Selective Oxidation Of Alcohols Research Articles

Visible-light-induced aerobic oxidation of alcohols to aldehydes/ketones via solvated dispersion intermediates

Visible-light-induced fast and selective aerobic oxidation of alcohols to aldehydes/ketones with HBr as a mediator in ethyl acetate enables high selectivity (up to 99%) and high conversion (up to 97%) for a broad range of alcohols.

Ni-Fe bimetallic catalysts with high dispersion supported by SBA-15 evaluated for the selective oxidation of benzyl alcohol to benzaldehyde.

A wetness impregnation method was used to impregnate the substrate with a substantial quantity of oleic acid together with a metal precursor, leading to significantly dispersed Ni-Fe bimetallic catalysts based on mesoporous SBA-15. Using a wide variety of characterization methods, such as XRD, BET, and TEM Analysis, the physiochemical properties of the catalyst were determined. The addition of the metal does not have any effect on the structural characteristics of the SBA-15 catalyst, as validated by transmission electron microscopy (TEM), which shows that the prepared SBA-15 supported catalyst has a hexagonal mesoporous structure. The catalytic capabilities of the Ni-Fe-SBA-15 catalysts were evaluated in the conversion of BzOH using tert-butyl hydroperoxide (TBHP) as an oxidant and acetonitrile as a solvent. The Ni/Fe-SBA-15 (NFS-15) catalytic composition is the best of the developed catalysts, with a maximum conversion of 98% and a selectivity of 99%. In-depth investigations were conducted into the molar ratio of TBHP to BzOH, the dosage of the catalyst, the reaction rate, temperature, and solvent. The recycling investigations indicate that the synthesized Ni/Fe-SBA-15 (NFS-15) catalyst seems to be more durable up to seven successive cycles.

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.

Metal–organic framework-catalyzed selective oxidation of alcohols and oxidative cross-coupling for C–C and C–N bond-forming reactions

A novel porous metal–organic framework Co(btc)(bpy) (Co-MOF-3a) was synthesized by employing a bipyridyl ligand, benzene tricarboxylic acid, and Co(NO3)2·6H2O and was completely characterized.

Medium entropy alloy wavy nanowires as highly effective and selective alcohol oxidation reaction catalysts for energy-saving hydrogen production and alcohol upgrade

Medium entropy alloy wavy nanowires as highly effective and selective alcohol oxidation reaction catalysts for energy-saving hydrogen production and alcohol upgrade

Defective Auδ−-Ov interfacial sites boost C-H bond activation for enhanced selective oxidation of amino alcohols to amino acids

Designing efficient active sites to facilitate the oxidation of hydroxyl group to carboxylic acid under the influence of nitrogen-containing functional groups is worth exploring, but it is rarely investigated. Herein, we construct defective Au-ZrO2 interfacial structures by tuning the calcination temperature of ZrO2 support to boost the oxidation of amino alcohols to amino acids. Interestingly, the modification of calcination temperature induces the escape of saturated coordination oxygen atoms in ZrO2 support, leaving behind abundant surface oxygen vacancy (Ov). The as-formed Auδ−-Ov interfacial site displays the unique synergistic adsorption effect and electron transfer ability. Specifically, the Ov site voluntarily adsorbs the –NH2 group of amino alcohol, thus ensuring that the electron-rich Auδ− nearby Ov site adsorbs the hydroxyl groups and activates the C-H bond activation of NH2CH2CH2O* intermediates. Consequently, Au/ZrO2-600 catalyst with more defective Auδ−-Ov interfacial sites exhibits 98.8 % product yield for the oxidation of diethanolamine to iminodiacetic acid at only 30 °C. The catalyst system is further extended to the oxidation of other amino alcohols, involving monoethanolamine and triethanolamine, to their corresponding amino acids with excellent catalytic performance.

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.

