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Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications. [ABSTRACT FROM AUTHOR]

Naphthenic acid (NA) widely exists in acidic crude oil. To reveal the mechanism of electrocoalescence of acidic crude oil emulsion, the influence of NA on the electrocoalescence of W/O emulsion is studied by high-frequency pulsed electrocoalescence technology and alkali washing method by changing electric field parameters and physical parameters. The results showed that the desalination (dehydration) rate of W/O emulsion increases with the increase of electric field strength, frequency, duty ratio, initial water contents and divalent salts. With the increase of monovalent salts, naphthenic acid and alkali injections, the desalination effect decreases. The sodium naphthenate intensified the emulsification effect. The presence of NA reduces the desalination rate. By increasing the concentration of CaCl2, the desalination effect of acidic crude oil emulsion is improved. The desalination rate is up to 99.63%, the water content is less than 0.5%, the salt concentration is less than 3 mg L−1, and the acid value is less than 0.03 mgKOH g−1. Our studies provide a theoretical basis for high-frequency pulsed electrocoalescence technology to improve the electrocoalescence and the multiple removal mechanism of inorganic salts and organic acids of acidic crude oil. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are a complex mixture of organic compounds released during bitumen extraction from mined oil sands that are important contaminants of oil sands process-affected water (OSPW). NAs can be toxic to aquatic organisms and, therefore, are a main target compound for OSPW. The ability of microorganisms to degrade NAs can be exploited for bioremediation of OSPW using constructed wetland treatment systems (CWTS), which represent a possible low energy and low-cost option for scalable in situ NA removal. Recent advances in genomics and analytical chemistry have provided insights into a better understanding of the metabolic pathways and genes involved in NA degradation. Here, we discuss the ecology of microbial NA degradation with a focus on CWTS and summarize the current knowledge related to the metabolic pathways and genes used by microorganisms to degrade NAs. Evidence to date suggests that NAs are mostly degraded aerobically through ring cleavage via the beta-oxidation pathway, which can be combined with other steps such as aromatization, alpha-oxidation, omega-oxidation, or activation as coenzyme A (CoA) thioesters. Anaerobic NA degradation has also been reported via the production of benzoyl-CoA as an intermediate and/or through the involvement of methanogens or nitrate, sulfate, and iron reducers. Furthermore, we discuss how genomic, statistical, and modeling tools can assist in the development of improved bioremediation practices. [ABSTRACT FROM AUTHOR]

The present study demonstrated the efficiency of ionic liquid in the removal of naphthenic acids from crude oil. The crude oil sample was obtained from Belema oil field in Southern Nigeria while tetramethyl ammonium hydroxide pentahydrate (TMAH) ionic liquid was commercially obtained. Liquid-liquid extraction was carried out and the reaction conditions were modelled and optimized using Box-Behnken design of the response surface methodology. Ionic liquid concentration (w/v%), reaction temperature (°C), and reaction time (mins) were selected as the factors while extraction efficiency (%) was selected as the response. The results of the study showed that the highest extraction efficiency of 96.67 % was achieved under reaction conditions of 3 w/v% ionic liquid concentration, 50 °C reaction temperature, and 45 mins reaction time. Owing to R2, adjusted R2, and predicted R2 values generally > 0.90, the model accurately described the deacidification reaction. Optimization results indicated that removal efficiency can reach over 96 % at 2.82 w/v% ionic liquid concentration, 48 °C reaction temperature, and 45 mins reaction time. The characterization of the original and deacidified oils using GC–MS showed reduced concentration of acidic species in the latter. Also, FT-IR of the ionic liquid showed minimal or no variations in functional groups before and after extraction, highlighting a possibility for regeneration of the ionic liquid. The findings of the study showed the use of ionic liquids as green alternatives in the removal of acidic species from crude oil.

Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the oil viscosity. However, the relationship between the molecular composition of naphthenic acids and oil viscosity is not well understood. This study examined a "clean" heavy oil with low contents of heteroatoms but had a high content of naphthenic acids. Naphthenic acids were fractionated by distillation and caustic extraction. The molecular composition was characterized by highresolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15e35 carbon atoms are dominant components of the acid fractions; the caustic extraction is capable of isolating naphthenic acids with less than 35 carbons, which is equivalent to the upper limit of the distillable components, but not those in the residue fraction; the total acid number of the heavy distillates is higher than that of the residue fraction; the viscosity of the distillation fraction increases exponentially with an increased boiling point of the distillates. Blending experiments indicates that there is a strong correlation between the oil viscosity and acids content, although the acid content is only a few percent of the total oil. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper represents a detailed techno-economic analysis of a typical commercial-scale catalytic decarboxylation process of naphthenic acids over HZSM-5 zeolite. Simulation of the process has been performed in ASPEN Plus®. The performance of the modeled unit was compared to experimental results data from a similar plant. Two models were developed for the proposed industrial plant based on continuous flow reactors; the first is based on a fluidized bed reactor, and it was modeled as a continuous stirred tank reactor (CSTR) unit, and the second is a semi-regenerative process that consists of three fixed-bed reactors with intermediate preheaters and are modeled as three plug flow reactors (PFR). The outcome of the economic analysis of the two proposed commercial scale reactors of a decarboxylation process of a capacity of 11,000 bbl/day showed that the CAPEX, including the total equipment cost for the fluidized bed reactor plant and semi-regenerative process plant, was $44,319,362 and $4,447,919, respectively. The annual operating cost for the fluidized bed plant and semi-regenerative process plant is 45,269,180 $/year and 1,771,839 $/year, respectively. Our results demonstrated that catalytic decarboxylation over HZSM-5 zeolite is economically feasible using a semi-regenerative process, and is a promising method for removing naphthenic acid. The insight obtained from this work can be used as a basis for more comprehensive future financial and risk modeling of the process. The cost estimated in this work was compared to the Khartoum refinery cost for the naphthenic acid corrosion mitigation system, with a saving of $29,459,528. [ABSTRACT FROM AUTHOR]

Calcium in crude oil can cause equipment fouling and catalyst deactivation, hence the speciation of calcium in crude oil is of interest to the petroleum industry. This review summarizes various forms of calcium found in crude oils, includes inorganic calcium-containing compounds and organic calcium-containing compounds. The progress in characterization method and molecular composition of organic insoluble calcium-containing compounds are highlighted. The organic calcium compounds are mainly calcium naphthenate, therefore the challenge for the characterization of calcium compounds is the molecular characterization of the hydrolyzed naphthenic acids. With the advances in high-resolution mass spectrometry, the complex mixture of naphthenic acids can be characterized at the molecular level. Large molecular tetra carboxylic acids, which are derived from bacterial/eukaryotic lipids and/or archaeal membranes, are found the major component to form hard deposit with calcium ions. Naphthenic acids are considered as a key controlling factor for the calcium content in petroleum, however, the mechanism of interaction between calcium and naphthenic acid molecules is still not well understood. [ABSTRACT FROM AUTHOR]

Formation of activated carbon from petroleum coke by KOH, results in high specific surface area materials that are predominantly microporous. This initial microporosity means that the adsorption kinetics of target species are not as rapid as they could be, thus limiting environmental remediation applications for the material. To address this problem a series of additional heat cycles with no additional chemical inputs were applied after activation but prior to the removal of activating agents. This process resulted in the oxidation of residual potassium metal from the initial activation which allows it to function again as an activating agent for the subsequent cycles. The heat cycling resulted in an increase in mesoporosity by 10–25% with each successive cycle independent of the KOH to feedstock ratio. This was shown to be demonstrably different than equivalently extended heating times, thus identifying the importance of thermal cycling. Adsorption kinetics of three model naphthenic acids showed faster kinetics for the pore widened activated carbon. The t1/2 times dropped from 20 to 6.6 min for diphenyl acetic acid, 34.3 to 4.5 min for cyclohexane acetic acid, and 51.4 to 12.0 min for heptanoic acid.

