Wax Dissolution Research Articles

Compatibility analysis between natural rubber/polybutadiene rubber and protective waxes based on experiments and materials studio simulations

AbstractProtective waxes are typically mixtures of paraffin and microcrystalline waxes that retard the aging of unsaturated rubbers and are widely used in rubber products. The wax solubility of rubber products is important for understanding the migration behavior and film formation of waxes and determining the appropriate wax content in rubber compounds. In this article, protective waxes were applied to natural rubber (NR)/polybutadiene rubber (BR) based sidewall rubber and the compatibility between NR and BR and the protective wax dissolution in these rubbers were investigated with a focus on the former investigation through Materials Studio simulations. It was found that the simulation results are strongly correlated with the wax migration test results on compounded and cured rubber at different NR/BR mass ratios. Blends and mesoscopic dynamics simulations yielded good compatibility between NR and BR and favorable blend morphology. By analyzing the solubility parameter, R value, mean square displacement and diffusion coefficient of wax chains with different lengths in the NR/BR matrix, the mechanism and reasons for the wax precipitation variation of protective waxes at varying NR/BR mass ratios were analyzed from a microstructural point of view, which provides strong theoretical support for the design of the molecular structure of protective waxes.

Evaluation of Crude Oil Wax Dissolution Using a Hydrocarbon-Based Solvent in the Presence of Ionic Liquid

The current alternative of using aromatic-based wax soak solvents has been found to be hazardous and imposes a high cost on field expenditures. These solvents are widely used in the oil and gas industry to soften up wax before the pigging process. However, their impacts on the environment are quite concerning. Plus, they also impose hazardous exposure and are found to be damaging to both plastic and rubber hoses. To replace the current alternative with other hydrocarbon-based wax soak solvents, ionic liquids were found to have the capability to increase the solvent power capabilities and the efficiency of wax soak solvent in dissolving heavy crude oil. To optimise the application of hydrocarbon solvents and ionic liquid in wax dissolution, the affinity of ionic liquids in three solvents was studied. The solvents were condensate, ethyl acetate, and xylene. It was found that from four types of ionic liquids tested, only BMIMCL and HMIMBr were miscible in all three of the solvents used. Dissolution of hard deposited paraffin wax in condensate, ethyl acetate and xylene was conducted using the spectral analysis method, and it was found that the dissolution of paraffin wax was greatest in ethyl acetate. However, enchantment on wax dissolution was also observed for gas condensate and xylene. The wax soaking time was also optimised, in which the dissolution of wax was found to reach a saturation level when the wax had been soaked for over 90 min in the solvents, especially for gas condensate. Further study on the effect of ionic liquid introduced alongside condensate, ethyl acetate and xylene, aiming to enhance the solvent power, was also conducted using the spectral analysis method. The introduction of ionic liquids to all hydrocarbon-based wax soak solvents used in this project was proven to significantly increase the UV-VIS absorbance of the extracted solvents after paraffin wax had been soaked for 30 min.

Sustainable and cleaner approach for paraffin wax treatment via CO2-induced polarity transformation of switchable solvents

Paraffin wax has caused obvious detrimental consequences to the extraction for fossil fuels, and posed environmental challenge due to the absence of cleaner methods for paraffin wax removal. A cleaner and sustainable approach for paraffin wax removal was developed using the switchable polarity solvents (SPS). Three SPS with low polarity, including dipropylamine (DPA), ethylbutylamine (EBA), and dibutylamine (DNBA) were selected for paraffin wax removal. Compared with bubbling CO2 into SPS straightway, the transformation of the polarity quantified by normalized polarity energy confirms the addition of water is benefit to enlarge the polarity scope. Paraffin wax is removed at the initial state and separated at the final state by CO2-induced polarity transformation of SPS. The dissolution rates for paraffin wax of DPA and EBA reached 0.071 g/min and 0.062 g/min, which surpassed that of traditional solvents, such as o-xylene (0.045 g/min) and Petroleum ether (0.017 g/min), indicating that these selected SPS is suitable for paraffin wax removal. The paraffin wax dissolution behaviors of SPS can be accurately matched using modified Apelblat models with root-mean-square deviation of 1.085%. With the addition of water, more than 99% of paraffin wax is separated from DPA and EBA by introducing CO2 within 10mins, which is a better alternative method for energy-intensive distillation process. The introduction of water is indispensable for improving the separation efficiency, since it enlarged the polarity difference between solvents and paraffin wax. The thermal behavior of separated paraffin wax detected by Differential Scanning Calorimetry remained steady, and there were negligible residual solvents detected indicate the feasible separation of paraffin wax. Both SPS and water are recovered upon N2/80 °C, which retain good recyclability for paraffin wax removal. These findings confirms the applicability of SPS in the sustainable and cleaner removal of paraffin wax. The use of SPS provides an alternative and promising approach for paraffin wax removal for ensuring the demands of low-energy consumption and environment.

