Alternative ball-milling synthesis of vanadium-substituted polyoxometalates as catalysts for the aerobic cleavage of C-C and C-O bonds

Vanadium-substituted phosphomolybdic acids (H3+x[PMo12-xVxO40], denoted as V-x) are well-known oxidation catalysts that are generally prepared by the hydrothermal treatment of MoO3 and V2O5 in the presence of H3PO4. This synthesis procedure is highly energy consuming and the V-x yields are not always acceptable. In the present work, an alternative hybrid mechanochemical/hydrothermal synthesis of V-x is proposed, comprising the ball-milling of MoO3 and V2O5, followed by a hydrothermal attack. The resulting materials, with 2 <= x <= 3, obtained from this new route were compared, in terms of yield, energy consumption and catalytic activity, with a reference V-3 sample prepared through a conventional hydrothermal treatment. The ball-milling step proved to lead not only to a shorter and far more energy-saving synthesis procedure, but also to high yields of V-x. Moreover, V-x from this alternative route proved to be generally more active than the conventionally prepared V-3 in the aerobic oxidative cleavage of C-O and C-C bonds in 2-phenoxyacetophenone, used herein as a lignin model compound.

Automated summary

An alternative mechanochemical/hydrothermal synthesis method for V-x was proposed, resulting in higher yields and greater catalytic activity compared to the traditional method of preparation. The ball-milling step in this new process proved to be more energy-saving and efficient in producing V-x catalysts.