Oxidation Of Aromatic Alcohols Research Articles

Sub-nanometric ruthenium clusters prepared by solid-state dispersion for catalytic selective aerobic oxidation of aromatic alcohols

The selective aerobic oxidation of alcohols to corresponding aldehydes is one of the most important challenges in the green chemical industry. In this work, Ru/Al2O3-SSD catalyst with highly dispersed metallic ruthenium clusters (average particle size of 0.97 nm) was prepared by solid-state dispersion (SSD) for efficient selective aerobic oxidation of aromatic alcohols to aldehydes. Compared with the counterpart catalyst Ru/Al2O3-IM prepared by wet impregnation (IM), this catalyst has smaller metal particles (0.97 nm vs. 3.4 nm), resulting in a special electronic structure, and exhibits much higher TOF (234 h−1 vs. 98 h−1) in the aerobic oxidation reaction of benzyl alcohol at 80 °C. The catalyst also shows excellent catalytic activity in the preparation of vanillin by selective aerobic oxidation of vanillyl alcohol at 100 °C, delivering a vanillin yield of 99%. The solid-state dispersion strategy provides an efficient and facile way for the fabrication of high-performance sub-nanometric metal catalysts.

Ceria nanocatalyst-supported oxidative organic transformations of aromatic alcohols and p-nitrotoluene

Hydrothermally derived nanocubes of CeO2(10 nm) were explored as an efficient heterogeneous catalyst in the partial oxidation of aromatic alcohols to the corresponding aldehydes and aerobic oxidation ofp-nitrotoluene top-nitrobenzoic acid. The CeO2nanocatalyst was characterized by x-ray diffraction, transmission electron microscopy (TEM), energy dispersive spectroscopy, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis and ultraviolet-visible spectroscopy. TEM/high-resolution TEM micrographs reveal a morphology of mostly cubic nanostructures with exposed highly active {100} and {110} facets. The surface area of nanoceria was determined by BET analysis and found to be 33.8 m2g-1. To demonstrate the universality of the catalytic system, the selective oxidation of different substrates of benzylic alcohol and complete oxidation ofp-nitrotoluene was investigated under mild conditions. Absolute selectivity towards their respective aldehydes was found to be 99.50% (benzaldehyde), 90.18% (p-chlorobenzaldehyde), 99.71% (p-nitrobenzaldehyde), 98.10% (p-fluorobenzaldehyde), 94.66% (p-anisaldehyde) and 86.14% (cinnamaldehyde). Moreover, the catalytic oxidative transformation of nitrotoluene results in 100% conversion with 99.29% selectivity towards nitrobenzoic acid.

Metal-free, light assisted integrated CO2 reduction coupled with selective oxidation of alcohols under visible light irradiation

An integrated CO2 photoreduction to CO by photo-induced electrons coupled with selective oxidation of aromatic alcohols to carbonyl compounds by photo-generated holes using metal-free anthraquinone (AQ) as an organo-photocatalyst under visible illumination is described. The maximum conversion of benzyl alcohol to benzaldehyde was 65.6% with a selectivity of 98 %, accompanied with the CO yield in gaseous phase 8.67 μmol h−1 g.−1 DFT calculations indicated that initial binding of benzyl alcohol with AQ formed an intermediate IM1 that subsequently interacted with CO2 to give CO2 anion with a free energy change of 0.24 eV. Further, the reduction of CO2 accompanied with the oxidation of benzyl alcohol provided CO and benzaldehyde, respectively along with the release of a water molecule. This concerted metal-free photocatalytic system offers the efficient use of electron-hole pairs for organic synthesis coupled with the CO2 conversion in a cost-effective and sustainable manner.

Research on the design and application of efficient catalysts based on interfacial chemistry: Molecular catalysts in gas-liquid mixed systems

Major challenges existing in the photocatalytic gas-liquid mixing system model include the mass transfer limit at the gas-liquid interface and the depth of light penetration. For this purpose, amphiphilic molecular catalysts were prepared by monovacancy phosphomolybdate modified by propyltrimethoxysilane. It is also used as a photocatalyst in the model reaction (molecular oxygen oxidation of aromatic alcohol). The amphiphilic molecular catalyst in the reaction is similar to surfactant behavior, not only can adsorb in the gas-liquid interface, ensure the direct contact between oxygen, catalyst and reactants, improve the efficiency of mass transfer, and also reduce the surface tension of aromatic alcohol, gas-liquid-solid three-phase system into foam system. The formed foam system amplifies the interface area of the reaction, enhances the light penetration depth and significantly promotes the reaction rate. The insights gained from our study provide a new perspective on the design of photocatalysis in a gas-liquid hybrid system.

