Enhancing oil–solid and oil–water separation in heavy oil recovery by CO2-responsive surfactants

Interfacial properties are of critical importance to various separation applications. In heavy oil recovery, for example, a low oil–water interfacial tension (IFT) benefits the separation of heavy oil from their host rocks, which becomes problematic in the later stage of oil–water separation. CO₂-responsive surfactants were investigated to enhance the overall heavy oil recovery by switching their interfacial activity to the desired state in each stage. The surfactants at interfacially active state greatly enhanced the separation of heavy oil from hosting solids, as demonstrated by measuring contact angle and oil liberation using a custom-designed on-line visualization system. Meanwhile, the resulting heavy oil-in-water emulsions could also be easily demulsified by the bubbling of CO₂ gas, which switched off the interfacial activity of the surfactants. Furthermore, CO₂-responsive surfactants could be partially recycled in process water to improve sustainability, making CO₂-responsive surfactants to be promising chemical aids in heavy oil production and many other vital industries.     

己二酸对MEA吸收-解吸CO2过程的影响<

实验研究了己二酸对MEA水溶液吸收-解吸CO₂的影响。在0.4 mol·L-1 MEA的CO₂吸收富液解吸过程加入一定量的己二酸并分析了其对CO₂解吸能耗和解吸速率的影响,发现解吸速率明显升高,析出单位体积CO₂的能耗显著降低;对解吸还原后的贫液进行了CO₂二次吸收的实验,发现因加酸引起的CO₂二次吸收量变化小于7%;为去除不确定因素对CO₂相似文献   

Multifunctional CO2-switchable polymers for the flocculation of oil sands tailings

A series of multifunctional homopolymer and copolymer of 2-dimethylamino ethyl methacrylate (DMAEMA) and N-isopropyl acrylamide (NIPAM) were designed and used to flocculate oil sands mature fine tailings (MFTs). Carbon dioxide (CO₂) protonated the tertiary amine groups of P(DMAEMA) and P(DMAEMA–NIPAM) making their chains positively charged. The pH sensitivity of these polymers favored the flocculation of the negatively charged clays in MFT due to charge neutralization. Three different polymers, P(DMAEMA), P(NIPAM₃₃–DMAEMA₆₇), and P(NIPAM₆₇–DMAEMA₃₃) were synthesized via aqueous free-radical polymerization and used to flocculate MFT in the presence of CO₂. Experimentally, CO₂ was introduced in the system in three different ways: (1) CO₂ was first bubbled into polymer solution, then the polymer solution was added to MFT, (2) CO₂ was first bubbled into MFT and then the CO₂-free polymer solution was added to MFT, and (3) both polymers and MFT were bubbled with CO₂ separately, then mixed together. We compared the effects of the method of CO₂ addition, copolymer composition, and polymer molecular weight on MFT flocculation performance. Our results indicate that CO₂-switchable polymers can be employed to enhance the dewatering of challenging wastewaters such as oil sands tailings. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47578.     

ABSORPTION AND DESORPTION OF CO2 BY AQUEOUS SOLUTIONS OF STERICALLY HINDERED 2-AMINO-2-METHYL-1-PROPANOL IN HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTORS

To understand the behavior of separation of CO₂ from CO₂-N₂ mixtures using a hydrophobic microporous hollow fiber (polytetrafluoroethylene) contained gas-liquid contactor with aqueous solutions of 2-amino-2-methyl-l-propanol (AMP) as liquid media in the shell side, first, the absorption of dilute CO₂ into aqueous AMP solutions and the desorption of CO₂ from CO₂-loaded AMP solutions into N2 stream were investigated separately for various combinations of operational variables. Secondly, the simultaneous absorption and desorption in a single unit was performed to check the possibility of a long-term continuous operation. The resistance to diffusion in the hollow fiber phase during absorption amounted to ca. 86% of the total resistance, and slightly decreased with increasing AMP concentration. The AMP solution partially leaks into pores of the hollow fiber, and both the diffusion and chemical reaction of dissolved CO₂ in the liquid-filled pores under the slow-reaction regime mainly control the overall absorption rate. If the physical diffusion in the liquid-filled part of the pore completely controlled the absorption process in the present hollow fiber contactor, the length of the liquid-filled part would be evaluated to be 72 ~ 108 urn as compared to the total pore length of 500 um. The desorption rate was found to be independent of the gas velocity in the lumen side. The desorption process can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Simultaneous absorption and desorption process in a single contactor was found to be kept in a stable state at least until 20?h.     

