Simultaneous removal of asphaltenes and water from water-in-bitumen emulsion: I. Fundamental development

Simultaneous removal of asphaltenes and water from a water-in-bitumen emulsion by adding light paraffinic solvents was investigated with a bench-scale unit. Asphaltene precipitation in bitumen, emulsion breaking, and phase separation were found to be largely dependent on solvency and temperature. Increasing temperature facilitated the precipitation of asphaltenes in bitumen, and accelerated the separation of the light deasphalting oil (DAO)/solvent phase and the heavy asphaltenes/water phase. The removal of 98 +% asphaltenes and 99.9 +% water from the emulsion was achieved with the n-pentane/bitumen volumetric ratio of 3.0 in temperature range of 423–453 K. The interaction between asphaltene particles and water droplets is actually beneficial to the removal process. For process design and optimization, the operation pathway including two-step solvent injections at different temperature, the supercritical recovery of solvent from DAO stream and the solidification of asphaltenes by depressurization, as well as other important issues have been addressed.     

Diffusion of asphaltene molecules through the pore structure of hydroconversion catalysts

When hydrotreatment of heavy cuts by heterogeneous catalysis is carried out in liquid phase, the molecules’ state of containment in the porous network is very high. Moreover, at that state of containment, the size of asphaltenes and resins, from various origins, can be the cause for the different hydrotreatment yields. Consequently, volume constraints are added to the kinetic and thermodynamic ones (adsorption equilibrium): a given species can penetrate in the solid only if the necessary volume is available within the network.Hindered diffusion and adsorption of asphaltene molecules inside hydrotreatment catalysts’ carriers were studied. The system's kinetics was investigated by visible absorption spectroscopy. Asphaltenes were prepared by n-heptane separation and solubilized in toluene at a known concentration and put in contact with a given amount of catalyst support. The evolution of the concentration in the asphaltene's solution was followed, as a function of time, by measuring the absorbance of a monochromatic visible radiation (750 nm) through the asphaltene suspension.A model based on the “Stefan–Maxwell” equations, that takes into account the volume constraints by the Fornasiero's formulation, which supposes that the molecules collide only by equivalent volume, was developed. The parameters estimation has been performed and discussed. The results show that the diffusional limitations are important in the catalyst used for heavy oil hydrotreatment and the asphaltene adsorption is very strong in this type of material.     

Modeling of asphaltene and water associations in petroleum reservoir fluids using cubic‐plus‐association EOS

Asphaltene is a group of complex compounds commonly present in petroleum reservoir fluids. It is conceivable that asphaltenes strongly interact with water through hydrogen bonding, affecting phase behavior of water/oil mixtures with/without forming an asphaltene‐rich phase. In this research, the cubic‐plus‐association equation of state (CPA EOS) is applied to multiphase behavior resulting from self‐ and cross‐associations of asphaltenes and water in petroleum fluids. This article also presents a new correlation for binary interaction parameters for water with n‐alkanes for the CPA EOS by using three‐phase data for water/n‐alkane binaries. A method is proposed to characterize mixtures of asphaltene‐containing oil with water using the CPA EOS. Results show that the CPA EOS can represent multiphase behavior for water/oil mixtures with up to four equilibrium phases: asphaltene‐rich, solvent‐rich, aqueous, and vapor phases. Case studies include bitumen/water mixtures, involving asphaltene‐water emulsion, water solution in bitumen, and their continuous transition with varying temperature. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3429–3442, 2018     

Evaluation of nanoemulsions based on silicone polyethers for demulsification of asphaltene model emulsions

