Naphthenic Acids Research Articles

Continuous extraction of naphthenic acid from low-grade oil using 1,6-hexanediol in an ammonia solution

The efficient use of low-quality crude oil is one short-term solution to overcoming the imminent energy crisis due to the depletion of fossil resources. Several methods have been developed to upgrade low-quality oil, the most important part of which is the removal of acidic components. High-acid crudes can be converted to lower-acid crudes using various methods based on physical and chemical principles. In this contribution, we suggest an efficient and economical method based on liquid–liquid extraction. The candidate solvent was screened from a thermodynamic analysis in a previous study, and the additives and process conditions were adjusted according to experimental results. As the final solvent choice, 1,6-hexanediol in an aqueous ammonia solution showed the best performance with the minimal amount of solvent (weight fraction of 0.6). Experiments showed that the proposed solvent can be used to treat real crude oil used in the industry. A continuous operation scheme was suggested with solvent regeneration and recycling combined with separation of the acidic residue. The results showed that the proposed extraction process can reduce 85% of the acidic component in high-acid crudes and that repeated use of the solvent is possible.

Application of mesoporous zeolite Socony Mobil-5 (ZSM-5) as an adsorbent material for the removal of naphthenic acid present in oil-produced water

The porous structure of ZSM-5 zeolite strongly affects the adsorption, especially when resistant compounds are present in the water, such as naphthenic acid in oil-produced water. In this sense, ME-ZSM-5 zeolite was synthesized by adding sodium alginate for later use as an adsorbent to remove naphthenic acid from synthetic water and real oil-produced water. Firstly, the results showed that the structural characteristics of the modified zeolite were improved by using sodium alginate (surface area of 235.58 m2 g−1 and total pore volume of 0.125 cm3 g−1). Besides, the adsorption of naphthenic acid from synthetic water was optimal using an adsorbent dosage of 3 g L−1 and pH 4, being the adsorption capacity of 195 mg g−1. Still, in synthetic solutions, the enthalpy of adsorption confirmed an exothermic process, and kinetic studies showed that the system reached equilibrium within the first 50 min. Finally, ME-ZSM-5 was applied to remove naphthenic acid from a real sample of oil-produced water and removed 92%. Therefore, ME-ZSM-5 zeolite was successfully synthesized and could be used as adsorbent material to uptake naphthenic acid from oil-produced water.

ROS-mediated time-varying cytotoxic effects on Phaeodactylum tricornutum under the stress of commercial naphthenic acids

The aquatic toxicity and ecological risks of naphthenic acids (NAs) in marine environments have attracted an increasing amount of attention. However, there remains a lack of methodologies for the long-term risk assessment of NAs on marine ecosystems after high acid crude oil spill accidents. In this study, using the model microalgae Phaeodactylum tricornutum as the target object, the time-effect manner under NAs stress is investigated for a continuous 24–144 h. We found that: 1) NAs caused photosynthetic damage and persistent oxidative stress that slowed the growth rate and limited the maximum growth of P. tricornutum population within 24 h to 144 h of exposure, especially under the high concentration treatment; 2) Within 144 h, NAs can cause oxidative stress to P. tricornutum. The damage to cell membrane and radical oxidative species (ROS) accumulation of P. tricornutum were observed as obvious time-effect; 3) Under NAs stress, the two types of cell death (accidental cell death and regulated cell death) of P. tricornutum cell mediated by ROS played different roles in the population growth inhibition of P. tricornutum. Moreover, regulated cell death of the P. tricornutum cell was accompanied by PS externalization, DNA fragment and the G2/M phase stagnation acted as an adaptive regulatory mechanism under NAs stress. This explained the dose-time-effects of NAs on the population growth of P. tricornutum. Overall, the results suggested that NAs have a lasting effect on marine phytoplankton populations, and long-term risk assessments are required after high acid crude oil spill accidents. This is the first attempt to identify the different types of death at the cellular level to explain the time-effect toxicity at the population level of marine microalgae when exposed to NAs. This research will provide a new approach to facilitate further risk assessments for NAs and related contaminants in marine ecosystems.

