Acidic Oil Research Articles

Compositional Analysis of High-TAN Sudanese Crude Oil Using High-Resolution Mass Spectrometry and Study of the Effect of Temperature and Catalyst on Acidic Composition.

Sudanese Fula crude oil, from the western region, is considered highly viscous and acidic and contains high amounts of heteroatoms (N and O) but a low sulfur content. This work presents an original and comprehensive analysis of its molecular composition in addition to an investigation of the effect of temperature and catalyst on the treatment of the acid fraction. The analysis was performed using a high-resolution Fourier transform mass spectrometer and Orbitrap-Elite with different ionization methods. The results reveal that the Fula crude oil contains a high abundance of nitrogen composition homologue classes N[H], NO2[H], and NO[H]. Their hydrocarbon composition includes low to high aromatic hydrocarbons. The number of oxygen classes varies from acids containing monocarboxylic acids of O2 to acids of multiple carboxylic and phenolic group (CxHyO3 to CxHyO15) classes, which indicate a high content of acidic moiety of 0.765%. In addition to oxygen classes, the acidic fraction that is present as a NOx series indicates the presence of carboxylic carbazole acidic fraction. Low-temperature crude oil treatment at 200 °C decreases the intensity of acids. No significant reduction to low masses was observed; however, there was a clear reduction to high masses. At a high temperature of 350 °C, the carboxylic acid intensity increases (O2 classes), and thus, heating crude oil to 350 °C is unfavorable as it increases the amount of monocarboxylic acids, which are primarily responsible for corrosion in refinery units. Predicted TAN values of residual samples show a reduction in TAN of 62% using thermal treatment at 200 °C, whereas there is an increase in TAN of 5% at 350 °C. A great reduction in acidity results from catalytic treatment with a transition metal catalyst of cobalt and iridium complex. A reduction in all acidic oils is observed; however, the greater reduction is found in mono- and dicarboxylic acids. Catalytic treatment is shown to result in an 85% reduction in predicted TAN values.

Deep eutectic solvent (DES) assisted deacidification of acidic oil and retaining catalyst activity: Variables optimization and catalyst characterization

Deacidification is a critical step in alkali catalyzed transestrification of acidic oil for biodiesel production. In this work, optimization of the process variables and insights into the mechanisms of deep eutectic solvent (DES) assistance of deacidification of acidic oil catalyzed by Amberlyst 15 were investigated. Specifically, response surface methodology (RSM) and Box-Behnken Design (BBD) were employed to optimize the three process variables, namely temperature, catalysis loading, and molar ratio of methanol to oleic acid. Furthermore, the catalysts before and after used with and without DES assistance were characterized by FTIR and XRD in order to elucidate the chemical mechanisms involved in the process. Results showed that maximum deacidification rate (DR) of 98.02% was achieved in the deacidification process assisted by DES at the optimal process conditions (temperature 72.02ºC, catalyst loading 5.05 wt%, and methanol to oleic acid molar ratio 33.02), compared to 89.68% of the control (without DES assistance). Data analysis and verification results further confirmed the suitability of BBD and RSM methods in optimizing the process. More interestingly, dramatic higher catalytic activity (DR of 76.33% vs 64.16%) of Amberlyst 15 with DES assistance compared to that of the control after 4 cycles was observed. Finally, FTIR spectra confirmed that less water absorbed onto the surface of Amberlyst 15 with DES assistance was the major reason for higher DR and better catalyst reusability in comparison with the control.

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.

