The interaction of waxes with pour point depressants

Paraffin wax deposition from crude oils at low temperature is one of the serious and long-standing problems in petroleum industry. Addition of pour point depressants (PPD) has been proved to be an efficient way to inhibit wax deposition. The influence of PPD on wax precipitation at low temperature was investigated. The amount and composition of wax precipitated from paraffin solutions with and without PPD at different temperatures were studied by high speed centrifuge and gas chromatography (GC), respectively. The interactions between waxes and PPD were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that PPD do not completely prevent the wax from precipitating, but just shift the precipitation toward a lower temperature. This conclusion was identified from the analysis of the amount and composition of precipitated wax as well as the transition temperatures and energies of wax. It was shown that this effect is due to the structure of wax is partly transformed from orthorhombic into hexagonal form by PPD.     

柴油降凝剂研究进展

本文综述了国内外柴油降凝剂的研究开发概况,降凝剂的种类及柴油降凝剂的复配研究,并对我国柴油降凝剂研制与开发提出了几点建议.     

Molecular dynamics simulation guiding the improvement of EVA-type pour point depressant

Addition of pour point depressants (PPDs) has been proved to be an efficient way to inhibit wax deposition of diesel fuels. However, the complexity of the oil is far beyond current commercial PPD products. So far it mainly depends on syntheses of numerous candidate compounds followed by repeating experimental measurements in order to improve the efficiency of PPDs. In this article, molecular dynamic simulation was successfully used to investigate the interaction between crystal planes of wax and EVA, as well as its derivatives with different branches, based on the model of wax. Side chain effects on adsorption energy and equilibrium adsorption conformations were studied under different kind and number of branches. It was concluded that side chains introduced by propylene were benefit to the affinity between the EVA-type molecules and alkanes in the wax plane, comparing with those branches introduced by butylenes. MD simulation calculations indicated that EVAP with one branch adjacent to the VA group would be a better PPD additive than EVA in diesel fuels, which has been proved in our experimental measurements. Therefore, the MD simulation is a promising method not only for exploring the interaction mechanism in polymer system, but also for directing the design of new candidates of PPD.     

柴油降凝剂研究的进展

叙述了国内外柴油降凝剂的研究开发概况，提出了对降凝剂作用机理的新看法以及柴油低温流动改进剂研究开发的方向     

Tuning of Cloud Point by the Nature of Surfactant Headgroup: Influence of Counterion and Additives

Work was performed to distinguish the role of sulfonate (–SO₃ ^?) and sulfate (–OSO₃ ^?) with respect to the micellization and clouding phenomenon in ionic surfactant solutions. The clouding phenomenon is a recent addition to the conventional one observed with nonionic surfactants. Three ionic surfactants [sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and sodium dodecylsulfonate (SDSo)] are chosen and the effects of added tetra-n-pentylammonium bromide (TPeAB) and benzyl tributylammonium bromide (BTAC) have been studied on micellization and clouding behaviors in aqueous solution. Based on critical micelle concentration (CMC) and cloud point (CP) measurements, the following order has been observed: SDBS < SDS < SDSo. Though both SDBS and SDSo contain sulfonate groups, they are found at the two ends of the ordering. Therefore, the role of the phenyl ring is also having importance in clouding phenomena. For a typical surfactant, TPeAB was found to be more effective than BTAC. Based on the CP studies, two compositions of SDSo + TPeAB/BTAC were chosen and the effects of different additives (carbohydrate, amino acid, and l-ascorbic acid) on the CP were investigated. Additive may either decrease or increase CP, depending on the structure of the counterion or additive. The present work shows a few novelties: (1) headgroup/counterion dependence of CP and (2) hydrophobicity of counterion/surfactant has an important bearing on the phenomenon. The data can be utilised in improving cloud point extraction methodologies (CPEMs).     