Interfacial tension (IFT) is important in developing oilfield exploration and production strategies, enhanced oil recovery, and oil-water separation. Tests using reservoir simulators such as Eclipse show that the selected IFT has significant impact on prediction of water coning and production. In petroleum engineering, IFT is often assessed through correlations based on bulk properties excluding the impact of surface-active components. Crude oil contains many different types of surface-active components among which naphthenic acids and asphaltene-like molecules play an important role in IFT between oil and water. It is desirable to be able to link the IFT to the concentration of the natural surfactants to predict variations across a petroleum reservoir. To develop this relation, the equilibrium IFT was investigated in various systems of varying acid content. As expected, naphthenic acids reduce IFT of oil and water significantly. The IFT reduction is however dependent on the structure and composition of naphthenic acids as well as the nature of the solvent. To include the natural surfactancy in the model a Gibbs-Langmuir approach is used to describe the impact of naphthenic acids content in crude oil on IFT. This is compared to two models currently used to estimate IFT in the petroleum industry. The current models are not equipped to capture the role of natural surfactants and hence results may lead to erroneous predictions on crude oil production. We therefore propose an approach where bulk properties that estimate the bulk IFT is used in combination of a term based on the Gibbs-Langmuir model to capture the perturbation by the naphthenic acids to yield more accurate estimates of IFT. This require fitting to at least two experimental points to yield accurate results. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are thought to be a primary cause of toxicity of oil sands process-affected water (OSPW). The purpose of this study was to determine if commercially available adamantane carboxylic acids act by mitrochondrial mechanisms similar to NAs found in OSPW. Mitochondria isolated from rainbow trout (Oncorhynchus mykiss) liver were exposed to commercially available adamantane acids, 3-hydroxyadamantane-1-carboxylic acid (CAS 42711-75-1) and 3,5-dimethyladamantane-1-carboxylic acid (CAS 14670-94-1), or to NAs extracted and purified from OSPW. The effects of these compounds on state 3 and 4 respiration, mitochondrial membrane potential, and mitochondrial reactive oxygen species (ROS; H2O2 production) were quantified. The compound 3-hydroxyadamantane-1-carboxylic acid only inhibited state 3 respiration at the highest concentration (2560 mg/L) and showed a concentration-dependent reduction in H2O2 production. Consistent with extracted OSPW NAs, 3,5-dimethyladamantane-1-carboxylic acid inhibited state 3 respiration and increased H2O2 production, but with a two-fold greater EC50 than the NA mixture extracted from OSPW. All three compounds uncoupled mitochondrial membrane potential and increased state 4 respiration. Based on these results, the adamantane 3,5-dimethyladamantane-1-carboxylic NAs may act via similar mitrochondrial mechanisms as NAs extracted from OSPW and could be used to further explore toxic mechanisms.

The naphthenic acid fraction compound (NAFC), 3,5-dimethyladamantane-1-acetic acid, was tested for its ability to uncouple mitochondrial oxidative phosphorylation. Mitochondria isolated from rainbow trout (Oncorhynchus mykiss) liver were exposed to 3,5-dimethyladamantane-1-acetic acid in state 3 and 4 respiration, and mitochondrial membrane potential were quantified. Electron transport chain (ETC) protein complexes were isolated using pharmacological agents and inhibitors, and their activities measured. The NAFC compound completely inhibited states 3 and 4 respiration with an IC50 of 0.77 and 1.01 mM, respectively. The NAFC compound partially uncoupled mitochondrial membrane potential in state 3 and 4 respiration with an IC50 of 2.19 and 1.73 mM, respectively. The NAFC impaired the activities of ETC protein complexes with a 9.5-fold range in sensitivity. The relative inhibitory effect of the ETC protein complexes to NAFC was CIV≥CI>CIII>CII. The impairment of mitochondrial oxidative phosphorylation by adamantane 3,5-dimethyladamantane-1-acetic acid is mediated via its inhibition of ETC protein complexes. • Potency of a naphthenic acid as a respiratory toxicant was examined in mitochondria. • The adamantane was capable of completely inhibiting respiration. • The adamantane compound could only partially reduce membrane potential. • Complexes I and IV were more sensitive as compared to II and III by 10-fold. [ABSTRACT FROM AUTHOR]

