大豆油生物柴油低温流动性能影响的研究

以大豆油为原料采用碱催化酯交换法合成生物柴油,测定了其酸值、游离甘油、总甘油、灰分、黏度和磷含量等指标。实验表明,共存的甲醇、水分和甘油酯对生物柴油的低温流动性能影响极少,饱和脂肪酸甲酯的同时析出对生物柴油低温流动性能起关键作用。考察了5种柴油降凝剂、0号和20号柴油以及乙醇对生物柴油低温流动性能的影响。0号柴油有效地改善生物柴油黏度,但对其低温流动性能影响不大。20号柴油和乙醇能显著降低生物柴油的凝点、倾点、冷滤点和黏度。其中3种降凝剂有效降低生物柴油的凝点和倾点,1种降凝剂能小幅度改善冷滤点,5种降凝剂都能使生物柴油的黏度小幅上升。     

低温下生物柴油的胶凝特性研究

利用流变仪在小振幅振荡剪切模式下对地沟油、花生油和大豆油生物柴油的胶凝特性进行了研究。结果表明,低温下生物柴油不仅具有冷却胶凝特性,还表现出明显的等温胶凝特性。分析了冷却速率和剪应力对地沟油生物柴油胶凝特性的影响。结果表明,静态降温时降温速率越大,生物柴油的胶凝温度越低,降温及恒温静置过程中同一温度下的胶凝结构越弱。相同降温速率下,生物柴油的胶凝结构和胶凝温度随剪应力的增加而降低,但经受不同剪应力作用的生物柴油恒温静置后胶凝结构相差不大。降温过程中施加的剪应力较小时,冷却胶凝结构随降温速率的增大而降低;剪应力较大时,冷却胶凝结构随降温速率的增大而加强。不管施加的剪应力多大,等温胶凝结构随降温速率的增大而加强。     

生物柴油的催化改性对其冷滤点的影响

利用HZSM-5型分子筛作为催化剂,在250℃～350℃、0.01MPa～0.04MPa的条件下,对生物柴油的主要组分油酸甲酯、棕榈酸甲酯、硬酯酸甲酯、亚油酸甲酯、月桂酸甲酯进行催化改性,以达到降低生物柴油冷滤点（CFPP）的目的。实验研究了反应温度和反应真空度对各脂肪酸甲酯产物的冷滤点、结炭率、碘值的影响,以该实验数据为依据,将动物油经过酯交换制备的生物柴油（AFE）进行催化改性。结果表明,在300℃~350℃,对饱和脂肪酸甲酯改性有很好的降凝效果,产物碘值升高;油酸甲酯通过改性,也取得了很好的降凝效果,产物碘值下降,在该反应条件下改性饱和脂肪酸甲酯和油酸甲酯催化剂的结炭率保持在5%以下;而亚油酸甲酯仅在350℃时改性才有降凝效果,且结炭率在10%以上。生物柴油（AFE）催化改性达到最佳降凝效果的条件为300℃~325℃,0.01MPa,改性后的的酸值小于0.6mg/g,冷滤点下降了19℃,碘值（I.V）为44.32g/100g,运动黏度（μ_t）为4.397mm²/s,并且催化剂结炭率保持在5%以下。     

煤灰在高温下的流变特性研究

为了研究煤灰在高温下的流变特性,以陕西神木煤、内蒙纳林沟煤、宁夏羊肠湾煤和山东南屯煤四种煤灰为样品,利用高温旋转黏度计,研究了高温下煤灰渣黏度和剪切应力随剪切速率的变化。实验结果表明,当实验温度高于煤灰的液相线温度时,其流型表现为牛顿流体;当温度低于液相线温度时,其流型逐渐由牛顿流体转变为非牛顿流体。其中,陕西神木煤和宁夏羊肠湾煤的煤灰样品在高温下表现为剪切增稠,随着温度的降低,由牛顿流体转变为屈服涨塑性流体;内蒙纳林沟煤和山东南屯煤的煤灰样品在高温下表现为剪切变稀,随着温度的降低,由牛顿流体转变为屈服假塑性流体。另外,随着温度的降低,由于液态煤灰中晶体的不断析出,使屈服应力逐渐增大,降低了煤灰的流动性。     