Biodiesel production from tucumã (Astrocaryum aculeatum Meyer) almond oil applying the electrolytic paste of spent batteries as a catalyst

Improper disposal of batteries can cause several environmental problems. Thus, this work aimed to apply the electrolytic paste (SB) of spent AA batteries as a catalyst. The SB was heat-treated (400 and 800 °C) and characterized by FTIR, XRF, XRD, TGA, SEM-EDX, titratable acidity, and soluble alkalinity. Although the thermal treatment changed the constituent phases, a majority presence of manganese and zinc was observed in the materials. The extracted tucumã almond oil was also characterized, showing a high percentage of saturated fatty acids (75%) and high acidity (9.25 KOH/g oil). The untreated SB showed higher acidity (0.02 mmol/g) and, consequently, higher catalytic activity in transesterification reactions, resulting in good conversions (>97%). Temperature and reaction time were the most significant parameters, according to ANOVA. SB also showed high catalytic activity in the esterification of oleic acid, achieving good conversions (96%). Thus, the electrolytic paste proved to be a potentially efficient and eco-friendly catalyst for biodiesel production, even from highly acidic oils.

Optimization of the Removal of Naphthenic Acids from Crude Oil via Catalytic Esterification

This study was carried out to ascertain the optimum parameters for maximum total acid number (TAN) reduction via catalytic esterification using chicken eggshell ash as catalyst. A central composite design (CCD) was created to optimize TAN reduction by varying temperature and catalyst weight %. The chicken eggshell ash was calcined and reactivated in a furnace at 900 °C for an hour. An oil solution (referred to as synthetic solution) of diesel was adulterated with the organic acid m-toluic which served as a representation for highly acidic oil. Titration using alcoholic potassium hydroxide (KOH) and an indicator (phenolphthalein) was used to deduce the total acid number of the synthetic solution before and after esterification. The optimum parameters for maximum TAN reduction obtained from the model were a temperature of 56.90 °C, a catalyst weight % of 11.45%, and a maximum TAN reduction of approximately 94%. Fourier Transform Infrared (FTIR) Spectroscopy also confirmed that TAN reduction had taken place as the peaks that represent the carbonyl group (C=O stretch at ~1605 cm-1) was reduced significantly.

First-principles calculations of carboxylic acid adsorption on carbonate surfaces: Chain size and aqueous interface effects

In enhanced oil recovery (EOR), low salinity water (LSW) is an essential condition to change wettability in carbonate reservoirs for organic compound desorption. However, the nature of the water–oil–carbonate interactions remains challenging. Accordingly, we performed first-principles calculations to determine the adsorption energies of the propanoic and octanoic acids on the calcite and dolomite surfaces with water interface and implicit solvation medium. Our results confirm that the Mg sites are less selective for adsorption of both acidic oil components, whereas the Ca sites keep retaining the acid molecules. The differentiated influence from the carbonate surfaces is enhanced through the aqueous environment. In presence of Mg, the aqueous environment may act mainly on the unoccupied electronic levels of the dolomite carbonate sites instead of the Ca sites in calcite, which in turn has a stronger interaction with the acid molecules. The effect of the acid chain size is less pronounced. The acid desorption process could be then reached from the carbonate sites as the surface hydrophilicity is mainly increased in dolomite, which has a favourable ionic exchange and water adsorption. Therefore, our simulation models help to shed light on some important interaction properties in complex water–oil–carbonate interfaces under LSW conditions for EOR.

Parts-Per-Million (Salen)Fe(III) Homogeneous Catalysts for the Production of Biodiesel from Waste Cooking Oils

This work describes the application of a library of iron(III)-salen catalysts in the production of biodiesel from vegetable oils. The conversion of neutral soybean oil is complete within two hours at 160–180 °C with low catalyst loading (0.10 mol%). A comparative screening reveals that the catalysts containing acetate as a fifth ligand are the most performing, and these have been conveniently used to convert acidic and waste cooking oils (WCO). WCOs were used as received without further purification to produce biodiesel in high yield (85–90%) under optimized conditions (2 h at 180 °C, catalyst loading 0.1 mol%, oil to alcohol molar ratio 1:20). The iron content in the lipophilic and hydrophilic phases of the crude mixture was investigated and the residual concentration in biodiesel was found to be in the order of 10–14 ppm, comparable to that contained in biodiesels from other sources.Graphical

