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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·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 °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. [ABSTRACT FROM AUTHOR]

Nickel catalysts with carbon-mineral supports derived from sapropel were synthesized; the effect exerted by the nature of the support (type of the initial sapropel) and active component precursor on the activity of the catalysts in the model reaction of liquid-phase nitrobenzene hydrogenation was studied. The catalysts, synthesized using the support with a smaller fraction of carbon, were more active irrespective of the precursor nature. The highest activity was observed for the catalysts synthesized from nickel nitrate and formate; nitrobenzene conversion was 65% and 51%, respectively, after 1 h of reaction. The catalysts retained high activity after six reaction cycles at 100% aniline selectivity. The presence of sulfur in the nickel precursor deteriorated the catalytic activity (convection less than 3%) due to formation of the sulfide phase. [ABSTRACT FROM AUTHOR]

Due to a detailed analysis of NMR spectra of the reaction solutions with different composition obtained by the aqueous‐phase catalytic (Pd/C) hydrogenation of 2,4,6‐trinitrobenzoic acid, the intermediate compounds were identified and a more substantiated mechanism was proposed for the formation of the main reaction products—1,3,5‐triaminobenzene and cyclohexane‐1,3,5‐trione trioxime. The condensation of the 1,3,5‐triaminobenzene molecules produced by a complete hydrogenation of 2,4,6‐trinitrobenzoic acid was shown to result in the formation of a paramagnetic heterocyclic compound. [ABSTRACT FROM AUTHOR]

Highlights: [•] Increase the fraction of bridging OH groups and concentration of Lewis acid sites. [•] Preferential formation of outer-sphere complexes. [•] Changes in the dispersion and electronic state of supported Pt. [•] Effect of hydrothermal treatment of the support on catalytic properties of Pt/Al2O3. [ABSTRACT FROM AUTHOR]