Effect of wax inhibitors on pour point and rheological properties of Iranian waxy crude oil

A variety of techniques have been employed in order to reduce problems caused by the crystallization of paraffin during the production and/or transportation of waxy crude oil. Flow improvers are used extensively to increase the mobility of crude oil. In this study, the influence of the ethylene-vinyl acetate copolymer (EVA), as flow improver, with different ranges of molecular weight on the viscosity and pour point of five Iranian waxy crude oils was evaluated. Five types of Iranian waxy crude oil were selected based on their similar wax (> 10%) but different asphaltene contents. Also, the effect of asphaltene content on the performance of this flow improver was studied. The rheological behavior of these crude oils, with middle range API gravity, in the absence/presence of flow improver was studied. The rheological data cover the temperature range of 5 to 40 °C. The results indicated that the performance of flow improver was dependent on the molecular weight and the asphaltene content. For crude oil with low asphaltene, higher molecular weight flow improvers are the best additive and lower molecular weight flow improvers showed good efficiency for crude oil with high asphaltene content. Addition of small quantities of asphaltene solvents such as xylene (1 wt.%), alone or in combination with flow improver, can improve viscosity of crude oil with high asphaltene content.     

Designing maleic anhydride-α-olifin copolymeric combs as wax crystal growth nucleators

Modification of the wax crystal habit is of great practical interest during transportation and processing of crude oil at low temperature. Various pour point depressant (PPD) additives can facilitate this modification by different mechanisms. Comb shaped polymer additives are known to depress the pour point of crude oil by providing different nucleation sites for the precipitation of wax. This paper describes performance based design, synthesis, characterization and evaluation of comb shaped polymeric diesters. Copolymers of maleic anhydride with different unsaturated C₂₂ esters were synthesized and copolymers then reacted with two unsaturated fatty alcohols. All products were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and Gel Permeation Chromatography (GPC). Rheological properties of crude (with and without additive) were studied by Advance Rheometer AR-500. In this study the additive based on oleic acid was evaluated as good PPD and rheology modifier.     

Polymeric structures as cold flow improvers for waxy residual fuel oil

Acrylic and methacrylic acids were esterified with dodecyl, hexadecyl and NAFOL 20⁺ (C_av = 21) alcohols. The monomers thus prepared were copolymerized with C₁₈ α-olefin at different molar ratios. The copolymers were purified, characterized and then assessed as cold flow improvers for a high-pour waxy residual fuel oil (RFO) by pour point and rheological measurements. The asphaltene, resin and wax contents of the RFO as well as the carbon number distribution of the wax fraction were determined. The results show that only the polymeric structures with long side chains of NAFOL 20⁺ have the potential to decrease the pour point and improve the rheological properties of the fuel oil. The storage stability of the treated RFO is good up to 3 days but then diminishes steadily. The effectiveness of the prepared additives is discussed on the basis of structure in relation to the fuel oil composition.     

Polymeric additives for improving the flow properties and viscosity index of lubricating oils

Four sets of copolymeric additives were synthesized via copolymerization of dialkyl fumarates and dialkyl maleates with vinyl acetate (VAc) and vinylpyrrolidone (VP) monomers. The dialkyl esters were prepared by the esterification of maleic and fumaric acids with a series of n-alkanol having an increasing number of carbon atoms to produce two groups of diesters. The completion of the esterification reaction was confirmed by spectroscopic analysis. The molecular weights of the prepared esters and copolymers were determined and the influences of different parameters on the molecular weight of the produced copolymers were discussed. The efficiency of the prepared copolymers as viscosity index and flow improvers (pour point depressants) was investigated. It has been found that the dialkyl ester/VP copolymers are more efficient as viscosity index improvers than the dialkyl ester/VAc copolymers. On the other hand, it has been found that the copolymers based on didodecyl fumarate/VAc are the most effective pour point depressants.     

A new method for the determination of wax precipitation from non-diluted crude oils by fractional precipitation

Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method.     

Synthesis and evaluation of alkyl fumarate–vinyl acetate copolymers in combination with alkyl acrylates as flow improvers for Borholla crude oil

A number of alkyl fumarate–vinyl acetate copolymers were prepared and evaluated as flow improvers for high waxy Borholla crude oil. Alkyl fumarate–vinyl acetate copolymers having 19·2 as the average carbon number of the alkyl group in combination with polybehenyl acrylate were found to show optimum activity. Alkyl fumarate–vinyl acetate copolymers reduce the pour point, plastic viscosity and yield stress considerably and polybehenyl acrylate prevents the crude oil from attaining the gel structure on prolonged storage.     