Application of acidic ionic liquids for the treatment of acidic low grade palm oil for biodiesel production

Employing low quality feedstocks for biodiesel production can present cost reduction opportunities due to its wide availability and cost effectiveness. However, most low quality feedstocks have high free fatty acid (FFA) content which is not feasible for biodiesel production through direct transesterification due to soap formation. Thus, a pre-treatment step through FFA esterification could reduce the FFA content while simultaneously yielding fatty acid methyl esters (FAME). In this study, the catalytic activity of ten ionic liquids (ILs) were screened for the esterification of FFA in acidic crude palm oil (ACPO). 1‑butyl‑3-methylimidazolium hydrogen sulfate as IL exhibited the highest catalytic activity and was further investigated to determine the optimum operating parameters such as IL dosage, molar ratio, reaction temperature and time. Single factor optimization was employed for the laboratory scale batch esterification reaction. The FFA content was reduced from 10.77% to less than 1% using the following optimum conditions: 4% IL to oil, molar ratio of 10:1 (methanol to oil), 120 min reaction time and 60 °C reaction temperature. Under optimum conditions, the IL can be recycled five times with minimal loss in catalytic activity, highlighting its feasibility as an industrial catalyst for esterification of acidic oils and fats.

A Study on the Catalytic Technology for Reduction of Naphthenic Acid Compound from Acidic Crude Oil

The existence of naphthenic acid (NA) in acidic crude oil tends to corrode the oil refinery equipment. In this study, a catalytic deacidification reaction involving the deacidifying agent and the synthesised catalyst was aimed to eliminate NA from acidic crude oil. Diethanolamine-polyethylene glycol (DEA-PEG) was introduced as a deacidifying agent. The wet impregnation method was applied for synthesizing the calcium oxide catalyst doped by copper supported on alumina (Cu/Ca/Al2O3). The potential catalyst was characterised utilising field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), Brunauer-Emmett-Teller (BET), and X-ray diffraction spectroscopy (XRD). The parameters include deacidifying agent dosing, loading dopant ratio and catalyst calcination temperature were performed to enhance the catalytic deacidification process in this study. Data showed that the total acidic number (TAN) value for crude B met the PETRONAS requirement for the TAN value below one using 1500 mg/L of DEA-PEG assisted by Cu/Ca (10:90)/Al2O3 catalyst.

Effect of bacteria on oil/water interfacial tension in asphaltenic oil reservoirs

Microbial enhanced oil recovery (MEOR), due to the formation of biofilm and the presence of biosurfactants generated by microorganisms in the reservoir, can play a role in reducing interfacial tension (IFT) and wettability alteration. In this work, the fluid-fluid interaction by measuring the IFT has been evaluated for combining two EOR methods, including low salinity water and MEOR, due to the high importance of fluid-fluid interaction in EOR. GeoBacillus stearothermophilus has been used as a bacterium to study changes in IFT. The effect of different salts, including monovalent and divalent cations and anions at different salinities, on biosurfactant performance, is investigated using IFT measurements. Also, the type of oil is evaluated in terms of its acidic and basic properties on the performance of biosurfactants. According to the results of this study, injection of GeoBacillus stearothermophilus bacteria reduces interfacial tension in acidic oil by 10.26% and in basic oil by 5.26%. According to the results, increasing salinity in the presence of oil-containing asphaltene with basic properties increases the IFT of the solution containing GeoBacillus stearothermophilus bacteria, but in the presence of acidic oil, a decrease in IFT is observed. The most significant effect of reducing the IFT of acidic oil and solution containing GeoBacillus stearothermophilus is obtained in the presence of the following salts, respectively: CaCl2 > MgCl2 > NaCl. The results show that with increasing CaCl2 concentration, the IFT between basic oil and GeoBacillus stearothermophilus solution gradually increases. This ascending trend is in the presence of NaCl salt with a lower slope. However, in the presence of MgCl2 salt, dual behavior is observed before and after the concentration of 1000 ppm, so that before this concentration, the IFT increases and then decreases. The findings of this study can help for a better understanding of the interaction of bacteria with asphaltenic oils in the presence of effective salts for low salinity water injection. The results of this study showed that by combining low salinity water with bacteria, less IFT could be obtained than low salinity water or bacteria alone.

