The Ni xCo3– xO4 ( x= 0–0.9) mixed oxides with a spinel structure modified with 2% Cs according to the Pechini method were prepared by coprecipitation from the solutions of nitrates with the use of...

Methane oxidative coupling (OCM) is considered a potential direct route to produce C₂ hydrocarbons. Layered perovskite-like Sr₂TiO₄ is a promising OCM catalyst. Mechanochemical activation (MA) is known to be an environmentally friendly method for perovskite synthesis. Sr₂TiO₄ were synthesized using MA of the mixtures containing SrCO₃ or SrO and TiO₂ or TiO(OH)₂ and annealing at 900 and 1100 °C. XRD and FT-IRS showed that MA leads to the starting component disordering and formation of SrTiO₃ only for SrO being pronounced when using TiO(OH)₂. After annealing at 900 °C, Sr₂TiO₄ was mainly produced from the mixtures of SrCO₃ or SrO and TiO(OH)₂. The single-phase Sr₂TiO₄ was only obtained from MA products containing SrCO₃ after calcination at 1100 °C. The surface enrichment with Sr was observed by XPS for all samples annealed at 1100 °C depending on the MA product composition. The OCM activity of the samples correlated with the surface Sr concentration and the ratio of the surface oxygen amount in SrO and perovskite (O_o/O_p). The maximal CH₄ conversion and C₂ yield (25.6 and 15.5% at 900 °C, respectively), and the high long-term stability were observed for the sample obtained from (SrCO₃ + TiO₂), showing the specific surface morphology and optimal values of the surface Sr concentration and O_o/O_p ratio.

The Ni0.75Co2.25O4catalysts were prepared by a coprecipitation method and modified with cesium cations by impregnation with a solution of cesium nitrate or cesium nitrate with citric acid and...

Mixed oxides 1%Cs/Mg_xCo_3–xO₄ (х = 0–0.9) with a spinel structure are synthesized by precipitation from nitrate solutions using (NH₄)₂CO₃ as the precipitating agent and the subsequent modification of the dry precipitate with cesium by the Pechini method and calcining. The synthesized samples are studied by XRD, BET, SEM, TPR, and TPD methods. It is shown that an increase in the magnesium content leads to a significant decrease in the degree of crystallization of the oxides, an increase in the specific surface area, and the formation of loosely bound oxygen species, which contributes to an increase in the catalytic activity of the samples in nitrous oxide decomposition at temperatures of 150–400°С. The highest activity is exhibited by the 1%Cs/Mg_0.1Co_2.9O₄ catalyst characterized by the presence of the maximum amount of loosely bound oxygen species. It is shown that the presence of oxygen or water in the reaction mixture leads to a decrease in the catalyst activity at 250°C by 10 or 80%, respectively; after that, the catalyst exhibits a stable on-stream behavior for at least 25 h. The catalyst activity is restored after a heat treatment.

Mixed oxides Me_xCo_3−xO₄ (Me: Ni or Mg, x = 0–0.9) with a spinel structure were synthesized by precipitation from Me, Co nitrate solutions using (NH₄)₂CO₃ as the precipitating agent with subsequent modification of the dry precipitate with cesium by the Pechini method and calcination. The samples were studied by XRD, TPR, and TPD methods. Their catalytic activity was studied in the low-temperature (150–350 °C) nitrous oxide decomposition process. It was shown that an increase in the degree of substitution of cobalt (x) leads to a significant decrease in the degree of crystallization of the oxides, an increase in the specific surface area, and the formation of surface weakly bound oxygen species. The highest activity was shown by the catalysts with a degree of substitution x = 0.1, especially by the nickel-substituted sample, which contained the maximum amount of weakly bound surface oxygen species. The difference in the influence of Mg and Ni on the Me_xCo_3−xO₄ properties is discussed.