Stability of oil/water interfaces
Abstract/Contents
- Abstract
- The stability of oil/water interfaces affects the manufacture of many different products in industries ranging from pharmaceuticals to oil industry. In the first part of the talk, the stability of asphaltene-laden interfaces will be discussed. Asphaltene molecules are complex molecules from crude oil that are defined by their solubility in hydrocarbons. These molecules have the propensity to adsorb onto oil/water interfaces where they create a viscoelastic network and stabilize oil/water emulsions. This causes difficulties, for instance, in the desalting process, one of the first processes in an oil refinery. During the desalting process, high concentrations of salt in crude oil are reduced by a liquid-liquid extraction where crude oil is mixed with water. Then, this mixture is brought to a settling tank called desalter where the two phases are expected to separate. However, the presence of asphaltenes may negatively impact this separation process as they stabilize oil/water emulsions. We built an experimental setup in the Fuller laboratory to reproduce in a smaller scale and in a controlled way the separation process that occurs in a desalter. Our goal was to study the impact of asphaltenes on the coalescence of both water and oil drops against a flat oil/water interface. We found that water drops are more stable than oil drops upon coalescence. In addition, the time it takes for water drops to coalesce as a function of the aging time of the interface presents a maximum due to a spontaneous appearance of micron-sized droplets at the oil/water interface. This spontaneous appearance of droplets is a phenomenon known as spontaneous emulsification and, in our system, the majority of the droplets formed consist of asphaltene-laden water droplets. In the second part of the talk, the spontaneous emulsification phenomenon in the presence of asphaltenes will be discussed. We used a co-flow microfluidic device to study the shrinkage due to spontaneous emulsification of suspended water drops in asphaltene/heptane-toluene solutions. The initial size of water drops and the concentration of solvents used in the oil phase are varied in our study. We found that drops will only decrease in size in the presence of asphaltenes. In addition, we found that drops shrink faster as their initial drop size decreases. In fact, the drop's radius decreases linearly with time and the angular coefficient of this relationship is a strong function of the drop's initial size. Finally, we found that the internal pressure of asphaltene-coated water drops does not follow a simple Young-Laplace equation and its internal pressure is inversely proportional to the drop's initial surface area. The internal drop pressure was found to be a potential force for spontaneous emulsification. An understanding of the spontaneous emulsification phenomenon in the presence of asphaltenes has strong implications in the oil industry, as it may affect problems ranging from oil refining to oil spill cleanups.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2019; ©2019 |
| Publication date | 2019; 2019 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Bochner de Araujo, Simone |
|---|---|
| Degree supervisor | Fuller, Gerald G |
| Thesis advisor | Fuller, Gerald G |
| Thesis advisor | Qin, Jian, (Professor of Chemical Engineering) |
| Thesis advisor | Spakowitz, Andrew James |
| Degree committee member | Qin, Jian, (Professor of Chemical Engineering) |
| Degree committee member | Spakowitz, Andrew James |
| Associated with | Stanford University, Department of Chemical Engineering. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Simone Bochner de Araujo. |
|---|---|
| Note | Submitted to the Department of Chemical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2019 by Simone Bochner de Araujo
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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