• A solvent extraction method for separating and purifying beryllium hydroxide from multi-component solution has been developed. • Naphthenic acid as a high loading capacity beryllium extractant has been screened. • Selective separation of beryllium and various trace impurities, especially beryllium and aluminium, has been realized. • Extraction mechanism and thermodynamics selective separation of Be and Al has been discussed. Beryllium is an essential metal for strategic purposes but remains an under-explored element. The separation of beryllium and aluminium and the purification of beryllium hydroxide from a multi-component solution has always been a challenging task in the beryllium industry and offers great research potential in academic fields. In this research, a solvent extraction method was used to purify and recover beryllium from trace impurities. A systematic investigation of the extraction process revealed that under optimal conditions, 98.66% of the beryllium was extracted in a three-stage countercurrent extraction using naphthenic acid (NA) as the extractant. The aluminium, iron and other trace impurities in the organic phase can be scrubbed with 1 mol/L HCl, then 99.27% of the beryllium was stripped with 5 mol/L NaOH by two-stage stripping. Be(OH) 2 with a purity of 99.67% was recovered from the stripped beryllium solution by hydrolysis precipitation method. Furthermore, FT-IR analysis and slope analysis demonstrate the mechanism of beryllium extraction with naphthenic acid accompanied by cation exchange. The influence of temperature on the beryllium extraction was investigated and the thermodynamic parameters and the equilibrium constant of the extraction reaction were calculated. Accordingly, a process flowsheet for the separation of beryllium from multiple impurities using naphthenic acid was developed. This process is believed to offer the advantages of high efficiency, recyclability, and a favorable beryllium-aluminium separation effect; presenting a promising new approach to beryllium recovery. [ABSTRACT FROM AUTHOR]

Abstract Process facilities for the separation of hydrocarbons from produced water in the oilfield are critical to flow assurance, product quality and environmental compliance. The formation of metal naphthenates, which are emulsion stabilizers and equipment foulers, is deleterious to performance and integrity of these processes and facilities. Manual removal of deposits of these organic salts formed at the oil–water interface during separation processes is difficult and expensive; hence, the best operational option is inhibition. The conventional method for the inhibition of metal naphthenates, which relies on suppressing the deprotonation of naphthenic acids by common ion effect, is no longer tenable because it exacerbates internal corrosion problems in topside facilities. Current industry focus is on the development of effective surface active agents for inhibition of naphthenates. There are a plethora of chemical compounds with naphthenate inhibition potential such as sulphonates, phosphate esters, aminated phosphonates and sulphosuccinates, but compatibility issues make the choice of inhibitor a complicated process. In this paper, the drivers and mechanism of oilfield metal naphthenate formation are reviewed. Surfactants for oilfield metal naphthenate inhibition and the mechanisms of inhibition are highlighted with a view to process optimization.

Abstract The presence of acidic compounds as naphthenic acids in crude oil causes several problems for the petroleum industry, including corrosion in both upstream and downstream production processes. Based on this scenario, the main objective of this work was to investigate the removal of the acidic compound from two Brazilian heavy oils by adsorption processes using six potential adsorbents: powdered shale, activated carbon, bentonite, silica gel, powdered sandstone and powdered wood. These raw materials were previously characterized by conventional and surface analysis techniques, which show that they offer a good surface area and thermal stability. To evaluate the removal efficiency at the molecular level, the crude oil samples and the filtered oils were analyzed by negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry [ESI (-) FTICR MS]. The O2 class, which is related to the relatively high acidity of the samples, was the most abundant in both crude oil samples, moreover, this class was more retained by adsorbents. Silica gel, activated carbon and bentonite were the best adsorbents of acidic compounds from the tested oils, in agreement with their markedly higher surface area and porous volume. Additionally, a chromatographic analysis was performed and showed no changes in the oil profile.

