Molecularly Tailored Nickel Precursor and Support Yield a Stable Methane Dry Reforming Catalyst with Superior Metal Utilization

Syngas
production via the dry reforming of methane (DRM) is a highly
endothermic process conducted under harsh conditions; hence, the main
difficulty resides in generating stable catalysts. This can, in principle,
be achieved by reducing coke formation, sintering, and loss of metal
through diffusion in the support. [{Ni­(μ2-OCHO)­(OCHO)­(tmeda)}2(μ2-OH2)] (tmeda = tetramethylethylenediamine),
readily synthesized and soluble in a broad range of solvents, was
developed as a molecular precursor to form 2 nm Ni(0) nanoparticles
on alumina, the commonly used support in DRM. While such small nanoparticles
prevent coke deposition and increase the initial activity, operando X-ray Absorption Near-Edge Structure (XANES) spectroscopy
confirms that deactivation largely occurs through the migration of
Ni into the support. However, we show that Ni loss into the support
can be mitigated through the Mg-doping of alumina, thereby increasing
significantly the stability for DRM. The superior performance of our
catalytic system is a direct consequence of the molecular design of
the metal precursor and the support, resulting in a maximization of
the amount of accessible metallic nickel in the form of small nanoparticles
while preventing coke deposition.