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

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: The reaction was performed in an isothermal slurry batch reactor in the presence and absence of UV-light. The products were analysed using GC-FID; the deposits formed on the catalyst was analysed using TGA and FTIR. Results: 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.

Understanding contributions of zeolite surface hydroxyl groups over Au/USY in selective oxidation of aromatic alcohols

Metal-zeolites catalysts are of great importance in selective organic conversions. Zeolites possess features of highly-ordered porous network, adjustable acidic properties (Brønsted/Lewis), spatial nanoconfinement effects, unique shape selectivity and the strong (hydrothermal-) stability. The role of zeolite hydroxyl (z-OH) groups, such as bridging ones in Si-O(H)-Al (B acids) and terminal ones in Al-OH and Si-OH (silanols), in catalysis is an interesting topic, particularly when they are not catalytic active sites, while they affect the catalytic performances. This study comprehensively investigated series of Au/USY catalysts in the selective oxidation of benzyl alcohol to benzaldehyde and clarified the dominating contributions of Al-associated z-OH groups to affecting catalytic conversions and selectivity via altering the Si/Al ratio and reducing z-OH groups by amorphous silica species derived from diethoxydimethylsilane under high-temperature calcination. The catalysts were characterized by XRD, BET, TEM, XPS, UV/Vis, FT-IR and in-situ DRIFT to investigate crystal structures, textural properties, morphologies, size distribution, chemical state of gold, acidity, and adsorptive properties. The experimental results proved that zeolites with a higher amount of z-OH groups tuned by Si/Al ratios or by diethoxydimethylsilane silylation exhibited higher catalytic activity because of the adsorption effect. Finally, a possible mechanism was discussed based on the experimental results and literature.

Stabilizing BiVO4 Photoanode in Bicarbonate Electrolyte for Efficient Photoelectrocatalytic Alcohol Oxidation.

In order to expand the application of bismuth vanadate (BiVO4) to the field of photoelectrochemistry, researchers have explored the potential of BiVO4 in catalyzing or degrading organic substances, potentially presenting a green and eco-friendly solution. A study was conducted to investigate the impact of electrolytes on the photocatalysis of benzyl alcohol by BiVO4. The research discovered that, in an acetonitrile electrolyte (pH 9) with sodium bicarbonate, BiVO4 catalyzed benzyl alcohol by introducing saturated V5+. This innovation addressed the issue of benzyl alcohol being susceptible to catalysis in an alkaline setting, as V5+ was prone to dissolution in pH 9 on BiVO4. The concern of the photocorrosion of BiVO4 was mitigated through two approaches. Firstly, the incorporation of a non-aqueous medium inhibited the formation of active material intermediates, reducing the susceptibility of the electrode surface to photocorrosion. Secondly, the presence of saturated V5+ further deterred the leaching of V5+. Concurrently, the production of carbonate radicals by bicarbonate played a vital role in catalyzing benzyl alcohol. The results show that, in this system, BiVO4 has the potential to oxidize benzyl alcohol by photocatalysis.

A binary dumbbell visible light driven photocatalyst for simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde

Photocatalytic H2 production with selective oxidation of organic moieties in an aqueous medium is a fascinating research area. However, the rational design of photocatalysts and their photocatalytic performance are still inadequate. In this work, we efficiently synthesized the MoS2 tipped CdS nanowires (NWs) photocatalyst using soft templates via the two-step hydrothermal method for efficient H2 production with selective oxidation of benzyl alcohol (BO) under visible light illumination. The optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst exhibits the highest photocatalytic H2 production efficiency of 13.55 mmol g−1 h−1 with 99 % selective oxidation of BO, which was 42.34 and 2.21 times greater photocatalytic performance than that of pristine CdS NWs and MoS2/CdS NWs, respectively. The directional loading of MoS2 at the tips of CdS NWs (as compared to nondirectional MoS2 at CdS NWs) is the key factor towards superior H2 production with 99 % selective oxidation of BO and has an inhibitory effect on the photo corrosion of pristine CdS NWs. Therefore, the amazing enhancement in the photocatalytic performance and selectivity of optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst is due to the spatial separation of their photoexcited charge carriers through the Schottky junction. Moreover, the unique structure of the MoS2 flower at the tip of 1D CdS NWs offers separate active sites for adsorption and surface reactions such as H2 production at the MoS2 flower (confirmed by Pt photo deposition) and subsequently the selective oxidation of BO at the stem of CdS NWs. This rational design of a photocatalyst could be an inspiring work for the further development of an efficient photocatalytic system for H2 production with selective oxidation of BO (a strategy of mashing two potatoes with one fork).

