Heterogeneous catalysts for the cyclization of dicarboxylic acids to cyclic anhydrides as monomers for bioplastic production
Cyclic anhydrides, key intermediates of carbon-neutral and biodegradable polyesters, are currently produced from biomass-derived dicarboxylic acids by a high-cost multistep process. We present a new high-yielding process for the direct intramolecular dehydration of dicarboxylic acids using a reusable heterogeneous Lewis acid catalyst, Nb2O5·nH2O. Various dicarboxylic acids, which can be produced by a biorefinery process, are transformed into the corresponding cyclic anhydrides as monomers for polyester production. This method is suitable for the production of renewable polyesters in a biorefinery process.