Selective Transfer Hydrogenation Research Articles

Design of gold catalysts for activation of H2 and H-donor molecules: transfer hydrogenation and CO2 hydrogenation

Gold catalysis can play an important role in selective hydrogenation, transfer hydrogenation and valorization of carbon dioxide into valuable chemicals.

Electrochemical-induced solvent-tuned selective transfer hydrogenation of imidazopyridines with carbazates as hydrogen donors

A solvent-tuned electrochemical protocol for the selective transfer hydrogenation of imidazopyridines using carbazates as hydrogen donors has been developed.

Catalyst-Free Transfer Hydrogenation of Activated Alkenes Exploiting Isopropanol as the Sole and Traceless Reductant.

Both metal-catalyzed and organocatalytic transfer hydrogenation reactions are widely employed for the reduction of C=O and C=N bonds. However, selective transfer hydrogenation reactions of C=C bonds remain challenging. Therefore, the chemoselective transfer hydrogenation of olefins under mild conditions and in the absence of metal catalysts, using readily available and inexpensive reducing agents (i.e. primary and secondary alcohols), will mark a significant advancement towards the development of green transfer hydrogenation strategies. Described herein is an unconventional catalyst-free transfer hydrogenation reaction of activated alkenes using isopropanol as an eco-friendly reductant and solvent. The reaction gives convenient synthetic access to a wide range of substituted malonic acid half oxyesters (SMAHOs) in moderate to good yields. Mechanistic investigations point towards an unprecedented hydrogen bond-assisted transfer hydrogenation process.

Ruthenium-Catalyzed Reductive Coupling of Epoxides with Primary Alcohols via Hydrogen Transfer Catalysis

Herein, we report the ruthenium-catalyzed synthesis of β-alkylated secondary alcohols via the regioselective ring-opening of epoxides with feedstock primary alcohols. The reaction utilized alcohol as the carbon source and the terminal reductant. Kinetic and labeling experiments elucidate the hydrogen transfer catalysis that operates via tandem Markovnikov selective transfer hydrogenation of terminal epoxides and hydrogen transfer-mediated cross-coupling of the resulting alcohol with primary alcohol substrates. A broad scope (40 examples including drugs/natural product derivatives) and excellent regioselectivity for a variety of substrates were shown.

Synergizing the Cu-only catalyst with the amino-modified mesoporous double-shelled nanoreactor for the selective transfer hydrogenation of nitriles

As a typical 3d transition metal, Cu exhibits competitive potential in the catalytic transfer hydrogenation of nitriles due to its low price and appropriate catalytic activity. Unfortunately, the Cu-based catalyst usually requires additional metals to realize good catalytic activity, this makes it difficult to understand the role of Cu. Herein, an amino-modified hollow mesoporous double-shell SiO2 @C (AmHMSiO2 @C) microsphere was applied as a nanoreactor, which achieves the high selective hydrogenation of nitriles over the Cu-only catalyst. The conversion and selectivity to primary amines were 100% and 96% respectively at 60 °C using amino borane as the hydrogen source, and the TOF reaches 199.75 h−1 for Cu. The unique structure of the Cu@AmHMSiO2 @C enhances the activity and stability of the Cu active sites. Comparative experiments demonstrate that the synergy between the nanoreactor and Cu nanoparticles enables the desirable catalytic performance toward the hydrogenation of nitriles to primary amines under mild reaction conditions. This work offers a distinct case for constructing an efficient Cu-based catalyst for heterogeneous hydrogenation reactions.

Selective catalytic transfer hydrogenation of polyunsaturated fatty acid methyl esters using Pd/organobentonite as catalyst under microwave heating

In this study, the catalytic transfer hydrogenation (CTH) of polyunsaturated fatty acid methyl esters (FAMEs) was carried out using ammonium formate as hydrogen donor and Pd/organobentonite (Pd/OB) as catalyst under the assistance of microwave. The effects of different technology parameters on the content of each FAME composition were investigated during the CTH reaction, and the optimal reaction conditions for the hydrogenation of FAMEs were determined. Under the optimal CTH conditions (40 g as the amount of ammonium formate, 60 g as the water amount, 8 wt.% as the catalyst dosage, 80 °C as the reaction temperature, 140 min as the reaction time and 350 rpm as the agitation speed), methyl linoleate (C18:2) was successfully hydrogenated into methyl oleate (C18:1) with high C18:2 conversion ratio (CRC182) of 78.56% and high C18:1 yield of 72.22%, and high selectivity for cis-C18:1 of 70.29%. Compared with conventional heating, microwave heating used in the CTH could enhance the CRC182 from 60.27% to 78.56% and reduce hydrogenation time. Moreover, the reaction of microwave-assisted CTH accorded with pseudo-first-order dynamic model through analyzing the obtained experimental data. In general, the effective hydrogenation of polyunsaturated FAMEs could be achieved under the microwave-assisted CTH reaction.