Additives from aromatic extracts

Aromatic extract residues, as by-products, are accumulated in local refineries through the refining of lubricating oils. These residues are dealt with as low economic value products, even their disposal imposes serious problems to the refineries. Therefore, the present work is aimed at upgrading these residues by using them to synthesis some different petroleum additives, e. g. antioxidants, ashless dispersant additives, pour point depressants and flow improvers for crankcase lubricating oils and fuels. Antioxidants are synthesised by reacting mono-aromatics with phosphorus pentasulphide (P₂S₅) in the presence of zince oxide (ZnO). Ashless dispersant additives are synthesised by reacting alkylated mono-aromatics (using chlorinated paraffin wax as alkylating agent) with formaldehyde solution (37%) in the presence of polyisobutylene succinimide. Pour point depressants and flow improvers are synthesised by acylating di-aromatics via a Friedel-Crafts' reaction. Comparative evaluation of the performance of the synthesised products with commercial additives showed their good efficiency.     

The Behavior of α-Olefins Butyl Acrylate Copolymers as Viscosity Index Improvers and Pour Point Depressants for Lube Oil

A lubricant additive may be defined as a material that imparts a new and desirable property not originally present in the oil or reinforces a desirable property already possessed in some degree by the oil. These materials are normally more chemically reactive than the base oil. The additives are being used at various concentrations from a few parts per million to over 30%. A great deal of research is being done at present into the synthesis, technology, and applications of different lube oil additives. In the present work, polymeric additives were prepared by reaction of butyl acrylate with different α-olefins (octene, dodecene, tetradecene, and octadecene). The efficiency of the prepared copolymers as viscosity index improvers and pour point depressants for a base lube oil were studied. It was found that the efficiency as viscosity index improvers increases with increasing the concentration of the prepared copolymers and increasing the chain length of alkyl groups of the α-olefins, and the efficiency as pour point depressants increases with decreasing the concentration and decreasing the molecular weights of the prepared copolymers.     

Synthesis of Dimer Acid 2-Ethylhexyl Esters and their Physicochemical Properties as Biolubricant Base Stock and their Potential as Additive in Commercial Base Oils

Previously synthesized C36-dimer acids (DA) have been esterified (97 ± 0.2% conversion at 120 °C for 72 hours) with 2-ethylhexanol (2-EH) to produce a new class of C52-DA 2-EH esters that have potential application in biolubricant formulations such as base oils and additives. Investigation of physicochemical and lubricant properties showed the bio-based esters have good solubility in commercial base stocks such as polyalpha olefin (PAO-6) (>20 w/w) and high-oleic sunflower oil (HOSuO) (>20 w/w). The neat C52-DA 2-EH esters displayed a three- to eightfold higher kinematic viscosity and comparable viscosity index (VI = 134) as a commercial base stock, PAO-6 (VI =137). Both C52-DA 2-EH esters, whose parent C36-DA were synthesized with two different zeolite catalysts, were oxidatively stable above 176 °C. Blending C52-DA 2-EH esters in HOSuO improved the pour point (PP) of HOSuO from −18.8 to −21.0 °C at 1% w/w and the cloud point (CP) from −6.3 to −10.6 °C at 8% w/w of C52-DA 2-EH ester 1. A similar trend was observed for C52-DA 2-EH ester 2, indicating that the esters possess PP depressant (PPD) characteristics in HOSuO blends. Blending C52-DA 2-EH esters in PAO-6 increased the VI of PAO-6, which is an indication that the bio-based esters were acting as VI improvers (VII). It was concluded that C52-DA 2-EH esters can be employed commercially as bio-based base oils and as PPD and VII additives in lubricant formulations.     

BEM/PMSQ杂化降凝剂对青海含蜡原油作用效果及其机理

基于聚甲基硅倍半氧烷（PMSQ）微球良好的有机相容性与规则的微观球形形貌,将PMSQ微球与BEM降凝剂通过熔融共混制备了BEM/PMSQ杂化降凝剂。以青海含蜡原油为研究对象,通过流变实验评价了BEM/PMSQ杂化降凝剂对原油的凝点、黏弹性、黏度与屈服值的影响,利用偏光显微镜观察了加剂前后原油蜡晶形貌的变化,并与单独添加BEM降凝剂的油样进行了对比。结果表明：不加剂原油凝点27.0℃;在相同的降凝剂加量下（100 μg·g^-1）,降凝效果最好的是BEM/PMSQ 2%杂化降凝剂,可降低原油凝点19.0℃,相较于添加BEM降凝剂,进一步降凝6.0℃,降低胶凝点4.3℃,10℃时平均降黏率39.0%,G'值降低了62.0%。PMSQ微球与BEM/PMSQ杂化降凝剂在十二烷中的分散状态照片表明PMSQ微球表面吸附了BEM降凝剂,从而在原油中作为蜡晶的成核模版存在,使所形成的蜡晶结构更为紧凑,包覆更少的液态油,从而改善原油的宏观流变性。     

