Investigation of the Deactivation Behavior of MeMo/La2O3-Al2O3- and MeMo/Nb2O5 Supported Catalysts (Me = Pt, Ni, and Co) in Tri-Reforming of Methane

The deactivation behaviors of MeMo/La2O3-Al2O3- and MeMo/Nb2O5 supported catalysts were investigated in the tri-reforming of methane (TRM). Characterizations by XRD, SEM-EDS, HRTEM, XPS, FTIR, and Raman spectroscopies were performed, after testing the catalysts in distinct TRM reaction conditions. The effects the transition metal components had on the causes of the deactivations of the solids were evaluated. The reaction conditions favored PtOx species residing in close contact with Mo sites to form a PtMo alloy. This enhanced the CH4 activation avoiding carbon accumulation in PtMo/Nb2O5. In contrast, LaPtOx[Pto]n surface oxygen species formation neither avoided sintering of the Pto particles on Mo/La2O3-Al2O3 nor oxidized the deposited carbon. The incorporation of Co in Mo/La2O-Al2O3 and Mo/Nb2O5 caused the continuous reoxidation of Co species because of the presence of O2, CO2, and steam reactants during the TRM reaction. Significant coke depositions on the Nio sites of NiMo/La2O3-Al2O3 and NiMo/Nb2O5 by the contribution of Boudouard and methane cracking reactions were observed, in short-term stability runs.