Cloud Point Extraction and Spectrophotometric Determination of Sulfide in Water Samples using Ethylene Blue Formation Reaction

Abstract

A rapid, selective, and sensitive cloud point extraction process using mixed micelle of a nonionic surfactant, Triton X-114, and an anionic surfactant, SDS, to extract sulfide from aqueous solutions was investigated. The method is based on the color reaction of sulfide with N,N-diethyl-p-phenylenediamine (DPD) in the presence of suitable oxidizing reagent (Fe³⁺) in acid media and cloud point extraction of ethylene blue (EB) dye. Various factors and optimal extraction and reaction conditions like: acid, Fe³⁺, reagent, and surfactant concentration were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, RSD%) were obtained. Linearity was obeyed in the range of 1–100 ng mL^?1 of sulfide ion. The detection limit of the method is 0.5 ng mL^?1 of sulfide ion. The interference effect of some anions, cations, and neutral species was also tested. The method was applied to the determination of sulfide in spring, river, and waste water samples.     

Polymeric additives for pour point depression of residual fuel oils

Esters of styrene-maleic anhydride copolymers were synthesised by reacting styrene with maleic anhydride and esterifying the product with fatty alcohols. The resulting copolymers were purified and tested as pour point depressants for residual fuel oils. Comparative evaluation of these esters of styrene-maleic anhydride copolymers with some commercial additives showed their good activity.     

Cloud point extraction: A sustainable method of elemental preconcentration and speciation

Trace elements are gaining increasing attention of scientists working in various analytical fields. Presence or absence of a trace element in a system seriously modifies its intrinsic behavior. Cloud point extraction (CPE) is an upcoming technology to preconcentrate and separate many of the trace elements from different chemical and biological systems. The system is sustainable as it involves benign extractants like surfactants and that too at low concentrations at slightly elevated temperatures to form clouds that separate out from the bulk solution. In addition, the extraction behavior of many elements depends on its chemical species. Keeping in view the need to summarize the research encompassing this technique, many review articles were published which cover a selection of the literature published on this topic over several time spans. A myriad of various technological developments has been reported by several workers. These developments have prompted us to revisit the CP technology with a better understanding of its detection, mechanism and extension to species dependent extraction behavior with regard to the state of art determination of trace metals in our day to day applications. The present article summarizes mainly the results of trace metal preconcentration using CP methodology from different practical samples with an insight to the probable mechanism and speciation involved from 2006 onwards.     

石化工业的一个增长点——聚合物共混物

聚合物共混物是石化工业的一个增长点,本文讨论了其发展特点、优点、制造和应用。     

Cloud Point Extraction and Preconcentration for the Determination of Cu and Ni in Natural Water by Flame Atomic Absorption Spectrometry

Abstract

In this work, a new cloud point extraction (CPE) method was developed for the separation and preconcentration of copper and nickel. The analyte was complexed with 3‐[(8‐{[(E)‐2‐hydroxyimino‐1‐methylpropylidene] amino}‐1‐naphthyl) imino]‐2‐butanone oxime (H₂mdo) in the initial aqueous solution and octylphenoxy polyethoxy ethanol (Triton X‐114) was added as a surfactant. After phase separation, based on the cloud point in the mixture, and dilution of the surfactant‐rich phase with methanol containing 0.1 mol l^?1 HNO₃, the enriched analytes were determined by flame atomic absorption spectrometry. After optimization of the complexation and extraction conditions (i.e. pH=8.5, H₂mdo=3×10^?4 mol l^?1, Triton X‐114=0.1% (w/v)) the enhancement factors of 65 and 59 and detection limits of 0.14 and 0.2 ng ml^?1 were obtained for copper and nickel respectively. The proposed method was applied to the determination of copper and nickel in several natural water samples with satisfactory results.     

Thermodynamic Parameters of Anionic Surfactant-Quaternary Phosphonium Bromides Systems at the Cloud Point

The thermodynamics of clouding in an anionic surfactant, sodium dodecyl sulfate (SDS) and quaternary phosphonium bromides systems in the presence of glycerol are reported. The standard Gibbs energy change of solubilization (Δ_sG°) for all of the additives was found to be negative. The standard enthalpy change (Δ_sH°) and the standard entropy change (TΔ_sS°) values were found to be negative as well as positive depending upon the type and nature of the additive. The results were explained on the basis of their nature, effect on the water structure, and solubilization of these additives either in the micellar or aqueous phase.     

