Coke deposition over Ni-based catalysts for dry reforming of methane: effects of MgO-Al2O3 support and ceria, lanthana promoters

Abstract

The coke deposition, a major challenge in the dry reforming of methane process (DRM), was investigated over the different Ni-based catalysts varied, Ni loading 5–12.5 wt% over γ-Al2O3, MgO content 30–70 wt% in MgO.Al2O3 and Ce, La promoters, prepared by incipient wetness impregnation method. The prepared catalysts were studied for the DRM activity and stability under the severe reaction conditions of 800 °C, 1 atm, CH4/CO2 = 1 and GHSV 1700 h−1 in a bench-scale reactor. The higher catalytic activity and coking resistance were observed at 5% Ni over γ-Al2O3 and 30% MgO in MgO.Al2O3 unpromoted catalysts attributed to the corresponding strong metal-support interaction and the highly stable MgAl2O4 spinel with a large number of medium strength basic sites. While the stability tests over the highly active promoted catalysts up to 76 h exhibited the pressure drop build-up of 0.40 bar in order of NiCeLa/MgO.Al2O3 < NiCe/γ-Al2O3 < NiLa/γ-Al2O3, similar to total carbon and the graphitic carbon deposition. The comparatively higher activity and stability over the catalyst NiCeLa/30MgO.70Al2O3 was assigned to the mainly amorphous coke formation. Also, the regeneration of a spent catalyst NiCe/γ-Al2O3 in the graphitic carbon regime further increased the pressure drop to 0.55 bar, revealing the difficulty of graphitic carbon regeneration. In addition, the regenerated catalyst exhibited decreased catalytic activity and the rapid increase of pressure drop 1.03 bar due to the catalyst deactivation.