Ni/Mg/Al anionic clay derived catalysts for the catalytic partial oxidation of methane : Residence time dependence of the reactivity features

摘要: The catalytic partial oxidation (CPO) of methane was investigated with four Ni-based catalysts prepared through reduction hydrotalcite-type precursors. calcination the precursors, generated materials in which Ni species were differently distributed between NiO, (Ni, Mg)Al2O4phases and NiO–MgO periclase structures. relative amount different phases depended on content affected reactivity solids towards CPO step. Catalysts high Ni-content required mild conditions, but deactivated rapidly time-on-stream due to carbon formation. Instead, low activated only after a severe treatment showed stability during reaction. effect residence time particularly stabilized catalyst, order understand if selectivities conversions could be kinetically controlled. Results grouped considering three regions (τ ≤ 70 ms, < τ 150 300 720 ms). In shorter region, large chemical composition variations temperature gradients observed along bed relevant differences surface gas temperatures determined. These differences, not other two regions, are discussed related heat transfer limitation, occurrence direct routes hot spot phenomenon effects.