Sodium Naphthenates Research Articles

Removal of Excess Alkali from Sodium Naphthenate Solution by Electrodialysis Using Bilayer Membranes for Subsequent Conversion to Naphthenic Acids.

The processing of solutions containing sodium salts of naphthenic acids (sodium naphthenate) is in high demand due to the high value of the latter. Such solutions usually include an excessive amount of alkali and a pH of around 13. Bipolar electrodialysis can convert sodium naphthenates into naphthenic acids; however, until pH 6.5, the naphthenic acids are not released from the solution. The primary process leading to a decrease in pH is the removal of excess alkali that implies that some part of electricity is wasted. In this work, we propose a technique for the surface modification of anion-exchange membranes with sulfonated polyetheretherketone, with the formation of bilayer membranes that are resistant to poisoning by the naphthenate anions. We investigated the electrochemical properties of the obtained membranes and their efficiency in a laboratory electrodialyzer. Modified membranes have better electrical conductivity, a high current efficiency for hydroxyl ions, and a low tendency to poisoning than the commercial membrane MA-41. We propose that the primary current carrier is the hydroxyl ion in both electromembrane systems with the MA-41 and MA-41M membranes. At the same time, for the modified MA-41M membrane, the concentration of hydroxyl ions in the anion-exchanger phase is higher than in the MA-41 membrane, which leads to almost five-fold higher values of the specific permeability coefficient. The MA-41M membranes are resistant to poisoning by naphthenic acids anions during at least six cycles of processing of the sodium naphthenate solution.

Synthesis and Application of New Multibranched–Linear–Multibranched Fluorinated Copolymer as Demulsifiers for Naphthenic Compounds Stabilized Emulsion

• A series of novel fluorinated copolymer with multibranched–linear–multibranched structure were prepared. • The demulsification process of the copolymers in naphthenic acids and sodium naphthenates stabilized emulsions were evaluated. • The relationship between polymer structure and demulsification performance was discussed. To deal with the demulsification of emulsion stabilized by naphthenic compounds, a series of multibranched–linear–multibranched (MLM) copolymer were designed and synthesized. The hydrophilic core with MLM structure is constructed by anionic ring-opening multibranching polymerization (ROMBP) of glycidol with poly (ethylene glycol). The amphophobic arms are grafted by atom transfer radical polymerization (ATRP) of 2, 2, 2-trifluoroethyl methacrylate (TFEMA). The demulsification performance of the MLM copolymer in n-octane/water emulsion stabilized by naphthenic acids (NAs) and sodium naphthenates (Na-NAs) were evaluated. The influences of copolymer dosage, temperature and Na-NAs/NAs ratio on the demulsification efficiency were investigated in detail. Compared with the blank sample settled for 90 min, the fluorinated MLM copolymer with medium HLB value promoted the demulsification efficiency from 50% to 92%. By analyzing the correlation between the polymer structure and demulsification performance, it can be considered that the PEG segment improved the low solubility of the fluorinated copolymer caused by the solvophobic nature of fluorinated groups. The amphophobic effect of the fluorinated group not only accelerates the diffusion process of polymer molecules from the bulk to the interface, but also reduces the rigidity of the interface film by repelling the original interface active material, and produces effective demulsification.

Application of Scheludko–Exerowa thin liquid film technique to studies of petroleum W/O emulsions

This paper is a review of our work with Scheludko–Exerowa thin liquid film—pressure balance technique TLF-PBT, the first systematic application of the technique to petroleum systems. New insights were gained in understanding the behavior of petroleum emulsions. We have observed new phenomena in foam films stabilized with sodium naphthenates: long range foam film stratifications and step-wise film thickening at constant capillary pressure. Our modification of TLF-PBT cell allows probing water-in-oil emulsion films with electrical signal, a new technique to study water-in-oil emulsions.

The role of naphthenates and kaolinite in toluene and toluene–bitumen emulsions

The study of toluene emulsions is relevant to understand the behavior, and the separation of solvent-diluted bitumen emulsions. Previous studies of similar systems have revealed that the presence of naphthenates, particles – specifically kaolinite- and asphaltenes can play an important role in the formation and stability of solvent-diluted bitumen emulsions. The objective of this work was to elucidate the relative importance of these factors. It was determined that in bitumen-free systems the presence of sodium naphthenates facilitates the entrapment of kaolinite in the emulsion and its segregation at the oil–water interface, which contributes to stabilize the emulsions. However, bitumen components (asphaltenes, resins, and other components) were shown to be more interfacially active than naphthenate-adsorbed kaolinite, resulting in the rejection of kaolinite from the emulsion. In naphthenate-adsorbed kaolinite emulsions, the presence of bitumen components is the dominant factor in determining the level of particles and water entrapped in the emulsion. Bitumen-coated kaolinite emulsions behaved in the same way as bitumen-free systems, suggesting that as long as the particle is pre-adsorbed with the dominant surface active species, particles can contribute to stabilize emulsions.