Asphaltenes are considered the main agents responsible for stabilizing petroleum emulsions. However, due to the complex chemical nature of crude oil, it is necessary to extract these molecules and prepare model solutions to investigate the effects of the various asphaltenes separately. In this study, the demulsification efficiency of oil‐in‐water (O/W) nanoemulsions based on silicone polyethers was evaluated using asphaltene model emulsions. The interfacial properties of the model emulsions were evaluated, with and without the presence of the nanoemulsions, by interfacial tension and inerfacial rheology measurements and correlating them with the ability and/or speed of diffusion to the interface. Dispersion/flocculation tests of the asphaltenes were performed to assess whether the nanoemulsions were modifying the aggregation state of the asphaltenes during the process of destabilizing the model emulsions. Through the interfacial rheology tests of the model asphaltene/saltwater system, with or without addition of the systems used in the demulsification tests, it was possible to determine the influence of the nanoemulsions on the mechanical properties of the interfacial film. The results of the water/oil gravitational separation tests showed that the nanoemulsions had separation efficiency between 80 and 95%, depending on the composition of the water/surfactant/oil/asphaltene system. The nanoemulsions containing xylene as the oil phase destabilized the emulsions the fastest. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44174.     

Simultaneous removal of asphaltenes and water from water-in-bitumen emulsion: II. Application feasibility

Application feasibility of the accelerated deasphaltening process for simultaneous removal of asphaltenes and water from a water-in-bitumen emulsion has been examined with a pilot plant having capacity of 1.590 m3/day. The solvent (n-pentane) was injected into the emulsion from three locations with progressively increasing temperature from 423 K. The first solvent injection precipitated the asphaltenes in bitumen, the second broke the emulsion and facilitated the phase separation, and the third extracted the oil that remained in heavy asphaltenes/water phase. The effects of operation parameters such as temperature, solvent/bitumen ratio, feed rate and feedstock composition on the quality of DAO (Deasphaltening oil) were investigated. The DAO with the yield of ~ 80 wt.% and asphaltene content of < 0.5 wt.% was produced under optimal operating conditions, and the residual product was a porous solids containing 38% sulfur, 47% nitrogen, 64% MCR, and 85% metals (nickel and vanadium) of the bitumen. For a real application in oil industry, other important aspects including energy efficiency, solvent recovery and water purification have been discussed.     

石油磺酸盐对原油界面性质及其乳状液稳定性的影响

The influence of petroleum sulphonate （TRS） on interfacial properties and stability of the emulsions formed by formation water and asphaltene, resin and crude model oils from Gudong crude oil was investigated by measurement of interfacial shear viscosity, interfacial tension （IFT） and emulsion stability. With increasing petroleum sulphonate concentration, IFT between the formation water and the asphaltene, resin and crude model oils decreases significantly. The interfacial shear viscosity and emulsion stability of asphaltene and crude model oil system increase for the petroleum sulphonate concentration in the range 0.1% to 0.3%, and decrease slightly when the concentration of the surfactant is 0.5%. There exists a close correlation between the interfacial shear viscosity and the stability of the emulsions formed by asphaltene or crude model oils and petroleum sulphonate solution. The stability of the emulsions is determined by the strength of the interfacial film formed of petroleum sulphonate molecules and the natural interfacial active components in the asphaltene fraction and the crude oil. The asphaltene in the crude oil plays a major role in determining the interfacial properties and the stability of the emulsions.     

Kinetics of asphaltenes conversion during hydrotreating of Maya crude

The kinetics of asphaltene conversion was studied during the hydrotreating of Maya heavy crude oil. Experimental tests were conducted in a pilot plant at the following reaction conditions: total pressure of 70–100 kg/cm², liquid hourly space-velocity (LHSV) of 0.33–1.5 h⁻¹, and reaction temperature of 380–420 °C at a constant hydrogen-to-oil ratio of 5000 ft³/bbl. A commercial NiMo/Al₂O₃ catalyst was used in all experiments. Asphaltenes were precipitated from Maya crude and from hydrotreated products in a Parr Batch Reactor at 25 kg/cm² and 60 °C with n-heptane as solvent. Asphaltene hydrocracking data were used to estimate reaction orders and activation energy using a power-law model, and the average absolute error between experimental and calculated concentrations of asphaltenes was found to be less than 5%.     