Regulation of Catalyst Immediate Environment Enables Acidic Electrochemical Benzyl Alcohol Oxidation to Benzaldehyde.

Electrocatalytic alcohol oxidation in acid offers a promising alternative to the kinetically sluggish water oxidation reaction toward low-energy H2 generation. However, electrocatalysts driving active and selective acidic alcohol electrochemical transformation are still scarce. In this work, we demonstrate efficient alcohol-to-aldehyde conversion achieved by reticular chemistry-based modification of the catalyst's immediate environment. Specifically, coating a Bi-based electrocatalyst with a thin layer of metal-organic framework (MOF) substantially improves its performance toward benzyl alcohol electro-oxidation to benzaldehyde in a 0.1 M H2SO4 electrolyte. Detailed analysis reveals that the MOF adlayer influences catalysis by increasing the reactivity of surface hydroxides as well as weakening the catalyst-benzaldehyde binding strength. In turn, low-potential (0.65 V) cathodic H2 evolution was obtained through coupling it with anodic benzyl alcohol electro-oxidation. Consequently, the presented approach could be implemented in a wide range of electrocatalytic oxidation reactions for energy-conversion application.

Macroporous NiFe-LDH accelerating highly-selective electrosynthesis of benzaldehyde accompanied with hydrogen production

Alkaline overall water splitting (OWS) is a potential technology for hydrogen (H2) production, however, the sluggish oxygen evolution reaction (OER) with high overpotential has limited its large-scale application. Herein, we successfully prepared the macroporous NiFe layered hydroxide (M-NiFe-LDH) on self-supported carbon cloth (CC) as electrocatalyst to drive an energy-saving device for both H2 production and benzyl alcohol (BA) oxidation to synthesize benzaldehyde (BAD). By utilizing the polystyrene (PS) microsphere templates and electrodeposition technology, CC@M-NiFe-LDH can be easily obtained after removing the PS templates. Due to the synergistic effect of bimetallic NiFe-LDH and macropores arrays which can expose more catalytic active sites, CC@M-NiFe-LDH electrocatalyst only needs a low potential of 1.31 VRHE to reach the current density of 10 mA cm−2 with a high BAD selectivity (∼99 %). Consequently, an energy-saving two-electrode device with both BAD electrosynthesis and H2 production can be assembled, which needs a low cell voltage of 1.648 V and electricity consumption of 3.60 kW h per cubic meter of H2, lower than that of OWS (1.826 V and 3.99 kW h).

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.

Influence of the oxidic support material on the platinum-catalyzed benzyl alcohol oxidation

Influence of the oxidic support material on the platinum-catalyzed benzyl alcohol oxidation

Boosting photocatalytic hydrogen peroxide evolution through aerobic oxidative dehydrogenation of benzyl alcohol over amino acid hyper-cross-linked polymer in two-phase system

The fusion of photocatalytic hydrogen peroxide (H2O2) production with the generation of high-value organic compounds carries the potential to optimize the utilization of solar energy. The efficient generation and separation of products constitute indispensable elements in constructing a proficient reaction system. Herein, the photocatalytic production of H2O2 via the aerobic oxidative dehydrogenation of benzyl alcohol (BA) was realized through the application of an amino acid hyper-cross-linked polymer (H6P-HCPs) in two-phase system. The outcomes unveiled that the H6P-HCPs with 1:6 M ratio of L-phenylalanine (L-Phe) and hexaphenylbenzene (HPB) achieves the highest generation rate of H2O2 (29.26 mmol∙gcat-1∙h-1), stoichiometric amount of benzyl alcohol oxidation products were obtained as 96% benzaldehyde (23.94 mmol∙gcat-1∙h-1) and 4% benzoic acid (5.56 mmol∙gcat-1∙h-1). Time-dependent density functional theory (TDDFT) calculations illuminated that the presence of L-Phe monomers of H6P-HCPs not only facilitated electron transfer from L-Phe to HPB, capitalizing on electronegativity differentials, but also instigated the formation of O2•- while concurrently adjusting its hydrophobic nature. These factors, in concert, were instrumental in the accomplishment of this highly efficient photocatalytic process.

