Aerobic Oxidation Of Benzyl Alcohol Research Articles

Molecular Photocatalysts Based on Quinolinium-Grafted Polyoxometalates for Efficient One-Step Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids

Molecular Photocatalysts Based on Quinolinium-Grafted Polyoxometalates for Efficient One-Step Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids

Oxygen vacancy engineering via doping Sr at the La-site of LaMnO3 to promote the ability for aerobic oxidation of benzyl alcohol

Aerobic selective oxidation is a prospective route to synthesize fine chemicals and their intermediates in modern industries, yet the development of an efficient catalyst remains a challenge, due to the limitations in O2 adsorption and activation. Herein, we report a promising La1-xSrxMnO3 (LSMO-x) perovskite oxide for aerobic oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) via oxygen vacancy engineering. Through the substitution of Sr at the La-site of LaMnO3, the quantity of oxygen vacancies, which are active site of molecular oxygen, is greatly increased, thereby improving the efficiency for oxygen activation and the reaction activity. The optimal catalyst, LSMO-0.15, shows BzOH conversion of 97.0 % and BzH selectivity of 93.4 %, at 50 °C, for 3 h. The importance of oxygen vacancy for the reaction is verified by DFT calculations, by comparing the adsorption energies of reactants on LaMnO3 containing with and without oxygen vacancy. A reaction mechanism is also proposed, in which the adsorption and activation of O2 occurs on the oxygen vacancy, and that of BzOH occurs on the Mn4+ ions. The activated O2 and BzOH then react with each other to release H2O and yield BzH.

Aerobic benzyl alcohol oxidation by copper(I)(2,2′-bipyridine)-based catalysts

“In situ” prepared cationic Cu(I) complexes bearing 2,2’-bipyridine ligands and trifluoromethylsulfonate (triflate) have been used to catalyze the aerobic oxidation of benzyl alcohol to benzaldehyde in acetonitrile in the presence of (2,2,6,6-tetramethylpiperidin-1-yl) oxyl (TEMPO). A combination of catalytic reactions, operando1H NMR spectroscopic studies and the analysis of the molecular structure of the Cu(I) precatalysts in acetonitrile by means of DFT calculations shed light on the notable influence of counter-anion ligand interactions on the observed catalytic activity.

Insight into the promotional effect of Ce doped in (FeCoNiCrMn)3O4 high entropy oxides for solvent-free aerobic oxidation of benzyl alcohol

It is desired but challenging to develop a non-noble metal catalyst for the selective oxidation of benzyl alcohol with O2 under solvent-free conditions. Herein, a series of Ce-doped high entropy oxides (Ce/HEOs) were prepared via co-precipitation and subsequent thermal treatment method. It was found that, the doping of Ce could remarkably promote the catalytic activity for selective oxidation of benzyl alcohol to benzaldehyde. The improved activity was ascribed to the good distribution of active Ce species, the increased oxygen vacancies, and the synergistic effect between CeO2 and high entropy oxides (HEOs). In addition, the surface oxygen of Ce/HEOs towards Ce displayed stronger reducibility compared to that of bare CeO2, endowing it stronger deprotonation ability towards benzyl alcohol during the reaction. The prepared catalyst exhibited satisfactory reusability and stability owing to the entropy-stabilized effect of HEOs and the interaction between CeO2 and HEOs, and negligible loss in catalytic activity was observed after seven runs. Besides, DFT calculations disclosed that, with the doping of Ce, the Ce/HEOs catalyst possessed stronger adsorption ability towards benzyl alcohol, and lower free energy was required for the rate-determining step during the whole oxidative reaction. This work gave some insights into the promotional effect of Ce doped into high entropy oxides for the solvent-free catalytic oxidation of benzyl alcohol.