Tailings Pond Surfactant Analogues: Effects on Toluene-Diluted Bitumen Drops in NaHCO3/K2CO3 Solution. Part 1: Dynamic Interfacial Tension

The interfacial properties and stability of the bitumen as films over free water or as droplets in process water require attention to aid the design of bitumen recovery methods that foster environmental sustainability. This paper addresses the nature and consequences of surfactant interactions with toluene-diluted bitumen (AOSB) in simulated tailings water. The interactions were monitored as functions of time (t) through measurements of dynamic interfacial tension σ(t). We compared the effects of adsorption of two simple surfactants, hexanoic acid (C5H11COOH or HAA), and the other having 3-cyclopentylpropionic acid (C5H9CH2CH2COOH or CPPA), with complex sodium naphthenates (SNs). The surfactants were adsorbed at the toluene/water interface as a control, and the Gibbs surface excess, the area per molecule, and critical breakpoint concentrations were determined. These data were used to select both surfactant concentrations for adsorption at the diluted bitumen/water interface and pH. σ(t) versus (t) was mea...

Tailings Pond Surfactant Analogues: Effects on Toluene-Diluted Bitumen Drops in NaHCO3/K2CO3 Solution. Part 2: Dilational Interfacial Viscoelasticity

In this two-part work, we used dilational interfacial rheometry to study the interfaces associated with diluted bitumen in simulated pond water as a function of pH, for three different surfactants: two simple carboxylic acids, one with a straight chain and one having a ring in the tail, and the more complex sodium naphthenates. In part 1 (10.1021/ef400376v), dynamic interfacial tension as a function of time was used to measure adsorption. In part 2, described in the present paper, interfacial dilational rheology was studied as a function of oscillation frequency for three different concentrations of the three surfactants adsorbed at the interface between buffer and toluene-diluted bitumen. The concentrations used were selected on the basis of results from part 1 (10.1021/ef400376v). Our results show that interfacial viscoelasticity depends upon not only the tail complexity in the surfactants but also the surfactant concentration and buffer pH. The adsorbed naphthenates were synergistic with interfacially ...

Interactions of divalent cations with tetrameric acid aggregates in aqueous solutions

Interactions in aqueous solutions between a tetrameric naphthenic acid in sodium salt (BP10Na4) and divalent Mg2+ and Ca2+ cations were investigated by isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). Colloidal aggregation of the tetrameric sodium naphthenates to vesicles and micelles enhances its binding with divalent cations. In vesicle systems, Ca2+ was found to bind first with carboxylate groups located at the external water/lipid interface of vesicles. The cations then diffuse through the membrane to interact with the inner carboxylate groups. Higher Ca2+ concentration and higher salinity gradients enhance cation diffusion. Under solution chemistry conditions where micelle dominates, Ca2+ reacts only with outer carboxylate groups of BP10Na4 without any significant cation diffusion through the aggregates. The binding of calcium with sodium naphthenate is an entropy-driven process where entropy gain comes from the dehydration of both cations and carboxylate groups of BP10Na4. The affinity of Mg2+ to BP10Na4 is much weaker than Ca2+ due to its stronger hydration and hence larger size of hydrated magnesium ions than hydrated calcium ions.

Salting-out effects on the characterization of naphthenic acids from Athabasca oil sands using electrospray ionization

There is growing interest in the mass spectrometric characterization of oil sands acids present in natural waters and contaminated soils. This interest stems from efforts to isolate the principal toxic components of oil sands acid extractable organics in aquatic environment. Salting-out effects are demonstrated for nanospray ionization mass spectra of Athabasca oil sands acid extractable organics (naphthenic acids), using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The differences in spectra obtained for the sodium naphthenates in dichloromethane/acetonitrile cosolvents compared to spectra obtained in the absence of saturated sodium chloride salts, are used here as a surrogate to indicate the more bioavailable or toxic components in natural waters. Whereas, monocarboxylic compounds (CnH2n+ZO2) were prevalent in the Z =−4, −6, and −12 (2, 3 and 6-ring naphthenic acids respectively) family in the carbon number range of 13 to 19 in the dichloromethane/acetonitrile cosolvent systems, salting-out effects resulted in a general enhancement of Z =−4 species, relative to others. Likewise, the shift in relative intensities of species containing O1, O3, O4, O2S and O3S was dramatic for systems with and without saturated salts present. The O4 and O3S species for example, were prevalent in the dichloromethane/acetonitrile cosolvent but were non-detected in the presence of saturated salts. Interactions of oil sands acids with salts are expected to occur in oil sands processed waters and natural saline waters. As evident by the distribution of species observed, salting-out effects will play a major role in limiting the bioavailability of oil sands acids in aquatic systems.

