Influence of Dopants on Pt/Al$_2$O$_3$-Based Monolithic Catalysts for Autothermal Oxidative Coupling of Methane

Autothermal oxidative coupling of methane (OCM) is a highly attractive approach for methane utilization. If platinum-based catalysts are operated in short-contact-time reactors with high space velocities, high methane conversion can be achieved. Using a 1 wt.% Pt/Al$_2$O$_3$ catalyst as a benchmark, the present study elucidates how different dopants, namely Ni, Sn, and V$_2$O$_5$, affect the OCM reaction. Kinetic catalyst tests reveal that acetylene (C$_2$H$_2$) is the predominant C$_2$ product, irrespective of the catalyst formulation or operation conditions. Furthermore, the use of bimetallic catalysts allows either for the maintenance or even the improvement of the C$_2$ selectivity during OCM, which is attributed to synergistic effects that occur when expensive Pt is partially replaced by cheaper dopants. In particular, the 1 wt.% Pt/Al$_2$O$_3$ reference catalyst yielded a maximum C$_2$ selectivity of 8.2%, whereas the best-performing doped sample 0.25 wt.% Pt 0.75 wt.% V$_2$O$_5$/Al$_2$O$_3$ yielded a total C$_2$ selectivity of 11.3%.