Effect of pH on catalyst activity and selectivity in the aqueous Fischer–Tropsch synthesis catalyzed by cobalt nanoparticles

Dry Reforming of Methane on Single-Site Ni/MgO Catalysts: Importance of Site Confinement

“…In this study, a combined density functional theory (DFT) calculations and kinetic Monte Carlo (KMC) simulations together with the coordinative studies in experiment was employed and the complex dry reforming of methane (DRM, CO 2 + CH 4 → 2CO + 2H 2 ) on single-atom Ni 1 /MgO­(001) and single-site Ni 4 /MgO­(001) model catalysts was used as a case study, aiming to understand the behavior of SSCs toward complex catalytic processes. The DRM is one of the effective ways for utilizing two of the greenhouse gasescarbon dioxide (CO 2 ) and methane (CH 4 )to produce syngas, − which can be used as the feedstock for catalytic processes, such as Fischer–Tropsch and methanol synthesis. − However, the conventional Ni catalysts for the DRM deactivate quickly, because of sintering of the active metal phase and carbon deposition via the Boudouard reaction (2CO → C + CO 2 ) and/or CH 4 decomposition (CH 4 → C + 4H). ,− One of the solutions is the formation of small Ni particles supported on MgO − by reducing NiO–MgO solid solutions, being able to exhibit a high stability against metal sintering and a strong coking resistance. − Alternatively, several possibilities including Ni concentration, , the oxygen vacancies (O vac ) produced during the reduction, , and the electronic modification introduced by the strong Ni-MgO interaction have been proposed . However, because of the complexity of the reaction, the origin of promoting effects remains elusive.…”

Effect of the Polymeric Stabilizer in the Aqueous Phase Fischer-Tropsch Synthesis Catalyzed by Colloidal Cobalt Nanocatalysts

“…45°, 35°, and 60° ( Figure 3 ). The broadening of XRD peaks was previously observed for CoNPs prepared by chemical reduction using NaBH 4 [ 23 , 24 ], and associated to the small size and/or to the amorphous structure of the NPs [ 25 , 26 ]. Surface analysis by X-ray photoelectron spectroscopy (XPS) revealed the presence of Na, Co, O, N, C, and B. Deconvolution of the Co 2p XPS spectra (see Supporting Information) revealed that the metallic cobalt content ranged from 6% to 67% for this series of NPs.…”

“…Furthermore, important amounts of boron were detected in all the CoNPs (2–13 mol %) ( Table 1 ). As previously reported, boron doping frequently occurs during the synthesis of cobalt nanoparticles prepared by NaBH 4 reduction [ 24 , 30 ]. The molar ratio between the cobalt and boron at the NPs’ surface revealed that the series of CoNPs can be divided in two groups: those with relatively large cobalt content at the surface, with Co/B ratios above 1 ( Co1 , Co2 , Co5 , and Co6 ), and those in which the boron content is superior to that of cobalt ( Co3 and Co4 ).…”

“…Concerning the product selectivity, Co4 and Co6 exhibited high selectivities towards CO 2 and CH 4 , respectively (97% and 48%). The other catalysts ( Co1 , Co2 , Co3 , and Co5 ) exhibited typical product selectivities for the aqueous phase FTS catalyzed by CoNPs [ 23 , 24 ]. The selectivity of Co4 towards CO 2 can be correlated to the presence of sodium at the metal surface since it was the counter ion of the polyanionic stabilizer (polymer 4 , Figure 1 ) [ 39 ].…”

One-pot synthesis of cobalt nanoparticle-embedded lamellar sheets by using inorganic complex via thermal decomposition route

“…Ferromagnetic cobalt nanoparticles has received considerable attention due to its extraordinary electrical, catalytic, and magnetic properties, which are of interest for basic scientific research and potential technological applications in, for example, high-density information storage, catalysts, magnetic sensors, magnetic fluids, etc. [4][5][6][7]. A series of techniques have been applied for synthesis of cobalt nanocrystals, such as ball milling, synthesis, direct current electrodeposition, direct reduction method, hydrothermal route, and metalorganic decomposition [8][9][10][11][12].…”