Predictive methods for density and refractive index of naphthenic lubricating oils during solvent extraction process

Lubricating oils are usually produced by solvent extraction to separate aromatics in order to achieve the desired specifications and better quality products.Among the different properties of lubricating oils,density and refractive index are some of the most important properties which can both be used for petroleum fluid characterization.Predictions of density and refractive index for naphthenic oils during solvent extraction by DMSO obtained by the pseudo-component approach and the quadratic correlation were both examined.The pseudo-component approach is a method to predict density and refractive index from composition while the latter merely relates density to refractive index.Results indicated that the predictions yielded by the pseudo-component method were in good agreement with experimental data for naphthenic oils.And the use of a function of refractive index(FRI_(20))as a pseudo-component property remarkably improved n_(20)predictions for the naphthenic mixtures.However,the density and refractive index predictions obtained by the quadratic correlation exhibited significantly higher de-viations for naphthenic oils than those for paraffinic oils.Thus a new modified correlation of the same functional form was proposed for naphthenic oils.The modification significantly improved predictions for naphthenic oils,which presented similar accuracy as the pseudo-component approach.And the previous correlation was still used for paraffinic oils.Additionally,effect of temperature on density and refractive index of naphthenic oils was examined.Results showed that the modified quadratic correlation was accurate for describing the relationship between density and refractive index of naphthenic oils at 20-90℃.The temperature dependence of density and refractive index for the raffinates and the extracts could be accurately described by the thermal coefficients for saturates and aromatics,respectively.Regarding the refractive index variation of the extracts with temperature,the empirical equation was proved to be a better option compared with the method using the thermal coefficient for aromatics.

Molecular composition of naphthenic acids in a Chinese heavy crude oil and their impacts on oil viscosity

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 high-resolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15–35 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.

Simulation of Solvent Extraction for Naphthenic Lubricating Base Oils

Solvent extraction is the process of separating aromatics from vacuum distillates for the production oflubricating base oils. In this study, the authors use dimethyl sulfoxide (DMSO) instead of furfural as solvent, in light of itshigher selectivity, to obtain extracts with a high aromatic content for naphthenic lubricating base oils. We systematicallyinvestigated effects of the solvent-to-oil (S/O) ratio and extraction temperature on the yield of the extract, efficiency ofaromatic removal, and composition of the extracts and raffinates. The results showed that the aromatic content of extractsfor naphthenic oils could reach a high value of about 80%. The solvent maintained a high selectivity for aromatics fornaphthenic oils even under a high S/O ratio and a high extraction temperature. Moreover, the efficiency of aromatic removalfor naphthenic lubricating base oils could be enhanced by increasing either the S/O ratio or the extraction temperature,although these measures had limited effects in practice. Following this, we used the non-random two-liquid (NRTL) modelbased on the pseudo-component approach to simulate the liquid-liquid equilibrium of the system of DMSO + naphtheniclubricating base oils, and determined the parameters of binary interaction through regression based on the data on phaseequilibrium. The modeling results showed that the predicted yield, content of the solvent, and composition of the raffinatesand extracts were in good agreement with those obtained in the experiments. This validates the reliability of the model usedto represent the DMSO + naphthenic lubricating base oil system. Both the experimental data and the method of simulationreported here can help optimize the extraction of naphthenic lubricating base oils, and provide a better understanding of thecorresponding process.

Study on Removal of Naphthenic Acids from White Oil by[BMIM]Br-AlCl_3

The removal of acid compounds （naphthenates） from acidic oil with ionic liquids was systematically investigated. [BMIM]Br-AlCl3 was used to investigate the effect on deacidification of oil. Experimental results showed that at a temperature of 323K with a molar ratio of AlCl3 to [BM1M]Br-AlCl3 of 0.2, and a mass ratio of IL to white oil of 4%, the deacidification rate could reach 75.9%. And a reaction time of 4 h was sufficient to achieve the goal. The study on reproducibility of catalytic performance of [BMIM]Br-AlCl3 showed the possibility of using the ionic liquid in the continuous catalytic reaction.

