Selective Hydrogenation Of Quinolines Research Articles

Constructing fully exposed Pt atomically dispersed catalysts for enhanced multifunctional selective hydrogenation reactions

Constructing highly efficient and low-cost catalysts is essential for the selective hydrogenation reaction. Herein, we developed fully exposed Pt atomically dispersed catalysts (PtAD/C-Al2O3) by a simple carbon modified strategy. Importantly, the co-existence of Pt-O1C2 single atoms and Pt nanoclusters in the PtAD/C-Al2O3 system could exhibit excellent catalytic activity in the selective hydrogenation of quinoline and p-nitrophenol. Notably, the quinoline conversion and the corresponding selectivity of 1,2,3,4-tetrahydroquinoline is 99.6 % and 99.3 %, respectively. Meanwhile, the turnover frequency of PtAD/C-Al2O3 (1081 h−1) is 3.8 and 5.7 times higher than that of Pt single-atom catalysts (PtSA/C-Al2O3) and Pt nanoparticles (PtNPs/C-Al2O3), respectively, during quinoline hydrogenation. Besides, the rate constant of PtAD/C-Al2O3 could reach 192.5 min-1mgPt-1 for p-nitrophenol hydrogenation, which is much better than most of the reported catalysts. Mechanism studies revealed the synergistic effect between Pt-O1C2 single atoms and Pt nanoclusters acts as the main role in enhancing the hydrogenation activity. Specifically, Pt single atoms sites mainly adsorb and activate quinoline molecules, while Pt nanoclusters boost the dissociation of H2 molecules to H atoms. This work paves an origin carbon modified method to construct Pt atomically dispersed catalysts for efficient multifunctional hydrogenation.

Highly efficient and selective hydrogenation of quinolines at room temperature over Ru@NC-500 catalyst

Selective hydrogenation of quinolines into 1,2,3,4-tetrahydroquinolines under mild conditions holds tremendous promise for the green synthesis of a multitude of fine chemicals. Herein, we describe nitrogen-doped carbon supported ruthenium nanoparticles were robust for the mide and selective hydrogenation of quinolines to the corresponding 1,2,3,4-tetrahydroquinolines with both excellent activity and selectivity at 30∼50 °C and 10 bar H2.

Efficient and selective hydrogenation of quinolines over FeNiCu/MCM-41 catalyst at low temperature: Synergism of Fe-Ni and Ni-Cu alloys

The development of non-precious metal catalysts in heterogeneous catalytic processes is of great importance to the hydrogenation of quinolines for both theoretical and industrial applications. Herein, an effective non-precious metal catalyst, 58% Fe4Ni6Cu5/MCM-41, was developed to catalyze the hydrogenation of quinolines under the green and mild conditions, which can achieve 97.5% conversion and exceeding 98% selectivity to tetrahydroquinoline in solvent-free at low temperature of 50 °C. Moreover, the acceptable results of the reusability and gram scale-up experiments proved an industrial application potential of the as-prepared catalyst. Meanwhile, in cyclohexane system, 58% Fe4Ni6Cu5/MCM-41 catalyst can further realize a higher activity of the hydrogenation at a lower temperature of 40 °C, achieving 98.2% conversion and 98% selectivity to tetrahydroquinoline. The existence of Fe-Ni and Ni-Cu alloys in Fe4Ni6Cu5/MCM-41 catalyst was demonstrated by TEM, XRD, XPS, H2-TPD, and Raman spectroscopy. And, Fe-Ni and Ni-Cu alloys can be well dispersed onto MCM-41 molecular sieves. For Fe4Ni6Cu5/MCM-41 catalyst, quinoline molecules can be adsorbed by Fe3+ species on the surface of Fe-Ni alloy through the coordination, while hydrogen molecules can be adsorbed and activated by Ni-Cu alloy. Under the synergism of Fe-Ni and Ni-Cu alloys, the highly effective and selective hydrogenation of quinolines was achieved at low temperature and in solvent-free system. The present approach offers a prospective idea for building non-precious metal catalysts to realize the effective hydrogenation of N-heterocyclic compounds under mild conditions.

Highly dispersed Ni nanoparticles encapsulated in hollow mesoporous silica spheres as an efficient catalyst for quinoline hydrogenation

With the aim of studying the effect of support structure and preparation method on the hydrogenation performance of Ni-based catalysts. Hollow mesoporous silica spheres (hw-mSiO2) containing tiny Ni nanoparticles highly dispersed on the inner surface ([email protected]2) were synthesized by using carbon sphere as template with four continuous procedures, containing Ni deposition, silica shell coating, calcination and reduction. As demonstrated by SEM and TEM, the hollow structure was successfully obtained after calcination and the active Ni species was highly dispersed inside the porous silica shell, which is much smaller than the Ni-based catalysts prepared by a conventional impregnation method using hw-mSiO2 (Ni/hw-mSiO2) or commercial SiO2 (Ni/mSiO2) as supports. TPR and H2-chemisorption results revealed the existence of strong metal-interaction and more hydrogenation sites in [email protected]2. Therefore, [email protected]2 catalyst achieved an excellent catalytic activity and stability in the selective hydrogenation of quinoline into 1–4-tetrahydroquinoline (py-THQ), due to the more dispersed Ni species, strong metal-support interaction and confinement effect of porous silica shell.

Liberating N-CNTs Confined Highly Dispersed CoNx Sites for Selective Hydrogenation of Quinolines.