Perfluorinated Zinc Porphyrin Sensitized Photoelectrosynthetic Cells for Enhanced TEMPO-Mediated Benzyl Alcohol Oxidation.

This research introduces a novel series of perfluorinated Zn(II) porphyrins with positive oxidation potentials designed as sensitizers for photoelectrosynthetic cells, with a focus on promoting the oxidation of benzyl alcohol (BzOH) mediated by the 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) organocatalyst. Three dyes, CLICK-3, CLICK-4, and BETA-4, are meticulously designed to explore the impact of substituents and their positions on the perfluorinated porphyrin ring in terms of redox potentials and energy level alignment when coupled with SnO2/TiO2-based photoanodes and TEMPO mediator. A comprehensive analysis utilizing spectroscopy, electrochemistry, photophysics, and computational techniques of the dyes in solution and sensitized thin films unveils an enhanced charge-separation character in the 4D-π-1A type BETA-4. Incorporating four dimethylamino donor groups at the periphery of the porphyrin ring and a BTD-accepting linker at the β-pyrrolic position equips the structure with a more efficient donor-acceptor system. This enhancement ensures improved light-harvesting capacity, resulting in a doubled incident photon-to-current conversion efficiency (IPCE% ≃30%) in the presence of LiI compared to meso-substituted dyes CLICK-3 and CLICK-4. Sensitizing SnO2/TiO2 thin films with BETA-4 successfully promotes the photooxidation of benzyl alcohol (BzOH) in the presence of the rapid TEMPO radical catalyst, yielding photocurrents of approximately 125 μA/cm2 in an optimized TBPy/LiClO4/ACN electrolyte. Notably, when lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) replaces TBPy as the base for TEMPO-catalyzed BzOH oxidation, a remarkable photocurrent of around 800 μA/cm2 is achieved, marking one of the highest values reported for this photoelectrochemical reaction to date. This study underscores that the proper functionalization of perfluorinated zinc porphyrins positions these dyes as ideal candidates for sensitizing SnO2/TiO2 in the photodriven oxidation of BzOH. It also highlights the crucial role of carefully tuning electrolyte composition based on the electronic properties of molecular sensitizers.

Dihalosalicylaldehyde based molybdenum(VI) complexes: Synthesis, spectral characterization, crystal structures, and catalytic activities for the selective oxidation of benzylic alcohols

Three ONO donor Schiff base ligands were obtained by the condensation of 3,5-dihalosalicylaldehydes with nicotinoylhydrazide (H2Cl2SN: (E)-N'-(3,5-dichlorosalicylaldehyde) nicotinoylhydrazone, H2Br2SN: (E)-N'-(3,5-dibromosalicylaldehyde) nicotinoylhydrazone, and H2I2SN: (E)-N'-(3,5-diiodosalicylaldehyde) nicotinoylhydrazone on refluxing in ethanol. The treatment of [MoO2(acac)2] (acac = acetylacetonato) with these ligands in methanol afforded cis-dioxidomolybdenum(VI) complexes [MoO2(Cl2SN)(CH3OH)] (1), [MoO2(Br2SN)(CH3OH)] (2), and [MoO2(I2SN)(CH3OH)] (3). Various techniques like NMR (1H and 13C), FT-IR, Mass, TGA, elemental (CHN), and single-crystal X-ray diffraction analysis (for H2Cl2SN·H2O, 2a, [MoO2(Br2SN)(C2H5OH)], and 3a, [MoO2(I2SN)(H2O)].DMF) were utilized to characterize the synthesized compounds. The data collected from diffraction studies revealed that the geometry around Mo(VI) ions was distorted octahedral. Additionally, all complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide.

