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

Katarzyna Świrk Da Costa; Paulina Summa; Jithin Gopakumar; Youri van Valen; Patrick Da Costa; Magnus Rønning

doi:10.1021/acs.energyfuels.3c02994

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

Energy Fuels. 2023 Nov 17;37(23):18952-18967. doi: 10.1021/acs.energyfuels.3c02994. eCollection 2023 Dec 7.

Authors

Katarzyna Świrk Da Costa¹, Paulina Summa^{2

3}, Jithin Gopakumar¹, Youri van Valen¹, Patrick Da Costa², Magnus Rønning¹

Affiliations

¹ Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.
² Institut Jean Le Rond d'Alembert, Sorbonne Univeristé, CNRS UMR 7190, 78210 Saint-Cyr-l'Ecole, France.
³ Faculty of Energy and Fuels, AGH University of Science and Technology, 30-059 Cracow, Poland.

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 CH₄ and CO₂. 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 Ni²⁺ to Ni⁰ 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 Y₂O₃ and/or NiYO₃. The dominant deactivation mechanism was the carbon encapsulation of Ni particles and the growth of filaments.