NMR study of temperature-induced phase separation and polymer-solvent interactions in poly(vinyl methyl ether)/D2O/ethanol solutions

The changes in the dynamic structure during temperature-induced phase transition in D₂O/ethanol solutions of poly(vinyl methyl ether) (PVME) were studied using NMR methods. The effect of polymer concentration and ethanol (EtOH) content in D₂O/EtOH mixtures on the appearance and extent of the phase separation was determined. Measurements of ¹H and ¹³C spin-spin and spin-lattice relaxations showed the presence of two kinds of EtOH molecules: besides the free EtOH expelled from the PVME mesoglobules there are also EtOH molecules bound in PVME mesoglobules. The existence of two different types of EtOH molecules at temperatures above the phase transition was in solutions with polymer concentration 20 wt% manifested by two well-resolved NMR signals (corresponding to free and bound EtOH) in ¹³C and ¹H NMR spectra. With time the originally bound EtOH is slowly released from globular-like structures. From the point of view of polymer-solvent interactions in the phase-separated PVME solutions both EtOH and water (HDO) molecules show a similar behaviour so indicating that the decisive factor in this behaviour is a polar character of these molecules and hydrogen bonding.     

Effect of hydrate formation/dissociation on emulsion stability using DSC and visual techniques

A key factor in hydrate risk management for an oil-dominated system is the stability of the emulsified water with gas hydrate formation. We show via differential scanning calorimetry (DSC) that gas hydrate formation and dissociation has a destabilizing effect on water-in-oil (W/O) emulsions, and can lead to a free water phase through agglomeration and coalescence of dissociated hydrate particles. High asphaltene content crude oils are shown to resist hydrate destabilization of the emulsion. Span80 was successfully used as an analog to asphaltene surface activity. Based on our experimental results, a new conceptual hydrate-induced destabilization model is proposed.     

沥青质和胶质对辽河稠油乳状液破乳的影响

针对辽河曙光稠油乳状液粘度大、破乳难、破乳温度高等问题,以曙光稠油为研究对象,从中分离出沥青质和胶质,用傅里叶变换红外光谱法分析其主要官能团,考察沥青质和胶质对稠油乳状液粘度及破乳效果的影响。测定了不同含量胶质、沥青质对稠油油／水界面张力的影响。结果证实,沥青质比胶质含有羟基多,分子间氢键作用强烈,更容易造成原油粘稠。随着叫（胶质）、训（沥青质）升高,稠油乳状液脱水率降低,w（沥青质）超过2．1％,或w（胶质）超过32％时,稠油乳状液的破乳十分困难。w（胶质）、w（沥青质）的增高会使破乳剂水溶液与原油的界面张力增大,w（沥青质）增加0．7％比叫（胶质）增加7％原油的界面张力升高还要大,所以训（沥青质）的增加对油水界面张力影响更大。     

Effect of Ascorbic Acid or Acyl Ascorbate on the Stability of Catechin in Oil-In-Water Emulsion

The degradation of (+)-catechin in an oil-in-water emulsion using methyl dodecanate as an oil phase with or without ascorbic acid or acyl ascorbate was kinetically examined at 40 °C. The rate constant, k, of the first-order kinetics for the degradation with ascorbic acid or octanoyl ascorbate depended on the added amount, whereas the k value with hexadecanoyl ascorbate was independent of the amount. The k value for a smaller oil droplet with each ascorbate was lower than that for a larger oil droplet. Catechin did not partition well into the methyl dodecanate phase, but did adsorb slightly onto the interface between the methyl dodecanate and water. The suppressive effect of acyl ascorbate on the catechin degradation in the emulsion was lower than that of hydrophilic ascorbic acid at the low concentration, but the peroxidative ability also was lower. Most of the catechin molecules in the emulsion degraded in the water phase. The catechin degradation in the emulsion with small oil droplets depended on the acyl chain length of the ascorbates more than in large oil droplets.     

