Department of Chemical Engineering, Yale University, New Haven, Connecticut 06510, USA.
J Phys Chem B. 2010 Dec 9;114(48):15780-8. doi: 10.1021/jp107548j. Epub 2010 Nov 11.
When oil is mixed with light alkanes, asphaltenes can precipitate out of oil solutions in a multistep process that involves the formation of nano and colloidal scale particles, the aggregation of asphaltene colloids, and their eventual sedimentation. Amphiphilic dispersants can greatly affect this process. The mechanism of the dispersant action in colloidal asphaltene suspensions in heptane has been shown through previous work to be due in part to a reduction in the size of the colloidal asphaltene particles with the addition of dispersant. However, previous studies of the sedimentation behavior revealed evidence of aggregation processes in the colloidal asphaltenes in heptane that has yet to be investigated fully. We investigate the effect of dispersants on this aggregation behavior through the use of dynamic light scattering, showing that both the amount of dispersant and the amount of heptane dilution can slow the onset of aggregation in colloidal asphaltene suspensions. An effective dispersant acts by suppressing colloidal aggregation in asphaltene suspensions, as shown by light scattering, and therefore also slows separation from the bulk, as revealed through macroscopic sedimentation experiments.
当油与轻烷混合时，沥青质可以通过多步过程从油溶液中沉淀出来，该过程涉及纳米和胶体尺度颗粒的形成、沥青质胶体的聚集以及它们最终的沉降。两亲分散剂可以极大地影响这个过程。通过之前的工作已经表明，分散剂在庚烷中胶体沥青质悬浮液中的作用机制部分归因于添加分散剂后胶体沥青质颗粒的尺寸减小。然而，以前对沉降行为的研究表明，在庚烷中的胶体沥青质中存在聚集过程，这一过程尚未得到充分研究。我们通过动态光散射研究了分散剂对这种聚集行为的影响，结果表明分散剂的用量和庚烷稀释量都可以减缓胶体沥青质悬浮液中聚集的开始。有效的分散剂通过抑制沥青质悬浮液中的胶体聚集来发挥作用，如光散射所示，因此也通过宏观沉降实验揭示了从主体中分离出来的速度减慢。