Evaluating the hydrophilic–lipophilic nature of asphaltenic oils and naphthenic amphiphiles using microemulsion models

Asphaltenes and naphthenic acid derivatives, which are polar and surface-active species, are known to interfere with the recovery of heavy crude oil by promoting the formation of stable emulsions. In this study, previously established microemulsion phase behavior models were applied to quantify the hydrophilic–lipophilic nature of asphaltenic oils (bitumen, deasphalted bitumen, asphalt, naphthalene) and surface-active species found in heavy oils (naphthenic compounds and asphaltenes). For the test oils, the equivalent alkane carbon number (EACN) was determined by evaluating the “salinity shifts” of microemulsions formulated with a reference surfactant (sodium dihexyl sulfosuccinate – SDHS) and a reference oil (toluene) as a function of test oil volume fraction. Similarly, the characteristic curvature ( C C ) of surface-active species was determined by evaluating the salinity shifts as a function of the molar fraction of the surface-active species in mixture with SDHS. As a part of the oil phase, asphaltenes and asphaltene-like species are highly hydrophilic, which lead to low EACN values despite their large molecular weight. As a surface-active material, asphaltenes are hydrophobic species that lead to the formation of water-in-oil emulsions. Naphthenates, particularly sodium naphthenates, are highly hydrophilic compounds that lead to the formation of oil-in-water emulsions. These hydrophilic–lipophilic characterization parameters, and the methods used to determine them, can be used in the future to understand the phase behavior of complex oil–water systems.

Chemical Speciation of Calcium and Sodium Naphthenate Deposits by Electrospray Ionization FT-ICR Mass Spectrometry

Calcium and sodium naphthenates are solid deposits and emulsions formed by the interaction of naphthenic acids with divalent (Ca2+, Mg2+) or monovalent (Na+, K+) ions in produced waters. Calcium naphthenate formation, an interfacial phenomenon, is thought to depend largely on tetraprotic naphthenic acids known as “ARN” acids (∼C80) in the crude oil, whereas sodium naphthenates originate from lower molecular weight (C15 to C35) monoprotic naphthenic acids. Here we present detailed chemical heteroatom class composition analyses of calcium and sodium naphthenates from the field based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In all cases, calcium naphthenate deposits consist predominately of tetraprotic acids with a C80 hydrocarbon skeleton whereas sodium naphthenate emulsions consist mainly of specific monoprotic saturated carboxylic acids. Furthermore, low molecular weight tetraprotic (ARN) acids with C60−77 hydrocarbon skeletons were identified in the calc...

Selective Creaming: A Novel Technique to Isolate Interfacial Organics and Mineral Solids from Water-in-Oil Emulsions

Characterization of interfacial materials isolated from water-in-crude oil emulsions is a useful tool to reveal the emulsion stability mechanisms. “Heavy water (D 2O) method” is a technique used successfully in the past to isolate the interfacial organics from laboratory-made emulsions containing D 2O droplets. However, isolation of interfacial mineral solids is beyond its capability. The “selective creaming” method proposed in this paper is able to overcome this limitation and is suitable for oilfield/plant emulsions containing H 2O droplets as well. The principle is to modify the density of the hydrocarbon phase first and place a layer of clean D 2O on top. The interfacial material-carrying H 2O droplets are pushed upward through the D 2O layer in a centrifuge. Non-interfacial organics are retained beneath the D 2O layer, and non-interfacial solids sink to the bottom of the hydrocarbon phase. Both contaminants are “selectively” removed from the isolated interfacial materials. This method was applied to a complex industrial system, i.e., water-in-diluted Athabasca bitumen froth emulsion. The isolated interfacial organics and solids were characterized using various analytical techniques. The solids concentration on the interface was determined to be 20.9 wt %. The asphaltene concentration was less than 32 wt %. The results suggest that interfacial organics as a whole are the main emulsion stabilizer, but no single organic species dominates the interface. Many other properties of the interfacial materials are consistent with the literature data based on model emulsion studies or bulk solids fractionation. However, the present interfacial sample contains virtually no sodium naphthenates and contains large amounts of 1−5 μm clay platelets, which are significantly larger in size than previous findings. The discrepancies could be due to the differences in sample sources and isolation procedures. Results from this work are likely more relevant to the commercial operations.

