Nanostructured hybrid materials as precursors of mesoporous NiMo-based catalysts for the propane oxidative dehydrogenation

Nanostructured hybrid materials made of guest ions and a self-assembled copolymer were used as precursors for the preparation of NiMo-based catalysts. The hybrids were calcined in air and the recovered materials were characterized and tested in propane oxidative dehydrogenation. A 6-fold improvement of the yield to propene is obtained as compared with classically prepared catalysts. The exothermic degradation profile of the copolymer is the key point of our approach as it allows to prepare a porous β-NiMoO4, namely the phase particularly desired for its superior propene selectivity. More precisely, the polar backbone and the aliphatic side chains of the copolymer burn at different temperatures. The former ignites at moderate temperatures and initiates the early crystallization of β-NiMoO4. Occurring at higher temperature, the decomposition of the aliphatic part then induces the formation of mesopores. A β-NiMoO4 can thus be prepared at moderate temperatures whereas elevated calcination temperatures (>650 °C) are usually required. This peculiar behavior enables to prevent the texture of NiMoO4 from sintering and to maintain at high levels its mesoporosity, specific area and thus catalytic activity. At the end, the use of our tailor designed copolymer template allows reaching the remarkably high propene yields obtained