ABSORPTION OF CO2 INTO AQUEOUS SOLUTIONS OF STERICALLY HINDERED METHYL AMINOETHANOL USING A HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTOR

The absorption of dilute CO₂ into aqueous solutions of sterically hindered 2-methyl aminoethanol (MAE) and the desorption of CO₂ from CO₂-loaded MAE solutions into N₂ stream were investigated separately for the various combinations of operational variables, using a hydrophobic microporous hollow fiber (polytetrafluoroethylene, PTFE) contained gas-liquid contactor with aqueous solutions of MAE as liquid media in the shell side at 30°C. The absorption of CO₂ in this contactor is governed by resistance in the liquid and hollow fiber phases. The resistance to diffusion in the hollow fiber phase amounts to 76–80% of the total resistance. Nevertheless, the absorption rates of CO₂ into aqueous MAE solutions in this contactor are higher than those into aqueous solutions of sterically hindered 2-amino-2-methyl-1-propanol (AMP) in the stirred tank with a plane unbroken gas-liquid interface. The process of desorption of CO₂ from CO₂-loaded MAE solutions can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Both absorption and desorption rates under the simultaneous absorption-desorption operation in a single unit tend to approach the respective constant values as process time elapses. The total absorption rate here seems to be almost balanced with the total desorpion rate at the constant mass transfer rate periods.     

Kinetics of carbon dioxide absorption and desorption in aqueous alkanolamine solutions using a novel hemispherical contactor—II: Experimental results and parameter estimation

In Part 1 of this paper, detailed design of the hemispherical apparatus and a rigorous mathematical model applied to CO₂ absorption and desorption in and from aqueous alkanolamine solutions was presented with some preliminary results. This part of the paper provides detailed results on CO₂-amine kinetics under absorption and desorption conditions and present new estimates of the kinetic parameter for aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), methyl-diethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP). The absorption experiments were conducted at near atmospheric pressure with pure humidified CO₂ at 293-323 K using initially unloaded solutions. The desorption experiments were performed at 333-383 K for CO₂ loadings between 0.02 to 0.7 mol of CO₂ per mole of amine using humidified nitrogen gas as a stripping medium at total system pressure ranging from 110 to 205 kPa.The new rigorous mathematical model discussed in Part 1 was used in conjunction with a non-linear regression technique to estimate the kinetic parameters. In all cases, the new model predicts the experimental results well. Also, the new results clearly demonstrate that the theory of absorption with reversible chemical reaction could be used to predict desorption rates. The zwitterion mechanism adequately describes the reactions between CO₂ and carbamate forming amines such as MEA, DEA and AMP. The reactions between CO₂ and aqueous MDEA solutions are best described by a base-catalyzed hydration reaction mechanism. The kinetic data obtained show that desorption experiments could be used to determine both forward and backward rate constants accurately. The absorption experiments, on the other hand, could only be used to determine forward rate constants. It was found that at all operating conditions used in this study, the kinetic parameters for MEA, DEA and AMP obtained using absorption data could not be extrapolated to predict desorption rates. However, for MDEA, these data could be used successfully to obtain reasonably good predictions of desorption rates.     

