新型磺基甜菜碱/聚丙烯酰胺体系表面及界面性能

采用自制的新型磺基甜菜碱两性表面活性剂与相对分子质量2500万的聚丙烯酰胺进行复配,考察了不同温度和矿化度条件下,聚合物对复配溶液表面、界面性能的影响。 采用滴体积法测定了溶液的表面张力,结果表明,加入聚合物使溶液的临界胶束浓度增大,且复配溶液的表面张力大于单独表面活性剂溶液的表面张力。 当聚合物浓度一定,增大溶液矿化度时,体系表面张力增大。 用旋滴型界面张力仪测定了溶液的界面张力,结果表明,增大聚合物浓度,油水界面张力增大,增大溶液矿化度,油水界面张力有所升高。 聚合物质量浓度为1.5 g/L,表面活性剂质量浓度为0.3 g/L时,可使胜利油田孤岛原油和孤东原油的油水界面张力达到超低数量级（10-3 mN/m）。 用分水时间法测定了溶液的乳化性能,结果表明,聚合物浓度增大,分水时间延长,并考察了75、85和95 ℃条件下体系的乳化性能,温度越高,分水时间越短。     

CTAB在硅胶表面吸附引起的润湿性变化和模拟驱油

用椭圆偏振法测定溴代十六烷基三甲胺（CTAB）水溶液在光滑的二氧化硅膜片上的吸附，其结果符合两阶段模型，即在不同浓度下发生单分子层和近似双分子层的吸附，并与其表面润湿性变化的数据吻合.用改进的Washburn方程测量改性硅胶粉末的润湿性, 研究了CTAB水溶液在硅胶粉末表面上吸附引起的润湿性变化.并由此探讨了CTAB水溶液在硅胶粉末表面的润湿性,表面活性剂的临界胶束浓度（CMC）与表面含油粉末脱油率的关系，对在非超低界面张力条件下通过改变固/液界面润湿性提高原油采收率作了实验探讨.     

餐厨废油制备的生物基两性表面活性剂的油水界面性能

以餐厨废油制备了生物基两性表面活性剂,应用界面张力和动态光散射方法,研究了该生物基两性表面活性剂体系的油水界面性能及在溶液中的聚集行为。 在无外加碱条件下,由餐厨废油制备的表面活性剂表现出良好的界面性能,在50~70 ℃以及pH值为7~12的条件下,均可以将油水界面张力降至超低值(<10^-3 mN/m),在不同的油藏模拟地层水中均保持较好的界面活性;分别在50、-20和4 ℃下保存,其界面活性均未受到明显影响。 在水溶液中形成的聚集体的平均流体力学半径为10~30 nm,无机盐离子的加入可使聚集体的粒径上升。 基于其优良的界面性质和可再生来源,由餐厨废油制备的生物基两性表面活性剂在三次采油方面具有重要的应用价值。     

甲烷在褐煤煤焦上的裂解反应研究

采用石英管固定床反应器,分别考察了不同温度（1123K、1173K、1223K、1273K）及不同浓度（10%、15%、20%）下,甲烷在褐煤煤焦上的裂解反应。结果表明,褐煤煤焦对甲烷裂解反应具有良好的催化活性,在所考察温度范围内,甲烷的初始转化率最高达99.5%,温度越高,甲烷的初始转化率越高;但随着反应的进行,转化率逐渐降低;甲烷进气浓度越高,初始转化率越低,而且催化剂失活也越快。反应前后煤焦电镜扫描照片及物性参数的比较表明,甲烷裂解生成炭沉积在煤焦表面,导致煤焦比表面积随反应的进行逐渐降低,与甲烷裂解转化率的变化趋势一致;反应后煤焦的孔容及微孔容都有所降低,平均孔径增大,说明甲烷的裂解生成炭造成了煤焦孔道尤其是微孔的堵塞,比表面积减小,导致了甲烷的转化率降低。     

超临界条件下甲烷在纳米活性炭表面的吸附机理

在273-373 K、0-10 MPa范围内测量了甲烷在纳米活性炭表面的吸附等温线和等量吸附热. 结果发现, 在实验涉及的温度范围内, 吸附平衡特性在低压下能够很好地遵循Dubinin-Astakhov (DA)微孔填充模型, 但是当压力超过特定范围时, 吸附等温线及等量吸附热测量数据都与DA模型计算结果发生了偏离, 吸附行为更接近单层定位吸附.文中参照Cerofolini对亚单层吸附提出的Freundlich-Dubinin-Radushkevich (FDR)混合模型, 对纳米活性炭在较高压力条件下的吸附使用通用Freundlich (GF)模型进行了修正, 从而提出了一种分段模型GFDA. 根据GFDA模型对甲烷在广泛的压力范围内在纳米活性炭表面的吸附机理进行了完整的解释, 并对纳米活性炭表面的能量非均匀性进行了分析.     

