Reactive Distillation - a Viable Solution for Etherification of Glycerol with tert-Butyl Alcohol

Two different alternatives for etherification of glycerol (G) with tert-butyl alcohol (TBA) are developed and analyzed. The conventional reaction - separation - recycle system uses a plug-flow reactor to perform the reaction in liquid phase, in the presence of a heterogeneous catalyst (Amberlyst 15). The separation of the products from reactants is achieved by two distillation columns where pure glycerol ethers (GTBE) are obtained, and a section involving extractive distillation with 1,4-butanediol as solvent, which separates TBA from the TBA/water azeotrope. Due to large number of units involved, the total annual cost (TAC) is very high. The second alternative employs a reactive distillation column, where TBA is fed as vapour below the reactive zone, while glycerol enters as liquid above the reactive zone. High purity water and glycerol ethers are obtained as distillate and bottoms, respectively. Because multiple steady states are detected, sensitivity analysis is used to choose a safe operating point. Finally, the controllability of reactive distillation setup is proved by dynamic simulation.