Permeability reduction by asphaltenes and resins deposition in porous media

The deposition of crude oil polar fractions such as asphaltenes and resins in oil reservoir rocks reduce considerably the rock permeability and the oil production. In the present work, a crude oil and various core samples were extracted from Rhourd–Nouss (RN) reservoir rock. Afterwards, core flow experiments were carried out in the laboratory to investigate permeability reduction that causes formation damage. The core permeability damage was evaluated by flooding Soltrol, through the sample and measuring the solvent permeabilities, K_i and K_f, respectively, before and after injection of a given pore volume number of the crude oil.The data indicate that upon flooding the crude oil through the porous medium, considerable permeability reduction, expressed as the ratio (K_i − K_f)/K_i, and ranging from 72.4% to 98.3% were observed. The permeability reduction is found to result from irreversible retention of asphaltenes and resins in the porous core sample. However, no correlations could be established between the depth of the well, the core porosity, the core mineral compositions determined by X-ray analysis, and the permeability damage factors. In addition, effluents flowing away from RN wells were collected and analysed at various periods, after carrying out aromatic solvents squeezes. The amount of saturates, aromatics, resins, and asphaltenes (SARA analysis), of the crude oil, the deposited crude oil fraction, and the effluent’s residues were measured and compared. The asphaltenes weight percent was found to increase from 1.56% for the crude oil to 11.42% for the deposited oil fraction, and was in the range 1.37–2.36% for the effluent’s residues. Such results indicate that the deposited oil fraction and the effluent’s residues consist mainly of asphaltenes and resins.     

Designing amino-based ionic liquids for improved carbon capture: One amine binds two CO2

Generally, amine group captures CO₂ according to 2:1 or 1:1 stoichiometry. Here, we report a kind of improved carbon capture using amino-functionalized ionic liquids (ILs) through 1:2 stoichiometry. A serial of amino-functionalized ILs various with basicity and steric hindrance of anion were designed, prepared, and applied in CO₂ capture. Through a combination of absorption experiment, quantum chemical calculation, spectroscopic investigation and calorimetric method, the results indicated that one amine group could bind two CO₂ through proton transfer (PT) process and intramolecular hydrogen bond formation, which leading to enhanced capacity that breaks through equimolar. The basicity and steric hindrance of anion play a significant role in promoting amine group to capture two CO₂. [P₆₆₆₁₄]₂[Asp] with dual anion was further designed and synthesized to promote PT process, which showed high capacity of 1.96 mol/mol IL at 30°C and 1 atm as well as excellent reversibility. © 2018 American Institute of Chemical Engineers AIChE J, 65: 230–238, 2019     

Temperature influence and CO2 transport in foaming processes of poly(methyl methacrylate)–block copolymer nanocellular and microcellular foams

Fabricated by high-pressure or supercritical CO₂ gas dissolution foaming process, nanocellular and microcellular polymer foams based on poly(methyl methacrylate) (PMMA homopolymer) present a controlled nucleation mechanism by the addition of a methylmethacrylate–butylacrylate–methylmethacrylate block copolymer (MAM), leading to defined nanocellular morphologies templated by the nanostructuration of PMMA/MAM precursor blends. Influence of the CO₂ saturation temperature on the foaming mechanism and on the foam structure has been studied in 90/10 PMMA/MAM blends and also in the neat (amorphous) PMMA or (nanostructured) MAM polymers, in order to understand the role of the MAM nanostructuration in the cell growth and coalescence phenomena. CO₂ uptake and desorption measurements on series of block copolymer/homopolymer blend samples show a competitive behavior of the soft, rubbery, and CO₂-philic block of PBA (poly(butyl acrylate)) domains: fast desorption kinetics but higher initial saturation. This competition nevertheless is strongly influenced by the type of dispersion of PBA (e.g. micellar or lamellar) and a very consequent influence on foaming.CO₂ sorption and desorption were characterized in order to provide a better understanding of the role of the block copolymer on the foaming stages. Poly(butyl acrylate) blocks are shown to have a faster CO₂ diffusion rate than poly(methyl methacrylate) but are more CO₂-philic. Thus gas saturation and cell nucleation (heterogeneous) are more affected by the PBA block while cell coalescence is more affected by the PMMA phases (in the copolymer blocks + in the matrix).     