Friberg Correlations in Oil Recovery

The current status of “Friberg correlations” is reviewed and illustrated in model and industrial systems relevant to the oil industry. For a model naphthenic acids/sodium hydroxide two‐phase system, a third, liquid crystal (LC), phase is formed at the o/w interface from sodium naphthenates, which is produced in situ by a chemical reaction. This LC layer spreads spontaneously on the o/w interface, thus it is a “surface‐active phase” in the sense defined by R. G. Laughlin. When this additional phase covers the oil/water interface it modifies the transport processes throughout the interface. The LC layers on water droplets may be one of the reasons for the high water‐in‐oil emulsion stability observed in industrial systems. This suggestion is supported by the increased stability of water‐in‐bitumen emulsions doped with sodium naphthenates at concentrations higher than 50 ppm. The stability of the emulsion droplets can be further enhanced by capturing solid particles or precipitated asphaltenes at the LC‐coated interfaces. At equilibrium, optically anisotropic structures are detected in the bitumen/water/sodium hydroxide system, indicating the presence of a liquid crystal (LC) phase in industrial systems. The possible source of errors and proper use of polarization microscopy are discussed for LC phase containing emulsions.

Competitive adsorption of sodium naphthenates and naturally occurring species at water-in-crude oil emulsion droplet surfaces

The stability of water-in-crude oil emulsions is partly due to a complex, rigid layer formed at the water droplet surface that is likely made of large molecules such as asphaltenes. In highly diluted bitumen, where water droplet surfaces are relatively free of low molecular weight surfactant species, surface rigidity is prevalent. The properties of this layer change dramatically upon addition of a low molecular weight surfactant, sodium naphthenates (NaN), to the water phase. A rigid droplet surface becomes flexible as the concentration of NaN is increased. Interfacial tension measurements, made on individual micron-sized droplets, indicate that the water–oil interface is increasingly dominated by the added surfactant. Without the surfactant, over days, the interfacial tension of such a system decreases indicating long term, irreversible adsorption, similar to the behaviour observed for proteins, or a slow reorganization of the adsorbed macromolecules into lower energy configurations. It appears that the adsorbed NaN prevents adsorption of less surface-active, higher molecular weight material. Although water droplets remain stable despite surfactant addition, the nature of the stability changes. In the presence of added surfactant the droplets flocculate—a phenomenon not observed in its absence.

Aqueous foam films stabilized by sodium naphthenates

Stratification of a foam liquid film drawn from aqueous solutions of sodium naphthenate at relatively high concentration is likely due to a lamellar liquid crystal-like structure within the film. Film stratification, resulting in stepwise thinning, has been observed in foam films formed from systems containing either moderate to high concentrations of surfactant or in films formed from solutions containing solid particles. At moderate surfactant concentrations, film stratification is likely due to layers of ordered spherical micelles as postulated in Wasan and Nikolov's model of film stratification [A.D. Nikolov, P.A. Kralchevsky, I.B. Ivanov, D.T. Wasan, J. Colloid Interface Sci. 133 (1989) 13]. At high surfactant concentrations, stepwise thinning of the films and occurrence of domains of uniform color within the film suggest a lamellar liquid crystal-like structure within the film, potentially up to hundred or more oriented layers. The LLC-like structure inside the film can occur at concentrations below the lower limit of the LLC existence as a bulk phase.

Isolation and Characterization of Interfacial Materials in Bitumen Emulsions

Stable water-in-diluted-bitumen emulsions are detrimental to the commercial production of Athabasca bitumen. Isolation and characterization of interfacial materials (IM) from these emulsions are vital in order to reveal the emulsion stabilization mechanism, which is not fully understood to date. Recently, a heavy water method to isolate IM has been developed for model systems containing less than 10% bitumen. In this study, the heavy water method was improved to isolate IM from water-in-naphtha-diluted-bitumen emulsions at a bitumen concentration typically used in the commercial operation (59 wt %). Modification of the method includes an additional naphtha cleaning process for the wet IM cake. The isolated IMs were characterized by a variety of techniques such as elemental analysis, density measurements, thermal gravimetric analysis, infrared spectroscopy, Langmuir trough, and atomic force microscopy. The results show that the IMs isolated from emulsions containing 5% and 59% bitumen, referred to IM5 and IM59 respectively, are quite different. IM59 on surface of water droplets is likely in a monolayer structure, while IM5 in a multilayer structure. Asphaltene-like species could be dominant in IM5. IM59 features a higher H/C ratio and contains more volatiles, more chloroform insoluble components, and clays as compared to IM5. Carboxylates, probably in the form of sodium naphthenates, were detected in IM59 only, which may play a role in monolayer formation in the emulsion from which IM59 was obtained. Combination of monolayer structure and clays is believed to cause the high stability of emulsions at the bitumen concentration of 59%.

