Work

Ni-Bi-Mo/Al2O3 metal-oxide catalysts for CO2-mediated oxidative dehydrogenation of n-butane into buta-1,3-diene: Bismuth molybdate effect and mechanistic insights

Year: 2026

Type: article

Abstract: Ni-Bi-Mo/Al 2 O 3 metal-oxide systems were prepared via co-impregnation and characterized using XRD, low-temperature (−196℃) N 2 adsorption–desorption, SEM-EDX, H 2 -TPR, NH 3 /CO 2 -TPD, and XPS. Their catalytic properties were investigated in CO 2 -mediated oxidative dehydrogenation of n -butane. Increasing Bi and Mo loadings leads to the accumulation of crystalline bismuth molybdates, thereby reducing the specific surface area and redistributing the acidic and basic sites by strength. As evidenced by TPSR-MS profiles of pre-adsorbed butenes, the increased number of acid-base pairs composed of moderate-strength butene-retaining acidic sites and adjacent lattice oxygen sites capable of hydrogen abstraction from the adsorbed olefin intermediates enables n -butane dehydrogenation toward buta-1,3-diene with a 67% selectivity. Structural changes induced by the catalytic reaction in the most selective catalyst were studied, and mechanistic insights are discussed. During CO 2 -mediated oxidative dehydrogenation of n -butane, the catalyst surface undergoes progressive reduction, transforming bismuth molybdates into crystalline MoO 2 , Mo 2 C, and Bi 0 , with a thin (BiO) 2 CO 3 surface shell. This process results in the concurrent operation of the initial, rapid Mars-van Krevelen cycle alongside a slower but more selective direct dehydrogenation pathway that emerges on the newly formed coordinatively unsaturated sites. Because the bulk Bi–Mo oxide phases cannot be fully re-oxidized to their initial state by CO 2 , direct dehydrogenation on coordinatively unsaturated sites becomes a prominent pathway, operating concurrently with the Reverse Water-Gas Shift reaction.

Source: Next Materials

DOI: 10.1016/j.nxmate.2026.103327