The effects of coke deposition on NiMoO4 used in the oxidative dehydrogenation of butane

The effects of coke deposition on the NiMoO4 catalyst used for oxidative dehydrogenation of n-butane have been investigated, The coke deposition rate and the catalyst changes during this process were studied by TG, FTIR, and XRD. Coke deposition induces segregation of the NiMoO4 into MoO3 and NiO. It was observed that the coke elimination in He/air flow for 30 min is not complete and the catalyst recovers only partially its structure. On the other hand, it was observed that coke deposition pretreatments lead to stabilization of the NiMoO4 beta-phase at room temperature. If the coke is totally eliminated, the beta-phase is again unstable. The expected catalyst deactivation with coke deposition was not observed, To the contrary, the conversion increases about 40% after such treatments, and the selectivity to dehydrogenation products also increases. Especially, the butadiene selectivity is more than twice higher, The increase of conversion and selectivity is ascribed to coke catalytic activity and beta-phase stabilization. (C) 1996 Academic Press, Inc.