The Influence of Paraffinic Base Oil on Low-temperature Viscosity of Naphthenic Base Oil

Low-temperature viscosity of lube oils mixed with paraffinic base oil and naphthenic base oil at different mass ratios has been tested by experiments. The influence of paraffinic base oil on the performance of naphthenic base oil was investigated by studying the low-temperature viscosity of tested oils. The viscosity of lube oils increased with an increasing content of high-viscosity paraffinic base oil in the oil mixture. And the low-temperature viscosity was less influenced when the content of paraffinic base oil in the mixture was insignificant. In order to reduce the cost for formulating lubricating oil, a small fraction of paraffinic base oil can be added into naphthenic base oil as far as the property of lubricating oil can meet the specification. According to the study on low-temperature viscosity of the oil mixed with paraffinic base oil and naphthenic base oil, a basic rule was worked out for the preparation of qualified lubricating oils.

High-efficiency separation and extraction of naphthenic acid from high acid oils using imidazolium carbonate ionic liquids

N-alkyl imidazolium carbonate ionic liquids were employed to separate and recover naphthenic acid from model oils.The effects of the cationic and anionic structures of ionic liquids and operating conditions on the deacidification performance were investigated.The deacidification performance of traditional organic solvents was also investigated for comparison.The results indicated that the naphthenic acid could be completely removed from the model oil with a small mass ratio of ionic liquid to oil.The extracted naphthenic acid was regenerated with a recovery of up to 92%.In addition,imidazolium carbonate ionic liquids could be successfully regenerated and recycled.The mechanism of interaction between imidazole ionic liquids and the naphthenic acid molecules were explained by Gauss calculation.

Tracking Catalytic Esterification of Naphthenic Acids in Crude Oil by ESI FT-ICR MS

The catalytic esterification reaction was used to decrease total acid number(TAN) of crude oil by converting naphthenic acids to naphthenic acid esters in the presence of Zn-Al hydrotalcite used as the catalyst and glycol used as the reactant. The crude oil and its corresponding esterified oil were characterized by the negative-ion electrospray ionization(ESI) Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS). Six acidic class species, O_2, O_1, N_1, N_2, N_1O_1 and N_1O_2 were assigned in the negative-ion spectrum both in the crude oil and its esterified oil. Among the identified acidic compounds, the O2 class was dominant. The relative abundance of O_2 class species was much higher than other acidic class species in crude oil, while it was significantly decreased after esterification. The most abundant O_2 class species had a carbon number of 30-34 and a double-bond equivalence(DBE) value of 5 before and after esterification. It could be concluded that the naphthenic acids in crude oil can be esterified to lower its TAN value, and each of them seems to exhibit identical esterification efficiency approximately due to the similar DBE versus the-carbon number distribution before and after esterification.

Adsorption of Naphthenic Acids from Dewaxed Vacuum Gas Oil by Activated Clay: Kinetics, Equilibrium and Thermodynamic Studies

This work was mainly concentrated on the removal of naphthenic acids(NAs) from dewaxed vacuum gas oil(VGO) by adsorption using a commercial grade activated clay(AC) adsorption during lube base oil refining. The NAs in dewaxed VGO cut-4 were identified by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS). The AC sample from a refinery was characterized by XRD, BET, TG/DTA, and SEM. A series of experiments were carried out to investigate the performance of NAs adsorption by AC using a batch adsorption technique, in which some key experimental parameters such as temperature, contact time, initial concentration of NA in oil sample as well as the dosage of adsorbent were investigated. Equilibrium isotherms were analyzed using the Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich(D-R) adsorption models. The pseudo-first order, the pseudo-second order, and intraparticle diffusion models were employed to describe the kinetics data. The results revealed that the D-R isotherm provided a better fit to the experimental data than other isotherms, and the adsorption kinetics followed the pseudo-first order kinetic equation. The thermodynamic data indicated that the adsorption process was feasible and spontaneous as an endothermic process. The results could provide a clear understanding of the NAs adsorption by AC during lube base oil processing at refineries.

