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

Abstract

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 PtO x 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, LaPtO x [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.

New Perspectives on Catalytic Hydrogen Production by the Reforming, Partial Oxidation and Decomposition of Methane and Biogas

“…[185] 650-1100 [44] 3-25 [44] 0.9-1. TCD 58 [187,191] 500-1000 [162,163] 1 [162] 2 USD/Kg [8] 2.55-5 USD/Kg [12] 3.53-3.82 USD/kg [192] 1.72 USD/kg * Data available in literature refer to non-catalytic process.…”

“…Kozonoe et al [162] compared carbon nanotubes and silica support for Ni catalysts and found that while both supports showed stable activity, carbon nanotubes offered better methane and carbon dioxide conversions, and also greater selectivity for hydrogen formation at 750 • C, mainly attributed to lower carbon dioxide activation by silica due to the acidic nature of the support. The deactivation behavior of bimetallic molybdenum catalysts supported on lanthana-alumina and on niobia determined that only NiMo catalysts are active on a lanthana-alumina support, while PtMo is active on a niobia support [163]. On a lanthanaalumina support, the Pt bimetallic catalyst rapidly deactivated due to sintering, while the CoMo catalyst deactivated due to oxidation of the cobalt species both on the lanthanaalumina and the niobia support.…”