Influence of reaction temperature on ICCU-methanation using LaNiO3 DFM

https://doi.org/10.1016/j.fuel.2022.123842

“To better understand the differences in the catalytic behaviour, Fig. 8 plots CH₄ concentration profiles during complete CO₂ adsorption and hydrogenation cycles at 280, 400 and 520 °C for DFMs obtained from 30% LaNiO₃/CeO₂, 30% LaNiO₃/La-Al₂O₃ and LaNiO₃ precursors. Profiles corresponding to the 30% LaNiO₃/Al₂O₃ precursor have not been included since they are similar to those of La-Al₂O₃-supported sample. In general, the evolution of CH₄ is significantly affected by DFM composition, especially at intermediates-high temperatures. The maximum CH₄ production is observed at initial times for the alumina-supported sample, whereas this process is delayed and takes place more progressively for the DFM obtained from bulk perovskite. On the other hand, the ceria-supported sample shows an intermediate CH₄ production profile. As previously observed in Table 1, the specific surface area was significantly higher for supported samples with respect to that observed for the DFM derived from bulk perovskite, which leads to the exsolution of Ni NPs with significantly lower average particle size than bulk counterpart (31.7 nm), especially for ceria-supported sample. Furthermore, this sample shows the higher proportion of medium basic sites with respect to strong basic sites. Taking into account that the close contact between storage component and the Ni⁰ NPs is regarded as the key factor to efficiently transfer of dissociated H to desorb, and subsequently to hydrogenate, adsorbed CO₂, these facts explain the wider temperature window of the DFM derived from the 30% LaNiO₃/CeO₂ formulation. In contrast, the stability of adsorbed species is limited for alumina-supported sample, favouring only the CH₄ production at the beginning of the hydrogenation period and low temperatures.”

“Fig. 8. CH₄ concentration profiles during a complete CO₂ adsorption and hydrogenation to CH₄ cycle at: a) 280, b) 400 and c) 520 °C for the DFMs obtained after the controlled reduction of 30% LaNiO₃/CeO₂, 30% LaNiO₃/La-Al₂O₃ and LaNiO₃ precursors.”