Effect of Olive Oil Acidity on Skin Delivery of Diclofenac: In Vitro Evaluation and Ex Vivo Skin Permeability Studies.

Olive oil is a vegetable oil which has been successfully used as a skin penetrating agent. Acidity of olive oil is considered as one of the characteristic properties of olive oil. Olive oil acidity was selected as a parameter under investigation for evaluation of skin permeability. The acidities of the three investigated olive oils are varying from 0.75±0.16 to 2±0.17. Olive oil with acidity equals 2.0 showed the highest skin permeation for 12 h and cutaneous deposition with significant difference compared to the permeation values of 0.75 and F1.4 acidities. Results of cutaneous secretion of cytokines suggested that higher penetration was accompanied higher cytokines' secretions. Olive oil with acidity equals 2.0 also showed more prominent skin changes which suggested to be due to acidity and fatty acids' content. These results suggest that olive oil might improve the epidermal permeability, which is more pronounced in highly acidic olive oil, through weakening of skin barriers followed by acting of cytokines on re-building effective barriers. Finally, based on the current study, highly acidic olive oil is more efficient skin permeation enhancer vehicle than less acidic ones and can be efficiently used in formulation of cutaneous drug delivery systems.

Title of the Paper: Tin-Doped Tungstophosphoric Acid Embedded on Zif-8 with Both Brönsted and Lewis Acid Sites: A Reusable Catalyst for Conversion of Acidic Oils to Biodiesel

Title of the Paper: Tin-Doped Tungstophosphoric Acid Embedded on Zif-8 with Both Brönsted and Lewis Acid Sites: A Reusable Catalyst for Conversion of Acidic Oils to Biodiesel

Integrated bioprocess for structured lipids, emulsifiers and biodiesel production using crude acidic olive pomace oils

Olive pomace oil (OPO), a by-product of olive oil industry, is directly consumed after refining. The novelty of this study consists of the direct use of crude high acidic OPO (3.4–20% acidity) to produce added-value compounds, using sn-1,3-regioselective lipases: (i) low-calorie dietetic structured lipids (SL) containing caprylic (C8:0) or capric (C10:0) acids by acidolysis or interesterification with their ethyl esters, (ii) fatty acid methyl esters (FAME) for biodiesel, and (iii) sn-2 monoacylglycerols (emulsifiers), as by-product of FAME production by methanolysis. Immobilized Rhizomucor miehei lipase showed similar activity in acidolysis and interesterification for SL production (yields: 47.8–53.4%, 7 h, 50℃) and was not affected by OPO acidity. Batch operational stability decreased with OPO acidity, but it was at least three-fold in interesterification that in acidolysis. Complete conversion of OPO into FAME and sn-2 monoacylglycerols was observed after 3 h-transesterification (glycerol stepwise addition) and lipase deactivation was negligeable after 11 cycles.