Aqueous naphthenic acids and polycyclic aromatic hydrocarbons in a meso-scale spill tank affected by diluted bitumen analyzed directly by membrane introduction mass spectrometry

With the increasing use of unconventional, heavy crude oils there is growing interest in potential impacts of a diluted bitumen (DB) spill in marine and freshwater environments. DB has the potential to release several toxic, trace organic contaminants to the water column. Here, the aqueous concentrations and compositions of two classes of organic contaminants, naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs), are followed over 8 weeks after a simulated spill of DB (10 L) into a freshwater mesocosm (1200 L) with river sediment (2.4 kg). These complex samples contain biogenic dissolved organic matter, inorganic ions, petroleum contaminants, suspended sediments, and oil droplets. We report the first use of condensed phase membrane introduction mass spectrometry (CP-MIMS) as a direct sampling platform in a complex multi-phase mesocosm spill tank study to measure trace aqueous phase contaminants with little to no sample preparation (dilution and/or pH adjustment). CP-MIMS provides complementary strengths to conventional analytical approaches (e.g., gas- or liquid chromatography mass spectrometry) by allowing the entire sample series to be screened quickly. Trace NAs are measured as carboxylates ([M-H]-) using electrospray ionization and PAHs are detected as radical cations (M+•) using liquid electron ionization coupled to a triple quadrupole mass spectrometer. The DB-affected mesocosm exhibits NA concentrations from 0.3 to 1.2 mg/L, which rise quickly over the first 2 – 5 days , then decrease slowly over the remainder of the study period. The NA profile (measured as the full scan in negative-electrospray ionization at nominal mass resolution) shifts to lower m/z with weathering, a process followed by principal component analysis of the normalized mass spectra. We couple CP-MIMS with high-resolution mass spectrometry to follow changes in molecular speciation over time, which reveals a concomitant shift from classical ‘O2’ naphthenic acids to more oxidized analogues. Concentrations of PAHs and alkylated analogues (C1 – C4) in the DB-affected water range from 0 to 5 μg/L. Changes in PAH concentrations depend on ring number and degree of alkylation, with small and/or lightly alkylated (C0 – C2) PAH concentrations rising to a maximum in the first 4 – 8 days (100 – 200 h) before slowly decaying over the remainder of the study period. Larger and heavily alkylated (C3 – C4) PAH concentrations generally rise slower, with some species remaining below the detection limit throughout the study period (e.g., C20H12 class including benzo[a]pyrene). In contrast, a control mesocosm (without oil) exhibited NA concentrations below 0.05 mg/L and PAHs were below detection limit. Capitalizing on the rapid analytical workflow of CP-MIMS, we also investigate the impacts of sample filtration at the time of sampling (on NA and PAH data) and sample storage time (on NA data only).

Using machine learning-based variable selection to identify hydrate related components from FT-ICR MS spectra.

The blockages of pipelines caused by agglomeration of gas hydrates is a major flow assurance issue in the oil and gas industry. Some crude oils form gas hydrates that remain as transportable particles in a slurry. It is commonly believed that naturally occurring components in those crude oils alter the surface properties of gas hydrate particles when formed. The exact structure of the crude oil components responsible for this surface modification remains unknown. In this study, a successive accumulation and spiking of hydrate-active crude oil fractions was performed to increase the concentration of hydrate related compounds. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) was then utilised to analyse extracted oil samples for each spiking generation. Machine learning-based variable selection was used on the FT-ICR MS spectra to identify the components related to hydrate formation. Among six different methods, Partial Least Squares Discriminant Analysis (PLS-DA) was selected as the best performing model and the 23 most important variables were determined. The FT-ICR MS mass spectra for each spiking level was compared to samples extracted before the successive accumulation, to identify changes in the composition. Principal Component Analysis (PCA) exhibited differences between the oils and spiking levels, indicating an accumulation of hydrate active components. Molecular formulas, double bond equivalents (DBE) and hydrogen-carbon (H/C) ratios were determined for each of the selected variables and evaluated. Some variables were identified as possibly asphaltenes and naphthenic acids which could be related to the positive wetting index (WI) for the oils.

