NiMoO4 preparation from polyampholytic hybrid precursors: Benefiting of the memory effect in the oxidative dehydrogenation of propane

Abstract

NiMoO4 are prepared thanks to the calcination of hybrid precursors. These catalysts are synthesised from nickel and molybdate ions hybridised with a polyampholytic amphiphilic alternated copolymer. The idea is to take advantage of the copolymer supramolecular organisation to improve the physico-chemical properties and the catalytic behaviour of the catalysts. Homogeneous hybrid materials have been successfully synthesised thanks to interactions between inorganic ions and copolymer charges. The polymer matrix exothermic decomposition favours the crystallisation of nickel molybdate at lower temperatures. Depending on the amount of ions added into the copolymer matrix, either β-NiMoO4 or α-NiMoO4 is stabilised at RT after the calcination of hybrid precursors. The obtention of β-NiMoO4 is unusual as it is generally supposed to be unstable at RT. Moreover, the mixed oxides morphology seems to be related to that of the original copolymer matrix. The three latter points – early crystallisation temperature, phase stabilisation and copolymer preserved morphology, argue in favour of the existence of a memory effect of the copolymer matrix on the final mixed oxides. These NiMoO4 proved to be active in propane oxidative dehydrogenation. As expected, β-NiMoO4 stabilised at RT is more selective in propene than α-NiMoO4 pointing the potentialities of our preparation method.