Selective hydrogenation of quinoline and its derivatives is an important means to produce corresponding 1,2,3,4-tetrahydroquinolines for a wide spectrum of applications. A facile and efficient "laser irradiation in liquid" technique to liberate the inaccessible highly dispersed CoNx active sites confined inside N-doped carbon nanotubes is demonstrated. The liberated CoNx sites possess generic catalytic activities toward selective hydrogenation of quinoline and its hydroxyl, methyl, and halogen substituted derivatives into corresponding 1,2,3,4-tetrahydroquinolines with almost 100% conversion efficiency and selectivity. This laser irradiation treatment approach should be widely applicable to unlock the catalytic powers of inaccessible catalytic active sites confined by other materials.

Selective hydrogenation of quinolines over a CoCu bimetallic catalyst at low temperature

Quinoline derivatives are widely exist in the environment, and mainly separated from the coal tar pitch fraction. Hydrogenation of these compounds to 1,2,3,4-tetrahydroquinolines, an important class of natural products and medicinal agents, is a significant transformation of waste to valuable chemicals. In the present work, we developed a cheap and highly efficient Co3Cu1Ox bimetallic catalyst and used it for the hydrogenation of quinolines at a temperature down to 60 °C. The introduction of Cu into Co catalyst changed the physical and chemical features of Co catalyst, which was characterized by Raman spectra, N2-adsorption/desorption isotherms, H2-TPR and H2-TPD tests. The recycling experiments indicated the catalyst was stable and possessed good reusability. Importantly, the gram-scale experiment provided a high yield (92%) to the target product, demonstrating that the catalytic system has a potential practical application.

N-doped hierarchical porous carbon anchored tiny Pd NPs: A mild and efficient quinolines selective hydrogenation catalyst

Chemoselective hydrogenation of quinolines is often subjected to the problems of leaching and poisoning of catalytic active site as well as harsh reaction conditions. Developing a novel and high-performance heterogeneous catalyst is of paramount importance yet a huge challenge. Herein, we report a facile and efficient strategy for preparing the large surface area and highly N-doped hierarchical porous carbon anchored tiny Pd NPs catalyst, in which the low-cost chitosan, nitrogen-rich ionic liquids are served as composite precursors and KZ molten salt as friendly pore-forming agent. And a series of Pd@CIL-T (C refers to chitosan, IL refers to ionic liquid, T = 600–900 °C) catalysts are successfully fabricated via pyrolyzing aforesaid composites at different temperatures followed by anchoring the highly dispersed and small-sized Pd NPs on their surface. Among all the prepared catalysts, Pd@CIL-900 exhibits the optimal catalytic performance towards the selective hydrogenation of quinoline under extremely mild conditions (0.6 mol% Pd, 0.1 MPa H2 and 50 °C). The kinetic experiments further reveal that such hydrogenation is subject to a pseudo-first order reaction and the apparent activation energy is as low as 41.1 kJ/mol, demonstrating excellent hydrogenation reaction rate. Moreover, the catalytic activity and selectivity are well maintained even after being reused for fifth reaction cycles.

Strong electronic metal-support interaction of Pt/CeO2 enables efficient and selective hydrogenation of quinolines at room temperature

Selectively catalytic hydrogenation of various quinolines in the presence of other reducible groups into the 1,2,3,4-tetrahydroquinoline compounds under mild conditions is a particular challenge for the heterogeneous catalysts due to the natural chemical stability of quinolines and poor chemoselectivity. Pt-based catalysts generally deliver good catalytic activity and selectivity for hydrogenation of quinolines with other reducible groups. However, the over-hydrogenated by-products are also often observed. Herein, Pt nanoparticles supported on CeO2 nanorods (Pt/NR-CeO2) realized highly efficient and chemoselective hydrogenation of various functionalized quinolines at room temperature. The unusual catalytic performance can be attributed to the strong electronic metal-support interactions (EMSI) between Pt and NR-CeO2 with the abundant surface oxygen vacancy, resulting in the enhanced electronic density of Pt nanoparticles. Subsequently, the modulated electronic structure of Pt enables the efficient hydrogen activation at room temperature, leading to a TOF of 546 h−1 of Pt/NR-CeO2 for the selective hydrogenation of 6-chloroquinolines. Density functional theory calculations also reveal that the high electron density of Pt benefits the desorption of the hydrogenated products and thus avoids the over-hydrogenation effectively.

Selective hydrogenation of quinolines into 1,2,3,4-tetrahydroquinolines over a nitrogen-doped carbon-supported Pd catalyst

In this study, we have prepared a nitrogen-doped carbon supported Pd catalyst with abundant porous structures (abbreviated as Pd/CN) for the hydrogenation of quinolines.

Using plant tannin as natural amphiphilic stabilizer to construct an aqueous–organic biphasic system for highly active and selective hydrogenation of quinoline

Black wattle tannin (BWT), a typical natural plant polyphenol, was used as natural amphiphilic stabilizer to prepare BWT-stabilized Pd nanoparticles (BWT-Pd) catalyst. The as-prepared catalyst was found to be highly active in aqueous–organic biphasic hydrogenation of quinoline, which exhibited 100% selectivity to 1,2,3,4-tetrahydroquinoline (py-THQ). Furthermore, the BWT-Pd catalyst can be reused 3 times without significant loss of catalytic activity, thus providing an effective and environmentally benign strategy for the production of py-THQ.

Selective hydrogenation of quinoline and its homologs, isoquinoline, and phenyl-substituted pyridines in the benzene ring

Selective hydrogenation of quinoline and its homologs, isoquinoline, and phenyl-substituted pyridines in the benzene ring