Analyzing an immobilization strategy on membranes to produce green chemicals : The production of glycerol carbonate
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- Global warming and greenhouse gas emissions show the need to find greener energy alternatives. One solution is the production of biodiesel, with glycerol as a by-product. This Gly can be transformed into glycerol carbonate (GlyC) a value-added component compared to the Gly. Thanks to its large amount of oxygen, this GlyC has an interest as a fuel additive. This reaction requires DMC and produces MeOH which form an azeotrope together. In order to improve the GlyC yield, it is necessary to continuously remove this MeOH by a pervaporation system to balance the equilibrium towards the formation of GlyC. This thesis studies the use of composite membranes based on PAN, chitosan and MOFs (ZIF-8, MIL-160 and MOF-801), as well as lipase-type enzymes immobilized on these membranes to serve as catalysts for the reaction of Gly and DMC. Immobilization was performed by adsorption and enzymatic activity tested. During immobilization, the membranes of MOF-801 capture the most lipases, closely followed by ZIF-8. This immobilization is used to stabilize and increase the enzymatic activity of lipases, increasing from a conversion of 23.08 to 23.72% of GLyC and 38.12 to 49.60% of MeOH. More MeOH can be removed by pervaporation to balance the equilibrium. Regarding the pervaporation, it is the membrane of ZIF-8 that allows the best separation factor = 7.95. Reaction conditions were also tested, and the best yields were obtained at neutral pH and MOFs concentration equal to 4 mg/mL. The membrane for the best GlyC production is the one with ZIF-8 MOFs. Regarding reuse, most of the membranes studied promise high rates of reuse (>75%) but some, like those containing ZIF-8 at 4 mg/mL enzymes, have a reuse rate of only 56.1%.