Investigation of the Deactivation Behavior of MeMo/La<sub>2</sub>O<sub>3</sub>-Al<sub>2</sub>O<sub>3</sub>- and MeMo/Nb<sub>2</sub>O<sub>5</sub> Supported Catalysts (Me = Pt, Ni, and Co) in Tri-Reforming of Methane
João Pedro S. Nascimento, Rita de Cássia F. Bezerra, Elisabete M. Assaf, Alessandra Fonseca Lucrédio, Rinaldo dos Santos Araújo, Gilberto D. Saraiva, Enrique Rodrı́guez-Castellón, Elena Rodríguez‐Aguado, G.S. Pinheiro, Alcinéia C. Oliveira
Abstract
The deactivation behaviors of MeMo/La 2 O 3 -Al 2 O 3 - and MeMo/Nb 2 O 5 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 PtO x species residing in close contact with Mo sites to form a PtMo alloy. This enhanced the CH 4 activation avoiding carbon accumulation in PtMo/Nb 2 O 5 . In contrast, LaPtO x [Pt o ] n surface oxygen species formation neither avoided sintering of the Pt o particles on Mo/La 2 O 3 -Al 2 O 3 nor oxidized the deposited carbon. The incorporation of Co in Mo/La 2 O-Al 2 O 3 and Mo/Nb 2 O 5 caused the continuous reoxidation of Co species because of the presence of O 2, CO 2, and steam reactants during the TRM reaction. Significant coke depositions on the Ni o sites of NiMo/La 2 O 3 -Al 2 O 3 and NiMo/Nb 2 O 5 by the contribution of Boudouard and methane cracking reactions were observed, in short-term stability runs.