Cyclodextrin-assisted low-metal Ni-Pd/Al2O3 bimetallic catalysts for the direct amination of aliphatic alcohols

Synergistic effects of the bimetallic Ni-Fe systems and their application in the reductive amination of polyether polyols

We report the synthesis of xNi-yFe/γ-Al2O3 catalysts which were applied to the reductive amination of polypropylene glycol (PPG) for the preparation of polyether amine (PEA). The catalysts were characterized by N2-sorption, X-ray diffraction, H2-temperature programmed reduction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to reveal the synergistic effect of the bimetallic Ni-Fe-loaded catalysts. It was found that in the reductive amination of PPG to PEA, the conversion and product selectivity of the reaction were closely related to the types of active centers of the catalyst. In particular, the surface Ni0 content increased by adding Fe as a promoter, with a maximum Ni0 content on the 15Ni-7.5Fe/Al2O3 catalyst, which also led to the highest conversion rate (>99%). In addition, no deactivation was observed after three cycles of reaction carried out by the catalyst.

Uncovering Structure-Activity Relationships in Pt/CeO2 Catalysts for Hydrogen-Borrowing Amination

The hydrogen-borrowing amination of alcohols is a promising route to produce amines. In this study, experimental parameters involved in the preparation of Pt/CeO₂ catalysts were varied to assess how physicochemical properties influence their performance in such reactions. An amination reaction between cyclopentanol and cyclopentylamine was used as the model reaction for this study. The Pt precursor used in the catalyst synthesis and the properties of the CeO₂ support were both found to strongly influence catalytic performance. Aberration corrected scanning transmission electron microscopy revealed that the most active catalyst comprised linearly structured Pt species. The formation of these features, a function result of epitaxial Pt deposition along the CeO₂ [100] plane, appeared to be dependent on the properties of the CeO₂ support and the Pt precursor used. Density functional theory calculations subsequently confirmed that these sites were more effective for cyclopentanol dehydrogenation-considered to be the rate-determining step of the process-than Pt clusters and nanoparticles. This study provides insights into the desirable catalytic properties required for hydrogen-borrowing amination but has relevance to other related fields. We consider that this study will provide a foundation for further study in this atom-efficient area of chemistry.

Current Status of Quantum Chemical Studies of Cyclodextrin Host-Guest Complexes

This article aims to review the application of various quantum chemical methods (semi-empirical, density functional theory (DFT), second order Møller-Plesset perturbation theory (MP2)) in the studies of cyclodextrin host-guest complexes. The details of applied approaches such as functionals, basis sets, dispersion corrections or solvent treatment methods are analyzed, pointing to the best possible options for such theoretical studies. Apart from reviewing the ways that the computations are usually performed, the reasons for such studies are presented and discussed. The successful applications of theoretical calculations are not limited to the determination of stable conformations but also include the prediction of thermodynamic properties as well as UV-Vis, IR, and NMR spectra. It has been shown that quantum chemical calculations, when applied to the studies of CD complexes, can provide results unobtainable by any other methods, both experimental and computational.

FePd nanowires modified with cyclodextrin as improved catalysts: effect of the alloy composition on colloidal stability and catalytic capacity

FePd nanowires of different compositions are thoroughly characterized and assessed as catalysts for the reduction reaction of 4-nitrophenol to 4-aminophenol.

Effects of ruthenium hydride species on primary amine synthesis by direct amination of alcohols over a heterogeneous Ru catalyst

Heterogeneously catalysed synthesis of primary amines by direct amination of alcohols with ammonia has long been an elusive goal. In contrast to reported Ru-based catalytic systems, we report that Ru-MgO/TiO2 acts as an effective heterogeneous catalyst for the direct amination of a variety of alcohols to primary amines at low temperatures of ca. 100 °C without the introduction of H2 gas. The present system could be applied to a variety of alcohols and provides an efficient synthetic route for 2,5-bis(aminomethyl)furan (BAMF), an attention-getting biomonomer. The high catalytic performance can be rationalized by the reactivity tuning of Ru-H species using MgO. Spectroscopic measurements suggest that MgO enhances the reactivity of hydride species by electron donation from MgO to Ru.

Tiny Ni particles dispersed in platelet SBA-15 materials induce high efficiency for CO2 methanation

In this study, short-channel SBA-15 with a platelet morphology (p-SBA-15) is used to support Ni to effectively enhance catalytic activity and CH₄ selectivity during CO₂ hydrogenation. The use of p-SBA-15 as a support can result in smaller Ni particle sizes than Ni particles on typical SBA-15 supports because p-SBA-15 possesses a larger surface area and a greater ability to provide metal-support interactions. The Ni/p-SBA-15 materials with tiny Ni particles exhibit enhanced catalytic activity toward CO₂ hydrogenation and CH₄ formation during CO₂ hydrogenation compared to the same Ni loading on a SBA-15 support. The presence of metal-support interaction on the Ni/p-SBA-15 catalyst may increase the possibility of abundance of strongly adsorbing sites for CO and CO₂, thus resulting in high reaction rates for CO₂ and CO hydrogenation. The reaction kinetics, reaction pathway and active sites were studied and correlated to the high catalytic activity for CO₂ hydrogenation to form CH₄.