Continuous biodiesel production from acidic oil using a combination of the acid-, alkali-catalyzed membrane and GO/PVDF separation membrane

An integrated process of esterification with phosphotungstic acid/poly (ether sulfone) (PWA/PES) membrane, transesterification with alkalized polysulfone (APSF) membrane and Graphene Oxide/poly (vinylidene fluoride) (GO/PVDF) separation membrane was carried out to produce biodiesel from acidic oil. At the first step, the PWA/PES membrane was introduced to catalyze the esterification reaction. The morphology, maximum pore size, porosity and catalytic esterification performance of PWA/PES membrane were investigated. After the esterification, products and reactants without reaction were put into the GO/PVDF separation membrane to soybean oil and other substances. The permeation mixture flux and soybean oil rejection of the GO/PVDF separation membrane is 597.89 L/m2·h and 98.02%, respectively. At the second step, the APSF membrane was added to catalyze the transesterification reaction in which the soybean oil reacted with methanol. The results showed that the esterification conversion was 98.6% and transesterification conversion was 91.2%. The main parameters of the biodiesel product obtained meet the Chinese Standard (GB/T 20828) and European Standard (EN 14214).

Efficient naphthenic acid extraction from high acidic oil using novel 1,5-diazabicyclo[4.3.0]non-5-ene based ionic liquids

In this work, the high acidic crude oil deacidification study was performed with novel 1-alkyl-1,5-diazabicyclo[4.3.0]non-5-ene (DBN) based ionic liquids (ILs). Firstly, we took advantage of the systematic COSMO-RS (Conductor-like Screening Model for Real Solvents) calculations to screen the possible ILs with good acid extraction performance from the combinations of 94 cations and 56 anions. Four 1-alkyl-1,5-diazabicyclo[4.3.0]non-5-enium imidazolide ([DBN-R][IM]) ILs with varying alkyl chains were eventually identified and synthesized successfully. Their deacidification performances were tested experimentally and different factors, including the alkyl chain length, ILs/oil mass ratio, temperature, and the initial total acid number (TAN) value of the simulated acidic oil, were also studied in detail. The experimental results showed that [DBN-R][IM] exhibited excellent performances on naphthenic acids (NAs) removal and [DBN-Et][IM] could achieve 93% of NAs removal employing the ILs/oil mass ratio of 0.06 at room temperature for the acidic oil with the TAN value of 3.28 mg KOH/g. COSMO-RS analyses were also used to elucidate the unusual effects of the alkyl chain length and temperature on the NAs extraction performances. Additionally, a two-step deacidification strategy was proposed aiming at realizing more efficient NAs extraction. Finally, density functional theory (DFT) calculations were carried out and the independent gradient model (IGM) analyses were applied to the IL-NAs system to get insight into the deacidification mechanism of the ILs.

An effective strategy for waste oil deoxygenation and upgrading for hydrocarbon biofuels production: A computational and experimental investigation

Waste oil, like waste cooking and acidic oil, are two promising carboxylic acids feedstocks that can be converted into hydrocarbons by the pyrolytic method, usually through DCO2 and DCO processes. DFT is employed to investigate the deoxygenation mechanism using octanoic acid as a model compound in this work. Additionally, pyrolysis of the above samples was carried out at atmospheric pressure, temperature below 773.15K. GC-MS, GC and TG-FTIR-MS test measures were used to analyze pyrolytic products. The DFT results reveal that pyrolysis conversion of waste oil was a direct and effective deoxygenation method. And high alkene content endowing pyrolytic oil greatly potential to upgrade for high-quality biofuel production. Finally, pyrolytic oil was upgraded by SAPO-11-Pd/C can increase the components of iso-hydrocarbons, further can faction cut to obtain three biofuel fractions. Fraction blending with fuels could decrease the cold filter plugging point of final fuels, dramatically improving the commercial value of pyrolytic oil and effectively solving the waste oil disposal problem.