Kinetic Analysis of Solvent Effect in the Photocatalytic, Aerobic Oxidation of Benzyl Alcohol over P25

Background: Photocatalysis is of particular importance in the oxidation of alcohols to aldehydes to increase the conversion of benzyl alcohol oxidation to benzaldehyde at high selectivity, which could be useful for the pharmaceutical and perfumery industries. Objective: The oxidation of benzyl alcohol over P25 was investigated in various solvents (water, benzotrifluoride, toluene and acetonitrile). Methods: These deposits were characterized using TGA and FTIR and could resemble polymers of the hydrated form of benzyl alcohol. UV-Vis was used to find the absorbance of light in various solvents over 190-1100 nm. Result: In the presence of light, the reaction was very selective for the formation of benzaldehyde (e.g., 99% selectivity at 53% conversion using acetonitrile as a solvent), whereas, in the absence of light, the formation of higher molecular weight products was observed (e.g., 22% selectivity at 1.7% conversion using acetonitrile as a solvent). It was observed that the activity in the absence of oxygen was initially high, but it dropped rapidly from initially 0.4 to 0 mmol g-1 h-1 after 2-4 h (using acetonitrile as a solvent). This was attributed to the activity of the few oxidized sites present on P25. Conclusion: Acetonitrile appears to be the most effective solvent, as it seems to interact least with the catalytically active sites. The photocatalytic oxidation of benzyl alcohol over P25 does not only yield products in the solution, but also deposits on the surface. The deposits can be removed in an oxidative environment or an inert environment.

Palladium-based pseudohomogeneous catalyst for highly selective aerobic oxidation of benzylic alcohols to aldehydes

This study presents a novel class of pseudohomogeneous catalysts (PHC) based on carbon quantum dots functionalized with terpyridine ligands (CQDs-Tpy) to immobilize and stabilize palladium nanoparticles (Pd NPs). Extensive characterization techniques clearly confirmed the successful stabilization of Pd NPs on CQDs-Tpy. The effectiveness of the catalyst was demonstrated in the selective aerobic oxidation of primary and secondary of benzylic alcohols to aldehydes in the absence of additives and phase transfer catalyst (PTC). Remarkably, the reactions predominantly yielded aldehydes without further oxidation to carboxylic acids. By employing low catalyst loadings (0.13 mol%), high conversions (up to 89%) and excellent selectivity (> 99%) of the aldehyde derivatives were achieved. Moreover, the CQDs-Tpy/Pd NPs catalyst displayed suitable catalytic activity and recyclability, offering potential economic advantages. This promising approach opens up new opportunities in the field of catalysis for designing subnanometric metal-based PHCs.

Catalytic Activity of Nonaggregating Cu Nanoparticles Supported in Pores of Zeolite for Aerobic Oxidation of Benzyl Alcohol.

Cu nanoparticles (NPs) as catalysts have the good advantage of being more abundant than noble metal NPs. In this study, we synthesized nonaggregating Cu NPs supported in Y-type zeolite by the photoreduction method. In this method, Cu ions in pores of zeolite can be slowly reduced with a small amount of reductant at room temperature. The high-resolution transmission electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction patterns, and UV-Vis spectra supported that nonaggregating Cu NPs existed in the pores of zeolite. Catalytic activities of Cu NP-zeolite were investigated for the aerobic oxidation of benzyl alcohol. Our Cu NP-zeolite had a large turnover frequency of 17 h-1. The yield of benzaldehyde increased in proportion to the amount of Cu loading at ≤0.5 wt %, indicating that Cu NPs in pores of zeolite work as catalysts for selective aerobic oxidation of benzyl alcohol. The high catalytic activity was brought by nonaggregating Cu NPs in pores of zeolite. The catalytic reaction for other aromatic alcohols with electron-donating groups proceeded, whereas it did not proceed for the aromatic alcohols with electron-withdrawing groups or aliphatic alcohols, indicating that the interaction between zeolite and the benzene ring also contributed to the reaction. This study would be expected to contribute to the development of Cu NP catalysts.

Organic-inorganic hybridized Mo/Pd-based complexes as efficient catalysts for selective aerobic oxidation of benzyl alcohols

Organic-inorganic hybrid crystalline compounds have demonstrated outstanding potential utilization in a wide range of catalytic applications. Herein, three organic–inorganic hybrids Mo/Pd-based complexes Mo2O4(CF3COO)2(DMSO)4 (compound 1), Pd(C6H5CH2)2NCS2)2 (compound 2) and Pd[(CH3)2CHCH2NCS2]2 (compound 3) have been controllably synthesized and fully characterized. Remarkably, benefiting from coordinated solvent molecules, the dinuclear oxomolybdates 1 exhibits the efficient homogeneous catalytic activities for the selective aerobic oxidation of benzyl alcohols under ambient pressure (yields up to 90%). Moreover, compound 1 can be reused three cycles in the reactions without significant loss of activity and the possible catalytic mechanisms also be proposed.

