Catalytic Transfer Hydrogenation Reaction Research Articles

Zn Single-Atom Catalysts Enable the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes.

Highly active nonprecious-metal single-atom catalysts (SACs) toward catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes are of great significance but still are deficient. Herein, we report that Zn-N-C SACs containing Zn-N3 moieties can catalyze the conversion of cinnamaldehyde to cinnamyl alcohol with a conversion of 95.5% and selectivity of 95.4% under a mild temperature and atmospheric pressure, which is the first case of Zn-species-based heterogeneous catalysts for the CTH reaction. Isotopic labeling, in situ FT-IR spectroscopy, and DFT calculations indicate that reactants, coabsorbed at the Zn sites, proceed CTH via a "Meerwein-Ponndorf-Verley" mechanism. DFT calculations also reveal that the high activity over Zn-N3 moieties stems from the suitable adsorption energy and favorable reaction energy of the rate-determining step at the Zn active sites. Our findings demonstrate that Zn-N-C SACs hold extraordinary activity toward CTH reactions and thus provide a promising approach to explore the advanced SACs for high-value-added chemicals.

Synthesis of the Pentasaccharide of the K14 Capsular Polysaccharide of Antibiotic Resistant ST25 Acinetobacter baumannii isolate, D46 and O‐Polysaccharide of Acinetobacter baumannii O11

AbstractSynthesis of the pentasaccharide corresponding to the K14 capsular polysaccharide from ST25 Acinetobacter baumannii isolate, D46 and O‐polysaccharide of Acinetobacter baumannii O11 has been achieved in very good yield using a convergent stereoselective [3+2] block glycosylation strategy. The synthetic scheme includes several regio‐ and stereose lective glycosylations as well as orthogonal glycosylation with high yield. Thioglycosides have been used as glycosyl donors using a combination of copper(II) bromide and tetra‐n‐butylammonium bromide (TBAB) as thiophilic activator for 1,2‐cis glycosylation and a combination of N‐iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf) as thiophilic activator for 1,2‐trans glycosylation. Glycosyl trichloroacetimidate derivative was used as glycosyl donor using perchloric acid supported on silica (HClO4–SiO2) as activator. A catalytic transfer hydrogenation reaction has been carried out for the removal of benzyloxy and benzylidene functional groups using triethylsilane as hydrogen source.

Stabilization of unique Zr>4+ species in NiFe2O4 nanocrystals for unprecedented catalytic transfer hydrogenation reaction

Stabilization of transition metal species (like Zr>4+) with increasingly positive charge density at oxide surfaces is highly important for intrinsically improving catalytic performance for many uses like catalytic transfer hydrogenation (CTH) reaction, which however remains inaccessible. Here, we showcase a water-quenching strategy that stably achieves Zr>4+ species at surfaces of prototype spinel oxide NiFe2O4. Systematic investigation unveils that these Zr>4+species were precisely incorporated into surface octahedral Ni sites of NiFe2O4. The local electronic structure was thus regulated. As a consequence, there simultaneously appear electron depletion (Zr>4+) and accumulation (O2-) at the resulted sites, which play the distinct roles as Lewis acid-base sites in (i) facilitating O-H bond dissociation and CO bond activation, (ii) enhancing the interaction and bonding with substrate molecules, and (iii) reducing the energy barrier for hydrogen transfer process. The resulting catalysts exhibit superior catalytic performance and stability in the CTH reaction of biomass-derived carbonyls and representative aldehydes/ketones, especially the reduction of furfural to furfuryl alcohol with a yield of 90.7% under 120 ℃ for 3 h. This work provides new insights into optimizing catalytic activity in metal oxides by stabilizing transition metal species with unexpectedly positive charge density.

