(178f) Catalytic Methane Steam Reforming with Ni-xMo2C/FAU: Formation Energetics and Promoting Role of Molybdenum Carbide Clusters Encapsulated

Encapsulation of molybdenum carbides and oxides in zeolites leads to effective catalytic particles for methane conversion and biomass upgrading. Here, we report our recent study on methane steam reforming (MSR) for hydrogen production using Ni-xMo₂C/FAU as the catalyst. It is found that the synergetic effects between Ni and Mo₂C particles lead to enhanced activity and catalytic stability, in which Mo₂C enhanced CH₄ activation and conversion. In addition, sintering and coking are the major deactivation mechanisms, and Mo₂C clusters demonstrate high thermal stability, sintering resistance, and high dispersion during and after the reactions. The conclusions in this catalytic investigation are supported by our experimental thermodynamic studies on the formation energetics of Mo₂C and MoO₃ under encapsulation in FAU with different Si/Al ratios using high-temperature oxide melt solution calorimetry. Specifically, at a fixed Mo loading, the formation enthalpies of both Mo₂C/FAU and MoO₃/FAU from constituent carbides and oxides tend to be less endothermic as the Si/Al ratio increases. The Mo₂C – FAU interactions are energetically more favorable than the encapsulation of MoO₃ in FAU by ∼30 kJ/mol per tetrahedron unit. Interestingly, the MoO₃ clusters present high redox transition flexibility to reach energetically favorable states, yet strong interfacial bonding between Mo₂C and FAU pays for the energetic cost leading to highly dispersed Mo₂C particles with enhanced catalytic, thermal, and thermodynamic stability.