Nanoarchitectonics of niobium (V) oxide with grafted sulfonic acid groups for solventless conversion of biomass derivatives to high carbon biofuel precursors

Abstract

We report the development of sulfonic acid functionalized niobium pentoxide (Nb2O5) for the synthesis of high dense carbon biofuel precursors from low dense biomass derivatives. Specifically, we have used a Lewis acid catalyst in the form of niobium pentoxide and combination of Lewis and Brønsted acid catalysts in the form of sulfonic acid functionalized catalyst (S-Nb2O5). The structural modification of Nb2O5 after treatment with different amounts of sulfuric acid has been discussed with the help of various techniques. Both Nb2O5 and S-Nb2O5 have been used for the solventless hydroxyalkylation-alkylation (HAA) reaction between 2-methylfuran and furfural (biomass derivatives) to form C-15 product, which can be used as a precursor for the synthesis of biofuels. Variation in the amount of sulfonic group functionalization on the surface of Nb2O5 was performed and it turns out that S3-Nb2O5 having 5.87% atomic percent of S shows the best catalytic activity with a maximum yield of 87% for C-15 product at relatively low temperature (50 °C) under neat conditions. Green metrics calculations have been performed to compare the sustainability and greenness of the reaction with various other catalysts. This work is expected to pave way for the development of acid functionalized metal oxide-based catalysts for biomass conversion reactions aimed towards bioenergy.