Radical-driven selective oxidation of benzyl alcohol on MnCoOx catalysts with no oxidant other than air in reactor

Mn reinforced Co3O4 catalysts (MnCoOx) were prepared by a facile solid phase mixed foaming method with an in-situ heating enhancement for the formation of spinel phase mixed oxide species, and studied in the selective oxidation of benzyl alcohol just the air in reactor as oxygen donor. It was found that the MnCoOx catalysts are composed of relatively minimal spinel MnCo2O4 mixed oxide and massive Co3O4 to form MnCo2O4-Co3O4 oxide pair. The micro-domains of MnCo2O4-Co3O4 oxide pair present two redox couples of Mn3+/Mn2+ and Co3+/Co2+ instead of the single one of Co3+/Co2+ in Co3O4, and then dramatically enhance the formation of superoxide radicals (•O2–) species from the O2 in air, which can efficiently initiate the conversion of benzyl alcohol to benzaldehyde in a Fenton-like processes. With no oxidant other than air in reactor, the interaction between MnCo2O4 and Co3O4 in MnCoOx catalysts leads to a benzyl alcohol conversion up to 98 % with a 100 % benzaldehyde selectivity at atmospheric pressure while single component Co3O4 can only present a benzyl alcohol conversion at 37 %. This embodiment of highly efficient heterogeneous selective oxidation just with air as oxidant provides a probability for developing a low-cost and super-facile radical-induced selective oxidation process for alcohols.

A new perspective for palladium(II)-catalyzed alcohol oxidation in aerobic means

The development of alternative and environmentally safe routes for the oxidation of primary and secondary alcohols has attracted the attention of several researchers due to the importance of these oxidized products in industries. Thereby, the oxidation of β-citronellol, geraniol, nerol, borneol, isoborneol, cinnamic alcohol, and benzyl alcohol is described herein. These reactions occurred in an aerobic environment, with or without system pressurization. Acetonitrile was the solvent used. The process was catalyzed by the bimetallic complex formed with palladium(II) acetate and copper(II) acetate, using p-benzoquinone as a cocatalyst in some reaction conditions. The applied system obtained 62.5 points on the eco-scale, with yields above 61%. Alcohol oxidation products are of great importance in industrial applications. Thus, this work presents a cleaner, more sustainable alternative to alcohol oxidations.

Versatile catalytic performance of magnetic and reusable mesoporous Co3(PO4)2 in benzyl alcohol oxidation and esterification with acetic acid

Versatile catalytic performance of magnetic and reusable mesoporous Co3(PO4)2 in benzyl alcohol oxidation and esterification with acetic acid

CuInSe2 nanoplatelets decorated CdS nanosheets as 2D-2D S-scheme photocatalyst for photocatalytic H2 generation coupled with benzyl alcohol oxidation and microplastic degradation

In this work, a novel 2D layered heterojunction for various photocatalytic reactions is constructed by hybridizing CdS nanosheets and CuInSe2 nanoplatelets. By adjusting CuInSe2 content, the CdS-16% CuInSe2 sample displays a visible-light-induced H2 production rate of 4382 μmol g−1 h−1, approximately 7.5 times higher than pristine CdS. Furthermore, CdS-16% CuInSe2 demonstrates exceptional photocatalytic activity in H2 evolution simultaneous benzyl alcohol (BA) oxidation and polyethylene terephthalate (PET) degradation. The superior photocatalytic activity is ascribed to the unique S-scheme heterojunction and 2D-2D CdS–CuInSe2 layered heterostructures that effectively separate photoinduced charge carriers and provide appropriate interfacial band structures. The photocatalytic mechanism is thoroughly examined through experiments and density functional theory calculations. This work offers a valuable platform to develop innovative layered photocatalysts that are highly effective for a wide range of photocatalytic reactions.

Guest-Regulated Generation of Reactive Oxygen Species from Porphyrin-Based Multicomponent Metallacages for Selective Photocatalysis.