A green and pollution-free heterogeneous ruthenium catalyst anchoring on magnetic nanoparticles with FPBA and DTPA groups for oxidation of aromatic alcohols

Using ruthenium chloride as catalyst precursor, magnetic silicon spheres as support, 4-formylphenylboronic acid and ethylenediaminepentaacetic acid as functional ligands, a magnetic heterogeneous nano-ruthenium catalyst (Fe3O4@SiO2-FPBA-DTPA-Ru) was prepared for the first time. It was nano level with 20.17 emu/g saturation magnetic strength and thermal stability under 249.63 °C. Fe3O4@SiO2-FPBA-DTPA-Ru contained 0.38 mmol/g Ru and was successfully used to catalyze the oxidation reactions of 15 aromatic secondary alcohols. Results proved that Fe3O4@SiO2-FPBA-DTPA-Ru as catalyst had good catalytic activity for the oxidation of secondary aromatic alcohols with yields exceeding 90 % for 12 products and 95 % for 10 products. High TON and TOF values (6386 and 9158 h−1) in 1-phenylethanol oxidation were obtained. All the reactions of aromatic alcohols were carried out in a solvent-free system, so the prepared catalyst had the characteristics of green and pollution-free. It was’nt suitable for oxidation of aromatic primary alcohols. If there was steric hindrance around the hydroxyl group in substrate, the catalysis also may be limited. The Fe3O4@SiO2-FPBA-DTPA-Ru catalyst also exhibited the advantages of energy saving, satisfactory reusability and stability in 9 consecutive runs. It showed great potential for future large-scale industrial production.

Efficient Photocatalytic Partial Oxidation of Aromatic Alcohols by Using ZnIn2S4 under Green Conditions.

The ternary chalcogenide ZnIn2S4 (ZIS) has been synthesized by a simple hydrothermal method in which the carcinogen thiacetamide, universally used as a precursor, has been, for the first time, replaced successfully with the harmless thiourea. ZIS has been used as photocatalyst for the partial oxidation of different aromatic alcohols to their corresponding aldehyde in water solution, under ambient conditions and simulated solar light irradiation. The photocatalytic performance of ZnIn2S4 was better than TiO2 P25. In the presence of ZIS for 4-methoxybenzyl alcohol, piperonyl alcohol, and benzyl alcohol, a selectivity towards the corresponding aldehyde of 99 % for a conversion of 46 %, 75 % for a conversion of 81 %, and 87 % for a conversion of 25 %, respectively, was obtained. For the same alcohols a selectivity of 19 % for a conversion of 41 %, 19 % for a conversion of 13 %, and 16 % for a conversion of 26 %, was observed in the presence of TiO2 P25.

Facile interfacial synthesis of thin AuPd alloy nanowires for plasmon-enhanced selective photocatalytic oxidation of benzyl alcohol

Bimetallic AuPd plasmonic photocatalyst is a promising candidate for catalyzing selective oxidation of aromatic alcohol. However, developing a simple one-step method for the preparation of free-standing AuPd nanostructures with excellent photocatalytic performance remains a huge challenge. Here, a facile liquid–liquid interface route was exploited to one-pot prepare free-standing AuPd alloy nanowires (NWs) under mild conditions. Specifically, Au1Pd1 NWs are grown via oriented attachment at chloroform-water interface and 40 °C with Na2PdCl4 and HAuCl4 as precursors and 1-naphthol as reductant. Au1Pd1 NWs possess many advantages, such as thin diameter (4.0 nm), large aspect ratio, abundant defects and strong Au-Pd electronic interaction. During benzyl alcohol oxidation to benzaldehyde, Au1Pd1 NWs exhibit excellent photocatalytic activity and durability. At 40 min of visible light illumination, 98 % conversion of benzyl alcohol and 100 % selectivity to benzaldehyde are finished. After five cycles, Au1Pd1 NWs still maintain high photocatalytic activity. Compared to pure Au NWs, alloying Pd with Au in Au1Pd1 NWs dramatically enhances photocatalytic activity. The results indicate that the generated abundant •O2– under illumination play an important role in significantly improving benzyl alcohol oxidation to benzaldehyde.

