Sol–gel synthesis and investigation of catalysts on the basis of perovskite-type oxides GdMO 3 (M = Fe, Co)

The perovskite-type oxides GdCo x Fe 1−x O 3 (x = 0; 0.2; 0.5; 0.8; 1) synthesized by the sol–gel method were tested as catalysts in the dry reforming of methane to syngas between 500 and 950 °С at atmospheric pressure. Thermal analysis (TG and DSC coupled with MS) and phase analysis (X-ray diffraction) were used for the synthesis parameters control. The morphology and surface area were determined by BET and SEM methods. The highly crystalline, homogeneous and pure solids with well-defined structures were prepared. The mixed GdCo x Fe 1−x O 3 (x = 0; 0.2; 0.5; 0.8; 1) structure belongs to an orthorhombic crystal system with a space group of Pnma (62). The partial substitution of Fe by Co leads to the increase of the catalytic activity. in the row: GdFeO 3 < GdFe 0.5 Co 0.5 O 3 < GdCoO 3 ⩽ GdFe 0.8 Co 0.2 O 3 ≈ GdFe 0.2 Co 0.8 O 3 . An additional point is that the presence of Co in B-site suppresses secondary reactions such as reverse water gas-shift without slowing the dry reforming reaction, which produces syngas in a ratio close to 1. [Figure not available: see fulltext.]. © 2019, Springer Science+Business Media, LLC, part of Springer Nature

Effect of Cobalt in GdFeO3 Catalyst Systems on Their Activity in the Dry Reforming of Methane to Synthesis Gas

Abstract: Perovskite-type complex oxides GdFeO3 and GdCo0.5Fe0.5O3 synthesized by the sol–gel method and gadolinium ferrite modified with cobalt oxide (5 wt %) are studied as catalysts for the dry reforming of methane. Single-phase catalysts with the perovskite orthorhombic crystal structure and an average particle size of 100–200 nm are synthesized. Catalytic activity testing shows that the surface modification of gadolinium ferrite with cobalt, as well as the introduction of Co directly into the crystal structure to form a GdCo0.5Fe0.5O3 solid solution, leads to the formation of new catalytically active sites and provides an increase in the activity of GdFeO3. The sample with cobalt oxide deposited on the surface is highly resistant to coking. © 2020, Pleiades Publishing, Ltd

Dry Reforming of Methane over GdFeO3-Based Catalysts

Abstract: Features of dry reforming of methane over perovskite-type complex oxide GdFeO3 synthesized by several methods (solid-phase, citrate–nitrate sol–gel, glycine–nitrate sol–gel syntheses) have been studied. It has been found that the use of the sol–gel method leads to the formation of porous catalysts consisting of nanosized particles. Significant differences in morphology and texture affect the catalytic properties of GdFeO3. The sample synthesized by the citrate–nitrate sol–gel method mediates the conversion of hydrogen contained the feed methane to molecular hydrogen at a selectivity of 90%. It has been shown that GdFeO3-based catalysts exhibit a stable on-stream behavior for a long time. © 2020, Pleiades Publishing, Ltd

Abnormal enhancement of light output by cation mixing in ZnxMg₁₋ₓWO₄ nanocrystals

In the paper the effect of light output increase with maximum at x = 0.5 observed previously for the mixed ZnxMg₁₋ₓWO₄ crystals is demonstrated for nanocrystals with the same composition. The enhancement of light output up to 3 times at the transition from bulk to nanosize was shown. This effect is determined by nonlinear dependence of concentration of oxygen vacancies with minimum at x = 0.5 for ZnxMg₁₋ₓWO₄ nanocrystals.