Simulation And Optimization Of Process Isolating High Purity Isobutene From C4 Raffinate

High purity isobutene(HPI) is an important monomer in polymerization process of butyl rubber. Reactive distillation process based on skeletal hydro-isomerization of C4 olefins shows great technological advantages in isolating HPI from C4 fractions.For further investigation, reaction kinetics and thermodynamic properties of C4 olefin hydroisomerization are analyzed. Results demonstrate that the single-pass conversion of 1-butente to 2-butene is up to 96%in relatively low temperature.Steady-state simulation of reactive distillation process using Aspen Plus software shows that high reflux ratio and proper position of reactive stages are key factors to get extremely high conversion of 1-butene. Optimized operating parameters are obtained by parameter sensitivity analysis. The concentration of isobutene in product of reactive distillation reaches 94.4%.Extractive distillation process is selected for isolating HPI from the top product of reactive distillation. Relatively volatilities of C4 fractions under the influence of NMP, DMF and ACN are respectively predicted by UNIFAC model. Results show that the mixture of NMP and water is relatively more suitable to be the extractive agent for separating isobutene.A new process for producing HPI which is combined by reactive distillation and extractive distillation is set up with Aspen plus, the model of the process is established and parameter sensitivities of extractive distillation are analyzed. Results show that the established process is suitable for HPI production, the purity of HPI is more than 99.5%(wt). The key operating parameters of extractive distillation are solvent:feed ratio and solvent entrancing temperature. Economic assessment shows the process mentioned is simple, clean and profitable.