The removal of water-soluble organics compounds in oilfield produced water (OPW) is currently one of the biggest challenges to meet the environmental legislation, as conventional remediation focuses mainly on removing solids and the dispersed oil fraction. Naphthenic acids (NAs) are present in significant amounts in water-soluble organics compounds; therefore, this work milestone is to properly understand the adsorption process by using an acutely recalcitrant O 2 -NA as WSO model. For this, a comprehensive screening of commercial adsorbents and waste was tested for NAs remediation, assessing also the influence of adsorbent properties and functionalities. Afterwards, there were selected the resins MN 202 and L 493 as adsorbents to further evaluate the regeneration and other variables such as temperature, pH and salt content, focusing on on-site offshore conditions. The initial screening and the equilibrium data suggest that characteristics such as surface area, pore diameter, and ionic form have a great influence on the adsorption process. Furthermore, the adsorption mechanisms involve anion exchange and hydrophobic interactions, showing a transition between multilayer to monolayer adsorption with the increase of the adsorbent dosage and the kinetics, while increasing NA encourages pore diffusion, resulting in irreversible adsorption. The use of eluents, while avoiding irreversible adsorption, allows recovering the adsorbent, improving the process feasibility at the targeted conditions. [ABSTRACT FROM AUTHOR]

This paper reviews the history and use of copper naphthenate as a heavy-duty wood preservative, with a focus on use patterns within the USA and opportunities for expansion in Canada and Europe. Copper naphthenate has demonstrated efficacy to preserve and protect cellulosic and wooden items essential to critical infrastructure and is an ideal choice for use in the replacement of pentachlorophenol and creosote where less toxic and environmentally friendlier alternatives are required. [ABSTRACT FROM AUTHOR]

• Mg-Al hydrotalcite were used as catalyst to lower the TAN of crude oils. • The esterification of 3-cyclopentylpropionic with methanol was performed at 80ªC. • The best performance was obtained with Mg-Al hydrotalcite without calcination. • Brönsted basic sites (OH−) were confirmed as active centres in the esterification. • The esterification reaction was first order to acid and activation energy 25.3 kJ/mol. The presence of relatively high levels of naphthenic acids in crude oil may cause serious corrosion problem at temperature between 200 °C and 400 °C. One of the viable processes for decreasing acidity is the esterification of the present acids using an alcohol such as methanol. Therefore, the aim of this work is to develop a solid catalyst for the esterification reaction of 3-cyclopentylpropionic acid representative of the naphthenic acids. The esterification reaction is carried out at 80 °C, 3.5 kg/cm2 of pressure in a mechanically stirred batch reactor, using Mg-Al hydrotalcite (Mg/Al = 4) with different activation treatments as catalyst. These solids are characterized by N 2 sorptometry and X ray diffraction. The higher concentration of Bronsted basic sites present in uncalcined hydrotalcite would explain the satisfactory performance obtained. TAN decreased 90% by operating at a temperature as low as 80 °C after 60 min of reaction. The catalytic activity is evaluated at different reaction conditions such as, mass of catalyst, stirring speed and reaction temperature. A kinetic study for heterogeneous esterification of 3-cyclopentylpropionic acid with methanol was performed. [ABSTRACT FROM AUTHOR]

The interfacial activity of asphaltenes, naphthenic acids, and naphthenates has been amply studied in the literature, as they are involved in the formation and stabilization of bitumen and heavy crude oil emulsions. While most of the literature evaluates one component at a time, in this work these bitumen components were separated one at a time from Athabasca bitumen, and the surface activity of the resulting fraction was evaluated as a function of pH, solvent aromaticity (heptane/toluene mixtures, known as heptol, at volume ratios 50/50 and 80/20), and temperature for selected systems. The interfacial activity was evaluated in two ways: via dynamic interfacial tension during adsorption on a bitumen drop of constant volume, and via dynamic interfacial tension during drop volume cycling. The adsorption data were interpreted using a model that combined multicomponent adsorption kinetics inspired by Langmuir–Freundlich kinetics with the Fainerman surface equation of state. The volume cycling experiments were interpreted using the compression relaxation model, which segregates adsorption/relaxation effects from elastic phenomena at interfaces. Overall, the adsorption data confirmed that naphthenic acids are the fastest adsorbing species that tend to dominate the interface, but that asphaltenes adsorb, almost irreversibly, at longer time scales and likely forming a sublayer previously proposed in the literature. The dilatational elasticity of the interface seems to be highly influenced by that asphaltene sublayer, which softens at high pH at room temperature, or at 80 °C independently of the pH of the system. [ABSTRACT FROM AUTHOR]