Innovative development of hybrid nanocatalyst (ATH-ZnONPs) through green methods for achieving visible light-induced photocatalytic aerobic oxidation of benzyl alcohols into corresponding aldehydes and ketones

In recent research, there has been a surging interest in green methods for manufacturing metal oxide photocatalysts and enabling organic transformations in gentle conditions. This study achieved a groundbreaking development, introducing zinc oxide nanoparticles sensitized with anthocyanin dye (ATH-ZnONPs) for the very first time. The reducing agents in pomegranate leaves were utilized to synthesize ZnONPs from zinc salt. Simultaneously, anthocyanin dye was extracted from pomegranate flowers and linked with the ZnONPs. The FT-IR functional group analysis provided evidence of the successful conjugation of ZnONPs and ATH dye. SEM, EDX, and Elemental Mapping analysis unveiled the spherical morphology and nanocrystalline structure of ATH-ZnONPs, with particle sizes falling within the range of 50–70 nm. XRD analysis verified the hexagonal structural configuration of ZnONPs within the hybrid nanocomposite, with calculated lattice parameters of a = 3.261 Å and c = 5.207 Å. UV–Vis and DRS spectroscopy demonstrated that the composite efficiently harnesses visible light irradiation, exhibiting an energy bandgap of 2.22 eV. The assessment of ZnONPs through BET analysis unveiled a pore volume of 0.053 cm3/g, an SSA of 14.223 m2/g, and an average pore size of 4.18 nm, underscoring the mesoporous characteristics of ZnONPs. Importantly, the photocatalytic performance of the synthesized ATH-ZnONPs was thoroughly examined under blue LED light exposure. This investigation encompassed the evaluation of catalyst dosage, the impact of the light source, stability, regeneration, and the potential for reuse in the aerobic oxidation of benzyl alcohols, resulting in their corresponding aldehydes and ketones. 1HNMR and 13CNMR were used to characterize the products. The results of these studies highlight the versatile potential of this composite for a wide range of photocatalytic applications.

Flowerlike Nanosheet-Based High-Entropy Oxides as Catalysts for Aerobic Oxidation of Benzyl Alcohol

Flowerlike Nanosheet-Based High-Entropy Oxides as Catalysts for Aerobic Oxidation of Benzyl Alcohol

Polyacrylonitrile/cellulose nanofiber supported gold nanoparticles for liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde

Polyacrylonitrile/cellulose nanofiber supported gold nanoparticles for liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde

Copper Nanoparticles Supported on ZIF-8: Comparison of Cu(II) Reduction Processes and Application as Benzyl Alcohol Oxidation Catalysts.

We report the synthesis of a stable heterogeneous catalyst based on copper metal nanoparticles with oxidized surface supported on ZIF-8 for the oxidation of benzyl alcohol under mild temperature and using air as a sustainable oxygen source as well as for the implementation of the tandem "one-pot" catalytic system allowing the sustainable synthesis of benzylidene malononitrile. The influence of the reduction process applied to form the nanoparticle upon the catalyst texture and its performances was extensively examined. After ZIF-8 impregnation with a copper chloride precursor, the reduction of cupric ions into Cu0 nanoparticles was carried out according to two procedures: (i) by soaking the solid into a solution of NaBH4 and (ii) by submitting it to a flow of gaseous H2 at 340 °C. The in-depth physicochemical characterization and comparison of the resulting two types of Cu/ZIF-8 materials reveal significant differences: the reduction with NaBH4 led to the formation of 16 nm sized Cu0 nanoparticles (NP) mainly localized on the external surface of the ZIF-8 crystals together with ZnO nanocrystallites, while the reduction under H2 flow resulted in Cu0 nanoparticles with a mean size of 22 nm embedded within the bulk of ZIF-8 crystals. More, when NaBH4 was used to reduce cupric ions, ZnO particles were highlighted by high-resolution microcospy imaging. Formation of ZnO impurities was confirmed by the photoluminescence analysis of ZIF-8 after NaBH4 treatment. In contrast, ZnO was not detected on ZIF-8 treated with H2. Both types of Cu0 NPs supported on ZIF-8 were found to be active as catalysts toward the aerobic oxidation of benzyl alcohol under moderate temperature (T < 80 °C) and using air as a sustainable O2 source. Benzaldehyde yield of 66% and selectivity superior to 90% were obtained with the Cu/ZIF-8 catalyst prepared under H2 flow after 24 h under these conditions. The same material could be recycled 5 times without loss of activity, unlike the catalysts synthesized with NaBH4, as a result of the leaching of the surface copper NPs over the consecutive catalytic cycles. Finally, the most stable catalyst was successfully implemented in a tandem "one-pot" catalytic system associating benzyl alcohol oxidation and Knoevenagel condensation to synthesize benzylidene malononitrile.

