Membrane pervaporation to enhance triacetin production: reaction experiments, simulation and techno-economic analysis of the intensified process

The production of triacetin has emerged as a route for the valorisation of waste glycerol from biodiesel production. Stemming from the esterification reaction of glycerol with acetic acid, which generates water as a by-product, this reaction poses challenges owing to its thermodynamic equilibrium, therefore limiting triacetin yields. Here, a pervaporation membrane reactor is used to remove water in situ from the reaction medium and enhance triacetin yields. Using pure glycerol and Amberlyst-36 as catalyst, conventional batch operation achieved a triacetin yield of 0.63 g triacetin g glycerol −1 at 100 °C. Integrating a pervaporation membrane reactor as a subsequent step, with Nafion 117 membrane, enhanced the yield by 41% up to 0.89 g triacetin g glycerol −1 . The increase in yield was also observed when using purified glycerol (74.3 wt%) derived from 2nd generation crude glycerol. Despite fouling of the membrane, its cleaning procedure was accomplished by washing with deionised water. In terms of industrial scale-up, a process was proposed generating 22,000 tonne yr −1 of high-purity triacetin (99.7 wt%) and 1930 tonne yr −1 of technical diacetin (73.0 wt%). Compared to a membrane-less process, the intensified process attains an increase in triacetin production capacity of 23%. The process also requires 33% less energy (120 MJ kg triacetin −1 ) in terms of both heating and cooling duties. Thus, the total annualised cost decreased by 16% with a triacetin breakeven selling price of £1577 tonne −1 .