Study on Separating Naphthenic Acids from Diesel Fuel by Microwave Irradiation

The microwave technology was introduced to separate naphthenic acids from diesel fuel. Thedecrease of zeta-potential of electric double layer on the W/O interface and the reduction of diesel fuelviscosity were responsible for the accelerated separation of naphthenic acids under microwave irradiation.The influences of dosage of alkali compound solvent (Mp/MT), irradiation pressure, irradiation time,irradiation power, the settling time and oil phase-to-solvent phase volume ratio (O/S) had been investigated.The optimum process conditions for the refining process were determined. The removal of naphthenicacids reached 98.4% when the optimum conditions were proposed as follows: Mp/MT=1.5, 0.05MPa, 6 min,375W, 25min and O/S=10, respectively. The diesel recovery could reach 99.3% and the quality of thetreated diesel oil was good enough to meet the specification of GB252-2000.

Molecular Simulation of Naphthenic Acid Removal on Acidic Catalyst(I) Mechanism of Catalytic Decarboxylation

In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simulation results showed that the bond order of C—O was higher than that of C—C, and C—C bond connected to the carbon atom in the carboxyl radical had the lowest bond order. The charge distributions of model naphthenic acids were similar in characteristics that the negative charges were concentrated on carboxyls. According to the simulation results, the mechanisms of catalytic decar- boxylation over acidic solid catalyst were proposed, and a new route was put forward regarding removal of the naphthenic acid from crude oil through catalytic decarboxylation.

A New Method for Determination of Naphthenic Acids in Crude Oil

The petroleum acids in crude oil were separated by extraction with column chromatogram and anion exchange resin. The separation effect and the related composition and structure of petroleum acids were obtained by using IR (Infra-Red) spectra techniques. The separated petroleum acids can under special conditions react with methanol to form corresponding esters, which can be analyzed by CI (chemical ionization)-MS (mass spectrometry). The characteristic ion peaks m/z (M+15)+ of naphthenic acid esters combined with z-series formula CnH2n+zO2 of naphthenic acids can be used to classify naphthenic acids into fatty acids, mono-cyclic, bi-cyclic, tri-cyclic, and higher polycyclic acids. The analytical results can give the molecular weight and the carbon number distribution of petroleum acids contained in crude oil. The results of study indicate that this method is simple, rapid and easy in operation.

Molecular Simulation of Naphthenic Acid Removal on Acidic Catalyst II. Experimental results of catalytic decarboxylation over acidic catalysts

The energy barriers of thermal decarboxylation reactions of petroleum acids and catalytic decarboxylation reactions of Bronsted acid and Lewis acid were analyzed using molecular simulation technology. Compared with thermal decarboxylation reactions of petroleum acids, the decarboxylation reactions by acid catalysts were easier to occur. The decarboxylaton effect by Lewis acid was better than Bronsted acid. The mechanisms of catalytic decarboxylation over acid catalyst were also verified by experiments on a fixed bed and a fluidized bed, the experimental results showed that the rate of acid removal could reach up to 97% over the acidic catalyst at a temperature above 400℃.

UV Photocatalytic Degradation of Commercial Naphthenic Acid Using TiO₂-Zeolite Composites

The presence of naphthenic acids in oil sand products and process streams is the cause of toxicity to aquatic life and corrosion. The removal of organic acids from tailings pond water reduces the negative impact on marine life. The ultra-violet (UV) photocatalytic reduction of commercial naphthenic acid in water using TiO2-zeolitecomposites showed a significant decrease in the concentration of naphthenic acid, accompanied by an increase in carbon dioxide formation;the presence of carbon dioxide signifies degradation of the naphthenic acids. Mixtures of the acid and photocatalyst kept in the dark did not show any concentration changes. The extent of naphthenic acid reduction by UV light was verified by the reduction in total acidity. The total acidity values of mixtures of the acid and TiO2-zeoliteexposed to UV decreased by 31% compared to mixtures kept in the dark. A reduction in total acidity may lead to a decrease in the toxicity of naphthenic acid contaminated water.

