Modified niobic acid via acidification by various liquid acids for dehydration of succinic acid to succinic anhydride

The dehydration of succinic acid to succinic anhydride has been brought into the spotlight due to its environmental-friendly process. However, it is still an industrial challenge to enhance the dehydration performance under moderate reaction conditions. In this study, a series of acid-treated niobic acid catalysts were prepared for the dehydration of succinic acid to succinic anhydride. The textural properties and relative Lewis acid contents in samples could be affected by different liquid acid, thus resulting in the different catalytic activities. More interestingly, after the treatment of H3PO4, NbOPO4 instead of Nb2O5·nH2O could be formed. And H2SO4-treated niobic acid formed Nb2O4SO4. Among these samples, H3PO4/Nb2O5·nH2O exhibited the highest activity for the dehydration of succinic acid to succinic anhydride, which was attributed to the maximum specific surface area and moderate relative content of Lewis acid. Yields as high as 80% in the dehydration of succinic acid to succinic anhydride catalyzed by 5 wt% H3PO4/Nb2O5·nH2O could be reached at 150 ℃ for only 5 h, which has greatly promoted the development of industrialization.