Absorption and desorption of carbon dioxide in several water types

This study investigated the effect of water type on the rate of CO₂ transfer from/to an aqueous phase with varying degree of water salinity. The absorption and desorption experiments were conducted on reverse osmosis product, brackish well, and brackish water reverse osmosis reject waters as well as seawater in a mechanically agitated tank. Results show that the direction of mass transfer has a major impact on the value of the volumetric mass transfer coefficient, k_La, with the absorption experiments always rendering higher values. Furthermore, k_La values always decreased with salinity in both absorption and desorption experiments until a certain critical salinity value was reached, beyond which mass transfer increased again. However, k_La values were found to decrease continuously with an increase in the water alkalinity in absorption experiments, while no clear conclusion could be drawn for the alkalinity effect in the case of desorption experiments. These observations suggest that the effect of alkalinity should be further investigated to elucidate its impact along with the salinity on the volumetric mass transfer rate.     

Analyzing the energy intensity and greenhouse gas emission of Canadian oil sands crude upgrading through process modeling and simulation

This paper presents an evaluation of the energy intensity and related greenhouse gas/CO₂ emissions of integrated oil sands crude upgrading processes. Two major oil sands crude upgrading schemes currently used in Canadian oil sands operations were investigated: cokingbased and hydroconversion-based. The analysis, which was based on a robust process model of the entire process, was constructed in Aspen HYSYS and calibrated with representative data. Simulations were conducted for the two upgrading schemes in order to generate a detailed inventory of the required energy and utility inputs: process fuel, steam, hydrogen and power. It was concluded that while hydroconversion-based scheme yields considerably higher amount of synthetic crude oil (SCO) than the cokerbased scheme (94 wt-% vs. 76 wt-%), it consumes more energy and is therefore more CO₂-intensive (413.2 kg CO₂/m³ SCO vs. 216.4 kg CO₂/m³ SCO). This substantial difference results from the large amount of hydrogen consumed in the ebullated-bed hydroconverter in the hydroconversion-based scheme, as hydrogen production through conventional methane steam reforming is highly energy-intensive and therefore the major source of CO₂ emission. Further simulations indicated that optimization of hydroconverter operating variables had only a minor effect on the overall CO₂ emission due to the complex trade-off effect between energy inputs.     

Structure,morphology, thermal,and sorption characteristics of epoxidized natural rubber conjugated spent coffee via one-pot synthesis

The present work highlights the preparation of the epoxidized natural rubber conjugated spent coffee biocomposites (ENR-g-SC) via one-pot synthesis to control petroleum oil spills. The structural determination of the spent coffee grafted epoxidized natural rubber (ENR-g-SC) was confirmed through FTIR and ¹H-NMR spectroscopic analyses. The thermal performance, tensile tests, and morphological properties of the synthesized (ENR-g-SC) biocomposites were performed. The data revealed that ENR-g-SC biocomposite with 20 phr of spent coffee (SC) exhibited the highest tensile properties due to maximal chemical linkages of spent coffee and epoxide groups in ENR. The epoxidized natural rubber conjugated spent coffee copolymers were evaluated as oil sorbers for oil absorbency applications in chloroform, toluene, and 10% crude petroleum diluted with toluene. The data revealed that the oil absorbency increased slightly with chloroform or toluene instead of 10% crude oil diluted with toluene. Furthermore, swelling and network parameters including the maximum oil absorbency (Q_max), swelling rate constant (k), polymer-solvent interaction (χ), effective crosslink density (ύe), equilibrium modulus of elasticity (G_T), and average molecular weight between crosslinks (M_c) and theoretical crosslink density (ύ_t) were determined, and correlated to the efficiency of the synthesized epoxidized natural rubber conjugated spent coffee.     

Fabrication of PEI-grafted porous polymer foam for CO2 capture

A polymer foam material with both the open-cell porous structure and the polyethylenemine (PEI)-grafted inner face was constructed for CO₂ capture. The porous poly(tert-butyl acrylate) foam was first prepared via a concentrated emulsion polymerization, and then the carboxyl groups were introduced on the interface of porous polymer after the hydrolysis reaction. Subsequently, the surface of the foam was grafted with PEI, and finally the PEI-grafted porous polymer foam designed as a CO₂ capture material was obtained. The structures of the foams were characterized by infrared spectroscopy, EDS, and SEM. The CO₂ adsorption properties were measured by adsorption/desorption cycles. As a result, the polymer foam contained a large number of amine groups (13.9 wt % N), and therefore possessed a high CO₂ adsorption capacity (5.91 mmol g⁻¹ at 40°C and 100 kPa). In addition, they also exhibited high CO₂ adsorption rate, good selectivity for CO₂-N₂ separation, and good stability according to CO₂ cyclic adsorption/desorption test. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47844.     

