LaMn1−xNixO3 Perovskite Deposited on γ-Al2O3 Spheres as Catalyst for Dry Reforming of Methane

Dry reforming of methane (DRM) represents a promising route for the valorization of CO2 captured from industrial emissions through high-temperature catalytic conversion. In this work, a LaMn1−xNixO3 perovskite catalyst (x = 0.25, 6 wt% Ni) was synthesized as a powder by solution combustion synthesis and subsequently deposited onto γ-alumina supports to obtain a structured catalyst. X-ray diffraction confirmed the formation of the perovskite structure, characterized by corner-sharing BO6 octahedra with Ni substitution at the B-site. H2-temperature-programmed reduction (H2-TPR) revealed the reduction of Mn4+ and Mn3+ species to MnO, accompanied by the complete reduction of oxidized Ni species to metallic Ni over the investigated temperature range. Raman spectroscopy of the spent catalyst indicated negligible carbon deposition after DRM. Moreover, the Mn–O stretching band shifted from 657 cm−1 in the fresh catalyst to 643 cm−1 after reaction, consistent with changes in the manganese oxidation state associated with the collapse of the perovskite structure and the formation of MnO. During a 25 h stability test at 700 ◦C, the powdered LaMn1−xNixO3 catalyst achieved a CH4 conversion of 75% at a WHSV of 60 L g−1 h−1. DRM tests performed with the structured catalyst confirmed the catalytic performance under larger-scale operating conditions and different reaction parameters, including temperature, residence time, and CH4/CO2 feed ratio, reaching CH4 conversions of up to 94% at 800 ◦C.