Functions of Demulsifiers in the Petroleum Industry

There are an increasing number of crude oil fields that are now producing both crude oil and water emulsions; such fields are both onshore and offshore. These emulsions are formed during oil exploitation due to the presence of natural surfactants, such as asphaltenes and resins. These molecules strongly stabilize the water/oil interface and prevent coalescence of water droplets. As water/oil phase separation is necessary before oil transportation and refining, demulsifiers are used to break water-in-oil emulsions. This review presents the crude oil emulsion formation, factors affecting demulsification of crude oil emulsion such as demulsifier chemical structure, water content, partition coefficient (K_P), and demulsifier concentration. This review also covers the kinetics and mechanism of the demulsification process.     

Application and development of synthetic polymer membranes. VI. Pervaporation of aqueous ethanol solution through quaternized poly[3-(N′,N′-dimethyl) aminopropylacrylamide-co-acrylonitrile] membranes

Membranes obtained from polymers, quaternized poly[3-(N′,N′-dimethyl) aminopropylacrylamide-co-acrylonitrile]s, showed selective separation of water from aqueous ethanol solution by pervaporation. The separation factor toward water reached over 15,000. Membrane performance showed a good correlation to membrane polarity. Differential scanning calorimetric melting endotherms of the water-swollen membranes were studied to clarify the state of water in the membranes. The results suggested that there are two states of water in the membrane: bound and free. The higher the fraction of bound water in the membrane, clearly, the more preferentially was water permeated.     

Characterising high mass materials in heavy oil fractions by size exclusion chromatography and MALDI-mass spectrometry

Several petroleum vacuum residues and a Maya asphaltene have been examined using size exclusion chromatography (SEC), using 1-methyl-2-pyrrolidinone as eluent. Aliphatic components are not dissolved in this solvent. All the samples showed a bimodal distribution. Material under the early eluting peak, excluded from column porosity corresponded to apparently very large molecular masses. The later eluting peak corresponded to molecules with a smaller range of masses and was relatively intense. The material excluded from column porosity is concentrated in the heptane-insoluble fraction; the peak of this fraction corresponding to smaller molecules shifted to earlier times than was found for the whole sample. In UV-fluorescence spectrometry, the heptane-insoluble materials did not fluoresce strongly. Materials excluded from column porosity showed no fluorescence, indicating that UV-fluorescence based methods are unable to detect high mass materials. MALDI-mass spectrometry indicated a bimodal distribution for the Maya asphaltene with a mass range up to m/z 40,000. Comparison of the low mass range of the spectrum with the small-size molecules detected by SEC indicated broad agreement for masses up to about 5000 u. However, if the excluded peak of SEC corresponds to the higher mass range up to m/z 40,000, then it is likely that these molecules are adopting three-dimensional conformations. Data from the hydrocracking of heavy oils was used to confirm some of the outlined findings.     

油水乳液分离沼气实验研究

研究了柴油-水乳液体系在水合物生成条件下对沼气（CO₂/CH₄）中CO₂的捕集能力。阻聚剂Span20被加入到乳液中以分散水滴和水合物颗粒。综合考虑了温度、原料气组成、压力和乳液含水率对柴油-水乳液体系分离能力的影响。从实验结果可以看出,吸收-水合耦合分离效果明显优于单独的吸收分离,且分离平衡后,浆液中水合物分散均匀,流动性良好。乳液体系分离能力在一定范围内随着温度降低和含水率的增加而增强。综合考虑乳液分离能力和流动特性表明,温度270.15～272.15 K,体系含水率 20%～25%（vol）和初始推动力为3.2 MPa左右时为最合适的分离条件,在对应条件下经过两级模拟分离,气相中CO₂浓度能从31%（mol）降到近10%（mol）,超过87%（mol）的CO₂被水合物浆液捕集。     

