How do Core–Shell Structure Features Impact on the Activity/Stability of the Co‐based Catalyst in Dry Reforming of Methane?

Abstract

Dry reforming of methane has been systematically investigated over a series of x‐Co@SiO2‐y catalysts where x is the Co particle size ranging from 11.1 to 121.3 nm while y denotes the silica shell thickness ranging from 6.0 to 21.9 nm. Various techniques including TEM, XRD, H2‐TPR/‐TPD, XPS, BET, O2‐TPO, TG, and H2‐TPSR‐MS were employed to characterize physicochemical properties of catalysts. H2‐TPR and XPS results indicate that the core–shell interaction is dependent on the core size: the smaller the Co particle size is; the stronger the core–shell interaction. The investigations employing H2‐TRSR‐MS and XPS on the spent catalysts demonstrated that a fraction of metallic Co was re‐oxidized on a large‐core catalyst such as 121.3‐Co@SiO2‐72.2 during the reaction, and such oxidation leads to lower catalytic activity and stability. O2‐TPO results indicated that the catalyst with smaller core size caused significant coking. TG analysis together with TEM investigation on the used samples suggested that carbon deposition is notably core‐size‐dependent and responsible for deactivation of the small‐core catalyst. Among various core–shell structured catalysts, 27.8‐Co@SiO2‐14.3 showed superior activity and durability, owing to the well‐balanced property between coking and anti‐oxidation of Co cores.

Cobalt@Silica Core‐Shell Catalysts for Hydrogenation of CO/CO2 Mixtures to Methane

“…For Co@SiO 2 catalysts Pang et al [17] examined the influence of the shell structure on the activity and selectivity in the dry reforming of methane. However, the composition at the reaction locus is depending on the diffusive transport of reactants and products through the porous shell for material B. Consequently, the diffusion rates governed by the molecular diffusion coefficients and the pore size, as well as the effective diffusion length given by the spatial arrangement of the active nanoparticles inside the supporting shell is important.…”

“…Consequently, the loss in active surface area by migration and subsequent coalescence of single atoms or aggregates as well as Ostwald ripening is hardly avoidable, leading to deactivation under reactions conditions. Pang et al [17] examined Co@SiO 2 catalysts in the dry reforming of methane and found that the core size as well as shell thickness need to be carefully balanced in order to ensure a high activity as well as to avoid coking and oxidation of Co cores. These systems offer an improved sinter resistance and allow to tailor the combination of physical and chemical functionalities on the nanoscale, as well as to generate a confinement effect.…”

“…[17,18] Miao et al [19] reviewed possible mechanisms during CO and CO 2 methanation focusing mainly on Ni and Ru catalysts. [17,18] Miao et al [19] reviewed possible mechanisms during CO and CO 2 methanation focusing mainly on Ni and Ru catalysts.…”

Development of Co Supported on Co−Al Spinel Catalysts from Exsolution of Amorphous Co−Al Oxides for Carbon Dioxide Reforming of Methane

“…XRD characterization : The composition, structure, and crystallinity of catalysts after reduction treatment were further analyzed using XRD. Observed in Figure , the diffraction peaks of reduced Co‐30 matched with the standard bulk data of Co, Al 2 O 3 , and CoAl 2 O 4 , confirming the TEM result in Figure (d2) . Meanwhile, for Co‐10, Co‐15, and Co‐20, the diffraction peaks indicate the presence of Co and CoAl 2 O 4 .…”

“…Alternatively, it has been revealed that the supported Co catalysts show good activity for dry reforming process. [9,[12][13][14][15] Even though the catalytic activity is neither superior to Ni nor to other noble metal catalysts such as Ru and Rh, studies on the supported Co catalysts have reported to produce good catalytic performance with significantly lower carbon deposition. [16,17] Previous study suggested that the rate of carbon deposition and the type of deposited carbon on Co metal are different from that on Ni metal.…”