Selective transfer hydrogenation of nitrobenzaldehydes over an extremely active synergistic MOF@Pt@MOF catalyst

Designing and developing efficient synergistic catalytic systems has always been an exciting topic. In this work, a sandwich-type nanocomposite, UiO-66-NH2@Pt@PCN-222, was utilized as a synergistic catalytic system for the selective reduction of nitrobenzaldehydes to nitrobenzyl alcohols. Benefiting from the synergy of PCN-222 and Pt NPs, the catalyst can efficiently promote the formation of 10 nitrobenzyl alcohols under mild conditions within as short as 30 min. Moreover, the PCN-222 provides not only active sites but also protection for metal nanoparticles, so the catalyst remained intact activity in cycles. This work has reference significance for the construction of synergistic catalytic systems.

Cu/CuOx@C for efficient selective transfer hydrogenation of furfural to furfuryl alcohol with formic acid

AbstractBackgroundCatalytic transfer hydrogenation has been increasingly employed as an effective and safe method for biomass upgrading; however, relying on biomass‐derived formic acid (FA) as hydrogen source has rarely been studied, especially in the production of furfuryl alcohol (FOL) from biomass‐derived furfural (FF) via selective hydrogenation, which is challenging due to diverse unsaturated groups. Herein, in situ encapsulation and stabilization of Cu/CuOx in a porous carbon matrix (Cu/CuOx@C) was reported for the first time and applied in the hydrogenation of FF to FOL with FA.ResultsVarious analytical techniques were used to characterize the effect of pyrolysis temperature on Cu/CuOx@C, since the temperature can be adjusted to control the reduction of the catalyst to give different Cu0/Cun+ ratios. The optimal catalyst Cu/CuOx@C‐450 gave a 99.1% FF conversion and 98% FOL selectivity under suitable reaction conditions, exhibiting excellent activity that was even better than those of noble metal catalysts. Further, density functional theory calculations were used to reveal the effect of Cu species on FA decomposition and final catalytic performance.ConclusionThe catalytic activity of Cu/CuOx@C was influenced by the pyrolysis temperature of the catalyst precursor, and its good performance was mainly attributed to a high dispersion of accessible catalytic Cu/CuOx nanoparticles on the porous carbon and to an appropriate Cu0/Cun+ ratio. © 2022 Society of Chemical Industry (SCI).

NiOBDP and Ni/NiOBDP catalyzed transfer hydrogenation of acetophenone and 4-nitrophenol

The NiOBDP and Ni/NiOBDP composites obtained by calcination of NiBDP MOF (MOF = metal–organic framework; BDP = 1,4-Bis(pyrazol-4-yl)benzene) in air at 700 °C were characterized by XRD (X-ray diffraction), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy. Both nanocatalysts presented high activity in selective transfer hydrogenation of acetophenone (APh) and 4-nitrophenol (4-NP) in mild conditions, using 2-propanol/NaOH or NaBH4/H2O as reducing agents. In both reactions, the catalytic activity of Ni/NiOBDP was higher compared to NiOBDP suggesting the participation of Ni(0) in the hydrogenation process.

Strong metal-support interaction of palladium carbide in PtPd/C catalysts for enhanced catalytic transfer hydrogenolysis of glycerol

Catalytic transfer hydrogenolysis of glycerol can give 1,2-propanediol under mild condition (200 °C) in the absence of external H2. Most existing studies have been focused on metallic catalysts for tandem H2 generation and hydrogenolysis. In this work, a series of bimetallic PtPd/C catalysts with PdCx as promoting role, were synthesized with different calcination temperatures (300–900 °C) and varied Pt/Pd molar ratio (Pd/Pt: 0.5–2.0), to investigate the structure-activity relationship over the in-situ transfer hydrogenation of glycerol. In particular, PtPd/C-900 catalysts showed the best performance (TOF: 37.6 h−1, 1,2-PDO selectivity: 45.3%). It is evidenced that varied metal particle sizes (2.6–7.0 nm) were obtained, and catalytic transfer hydrogenolysis of glycerol displayed size sensitivity over PtPd/C catalysts. Besides, strong metal-support interaction can promote the formation of palladium carbide (PdCx), thus changing the electronic structure of Pt atoms, and improving the activity of hydrogenation reaction and WGS + Reforming reaction. This study will provide insights for the structural design of catalyst for selective transfer hydrogenation of bio-polyols.

Photoresponsive Azobenzene-Functionalized Shell Cross-Linked Micelles for Selective Asymmetric Transfer Hydrogenation.

