Excess-Methane CO₂ Reforming over Reduced KIT-6-Ni-Y Mesoporous Silicas Monitored by In Situ XAS–XRD

Abstract

Making Europe less dependent on imported fuels requires a long-term strategy. Low-quality natural gas and biogas could be used to mitigate the energy crisis, and excess-methane dry reforming has the potential to upgrade a mixture of CH 4 and CO 2 . Herein, nickel-based KIT-6-supported catalysts (KIT-6-Ni) were modified with 3, 6, and 8 wt % of yttrium (Y/Ni molar ratio of 0.5, 1.07, and 1.5) to investigate the influence of this element on catalytic performance. Yttrium was well dispersed, preserving the mesopore structure of KIT-6. The yttrium addition increased the total basicity, contributing to a lower deactivation factor and remarkably stable syngas production compared to the catalyst containing only Ni. In situ XAS-XRD showed that Y allowed for the reduction of Ni 2+ to Ni 0 at significantly lower temperatures. A significant difference in the rate of reduction was observed for the studied samples. The analysis showed that the data of linear combination fitting of XANES can demonstrate linear fits with the reduction rate of NiO. The reduction rate of bulk and weakly interacting NiO increased for Y-promoted samples, while a decrease in the rate was registered for species strongly interacting with the support. The latter decreased more with increasing yttrium content. EXAFS analysis showed that Ni is completely reduced in the samples. Under excess-methane dry reforming conditions, the studied catalysts remained fully reduced and showed resistance to sintering of Ni particles. HRTEM results of KIT-6-Ni5-Y8 indicated that metallic Ni particles were decorated by Y 2 O 3 and/or NiYO 3 . The dominant deactivation mechanism was the carbon encapsulation of Ni particles and the growth of filaments.

Review and Outlook of Confined Ni Catalysts for the Dry Reforming of Methane Reaction

“…This would increase the sintering resistance of the metal species at high temperatures. Besides, the hierarchical zeolites have high capacities for molecular adsorption, which would accelerate the transformation rates of reactants. − Currently, zeolites, such as SBA-15, MCM-41, ZSM-5, etc., are reported to accommodate Ni nanoparticles for DRM.…”

Integrated Biorefinery for a Next-Generation Methanization Process Focusing on Volatile Fatty Acid Valorization: A Critical Review

“…A wider overview of the methanization process could lead to better efficiency, keeping in mind that an integrated biorefinery may generate high-value-added products through the intermediates (e.g., volatile fatty acids, VFAs) formed during the methanization stages (e.g., acidogenesis) [ 22 ], through the conversion of gases (e.g., CO 2 and CH 4 ) by further thermochemical processes (e.g., reforming [ 23 , 24 ]), or through extraction of valuable compounds from the digestate before soil-spreading [ 25 ].…”