Thermodynamic Analysis on Isomerization of n-Pentane to Isopentane
The thermodynamic behaviors of n-pentane isomerization to isopentane were systematically analyzed using SRK equation, and thermodynamic data, phase state, equilibrium composition and equilibrium isomerization ratio of n-pentane under different reaction conditions were calculated. The results show that the reaction is exothermic and decreasing the reaction temperature favors the increasing of equilibrium isomerization ratio of n-pentane. When the reaction temperature is high (e.g. moderate temperature zeolite-based isomerization or solid superacid isomerization), the reaction system is gas phase and similar to ideal gas. Therefore, the effects of reaction pressure and molar ratio of hydrogen to hydrocarbon ( n(H2)/n(HC)) on equilibrium isomerization ratio of n-pentane are insignificant. At low reaction temperature (e.g. low temperature isomerization), the reaction system is gas phase or gas-liquid two-phase and shows nonideality. As a result, the influence of reaction pressure and n(H2)/n(HC) on the reaction should not be neglected. The equilibrium isomerization ratio of n-pentane can be increased by decreasing the reaction pressure or increasing n(H2)/n(HC).
Key words: n-pentane, isomerization, isopentane, thermodynamics, SRK equation