Deformation and breakup mechanism of water droplet in acidic crude oil emulsion under uniform electric field: A molecular dynamics study

If the critical field strength (Ec) is exceeded, the droplets in water-in-oil (W/O) emulsions would undergo severe electrodispersion during the electric dehydration. Naphthenic acid (NA) is an essential constituent of acidic crude oil. To reveal the mechanisms behind the deformation and breakup of water droplets in acid-containing emulsions, a molecular dynamics method was employed to investigate the motor behavior of a single water droplet at different field strengths. Weak interaction analysis indicated that naphthenic acid formed a strong hydrogen bond (H-bond) with water, and a low-intensity dispersion attraction with n-hexane. The carboxyl group on NA was mainly adsorbed on the surface of droplet via electrostatic interaction, and the H-bond between the two has a lifetime of 2.14 ps at 0.6 V nm−1 field strength (E). Despite the presence of NA, H2O and ions are crucial factors influencing droplet deformation and breakup, respectively. The radius of gyration may allow for quantitatively evaluating the degree of droplet breakup. Potential energy analysis showed that the Coulomb interaction between NA molecules significantly affected their migration in the system. The dipole moment of NA driven by external electric field is parallel to the field direction. Our studies provide a molecular-level framework for understanding the movement of water droplets in acid-containing oil under applied electric field.

A microfluidic study of oil displacement in porous media at elevated temperature and pressure

Microfluidics methods offer possibilities for visual observations of oil recovery processes. Good control over test parameters also provides the opportunity to conduct tests that simulate representative reservoir conditions. This paper presents a setup and procedure development for microfluidic oil recovery tests at elevated temperature and pressure. Oil recovery factors and displacement patterns were determined in single- or two-step recovery tests using two crude oils, high salinity salt solutions and low salinity surfactant solutions. Neither the displacement pattern nor the recovery factor was significantly affected by the pressure range tested here. Increasing temperature affected the recovery factor significantly, but with opposite trends for the two tested crude oils. The difference was justified by changes in wettability alteration, due to variations in the amounts and structure of the acidic and basic oil fractions. Low salinity surfactant solutions enhanced the oil recovery for both oils.

Encapsulated deep eutectic solvent for esterification of free fatty acid

A novel encapsulated deep eutectic solvent (DES) was introduced for biodiesel production via a two-step process. The DES was encapsulated in medical capsules and were used to reduce the free fatty acid (FFA) content of acidic crude palm oil (ACPO) to the minimum acceptable level (< 1%). The DES was synthesized from methyltriphenylphosphonium bromide (MTPB) and p-toluenesulfonic acid (PTSA). The effects pertaining to different operating conditions such as capsule dosage, reaction time, molar ratio, and reaction temperature were optimized. The FFA content of ACPO was reduced from existing 9.61% to less than 1% under optimum operating conditions. This indicated that encapsulated MTPB-DES performed high catalytic activity in FFA esterification reaction and showed considerable activity even after four consecutive recycling runs. The produced biodiesel after acid esterification and alkaline transesterification met the EN14214 international biodiesel standard specifications. To our best knowledge, this is the first study to introduce an acidic catalyst in capsule form. This method presents a new route for the safe storage of new materials to be used for biofuel production. Conductor-like screening model for real solvents (COSMO-RS) representation of the DES using σ-profile and σ-potential graphs indicated that MTPB and PTSA is a compatible combination due to the balanced presence and affinity towards hydrogen bond donor and hydrogen bond acceptor in each constituent.

Mechanism for enhanced oil recovery from carbonate reservoirs by adding copper ions to seawater

In existing or operating oil fields, enhanced oil recovery (EOR) methods are employed to increase production, which can contribute to meet fossil fuel demand. This research proposes a new EOR method by adding Cu(II) ions into the injected seawater, which shows a significant incremental oil production in carbonate reservoirs. An important remark in this study is the Cu(II) incorporation into the cores, with mineralization of atacamite on the carbonate surface, and copper complexation with the acid fraction of the oil. In addition, we observed oil removal up to the last monolayer on calcite surfaces. Based on these observations and first-principles calculations, we propose an EOR mechanism where the acidic oil desorbs from the rock surface by forming acid-copper complexes that are dragged by the injected fluids. In summary, we propose a simple and cost-effective EOR method with transition metals, which may significantly increase the yield of low-recovery carbonate reservoirs and reduce the environmental impact of exploring new reservoirs.