2523-55-9Relevant articles and documents
The hydrogenation of para-toluidine over rhodium/silica: The effect of metal particle size and support texture
Hindle, Kenneth T.,Jackson, S. David,Stirling, Diane,Webb, Geoff
, p. 417 - 425 (2006)
The hydrogenation of para-toluidine was studied over a series of rhodium/silica catalysts. The reaction exhibits an antipathetic particle size effect, suggesting that plane face surface atoms, such as C39 sites, are the active site for ring hydrogenation. The reaction is zero-order in p-toluidine and first-order in hydrogen, with the mechanism of formation of the cis and trans isomers likely through surface immine and enamine intermediates. The activation energy for the trans isomer (62 ± 4 kJ mol-1) was systematically greater than that of the cis isomer (51 ± 6 kJ mol-1). The support was also shown to play a part, adsorbing trans-4-MCYA in the early stages of the reaction, resulting in a varying cis:trans ratio. The effect of pore size was also studied; a dramatic decrease in activity was observed at pore diameters 64 A.
Ceria supported Ru0-Ruδ+ clusters as efficient catalyst for arenes hydrogenation
Cao, Yanwei,Zheng, Huan,Zhu, Gangli,Wu, Haihong,He, Lin
supporting information, p. 770 - 774 (2020/08/24)
Selective hydrogenation of aromatic amines, especially chemicals such as aniline and bis(4-aminocyclohexyl)methane for non-yellowing polyurethane, is of particular interests due to the extensive applications. To conquer the existing difficulties in selective hydrogenation, the Ru0-Ruδ+/CeO2 catalyst with solid frustrated Lewis pairs was developed for aromatic amines hydrogenation with excellent activity and selectivity under relative milder conditions. The morphology, electronic and chemical properties, especially the Ru0-Ruδ+ clusters and reducible ceria were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), CO2 temperature programmed desorption (CO2-TPD), H2 temperature programmed reduction (H2-TPR), H2 diffuse reflectance Fourier transform infrared spectroscopy (H2-DRIFT), Raman, etc. The 2% Ru/CeO2 catalyst exhibited good conversion of 95% and selectivity greater than 99% toward cyclohexylamine. The volcano curve describing the activity and Ru state was found. Owning to the “acidic site isolation” by surrounding alkaline sites, condensation between the neighboring amine molecules could be effectively suppressed. The catalyst also showed good stability and applicability for other aromatic amines and heteroarenes containing different functional groups.
Ni-Catalyzed reductive amination of phenols with ammonia or amines into cyclohexylamines
Cuypers, Thomas,Morias, Thomas,Windels, Simon,Marquez, Carlos,Van Goethem, Cédric,Vankelecom, Ivo,De Vos, Dirk E.
, p. 1884 - 1893 (2020/04/07)
Phenol and its derivatives, which naturally occur in lignocellulose, can be considered as a renewable feedstock not only for aromatic, but also for alicyclic compounds, such as primary and N-substituted cyclohexylamines. So far, the latter are mostly produced from non-renewable starting materials like benzene via problematic nitration/reduction or cross-coupling routes. Herein, an efficient reductive amination of phenol with ammonia or amines is demonstrated, for the first time without the need for rare and expensive noble metals and without using any additives. Various supported Ni catalysts were screened and we elucidated the influence of the key parameters, including the acid-base properties of the supporting material. Acquired knowledge was then applied to different phenol-ammonia/amine combinations, resulting in the synthesis of various primary, secondary and tertiary cyclohexylamines in fair to very high yields.
Enhanced Selectivity in the Hydrogenation of Anilines to Cyclo-aliphatic Primary Amines over Lithium-Modified Ru/CNT Catalysts
Tomkins, Patrick,Müller, Thomas E.
, p. 1438 - 1445 (2018/03/30)
The hydrogenation of aromatic amines to the corresponding cycloaliphatic primary amines is an important industrial reaction. However, secondary amine formation and other side reactions are frequently observed, resulting in reduced selectivity. The side products are formed mostly on the support, yet support effects are little understood at present. This study describes the facile modification of Ru/CNT catalysts with LiOH, by this means significantly improving catalyst selectivity in toluidine hydrogenation without decreasing the activity of the catalysts. The effect is explained by LiOH diminishing acidic sites on the catalyst support and enhancing the adsorption of the aromatic ring on the metallic ruthenium nanoparticles. With the LiOH-modified Ru/CNT catalyst, other substrates, such as methylnitrobenzenes, are also converted efficiently. This study thus describes an improved catalyst for the preparation of cyclohexylamines and provides guidelines for future catalyst design.
