Ma Junchi, Haider Olivia M, Chang Chih-Cheng, Grzesiak Kathryn A, Squires Todd M, Walker Lynn M
Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States.
Langmuir. 2023 Oct 20;39(43):15238-48. doi: 10.1021/acs.langmuir.3c01890.
The formation of highly stable water-in-oil emulsions results in complications in both upstream and downstream processing. Emulsion stability in these systems has been connected to the adsorption of surface-active asphaltenes that are assumed to form a rigidified film at the oil/water (o/w) interface. Full characterization of this behavior is needed to allow for engineered solutions for enhanced oil recovery. Interfacial properties, such as surface pressure and interfacial elasticity, are implicated in the stabilizing mechanism for these observed films. Asphaltenes are known to be interfacially active in both good solvents (aromatics) and poor solvents (high ratio of aliphatic to aromatic). However, due to inherent complexities present in asphaltene studies, the details of the mechanical properties of the interface remain poorly understood. Despite the widely accepted perception that asphaltenes form persistent rigid films at fluid-fluid interfaces, the connection between bulk solution properties and interfacial mechanics has not been resolved. Here, the effects of solvent quality on the interfacial properties of asphaltene dispersions are determined by using a well-defined asphaltene/solvent system. Interfacial rigidity is observed only under poor solvent conditions, while the good solvent system remains fluid-like. The interfacial rheology under good and poor solvent conditions is measured simultaneously with surface pressure measurements to track interfacial development. It is shown that surface pressure and dilatational modulus measurements are not indicators of whether an interface demonstrates rigid behavior under large compressions. Finally, conditions required for asphaltene-coated interfaces to exhibit the mechanical behavior associated with a rigidified interface are defined. This work provides a framework for quantifying the impact of the aggregation state of asphaltenes on the stability and mechanics at the o/w interface.
高度稳定的油包水乳液的形成会在上游和下游加工过程中引发复杂问题。这些体系中的乳液稳定性与表面活性沥青质的吸附有关，人们认为沥青质会在油/水（o/w）界面形成刚性膜。需要对这种行为进行全面表征，以便找到提高采收率的工程解决方案。界面性质，如表面压力和界面弹性，与这些观察到的膜的稳定机制有关。已知沥青质在良溶剂（芳烃）和不良溶剂（脂肪族与芳烃的高比例）中都具有界面活性。然而，由于沥青质研究中存在固有的复杂性，界面力学性能的细节仍知之甚少。尽管人们普遍认为沥青质会在流体-流体界面形成持久的刚性膜，但本体溶液性质与界面力学之间的联系尚未得到解决。在此，通过使用定义明确的沥青质/溶剂体系来确定溶剂性质对沥青质分散体界面性质的影响。仅在不良溶剂条件下观察到界面刚性，而良溶剂体系仍呈流体状。在测量表面压力的同时测量良溶剂和不良溶剂条件下的界面流变学，以跟踪界面发展。结果表明，表面压力和拉伸模量测量并不能表明界面在大压缩下是否表现出刚性行为。最后，定义了沥青质包覆界面表现出与刚性界面相关的力学行为所需的条件。这项工作为量化沥青质聚集状态对o/w界面稳定性和力学性能的影响提供了一个框架。
