Photocatalytic selective oxidation of 5-(hydroxymethyl)-2-furaldehyde to 2,5-furandicarbaldehyde in water by using anatase, rutile and brookite TiO2 nanoparticles

5-(Hydroxymethyl)-2-furaldehyde (HMF) was selectively oxidized to 2,5-furandicarbaldehyde (FDC) in aqueous medium by using home-prepared (HP) anatase, rutile, and brookite TiO2 nanoparticles. HP samples were prepared via a sol−gel method by using TiCl4 as the TiO2 precursor. Commercial TiO2 catalysts were also used for comparison. All samples were characterized by BET specific surface area, XRD, TGA, and SEM, and the reactivity results showed that HP catalysts are predominantly amorphous and give rise to selectivities toward FDC more than twice that of commercial and well-crystallized catalysts.