Construction of synergistic active sites on MoS2 basal plane by interfacing with C60 derivative for enhanced photocatalytic hydrogen evolution coupled with biomass alcohol conversion

As a promising alternative to platinum, molybdenum disulfide (MoS2) is widely utilized as catalyst/co-catalyst in hydrogen evolution reaction (HER). However, its inactive basal plane greatly hampers its catalytic activity. Herein, we propose a function-oriented strategy to enhance the catalytic activity of MoS2 by interfacing with fullerene derivatives, specifically indene-C60 bisadduct (ICBA). The ICBA-MoS2 hybrid was then employed as an efficient co-catalyst, in conjunction with CdS, to construct a photocatalyst for solar-driven hydrogen production coupled with the selective oxidation of furfural alcohol (FOL) to furfural (FAL). The optimized 5 % ICBA-MoS2/CdS (5 %-IMC) sample exhibits a remarkable H2 and FAL production rates of 978 and 1160 μmol h−1 g−1, respectively, which was 2.4 times higher than that of the primitive sample without ICBA modified. This prominent catalytic performance can be attributed to the high activity of synergistic active sites in ICBA-MoS2, as well as the speed transportation and separation of the photogenerated charges from CdS to ICBA-MoS2, as evidenced by both experimental and theoretical investigations.

CFD modeling and simulation of benzyl alcohol oxidation coupled with hydrogen production in a continuous-flow photoelectrochemical reactor

Various conversion routes of biomass and its derivative compounds into high-value products has attracted attention from researchers recently. Among these, a solar-driven photoelectrochemical (PEC) oxidation approach of biomass alcohols to aldehydes is particularly of great interest for the potential applications because the reaction is selective and simultaneously accompanied with hydrogen production. Here, we propose a simulation of selective oxidation of benzyl alcohol into benzaldehyde coupled with hydrogen production in a 2-dimensional continuous-flow PEC reactor using COMSOL Multiphysics (5.6). In order to develop and fabricate a simple yet efficient reactor for a practical use, it is crucial to investigate the effects of operating and design parameters of the reactor on the reactions. Our studies demonstrated that the main contributions to product formation were the electrolyte flow velocity and the width of electrolyte channels. The optimized design parameter exhibited good photoelectrochemical performance with uniform potential distribution within the channels which served diffusion of neutral and charged species and electrochemical reaction. The maximum conversion of benzyl alcohol in this work was 48.25% with 100% selectivity of benzaldehyde. These findings are key for the design of the continuous-flow PEC reactor that can be applied to any series of biomass conversion reactions under mild conditions.

Exploring Thermomyces lanuginosus Lipase (TLL)‐PdNPs Nanohybrid as Suitable Catalyst for One‐pot Synthesis of Bis(3‐indolyl)phenylmethane

AbstractPalladium nanohybrids were synthesized and applied to the one‐pot synthesis of bis(3‐indolyl)methanes by selective C−C bond reaction from benzyl alcohol and indole. A T. lanuginosus lipase‐palladium nanoparticles hybrid (Pd@TLL) was synthesized, yielding PdNPs with an average diameter size of 5 nm. This heterogeneous catalyst was first tested in the selective oxidation of benzyl alcohol to benzaldehyde in different solvents. Then, the direct formation of bis(3‐indolyl)methane, by in situ oxidation and C−C coupling, was successfully evaluated under different conditions, obtaining >99 % conversion at 80 °C in toluene, with a TOF value of 9 min−1 and 89 % in pure water, demonstrating the versatility of these biohybrids.