DTAB降低饱和烷烃与水的界面张力的研究

判断一种表面活性剂降低油-水界面张力性能的优劣,就需要对界面张力进行准确有效的测量。文章就不同浓度的十二烷基三甲基溴化铵(DTAB)水溶液分别与正庚烷(n-Heptane)和正十六烷(n-Hexadecane)之间的界面张力进行定量的测量,分别得到了在30℃下水-正庚烷和水-正十六烷体系的界面张力随DTAB浓度变化的曲线。结果表明,在DTAB浓度达到其所在体系中的CMC值时,水-正庚烷体系界面张力小于水-十六烷体系界面张力。DTAB具有较强的抗矿盐能力,界面张力随温度升高有所下降。     

氧化铝自配合溶液中吸附Zn^2^+及SCN^-的初探

研究了在不同PH、浓度、时间、温度、离子强度和螯合剂的条件下, 用不同浓度的硝酸预处理的氧化铝吸附剂自锌(II)-硫氰酸根配合水溶液中吸附Zn^2^+及SCN^-的特性, 并与自简单锌盐、硫氰酸盐水溶液中的吸附特性相比较, 结果表明配合物体系中的吸附作用不同于非配合物体系, 除了主要以离子交换机理进行外, 还可能在氧化物/水界面上发生配位吸附作用。     

阴阳离子表面活性剂体系超低油水界面张力的应用

通过阴阳离子表面活性剂复配,在实际油水体系中获得了超低界面张力.通过在阴离子表面活性剂分子结构中加入乙氧基(EO)链段,以及采用阴阳离子加非离子型表面活性剂的三组分策略,有效解决了混合表面活性剂在水溶液中溶解度问题.进而研究了阳离子表面活性剂结构、非离子表面活性剂结构、三者组分配比、表面活性剂总浓度等因素对油水界面张力的影响,从而在胜利油田多个实际油水体系中获得了较大比例范围和较低浓度区域的油水超低界面张力,部分体系甚至达到了10-4 mN·m-1.由于阴阳离子表面活性剂间强烈的静电吸引作用,相关体系具有很好的抗吸附能力.经过石英砂48 h吸附后,体系仍然具有很好的超低界面张力.     

表面活性剂与油相动态界面张力影响因素研究

对不同类型表面活性剂烷基糖苷(APG1214)、咪唑啉(IAS)、十二烷基苯磺酸钠(SDBS)、烷基酚醚羧酸盐(ss-231)的油水动态界面张力进行了研究。在60℃,5 000 r·min-1条件下,考察了表面活性剂的浓度、表面活性剂的结构、正构烷烃碳数以及原油中活性物质对形成低界面张力影响。实验结果表明:表面活性剂亲水基的亲水性越强,亲水基之间排斥力越小,使得在油水界面排布的密度越大,降低界面张力的效果会更好;当表面活性剂疏水碳链与烷烃碳链相似时,降低界面张力的效果会更明显;无碱体系中原油中的活性物质可在油水界面上形成粘弹性界面膜,这种界面膜的形成减少了表面活性剂分子在界面的吸附,使界面张力升高。     

甲烷在石墨化热解碳黑和活性炭上的吸附

为研究影响碳基吸附剂吸附超临界温度气体的主要因素,选择石墨化热解碳黑BP280和Ajax活性炭,分析超临界温度高压甲烷在其上的吸附平衡。应用容积法,在压力0~20.5 MPa、温度253 K~313 K测定甲烷的吸附平衡数据,并由等量吸附线标绘和亨利定律常数确定等量吸附热。引入通用吸附等温方程,再由方程的Langmuir标绘确定最大吸附容量,进而通过方程的线性化计算吸附平衡态中甲烷分子的作用能。结果表明,甲烷在两种吸附剂上的最大吸附容量均随温度而变化,并都小于液态甲烷的密度;甲烷在碳黑和活性炭上的等量吸附热分别为11.9 kJ/mol~12.5 kJ/mol和17.5 kJ/mol~22.5 kJ/mol,体现了两种吸附剂不同的表面能量分布;甲烷分子间作用能随吸附量的变化特点反映了超临界温度甲烷以类似于压缩气体状态聚集的特点和吸附剂结构上的差异。碳基吸附剂的比表面积和微孔容积是影响其储存甲烷容量的重要因素。     

Thermodynamic properties of methane/water interface predicted by molecular dynamics simulations

Molecular dynamics simulations have been performed to examine the thermodynamic properties of methane/water interface using two different water models, the TIP4P/2005 and SPC/E, and two sets of combining rules. The density profiles, interfacial tensions, surface excesses, surface pressures, and coexisting densities are calculated over a wide range of pressure conditions. The TIP4P/2005 water model was used, with an optimized combining rule between water and methane fit to the solubility, to provide good predictions of interfacial properties. The use of the infinite dilution approximation to calculate the surface excesses from the interfacial tensions is examined comparing the surface pressures obtained by different approaches. It is shown that both the change of methane solubilities in pressure and position of maximum methane density profile at the interface are independent of pressure up to about 2 MPa. We have also calculated the adsorption enthalpies and entropies to describe the temperature dependency of the adsorption.     