The naphthenic acids (NAs) present in the crude oil can lead to the corrosion problems in oil refinery equipment apart from reduces the performances of the oil. In this study, the method to remove NA were done by means of extraction using sodium thiocyanate in ethanol with the aid of Ni/Ca/Al2O3 and Ni/Ce/Al2O3 catalysts at 27 °C reaction temperature. The catalyst was prepared by incipient wetness impregnation method (IWI) and calcined at three different temperature, 800, 900 and 1000 °C respectively. The efficiency of the extraction was affected by the catalyst calcination temperature. Both catalysts calcined at 800 and 900 °C gave total acid number (TAN) value more than 1 mg KOH/g while by using Ni/Ca(10:90)/Al2O3 and Ni/Ce(10:90)/Al2O3 calcined at 1000 °C the TAN value were reduced to 0.28 and 0.65 mg KOH/g respectively. Brunauer-Emmett Teller (BET) result shows both catalysts have large surface area that provide more reaction cites when calcined at 1000 °C. X-ray Diffraction Spectroscopy (XRD) analysis of Ni/Ca/Al2O3 catalyst revealed that the active site was dominated by the Al2O3 species while CeO2 was the active site for Ni/Ce/Al2O3 catalyst. In conclusion, both catalysts reduced the TAN value of acidic crude oil efficiently. [ABSTRACT FROM AUTHOR]

Nowadays, the increase of the unconventional oil deposit exploitation and the amount of oil sands process-affected waters (OSPW) in tailing ponds emerges the importance of developing bio-monitoring strategies for the restoration of these habitats. The major constituents of such deposits are naphthenic acids (NAs), emerging contaminant mixtures with toxic and recalcitrant properties. With the aim of developing bio-monitoring strategies based on culture-independent approach, we identified genes coding for enzymes involved in NA degradation from Rhodococcus opacus R7 genome, after the evaluation of its ability to mineralize model NAs. R. opacus R7 whole-genome analysis unveiled the presence of pobA and chcpca gene clusters putatively involved in NAs degradation. Gene expression analysis demonstrated the specific induction of R7 aliA1 gene, encoding for a long-chain-fatty-acid-CoA ligase, in the presence of cyclohexanecarboxylic acid (CHCA) and hexanoic acid (HA), selected as representative compounds for alicyclic and linear NAs, respectively. Therefore, aliA1 gene was selected as a molecular marker to monitor the biodegradative potential of slurry-phase sand microcosms in different conditions: spiked with CHCA, in the presence of R. opacus R7, the autochthonous microbial community, and combining these factors. Results revealed that the aliA1-targeting culture-independent approach could be a useful method for bio-monitoring of NA degradation in a model laboratory system. [ABSTRACT FROM AUTHOR]

Process facilities for the separation of hydrocarbons from produced water in the oilfield are critical to flow assurance, product quality and environmental compliance. The formation of metal naphthenates, which are emulsion stabilizers and equipment foulers, is deleterious to performance and integrity of these processes and facilities. Manual removal of deposits of these organic salts formed at the oil–water interface during separation processes is difficult and expensive; hence, the best operational option is inhibition. The conventional method for the inhibition of metal naphthenates, which relies on suppressing the deprotonation of naphthenic acids by common ion effect, is no longer tenable because it exacerbates internal corrosion problems in topside facilities. Current industry focus is on the development of effective surface active agents for inhibition of naphthenates. There are a plethora of chemical compounds with naphthenate inhibition potential such as sulphonates, phosphate esters, aminated phosphonates and sulphosuccinates, but compatibility issues make the choice of inhibitor a complicated process. In this paper, the drivers and mechanism of oilfield metal naphthenate formation are reviewed. Surfactants for oilfield metal naphthenate inhibition and the mechanisms of inhibition are highlighted with a view to process optimization. [ABSTRACT FROM AUTHOR]