几种典型含氟树脂流变行为研究概述

主要对乙烯-四氟乙烯共聚物(ETFE)、聚全氟乙丙烯(FEP)、聚偏氟乙烯(PVDF)、全氟磺酸树脂(PFSA)和全氟羧酸树脂(PFCR)这几种典型含氟树脂的加工流变行为和线性粘弹性进行了综述。FEP高速挤出时稳定流动区非常窄,并且进行模型拟合时发现其剪切流动行为符合Carreau模型。ETFE为热流变简单高分子,其剪切粘度、拉伸粘度、挤出胀大和动态模量等流变函数均可进行时温叠加。在低剪切速率下,PVDF熔体表现出牛顿流体行为;在高剪切速率下,PVDF熔体呈现出剪切稀化现象。PFSA和PFCR熔体的表观黏度随剪切速率、温度的升高而降低,流动曲线显示该熔体属于假塑性流体。     

不同酯基结构的棕榈油生物柴油的性能研究

以棕榈油为研究对象,分别与甲醇、乙醇、异丙醇和异丁醇进行酯交换反应制备了不同酯基结构的生物柴油。利用差示扫描量热仪和应力控制流变仪分析了不同酯基结构棕榈油生物柴油的结晶行为和低温流变性能,同时分析了酯基结构对生物柴油的氧化稳定性,40℃时的动力黏度、20℃时的密度等重要性质的影响。结果表明,随着醇的碳链长度的增加,棕榈油生物柴油的析蜡点和胶凝点均降低,特别是棕榈油异丁酯的析蜡点和胶凝点分别降低到了-2.57和-8.09℃,低温流动性得到了明显改善,且氧化诱导期略有延长,氧化稳定性有所改善。生物柴油的密度和黏度随着酯基结构的不同而有所变化,但其数值都符合中国生物柴油标准。     

胜利煤液化油煤浆表观黏度的影响因素研究

采用高温黏度计测定了胜利褐煤液化油煤浆在常压加热条件下的表观黏度,考察了煤浆质量分数、煤粉粒径、溶剂性质以及温度、剪切时间、剪切速率、溶胀等因素对煤浆体系表观黏度的影响。在常压室温至350℃的范围内,比较了胜利煤在起始溶剂和循环溶剂两种煤浆体系中的表观黏度。研究结果表明,胜利液化油煤浆体系是一种非牛顿流体,随着温度的升高,煤浆体系的黏度呈现先快速下降,然后基本保持不变,最后又逐渐上升的趋势。煤浆黏度保持不变的温度区间和黏度开始出现增加的温度随着煤浆的质量分数、煤粉的粒径以及配制煤浆所用溶剂的不同而不同。     

煤加氢液化残渣的流变特性研究

采用从煤直接液化实验装置取得的液化残渣,研究了它的流变性及温度和油、沥青质、固体含量对其流变性的影响。液化残渣是剪切变稀的非牛顿型假塑性流体,非牛顿指数随温度升高而不断减小,温度越高越接近牛顿流体行为。液化残渣对温度非常敏感,在升温过程中其表观黏度下降很快,且没有出现黏度峰。在液化残渣中加入少量的循环油后其表观黏度大幅下降;而在加入少量沥青质后则表现出低温下黏度变大,高温下黏度变小的现象;固体含量则始终是黏度增大的因素,表明其黏度与油、沥青质和固体含量关系密切。液化残渣的黏度－温度关系符合Arrhenius关系式,但在升温过程中出现了拐点,低温段的黏流活化能比高温段的要大。     

生物柴油调合对其低温流动性能的改善

为了了解生物柴油中脂肪酸甲酯组成对其低温流动性能的影响,探索改善其流动性能的方法,以大豆油、花生油和牛油为原料合成了大豆油甲酯、花生油甲酯和牛油甲酯,测定了它们的脂肪酸甲酯组成和低温流动性能.结果表明,长碳链饱和脂肪酸甲酯的含量是影响生物柴油低温流动性能的主要因素.通过对混合生物柴油流动性能的测定,发现可以通过不同来源...     