Adsorption of n-alkane vapours at the water surface

Monte Carlo simulations are reported here to predict the surface tension of the liquid-vapour interface of water upon adsorption of alkane vapours (methane to hexane). A decrease of the surface tension has been established from n-pentane. A correlation has been evidenced between the decrease of the surface tension and the absence of specific arrangement at the water surface for n-pentane and n-hexane. The thermodynamic stability of the adsorption layer and the absence of film for longer alkanes have been checked through the calculation of a potential of mean force. This complements the work recently published [Ghoufi et al., Phys. Chem. Chem. Phys., 2010, 12, 5203] concerning the adsorption of methane at the water surface. The decrease of the surface tension has been interpreted in terms of the degree of hydrogen bonding of water molecules at the liquid-vapour interface upon adsorption.     

Micellization and Adsorption Parameters of Poly(Propylene Oxide)/Poly(Ethylene Glycol) Block and Graft Copolymers in Aqueous Medium

This work aims to measure the adsorption and micellization parameters of new water soluble nonionic amphiphilic block and graft copolymers based on hydrophilic poly (ethylene glycol) (PEG) and hydrophobic poly (propylene oxide) (PPO) at ambient temperature and normal atmospheric pressure. The chemical composition and molecular weights of the prepared copolymers were determined from ¹H NMR analyses. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The surface tension, critical micelle concentration, and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration, the area per molecule at interface and the effectiveness of surface tension reduction were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption and micellization process were calculated and are discussed.     

Effect of volume concentration and temperature on viscosity and surface tension of graphene–water nanofluid for heat transfer applications

In the present study, the effect of volume concentration (0.05, 0.1 and 0.15 %) and temperature (10–90 °C) on viscosity and surface tension of graphene–water nanofluid has been experimentally measured. The sodium dodecyl benzene sulfonate is used as the surfactant for stable suspension of graphene. The results showed that the viscosity of graphene–water nanofluid increases with an increase in the volume concentration of nanoparticles and decreases with an increase in temperature. An average enhancement of 47.12 % in viscosity has been noted for 0.15 % volume concentration of graphene at 50 °C. The enhancement of the viscosity of the nanofluid at higher volume concentration is due to the higher shear rate. In contrast, the surface tension of the graphene–water nanofluid decreases with an increase in both volume concentration and temperature. A decrement of 18.7 % in surface tension has been noted for the same volume concentration and temperature. The surface tension reduction in nanofluid at higher volume concentrations is due to the adsorption of nanoparticles at the liquid–gas interface because of hydrophobic nature of graphene; and at higher temperatures, is due to the weakening of molecular attractions between fluid molecules and nanoparticles. The viscosity and surface tension showed stronger dependency on volume concentration than temperature. Based on the calculated effectiveness of graphene–water nanofluids, it is suggested that the graphene–water nanofluid is preferable as the better coolant for the real-time heat transfer applications.     

Adsorption and Aggregation Properties of Some Polysorbates at Different Temperatures

Measurements of the surface tension of aqueous solutions of polysorbates (Tween 20, Tween 60 and Tween 80) at 293, 303 and 313 K were made. On the basis of the obtained results the Gibbs surface excess concentration of the Tweens at the water–air interface and critical micelle concentrations were determined. Knowing the Gibbs surface excess concentration and taking into account the difference between the limiting area occupied by water and Tween molecules at the water–air interface, the fraction occupied by Tween molecules was established. The limiting area occupied by the Tween molecule was calculated by applying the Joos equation. The area determined in such a way was confirmed by the calculations of cross section of Tween molecules based on the bond lengths and the angles between them as well as the average distance between the molecules, taking into account their different conformations. This area was used for calculation of the standard Gibbs energy of adsorption using the Langmuir equation. The standard Gibbs energy of Tweens adsorption at the water–air interface was also calculated from the hydrophobic part of Tween molecule–water interface tension and that of hydrophobic part. Using the determined values of standard Gibbs energy of adsorption at different temperatures, the standard enthalpy and entropy values were deduced. The standard thermodynamic functions of micellization were also determined and compared to the Gibbs energy of Tween molecules interactions through the water phase.     