We describe the substrate-selective asymmetric transfer hydrogenation of aromatic ketones using rhodium complexes immobilized on a photoresponsive nanoreactor. The nanoreactor switches its morphology upon light irradiation in a wavelength-selective manner. Kinetic studies show that the gated behavior in the cross-linking layer is key to discriminating among substrates and reagents during catalysis. Under ultraviolet light irradiation, the nanoreactor displays substrate selectivity, converting smaller ketone substrates faster to the corresponding secondary alcohols.

Highly selective transfer hydrogenation of furfural into furfuryl alcohol by interfacial frustrated Lewis pairs on CeO2

The development of metal-free strategies for selective transfer hydrogenation is of particular interest in the conversion of biomass. Herein, the interfacial frustrated Lewis pairs (FLPs) constructed in CeO2(110) surface have been successfully demonstrated as novel catalytic active sites for the highly selective transfer hydrogenation. The defect-enriched porous nanorods of CeO2 with interfacial FLP sites show the >99.0% selectivity at 95.2% conversion for transfer hydrogenation of furfural to furfuryl alcohol. Mechanism investigations exhibit that the interfacial FLP sites can simultaneously activate furfural and isopropanol, which benefits the enhanced catalytic activity. While, the strong adsorption of aldehyde compounds on the interfacial FLP sites results in the improved hydrogenation and the suppressed pathway of the side-reaction, thereby achieving the superior catalytic selectivity. Such interfacial FLP sites exhibit the great potentials for the selective transfer hydrogenation of various unsaturated compounds.

Selective transfer hydrogenation coupling of nitroaromatics to azoxy/azo compounds by electron-enriched single Ni-N4 sites on mesoporous N-doped carbon

Developing an active and selective non-precious metal catalyst to boost transfer hydrogenation coupling (THC) of nitroaromatics to their corresponding aromatic azoxy/azo compounds is desirable, but remains a great challenge. Herein, for the first time, we report a facile microwave-assisted pyrolysis strategy to successfully prepare the unique Ni-N4 sites on open-mouth quasi-stellate mesoporous N-doped carbon (NC) with enlarged electronic density led by the shortening Ni-N coordination distance (h-Ni1N4 /NC) by microwave heating the 1,10-phenanthroline-Ni complex coated stellate mesoporous SiO2 followed by alkali-leaching, distinct from the single-atom Ni-N5 sites on NC (l-Ni1N5/NC) prepared by a conventional pyrolysis method, unambiguously confirmed by diverse characterization technologies and DFT calculations. More importantly, h-Ni1N4/NC efficiently boosts the selective THC of nitrobenzene to azoxy under mild conditions using isopropyl alcohol (IPA) as hydrogen donor, showing much higher turnover frequency (33.4 h−1) and selectivity (95.6%) than traditional l-Ni1N5/NC catalyst (13.5 h -1°/85.3%) and supported Ni nanoparticles on NC (10.1 h -1, no detectable azoxy). Kinetic experiments and theoretical calculations reveal that the enriched electron density of Ni atoms in single Ni-N 4 sites efficiently lowers activation barrier for IPA/nitrobenzene activation and azoxy formation over h-Ni1N4/NC, which contributes to the outstanding catalytic performance for azoxybenzene production. Moreover, the approach was extended to the transformation of diverse nitroaromatics to corresponding azoxy compounds with high yield. In addition, by varying reaction parameters, h-Ni1N4/NC catalyst enables highly active and selective production of azo compounds via THC reaction of nitroaromatics.

Active metal oxide-nitrogen-doped carbon hybrid catalysts towards selective catalytic transfer hydrogenation of furfural to furfuryl alcohol

Catalytic transfer hydrogenation (CTH) recently attracts significant attention in biorefinery due to the free of using high-pressure fossil-derived H2 that potentially reduce the equipment cost. Herein, up to 20 kinds of metal oxide-nitrogen-doped carbon (MOx-N-C) hybrid catalysts are prepared via a hydrothermal method followed by heat treatment under argon, and the successful preparation of such hybrid catalyst is confirmed by various means. Al is found to be the best element to construct such hybrid catalyst towards CTH, giving 96.6% yield of furfuryl alcohol at 99.3% furfural conversion at 120 oC for 6 h. By combining various characterization techniques, the deactivation and regeneration of AlOx-N-C catalyst is attributed to the change in specific surface area, pore volume, and the number of oxygen vacancies. The excellent catalytic performance of AlOx-N-C catalysts provides a broader prospect for its utilization in other biomass conversions as catalysts or active supports.