Efficient aerobic oxidation of alcohols and sulfides using an M-doped (M: Mn and Ni) zinc oxide nanostructure

The generation of aldehydes and sulfoxides through selective oxidation process plays an essential role in different organic synthesis. However, using or toxic solvents under harsh reaction conditions leads to wastes and undesired by-products. With this background, ultrafast one-step fabrication of Ni/Mn doped-ZnO was developed under ultrasonic agitation for the first time. The resulting nanostructure was characterized by XRD, SEM, TEM, and BET analysis. According to data, a single-phase ZnO structure (wurtzite type) with uniform morphology, and acceptable surface area was obtained for the prepared nanocatalyst. Next, the catalytic activity of the nanostructure was investigated in aerobic oxidation of aliphatic and benzylic alcohols and sulfides. Notably, the present work is the first report of using ultrasound-engendered Ni/Mn doped-ZnO for selective aerobic oxidation reactions. It was found that the proposed nanostructure represented a novel chemical function for catalyzed alcohols and sulfides oxidation with excellent yields and selectivity without using any additives.

Aerobic oxidation of benzylic alcohols catalysed by new (aryl‐BIAN)copper(I) complexes: Their synthesis and structural characterization

A new neutral dimeric Ar‐BIAN Cu(I) complex (where Ar‐BIAN = bis(aryl‐imino)acenaphthene) of formulation [CuBr(4‐iPrC6H4‐BIAN)]2 (2) was obtained by reacting CuBr and ligand 4‐iPrC6H4‐BIAN (L2) in refluxing acetonitrile under an argon atmosphere. When the ligand used was 2,4,6‐Me3C6H2‐BIAN (L1), we obtained 1 in which the expected dimer (1a) is present, but we could also observe, in solution, the presence of the bis‐chelate dimer [Cu(2,4,6‐Me3C6H2‐BIAN)2][CuBr2] (1b) bearing CuBr2− as counter‐ion; attempts to separate them failed. When the ligand used was 2‐iPrC6H4‐BIAN (L3), we obtained 3 in which the expected dimer (3a) is in equilibrium, in solution, with its bis‐chelate isomer [Cu(2‐iPrC6H4‐BIAN)2][CuBr2] (3b). The solid‐state molecular structures of compounds 2 and 3b were determined by single crystal X‐ray diffraction. The electrochemical behaviour of complexes: 1 (1a, and 1b), 2, and 3 (3a and 3b) and the known compound [Cu(2‐iPrC6H4‐BIAN)2][BF4] (7) were investigated by cyclic voltammetry. The new complexes 1 (1a, 1b), 2, and 3 (3a, 3b) were tested as catalysts for the aerobic oxidation of benzylic alcohols into aldehydes; they all catalyse the reaction, with good results; the catalytic studies were extended to the similar known complexes [CuBr(2,6‐iPr2C6H3‐BIAN)]2 (4), [CuI(2,6‐iPr2C6H3‐BIAN)]2 (5), [CuCl(2,6‐iPr2C6H3‐BIAN)]2 (6) and (7), in order to study the effect of different bridging halides or counter ions in the catalytic activity. We found that compound 4 exhibited a high catalytic activity comparable to the best results published so far. The oxidation products, benzaldehydes, were detected and further confirmed by NMR spectroscopy, and the conversion rate was determined after GC‐FID analysis.

