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Relaxation Dynamics of Ethanol and N-Butanol in Diesel Fuel Blends from Terahertz Spectroscopy
Journal of Infrared Millimeter and Terahertz Waves ( IF 2.9 ) Pub Date : 2021-08-30 , DOI: 10.1007/s10762-021-00807-5
Rayda Patiño-Camino 1 , Alexis Cova-Bonillo 1 , José Rodríguez-Fernández 1 , Magín Lapuerta 1 , Teresa P. Iglesias 2
Affiliation  

Binary blends of ethanol-diesel, n-butanol-diesel, ethanol-biodiesel, and n-butanol-biodiesel have been analyzed with terahertz time-domain spectroscopy in a full range of concentrations and at room temperature. The real and imaginary parts of the complex dielectric constant of the blends were obtained from the spectra and fitted to the Debye model at low volume concentrations (up to 7.5% for ethanol in diesel and up to 20% for butanol in diesel, ethanol in biodiesel, and butanol in biodiesel blends), considering the number of relaxation processes recommended in the literature for each pure component (single for diesel, double for biodiesel, and triple for alcohols). The results indicate that the faster relaxation time in low alcohol mixtures is longer than in pure alcohols. This relaxation time increases as the alcohol content increases. The excess of the real and of imaginary parts of the dielectric constant were individually determined. The analysis of such excess and of its different contributions (volume, contrast, and interactions) suggests that the intermolecular interactions between the different components of the blends dominate the relaxation dynamics in each pseudo-binary system. Ethanol was found to move blends further away from ideal behavior than n-butanol. In fact, these latter blends showed the most ideal behavior, suggesting that the length of the alcohol carbon chain plays an important role. This information allows a possible link between the nonlinear behavior of the physicochemical properties of the blends (e.g., viscosity and surface tension) and the molecular interactions between their constituent molecules. This relation could have direct application for monitoring the fuel composition and quality in the vehicle control systems.



中文翻译:

从太赫兹光谱看乙醇和正丁醇在柴油燃料混合物中的弛豫动力学

乙醇-柴油、正丁醇-柴油、乙醇-生物柴油和正丁醇-生物柴油的二元混合物已使用太赫兹时域光谱在全浓度范围和室温下进行了分析。混合物的复介电常数的实部和虚部从光谱中获得,并在低体积浓度下拟合到德拜模型(柴油中的乙醇高达 7.5%,柴油中的丁醇高达 20%,生物柴油中的乙醇)和生物柴油混合物中的丁醇),考虑文献中为每种纯组分推荐的松弛过程的数量(柴油为单一,生物柴油为两倍,醇为三倍)。结果表明,在低度酒精混合物中更快的弛豫时间比在纯醇中更长。这种松弛时间随着酒精含量的增加而增加。介电常数的实部和虚部的过量分别被确定。对这种过量及其不同贡献(体积、对比度和相互作用)的分析表明,混合物不同组分之间的分子间相互作用主导了每个伪二元系统中的弛豫动力学。发现乙醇比正丁醇更远离理想行为。事实上,后一种混合物表现出最理想的行为,表明醇碳链的长度起着重要作用。该信息允许在混合物的物理化学性质(例如,粘度和表面张力)的非线性行为与其组成分子之间的分子相互作用之间存在可能的联系。

更新日期:2021-08-30
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