A molecular understanding of the phase-behavior of thiophene in the ionic liquid [C₄mim]⁺[BF₄]^{∿/sup> for extraction from petroleum streams}

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• 作者：Osmair V. Oliveira^a ; Andrew S. Paluch^b ; Luciano T. Costa^c ; ^{ltcosta@id.uff.br" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Desulfurization ; Thiophene extraction ; Ionic liquid ; Molecular dynamics
• 刊名：Fuel
• 出版年：2016
• 出版时间：1 July 2016
• 年：2016
• 卷：175
• 期：Complete
• 页码：225-231
• 全文大小：1003 K

文摘

Sulfur compounds are an important contaminant in the combustion process and are responsible for many environmental and human health problems. In response, world-wide environmental regulations on sulfur limits are increasing significantly and efforts to find new efficient extraction solvents has become a top priority. Following this trend, molecular dynamics simulations were carried out to study the desulfurization process in n-dodecane (a diesel fuel model) using the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate and the model sulfur compound thiophene. The main goal of this work was to identify/clarify the mechanism involved in the extraction of thiophene from diesel fuel using an IL. The radial distribution function (RDF) shows that thiophene interacts preferentially with the cation ring. This interaction was identified as a strong pi–pi interaction using spatial distribution function (SDF) analysis and confirmed using a QTAIM approach. In general, the presence of thiophene molecules does not alter the IL structure. The equilibrium solubility of thiophene predicted in the IL was 45 times greater than in n-dodecane. Moreover, the solvation process of thiophene in the IL relative to n-dodecane is enthalpically driven due to the strong cation–thiophene pi–pi interaction as suggested by the SDF analysis. Overall, our results indicate that the mechanism of the desulfurization process of thiophene in the IL is attributed mainly to pi–pi interactions between the cation ring and thiophene, and is not due to interactions with the cation alkyl chain as previously suggested in the literature.