Sulfonic groups functionalized Zr-metal organic framework for highly catalytic transfer hydrogenation of furfural to furfuryl alcohol

The highly selective catalytic transfer hydrogenation (CTH) of furfural (FF) to furfuryl alcohol (FOL) is a significant route of biomass valorization. Herein, a series microporous Zr-metal organic framework (Zr-MOF) functionalized by sulfonic groups are prepared. Based on the comprehensive structural characterizations by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, Thermogravimetric (TG) and Fourier transformed infrared spectroscopy (FTIR), we find that sulfonic acid (–SO3H) functional groups are tethered on the UIO-66 without affecting the structure of the framework. Systematic characterizations (NH3-TPD, CO2-TPD, and in-situ FTIR) demonstrate that modifying of sulfonic groups on UIO-66 results in the formation of stronger Lewis acidic-basic and Brønsted acidis sites. The cooperative role of the versatile Lewis acidic-basic and Brønsted acidic sites in 60% mol fraction of sulfonic acid-containing UIO-66 (UIO-S0.6) retain high surface area and exhibit excellent catalytic performance of 94.7% FOL yield and 16.9 h−1 turnover number (TOF) under mild conditions. Kinetic experiments reveal that the activation energy of the CTH of furfural (FF) over UIO-S0.6 catalyst is as low as 50.8 kJ mol−1. Besides, the hydrogen transfer mechanism is investigated through isotope labeling experiments, exhibiting that the β-H in isopropanol is transferred to the α-C of FF by forming six-membered intermediates on the Lewis acidic-basic and Brønsted acidic sites of the UIO-S0.6, which is the rate-determining step in the formation of FOL.

Selective Catalytic Transfer Hydrogenation of Lignin to Alkyl Guaiacols Over NiMo/Al-MCM-41.

Efficient deoxygenation of lignin-derived bio-oils is central to their adoption as precursors to sustainable liquid fuels in place of current fossil resources. In-situ catalytic transfer hydrogenation (CTH), using isopropanol and formic acid as solvent and in-situ hydrogen sources, was demonstrated over metal-doped and promoted MCM-41 for the depolymerization of oxygen-rich (35.85 wt%) lignin from Chinese fir sawdust (termed O-lignin). A NiMo/Al-MCM-41 catalyst conferred an optimal lignin-derived oil yield of 61.6 wt% with a comparatively low molecular weight (Mw =542 g mol-1 , Mn =290 g mol-1 ) and H/C ratio of 1.39. High selectivity to alkyl guaiacols was attributed to efficient in-situ hydrogen transfer from isopropanol/formic acid donors, and a synergy between surface acid sites in the Al-doped MCM-41 support and reducible Ni/Mo species, which improved the chemical stability and quality of the resulting lignin-derived bio-oils.

Facile Synthesis of a Novel Heterogeneous Rh/COF Catalyst and Its Application in Tandem Selective Transfer Hydrogenation and Monomethylation of Nitro Compounds with Methanol

The development of transition-metal heterogeneous catalysts for economical and effective synthesis of N-methylamine, especially for the monomethylation of amines, is still challenging. Herein, two Rh-supported covalent organic framework (COF) heterogeneous catalysts Rh/MelCOF were facile-synthesized by a Schiff base reaction using melamine as a precursor, and, for the first time, it was successfully applied to the effective and high selective tandem reaction of transfer hydrogenation and monomethylation of nitroaromatic hydrocarbons, with methanol as a C1 and hydrogenation source. A series of nitroaromatic hydrocarbons, including heterocyclic or sterically hindered derivatives, can be well tolerated, and the catalyst could also be reused four times without losing significant reactivity. At the same time, the study of the Rh/MelCOF mechanism supports the hydrogen-borrowing mechanism and puts forward the reaction pathway of azobenzene as an intermediate, which is better than the hydrogen-transfer pathway from N-phenylhydroxylamine to aniline directly. This work expands the application of COF catalysts and provides an effective way to obtain mono-N-methylated amines from nitroaromatic hydrocarbons, as well as the detailed mechanism of Rh/COF-catalyzed tandem transfer hydrogenation and monomethylation of amines.

Catalytic Interplay of Metal Ions (Cu2+, Ni2+, and Fe2+) in Mfe2o4 Inverse Spinel Catalysts for Enhancing the Activity and Selectivity During Selective Transfer Hydrogenation of Furfural into 2-Methylfuran

Catalytic Interplay of Metal Ions (Cu2+, Ni2+, and Fe2+) in Mfe2o4 Inverse Spinel Catalysts for Enhancing the Activity and Selectivity During Selective Transfer Hydrogenation of Furfural into 2-Methylfuran

Catalytic interplay of metal ions (Cu2+, Ni2+, and Fe2+) in MFe2O4 inverse spinel catalysts for enhancing the activity and selectivity during selective transfer hydrogenation of furfural into 2-methylfuran

The substitution of Fe2+ from the octahedral sites of the Fe3O4 inverse spinel with Cu2+ and Ni2+ ions can be an effective strategy to synthesize cost-effective mixed metal oxide catalysts for the selective CTH of biomass-derived FUR to 2-MF.

Highly efficient Ni–NiO/carbon nanotubes catalysts for the selective transfer hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan

Ni–NiO/CNTs showed an excellent activity towards the catalytic transfer hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan.