High-performance Ni-foam-structured Nb₂O₅–NiO nanocomposite catalyst for oxidative dehydrogenation of shale gas ethane to ethylene: Effects of Nb₂O₅ loading and calcination temperature

Large-scale shale gas exploitation greatly enriches ethane resources, making the oxidative dehydrogenation of ethane (ODE) to ethylene quite fascinating, but the qualified catalyst presents a grand challenge. A series of Ni-foam-structured MO_x-NiO (M = Li, Mg, Ga, Ce, Zr, Mo, W, Nb) composite oxide catalysts (denoted as MO_x-NiO/Ni-foam) have been developed for the oxidative dehydrogenation of ethane to ethylene (ODE). The catalysts were obtained by hydrothermal growth of NiC₂O₄ onto a Ni-foam (110 PPI) and subsequent impregnation with an M-containing salt aqueous solution and calcination treatment. Among them, the Nb₂O₅–NiO/Ni-foam showed superior catalytic ODE performance over the others. Both Nb₂O₅ loading and calcination temperature showed remarkable impact on the catalytic performance. The modification with suitable amount of Nb₂O₅ was responsible for the significant elimination of non-selective oxygen species thereby leading to remarkable improvement of the ethylene selectivity. The activity and selectivity of the Nb₂O₅–NiO/Ni-foam catalysts are also sensitive to the calcination temperature that can modulate the desorption properties of their lattice oxygen species to a great extent. The most promising Nb₂O₅–NiO/Ni-foam catalyst is the one modified with 5 wt% Nb₂O₅ and calcined at 450 °C, being capable of converting 60% ethane with a 68% ethylene selectivity for a feed of C₂H₆/O₂/N₂ = 1/1/8 at 410 °C and GHSV of 9000 cm³ g⁻¹ h⁻¹ (corresponding to a high ethylene productivity of 0.423 g_C2H4 g_cat⁻¹ h⁻¹).