Efficient Dual-Function Catalyst: Palladium-Copper Nanoparticles Immobilized on Co-Cr LDH for Seamless Aerobic Oxidation of Benzyl Alcohol and Nitrobenzene Reduction.

Layered double hydroxides (LDHs) present exciting possibilities across various industries, ranging from catalytic applications to water remediation. By immobilizing nanoparticles, LDHs' characteristics and functionality can be enhanced, allowing for synergetic interactions that further expand their potential uses. A simple chemical method was developed to produce well-dispersed Pd-Cu NPs on a Co-Cr LDH support using a combination of in situ coprecipitation/hydrothermal and sol-immobilization techniques. The Pd-Cu@Co-Cr LDH catalysts was obtained, showing its catalytic activity in promoting the aerobic oxidation of alcohols and enabling the reduction of nitro-compounds through NaBH4 mediation. The physicochemical properties of the prepared catalyst were comprehensively investigated utilizing a range of analytical techniques, comprising FTIR, XRD, XPS, TGA, nitrogen adsorption isotherm, FESEM, and HRTEM-EDX. The findings showed the significance of immobilizing the bimetallic Pd-Cu nanoparticles on the Co-Cr LDH via an exceptional performance in the aerobic oxidation of benzyl alcohol (16% conversion, 99.9% selectivity to benzaldehyde) and the reduction of nitrobenzene (98.2% conversion, rate constant of 0.0921 min-1). The improved catalytic efficacy in benzyl alcohol oxidation and nitrobenzene reduction on the Pd-Cu@Co-Cr LDH catalyst is attributed to the uniform distribution and small size of the Pd-Cu NPs as active sites on the Co-Cr LDH surface. The prepared catalyst demonstrated exceptional stability during repeated runs. This study paves the way for multiple opportunities in tailoring, producing, and precisely controlling catalysts for various organic transformation reactions.

Highly selective and stable polybenzoxazine-based carbon nanosheet supported Pd catalyst for aerobic benzyl alcohol oxidation

Highly selective and stable polybenzoxazine-based carbon nanosheet supported Pd catalyst for aerobic benzyl alcohol oxidation

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions.

We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This structure raised the mixing efficiency of a gas-liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a closed system.

Selective aerobic oxidation of benzyl alcohol under ambient conditions using polyionic nanoclay-supported gold/palladium nanoparticles

Oxidation of alcohols to their respective aldehydes, esters, and acids is a common value-added industrial process, though techniques often rely on harsh reaction conditions (e.g., high temperature, strong base, organic solvents, hydrothermal processes) to achieve rapid reaction turnovers. The incorporation of gold and palladium nanoparticles facilitates the dehydrogenation and O2 reduction processes, respectively, and these advantages can be dually incorporated and enhanced using supported nanoparticle alloys. Herein, we utilize polyionic nanoclays (PINCs) as two-dimensional inorganic-organic architectures for supporting monometallic and bimetallic gold and palladium nanocatalysts for the model oxidation of benzyl alcohol to the corresponding aldehyde, ester, and acid. In addition, we present two new PINC surface chemistries (N-methylpyrrolidinium- and pyridinium-functionalized PINCs) and compare their performances as catalyst supports to show that catalyst enhancement is altered by the PINC surface chemistry. Reaction conditions are mild (aqueous, room temperature, open to atmosphere, weak or no base) yet reaction turnovers are comparable to those of more demanding literature accounts.

Visible-light Aerobic Oxidation of Benzyl Alcohol over Porphyrin-sensitized Titanium Dioxide Photocatalysts

Visible-light Aerobic Oxidation of Benzyl Alcohol over Porphyrin-sensitized Titanium Dioxide Photocatalysts

Aerobic, Efficient, Mild, and Heterogeneous Oxidation of Benzylic Alcohols Based on α-MnO2/GO Nanocatalyst

Aerobic, Efficient, Mild, and Heterogeneous Oxidation of Benzylic Alcohols Based on α-MnO2/GO Nanocatalyst