Reactive Distillation for Acetates from Ethanol and Iso-propanol Mixtures

This work presents a feasible design for conducting esterifications of ethanol (EtOH) and iso-propyl alcohol (IPOH) mixtures with acetic acid (HAc). The NRTL-HOC thermodynamic models are used for modeling the vapor-liquid and vapor-liquid-liquid equilibrium. The reactions are catalyzed by using Amberlyst-15 catalyst. Furthermore, the Pre-exponential factors of esterification of ethanol based on Calvar is modified. There are two alternative arrangements regarding the alcohol mixtures as feed for reactive distillation. In the first, separation of the mixture to pure alcohols goes before esterifying with RD. In the second, esterification by RD goes directly before purifying the products. According to the boiling point ranking and the phase equilibrium data, conceptual process design is proposed. Aspen Plus simulator is then used to find an optimal flow sheet with a minimum total annual cost for each of the two arrangements above mentioned. After comparing the total annual cost (TAC), the second arrangement turns out to haves more economical benefit than the first one. The second arrangement includes a RD and close the exit on the bottom of RD. And use a decanter in order to separate water from organic phase. Part of organic phase stream will go back into the RD. The organic phase then is feed into a stripper to obtain EtAc and IPAc mixtures on the bottom of stripper. Overhead vapors of the stripper recycle to the decanter in order to increase the conversion for reactant. In the end, we use a distillation column to separate ester mixtures.
Although the resulting optimal process can achieve high product specifications, heat integration needs to be considered for reducing the energy cost and the total annual cost. To decrease the energy consumption and capital cost, the separation columns in the above process is integrated to a DWC configuration. By simulation, compared with the original design, in this DWC design, all energy required is provided by the reboiler of the distillation column. To make this major saving possible, this DWC indeed avoids the remixing effect that used to take place is the original stripper bottom.