Adsorption of dioctyldimethylammonium chloride at water/hexane interface

The adsorption behavior of dioctyldimethylammonium chloride at water/ hexane interface has been studied by measuring the interfacial tension as a function of temperature and pressure at various bulk concentrations. By applying the thermodynamics of adsorption at interfaces to the experimental results, the thermodynamic quantity changes associated with adsorption and the interfacial density of dioctyldimethylammonium chloride have been evaluated.The interfacial tension vs temperature and concentration curves have shown the breaks and it has been concluded that the first order phase transition takes place between a gaseous and an expanded state. The entropy and volume changes associated with adsorption have shown the remarkable dependence on temperature and pressure and have been found to decrease with increasing the molality. Also the energy change associated with adsorption has been evaluated and it has been concluded that the adsorption of dioctyldimethylammonium chloride at water/hexane interface is enhanced by negative values of the partial molar energy change. Further, all the thermodynamic quantities have been characterized by the discontinuous change attributable to the phase transition.     

Effect of temperature on the density and surface tension of aqueous solutions of HMT

In this study, a systematic study of the effect of the temperature on the density and surface tension of HMT (hexamethylentetramine) in water was developed. The density and surface tension were determined at temperatures of 288.15, 293.15, 298.15, 303.15, and 308.15 K. Precise data of surface tension have not been reported previously in literature. From the density measurements, the apparent molar and partial molar volumes were calculated. The apparent molar volume decreases with concentration, the molar partial volume increases with temperature. The surface tension of the aqueous solutions of HMT decreases with concentration. The excess surface concentration was calculated, the values increase with concentration, indicating that the amount of HMT that goes to the interface gas liquid increases at higher concentrations of HMT.     

CTAB水溶液表面的吸附动力学

用最大气泡压力法测定了十六烷基三甲基溴化铵(CTAB)水溶液的动态表面张力,研究了CTAB水溶液表面吸附的动力学及其影响因素。结果表明,吸附过程由初始的扩散控制经混合控制过渡到势垒控制。扩散控制吸附速率快,时间短;势垒控制速率慢,时间长,吸附势垒一般为4～10kJ.mol^-^1。温度升高,动态表面张力减小,但吸附机理不变;无机盐或醇类的加入对势垒值影响不大,但对扩散控制步骤的影响较大。     

Methane dissociative adsorption on the Pt(111) surface over the 300-500 K temperature and 1-10 Torr pressure ranges

The dissociative adsorption of methane on the Pt(111) surface has been investigated and characterized over the 1-10 Torr pressure and 300-500 K temperature ranges using sum frequency generation (SFG) vibrational spectroscopy and Auger electron spectroscopy (AES). At a reaction temperature of 300 K and a pressure of 1 Torr, C-H bond dissociation occurs in methane on the Pt(111) surface to produce adsorbed methyl (CH(3)) groups, carbon, and hydrogen. SFG results suggest that C-C coupling occurs at higher reaction temperatures and pressures. At 400 K, methyl groups react with adsorbed C to form ethylidyne (C(2)H(3)), which dehydrogenates at 500 K to form ethynyl (C(2)H) and methylidyne (CH) species, as shown by SFG. By 600 K, all of the ethylidyne has reacted to form the dissociation products ethynyl and methylidyne. Calculated C-H bond dissociation probabilities for methane, determined by carbon deposition measured by AES, are in the 10(-8) range and increase with increasing reaction temperature. A mechanism has been developed and is compared with conclusions from other experimental and theoretical studies using single crystals.     

甲烷在活性炭上吸附平衡模型的研究

比较吸附模型分析甲烷在活性炭上吸附平衡的适用性,为吸附式天然气(ANG)的工程应用提供准确的预测模型。基于在温度268.15～338.15 K、压力0～12.5 MPa测试的甲烷在Ajax活性炭上的吸附平衡数据,选择Langmuir、Langmuir-Freundlich和Toth方程,应用非线性回归拟合方程参数后,确定绝对吸附量和甲烷吸附相态,并比较方程在不同压力区域内的预测精度。结果表明,甲烷吸附相密度随平衡温度和压力变化;由绝对吸附量确定的甲烷在Ajax活性炭上的平均等量吸附热为15.72 kJ/mol,小于由过剩吸附量的标绘结果;Langmuir、Langmuir-Freundlich和Toth方程预测结果在0～0.025 MPa的累积相对误差为6.449 8%、7.918 4%和0.910 0%,在1～10 MPa为0.491 1%、0.161 3%和0.369 4%。Toth方程在整个压力范围内的预测结果最为准确,但Langmuir-Freundlich方程在较高压力区域内具有较高的预测精度。