CO 2 -responsive microemulsion (ME) is considered a promising candidate for deep-cleaning and oil recovery from oil-contaminated soils. Understanding the responsive nature of different microstructures (i.e. , oil-in-water (O/W), bicontinuous (B.C.) and water-in-oil (W/O)) is essential for unlocking the potential and mechanisms of CO 2 -responsive emulsions in complex multiphase systems and providing comprehensive guidance for remediation of oil-contaminated soils. Herein, the responsiveness of microstructures of ME to CO 2 trigger was investigated using experimental designs and coarse-grained molecular dynamic simulations. MEs were formed for the first time by a weakly associated pseudo-Gemini surfactant of indigenous organic acids (naphthenic acids, NAs are a class of natural surface-active molecules in crude oil) and tetraethylenepentamine (TEPA) through fine tuning of co-solvent of dodecyl benzene sulfonic acid (DBSA) and butanol. The O/W ME exhibited an optimal CO 2 -responsive character due to easier proton migration in the continuous aqueous phase and more pronounced dependence of configuration on deprotonated NA ions. Conversely, the ME with W/O microstructure exhibited a weak to none responsive characteristic, most likely attributed to its high viscosity and strong oil-NA interactions. The O/W ME also showed superior cleaning efficiency and oil recovery from oil-contaminated soils. The results from this study provide insights for the design of CO 2 -responsive MEs with desired performance and guidance for choosing the favorable operating conditions in various industrial applications, such as oily solid waste treatment, enhanced oil recovery (EOR), and pipeline transportation. The insights from this work allow more efficient and tailored design of switchable MEs for manufacturing advanced responsive materials in various industrial sectors and formulation of household products. [Display omitted] • PGS prepared using natural NAs in crude oil and TEPA formulated CO 2 -responsive MEs. • A relationship between microstructures of MEs and responsiveness was established. • Migration of protons and type of MEs determine CO 2 responses of MEs. • O/W CO 2 -responsive MEs exhibited the best cleaning of oil-contaminated solids. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the capability of subcritical methanol to reduce the acidity of naphthenic acids and to determine reaction kinetics for large-scale reactor design.The experiments were carried out in a 25 mL autoclave reactor (China) at temperatures of 70-120oC, Methanol Partial Pressures (MPPs) of 0.1-1.5 MPa, and reaction times of 0-60 min. The total acid number content of the samples was analyzed using ASTM D 974 techniques. Experimental results reveal that total acid number reduction of naphthenic acids increased with increasing reaction temperature, MPP, and reaction time. Approximately 74.20% total acid number was reduced at a temperature of 120oC, a MPP of 1 MPa, and a reaction time of 60 min. Experimental data revealed that total acid number removal reaction kinetics followed second-order kinetics with an activation energy of 11.27 kcal/mol. Therefore, subcritical methanol is able to reduce the total acid number of naphthenic acids without the addition of any catalyst.

Extraction of Cu+2 from dilute aqueous solutions as a case study by liquid cation exchanger in a modified rotating disc extractor was studied. The liquid cation exchanger consisted of naphthenic acid dissolved in an inert carrier kerosene. Variables studied were: initial concentration of Cu+2, disc rotational speed, concentration of naphthenic acid, flow rates of continuous and dispersed phase, degree of roughness, and number of rotating discs. The rate of extraction increased with increasing rotational speed, concentration of naphthenic acid, flow rate of dispersed phase, degree of roughness and number of discs to a certain number, while increasing Cu+2 concentration and flow rate of continuous phase decreased the rate of extraction. All variables were correlated by the dimensionless mass transfer equation. Possible practical applications of the present data in treating aqueous waste from different sources such as petrochemical industries, electroplating, and hydrometallurgical processes was highlighted.