Naphthenic acid fraction components from oil sands process-affected water from the Athabasca Oil Sands Region impair murine osteoblast differentiation and function.

The extraction of bitumen from surface mining in the Athabasca Oil Sands Region (AOSR) produces large quantities of oil sands process-affected water (OSPW) that needs to be stored in settling basins near extraction sites. Chemical constituents of OSPW are known to impair bone health in some organisms, which can lead to increased fracture risk and lower reproductive fitness. Naphthenic acid fraction components (NAFCs) are thought to be among the most toxic class of compounds in OSPW; however, the effect of NAFCs on osteoblast development is largely unknown. In this study, we demonstrate that NAFCs from OSPW inhibit osteoblast differentiation and deposition of extracellular matrix, which is required for bone formation. Extracellular matrix deposition was inhibited in osteoblasts exposed to 12.5-125 mg/L of NAFC for 21 days. We also show that components within NAFCs inhibit the expression of gene markers of osteoblast differentiation and function, namely, alkaline phosphatase (Alp), osteocalcin, and collagen type 1 alpha 1 (Col1a1). These effects were partially mediated by the induction of glucocorticoid receptor (GR) activity; NAFC induces the expression of the GR activity marker genes Sgk1 (12.5mg/L) and p85a (125 mg/L) and inhibits GR protein (125 mg/L) and Opg RNA (12.5mg/L) expression. This study provides evidence that NAFC concentrations of 12.5mg/L and above can directly act on osteoblasts to inhibit bone formation and suggests that NAFCs contain components that can act as GR agonists, which may have further endocrine disrupting effects on exposed wildlife.

Highly efficient electro-cocatalytic Fenton-like reactions for the degradation of recalcitrant naphthenic acids: Exploring reaction mechanisms and environmental implications

In this study, an electrochemical/peroxymonosulfate/Fe(III) (EC/PMS/Fe(III)) system was established for efficient degradation of four naphthenic acids (NAs) compounds including cyclohexanecarboxylic (CHA), heptanoic (HPA), benzoic (BA) and 2-methylhexanoic acids (2-MHA). The introduction of electric field enhances the redox cycle of Fe(III)/Fe(II) to activate PMS for degredation of NAs. Complete degradation of NAs compounds (5 mg/L) has been achieved within 30 min in the EC/PMS/Fe(III) system. The results of electron paramagnetic resonance (EPR) analysis, scavenging experiment, and chemical probe experiments indicated hydroxyl radical (•OH), sulfate radical (SO4•−) and singlet oxygen (1O2) are primary reactive oxygen species (ROS) in the EC/PMS/Fe(III) system. NAs compounds with different structures exhibit inconsistent degradation efficiency in current system (kCHA > kBA > kHPA > k2-MHA), depending on the selectivity of the different ROS and stability of respective intermediate organic radicals. Besides, multiple degradation pathways of CHA, mainly including hydroxylation and carbonylation, were proposed by combining the results of mass spectrometry analysis with the calculated Fukui index based on density functional theory (DFT) calculation. In addition, the EC/PMS/Fe(III) system exhibited robust performance with the addition of co-existing ions. This work provides a novel strategy for efficient degradation of NAs for future remediation of petroleum wastewater.

The mechanistic investigation on the effect of the crude oil /brine interaction on the interface properties: A study on asphaltene structure

• The Asphaltene molecular Structure was determined by ATR and EDAX analysis. • the Asphaltene adsorption rate at the interface highly depends on the brine salinity. • compaction of the Asphaltene molecules Structure significantly affects the adsorption behavior of the Asphaltene. • The concentration of Asphaltene fraction in the crude oil has a key role in fluid–fluid interaction. • Asphaltene molecules accumulate at the oil-brine interface and perform the Asphaltene-ion-bound with the dissolved ions. Despite many attempts to study the interaction of fluids in low-salinity flooding, they do not examine the principles of interphasic transition phenomena. This study aims to provide a new understanding of liquid–liquid interactions during the low-salinity water interaction through a series of experiments on the oil, emulsion, and aqueous phase. Three samples of crude oils with different asphaltene concentrations and structures with known physical properties are in contact with different solutions. The brine pH, conductivity, and crude oil viscosity experiments before and after contacting the oil with brine showed that the heteroatom concentration and compaction of crude oil asphaltene fraction and the brine salinity affect the rate of the migration of crude oil polar component toward the interface. Moreover, the IFT measurement illustrated that interface interactions are affected by several parameters such as dissolved ion type, the concentration of the brine, and the concentration of the polar components in crude oil. The solubility of crude oil polar species such as naphthenic acids in the brine does not always increase by decreasing the salinity of the aqueous phase. To verify this important finding, UV–Vis spectroscopy and FTIR were performed on the brine and crude oils before and after in contact with each other.