Catalytic aqueous hydrodeoxygenation of palmitic acid with in-situ hydrogen donor

Algal bio-oil obtained from hydrothermal liquefaction of algae contains a large amount of water and long-chain fatty acids. High acidity and corrosiveness seriously restrict the application of algal bio-oil. The aqueous-phase catalytic upgrading was a promising approach to solve this problem, and the hydrogen donor was one of the most important parameters to the conversion of the algal bio-oil and the quality of the products. Catalytic transfer hydrogenation (CTH) reaction was an efficient, economical and green method for hydrogenation reaction, which can directly transfer hydrogen from the hydrogen donor to the reaction substrate. In this work, the CTH reaction of algal bio-oil model compound palmitic acid was investigated to deal with the problem of high oxygen content in the algal bio-oil. Several common hydrogen donors, included methanol, ethanol, formic acid, and isopropanol, as well as different reaction conditions were experimented to study the CTH process of palmitic acid. The results showed that, with the reaction conditions of 350 °C and 10 h, formic acid achieved the best oxygen removal, carbon retention and energy efficiency, the C16 selectivity reached the highest at 33.3 % as the formic acid addition ratio was 1:2, and the C15 selectivity reached the highest at 48.3 % as the formic acid addition ratio was 1:3. In general, the best ratio of formic acid added was 1:3, which showed the highest yield of C15 and above alkanes of 79.6 %. This result indicates that the catalytic transfer hydrogenation reaction of formic acid has practical value in improving the combustion performance of algal bio-oil.

Rigorous design, techno-economic and environmental analysis of two catalytic transfer hydrogenation (CTH) processes to produce bio-based 2-methylfuran (2-MF)

The catalytic transfer hydrogenation (CTH) reaction has emerged as a safer method for converting biomass derivatives into value-added chemicals. This study aims to comprehensively evaluate two processes for converting furfural into 2-methylfuran (2-MF) using either methanol (or MeOH, Scheme 1) or isopropyl alcohol (or IPA, Scheme 2) as hydrogen carriers. Both processes were rigorously simulated using Aspen Plus. The reaction performance was modeled using kinetic models developed from literature data. In addition, appropriate strategies are first established for separating the reactor effluents of both processes, which contain multiple azeotropes, based on the thermodynamic parameters estimated through COSMO-based calculations. From the techno-economic analysis, the minimum required selling price (MRSP) of 2-MF is 5.15 USD/kg when produced with Scheme 1, and 3.63 USD/kg when produced with Scheme 2. The MRSP in Scheme 1 becomes 4.50 USD/kg by considering the benefits of the side product, a formalin solution. Compared to various literature data, the MRSPs of these two process schemes are significantly lower than that obtained from direct hydrogenation (6.87 USD/kg). If the cost of the starting materials can be reduced by 25% or more, the MRSP becomes comparable to that obtained from an improved direct hydrogenation process (2.20–3.30 USD/kg). Furthermore, the CO2 emission analysis reveals that Scheme 2 has a lower rate of indirect CO2 emission rate (0.926 Ton-CO2/Ton-2-MF) compared to Scheme 1 (1.088 Ton-CO2/Ton-2-MF). With thorough assessment, we have concluded that the production of 2-MF through the CTH reaction in Scheme 2 is superior. This process shows promise in both economic and decarbonization aspects and could have industrial significance.

Ethanol as hydrogen donor: An efficient transfer hydrogenation of aldehydes, ketones, and nitroarenes with H-bonded Ru(II)-N-heterocyclic iminium complex

