Mechanism of CH4 dry reforming by pulse microcalorimetry: Metal nanoparticles on perovskite/fluorite supports with high oxygen mobility

The mechanism of CH4 dry reforming on Pt, Ru, Ni, Ni + Ru-supported perovskite (PrFeOx, LaPrMnCrOx) or fluorite (LnCeZrOx) oxides was studied using a Setaram Sensys DSC TG calorimeter and a pulse kinetic installation. For catalysts in the steady-state, CH4 and CO2 transformation in separate pulses proceeds with the rate and products selectivity equal to that in mixed CO2 + CH4 pulses. Heat effects of separate stages correspond to CH4 oxidation into syngas by strongly bound bridging oxygen forms of support (heat of adsorption up to 650 kJ mol−1 O2 for fluorites and ∼500 kJ mol−1 O2 for perovskites) and their replenishment by CO2 dissociation, respectively. These features demonstrate a step-wise red-ox (Mars-van-Crevelen) mechanism of CH4 dry reforming. Fast oxygen transfer from the sites of oxide support to the metal/oxide interface provides required conjugation of stages.

► Step-wise bifunctional mechanism of CH4 dry reforming was proved.
► CH4 and CO2 are independently activated on metal and oxide sites.
► CH bond breaking is rate-limiting stage.
► Strongly bound oxygen species of support selectively oxidize CH4 into syngas.
► Fast oxygen transfer from support to metal sites provides conjugation of stages.