The Stability of Water‐in‐Crude and Model Oil Emulsions

The critical electric field (cef) technique has been utilized to measure the stabilities of a variety of water‐in‐model oil and petroleum emulsions. The cef method allows for a fast, reproducible, and quantitative gauge of emulsion stability. Here, we have used cef to measure the stability of water‐in‐heptane‐toluene‐asphaltene emulsions and confirmed the importance of solvation of asphaltenes and the state of asphaltene aggregation to emulsion stability. Emulsion stability increased with the concentration of soluble asphaltenes near the point of precipitation. Droplet sizes were measured with optical microscopy in order to calculate interfacial areas and film thicknesses. It was found that film thickness increased with asphaltene concentration up to the solubility limit, above which increased concentration had little effect, and cef increased with interfacial film thickness up to a monolayer coverage of asphaltene aggregates, above which film thickness had a much smaller effect. These findings were applied to a cef investigation of water‐in‐ppetroleum emulsions to develop correlations of the stability of water‐in‐ccrude oil emulsions. A strong correlation (coefficient = 0.95) was found for cef with the product of asphaltene concentration and the difference in hydrogen to carbon atomic ratios of the asphaltenes and petroleum solvent. The development of a kinetic model and its fit to experimental data revealed the effects of asphaltene chemistry, solvency, and resin concentration on the adsorption and consolidation of emulsion stabilizing interfacial films.     

胜利孤岛注聚原油破乳剂的筛选与性能评价

以研究孤岛注聚原油乳状液破乳为目的,通过瓶试法和界面性质的测定,筛选了多种类型的原油破乳剂,考察了破乳剂质量浓度、聚合物和原油组分对破乳效果的影响,探讨了原油乳状液的破乳机理。结果表明,破乳剂BF-069质量浓度在100mg/L,50℃条件下,脱水率达到70%以上,现场温度稍微升高,脱水率达到85%左右,破乳剂BF-069已在胜利油田应用,现场使用效果良好;聚合物质量浓度在50mg/L时,原油乳状液最难破乳;原油中不同组分对破乳效果的影响不同,油水界面性质的测定表明,胶质和沥青质是影响原油破乳的主要因素。     

Surfactant-enhanced free radical polymerization of styrene in emulsion gels

The presence of a surfactant (such as hexadecyltrimethylammonium bromide, CTAB) enhanced the rate of polymerization of styrene in emulsion gels with and without silica. The emulsion gels consisted of styrene, azobisisobutyronitrile (AIBN), surfactant, water, and, in some cases, fumed silica. Polymerization of the emulsions was carried out at room temperature in one or several days depending on the composition of the emulsion. The conversion of monomer to polymer could exceed 90% in a couple of days. In contrast, very little polymerization occurred in the absence of surfactant. A simple model, incorporating a surfactant-initiator complex and standard free radical polymerization, successfully fits the experimental kinetics data. This analysis suggests that the initiator is complexed with approximately three surfactant molecules.     

Polymer latex containing carboxylic acid functional groups. I. Synthesis of polymer latex from MMA and AA

The polymer latex of poly(MMA‐AA) was synthesized using two techniques: soapless seeded emulsion polymerization, and the soapless emulsion copolymerization technique. The reaction kinetics, morphology, composition, and size of latex particles, as well as the structure using thin‐layer chromatographic separation techniques, glass transition temperature (T_g), and molecular weight of polymer products, were studied under different experimental conditions. The reaction of the hydrophilic AA monomer took place in two places—on or in the latex particles, and in the water phase. Therefore, the polymer latex, whose size is very small and uniform, dispersed uniformly all over the PAA continuous phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3111–3120, 1999     

H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

¹H NMR spectroscopy was used to investigate thermotropic phase transitions in D₂O solutions of poly(N-isopropylmethacrylamide) (PIPMAm)/poly(vinyl methyl ether) (PVME) mixtures. In all studied solutions (polymer concentrations c=0.1-10 wt%) two phase transitions were detected at temperatures roughly corresponding to different lower critical solution temperatures of PIPMAm and PVME. While the phase transition of PVME component (located at lower temperatures) is not affected by the presence of PIPMAm in the mixture, the phase transition temperatures of PIPMAm component (located at higher temperatures) are affected by the phase separation of the PVME component. Measurements of ¹H spin-spin relaxation of residual water (HDO) molecules revealed that above the phase transition, a certain portion of water molecules is bound to polymer globular structures. A major part of bound water is present in globular structures of predominating polymer component in the mixture.