Acidic Oil Research Articles

Biodiesel production via simultaneous transesterification and esterification reactions over SrO–ZnO/Al2O3 as a bifunctional catalyst using high acidic waste cooking oil

A simultaneous transesterification and esterification process was applied for production of biodiesel from high acidic waste cooking oil containing 18 wt% FFA using a range of heterogeneous bifunctional strontium–zinc–aluminium catalyst. The influence of the molar ratio of metal oxide, the ethanol to waste oil molar ratio, temperature and time of reaction, catalyst dosage, and free fatty acids in the feedstock on the conversion of biodiesel were studied. High interaction between Sr, Al and Zn metal was recognised to promote catalyst performance. A high interaction and mixing of strontium, aluminium and zinc oxides enhanced and increased the active sites on the surface of acid and base. The catalyst with a 2.6:1 M ratio of strontium to zinc was found to perform the best to transesterify the glycerides and esterify the fatty acid in the used oil simultaneously. The catalyst exhibited higher catalytic activity with high acidity waste cooking oil, with 95.7% reaction conversion at the optimum conditions 10:1 ethanol to waste oil molar ratio, 15 wt% catalyst dosage, and 5 h reaction time at 75 °C reaction temperature. The used catalyst showed low reusability due to high leaching of strontium.

One-pot conversion of highly acidic waste cooking oil into biodiesel over a novel bio-based bi-functional catalyst

We developed a KOH/corncobs-derived activated carbon (AC) heterogeneous catalyst for the single stage biodiesel production from highly acidic waste vegetable oil, which was active in both the esterification and transesterification reactions. Among the different AC preparation conditions tested, a sulfuric acid to raw corn cobs (volume/weight) ratio of 5:1, activation temperature and time of 600 °C for 1 h were selected as the best conditions. The specific surface area (SSA) was 627 m2/g but among all the samples, the highest SSA was however 1131 m2/g. The main factors affecting the simultaneous esterification-transesterification were investigated with a full factorial design combined with response surface methodology via central composite design. The optimum conditions were 1 h reaction time, 18:1 methanol:oil molar ratio, 1 wt% catalyst loading and 45 °C temperature, at which the yield was 97.8%. The biodiesel obtained, in such conditions, matched the ASTM standards. The catalyst was stable for up to five successive times to catalyze esterification, but KOH leached easily and the catalyst became inactive in the transesterification.

Grafting copolymerization of dual acidic ionic liquid on core-shell structured magnetic silica: A magnetically recyclable Brönsted acid catalyst for biodiesel production by one-pot transformation of low-quality oils

The objective of the current research is to prepare an efficient and magnetically separable Brönsted acid catalyst for one-pot transformation of low-quality oils to biodiesel. In this premise, the core–shell structured magnetic composites were firstly prepared by coating of silica shells on magnetic Fe3O4 nanoparticles. Thereafter, the grafting copolymerization of dual acidic ionic liquids (ILs, 1-vinyl-3-(3-sulfopropyl)imidazolium hydrogen sulfate as an monomer and 1.4-butanediyl-3,3′-bis-1-vinylimidazoliu hydrogen sulfate as a cross-linker agent) on the magnetic silica composite was conducted to impart the richer Brönsted acidic functionality on the support. The detailed catalyst characterization results showed that the magnetic silica support was really formed, and moreover the polymeric acidic ILs were successfully grafted on the magnetic support. The so-prepared solid catalyst had a large surface acidity (3.93 meq H+/g) and strong magnetism (27.5 emu/g). Benefiting from the synergism between the polymeric ILs and magnetic porous support, this developed catalyst displayed good catalytic activities toward both the transesterification of soybean oil and esterification of free fatty acids (FFAs), which endowed it to be a robust solid acid catalyst for one-pot biodiesel production from low-quality acidic oils. The solid catalyst could be simply recovered by an external magnet with minor loss of catalytic activity within five cycles, and further showed insensitivities to moisture and FFAs present in the feedstocks, possessing both economic and environmental advantages for the application in biodiesel production especially from the low-quality oils.

