CuCoMgAlO_x Mixed Oxides as Selective Catalysts for the Hydrogenation of Furan Compounds

Single phase CuCoMgAl-layered hydroxides were obtained by making fine adjustment to their composition through changing the (Co + Cu)/Mg = 0.5; 1; 2; 3 and Co/Cu = 0.5; 1; 2 ratios. The rise of Co/Cu in systems contributed to the increase in their thermal stability. CuCoMgAl-catalysts showed high selectivity of carbonyl group hydrogenation in furfural and 5-hydroxymethylfurfural. In furfural hydrogenation, the selectivity to furfuryl alcohol was more than 99%, and in 5-hydroxymethylfurfural hydrogenation, the selectivity to 2,5-hydroxymethyl furfural was 95%. The surface of the samples with different Co/Cu after calcination and reduction was the same and had a «core-shell» structure (TEM). «Core» consisted of Cu and Co metallic particles. «Shell» consisted of CuCoMgAlOx mixed no-stoichiometric spinel oxides. There was no sintering or change in size of the metallic particles after the reaction. For the sample with Co/Cu = 1, their phase composition after reaction remained unchangeable. The increase of Co/Cu led to the formation of an X-ray amorphous phase after the reaction. This suggests the decrease in structural stability of this sample. The obtained results prove the prospects of using bimetallic CoCu-systems for hydrogenation of furan aldehydes, and opens up new directions for further research and improvement

Anisotropy of destruction viscosity of hot-pressed silicon nitride

The paper discusses the study of destruction viscosity and hardness of silicon nitride samples produced by hot pressing from powder and rolled ribbons. Anisotropy of crack resistance and a crystallographic texture are identified in both types of samples. The studies establish that the destruction viscosity in the direction parallel to the hot pressing force is higher than in the perpendicular direction. A comparative analysis of anisotropy reveals its weak dependence on preliminary rolling