The development of novel materials for highly efficient and selective photocatalysis is crucial for their practical applications. Herein, we employ the host-guest chemistry of porphyrin-based metallacages to regulate the generation of reactive oxygen species and further use them for the selective photocatalytic oxidation of benzyl alcohols. Upon irradiation, the sole metallacage (6) can generate singlet oxygen (1O2) effectively via excited energy transfer, while its complex with C70 (6⊃C70) opens a pathway for electron transfer to promote the formation of superoxide anion (O2⋅-), producing both 1O2 and O2⋅-. The addition of 4,4'-bipyridine (BPY) to complex 6⊃C70 forms a more stable complex (6⊃BPY) via the coordination of the Zn-porphyrin faces of 6 and BPY, which drives fullerenes out of the cavities and restores the ability of 1O2 generation. Therefore, benzyl alcohols are oxidized into benzyl aldehydes upon irradiation in the presence of 6 or 6⊃BPY, while they are oxidized into benzoic acids when 6⊃C70 is employed as the photosensitizing agent. This study demonstrates a highly efficient strategy that utilizes the host-guest chemistry of metallacages to regulate the generation of reactive oxygen species for selective photooxidation reactions, which could promote the utilization of metallacages and their related host-guest complexes for photocatalytic applications.

Guest‐Regulated Generation of Reactive Oxygen Species from Porphyrin‐Based Multicomponent Metallacages for Selective Photocatalysis

AbstractThe development of novel materials for highly efficient and selective photocatalysis is crucial for their practical applications. Herein, we employ the host‐guest chemistry of porphyrin‐based metallacages to regulate the generation of reactive oxygen species and further use them for the selective photocatalytic oxidation of benzyl alcohols. Upon irradiation, the sole metallacage (6) can generate singlet oxygen (1O2) effectively via excited energy transfer, while its complex with C70 (6⊃C70) opens a pathway for electron transfer to promote the formation of superoxide anion (O2⋅−), producing both 1O2 and O2⋅−. The addition of 4,4′‐bipyridine (BPY) to complex 6⊃C70 forms a more stable complex (6⊃BPY) via the coordination of the Zn‐porphyrin faces of 6 and BPY, which drives fullerenes out of the cavities and restores the ability of 1O2 generation. Therefore, benzyl alcohols are oxidized into benzyl aldehydes upon irradiation in the presence of 6 or 6⊃BPY, while they are oxidized into benzoic acids when 6⊃C70 is employed as the photosensitizing agent. This study demonstrates a highly efficient strategy that utilizes the host‐guest chemistry of metallacages to regulate the generation of reactive oxygen species for selective photooxidation reactions, which could promote the utilization of metallacages and their related host‐guest complexes for photocatalytic applications.

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.

Benzyl alcohol promoted electrocatalytic reduction of carbon dioxide and C2 production by Cu2O/Cu

Oxide-derived copper (OD-Cu)-based materials containing Cuδ+ (0 < δ ≤ 1) have been considered as promising electrocatalysts for electrochemical CO2 reduction reaction (ECO2RR) to produce valuable C2 products, which, however, suffer from poor stability, mainly due to the inevitable reduction of Cuδ+. We report here that the benzyl alcohol (BA) introduced in catholyte presents a markedly positive effect on the durability and C2 selectivity enhancement of ECO2RR when OD-Cu-based material is adopted as cathode electrocatalyst. The critical evidence of ECO2RR intermediates has been provided by in situ Raman and FTIR spectroscopy, which reveals the surface mechanisms of BA-assisted ECO2RR over OD-Cu catalysts. On the one hand, the introduction of BA increases the CO2 supply for ECO2RR by slowing down its neutralizing reaction, which results in the increased intermediate species coverage on the catalytic surface therefore the delayed self-reduction of Cuδ+; On the other hand, the interaction between BA and the intermediate species *CO during ECO2RR brings an enhanced selectivity of C2 products (FE C2 = 85.5 % at −1.38 V vs RHE). Besides, an energy-savings and economic electrolyzer can be achieved by coupling anodic BA oxidation reaction to benzoic acid and ECO2RR to C2 products with much lowered cell voltages.