Influence of Ni support on ICCU-RWGS

The following work reported the use of different supports for Ni-based catalysts, which were physically mixed with CaO for ICCU-RWGS.

“The ICCU-RWGS performance using Ni/support-CaO bifunctional combined materials (BCMs) with various supports (e.g. ZrO₂, TiO₂, CeO₂ and Al₂O₃) are shown in Fig. 7. Here Ni particles were used as active catalytic sites, and CaO played as the CO₂ adsorbent. A typical ICCU-RWGS process mainly included two steps, one was CO₂ adsorption from a diluted CO₂ source (e.g. 20% CO₂/N₂), and another was hydrogenation of the captured CO₂. The above two steps were isothermally operated by switching the inlet gas between 20% CO₂/N₂ and 5% H₂/N₂. The SiO₂/CaO was used as a blank benchmark material to demonstrate the ICCU-RWGS performance with bare inert support compared to active Ni metal over active supports. To reveal the optimal support for the ICCU-RWGS process, various Ni/support-CaO bifunctional combined materials were evaluated at 550–750 °C.”

“Fig. 7. Integrated CO₂ capture and RWGS performance of various Ni/support-CaO BCMs: (a) CO₂ conversion; (b) CO selectivity; (c) CO yield and (d) C1 species (CO₂ + CO + CH₄) yield.”

“As shown in Fig. 7a and 7c, the CO₂ conversions and CO yields of various Ni/support-CaO BCMs followed the decreasing order: Ni/CeO₂-CaO > Ni/TiO₂-CaO > Ni/ZrO₂-CaO > Ni/Al₂O₃-CaO. All of the Ni/support-CaO BCMs exhibited excellent CO selectivity (∼100%) over the investigated temperature range. The Ni/Al₂O₃-CaO showed only a comparable performance with SiO₂-CaO in terms of CO₂ conversion and CO yield, indicating the poor catalytic activities of nonreducible NiAl₂O₄ spinel (Fig. 5a). However, Ni/TiO₂-CaO with NiTiO₃ spinel achieved much high CO₂ conversion compared to Ni/Al₂O₃-CaO owing to the better spinel reducibility. Although there was no spinel formation, Ni/CeO₂-CaO outperforms Ni/ZrO₂-CaO in relation to CO₂ conversion and CO yield. For example, Ni/CeO₂-CaO and Ni/ZrO₂-CaO achieved 56.1% and 34.0% for CO₂ conversion and 2.7 and 1.1 mmol g⁻¹ for CO yield at 650 °C, respectively.”