Electrochemical and Anticorrosive Behavior of Synthesized Diimine-Based Compound on X80 Steel in Acidic Oil and Gas Well Treatment Fluids at Different Temperatures

A green compound, N,N′-bis(2,4,6-trihydroxybenzaldehyde)-2,2-dimethylpropandiimine, was studied as an acid corrosion inhibitor for X80 steel. Aqueous 15% HCl was utilized for simulating the oil well acidizing fluid at various temperatures. The inhibition performance was assessed using the weight loss method, the electrochemical impedance, the polarization, and the scanning electron microscopy. Polarization investigations showed that the studied diimine inhibitor delays both the cathodic and anodic reactions over chemical adsorption and blocks the active corrosion sites. The adsorption procedure was performed physically as best estimated using the Langmuir adsorption isotherm. It was observed that, the adsorption process was spontaneous and exothermic in the direction of a rise in the bulk phase entropy. The efficiency of the inhibitor was reduced by increasing temperature and raised with an increasing amount of the inhibitor. Impedance data indicated that as the inhibitor amount enhanced the charge transfer resistance of steel also increased while the double layer capacitance decreased. Kinetic and thermodynamic factors such as the activation energy, enthalpy, entropy and the Gibbs free energy of activation and adsorption were computed. Scanning electron microscopy was utilized to examine the steel surface in the presence or the absence of the inhibitor, showing excellent surface protection by the studied inhibitor.

Preparation and properties study of graphene-enhanced acid-resistant anticorrosion coating for subsea oil and gas

In order to solve the corrosion problem of the existence of acidic material such as H2S, CO2 in the subsea pipelines, this article studied the coating film forming matter, which is combined with phenolic epoxy resin and phenolic aldehyde amine, acid-resistant filler system, etc. With the addition of the graphene dispersion, it significantly improves the abrasive resistance, salt fog resistance, adhesion and chemical character. This article took out the coating with good acid resistance. The results showed that the acid-resistant anticorrosion coating enhanced by graphene has excellent comprehensive physical and chemical properties, such as salt fog resistance, chemical resistance, hydrogen sulfide corrosion resistance, and alkali resistance, which meet the corrosion protection requirements of H2S and CO2 in acidic oil and gas fields subsea pipelines.

A new kinetic model for simultaneous interesterification and esterification reactions from methyl acetate and highly acidic oil

This work presents the development of a kinetic model for simultaneous reactions of esterification and interesterification from macaw oil and methyl acetate using γ-alumina as the heterogeneous catalyst. Experimental data varied between 225 °C and 300 °C, catalyst concentration of 2 wt%, 5 wt%, and 10 wt% and molar ratio (methyl acetate: Oil) of 10:1, 20:1 and 40:1. Arrhenius kinetic parameters were concomitantly estimated for all experimental conditions by minimizing the objective using a hybrid optimization algorithm. From the results, it could be verified that γ-alumina is an active catalyst for both interesterification and esterification reactions with MeA and a high acid glyceride source. The simultaneous reaction system indicated an endothermic character at experimental conditions investigated. The FAME conversions presented a strong limitation of chemical equilibrium. Moreover, it could be verified that the esterification reaction produces about 80% of total fatty acid methyl esters and that acetic acid played the main role as a reagent through reactions with glycerine acetates and not as a catalyst. The proposed kinetic model satisfactorily fitted the experimental results.

Synthesis of heterogenized polyoxometalate-based ionic liquids with Brönsted-Lewis acid sites: A magnetically recyclable catalyst for biodiesel production from low-quality oils

The aim of this study is to develop a magnetically recyclable acid catalyst for biodiesel production from low-quality acidic oils. To achieve this, polyoxometalate (POM)-based sulfonated ionic liquids (ILs) bearing Brönsted-Lewis acid sites, namely (Py-Ps)PMo, were firstly prepared by reaction of pyridine with 1,3-propanesultone, followed by anion exchange with phosphomolybdic acid (HPMo). Thereafter, the so-prepared ILs were loaded on the amino-functionalized metal–organic framework (CoFe2O4/MIL-88B(Fe)-NH2) to synthesize the recoverable solid catalyst. The obtained CoFe2O4/MIL-88B(Fe)-NH2/(Py-Ps)PMo catalyst was characterized by several techniques, which provided an evidence that the acidic ILs were loaded on the magnetic support by strong charge interaction effect. This catalyst showed highly catalytic activities toward the transesterification of soybean oil and esterification of free fatty acids (FFAs), making it to be applicable for one-pot production of biodiesel from low-quality acidic oils. The catalytic performance was originated from the combination of the characteristics of Brönsted-Lewis acid sites and porous structure of the support. Moreover, the catalyst could be simply recovered by a permanent magnet and reutilized for several times with no remarkable attenuation of catalytic activity. Thus, the IL based solid catalyst possessed the potential of efficient and environmentally benign production of biodiesel practically from the low-quality oils.

