Catalytic valorisation of Chlorella sp. algae to obtain 5-Hydroxymethylfurfural in the presence of Nb2O5 or NbOPO4

Microalgae are interesting biomass able to growth in not-arable lands, in wastewaters or seawaters. There are plenty of species of microalgae and several of them find application in various industrial sectors because they are source of several products in an integrated biorefinery view. In this work two acidic heterogeneous catalysts, namely Nb2O5 and NbOPO4 have been used. Both are commercial products provided by CBMM and they have been physico-chemically characterised. The isomerisation/dehydration reactions proceed through a tandem pathway involving the Lewis and Brønsted acid sites provided by the surface of the acidic solids giving rise to the isomerization of glucose to fructose, followed by dehydration of fructose to 5-HMF. The higher number of Brønsted acidic sites (BASs) on the NbOPO4 catalyst surface with respect to Nb2O5 has been claimed to justify its better performance. NbOPO4, which resulted more acidic than Nb2O5 and which led to 21 % yield to 5-HMF on the total sugars.