Olefin isomer separation by reactive extractive distillation:Modelling of vapour-liquid equilibria and conceptual design for 1-hexene purification

摘要

A thermodynamic model was developed to describe the vapour-liquid equilibria encountered in the reactive extractive distillation of 1-hexene mixed with n-hexane and 2-methyl-1-pentene,used to represent a Fischer-Tropsch stream.Experimentally it is determined that the feed mixture behaves nearly ideal in the absence of any solvent and that the obtained selectivities are near unity.A non-reactive solvent(D2EHPA)increases the activity coefficients but does not significantly improve the selectivity.The selectivity can only be increased by enriching the solvent with a metal-ion(Ag).The model uses the Wilson equation to describe the activity coefficients and can represent the vapour-liquid equilibria accurately as function of composition,pressure and temperature.To produce 1-hexene with a 99% recovery and at 99.5% purity,the solvent-to-feed ratio should be around 5(at 0.2 bar,T=311 K).Under these conditions the selectivity is 1.34(2-methyl-1-pentene/1-hexene)and 1.55(n-hexane/1-hexene)and the minimum number of equilibrium trays approximately 42.