Reaction Reversibility in α-Pinene Thermal Isomerization: Improving the Kinetic Model
Russian Journal of Physical Chemistry A
, E-ISSN: 1531-863X
||chemical equilibrium, identification of kinetic parameters, monoterpenes, Supercritical fluid, thermal isomerization, thermochemical data
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090 Russia
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Revision of the experimental data on α-pinene thermal isomerization attained in supercritical ethanol allowed us to expand the reaction scheme, which includes now six main products and eleven reversible reactions. The equilibrium constants of every reaction (K T, j and K Φ, j) were calculated to allow for reversibility of reactions. The thermochemical data of the pure compounds required to calculate constants K T, j and K Φ, j (standard enthalpy and entropy of formation Δf H° (298.15 K), Δf S° (298.15 K), heat capacity C p (T), critical parameters T cr and p cr, boiling point T b, and the acentric factor ω) were preliminary estimated using the empirical Joback and Benson methods. A kinetic model based on the new expanded scheme of reversible reactions was successfully identified and its kinetic parameters k j (600 K) and E j were determined. Detailed examination of the new kinetic model allowed us to refine the generally accepted mechanism of α-pinene thermal isomerization and to distinguish additional features of the multistep process.