Some substituted polysaccharides as low temperature middle distillate additives

Substituted polysaccharides with different molecular weights (mol. wt 12 000–15 500) were synthesised by reacting aliphatic acid chlorides with different carbon numbers (C₁₂-C₁₈) with dextrin. The resulting polymers were purified and tested as pour point depressants and flow improvers for middle distillates (gas oils). Comparative evaluation of these polysaccharides with some commercial additives showed their good activity, especially as flow improvers.     

The effects of metallic catalysts on light crude oil oxidation in limestone medium

In this study, 28 experiments were performed to study the effects of metallic additives on light crude oil oxidation in limestone medium. Karakuş and Beykan crude oils from Turkish oil fields were used. The metallic additives were ferric chloride (FeCl₃), copper chloride (CuCl) and magnesium chloride (MgCl₂·6H₂O). The mixture of aqueous solutions of three metallic salts with limestone and the crude oils was subjected to a controlled heating schedule under a constant flow rate of air. The produced gas was analysed for its oxygen and carbon oxides contents.The results of reaction kinetics showed that the molar CO₂/CO ratio values of fuel combustion increased when additives were added. A decrease in the atomic H/C ratio with an increase in temperature was observed for all runs. The reaction order, m in Arrhenius equation increases as concentration of copper and magnesium chloride additive increases but decreases as ferric chloride additive increases in both crude oils. It is observed that the metallic additives except ferric chloride decreased the Arrhenius constant, Ar, for both crude oils.As concentration of ferric chloride increases the activation energy of Karakuş crude oil increases while activation energy of Beykan crude oil decreases. The copper chloride additive shows same trend for both crude oils. The 1.0 mol% concentration decreases the activation energies. The 2.0 mol% magnesium chloride increases the activation energy of Karakuş crude oil while decreases the activation energy of Beykan crude oil more than 1.0 mol% does.For Karakuş crude oil, the oxygen consumption curves of 2.0 mol% of metallic additives show one peak. There is similar behavior between runs with 1.0 mol% of ferric chloride and magnesium chloride and runs with no additive, but the oxidation reaction peaks with metallic salts at both concentrations occurs at lower temperatures. For Beykan crude oil, all the additives lower the peak temperature when they are compared to standard run. The trends of the curves are actually the same. Copper chloride shows one peak with the 1.0 and 2.0 mol% runs for both crude oils.     

Ozonized vegetable oil as pour point depressant for neat biodiesel

The use of ozonized vegetable oils as pour point depressant for neat biodiesel was evaluated. Ozonized vegetable oils (1-1.5% by weight) were effective in reducing the pour point of biodiesel prepared from sunflower oil, soybean oil and rapeseed oil to −24, −12 and −30 °C, respectively. Cloud point however remained unaffected. In the case of palm oil biodiesel, significant reduction was observed in cloud point but not in pour point. Statistical analyses showed that neat biodiesel and biodiesel treated with ozonized vegetable oils showed no significant difference in other properties including density and viscosity. Although ozonized vegetable oils increase the flash point of biodiesel, the values are still within the limits set by the standards in the US and Europe. Lowest reduction in pour point was observed in cases where the biodiesel and the ozonized samples were prepared from the same vegetable oil. Hence, a correlation may exist between the nature of the biodiesel and ozonized oil. Microscopic analysis at low temperature revealed that ozonized vegetable oil impede agglomeration of biodiesel into network of solidified material giving crystals with sizes around 10 μm.     

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.     