Isopropanol and formic acid are predominantly utilized as hydrogen sources in catalytic transfer hydrogenation reactions. However, the utilization of primary alcohols in such reactions has been sparsely documented, with only a limited number of reports available. In this article, we hereby present findings that underscore the prospective application of ecologically sustainable and economically viable ethanol, alongside a ruthenium(II) catalyst that exhibits remarkable resilience in the presence of moisture and oxygen. The air-stable Ru(II) complex (I) has been synthesized by non-covalently interacting anionic Ru(p-cymene)Cl3 and 1,3-diisopropyl-1H-perimidin-2(3H)-iminium (LH2+). The compound was subjected to experimental evaluation to conduct transfer hydrogenation reactions on aldehydes, ketones, and nitroarenes. The process entailed the utilization of ethanol, a hydrogen source that is both economically advantageous and ecologically benign. The hydrogen bond interaction existing between the Ru(p-cymene)Cl3 and LH2+ species plays a crucial in facilitating the exceptional catalytic efficiency exhibited by the Ru(II) complex (I). The reaction exhibits a wide range of substrate compatibility, enabling the hydrogenation of ketones, aldehydes, and nitroarenes. The results obtained from the control experiments have provided evidence for the formation of Ru − H species. A plausible mechanism has been hypothesized, relying on stoichiometric investigations.

Heterocyclic compounds: their potential application as antimicrobials of health importance and in the catalytic hydrogen transfer reaction

Heterocyclic compounds: their potential application as antimicrobials of health importance and in the catalytic hydrogen transfer reaction

Catalytic transfer hydrogenation of furfural via metal-organic framework-derived high entropy alloy catalysts at room pressure

Catalytic transfer hydrogenation (CTH), as an environmentally friendly selective hydrogenation method, has attracted great interest in the preparation of high value-added products from biomass-derived resources. Herein, the carbon-based high-entropy alloy (HEA) catalysts (PtCoNiCuZn@NC-X) were prepared via MOF derivatization, which exhibited good catalytic behavior for the CTH of furfural (FF) with isopropyl alcohol (IPA) as the hydrogen donor. The conversion of FF and selectivity of furfuryl alcohol (FOL) reached 100% at 100 °C without additional pressure via PtCoNiCuZn@NC-600 catalyst. Systematic characterization suggests that the abundance of strong acidic sites, high content of high-valent metals and appropriate alloy surface composition play a crucial role in determining the catalytic behavior. This work confirms the multi-sites synergistic catalysis of HEA, establishing structure-property correlations and revealing reaction pathways that can be extended to other CTH reactions in biomass upgrading processes.

Pt/CeCrO2−x: A multifunctional catalyst for tandem catalysis of lignocellulose hydro-liquefaction and Guerbet reaction

Catalytic transfer hydrogenation (CTH) of lignocellulose liquefaction using renewable ethanol presents a promising alternative to conventional hydrogenation techniques. However, the development of efficient and stable multifunctional catalysts remains a significant challenge. Herein, a Pt/Ce9Cr1O2−x catalyst was developed to facilitate the CTH reactions and achieve nearly complete utilization of lignocellulose. Isotope labeling experiments were conducted to elucidate the mechanism of CTH. The introduction of Cr3+ increased the density of surface oxygen vacancies, consequently enhancing the hydrodeoxygenation ability and metal anchoring. The solid solution structure promotes the electrons transfer from Cr atoms to Pt atoms, forming electron-rich Ptδ+ species that promote ethanol dehydrogenation and lignocellulose hydrodeoxygenation. Furthermore, Pt/Ce9Cr1O2−x catalyst provided optimal acid-base sites and hydroxyl groups, thereby improving ethanol upgrading efficiency and wettability.

Oxygenated groups enriched polyolefin-Zr(IV) complexes catalyzing low-temperature transfer hydrogenation of biomass-derived furfural with 2-propanol