Effective Proficiency of Manganese Porphyrins as Catalysts in Chemical Transformations: A Review

: Porphyrin ligands are well-known for their promising tendency to produce metal porphyrin complexes of great significance. Out of different metal porphyrins, manganese porphyrins are one of the most valuable metal porphyrins due to effective catalytic performance and potential in many reactions like C-H isocyanation, the cycloaddition of CO2 with epoxides, epoxidation, oxygen reduction reaction, depolymerization reactions, oxidation of aromatic alcohols, selective oxidation of cycloalkenes/ alkanes, aliphatic C-H chlorination, dehydrogenation of alcohols, dye degradation, BSA nitration and others. Hence, in this review, the authors have best tried to present an effective insight overview of these aforementioned applications with the help of some recent studies for signifying the value of manganese porphyrins as a competent catalyst.

Soft-templating synthesis of mesoporous MnSiOx composites as catalytic supports for Pd nanoparticles towards solvent-free oxidation of benzyl alcohol under atmospheric pressure O2

Solvent-free and liquid-phase selective oxidation of aromatic alcohols using O2 as an oxidant is a green strategy for the synthesis of aromatic aldehydes and other carbonyl compounds. Wherein, the design and preparation of heterogeneous catalysts with high activity and selectivity is a hot topic in this process. Herein, a series of manganese oxide-silica (MnSiOx) composites were synthesized using cetyltrimethylammonium bromide as a soft template. During the preparation process, the amounts of tetraethyl orthosilicate and ammonia and the calcination temperature significantly affected the textural properties and Mn cation distributions of MnSiOx. The MnSiOx composites were then employed as catalysts for Pd nanoparticles. In the solvent-free and atmospheric conditions, Pd/MnSiOx materials showed high catalytic conversions of benzyl alcohol (BZA), and the catalytic activity thereof is related to the fractions of Pd0 and Mn3+. As the reaction time and temperature are 4 h and 90 °C, the conversion of BZA (feeding dosage: 4 mL) and the selectivity of benzaldehyde are 64.8 % and 94.9 %, respectively. The catalyst can be reused at least five times without any significant loss of activity. Furthermore, the correlation between physiochemical properties and catalytic activity of Pd/MnSiOx was analyzed.

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.

Tailoring Charge Separation in ZnIn2S4@CdS Hollow Nanocages for Simultaneous Alcohol Oxidation and CO2 Reduction under Visible Light.

Artificial photosynthesis provides a sustainable strategy for producing usable fuels and fine chemicals and attracts broad research interest. However, conventional approaches suffer from low reactivity or low selectivity. Herein, we demonstrate that photocatalytic reduction of CO2 coupled with selective oxidation of aromatic alcohol into corresponding syngas and aromatic aldehydes can be processed efficiently and fantastically over the designed S-scheme ZnIn2S4@CdS core-shell hollow nanocage under visible light. In the ZnIn2S4@CdS heterostructure, the photoexcited electrons and holes with weak redox capacities are eliminated, while the photoexcited electrons and holes with powder redox capacities are separated spatially and preserved on the desired active sites. Therefore, even if there are no cocatalysts and no vacancies, ZnIn2S4@CdS exhibits high reactivity. For instance, the CO production of ZnIn2S4@CdS is about 3.2 and 3.4 times higher than that of pure CdS and ZnIn2S4, respectively. More importantly, ZnIn2S4@CdS exhibits general applicability and high photocatalytic stability. Trapping agent experiments, 13CO2 isotopic tracing, in situ characterizations, and theoretical calculations reveal the photocatalytic mechanism. This study provides a new strategy to design efficient and selective photocatalysts for dual-function redox reactions by tailoring the active sites and regulating vector separation of photoexcited charge carriers.

Integrating NiFe bimetal sites into a conjugated microporous polymer for boosting photocatalytic selective aromatic alcohol oxidation

A conjugated porous polymer metalated with Ni and Fe sites (NiFe-CMP) has been rationally designed and synthesized, exhibiting excellent photocatalytic activity and selectivity in the oxidation of aromatic alcohols under visible light irradiation.

Atomically Dispersed Co on N-Doped Porous Carbon for the Highly Efficient Catalytic Oxidation of Aromatic Alcohols to Acids and Nitriles

Atomically Dispersed Co on N-Doped Porous Carbon for the Highly Efficient Catalytic Oxidation of Aromatic Alcohols to Acids and Nitriles

Fe-Ni bimetallic supported on mordenite catalyst for selective oxidation of veratryl alcohol in a continuous reactor

Veratryl alcohol (VA) is preferentially oxidized to veratraldehyde (VADE) using a heterogeneous catalyst, which is more favoured in industries. Commercial mordenite (Ca,Na2,K2) Al2Si10O24·7H2O) was desilicated with NaOH and loaded with nickel and iron bimetal by the wet impregnation method. The synthesised Mordenite-Fe(5 %)/Ni(5–20 %) bimetallic catalyst, possessing active Bronsted acid sites, was employed to selectively oxidize the veratryl alcohol reaction. FT-IR, XRD, BET, HR-SEM, HR-TEM, and TPD were employed to determine the catalyst's textural attributes, morphology, chemical properties, and stability. Selective oxidation was performed over the catalysts using TBHP as an oxidant in a continuous reactor. To examine the most active catalyst among the four and to maximise the conversion and yield, the reaction conditions are optimised for various reaction parameters The reaction conditions were optimized by attaining 100 % conversion at temperature (90° C) for time (2 hr) and a maximum conversion of 97 % and a selectivity of 99 % at 10 bar pressure, WHSV (1.0 h−1) with acetonitrile solvent. The result of the study display that Fe (5 %) and Ni(15 %) impregnated on mordenite exhibits excellent catalytic stability with conversion (100 %) and selectivity (99 %) among the other catalysts. During regeneration, the conversion rate declined from 99.5 to 92.4.7 % and selectivity declined from 100 % to 96.2 % at the end of the seventh cycle. The high selectivity and stability of MOR-Fe(5 %)/Ni(15 %) imply that they might function properly as appropriate catalysts for the oxidation of aromatic alcohols. The advantages of the current synthesis are its cost-efficiency and eco-friendliness.

Biomimetic Solar Photocatalytic Reactor for Selective Oxidation of Aromatic Alcohols with Enhanced Solar‐Energy Utilization

AbstractLow utilization of solar energy remains a challenge that limits photocatalytic efficiency. To address this issue, this work proposes a bionic solar photocatalytic reactor (BSPR) for efficient selective oxidation of aromatic alcohols. A biomimetic phototropic hydrogel is prepared by coupling chlorine‐doped polypyrrole (Cl‐PPy) and poly(N‐isopropyl acrylamide) (PNIPAm) to maximize light‐harvesting efficiency automatically, allowing the BSPR to maintain high catalytic levels throughout the day. Molecular dynamics simulations are used to unveil the understanding of the fast photoresponsive behavior of Cl‐PPy/PNIPAm from a molecular level, while COMSOL simulations are conducted to follow the macroscopically phototropic mechanism of BSPR. Attributing to the existence of PdS/S vacancies riched ZnIn2S4 nanocomposite in the top flower‐shaped hydrogel, the BSPR displays a special function for efficiently photocatalytic oxidation of aromatic alcohols under solar illumination (yield of 4‐methoxybenzaldehyde: 479.5 µmol g−1 h−1; selectivity: 68.8%). Two possible reaction pathways are identified as follows: photogenerated holes can attract aromatic alcohols directly and generate aromatic aldehydes; photoexcited electrons oxidize O2 to ·O2− can also react with the adsorbed aromatic alcohol. This study presents a promising paradigm that explores opportunities for enhanced utilization of light energy, offering a novel approach to maximize its efficiency in practical applications.

Some sulphur - containing double combination reagents

Research and development of new reagents are very important for organic synthesis. In recent years, some new reagents with universal applicability have been reported, but new reagents of sulphur-containing are rarely reported. Wang’s group has developed several new sulphur-containing reagents which are called as Wang reagents: Sodium dithionite - tert-Butyl hydroperoxide (Na2S2O4-TBHP). The paper presents the reactions involved in the reagents obtaining and the associated mechanisms. Na2S2O4-TBHP is a new reagent for selective oxidation of aromatic alcohols to aldehydes. Wang reagents have universal applicability in organic synthesis.

Cooperation of ultrathin bowl-shaped scaffolds and oxygen vacancies promoting selective photo-oxidation of aromatic alcohols on layered oxyhalide PbBiO2Cl

Photocatalytic selective oxidation of aromatic alcohols into value-added chemicals has attracted increasing attention. Yet most processes suffer from sluggish charge kinetics, weak O2 affinity, low conversion efficiency and selectivity, which restrict their practical development. Herein, PbBiO2Cl ultrathin bowls (UBs) with rich oxygen vacancies (ROV) were initially fabricated via a combined microemulsion method and in-situ reduction process. The ultrathin bowl-shaped geometry and rich OVs effectively boost light absorption and charge separation. Theoretical results indicate the OVs on PbBiO2Cl not only generate abundant localized electrons, but also afford strong interfacial covalent bonds between O2 and OVs, which can act as atomic-level electron transfer highway and effectively promote the O2 adsorption and activation. As a result, ROV-PbBiO2Cl UBs show a 5.2-fold enhanced activity for aerobic oxidation of alcohols to aldehydes relative to PbBiO2Cl nanoplates (NPs). This work may inspire the design of more open hollow scaffolds with defect engineering for artificial photosynthesis.