Dissolution of a spherical particle with a moving boundary in a flow field

Particle dissolution is an important process that occurs during heat treatment in the transportation process. We present a one-dimensional model of spherical wax particle dissolution in a fluid. The model includes a nonlinear equation at the free boundary, which was established to describe the dissolution rate of a wax particle assuming a diffusion process. At the moving boundary, we compute the concentration distributions of partial solutions. To estimate wax dissolution in solution and related expressions for the dissolved radius, an analytical solution of a mathematical model for spherical particle dissolution in flow is used.

Contrasting impacts of mixed nonionic surfactant micelles on plant growth in the delivery of fungicide and herbicide

HypothesisNonionic alkyl ethoxylate surfactants are widely used in agrochemicals to facilitate the permeation of systemic herbicides and fungicides across the plant waxy film. Industrial grade surfactants are often highly mixed and how the mixing affects their interactions with pesticides and wax films remains largely unexplored. A better understanding could enable design of mixed nonionic surfactants for herbicides and fungicides to maximize their efficiency and reduce wastage whilst controlling their impact on plant wax films. ExperimentIn this study, nonionic surfactants with general structure n-oxyethylene glycol monododecyl ether (C12En) were used to form surfactant mixtures with the same average ethoxylate numbers but different hydrophilic-lipophilic balance (HLB) values. Their mixed micellar systems were then used to solubilize a herbicide diuron (DN) and a fungicide cyprodinil (CP), followed by plant wax solubilization upon contact with wax films. These processes were monitored by 1H NMR and SANS. FindingPesticide solubilization made surfactant micelles effectively more hydrophobic but subsequent wax dissolution caused pesticide release and the restoration of the micellar amphiphilicity. Nonionic surfactants with lower HLBs form larger nanoaggregates, show enhanced wettability, and have better ability to solubilize and permeate pesticides across the wax film, but may cause significant damage to plant growth. These observations help explain why herbicides applied on weeds would benefit from surfactants with lower HLB values while fungicides require surfactants with HLBs to balance between delivery efficiency and potential phytotoxicity risks.

Impacts of shear and thermal histories on the stability of waxy crude oil flowability improvement by electric treatments

Recent studies have shown that the poor flowability of waxy crude oil can be obviously improved by the application of an external electric field. Available studies about this novel technique to treat waxy oils focus on the efficacy of this technique while the sustainability of the efficacy is not well understood. In this work, the impacts of shearing and thermal cycling on the stability of the electric treatment efficacy were investigated. A representative waxy crude treated by electric field was subjected to shearing at different conditions and reheating to an elevated temperature and cooling, then the viscosity and the yield stress were inspected and wax particle microscopic images were observed to examine the impacts of shear and thermal histories on the sustainability of waxy crude oil flowability improvement by electric treatment. The experimental results show that the electric treatment efficacy of waxy crude oil gradually diminishes after the removal of electric field. However, shearing at a high shear rate and for a prolonged duration partially preserves the efficacy of the electric treatment and intensively shearing the electric treated oil provides some additional flowability improvement. The flowability improvement by electric treatment is weakened by reheating the treated oil to an elevated temperature. When the treated oil is heated above the wax dissolution temperature, the efficacy of the electric treatment is eventually eliminated. The results presented in this work further the understanding of the flowability improvement of waxy crudes by electric treatment.

Development of a SGJ-1 of Water-Based Anti-Wax Agent

The phenomenon of petroleum wax deposition is very common during oil well production. When the wax molecule condenses on the surface of the pipeline, it will hinder the exploitation of crude oil, reduce the recovery rate of crude oil, and may lead to the blockage of the pipeline when it is serious, so that the oil recovery work will stop. This phenomenon can be obviously changed by using wax cleaning agent. However, the low ignition point and toxicity of oil-based wax remover are not conducive to oil recovery. Therefore, a new water-based paraffin remover SGJ-1 was developed in this paper. The best formula is: wax dispersant 15%, wetting reversion agent 1%, sodium silicate 1%, alcohol cosolvent 8% and 75% water. Condensation point, wax dissolution rate and anti-wax performance of SGJ-1 water-based dewaxing and anti-waxing agent were tested by self-assembly testing device. The experimental results show that the condensation point of SGJ-1 is -34°C, the viscosity reduction effect is good under 35°C, and the wax dissolution rate is 0.0512 g/min, The highest wax prevention rate can reach 89.58% and the wax removal and wax prevention ability is excellent. Compared with other paraffin removers, SGJ-1 can also reduce the viscosity of crude oil, so it has a good development prospect.