Chemical Speciation of Naphthenic Acids in Brazilian Crude Oils by Advanced Analytical Techniques

Chemical Speciation of Naphthenic Acids in Brazilian Crude Oils by Advanced Analytical Techniques

Ultrasonic-Assisted Extraction of Toxic Acidic Components from Acidic Oil Using 1,8-Diazobicyclo[5.4.0]undec-7-ene-Based Ionic Liquids.

Ionic liquids (ILs) show remarkable performance in enhancing the naphthenic acid extraction efficiency and decreasing the extraction time. However, the ultrasonic-assisted IL-based extraction of naphthenic acid is merely addressed previously. Therefore, this study investigated the impact of essential ultrasonic parameters, including amplitude and time, on naphthenic acid extraction using different ILs, and the system was optimized for maximum extraction. The IL 1,8-diazobicyclo[5.4.0]-undec-7-ene (DBU) with thiocyanate anions revealed the highest efficiency in extracting naphthenic acid from a model oil (dodecane) at optimized conditions, and the experimental liquid–liquid equilibrium data were obtained at atmospheric pressure for the mixture of dodecane, [DBU], thiocyanate, and naphthenic acid. In addition, the influence of the chain length of the cation (hexyl, octyl, or decyl) on the extraction efficiency was also evaluated by determining the distribution coefficients, and the conductor-like screening model for real solvents (COSMO-RS) study was carried out at infinite dilution. It was found that [DBU-Dec] [SCN] gives the best extraction efficiency and has a distribution coefficient of 9.2707 and a performance index of 49.48. Based on these values, ILs can be ordered as follows: [DBU-Dec] [SCN] > [DBU-Oct][SCN] > [DBU-Hex][SCN] in the decreasing order of performance index 49.48, 41.58, and 28.13. Moreover, non-random two liquid and Margules thermodynamic models were employed to investigate the interaction parameters between the components. Both models showed excellent agreement with the experimental results and could successfully be used for ultrasonic-assisted IL extraction of naphthenic acid.

Electromembrane Extraction of Naphthenic Acids in Produced Water Followed by Ultra-High-Resolution Mass Spectrometry Analysis.

Naphthenic acids comprise one of the most toxic compounds of the produced water released from offshore oil platforms. Therefore, developing and applying faster, simpler, and more efficient analytical methods for analyzing naphthenic acids are urgently needed. Electromembrane extraction (EME) uses the electrokinetic migration of target ions through a porous membrane. Herein, the EME method was applied to extract naphthenic acids from produced water. The EME method was optimized, and the optimal conditions encompassed decanol as the organic solvent, the sample with pH 10.0, 5 min of extraction at 200 V, and the ratio 4:1 (borate buffer/matrix, v/v). Electrochemical impedance spectroscopy confirmed charged species' migration from produced water through the EME. Subsequently, all extracts were analyzed by ultra-high-resolution mass spectrometry. The EME efficiency was assessed by comparing the extraction results to the liquid-liquid extraction (LLE) method results. Analytical results showed good linearity for both solvent and matrix curves (R2 > 0.98). Low detection limits ranged from 0.10 to 0.13 μg mL-1 and quantification limits from 0.36 to 0.45 μg mL-1. Precision and accuracy values ranged from -13.3% to 16.5%. These values fit the proposed method, demonstrating that the EME was more efficient than LLE in naphthenic acid extraction. The EME method preferably extracted aromatic compounds with double-bond equivalence from 6 to 8. The EME coupled with ultra-high-resolution mass spectrometry was demonstrated as a promising analytical approach to naphthenic acid extraction as an efficient and more environmentally friendly alternative to conventional extraction methods.