Photothermal synergistic catalytic reactions: g-C3N4 assisted CeO2 for efficient selective aromatic alcohol oxidation

This paper investigates the enhanced effect of photothermal synergistic catalytic reactions and demonstrates this effect using CeO2 as an example. The experimental results demonstrate that CeO2 exhibits remarkable ability to efficiently harness both light and thermal energy for catalytic reactions, which can achieve the enhanced effect of photothermal synergistic catalytic reaction. The effect of photothermal co-catalysis is significantly greater than the simple algebraic sum of photocatalysis and thermal catalysis. Furthermore, by incorporating other materials such as g-C3N4, the photothermal catalytic performance of CeO2 can be further enhanced. Specifically, under visible light irradiation and a stable temperature of 363.15 K, the yield and selectivity of 50% CeO2/g-C3N4 (50% COCN) catalyst for the oxidation of benzyl alcohol to benzaldehyde reached 56.9% and 99%, respectively. Based on characterization and theoretical calculations, a possible mechanism of photothermal co-catalysis was proposed. This study provides a new idea for the implementation of photothermal synergistic catalytic reaction and provides a reference for the design and synthesis of related materials.

Generation of Site-Selective Structural Vacancies in a Multinary Metal-Organic Framework for Enhanced Catalysis.

Generating structural vacancies in metal-organic frameworks (MOFs) by partially removing the inorganic and organic units from the scaffolds is an effective strategy to modulate the pore parameters of the extended structures. However, pore enlargement is accomplished at the cost of loss in the number of active sites in typical MOFs, since dissociations of coordination linkages to create vacancies are not site-selective. Here, we performed site-specific vacancy generation in a multinary MOF (FDM-6) by selectively hydrolyzing the weak Zn─carboxylate linkages and keeping the strong Cu─pyrazolate linkages untouched. Surface area and pore size range of the materials could be systematically tuned by adjusting the water content and hydrolysis time. More than 56% of the Zn(II) sites in FDM-6 could be vacant, as evidenced by the atom occupancy analysis using powder X-ray diffraction, while most of the redox-active Cu sites are held in the backbone. The vacancies create highly connected mesopores, thus guaranteeing facile transportation of the guest molecules toward the active sites. Compared with the pristine MOF, FDM-6 with site-selective vacancies shows enhanced catalytic activity in bulky aromatic alcohol oxidation. Overall, the multinary MOF provides a platform in which both pore size enhancement and full retainment of active sites could be delivered in one framework by simple vacancy engineering.

Ultrathin ZnIn2S4 Nanosheets-Supported Metallic Ni3FeN for Photocatalytic Coupled Selective Alcohol Oxidation and H2 Evolution

Photocatalytic anaerobic organic oxidation coupled with H2 evolution represents an advanced solar energy utilization strategy for the coproduction of clean fuel and fine chemicals. To achieve a high conversion efficiency, the smart design of efficient catalysts by the right combination of semiconductor light harvesters and cocatalyst is highly required. Herein, we report a composite photocatalyst composed of noble metal-free transition metal nitride Ni3FeN decorated on 2D ultrathin ZnIn2S4 (ZIS) nanosheets for selective oxidation of aromatic alcohols to aldehydes pairing with H2 production. In the composite, ultrathin ZIS serves as a light harvester that greatly shortens the diffusion length of photogenerated charges, while the metallic nitride Ni3FeN acts as an advanced cocatalyst which not only captures the photoelectrons generated from the ultrathin ZIS to promote the charge separation, but also provides active sites to lower the overpotential and accelerate the H2 reduction. The best photocatalytic performance is found on ZIS/1.5% M-Ni3FeN, which shows a H2 generation rate of 2427.9 µmol g−1 h−1 and a benzaldehyde (BAD) production rate of 2460 µmol g−1 h−1, about 7.8-fold as high as that of bare ZIS. This work is anticipated to endorse the exploration of transition metal nitrides as high-performance cocatalysts to promote the coupled photocatalytic organic transformation and H2 production.