Preparation of Janus Titanium Dioxide Particles via Ultraviolet Irradiation of Pickering Emulsions

AbstractPickering emulsions are stabilized by solid particles assembled at an immiscible liquid–liquid interface. In this work, the use of such emulsions to prepare semiconductor Janus particles through UV‐irradiation is explored. Titanium dioxide particles that are prefunctionalized with an alkylsilane or a fluoroalkylsilane are employed to obtain wax‐in‐water emulsion droplets, which consist of the particles partially embedded in the wax core. Different emulsion formation mechanisms are discussed. The emulsified wax droplets are then subjected to ultraviolet irradiation, which photocatalytically degrades the silanes on the exposed portion of the particle surfaces, leading to Janus particles containing partial silane coatings. The particles are finally recovered through dissolution of wax. The Janus particles, which have contrasting wettabilities over their surface, are characterized based on self‐assembly behavior and bulk wetting performance in a compact film, as compared with nonfunctionalized and fully‐functionalized homogeneous particles. Three different types of Janus particles are created and their characters are explained using the concept of the Janus balance. The method has the potential to produce large scale yields in a relatively short time, and can be potentially applied to other semiconductor particles for the generation of Janus particles.

Evaluation of synthesized polymeric additives as paraffin inhibitors for wax dissolution in the petroleum reservoir rock

Abstract Precipitation of paraffin in petroleum reservoir rock can be a challenge to oil productivity for oil and gas industries. Paraffins exist in equilibrium with the crude oil under normal reservoir temperature and pressure. During the flow of crude oil through the petroleum formation, the proportion of lighter ends in crude oil underwent variation on account of localized pressure fluctuations. It led to reduction in solubility of heavy molecular weight hydrocarbons and they precipitate in the form of wax in the pores of reservoir rock. In this paper, wax deposition from crude oil was investigated using an experimental set up. The crude oil was characterized as medium heavy and waxy crude oil. Two paraffin inhibitors were synthesized in laboratory based on amination reaction of maleic anhydride with unsaturated amines. The monomer formed underwent free radical polymerization at 75 °C. The synthesized inhibitor was doped in crude oil to check wax dissolution through pores as compared to commercial paraffin inhibitors. In addition, the core was aged with crude oil for 15 days and alteration in its wettability was evaluated through changes in contact angle hysteresis with paraffin dissolution. It was found that synthesized paraffin inhibitors showed higher contact angle hysteresis as compared to commercial paraffin inhibitors, indicating excellent solubilisation of wax deposit in the pores of core.

MORPHOLOGY AND KINETICS OF PETROLEUM WAX DISSOLUTION IN HYDROCARBON SYSTEMS

This paper studies the effect of solvent chemical nature on the kinetic parameters of dissolution and the morphology of the petroleum waxes. The kinetics of the petroleum wax dissolution in gas condensate and the hexane-cyclohexane-benzene mixture was examined on the torsion balance within the temperature range from 10 to 40°C. The process was described using the Erofeev-Kolmogorov equation. The following kinetic parameters were calculated: reaction rate, the order of reactions and effective energy for activation the wax dissolution in the studied solvents. It was found that the wax dissolution rate in the ternary composite is an order of magnitude greater and the activation energy is three times less in comparison with the process of wax dissolution in the gas condensate. The morphological features of the wax samples, treated by these solvents, were examined by means of scanning electron microscopy. It was found that in the ternary composite, wax has a porous structure and in the gas condensate, it is compressed. Thus, the identified kinetic and morphological behavior of petroleum waxes indicates the influence of the chemical nature of the solvent. The findings of this study can be useful when choosing a solvent for the paraffin deposits removal.

Influencing factors governing paraffin wax deposition of heavy oil and research on wellbore paraffin remover

Wax deposition is harmful to oil wells, especially for waxy heavy oils at low temperature. The influencing factors on wax deposition of heavy oil were studied and a kind of O/W emulsion type wellbore wax remover was investigated. The results showed that the wax deposition rate of Jinghe heavy oil increased with the increasing wax content and asphaltenes content but decreased with the increasing water content. The oil in water emulsion type paraffin remover was prepared and it showed both good wax dissolution and paraffin prevention ability and can save large quantities of solvent. The results of this study provides a possible way for waxy heavy oils to dissolve wax, to prevent wax deposition and reduce the viscosity of heavy oils by emulsification together, which is helpful to reduce the frequency of hot washing and enhance oil recovery for waxy heavy oils.