Recovery of Saponins from Jua (Ziziphus joazeiro) by Micellar Extraction and Cloud Point Preconcentration

Juá (Ziziphus joazeiro) is a Brazilian plant and its bark has been used as a detergent and phytotherapic due to its high saponin content (2–10 %). Saponins are triterpenic glycosides with some properties that aid their use in food, cosmetic and pharmaceutical industries. The object of the present work was to develop an extraction and concentration process of saponins from jua bark, using green solvents such as water and ethanol. Firstly, the extraction conditions optimization was carried out using a central composite design, and compared with other methods such as Soxhlet, ultrasound-assisted extraction and micellar extraction. Then, cloud point preconcentration was tested to select the salt type and its concentration which promotes a higher concentration factor and partition coefficient at room temperature. Finally, the removal of a t-octyl phenol ethoxylate (9–10 EO) nonionic surfactant by adsorption was evaluated by optimizing the adsorbent type and its concentration, temperature and time of adsorption, in addition to the adsorbent recycling. Orbital shaker extraction leads to a recovery of 45.6 % saponins under the following conditions: temperature, 38.8 °C; jua/solvent ratio, 0.272; stirring speed, 300 rpm; extraction time, 2 h. Under these conditions, saponins recovery reached 90.8 % when using 15 % v/v of the nonionic surfactant, and a preconcentration factor of 14.2 was obtained by adding sodium carbonate 20 % w/v. The preconcentration factor decreased to a value of 10.1, after nonionic surfactant removal by a hydrophobic crosslinked polystyrene copolymer resin.     

The pressure effect on the wax formation in diesel fuel☆

The prevention of wax formation under high pressure on new diesel engine requires a good understanding of the behaviour of the paraffin molecules crystallization. In this work a diesel from a Petrogal refinery was investigated under pressure. In particular the melting curve was measured from atmospheric pressure to 100 MPa by an optical technique. The behaviour of the solid phase with the pressure was also investigated up to 50 MPa by filtration. The results obtained show an increase in the diesel cloud point of about 25 °C at the operating pressure of a common rail engine. It is clear from our results that the increase of the diesel cloud point must be taken into account in the development of new diesel engines where the diesel is injected under high pressure.All the results obtained were successfully predicted with a thermodynamic model able to describe multiphase equilibrium.     

Study of the Additive Effect on the Cloud Point of Nortriptyline Hydrochloride Solutions

The cloud point (CP) phenomenon has been studied in amphiphilic drug nortriptyline hydrochloride solutions with or without additives. The drug solutions were prepared in 10 mM sodium phosphate buffer. An increase in pH decreases the solution CP in the absence as well as the presence of additives (urea and TBuAB) due to deprotonation of the drug molecules. At constant pH (7.07), addition of simple salts (NaF, NaCl, NaBr) increases the CP by increasing the micelle hydration. Addition of Br salts (LiBr, NaBr, KBr) also increases the CP. The behavior is explained on the basis of the cation hydrated radius. Quaternary ammonium bromides, due to adsorption/mixed-micelle formation, also increase the CP, the order being: Bu<Pr<Et<Me. The urea family additives influence CP in both ways depending on whether they contain the >C = O or >C = S moiety. The former interacts with the micelles and decreases CP while the latter (due to its electropositive character) may not interact and hence increases CP.

Effect of Additives on the Cloud Point of the Octylphenol Ethoxylate (30EO) Nonionic Surfactant

The effect of different additives on the cloud point (CP) of an octylphenol ethoxylate (OPEO30) aqueous solution was investigated. The CP of OPEO30 is higher than 100 °C due to its approximately 30 oxyethylene units per molecule, which limits its use in cloud point extraction (CPE) procedures at room temperature. However, the presence of additives can promote a decrease in CP, allowing its use in CPE. Halide presence decreased the CP of OPEO30 in the following order F^? > Cl^? > Br^?. It was also observed that the addition of divalent anions resulted in a more pronounced salting‐out effect than monovalent anions. Blends of OPEO30 and its counterpart with 7.5 units of ethylene oxide (OPEO7.5) were also investigated, and it was verified that the CP of OPEO30 decreased linearly with increasing OPEO7.5 concentration, showing that mixing surfactants is a strategy to be explored. In the presence of small amounts of alcohols that are partially soluble in aqueous solution, such as isobutanol and pentanol, cloudiness was observed at temperatures below the CP of pure OPEO30 solution.     

