Insight into the Local Composition of the Wilson Equation at High Temperatures and Pressures through Molecular Simulations of Methanol鈥揥ater Mixtures

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• 作者：Takumi Ono ; Kyouhei Horikawa ; Masaki Ota ; Yoshiyuki Sato ; Hiroshi Inomata
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2014
• 出版时间：April 10, 2014
• 年：2014
• 卷：59
• 期：4
• 页码：1024-1030
• 全文大小：385K
• 年卷期：v.59,no.4(April 10, 2014)
• ISSN：1520-5134

文摘

Methanol鈥搘ater mixtures are known to be microscopically inhomogeneous and show nonideal properties at ambient conditions and also at higher temperatures and pressures. To understand the nonideality of methanol鈥搘ater mixtures, the behaviors of local compositions were studied through evaluating the local mole fractions by the well-known activity coefficient equation, Wilson equation, and by molecular dynamics (MD) simulation at three conditions: 25 掳C鈥?.1 MPa, 300 掳C鈥?5 MPa, and 350 掳C鈥?5 MPa. The Wilson parameters were redetermined to generate the reference values for the comparison in this study. The deviation of local mole fraction from bulk mole fraction was selected as an indicator for local composition. The deviations by the Wilson equation were positive in all compositions, and its magnitude for water was much larger than that for methanol, which is principally independent of temperature and pressure and was completely supported by the results by MD simulation. The MD simulation provided the dependence of the local mole fraction deviation on the intermolecular distance and indicated that the immediate neighbor in the Wilson local mole fraction approximately corresponds to the distance range from first valley to second peak in the radial distribution function. In addition, the general trends of local mole fraction by MD simulation are similar at ambient and high temperature and pressure conditions, suggesting the applicability of the Wilson equation for methanol鈥搘ater mixture to high temperature and pressure conditions in terms of representing the local mole fraction.