Fischer-Tropsch Synthesis in supercritical Co2 – Inhibition of Co2 selectivity for enhanced hydrocarbon production

It has been generally observed that the fraction of the carbon in coal reporting as non methane hydrocarbons during coal to liquid (CTL) fuels process employing gasification and Fischer Tropsch Synthesis (FTS) using Fe based catalysts is less than 17% while theoretical limit for a CTL is around 52%. The use of supercritical CO2 as a solvent for FTS is shown to increase the reaction rates, suppress CO2 selectivity, reduce CH4 selectivity and thereby increase chain growth and improve the heat transfer and wax dissolution characteristics to increase catalyst longevity. This paper presents the results from proof of concept studies on FT synthesis in supercritical CO2 from syngas (H2:CO ∼1:1) typically produced from coal gasification and using a Fe-Zn-K/γ-alumina catalyst. Experiments were conducted with syngas alone, syngas diluted with N2 and syngas diluted with CO2. The high pressures improved the conversions and reduced the CO2 emissions. The dilution with N2 somewhat improved the CO conversions and CO2 emissions. However, CH4 emissions were found to increase. When diluted with CO2 and experiments conducted at pressures above the critical pressure, the data show, both, an overall shift in the product distribution towards higher hydrocarbons and reduction in the parasitic loss of carbon efficiency due to carbon dioxide formation along with significant improvement in the conversion rates. The use of the supercritical CO2 (ScCO2) inhibited methane and converted some of the CO2.

Structural features of reconstituted wheat wax films.

Cuticular waxes are essential for the well-being of all plants, from controlling the transport of water and nutrients across the plant surface to protecting them against external environmental attacks. Despite their significance, our current understanding regarding the structure and function of the wax film is limited. In this work, we have formed representative reconstituted wax film models of controlled thicknesses that facilitated an ex vivo study of plant cuticular wax film properties by neutron reflection (NR). Triticum aestivum L. (wheat) waxes were extracted from two different wheat straw samples, using two distinct extraction methods. Waxes extracted from harvested field-grown wheat straw using supercritical CO2 are compared with waxes extracted from laboratory-grown wheat straw via wax dissolution by chloroform rinsing. Wax films were produced by spin-coating the two extracts onto silicon substrates. Atomic force microscopy and cryo-scanning electron microscopy imaging revealed that the two reconstituted wax film models are ultrathin and porous with characteristic nanoscale extrusions on the outer surface, mimicking the structure of epicuticular waxes found upon adaxial wheat leaf surfaces. On the basis of solid–liquid and solid–air NR and ellipsometric measurements, these wax films could be modelled into two representative layers, with the diffuse underlying layer fitted with thicknesses ranging from approximately 65 to 70 Å, whereas the surface extrusion region reached heights exceeding 200 Å. Moisture-controlled NR measurements indicated that water penetrated extensively into the wax films measured under saturated humidity and under water, causing them to hydrate and swell significantly. These studies have thus provided a useful structural basis that underlies the function of the epicuticular waxes in controlling the water transport of crops.

Chemical Method for Inhibition of Wax and Scale Deposition in Low-Permeability Reservoirs

The goal of this work was to optimize a chemical method for preventing wax and scale deposition in the aqing Yushulin oil field (China). We studied the characteristics of the crude oil and the water injected into the formation in different sections of the oil field. Preliminary testing of the compositions for wax and scale removal was done as applied to this oil field, and we determined the optimal concentrations of the reagents. We estimated the wax dissolution rate, the effectiveness of wax and scale inhibition, and the degree of viscosity reduction in the crude oil. The reagents were chemically modified with the aim of improving their effectiveness. The process of wax crystallization in the crude oil containing wax inhibitors was studied by differential scanning calorimetry.

Thermal behavior and solid fraction dependent gel strength model of waxy oils

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min−1. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min−1. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines.