Correlations Between Cloud Point and Compositional Properties of Palm Oil and Liquid Fractions from Dry Fractionation

Dry fractionation of palm oil can be conducted as a multi-step process; this gives rise to new softer and harder fractions having multitudes of applications in fat foods. This work focuses on the liquid fractions obtained following a triple-step fractionation; the cloud point was measured on a set of 125 palm oil, olein, super olein and top olein samples, with the intention to correlate this value to the compositional properties. The Mettler cloud point, the diacylglycerol content, some selected single or groups of triacylglycerols and the iodine value (in total, 11 variables per sample) were measured and entered in a statistical model. A principal component analysis (PCA) was first carried out from which different sub-groups were highlighted. In each sub-group, various regressions (simple linear, simple non-linear and multiple linear) were applied and 28 significant equations were derived. Out of these, one multiple linear regression involving the iodine value, the UUU and PPP contents showed the best correlation with the Mettler cloud point. This equation was selected to predict the cloud point since it was further successfully validated by using a set of 25 other independent samples. A partial least square (PLS) regression was tested and also considered adequate to predict the cloud point.     

Cloud point extraction of methylphenol in water samples with low viscosity of non-ionic surfactant Sylgard 309 coupled with high-performance liquid chromatography

A cloud point extraction method is developed for the extraction of methylphenol from various water samples using the non-ionic surfactant, Sylgard-309. Methylphenol in the water is a toxic element that is dangerous to humans. Hence, the treatment of water containing methylphenol is necessary. The method’s optimum conditions are 2.0 M salt concentration and 10% of surfactant concentration at room temperature. The limit of detection and limit of quantification of the method is 0.109 ppm and 0.365, respectively. The extraction recoveries of methylphenol in water samples (tap water, lake water, river water and sea water) are in the range of 90–99% with the relative standard deviations of less than 1.5%.     

Removal of Tannic Acid From Aqueous Solution by Cloud Point Extraction and Investigation of Surfactant Regeneration by Microemulsion Extraction

The aim of this work is the extraction of tannic acid (TA) with two commercial nonionic surfactants, separately: Lutensol ON 30 and Triton X‐114 (TX‐114).The experimental cloud point extraction results are expressed by four responses to surfactant concentration and temperature variations: extent of TA extraction (E), remaining solute (X_s,w) and surfactant (X_t,w) concentrations in dilute phase and volume fraction of coacervate (Φ_c) at equilibrium. An empirical smoothing method was used and the results are represented on three dimensional plots. In optimal conditions, the extraction extent of TA reaches 95 and 87 % using TX‐114 and Lutensol ON 30, respectively. Sodium sulfate, cetyltrimethylammonium bromide (CTAB) addition and pH effect are also studied. Finally, the possibility of recycling of the surfactant is proved.     

Cloud Point Extraction of Glycyrrhizic Acid from Licorice Root

Abstract

An attempt has been made to extract glycyrrhizic acid (GA) from licorice root by surfactant mediated cloud point extraction (CPE) using non‐ionic surfactant (Triton X‐100). Almost all of the GA molecules were concentrated in the surfactant‐rich phase (also called coacervate phase) after phase separation. The pH is the most critical factor regulating the distribution of GA in the micelle which related to the ionization form. The other effects of the concentration of GA and the surfactant, the temperature, and the salt concentration on the extraction efficiency of GA in the coacervate phase and aqueous phase have been studied. The mechanism of CPE of GA was explored with transmitting electron microscopy. It was deduced that aggregate GA molecules were adsorbed on micelles' outer poler mantle and inner cross‐linked micelles at high GA concentrations in coacervate phase.