Catalytic study of Ni/Ce/Al2O3 and Ni/Ca/Al2O3 on the removal of naphthenic acid from petroleum crude oil utilizing sodium thiocyanate in ethanol

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.

Impact of arbuscular mycorrhizal fungi and Pseudomonas fluorescens on growth, physiological parameters and essential oil content in Ocimum basilicum L.

A pot experiment was performed to see the interactive potential of Glomus mosseae and Acaulospora laevis alone or in combination with Pseudomonas fluorescens on Ocimum basilicum L. under glass house conditions. Various morphological and physiological parameters were measured after 120 days. Although, all co-inoculation treatments showed beneficial effects but G. mosseae is found to be the most compatible strain found in the rhizosphere of basil plant. G. mosseae alone or in combination with other bioinoculants showed maximum increase in all the different parameters studied (plant height, fresh weight, dry weight, leaf number, inflorescence height, root and shoot phosphorus, acidic and alkaline phosphatase and oil content). The overall results demonstrate that the co-inoculation of P. fluorescens with AM fungi promotes higher mycorrhizal colonization enhancing nutrient acquisition especially phosphorus (P), producing plant growth hormones resulting in improvement of rhizospheric condition of soil, altering the physiological and biochemical properties of sweet basil.

Impact of Acid and Base Numbers and Their Ratios on Wettability Alteration of the Calcite Surface

Alteration of rock wetting preference toward a more favorable wetting state has been identified as the primary mechanism of oil recovery from intermediate and oil-wet carbonate rocks. In order to produce a favorable wetting state, it is critical to have a clear picture of the initial wetting properties of the rock surface. This study aimed to improve the understanding of carbonate wettability by examining the impact of acid, base, and their mixture on wettability of calcite surfaces using different analytical tools (contact angle measurements, zeta potential test, Fourier transform infrared spectroscopy, interfacial tension measurements, and fluorescence ultraviolet spectroscopy). The acid number (AN) and the ratio of the basic component (quinoline) to the acidic component (stearic acid) were systematically varied in model oil solutions to elucidate the effect of simultaneous presence of the acid and base on the wettability alteration process. The results showed that as the acid concentration increases, the wettability alteration toward the oil-wet state is enhanced. However, the impact of the base was significant at high concentrations, where the wettability was changed toward the neutral state. Addition of the basic compound to the acidic model oil hindered the impact of stearic acid on wettability alteration. Although the impact of the basic component on wettability alteration of calcite seems to be weaker than that of the acidic component, presence of the base can alter the wetting characteristics of the surface. Acid and base concentrations and their ratio dictate the extent of calcite wettability alteration. Slight impact of the base on the wettability alteration process was observed for a system with an AN of 0.25. However, at higher ANs, an increase in the base number (BN) to AN ratio from 0 to 1 resulted in a remarkable reduction in the contact angle; while the contact angle increased again when the BN to AN ratio was 4. Further investigations (for systems with AN = 1) revealed that at the BN to AN ratio of 0.25 and 1, adsorption of the basic component on the surface was unlikely to happen. Formation of an acid–base complex could hinder the access of stearate ions to the calcite surface. At the BN to AN ratio of 1, the quinoline concentration was equal to that for stearic acid, which may enhance the acid–base interactions; hence, more stearic acid would be involved in acid–base complexes. However, once the base concentration became higher than the acid concentration (BN to AN = 4), an excess amount of the base, which was not involved in the complex mixtures with acid molecules, might adsorb on the surface.

Esterification of Free Fatty Acids with Glycerol within the Biodiesel Production Framework

Companies in the field of the collection and treatment of waste cooking oils (WCO) for subsequent biodiesel production usually have to cope with high acidity oils, which cannot be directly transformed into fatty acid methyl esters due to soap production. Since glycerine is the main byproduct of biodiesel production, these high acidity oils could be esterified with the glycerine surplus to transform the free fatty acids (FFA) into triglycerides before performing the transesterification. In this work, commercial glycerol was esterified with commercial fatty acids and commercial fatty acid/lampante olive oil mixtures over tin (II) chloride. In the first set of experiments, the esterification of linoleic acid with glycerol excess from 20 to 80% molar over the stoichiometric was performed. From 20% glycerol excess, there was no improvement in FFA reduction. Using 20% glycerol excess, the performance of a biochar obtained from heavy metal-contaminated plant roots was compared to that of SnCl2. Then, the effect of the initial FFA content was assessed using different oleic acid/lampante olive oil mixtures. The results illustrated that glycerolysis was impeded at initial FFA contents lower than 10%. Finally, the glycerolysis of a WCO with 9.94% FFA was assayed, without success.