Determination of naphthenic acids in produced water by using microchip electrophoresis with integrated contactless conductivity detection

This study reports for the first time the use of a microchip electrophoresis (ME) device with integrated capacitively coupled contactless conductivity detection (C4D) to analyze naphthenic acids in produced water. A mixture containing 9-anthracenecarboxylic, 1-naphthoic, and benzoic acids was separated and detected using a running buffer composed of 10 mmol L−1 carbonate buffer (pH = 10.2). The separation was achieved within ca. 140 s with baseline resolution greater than 2 and efficiency values ranging from 1.9 × 105 to 2.4 × 105 plates m−1. The developed methodology provided linear correlation with determination coefficients greater than 0.992 for the concentration ranges between 50 and 250 µmol L−1 for benzoic and 9-anthracenecarboxylic acids, and between 50 and 200 µmol L−1 for 1-naphthoic acid. The achieved limit of detection values varied between 4.7 and 7.7 µmol L−1. The proposed methodology revealed satisfactory repeatability with RSD values for a sequence of eight injections between 5.5 and 7.7% for peak areas and lower than 1% for migration times. In addition, inter-day precision was evaluated for sixteen injections (a sequence of four injections performed during four days), and the RSD values were lower than 11.5 and 4.9% for peak areas and migration time, respectively. Five produced water samples were analyzed, and it was possible to detect and quantify 9-anthracenecarboxylic acid. The concentrations ranged from 1.05 to 2.24 mmol L−1 with recovery values between 90.8 and 96.0%. ME-C4D demonstrated satisfactory analytical performance for determining naphthenic acids in produced water for the first time, which is useful for petroleum or oil industry investigation.

Effect of the structural characteristics of naphthenic acids on the corrosion kinetics of an AISI SAE 1005

Processing crudes with high naphthenic acid content causes corrosion problems on the crude oil distillation units. The total acid number (TAN) is commonly used to evaluate the corrosivity of crude oils; thus for decision-making related to corrosion mitigation and control in refineries. However, the TAN only represents the number of carboxylic groups present in the crude oil and does not consider the structural characteristics of the naphthenic acids, nor their reactivity, which are highly relevant to corrosion. On the other hand, the study of naphthenic acids as fractions with specific structural characteristics should enable the identification of differences in the corrosivity of crude oil with the same naphthenic acid concentration. In this research work, the fractioning of a commercial mixture of naphthenic acids was performed using the ionic strength of their respective salts. The structural characterization of the obtained fractions was conducted using Fourier-transform infrared and mass spectroscopy, gel permeation chromatography, and nuclear magnetic resonance. Furthermore, the corrosion rate of AISI SAE 1005 steel exposed to each fraction of naphthenic acids in the temperature range between 270 and 350 ºC was determined. Based on these results, a kinetic model of parallel reactions for predicting the concentration of dissolved iron in crude oil containing a mixture of naphthenic acids is proposed and validated.

Treatment of naphthenic acids in oil sands process-affected waters with a surface flow treatment wetland: mass removal, half-life, and toxicity-reduction

This study is the first to investigate the removal of naphthenic acids in a full-scale constructed wetland within the Alberta Oil Sands region. The average mass-removal efficiency for all O2-naphthenic acids measured in three separate deployments in the wetland ranged from 7.5% to 68.9% and appeared sensitive to physicochemical properties of the naphthenic acids, environmental conditions, and water quality. Treatment efficiency of individual naphthenic acids was found to increase with increasing carbon number and decreasing number of double bond equivalents in the molecule. Treatment efficiency was also found to increase with both higher initial turbidity in OSPW entering the wetland, and warmer average OSPW temperatures during wetland operation. Half-life times of naphthenic acids in the treatment wetland ranged between 8.9 and 39 days and were substantially lower than those in tailings ponds (i.e., 12.9–13.6 years) and laboratory studies focussed on bench-scale aerobic microbial biodegradation (i.e., 44–315 days). Using published dose-response data, biomimetic extraction measurements using solid phase microextraction fibers indicate that 14 days of wetland treatment resulted in a reduction in (4 d) deformity of Danio rerio from 50 to 16%, while exhibiting less than 1% toxic response for less sensitive toxic endpoints. The study concludes that wetland treatment is a feasible and productive treatment method for naphthenic acids in oil sands process-affected water due to a combination of sorption and biodegradation.

