Carbon-structure affecting catalytic carbon dioxide reforming of methane reaction over Ni-carbon composites

Cu-doped LaNiO3 perovskite catalyst for DRM: revisiting it as a molecular-level nanocomposite

Dry reforming of methane (DRM) was extensively studied on Cu-doped LaNiO3 catalysts. The main findings of this work are as follows: (i) thermal switching of the catalyst phase between the parent perovskite and molecular-level nanocomposite of individual components formed in situ during DRM, (ii) reusability of the catalyst with enhanced activity, and (iii) regeneration of the catalyst phase at a lower temperature than that required for the formation of the parent perovskite. The present investigation provides an extensive analysis and understanding of the DRM reaction using Cu-doped LaNiO3 compared to the result reported by Moradi et al., (Chin. J. Catal., 2012, 33, 797-801) and hence provides new insights into its catalytic activity. Phase-pure LaNi1-xCuxO3 catalysts, specifically LaNi0.8Cu0.2O3, exhibited high catalytic activity towards the DRM reaction (97% CH4 and 99% CO2 conversion with an H2/CO ratio of ∼1.4-0.9). Remarkably, although the initial perovskite phase primarily decomposed into its component phases after DRM, its catalytic activity was barely affected and maintained even after 100 h. The regeneration of the initial perovskite from the disintegrated binary phases via annealing at temperatures even lower than the synthesis temperature together with the amazing retention of activity was very intriguing. The parallel activity of the pristine perovskite and its degraded binary mixtures makes it difficult to identify the actual components responsible for the DRM activity. Accordingly, we have explained the sustained activity of the degraded perovskite catalyst in the context of nanocomposite formation at the molecular level in the reforming atmosphere with the availability of Ni0 and NiO, as revealed by the thoroughly characterized samples in the as-prepared, aged, and regenerated forms.

High activity in the dry reforming of methane using a thermally switchable double perovskite and in situ generated molecular level nanocomposite

This work emphasizes the dry reforming of methane (DRM) reaction on citrate sol-gel-synthesized double perovskite oxides. Phase pure La2NiMnO6 shows very impressive DRM activity with H2/CO = 0.9, hence revealing a high prospect of next-generation catalysts. Although the starting double perovskite phase gets degraded into mostly binary oxide phases after a few hours of DRM activity, the activity continues up to 100 h. The regeneration of the original double perovskite out of decomposed phases by annealing at near synthesis temperature, followed by the spectacular retention of activity, is rather interesting and hitherto unreported. This result unravels unique reversible thermal switching between the original double perovskite phase and decomposed phases during DRM without compromising the activity and raises challenge to understand the role of decomposed phases evolved during DRM. We have addressed this unique feature of the catalyst via structure-property relationship using the in situ generated molecular level nanocomposite.

Highly active and thermostable submonolayer La(NiCo)OΔ catalyst stabilized by a perovskite LaCrO3 support

It is important to develop highly active and stable catalysts for high temperature reactions, such as dry reforming of methane. Here we show a La(NiCo)OΔ (LNCO) submonolayer catalyst (SMLC) stabilized by the surface lattice of a perovskite LaCrO3 support and demonstrate a Ni-Co synergistic effect. The submonolayer/support type catalyst was prepared by in-situ hydrogen reduction of a LaNi0.05Co0.05Cr0.9O3 precursor synthesized by a sol-gel method. The LNCO-SMLC is highly active and very stable during a 100 h on stream test at 750 °C under the reaction conditions of dry reforming of methane. The catalyst also shows good anti-coking ability. We found that the synergistic effect between Ni and Co atoms in LNCO-SMLC remarkably improved the thermostability of the catalyst. This work provides a useful concept for designing atomically dispersed catalysts with high thermostability.

Effect of Calcination Temperature on Cu-Modified Ni Catalysts Supported on Mesocellular Silica for Methane Decomposition

Catalytic methane decomposition has been considered suitable for the green and sustainable production of high-purity H₂ to help reduce greenhouse gas emissions. This research developed a copper-modified nickel-supported mesocellular silica NiCu/MS(x) catalyst synthesized at different calcination temperatures to improve the activity and stability in the CH₄ decomposition reaction at 600 °C. Ni and Cu metals were loaded on a mesocellular silica (MS) support using a co-impregnation method and calcined at different temperatures (500, 600, 700, and 800 °C). The NiCu/MS(600) catalyst not only had the highest H₂ yield (32.78%), which was 1.47-3.87 times higher than those of the other NiCu/MS(x) catalysts, but also showed better stability during the reaction. Calcination at 600 °C helps improve the active nickel dispersion, the reducibility of the NiCu catalyst, and the interaction of the NiCu-MS support, leading to the formation of fishbone and platelet carbon nanofibers via a tip-growth mechanism, resulting in the NiCu metals remaining active during the reaction.

Highly active and stable cobalt catalysts with a tungsten carbide-activated carbon support for dry reforming of methane: effect of the different promoters

A series of cobalt catalysts decorated with different transition metals were synthesized. The introduction of Y improves the dispersibility of the active metal and its oxygen vacancy content, thereby enhancing its activity and anti-coking ability.