Sono-dispersed MgO over cerium-doped MCM-41 nanocatalyst for biodiesel production from acidic sunflower oil: Surface evolution by altering Si/Ce molar ratios

In the present work, Mobil Composite Material no. 41 (MCM-41) utilized as the catalyst support for biodiesel production from Waste Cooking Oil (WCO). Different amounts of Si/Ce molar ratios (5, 10, 25, 50 and Ce = 0) introduced to the MCM-41 structure to synthesize the bifunctional nanocatalysts and achieve a modified support of high stability and acidity. Then, ultrasound used to disperse MgO active phase on support surface. The prepared nanocatalysts were investigated using various techniques as follows: XRD, EDX, TEM, FESEM, FTIR and BET. The XRD patterns along with the results of FTIR and BET analysis revealed the MCM-41 framework destruction while increasing the Ce content. The FESEM images of the nanocatalysts illustrated a well distribution and uniform morphology for the Mg/CeM (Si/Ce = 10). The particle size and size distribution of the Mg/CeM (Si/Ce = 10) were subsequently determined by TEM and FESEM images. Biodiesel production carried out under following constant operational parameters to evaluate catalytic performance of synthesized samples: T = 70 °C, catalyst loading = 5 wt%, methanol/oil molar ratio = 9, and 6 h reaction time. Ce substitution in support framework considerably enhanced the biodiesel conversion. The Mg/CeM (Si/Ce = 10) nanocatalyst demonstrated the highest conversion of 94.3%. The reusability of the Mg/CeM (Si/Ce = 10) studied in seven reaction cycles and biodiesel conversion reached to 88.7% at the end of seventh cycle which demonstrated its significant stability.

Thermochemical conversion of waste acidic oil into hydrocarbon products over basic composite catalysts

Removal of oxygen atoms from triglycerides is the most important step in their conversion into hydrocarbons. Basic catalysts have proven to be highly efficient in deoxygenation, whereby the oxygen atoms are removed in the form of CO and CO2, yielding pyrolytic oil with acid number below 10 mg KOH⋅g−1. We have now investigated the deoxygenation abilities of composite basic catalysts during the thermochemical conversion process. The dynamics of the catalytic cracking reaction using metal oxides, such as calcium oxide, in the presence of sodium carbonate, has been tested. According to thermogravimetric analysis (TGA) data, the activation energy for catalytic cracking was influenced by cations. By using calcium oxide as a catalyst, the activation energy was reduced from 260 kJ/mol to 185 kJ/mol, leading to a reduction in the reaction temperature of approximately 20–40 °C. The yield of the cracked liquid fraction was of the order of 66–70%, more than 90% of which could be recovered as liquid hydrocarbons. The results presented herein indicate an alternative reaction pathway, allowing thermochemical conversion to be conducted at a lower operational temperature, which would be beneficial for industrial production with lower energy consumption.

Catalytic Deacidification of Vacuum Gas Oil by ZnO/Al2O3 and Its Modification with Fe2O3

High acidic vacuum gas oil (VGO) decreases product quality and causes corrosions. To overcome these problems, catalytic esterification was utilized for the deacidification of VGO. A series of Al2O3-supported ZnO catalysts, undoped and doped with Fe2O3, were prepared and characterized. The results showed that both the ZnO/Al2O3 and the ZnO/Al2O3 doped with Fe2O3 had good deacidification effects with glycol for the 4th VGO. The deacidification rate reached 95.1% and 97.6%, respectively, under mild conditions (catalysts 2.5 wt%, glycol dosage 4.0 wt%, 250 °C and 1 h). The naphthenic acids were transferred into ester, which was proved by the Fourier Transform Infrared (FT-IR) and 1H nuclear magnetic resonance (NMR).Reusability of the catalyst for the esterification reaction was also studied. It was found that the deacidification rate was still over 90% after six reruns.

Facile tuning of the mechanical properties of a biocompatible soft material

Herein, we introduce a method to locally modify the mechanical properties of a soft, biocompatible material through the exploitation of the effects induced by the presence of a local temperature gradient. In our hypotheses, this induces a concentration gradient in an aqueous sodium alginate solution containing calcium carbonate particles confined within a microfluidic channel. The concentration gradient is then fixed by forming a stable calcium alginate hydrogel. The process responsible for the hydrogel formation is initiated by diffusing an acidic oil solution through a permeable membrane in a 2-layer microfluidic device, thus reducing the pH and freeing calcium ions. We characterize the gradient of mechanical properties using atomic force microscopy nanoindentation measurements for a variety of material compositions and thermal conditions. Significantly, our novel approach enables the creation of steep gradients in mechanical properties (typically between 10–100 kPa/mm) on small scales, which will be of significant use in a range of tissue engineering and cell mechanosensing studies.

Biodiesel Production from Acidic Oils Using Polyoxometalate-Based Sulfonated Ionic Liquids Functionalized Metal–Organic Frameworks

An efficient and recyclable catalyst, namely phosphomolybdenum-based sulfonated ionic liquids (ILs) functionalized MIL-100(Fe) metal–organic framework (AIL/HPMo/MIL-100(Fe)), was developed for the production of biodiesel via the transesterification-esterifications of acidic oils. For this goal, the MIL-100(Fe) metal–organic framework (MOF) was initially modified with phosphomolybdic acid (HPMo), and then the acidic ionic liquid (AIL) was immobilized on the prepared HPMo/MIL-100(Fe) composite through ion-exchange of 1-(propyl-3-sulfonate)imidazolium hydrogen sulfate with HPMo. The as-developed AIL/HPMo/MIL-100(Fe) catalyst possessed enhanced surface acidities, endowing the merits of Lewis and Bronsted acids with a heterogeneous microreactor of MOFs and favoring the better catalytic performance. The characterization results corroborated that the polyoxometalate-based ILs were incorporated into the MIL-100(Fe), and the porous structure of the MIL-100(Fe) maintained nearly unchangeable after the synthesis processes. The AIL/HPMo/MIL-100(Fe) catalyst could perform simultaneous transesterification of soybean oil and esterification of free fatty acids (FFAs) with long-term catalytic durability. The conversion of acidic oils using this solid catalyst gave 92.3% oil conversion for the transesterification of soybean oil and full FFA conversion for the esterification of FFAs with the methanol/oil molar ratio of 30:1 at 120 °C, showing potential applications for the production of biodiesel particularly from acidic oil feedstocks. Synopsis: Phosphomolybdenum-based sulfonated ionic liquids (ILs) functionalized MIL-100(Fe) metal–organic framework composites are fabricated and then utilized as efficient and recyclable catalysts for the production of biodiesel via one-pot transesterification-esterifications of acidic oils.

The role of CO2 and ion type in the dynamic interfacial tension of acidic crude oil/carbonated brine

The effects of CO2 and salt type on the interfacial tension (IFT) between crude oil and carbonated brine (CB) have not been fully understood. This study focuses on measuring the dynamic IFT between acidic crude oil with a total acid number of 1.5 mg KOH/g and fully CO2-saturated aqueous solutions consisting of 15,000 ppm of KCl, NaCl, CaCl2 and MgCl2 at 30 °C and a wide range of pressures (500–4000 psi). The results of IFT measurements showed that solvation of CO2 into all the studied aqueous solutions led to an increase in IFT of acidic crude oil (i.e., comparison of IFT of crude oil/CB and crude oil/brine), while no significant effect was observed for pressure. In contrast, the obtained results of studied salts indicated a positive effect on the IFT reduction of acidic crude oil/carbonated water (CW) (i.e., comparison of IFT of crude oil/CB and crude oil/CW).