A novel functionalized ionic liquid [DOC4mim][DEHG] for impurity removal of aluminum in rare earth leaching solution

The separation of rare earth (RE) and aluminum (Al) has always been a practical challenge. In this article, a novel functionalized ionic liquid 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-imidazol-3-ium bis(2-ethylhexyl)glycinate ([DOC4mim][DEHG]) with high selectivity was developed for the impurity removal of Al from ion-adsorbed type RE ores leaching solution. In the sulfuric acid system, the ionic liquid extracted Al through an ion association mechanism. Salting out agent of Na2SO4 could change the stoichiometric number of extraction equilibrium. For the actual RE leaching solution, the inhibitory effect exhibited by Na2SO4 prevented more RE elements from being removed together with Al. Under the optimized extraction conditions, the removal rate of Al was more than 95%, also the recovery rate of RE was more than 96%. Compared with saponified industrial extractant naphthenic acid, it revealed better interface phenomenon and higher RE recovery performance. NaOH solution with low concentration could be used to strip and regenerate RE-loaded [DOC4mim][DEHG] at the same time. In five cycles, the extraction system maintained good reproducibility. There was no acid consumption in the separation process. This work provides a new insight into the efficient and sustainable removal of Al impurity from actual RE leaching solution.

Study on the mechanism of flotation of coal gasification fine slag reinforced with naphthenic acids

The impact of the collector and frother dosages on the separation of carbon and ash in coal gasification fine slag (CGFS) based on flotation using kerosene and compound collectors consisting of naphthenic acids and kerosene mixed at different ratios is investigated in this study. The physical properties of the original sample of CGFS, the residual carbon, and the ash material were investigated to characterize the differences in pore structure composition and element distribution among them, thereby illuminating the basis for flotation-based separation of residual carbon and ash material and the cause of the large reagent consumption. Furthermore, the mechanisms of interactions between CGFS particles, particles and bubbles in the aqueous phase were computed and analyzed using the extended DLVO theory. The results demonstrate that the energy barrier between concentrated particles disappeared, while the energy barrier between tailing particles remained. Experimental results showed that NK concentrate particles flocculated and adhered to bubbles earlier than other particles at 100 × 10−19 m, which were conducive to flotation. (The NK is a compound reagent consisting of naphthenic acids and kerosene mixed at different ratios). The above research results are helpful to clarify the separation mechanism of residual carbon and ash in CGFS and improve the flotation separation effect.

Vegetable Oils Based Ionic Liquids for Rare Earth Elements Recovery: A Techno-Economic Analysis

This study aims to evaluate the feasibility of the yttrium recovery from compact fluorescent lamp waste using methyltrioctylammonium peanut oil ([N1,8,8,8][PO]) compared to methyltrioctylammonium naphthenic acid ([N1,8,8,8][NA]) and tetraoctylphosphonium oleate ([P8,8,8,8][Oleate]) on a large scale. Based on the techno-economic analysis, the process was feasible on a large scale commercially due to changes in economic parameters such as gross profit margin (GPM), payback period (PBP), break-even point (BEP), break even capacity (BEC), cumulative net present value (CNPV), profitability index (PI), internal rate return (IRR), and return on investment (ROI) tend to be positive with the greatest profit when using [P8,8,8,8][Oleate] compared to [N1,8,8,8][NA] and [N1,8,8,8][PO] under ideal conditions and the use of [N1,8,8,8][PO] can still be profitable under non-ideal conditions with certain fluctuation limits.