Stepwise thickening in aqueous foam films stabilized by sodium naphthenates

During drainage of a foam film formed from an aqueous sodium naphthenate solution, a transient, local, stepwise thickening process was observed. Film stratification is related to the stepwise thinning drainage process where individual layers of material are drained from a film. The process typically involves the appearance of a sequence of small, uniformly thick spots that eventually expand to the size of the film. The appearance and growth of each spot represents a discrete decrease in the thickness of the film. The size of each decrease or step typically corresponds to the size of one or more lamella layers of the stratified film. Stepwise thinning was observed in a foam film formed from an aqueous sodium naphthenate solution, as frequently reported for a variety of systems. However, during the drainage process, a transient stepwise thickening process was also observed. Bright spots began to appear and grow, indicate a discrete increase in the thickness of a portion of the film. This local, stepwise thickening process appeared to be an alternate and temporary drainage process directly related to the expansion of the stepwise thinning spots.

Emulsion stability based on phase behavior in sodium naphthenates containing systems: Gels with a high organic solvent content

Addition of heptane to a sodium naphthenates/toluene/water system at 25 °C reduces the lamellar liquid-crystal phase range and increases the microemulsion phase range. Both of these effects result in the extension of the composition range where emulsions have low stability. This effect is even stronger at 40 °C. Heptane addition also results in the formation of very stable emulsions within the overlapping phase-existence ranges of aqueous (L1) and organic (L2) phases. Stable non-birefringent gel observed in equilibrium with L1 and L2 phases contains only a small percentage of water and sodium naphthenates. The swelling behavior of an unstable gel, an emulsion previously compressed by centrifugation, appears to be due to a stepwise thickening of the thin liquid films between the droplets.

Investigating the Stability Mechanism of Water-in-Diluted Bitumen Emulsions through Isolation and Characterization of the Stabilizing Materials at the Interface

In oil sand industry, formation of a stable salty water-in-diluted bitumen emulsion poses a serious corrosion problem at the bitumen upgrading plant. Previous studies indicated the presence of a “critical concentration” of bitumen in the emulsion, above which the oil−water interface is flexible and the water-in-diluted bitumen emulsion is stable, but below which the interface becomes rigid and the emulsion is unstable. The cause of this critical concentration was investigated through isolation and characterization of the interfacial material from the emulsions both below and above the critical concentration. The analytical data showed that, in heptane/toluene(1:1)-diluted bitumen emulsions, the flexible interfacial film is composed of a mixture of asphaltene and carboxylic salts with a combined H/C ratio of 1.32 while the rigid interfacial film is composed of asphaltene alone with a H/C ratio of 1.13. The carboxylic salts are water insoluble and are likely sodium naphthenates containing >20 carbons. The p...

Naphthenic acids inhibit root water transport, gas exchange and leaf growth in aspen (Populus tremuloides) seedlings.

Effects of sodium naphthenates (NAs) on root hydraulic conductivity (Lp) and gas exchange processes were examined in aspen (Populus tremuloides Michx.) seedlings grown in solution culture. Exposure of roots to NAs for 3-5 weeks significantly decreased Lp and stomatal conductance. Root-absorbed NAs also decreased leaf chlorophyll concentration, net photosynthesis and leaf growth. Short-term (< or = 2 h) exposure of excised roots to NAs significantly decreased root water flow (Qv) with a concomitant decline in root respiration. We conclude that NAs metabolically inhibited Lp, likely by affecting water channel activity, and that this inhibition could be responsible for the observed reductions in gas exchange and leaf growth.

Sandwich Structures at Oil–Water Interfaces under Alkaline Conditions

Equilibrium liquid crystal (LC) layer on an interface between crude oils and water was observed at high pH. This layer is composed mainly of sodium naphthenates produced in situ at the water/oil interface. Transient LC layer was also evolved at the interface of aqueous phase of sodium hydroxide solutions and oleic phase of naphthenic acid (NA) solutions as result of a chemical reaction between NaOH and NA. This chemical reaction causes transport process resulting in a disturbance of the interface. Optical observation of this interface disturbance reviled that the interface covered with LC shows considerably lower flexibility as compared to LC free interface. The LC layer eventually dissolves in the water phase at low oil-to-water ratio, while at high oil-to-water ratio it can form an equilibrium phase, which spreads spontaneously at the oil–water interface.