Zr4+−O2− pairs in MOFs and macromolecule − Zr(IV) complexes have proved one of the ideal catalytic components for catalytic transfer hydrogenation of biomass-derived furfural. However, restricted by limited adjustability of Zr4+−O2− coordination environment and the complex design and creation of ligand defects, currently, there are only a few efficient low-temperature (<100 °C) catalytic systems. In this work, oxygenated groups enriched polyolefin − Zr(IV) complexes were prepared and fixed on/in mesoporous silica aerogel support. The complexes possessed a stable structure with CC bonds as the connecting skeleton of each oxygenated group, and the types and densities of oxygenated groups (COOH, SO3H, and OH) could be easily adjusted by using different monomers. In the catalytic transfer hydrogenation reaction of furfural and 2-propanol, the catalyst synthesized using dicarboxylic maleic acid as a monomer of polyolefin exhibited the best catalytic performance in low temperatures, the main product furfuryl alcohol with a high yield of 96.0 % and a high selectivity of 98.2 % was obtained at 85 °C for 8 h. In 6 cycles of reactions at 85 °C, the furfuryl alcohol yield decreased gradually from 96 % in the 1st cycle to 84.0 % in the 4th cycle and further restored to 90.9 % and 89.3 % in the 5th and 6th cycles, respectively, by refreshing the used catalyst with methanol washing, and there was almost no leaching of Zr4+ species in the reaction medium. The catalyst poisoning experiment with acidic and basic sites shielded by pyridine and boric acid, respectively, showed that the catalytic activity was more sensitive to the shielding of basic sites, and the isotope experiments revealed that two H of the product furfuryl alcohol are transferred from 2-propanol. Hereby, the oxygenated group-bearing polyolefin − Zr(IV) complexes with stable structure, variable functional groups and the corresponding various Zr4+−O2– coordination pairs, are ideal catalyst candidates for the selective transfer hydrogenation of furfural to furfuryl alcohol.

Reactivation of Ni-TiO2 catalysts in hydrogen flow and in supercritical 2-propanol-Comparative study by electron spin resonance in situ.

Highly dispersed Ni-TiO2 catalyst has been studied in the process of preparation and under catalytic transfer hydrogenation reaction conditions in supercritical 2-propanol (250°C, 70 bar) using electron spin resonance in situ. Electron spin resonance in situ has been used to study the process of the catalyst passivation and subsequent reduction of the oxide layer in the gas flow. Reduction of the NiO layer on the surface of passivated Ni nanoparticles has been detected in supercritical 2-propanol, which is in agreement with kinetic modeling data. It has been found that the reduction of the nickel oxide layer in supercritical 2-propanol occurs at a lower temperature compared with the reduction in hydrogen flow, according to in situ electron spin resonance study.

Sugars as Emerging Hydrogen Donors in the Synthesis of Alditol via Catalytic Transfer Hydrogenation

AbstractThe utilization of biomass‐derived sugars as the emerging hydrogen donor in catalytic transfer hydrogenation (CTH) reactions has received great attention in recent years. In this work, we proposed two CTH routes of alditol production in the aqueous solution, i. e. self‐disproportionation of sugar and cross CTH of different sugars. Both could realize the process of sugar towards alditol. Taking advantage of the differences in hydrogenation and dehydrogenation capabilities of different sugars, a high C4 alditol yield of 85.9 % was surprisingly obtained via cross CTH route using glucose as the hydrogen donor, which is much better than that obtained when using traditional hydrogen donor isopropanol. The CTH reactions using sugars as the hydrogen donor can not only reduce the utilization of fossil energy, but also provide a new pathway for the production of alditols.

Creation of surface frustrated Lewis pairs on high-entropy spinel nanocrystals that boosts catalytic transfer hydrogenation reaction

Creating frustrated Lewis pairs (FLPs) on stable high-entropy oxides (HEOs) is a new challenge, and also an uncultivated field in catalysis. Herein, holey layered HEO spinel nanocrystals with rich FLPs were synthesized via a temperature-driven topological transition. The FLPs on the surface of HEO spinel nanocrystals are created by oxygen vacancies (Lewis acid sites) and proximal surface hydroxyls or surface lattice oxygen (Lewis base sites). Rich FLPs furnish HEO nanocrystals a superior activity towards the catalytic transfer hydrogenation reaction of biomass-derived carbonyl compounds at mild conditions. The active regions in between FLPs provide a strong driving force for dissociating alcohols and activating carbonyl groups of substrates, as evidenced by the attenuated total reflectance-infrared spectroscopy (ATR-IR) analysis, which enhances the catalytic activity. This work develops a new kind of hydrogenation catalysts and provides a perspective for creating solid FLPs.