Photocatalysis of Naphthenic Acids in Water

Naphthenic acids (NAs) are soluble in water and are concentrated in oil sand process water (OSPW) as a result of caustic oil sands extraction processes. Significant environmental and regulatory attention has been focused on the naphthenic acids. A laboratory scale photocatalysis system was developed using UV254 florescent lamps. Experiments were conducted to determine the NA degradation efficiency of this system in presence of TiO2 catalyst. Degradation kinetics for total NAs as well as individual z-families was calculated. The developed treatment system was able to degrade OSPW NAs with half life values ranging between 1.55 and 4.80 h. This system also completely reduced the acute toxicity associated with NAs (up to 5 min. IC50 v/v > 90%) based on Microtox assays.

Processing and Utilization of Naphthenic Base Heavy Crude Oil(continued)

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Improving Winter Traction and Fuel Economy of Car Tires Using Naphthenic Tire Oils

Naphthenic tire oils were used in winter tire tread compounding. Properties of compounds were compared with similar compounds made of other safe tire oils. Retreaded passenger car winter tires were prepared using the compounds. Traction and rolling resistance of the tires were determined in different weather conditions.It was shown that naphthenie oils may lead to improvement of winter traction and rolling resistance without compromising other tire properties.

Processing and Utilization of Naphthenic Base Heavy Crude Oil

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Effects of the chemical structure of surfactants on the stability of naphthenic oil-based metalworking fluids

In this study,various nonionic surfactants(NS) with different ethylene oxide(EO) numbers and tail lengths and its binary blends with anionic surfactants(AS) were used as emulsifiers for naphthenic oil to form the microemulsion metalworking fluids(MWFs),and the effects of them on the stability of the emulsion system were investigated by formulation triangle method.The results indicated that binary complex surfactants of NS and AS as emulsifiers exhibited better emulsifying effect than that of single NS.NS with different EO numbers and tail lengths presented various emulsifying effects.NS(EO=10)exhibited the greatest number of stable formulations,especially the TX-10,but no linear relationship existed between the number of stable formulations and the tail length of NS.In addition,aromatic primary alcohol ethoxy late(APAE) series surfactants containing benzene groups similar to the cycloalkanes in the naphthenic oil so that presented the best emulsifying affect and the greatest number of stable formulations.The co-surfactant of sodium dodecyl benzene sulfonate(SDBS) binary blends with NS exerted the best synergistic effect,and the stable formulations numbers were ranged from 5 to 7,next sodium stearate(SS) comes last followed by sodium dodecyl sulfate(SDS-1) and sodium dodecyl sulfonate(SDS-2).

Standard method design considerations for semi-quantification of total naphthenic acids in oil sands process affected water by mass spectrometry： A review

Naphthenic acids are a complex class of thousands of naturally occurring aliphatic and alicyclic carboxylic acids found in oil sands bitumen and in the wastewater generated from bitumen processing. Dozens of analytical methods have been developed for the semiquantification of total naphthenic acids in water samples. However, different methods can give different results, prompting investigation into the comparability of the many methods. A review of important methodological features for analyzing total naphthenic acids is presented and informs the design of future standard methods for the semi- quantification of total naphthenic acids using mass spectrometry. The design considerations presented are a synthesis of discussions from an Environment and Climate Change Canada （ECCC） led taskforce of 10 laboratory experts from government, industry and academia during April 2016 and subsequent discussions between University of British Columbia and ECCC representatives. Matters considered are： extraction method, solvent, pH, and temperature; analysis instrumentation and resolution; choice of calibration standards; use of surrogate and internal standards; and use of online or offline separation prior to analysis. The design considerations are amenable to both time-of-flight and Orbitrap mass spectrometers.

Potential of capillary electrophoresis mass spectrometry for the characterization and monitoring of amine-derivatized naphthenic acids from oil sands process-affected water

Capillary electrophoresis coupled to mass spectrometry（CE–MS） was used for the analysis of naphthenic acid fraction compounds（NAFCs） of oil sands process-affected water（OSPW）. A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15 min. Time of flight MS analysis（TOFMS）, optimized for high molecular weight ions, showed NAFCs between 250 and 800 m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs（between 100 and 450 m/z） are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）, or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30%（V/V） methanol in water and 2%（V/V） formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z.