Technology of acid-bearing oil with phytocomponents

The assortment of butter in Russia traditionally contained anhydrous butter produced by the method of knocking cream. At present, butter is produced to a greater extent by the conversion of high-fat cream. On the shelves of stores, besides the sweetening and acidic oils, you can see butter butter with the addition of additional flavor components. Fito components have high antioxidant properties and are widely used in the food industry. Introduction to the product of this recipe ingredient allows you to enrich the product with valuable nutrients and increase the stability of the latter when stored. The recipe of oil of the acidic and phytocomponents containing high-fat cream, leaven, salt, cooked phytocomponents, vitamins, stabilizer, emulsifier is proposed. The phytocomponent composition includes a dry mixture of parsley, dill and porridge. It is of interest to study the antioxidant activity of phyto-components. The dried parts of the plants were shredded to a particle size of 2.5 ± 1.5 mm. Plant extracts were obtained by maceration using distilled water. The extracts were filtered before the study. An indicator of the antioxidant activity of the aqueous extract of phyto-components was determined – 0.271 mg / g. A comparison of the obtained results with known indices of other plants is carried out. As the objects of comparison took the most used herbs in the food industry: sweet, saffron, thyme, St. John's wort, chamomile chemist, melissa. It has been established that the mixture of dill, parsley and porridge meal has a high antioxidant index and minimal restrictions when used. The optimal dosage of the mixture of herbs is 1.0 – 1.5 % and food cooking salt – 1 % (indicator according to GOST 32899–2014 for greenery and their mixtures is 0.5 – 8.0 %, for sodium chloride – no more than 2 %) The technology of production of oxygen-containing oil with phytocomponents is developed. The indicators of its quality have been studied, the shelf life of the oil has been determined.

Oil-in-water emulsification of Athabasca bitumen with pyrrolidine solution

This paper presents an experimental study of use of pyrrolidine solutions to induce the oil-in-water (o/w) emulsion of Athabasca bitumen without using synthetic surfactants. Pyrrolidine, an organic alkali, acts not only as an alkali that generates natural surfactants from acidic oil components in bitumen, but also as a cosolvent that improves the fluidity of the o/w emulsions.Experimental results show that the o/w emulsions created by pyrrolidine solutions can result in a large mobility increase of bitumen because of their low viscosity and high bitumen content. O/w emulsions were observed at low pyrrolidine concentrations (below 20 wt% and as low as 0.5 wt%) and low salinities (0 and 1000 ppm). For example, the sample of 0.5 wt% pyrrolidine in 1000-ppm NaCl brine with 7:3 water-oil-ratio showed a single-phase o/w emulsion at all experimental temperatures from 298 K to 373 K. In comparison to the original bitumen, the o/w emulsion was 4–6 orders of magnitude less viscous at 298 K, 2–3 orders of magnitude less viscous at 323 K, and 1–2 orders of magnitude less viscous at 353 K.The affinity of the organic alkali for asphaltic bitumen is important for o/w emulsification at a wide range of temperatures. Pyrrolidine is superior to the other organic alkalis tested, diethylamine and triethylenetetramine, likely because the cyclic structure makes pyrrolidine more compatible with the asphaltic bitumen. The favorable result with pyrrolidine is also confirmed by the Hansen solubility dispersion parameter.

Low salinity water flooding in high acidic oil reservoirs: Impact of pH on wettability of carbonate reservoirs

Wettability alteration has been identified as an important mechanism during low salinity water flooding in carbonate reservoirs. Oil composition, in particular, acidic and basic functional groups, plays an important role in regulating wettability. In this paper, we explored the potential of low salinity effect in reservoirs with high acidic components (acid number = 4.0 mg KOH/g and base number = 1.3 mg KOH/g) with a combination of approaches (e.g., contact angle and zeta potential measurements, and surface complexation modelling). We measured the contact angles of oil on calcite surfaces in presence of aqueous ionic solutions at different pH (3 and 8), salinity (0.01 and 1 mol/L), ion type (CaCl2 and Na2SO4) and temperatures (25–100 °C).Our results show that both salinity and ion type significantly affect contact angle at pH = 8. However, at low pH (pH 3), the oil-brine-calcite system becomes strongly water-wet with minor effect from salinity, ion type, and temperature. Lowing salinity drives the zeta potential of both oil-brine and brine-calcite to be strongly negative, particularly in the presence of Na2SO4 at pH 8, confirming the contribution of the electrical double layer to low salinity effect. Geochemical modelling reveals that breakage of electrostatic bridges between oil and calcite increases linearly with acid number, implying a higher potential of low salinity effect in high acidic oil-bearing carbonate reservoirs.This study provides an insight into how acid number parameter influences the wettability of oil-brine-carbonate system, and underscores the significance of acid components in wettability alteration of carbonate reservoirs, assisting in a better prediction and screening of low salinity EOR in carbonate reservoirs.