Extraction of Canada's oil sands has created 1 billion m3 of tailings, which are stored in on-site tailings ponds. Due to limited storage capacity, the planned release of tailings into the surrounding environment may be required. This represents an environmental management challenge, as the tailings contain contaminants that are known toxins to aquatic communities. Of particular concern are naphthenic acids and their metallic counterparts, as they are the principal toxic components of tailings, are relatively soluble, and are persistent in aquatic environments. This study examines the acute toxicity of environmentally relevant 10:1 mixtures of two process water components: naphthenic acid and sodium naphthenate. We assess the effects of these simplified oil sands process water (OSPW) mixtures under planned and unplanned tailings release scenarios, using traditional and cutting-edge bioindicators for aquatic invertebrate taxa. We found that safe concentrations for mayflies and other aquatic macroinvertebrates were less than 1 mg/l, as no mayfly taxa survived repeated exposure to this dose in either the 48-h or 72-h acute toxicity test. In the 72-h test, no mayflies survived treatment levels greater than 0.5 mg sodium naphthenate/l. In the mesocosm study, even a 90% dilution of the OSPW mixture was not sufficient to protect sensitive macroinvertebrate communities. The results of this study highlight the potential environmental damage that will occur if OSPW is not carefully managed. This information will aid with the development of a management plan for oil sands tailings ponds, which will provide insight into the potential for process water release into the surrounding environment while conserving unique ecosystems downstream of development in the oil sands region. [ABSTRACT FROM AUTHOR]

Highlights • Naphthenic acid (NA) is a major cause of corrosion in heavy crude oil refinery. • The current approaches for de-acidification of crude oil have serious shortcomings. • DBU based ILs have been found to be an efficient media for NA removal. • Molecular dynamic simulation of dodecane, NA and IL mixture was performed. • DBU cation does not form any cage around the naphthenic acid. • Major factor in extraction of NA is the solubility of the polar IL in the dodecane. Abstract Naphthenic acid is a toxic component that is present in the crude oil. It causes severe operational problems for oil refineries. However, naphthenic acid is a useful raw material for many industrial processes. Thus, it is advantageous to extract and recover the naphthenic acid from crude oil. Ionic liquid has been considered as an environmental friendly material that can be used to extract naphthenic acid from crude oil. However, the characteristics of the ionic liquids to achieve the best extraction efficiency is still not completely known. In this research, the performance of the ionic liquids consists of diazabicyclo undecene (DBU) based cations and dicyanamide (DCN) anion in the extraction of naphthenic acid from acidic model oil was studied. Computer simulation of a mixture of naphthenic acid, ionic liquid, and n-dodecane was also performed. The study showed that the DBU-DCN based ionic liquids can effectively extract naphthenic acid from highly acidic model oil. The increase in the alkyl chain length on the cation increases the percent naphthenic acid extraction. Molecular simulation studies showed that the dicynamide anion interacting directly with the naphthenic acid. The alkyl chain on the DBU cation does not form any cage around the naphthenic acid as previously proposed. The study suggests that the biggest factor affecting naphthenic acid extraction efficiency is the extent of solubility of the polar ionic liquid in the non-polar oil. [ABSTRACT FROM AUTHOR]

Cyclopentane carboxylic acid (CPCA) is a model compound of Naphthenic acids (NAs). This objective of this paper is to discover total acid number (TAN) reduction kinetics and pathways of the reaction between CAPA and subcritical methanol (SubC-MeOH). The experiments were carried out in an autoclave reactor at temperatures of 180-220°C, a methanol partial pressure (MPP) of 3 MPa, reaction times of 0-30 min and CPCA initial gas phase concentrations of 0.016-0.04 g/mL. TAN content of the samples were analyzed using ASTM D 974 techniques. The reaction products were identified and quantified with the help of GC/MS and GC-FID respectively. Experimental results reveal that TAN removal kinetics followed first order kinetics with an activation energy of 13.97 kcal/mol and a pre-exponential factor of 174.21 s-1. Subcritical methanol is able to reduce TAN of CPCA decomposing CPCA into new compounds such as cyclopentane, formaldehyde, methyl acetate and 3-pentanol.