气相色谱法在生物柴油生产工艺研究中的应用

综述了气相色谱法在生物柴油生产工艺研究中的应用,包括反应产物和生物柴油产品中脂肪酸甲酯含量和分布的测定,单脂肪酸甘油酯、二脂肪酸甘油酯和三脂肪酸甘油酯含量的测定,游离脂肪酸含量的测定以及微量甲醇含量的测定等。讨论了进样方式、色谱柱类型、硅烷化等因素对反应产物组成测定的影响;提出了一种采用双柱压力反吹的方式测定生物柴油产品中微量甲醇含量的方法：采用正丙醇作内标,甲醇与内标通过预切柱进入分析柱后,通过压力变化,将其余组分通过分流出口反吹出色谱系统;采用极性聚乙二醇色谱柱测定了8种不同植物油中脂肪酸甲酯的含量和分布。     

Rheological evidence for the existence of subphases in the liquid crystalline 4-n-alkoxybenzoic acids

The rheological behaviour of the homologous series, the alkyloxybenzoic acids, has been studied at steady flow and small amplitude oscillatory shear. The temperature dependencies of the viscosity were compared with differential scanning calorimetry data in order to estimate pretransitional phenomena in mesophases. The values of the viscosity and flow activation energy (E) can be indicative of the mesophase state. 4-n-pentyloxybenzoic acid yields a classic nematic (N) phase while the next homologues show a cybotactic nematic phase having a higher E value. The N phase is a Newtonian fluid of lower viscosity than that of the isotropic phase. The cybotactic nematic phase by its rheological properties takes an intermediate position between the N phase and a smectic C (SmC) phase. The SmC phase is a viscoelastic and viscoplastic medium. The SmC phase of 4-n-octyloxy-, 4-n-nonyloxy-, 4-n-decyloxy- and 4-n-dodecyloxybenzoic acid can exist in high- and low-ordered states. The more ordered smectic phase is characterised by higher stiffness, viscosity and yield stress than those of the less ordered. The SmC phase of 4-n-hexadecyloxybenzoic acid is characterised by the only state with unstable value of apparent viscosity. The phase state and the transition temperature can be dependent on the thermal history of the sample and a mechanical shear.     

A rheological and morphological study of a copolyester liquid crystal/polypropylene blend system

The effects of composition and shear rate on the rheology and morphology of blends of LC–3000, a thermotropic liquid crystalline polymer consisting of 60/40 of hydroxybenzoic acid and poly(ethylene terephthalate), with polypropylene were studied. It was found that the rheological properties depend in a complex manner on composition and applied shear. Both positive and negative deviations from the log-additivity rule were observed at low shear rates. Significant viscosity reduction was measured when the dispersed phase was a nematic TLCP. The accompanying microstructural transitions were characterized a posteriori, and it was found that the state of dispersion of the TLCP phase also influences the viscosity reduction phenomenon. A nematic, fibrillar TLCP phase shows a viscosity reduction of the order of fourfold with respect to the viscosity of the matrix. Another important finding was that the stability of these fibers would not be expected from work on other non-TLCP-containing immiscible blends. This suggests that the unique rheology of the TLCP minor phase is relevant to the formation of stable fibers. © 1996 John Wiley & Sons, Inc.     