The effect of silica nanoparticle aggregates on wax dissolution in diesel oil

In recent years, silica nanoparticle aggregates (SNPAs) have been used to decrease the injection pressure of wells in low permeability reservoirs achieving good results. In order to study the mechanisms for reduction in the injection pressure of low permeability wells by the SNPA-diesel oil system injection, the microstructure of SNPAs was observed with a transmission electron microscope (TEM). The particle size distribution of SNPAs was also measured by the laser scattering method. The viscosities of diesel oil and SNPA-diesel oil system were measured with a capillary viscometer. The effect of SNPAs on the solubility of wax in the diesel oil was experimentally studied. The influencing factors, including temperature and SNPA concentration in diesel oil, on wax solubility were analyzed. A pore-throat film displacement model (PTFDM) was built for mechanism explanation. The microstructure and size distribution analyses show that the SNPAs are in the nanometer size range. The viscosity of the SNPA-diesel oil system is lower than that of the diesel oil. The solubility of wax in the diesel oil increases greatly due to SNPA addition, the solubility ratio reaches 7.5. The solubility of wax in diesel oil increases with increases in the concentration of SNPAs in the diesel oil and with the temperature. It is proved that the addition of SNPAs to diesel oil helps remove the wax deposited near the wellbore. This maybe one of the main mechanisms for injection pressure decreases in low permeability reservoirs.

The Hardening Process and Morphology of a Wax Deposit in a Pipe Flow

Paraffins crystallize out from waxy oil solution as temperature is lowered and form a deposit on transportation pipelines. The deposit becomes hard with an increase in its solid content, making cleaning difficult. A good knowledge of the crystal morphology is essential to understand the hardness of the deposit. The morphology of the deposit on a cold pipe was studied with scanning electron microscopy. The crystal morphology changed gradually from a round, plate-like crystal to mal-crystals and spherulites as the deposit grew. The deposit became harder with a decrease in its oil cavities created by lateral growing of macroplate crystals and formation of mal-crystals. The morphology change gradually occurs at temperatures between the cloud point and wax dissolution temperature depends on cooling rates. The results revealed another aging mechanism is the change in crystals morphology.

Fractionation and Characterization of Mexican Crude Oils

Crude oils are intricate mixtures of hydrocarbon compounds; different physicochemical characterizations must be performed to get to know their complexity. A series of four typical Mexican Crude Oils (MCOs) with densities ranging from 30 to 9 °API was characterized through different physical, spectroscopic, and thermal methods. The four types of MCOs were also fractionated into saturates, aromatics, resins, and asphaltenes (SARA) through high-performance liquid chromatography (HPLC). The fractions obtained were subsequently characterized through different physicochemical techniques such as Fourier transform infrared (FTIR) spectroscopy, vapor pressure osmometry (VPO), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). VPO led to determining the average molar mass of each MCO fraction to be compared to those of the different Mexican petroleums. It was clearly observed that the molar mass of the resin and asphaltene fractions increases when crude oil gets heavier than saturate and aromatic components. The thermal stability of the series of MCOs was evaluated by TGA observing that the decomposition temperature increases with the average molecular mass of the crude oil. The original heavy crude oil and its fractions were studied through differential scanning calorimetry (DSC); the study of heat effects associated to phase transitions was monitored for each fraction, resulting into the Wax dissolution temperature (WDT) and the Wax precipitation temperature (WPT) of the four MCOs investigated. It was established that the different molecular features of crude oils may be clearly correlated to their average molar mass.

Thermodynamic analysis for the interaction of polyacrylate with wax in heptane

The effect of polyacrylate (PA) on wax-precipitation temperature in heptane was investigated using differential scanning calorimetry (DSC). A thermodynamic analysis for the dissolution of wax in the absence and presence of PA was conducted. Results suggested that the change in wax-precipitation temperature caused by the introduction of the additives may be regarded as an index for characterizing the interaction of polymer additives with wax.

Fused Chemical Reactions: The Use of Dispersion To Delay Reaction Time in Tubular Reactors

Fused chemical reactions are delayed exothermic reactions. An axial dispersion model is used to simulate the flow of alternately injected pulses of reactants separated by an inert. There is a delay in reaction and heat release because the reactants have to disperse through the inert spacer to react. The feasibility of this technique is described for the reaction between ammonium chloride and sodium nitrite catalyzed by acetic acid. This technique can be successfully applied to the effective dissolution of wax deposited in subsea pipelines. The delay in the reaction is required to supply heat to regions further down the pipeline that are more susceptible to wax deposition. Simulation results show that the delay in the heat release depends on the width of the inert spacer as well as the catalyst concentration. However, the amount of heat released depends on the inlet concentrations of the reactants. Simulations can successfully determine the inlet concentrations of the reactants and catalyst as well as the ...