Synthesis of CuAl-LDHs by Co-Precipitation and Mechanochemical Methods and Selective Hydrogenation Catalysts Based on Them

The paper presents the results of the synthesis and study of CuAl layered double hydroxides (LDHs) as well as their application as catalysts for the selective hydrogenation of crotonaldehyde. Phase-homogeneous LDHs were obtained by co-precipitation and mechanochemical methods, and critical parameters ensuring the formation of the target product were identified. In the case of coprecipitation, the formation of LDH is most affected by the pH of the reaction medium and the CO32-/Al3+ ratio. The optimal CO32-/Al3+ ratio is ca. 0.5-0.8 and pH 9.5-10.0. When mechanochemical synthesis is used, at 500 m & BULL;s(-2) and 60 min, it is possible to obtain a single-phase CuAl LDH, whereas at higher energies, LDH is destroyed. The mechanochemical method makes it possible not only to reduce the synthesis time and the amount of alkaline wash water but also to obtain more dispersed copper particles with a higher hydrogenating activity. The conversion of 2-butenal (T = 80 & DEG;C, P = 0.5 MPa, 180 min, ethanol) for this sample was 99.9%, in contrast to 50.5% for the catalyst obtained by co-precipitation. It is important that, regardless of the conversion, both catalysts showed high selectivity (S = 90-95%) for the double bond hydrogenation.

Automated summary

The paper discusses the synthesis and application of CuAl layered double hydroxides (LDHs) as catalysts for selective hydrogenation. Homogeneous LDHs were obtained through co-precipitation and mechanochemical methods, and the important parameters for their formation were identified. The co-precipitation method was found to be most influenced by pH and CO32-/Al3+ ratio, while mechanochemical synthesis allowed for shorter synthesis time and improved catalytic activity. Both catalysts showed high selectivity for double bond hydrogenation with significantly higher conversion for the mechanochemically synthesized sample.