Construction of HfO2 nanoparticles with rich hydroxyl group for the efficient catalytic transfer hydrogenation of furfural

Although metal oxide has unique advantages in catalytic transfer hydrogenation (CTH) of furfural (FAL) into furfuryl alcohol (FOL), the excessive stability of the metal site and oxygen coordination leads to the inert Lewis acid site in the oxide, which affects the catalytic activity and limits its broader application. It is known that the hydroxyl group on the oxide surface can promote the adsorption of isopropanol in an alkoxide species by assisting its deprotonation, thereby activating the metal site and enhance the overall reaction activity. However, constructing metal oxide with rich hydroxyl groups is always challenging. This contribution prepared a series of HfO2 nanoparticles (NPs) with rich hydroxyl groups through hydrothermal methods. Systematic characterizations proved the presence of hydroxyl groups on the surface of HfO2 NPs, which promoted its adsorption capacity for isopropanol (hydrogen donor and reaction solvent) and substrate (FAL), thus accelerating the subsequent reaction for CTH of FAL into FOL. As a result, a 100% of FAL conversion with 95.2% of FOL yield was obtained at 160 °C in 4 h, which has significant advantages over commercial and other literature reported oxides. This finding provides a new idea for designing of efficient metal oxides for the CTH reaction by enhancing the hydroxyl group.

Confining Co-Based Nanocatalysts by Ultrathin Nanotubes for Efficient Transfer Hydrogenation of Biomass Derivatives.

Catalytic transfer hydrogenation (CTH) based on non-noble-metal catalysts has emerged as an environmentally friendly way for the utilization of biomass resources. However, the development of efficient and stable non-noble-metal catalysts is crucially challenging due to their inherent inactivity. Herein, a metal-organic framework (MOF)-transformed CoAl nanotube catalyst (CoAl NT160-H) with unique confinement effect was developed via a "MOF transformation and reduction" strategy, which exhibited excellent catalytic activity for the CTH reaction of levulinic acid (LA) to γ-valerolactone (GVL) with isopropanol (2-PrOH) as the H donor. Comprehensive characterizations and experimental investigations uncovered that the confined effect of the ultrathin amorphous Al2O3 nanotubes could modulate the electronic structure and enhance the Lewis acidity of Co nanoparticles (NPs), thus contributing to the adsorption and activation of LA and 2-PrOH. The synergy between the electropositive Co NPs and Lewis acid-base sites of the CoAl NT160-H catalyst facilitated the transfer of α-H in 2-PrOH to the C atom of carbonyl in LA during the CTH process via a Meerwein-Ponndorf-Verley mechanism. Moreover, the confined Co NPs embedded on am-Al2O3 nanotubes endowed the CoAl NT160-H catalyst with superior stability and the catalytic activity was nearly unchanged for at least ten cycles, far surpassing that of the Co/am-Al2O3 catalyst prepared by the traditional impregnation method.

Organodiphosphonate Zr‐MOF: A highly efficient catalyst for Meerwein–Ponndorf–Verley reduction of furfural

AbstractTetraethyl p‐xylenediphosphate is used as the organic ligand to prepare the organodiphosphonate Zr‐based metal organic frameworks (ZrP‐MOF). The physicochemical characterizations of ZrP‐MOF under different hydrothermal and calcination conditions were performed by various analytical techniques. ZrP‐MOF was then employed as a catalyst for the catalytic transfer hydrogenation of furfural with alcohol as the hydrogen donor, and the preparation parameters and catalytic properties of ZrP‐MOF were investigated. Compared with fresh ZrP‐MOF, the furfural conversion of ZrP‐MOF calcined at 825 K increased from 43.5% to 95.1%. Calcination can significantly increase the Lewis/Brønsted acid ratio and enlarge the pore structure of ZrP‐MOF, which promote the furfural catalytic transfer hydrogenation reaction over Zr‐O based on the Meerwein–Ponndorf–Verley reduction.

