Mixed Micelles of Tetrameric Acids and Naphthenic Acids in Water

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• 作者：Kenneth D. Knudsen ; S茅bastien Simon ; Lilia Qassym ; Bicheng Gao ; Johan Sj枚blom
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：July 17, 2014
• 年：2014
• 卷：28
• 期：7
• 页码：4469-4479
• 全文大小：695K
• ISSN：1520-5029

文摘

This article presents a characterization of the structures formed in aqueous solution by a mixture of carboxylic acid and a tetrameric acid molecule: either C₈₀-tetraacid (also known as ARN), which is an aliphatic molecule present in crude oil and responsible for the formation of deposits, or BP-10, a molecule designed to mimic the properties of the C₈₀-tetraacid. These molecules have four carboxylic functions at the end of four interconnected hydrocarbon chains and can be dissolved in aqueous solution in basic media. The structures have been analyzed by dynamic light scattering (DLS) and small-angle neutron scattering (SANS) techniques. It has previously been shown from SANS measurements that BP-10 in sodium form (Na₄BP-10) self-associate in solution to form nanosized micelles. We show here that sodium carboxylates, when present, can be incorporated into the BP-10 micelles. This incorporation is a function of the CMC of the sodium carboxylates. In contrast, the other tetrameric acid鈥擟₈₀-TA in sodium form鈥攕elf-associates to form very large aggregates in pure water and 20 mM NaCl. The extent of aggregation is influenced by the presence of sodium carboxylates, but depending strongly on their composition. When sodium oleate is added, the size of the aggregates decreases, most likely by a peptization mechanism. An opposite trend is observed in the presence of sodium decanoate, for which the aggregates grow in size. Finally, since sodium oleate can stabilize and disperse C₈₀-TA aggregates, we have investigated its effect on a real system: a calcium naphthenate deposit. It must be noticed that compared to the previous experiments, the deposit also contains calcium. The results show clearly that carboxylic acids are able to disperse calcium naphthenate deposits and that the effect is consistent with the previous experiments; i.e., sodium oleate is more efficient than sodium decanoate.