Fabrication and characterization of poly(vinylidene fluoride)–polytetrafluoroethylene composite membrane for CO2 absorption in gas–liquid contacting process

The wetting resistance of poly(vinylidene fluoride) (PVDF) membrane is a critical factor which determines the carbon dioxide (CO₂) absorption performance of the gas–liquid membrane contactors. In this study, the composite PVDF–polytetrafluoroethylene (PTFE) hollow fiber membranes were fabricated through dry-jet wet phase-inversion method by dispersing PTFE nanoparticles into PVDF solution and adopting phosphoric acid as nonsolvent additive. Compared with the PVDF membrane, the composite membranes presented higher CO₂ absorption flux due to their higher effective surface porosity and surface hydrophobicity. The composite membrane with addition of 5 wt % PTFE in the dope gained the optimum CO₂ absorption flux of 9.84 × 10⁻⁴ and 2.02 × 10⁻³ mol m⁻² s⁻¹ at an inlet gas (CO₂/N₂ = 19/81, v/v) flow rate of 100 mL min⁻¹ by using distilled water and aqueous diethanolamine solution, respectively. Moreover, the 5% PTFE membrane showed better long-term stability than the PVDF membrane regardless of different types of absorbent, indicating that polymer blending demonstrates great potential for gas separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47767.     

Effect of addition of weak acids on CO<Subscript>2</Subscript> desorption from rich amine solvents

Experiments were conducted to study the effect of addition of four weak acids (adipic, suberic, phthalic and sebacic acids) on the regeneration of three types of CO₂-loaded rich solvents (Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA)). It was found that CO₂ could be released faster and in a larger quantity when the amount of acid added to the solvent was increased while other desorption conditions were maintained unchanged. Adipic acid appeared to be more effective than phthalic, suberic and sebacic acids in enhancing solvent regeneration rate. Among the three amines investigated, MEA had the highest CO₂ desorption rate, while DEA saved the most energy. The effect of adipic acid residue in the MEA solvent on CO₂ absorption was also investigated. The residue acid reduced the absorption capacity of the MEA solvent significantly when the solvent concentration was low and slightly when the concentration was high.     

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.     

Screening test for aqueous solvents used in CO2 capture: K2CO3 used with twelve different rate promoters

K₂CO₃ solution is widely used in the CO₂-capture industry. In particular, it has advantages for treating CO₂ in flue gas under high-temperature and high-pressure conditions. However, it has a lower CO₂-loading capacity and slower absorption kinetics than those of amines, which are its major disadvantages. Thus, in this study, we investigated ten loading-rate promoters, five primary amines and five secondary amines, to develop higher CO₂-loading capacity and faster absorption kinetics. The screening tests of the absorption and desorption processes were conducted at 70 °C and 90 °C, respectively. Based on the results, we concluded that all the amines used improved the CO₂-loading and absorption kinetics compared with the use of K₂CO₃ alone. At a certain value CO₂ loading, the respective performance of the primary and secondary amines was twice and thrice better, respectively, than the neat K₂CO₃ solution. Thus, secondary amines had superior absorption capacity and absorption/desorption rate compared to primary amines. Among the secondary amines, pipecolic acid, sarcosine, and isonipecotic acid were determined as the most effective absorption rate promoters.     

