Die effektiwiteit van geselekteerde ekstraheermiddels vir die skeiding van n–propanol en 2–butanol tydens ekstraktiewe distillasie

Abstract

The effectiveness of selected extractive agents for the separation of n-propanol and 2-butanol was evaluated with the aid of a circulation vapour-liquid equilibrium still. The difference in boiling points between n-propanol and 2-butanol is 2,1 oC and the corresponding relative volatility is 1,09. The extractive agents and respective relative volatilities of n-propanol achieved were correlated with the physical properties of the pure extractive agent. In the presence of a high-boiling hydrocarbon cut, White oil 2 (C12 - C14 isoparaffin), a relative volatility of 1,57 was achieved. This significantly improves the potential to separate n-propanol from 2-butanol. Hydrogen bonding and polarity mainly contribute to the selectivity of an extractive agent. This result is in agreement with the findings of Yeh ( 1984). Accurate selection can be made using physical properties and can be applied to polar systems in general. The most promising extractive agent, White oil 2, was evaluated and found feasible on pilot plant scale. This evaluation was performed on a close-boiling Fischer-Tropsch alcohol mixture. This extractive distillation was done on a 32 theoretical plate distillation column and a n-propanol purity of 99,85% was achieved. Binary interaction parameters from VLE data were determined with UNIQUAC. These parameters were employed for simulation purposes of the extractive distillation column. Results obtained from modelling of the extractive distillation column furnished good predictions and were in agreement with experimental results.