Sztukowski Danuta M, Jafari Maryam, Alboudwarej Hussein, Yarranton Harvey W
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB, T2N 1N4, Canada.
J Colloid Interface Sci. 2003 Sep 1;265(1):179-86. doi: 10.1016/s0021-9797(03)00189-9.
The configuration of asphaltenes on the water-oil interface was evaluated from a combination of molar mass, interfacial tension, drop size distribution, and gravimetric measurements of model emulsions consisting of asphaltenes, toluene, heptane, and water. Molar mass measurements were required because asphaltenes self-associate and the level of self-association varies with asphaltene concentration, the resin content, solvent type, and temperature. Plots of interfacial tension versus the log of asphaltene molar concentration were employed to determine the average interfacial area of asphaltene molecules on the interface. The moles of asphaltenes per area of emulsion interface were determined from the molar mass data as well as drop size distributions and gravimetric measurements of the model emulsions. The results indicate that asphaltenes form monolayers on the interface even at concentrations as high as 40 kg/m(3). As well, large aggregates with molar masses exceeding approximately 10,000 g/mol did not appear to adsorb at the interface. The area occupied by the asphaltenes on the interface was constant indicating that self-associated asphaltenes simply extend further into the continuous phase than nonassociated asphaltenes. The thickness of the monolayer ranged from 2 to 9 nm.
通过对由沥青质、甲苯、庚烷和水组成的模型乳液进行摩尔质量、界面张力、液滴尺寸分布和重量测量等综合分析，评估了水 - 油界面上沥青质的形态。之所以需要进行摩尔质量测量，是因为沥青质会发生自缔合，且自缔合程度会随沥青质浓度、树脂含量、溶剂类型和温度而变化。利用界面张力与沥青质摩尔浓度对数的关系图来确定界面上沥青质分子的平均界面面积。根据模型乳液的摩尔质量数据以及液滴尺寸分布和重量测量结果，确定了乳液界面每单位面积上沥青质的摩尔数。结果表明，即使在浓度高达40 kg/m³时，沥青质仍在界面上形成单分子层。此外，摩尔质量超过约10,000 g/mol的大聚集体似乎并未吸附在界面上。沥青质在界面上所占的面积是恒定的，这表明自缔合的沥青质比未缔合的沥青质只是在连续相中延伸得更远。单分子层的厚度范围为2至9纳米。