Producing fuel and specialty chemicals from the slow pyrolysis of poultry DAF skimmings

The production of bio-oil via the slow pyrolysis of dissolved air flotation (DAF) skimmings from poultry processing is described. The raw DAF skimmings were characterized for physicochemical properties and for thermal behavior (TGA). The bio-oil was produced in a batch pyrolysis system at varying temperatures between 400 and 700 °C to study the effect of temperature on product yield. The fatty acids in the bio-oil produced displayed a high degree of saturation that caused the bio-oil to have poor cold flow properties (high cloud point and viscosity) so a solvent extraction scheme was devised to extract a bio-oil fraction rich in unsaturated fatty acids that could be further esterified into a bio-diesel and fatty nitriles that could be further processed into surfactants. This ethyl acetate-soluble fraction demonstrated much improved cold flow properties as well as lower water content and a higher HHV. The esterification of this soluble fraction was performed using methanol and sulfuric acid as an acid catalyst and the formation of fatty acid methyl esters was verified using GC/MS and FT-IR.     

The effects of some factors on the rheological properties of the lyotropic liquid crystals formed in Brij97/NaDC/IPM/water system: compositions,temperature and polyphenols

In this paper, interaction between Brij97 and NaDC in mixed micelles was studied by surface tension method. Phase behavior for Brij97/NaDC/IPM/H₂O system was investigated at the desire molar ratio of α_NaDC?=?0.42 and the human body temperature of 37?°C. Hexagonal and cubic liquid crystal were found in this system analyzed by small angle x-ray scattering (SAXS). some factors were changed to affect the rheological properties of liquid crystal. Rheological investigations showed: The higher content of water and lower experimental temperature favored the greater values of shear viscosity and viscoelastic modulus; The sample was closer to the plastic fluid and was more likely to recover from disturbed state to equilibrium state at lower ratio of NaDC; The curcumin and TP can influence the shear viscosity, viscoelastic properties and phase transition temperature, even change the structure of liquid crystal. This supplies a way to adjust rheological properties, structure and even phase transition by altering those factors.     

Rheological Behavior of Titanium Dioxide Suspensions

The rheological properties of titanium dioxide dispersed in water are measured over a wide range of powder concentrations, temperatures, and pH values. The value of intrinsic viscosity of titanium dioxide measured with an Ubbelohde capillary viscometer is 3.55, which is useful for determining the shape and aggregation property of the particles. The yield stress and steady shear viscosity of titanium dioxide with broad and narrow particle size distributions were measured over a wide range of solid volume fractions on a Brabender rheometer. It is observed that the rheological properties of the suspensions are quite different due to the difference in particle size distributions. Quemada, Casson, and Zhou's models were used to fit the experimental data and useful parameters were obtained. Calculated data are also in good agreement with the experimental data. As expected, the shear viscosity and yield stress decrease with increasing temperature. But when the temperature is around 50 degrees C, yield stress increases with increasing temperature while shear viscosity exhibits a complex behavior. The phenomena are very interesting and special. The Peclet number was used to analyze the shear thickening behavior. Models were also used to describe the shear viscosity under different temperatures and the master plots of the reduced variables eta/eta(infinity) vs t(c)gamma; at different temperatures are superimposed, which means the agreement is fair and the models are suitable to describe the rheological properties of titanium dioxide suspensions. pH effects were investigated on a Rheometrics RFS-II rheometer and it was found that pH can change the surface charge of the particles, which also affects the rheological behavior. The pH at which maximum shear viscosity and yield stress occur is in concordance with the isoelectric point. Copyright 2001 Academic Press.     

FLOW PROPERTIES OF WEATHERED CRUDE OILS AND THEIR EMULSIONS

The present paper proposes the emulsification of weathered crude oils in water as a competitive and cost effective method for reducing their viscosities. Weathered crude oil samples were collected from major Kuwaiti oil lakes. Emulsion preparation involved using, either a nonionic surfactant or alkali, as well as both alkali and fatty acid. The obtained emulsions were characterized by measuring the droplet size distribution of the dispersed phase using optical microscopy. Emulsion stability was also examined in terms of the system breakdown. The rheological properties were measured using a concentric cylinder rotary rheometer. The emulsion rheological behavior has been studied as a function of composition, temperature, and shear rate. A constitutive model was developed to characterize the pseudoplastic behavior of the crude oil and the emulsion systems. The model fitted well the experimental results with a correlation coefficient higher than 95%. Associated with the pseudoplastic behavior, viscoelastic behavior has been observed with emulsions and some oils at high shear rates.

