Coarse-Grained Interface Surfactant Density Maps for Calculation of the Fractional Conversion of Tetrameric Carboxylic Acids to Calcium Naphthenate Precipitates
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- 作者：Aleksandar Y. Mehandzhiyski ; Brian A. Grimes
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2016
- 出版时间：May 4, 2016
- 年：2016
- 卷：55
- 期：17
- 页码：5090-5099
- 全文大小：718K
- 年卷期：0
- ISSN：1520-5045
文摘
Modeling molecular interactions on different length scales is often necessary and presents a significant challenge in chemical engineering. In the present study, we apply molecular dynamics (MD) simulations on different tetrameric carboxylic acid (TA) molecules absorbed at a water–oil interface, which tend to form a cross-linked network in the presence of calcium. From the MD simulations, we obtain various spatial probabilities describing the molecular geometries of TAs in the interfacial region. The MD-obtained probability distribution functions are then used to recreate a coarse-grained representation (interface map) of the interfacial density of the TA molecules. The interface maps are created by randomly placing molecules in an interfacial region and calculating the coordinates of the carboxylate groups according to the MD probability functions. By creating a large number of interface maps, we can obtain a better statistical representation of how the molecules are spatially arranged at the interface at different interfacial concentrations. The orientation and distance between the carboxylate groups from different TA molecules is important for the study of the formation of calcium naphthenate precipitates occurring in the petroleum industry. After an interface map has been built, we can assess how many molecules are cross-linked for a given interfacial concentration based on MD-calculated calcium carboxylate binding probabilities. Subsequently, we can obtain the fractional conversion [fp(ΓTA)] of tetrameric acids to cross-linked calcium naphthenate precipitates. The fractional conversion function can then be used in multiscale approaches for further elucidation of the phenomena of calcium naphthenate precipitation.