Increased methanation activity through passivation of the silica support

Chemical route to prepare nickel supported on intermetallic Ti6Si7Ni16 nanoparticles catalyzing CO methanation

In this study, ternary intermetallic nickel silicide, Ti₆Si₇Ni₁₆, nanoparticles with a high surface area of 37.5 m² g^-1 were chemically prepared from SiO₂-impregnated oxide precursors, which were reduced at as low as 600 °C by a CaH₂ reducing agent in molten LiCl, resulting in the formation of single-phase Ti₆Si₇Ni₁₆ with a nanosized morphology. The intermetallic Ti₆Si₇Ni₁₆ phase in the nanoparticles was stabilized in air by surface passive oxide layers of TiO_x-SiO_y, which facilitated the handling of the nanoparticles. Considering our previous successful work of preparing single-phase LaNi₂Si₂ (39.3 m² g^-1) and YNi₂Si₂ (27.0 m² g^-1) nanoparticles in a similar manner, the proposed chemical method showed to be a versatile approach in preparing ternary silicide nanoparticles. In this study, we applied the obtained Ti₆Si₇Ni₁₆ nanoparticles as catalyst supports in CO methanation. The supported nickel catalyst showed an activation energy of 56 kJ mol^-1, which is half as low as that of common TiO₂-supported nickel catalysts. Also, Ni/Ti₆Si₇Ni₁₆ provided the lower activation energy more than any previous Ni-based catalyst. Since the measured work function of Ti₆Si₇Ni₁₆ (4.5 eV) was lower than that of nickel (5.15 eV), it was suggested that the Ti₆Si₇Ni₁₆ support can accelerate the rate-determining step of C-O bond dissociation in CO methanation due to its good electron donation capacity.

Ru nanoparticles supported on amorphous ZrO2 for CO2 methanation

The influence of support materials and preparation methods on CO₂ methanation activity was investigated using Ru nanoparticles supported on amorphous ZrO₂ (am-ZrO₂), crystalline ZrO₂ (cr-ZrO₂), and SiO₂.

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.

Predictive morphology, stoichiometry and structure of surface species in supported Ru nanoparticles under H2 and CO atmospheres from combined experimental and DFT studies

CO and H₂ chemisorption stoichiometries of silica supported Ru nanoparticles are understood by combining chemisorption experiments and ab initio calculations.