“…The earliest supports used for VPO were traditional oxides, including SiO 2 , 18 TiO 2 , 19 and Al 2 O 3 , 20 as well as novel materials such as SiC. 21 Alternative supports for the VPO catalyst include MCM-41, silica, fumed silica, 22 SBA-15, 23 Al-MCM-41, 24 and zirconia modified with phosphoric acid. 25 The study of niobium-based materials has recently received more attention as a solid acid catalyst in a number of catalytic transformations, such as hydrolysis, esterification, hydration, and dehydration.…”