCl concentration were 65:35, 0.5 and 0.2 wt%, respectively. The feasibility of pipeline transport of the O/W heavy oil emulsion was evaluated. The results illustrated that the demulsification of the O/W emulsion after transport could be easily realized by bubbling CO₂ through. Although demulsification efficiency still needs to be improved, the recycling of the aqueous phase after demulsification by removal of CO₂ looks promising.