Thermal Dissociation of Molten KHSO4: Temperature Dependence of Raman Spectra and Thermodynamics

详细信息    查看全文

• 作者：Christian B. Knudsen ; Angelos G. Kalampounias ; Rasmus Fehrmann ; Soghomon Boghosian
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：September 25, 2008
• 年：2008
• 卷：112
• 期：38
• 页码：11996-12000
• 全文大小：179K
• 年卷期：v.112,no.38(September 25, 2008)
• ISSN：1520-5207

文摘

Raman spectroscopy is used to study the thermal dissociation of molten KHSO₄ at temperatures of 240−450 °C under static equilibrium conditions. Raman spectra obtained at 10 different temperatures for the molten phase and for the vapors thereof exhibit vibrational wavenumbers and relative band intensities inferring the occurrence of the temperature-dependent dissociation equilibrium 2HSO₄⁻(l) ↔ S₂O₇²⁻(l) + H₂O(g). The Raman data are adequate for determining the partial pressures of H₂O in the gas phase above the molten mixtures. A formalism for correlating relative Raman band intensities with the stoichiometric coefficients, the equilibrium constant, and the thermodynamics of the reaction equilibrium is derived. The method is usedalong with the temperature-dependent features of the Raman spectrato show that the studied equilibrium 2HSO₄⁻(l) ↔ S₂O₇²⁻(l) + H₂O(g) is the only process taking place to a significant extent in the temperature range of the investigation and for determining its enthalpy to be ΔH° = 64.9 ± 2.9 kJ mol⁻¹. The importance of these findings for the understanding of the performance of the industrially important sulfuric acid catalyst under “wet” conditions is briefly addressed.