Supercritical fluid extraction of peach (Prunus persica) almond oil: Kinetics, mathematical modeling and scale-up

Peach almonds contain oil with important therapeutic and nutritional properties due to the presence of unsaturated fatty acids, high content of oleic acid and other substances. In this study, peach almond oil was obtained by means of supercritical fluid extraction (SFE), with yield up to 24% w/w. The objective of this work was to evaluate the effect of the operation variables in the process kinetics in order to define scale-up parameters, like extractor volume and solvent flow rate. In spite of the importance for industrial application, the definition of a scale-up methodology is difficult. Therefore, the main goal of this work was to study the kinetic aspects of the SFE by modeling the extraction curves and, with these results, suggests a scale-up methodology. The parameters evaluated were extraction pressure, CO₂ flow rate and particle size. The mass transfer models used to describe the extraction curves were logistic model, diffusion model and Sovová model. Four scale-up methodologies, based on mass transfer mechanisms, were applied. The results indicate the best curve fitting by means of Sovová’s model, while the best scale-up criterion was maintaining the ratio Q_CO2/M (solvent flow rate/raw material mass) constant. This study also indicated the convection as the dominant mass transfer mechanism, while the diffusion was the limiting factor. Moreover, the SFE of peach almond oil could be predicted by the scale-up method used.     

Thermo- and CO2-triggered swelling polymer microgels for reducing water-cut during CO2 flooding

CO₂ has been widely used in the process of enhanced oil recovery (EOR) over decades. However, the heterogeneity of oil reservoirs renders CO₂ to flow preferentially into highly permeable zones, leaving tight areas unswept with oil unrecovered in these areas. While conventional water-swelling gels were used for blocking the “channeling” path, most of them experience the risks of shrinkage under high temperature and CO₂-induced acidic environment. Here, we developed double swelling smart polymer microgels (SPMs) triggered by both heat and CO₂. Such SPMs were prepared by copolymerization of acrylamide (AAm) in combination with N,N-2-(dimethylamino)ethyl methacrylate (DMAEMA) and [2-(methacryloyloxy) ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), and with N,N′-methylene bisacrylamide (MBA) as the crosslinker. These SPMs swell when temperature is higher than 65 °C or in the presence of CO₂, with an ameliorative salinity tolerance ability. Artificial sand pack flooding carried by SMPs at 65 °C showed an elevated plugging efficiency at around 97% under a simulated pressurization at 5 MPa, proposing a valid candidate for future EOR applications during CO₂ flooding. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48305.     

Catalytic desorption of CO2-loaded solutions of diethylethanolamine using bentonite catalyst

The absorption of CO₂ gas into aqueous alkanolamine solutions is the most advanced CO₂ separation technology and a key challenge in this technique is the energy-intensive process of solvent regeneration. The tertiary amine N,N′-diethylethanolamine (or DEEA) is a candidate CO₂-capturing solvent with potential. To improve the energy efficiency of regeneration of DEEA, several catalysts were used for desorbing CO₂ from loaded solutions of DEEA (2.5 M) at T = 363 K. Desorption trials were conducted in batch mode. The initial CO₂ loading varied in the 0.3–0.35 mol CO₂/mol DEEA range. The performance was analyzed by calculating the rate of CO₂ desorption, cyclic capacity, and reduction in sensible energy. The amount of thermal energy needed for amine regeneration was significantly lowered by using nine transition metal oxide catalysts and the hierarchy was as follows: Al₂O₃ < MoO₃ < V₂O₅ < TiO₂ < MnO₂ < ZnO < Cr₂O₃ < SiO₂ < ZrO₂. Among the metal oxides, Al₂O₃ increased desorption efficiency compared to blank runs by 89%. A clay-based powder bentonite was also used as catalyst and its efficacy was compared with the metal oxides. This cheap and easily available bentonite catalyst was tuned through simple ion-exchange with four acids (HCl, H₃PO₄, HNO₃, and H₂SO₄). Upon treatment with H₂SO₄, bentonite remarkably increased desorption efficiency by 100%. Furthermore, bentonite catalyst treated with sulphuric acid (denoted here as Bt/H₂SO₄) was characterized by Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectrometery (FTIR), X-ray diffraction (XRD), and ammonia temperature-programmed desorption (NH₃-TPD). In this way, a comprehensive study on catalytic desorption of DEEA was performed.