集输工艺对高蜡原油中降凝剂作用的影响分析

高蜡原油的集输工艺对降凝剂的降凝降黏作用有较大影响。使用降凝剂AE对吉林木南原油降凝处理,考察了集输过程中降凝剂加量和加剂温度、泵的高速剪切、原油的重复加热和输送过程中冷却速率等工艺条件对降凝剂作用效果的影响。结果表明,降凝剂最佳加剂量0.7%,最佳加剂温度70℃,高速剪切温度应在析蜡点10℃以上,重复加热温度应不低于60℃,在55～40℃的析蜡高峰区应使原油温度缓慢降低。     

Studies on the influence of long chain acrylic esters polymers with polar monomers as crude oil flow improver additives

This study investigated the efficiency of 22 polymer additives of defined and controlled structural characteristics in improving the flow properties of crude oil. The additives were synthesized by the solution polymerization of alkyl acrylates of various alkyl chain lengths with styrene, acrylic acid and 1-vinyl-2-pyrrolidone as copolymers or terpolymers. Polymerization was performed by tert-butylperoxy-2-ethylhexanoate as initiator in xylene at 92 °C, up to high conversion. The influence of polymerization conditions on additive composition and properties, and their effect on the pour point and rheological properties of crude oil samples from the fields of ?tevkovica, Obod and ?eletovci located in the northern Croatia were studied. Additive efficiency was dominantly influenced by the alkyl acrylate chain length. The influence of component with carboxyl functional group or heterocyclic-nitrogen compound on additive quality was less obvious. Additive efficiency significantly depended on the properties of crude oil, and n-paraffin content and distribution. The main advantage of the process is that additives can be directly used without purification.     

Preparation and application of flow improvers additives for super-viscous crude oil

通过多元高碳醇与甲基丙烯酸酯化、共聚和胺解,研制出新型胺解共聚物型超稠原油流动改进剂,将流动改进剂应用于辽河超稠油中,进行黏温性能测试和模型预测分析。实验结果表明,由于胺解共聚物流动改进剂具有与稠油较为相似的结构组成,使得原油内部大基团溶解而促进原油流动,因而显示出对超稠油独特的降黏效果,平均降黏率50%,最高可达到80%以上。建立了原油黏度随温度变化的预测模型并进行了三维参数模拟,预测模型的相关性达到0.987。     

英旺油田高含蜡原油降凝剂筛选及现场应用

英旺油田长8油层高131原油具有凝固点较高（17℃）,高含蜡量13．58％特点,运用单一药剂对其降凝效果不明显,分散剂和添加剂复配可有效降低该储层原油凝固点。在添加剂最佳浓度为0．5％,分散剂最佳浓度为5％时,可使长8储层原油凝固点从27℃降低到4．5℃。现场试验表明,采出液凝点均已降低到5℃以下,原油流动性也很好,产量有所增加且稳定。     

原油降凝剂的合成及性能研究

针对我国原油含蜡量较高的特点,采用在原油中加入化学降凝剂的方法,对原油降凝。以高活性聚异丁烯为主要原料,先与苯进行烷基化反应得到聚异丁烯烷基苯,再以浓硫酸为磺化剂进行磺化反应,制得的烷基苯磺酸经中和反应制得烷基苯磺酸盐原油降凝剂。红外光谱分析表明,产物为预期产物。用偏光显微镜研究了加剂前后晶体形态,并探讨了降凝机理。通过对产物与大庆原油进行的降凝效果的测定,证实合成的产物在大庆原油中加入量为0.6%时降凝效果最好,降凝幅度为8℃。     

Co-adsorption behaviors of asphaltenes and different flow improvers and their impacts on the interfacial viscoelasticity

Commonly used flow improvers in oilfields, such as ethylene–vinyl acetate copolymer (EVA), poly(octadecyl acrylate) (POA), and polymethylsilsesquioxane (PMSQ) are proven to be effective to enhance the flowability of crude oil. However, the addition of these flow improvers may change the stability of the emulsion and make the crude oil treatment process challenging. In this research, the impacts of different flow improvers on the interfacial properties of the emulsions containing asphaltenes are systematically investigated. The co-adsorption behaviors of the flow improvers and asphaltenes are analyzed through dynamic interfacial tension (DIFT). The rheological properties of the interfacial layer after the adsorption are explored via dilational viscoelasticity. Significant difference is observed in the structural properties of the interface adsorbed by different flow improvers, which is attributed to different interactions between the flow improvers and asphaltenes. To investigate these interactions, conductivity, asphaltenes precipitation, dynamic light scattering (DLS), and contact angle experiments are conducted systematically. Results show that EVA and POA can alter the interfacial properties by changing the asphaltene dispersion state. The interaction between EVA and asphaltenes is stronger than that between POA and asphaltenes due to the difference in molecular structures. Unlike EVA and POA, the change of interfacial property with the addition of PMSQ is attributed to the partial adsorption of asphaltenes on PMSQ.