The results of this investigation indicated that the examined weathered crude oils can be transported through pipelines as emulsions of up to 80 vol.% oil concentrations. The proposed method of treatment with NaOH and oleic acid offers several advantages over the surfactant treatment. It exhibited comparable rheological behavior at lower cost and less mixing energy. It also provided higher emulsion stability, which favors oil transportation for longer distances.     

含氰基离子液体的合成、表征及流变性质研究

摘要合成、 表征了一系列新的含氰基咪唑类离子液体. 测定了该离子液体的密度、 熔点及溶解性等物理性质, 研究了其在稳态、 瞬态和动态条件下的流变行为. 结果表明, 当剪切速率在0.1～50 s^-1范围内时, 其粘度不随剪切速率的变化而变化, 但随温度升高而降低, 粘流活化能随取代基长度变化呈现规律性变化. 对于1-丁基-3-氰乙基咪唑六氟磷酸盐离子液体, 维持剪切速率不变时, 其剪切应力和粘度均不随时间变化, 且随着温度的升高而降低; 在动态条件下, 在线性粘弹区, 复合粘度和损耗模量G″ 随温度升高而降低. 关键词     

Slurries and emulsions of waxy and heavy crude oils for pipeline transportation of crude oil

The high viscosity of many asphaltic crude oils and the high pour points of many waxy crude oils present significant problems in their transportation over long distances by pipeline and tanker. While heating the oils and insulating the pipelines will help alleviate the problem, there is danger associated with an extended shutdown of flow and either congealing or solidification of the oil. A possible solution which we have studied in the laboratory is the emulsification or dispersion of the oil in water or brine so that shear takes place in the continuous aqueous phase rather than the oil droplets or particles.Synthetic waxy crude oils were prepared by dissolving paraffin wax in white mineral oil at slightly elevated temperatures and then measuring the pour point. One containing 30% wax had a pour point of 43°C and was selected for preparations of the dispersions. This was emulsified in water at a temperature higher than the pour point by using a suitable surfactant as an emulsifying agent. Rheological properties were measured at various temperatures and are reported in the paper. The method shows great promise for use in countries such as China which produce significant quantities of waxy crude oil and have seasonal temperatures significantly lower than the pour point of the crude oil.     

Structural effect of linear and star‐shaped poly(L‐lactic acid) on physical properties

The linear and star‐shaped poly(L‐lactic acid) (PLLA) with similar molecular weight were prepared and their physical properties such as thermal properties, rheological properties, and crystallization behavior in quiescent and dynamic states were compared. The differential scanning calorimetry showed that the linear PLLA gave higher glass transition, melting, and crystallization temperatures than the star‐shaped one. In dynamic crystallization, the linear PLLA gave longer induction time and longer overall crystallization time than the star‐shaped one, although the former gave higher rate of crystallization in quiescent crystallization. However, wide‐angle X‐ray diffractometer(WAXD) analysis revealed that the linear and star‐shaped PLLA developed the same crystal structure and application of shear had little effect on crystal structure. As predicted, the linear PLLA gave higher crystallinity than the star‐shaped PLLA. In the dilute solutions, the linear PLLA exhibited higher intrinsic viscosity than the star‐shaped one. In the concentrated solutions, the star‐shaped PLLA gave higher values of dynamic viscosity, storage, and loss moduli than the linear one. Further, the former exhibited more noticeable shear thinning behavior and greater dependence of rheological properties on temperature than the latter. For both PLLA melts, the modified Cole–Cole plot gave slope less than 2. Of two PLLA polymers the star‐shaped PLLA gave smaller slope than the linear one. In addition, the former showed greater change of the slope with temperature than the latter. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 939–946, 2004