Construction of electron-deficient zirconium sites for the efficient catalytic transfer hydrogenation of levulinic acid

Zirconium-derived catalyst with abundant Lewis acid-base pairs has earned it a place of prominence for the catalytic upgrade of bio-based carbonyls to valuable chemicals and fuels through catalytic transfer hydrogenation (CTH) reaction. However, the low catalytic efficiency of Zr-based catalysts urgently needs to be improved to meet the criterion for their industrial deployment. In this contribution, tungstophosphoric acid (HPW) was demonstrated as an effective modifier to the electronic structure of the pristine polyacrylonitrile and lignin-supported Zr nanofiber (Zr-Lig@PAN) to boost the CTH of levulinic acid (LA) into γ-valerolactone (GVL). Especially, an impressive GVL formation rate of 32.5 mmol·g−1·h−1 was implemented over Zr/HPW0.75g-Lig@PAN, significantly prevailing over the previous reported Zr-based catalysts for the CTH of LA or its ester to GVL. Mechanistic investigations well demonstrated that the superior electron-accept ability of HPW allowed the construction of electron-deficient Zr sites, which is beneficial to the adsorption and activation of LA and isopropanol, thus boosting the CTH reaction. These findings open up a new avenue to design efficient Zr-based catalysts for the CTH reaction by elaborately tuning the electronic structure of the catalyst in the presence of a second metal.

Amido-ene(amido) Ni(II)-Catalyzed Highly Enantioselective Transfer Hydrogenations of Ketone: Dual Functions of the Ene(amido) Group

Catalytic asymmetric transfer hydrogenation (ATH) reactions of ketones have become an important tool for producing enantiomerically pure alcohols that are widely used in the syntheses of bioactive compounds. However, the high toxicities and low abundances of traditionally employed precious metals serving as catalyst centers have impeded widespread application of precious metal-based catalysts in asymmetric synthesis. Development of catalysts from abundant and less toxic 3d metals is highly desirable but still challenging. We report herein the development of structurally well-defined (R,R)-amido-ene(amido) nickel catalysts for ATH of ketone substrates, facilitating access to a wide range of secondary (S)-configuration alcohols, many of which are synthetic building blocks of biologically relevant molecules, with up to 95% enantiomeric excess (e.e.) and broad scope of functional group tolerance. Catalytic intermediate isolation and density functional theory calculation ascribed the catalytic activity to stabilization of the electron-rich nickel center with the ene(amido) group via a π-backdonation interaction within the catalytic intermediates, while the stereoinduction mainly arises from a catalyst–substrate π–π interaction in the transition state for enantioselective hydride transfer.

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.

Production of γ-valerolactone from ethyl levulinate over hydrothermally synthesized Sn-Beta under mild conditions

Production of γ-valerolactone (GVL) from ethyl levulinate (EL) was studied by catalytic transfer hydrogenation (CTH) strategy under mild conditions. Hydrothermally synthesized Sn-Beta zeolites with high crystallinity show high catalytic activity and selectivity. With isopropanol as hydrogen source, 97.1 % GVL yield with 100 % selectivity was given under 110 °C. Crystallization time for synthesis of Sn-Beta showed great effect on the catalytic performance. Sn-Beta-xd catalysts with longer crystallization time (≥7 days) have high crystallinity and better catalytic performance. Firstly, longer crystallization time is necessary for the formation of large amount of Lewis acid sites which catalyze the conversion of EL to GVL. Secondly, high level of silanol groups in Sn-Beta has negative effect on the catalytic performance. High crystallinity means the amount of silanol groups in Sn-Beta-xd at a low level which is favorable for this CTH reaction. Meanwhile, this is why hydrothermally synthesized Sn-Beta shows higher catalytic activity than post-synthesized Sn-Beta in the conversion of EL to GVL. Furthermore, the catalyst was reusable.