Effects of asphaltenes on the photolytic and toxic behavior of bitumen and conventional oil products on saltwater

The effects of asphaltenes on the photolytic and toxic behavior of petroleum oil on seawater was investigated by exposing five original oils and their maltenes to solar irradiation for seven days. Polycyclic aromatic hydrocarbons (PAHs) experienced the fastest photo-oxidation, but negligible photolytic loss was observed for most normal alkanes and all the petroleum biomarkers from tri-cyclic to pentyl-cyclic terpanes in the test total oil and maltenes. The removal of most PAHs from some maltenes was greater than the corresponding total oils. Deasphalting process did not affect the characteristics of naphthenic acid fraction components (NAFCs) in all control samples. In all test oils, solar irradiation formed abundant NAFCs, in particular those only containing oxygen as the heteroatoms (Oo species). The formed Oo species were abundant in congeners having highly saturated congeners, and shifted to a lighter carbon number after exposed. Deasphalting process significantly enhanced the formation of Oo species (o from 2 to 4) for all test oils, in particular for the Cold Lake Blend and Bunker C. The toxicity of exposed maltenes was generally higher than the exposed total oil for most oils, suggesting the aqueous toxicity level was positively related to the formed NAFC intermediates.

Kinetics of Catalytic Decarboxylation of Naphthenic Acids over HZSM-5 Zeolite Catalyst

Naphthenic acids are naturally occurring carboxylic acids in crude oil with cyclic or aromatic rings in their structure. These carboxylic acids are responsible for the acidity of crude oil, leading to corrosion problems in refinery equipment and the deactivation of catalysts while creating a continuous need for maintenance. Therefore, removing naphthenic acids has become an important requirement in refining acidic crude oil. In this paper, experiments are conducted to investigate the use of HZSM-5 zeolite catalyst to reduce the total acid number (TAN) of a typical acidic crude oil obtained from Al-Fula blocks in Western Sudan. TAN is an important metric signifying the acidity of crude oil. A full factorial design of the experiment (DOE) framework enabled a better understanding of the efficacy of the catalyst at three parametric levels (reaction temperature: 250-270-300 °C, reaction time: 2-3-4 h, and oil:catalyst weight ratio: 20-22-25 g/g). The results demonstrate that the HZSM-5 zeolite catalyst provides up to 99% removal of naphthenic acids via the decarboxylation route. Additionally, the removal efficiency increases with increasing temperature and residence time. The acidity of the crude oil was shown to decrease after treatment with the catalyst for four hrs.; from 6.5 mg KOH/g crude to 1.24; 0.39 and 0.17 mg KOH/g at 250; 270 and 300 °C, respectively. A sharp decrease of TAN was observed at the oil catalyst mass ratio of 20 g/g at 250 °C, and almost complete conversion of acids was achieved after 4 hrs. Another experiment at 270 °C showed a converse relationship between the oil:catalyst ratio and acid removal; suggesting the activation of side reactions at higher temperature conditions catalyzed by excess acid. Finally; a Langmuir–Hinshelwood (LH) kinetic model has been developed to enable rapid prediction of the performance of the HZSM-5 zeolite catalyst for decarboxylation reaction. The model has also been validated and tested in ASPEN® software for future simulation and scalability studies.

Separation of aluminum from rare earth by solvent extraction with4-octyloxybenzoic acid

Leaching method is usually used to extract rare earth (RE) elements from ion adsorbed RE ores. In the leaching process, some impurities such as aluminum (Al) enter the leaching solution. The separation of Al from RE by carboxylic acid extractant 4-octyloxybenzoic acid (POOA) was studied in this article. By changing the pH value, temperature, solvent, saponification degree and other parameters, the extraction and separation performance of POOA in chloride system was systematically studied. Through specific extraction experiments and slope analysis, it can be seen that the stoichiometric ratio of POOA to Al is 3:1 during the extraction process. The separation factor of Al3+ and Pr3+ can reach about 160.00. Compared with easily emulsified naphthenic acid, POOA achieves better phase separation. The above results show that saponified POOA (S-POOA) has a good separation effect on Al and RE. Under the condition of low concentration stripping acid of 0.60 mol/L HCl, the developed extraction system can be almost completely stripped, and the stripping rate reaches 97.52%. The regenerated POOA can be directly used for the recycling extraction.