Decorating CdS with cobaltous hydroxide and graphene dual cocatalyst for photocatalytic hydrogen production coupled selective benzyl alcohol oxidation

Coupling photocatalytic H2 evolution with benzyl alcohol (BA) oxidation to benzaldehyde (BAD) reaction allows the full utilization of the energy of light-induced electron and hole to produce fuel and valuable chemicals, which has received widespread attention recently. Herein, Co(OH)2 nanosheet array-graphene(GR) composites cocatalyst can be successfully synthesized by simple precipitation method, and then CdS nanoparticles are in situ grown in hybrid cocatalyst to finally obtain CdS-Co(OH)2-GR ternary photocatalysts. Composting of dual-cocatalyst with CdS facilitates the migration of photoinduced charge carriers of CdS, affords abundant active sites and makes the growth of CdS nanoparticles more uniform and dispersed. As a result, the CdS-Co(OH)2-GR ternary composites have shown a glorious performance, showing the H2 generation velocity of 1173.53 µmol h−1 g−1, and the conversion rate of benzyl alcohol has reached 100 % within 2 h, which has surpassed other prepared samples and most of analogous photocatalyst systems. We are confident that this study can supply a useful reference for the synthesis of dual-cocatalyst-modified semiconductor composites, and promote the development of photocatalytic coupling reaction system, in which sacrifice agents are free and energies of light-induced electron and holes can be fully utilized.

Effect of ethylene glycol chelated on ultrathin TiO2(B) nanosheets on the photocatalytic selective benzyl alcohol oxidation

The two-dimensional (2D) photocatalysts have been paid intensive attention in catalysis due to their excellent activity, which was greatly improved by the higher exposure of active sites and a facile reaction platform, and the separation efficiency of charge carriers. Herein, TiO2(B) nanosheets, which were synthesized via solvothermal method in ethylene glycol, could photocatalytically oxidize benzyl alcohol to benzaldehyde with high selectivity. The study revealed that the material's photocatalytic performance is highly influenced by the surface-chelated ethylene glycol. The pristine TiO2(B) was effective in selectively photocatalytic oxidizing benzyl alcohol, achieving a 94.5 % conversion, while the conversion decreased to 55 % after the elimination of the surface ethylene glycol. The presence of ethylene glycol on the surface of TiO2(B) nanosheets benefits the transfer of photogenerated charge carriers and improves charge separation efficiency. It is favorable for the selective formation of singlet oxygen (1O2) species, which results in enhanced photocatalytic activity and selectivity. We believe that our findings can shed light on the importance of the surface species and properties of photocatalysts in photocatalysis, and pave an avenue for the design and preparation of high-efficiency photocatalysts with unique surface properties.

Vanadia Catalysts Supported on Carbon Nitride for Selective Oxidation of Benzyl Alcohol Under Atmospheric Oxygen

Vanadia Catalysts Supported on Carbon Nitride for Selective Oxidation of Benzyl Alcohol Under Atmospheric Oxygen

Microenvironment tailoring mediated oxygen-vacancy defect engineering strategy facilitating O2 and alcohol activation on HEOs with superior catalytic efficiency

Achieving selective oxidation of biomass-derived benzyl alcohol under a mild environment to prepare high-value-added oxygenates is an attractive goal but remains a significant challenge in the absence of qualifying catalysts. Herein, we propose a microenvironment modulation mediated oxygen-vacancy defect engineering for piloting the benzyl alcohol oxidation on catalyst MW-HEO. Collective characterizations indicate that the contemporary tactic can modulate the catalyst's pore structure and surface electronic states and form massive oxygen vacancies. Both density functional theory (DFT) simulations and experimental results conclusively reveal that the oxygen vacancies contribute to the O2 activation and forming active radicals, thus facilitating the deeper reactant activation and enabling the subsequent oxidation reactions to proceed feasibly. This work lays a solid foundation for microenvironment regulation-mediated oxygen vacancy defect engineering for the high-efficiency oxidation catalysis of benzyl alcohol and a series of alcohol derivatives.

Synthesis of hollow shell TiO2 nanostructures enclosing Au nanoparticles and evaluation of their photoelectrocatalytic activity

Titania hollow shell structures enclosing Au nanoparticles (NPs) Void@Au@TiO2 were synthesized and applied for photoelectrochemical and chemical catalysis. SiO2 nanospheres were first synthesized to be used as templates for the nanostructures. These SiO2 nanospheres were then functionalized with gold nanoparticles (Au NP) using a bifunctional linker APTES [(3-Aminopropyl)triethoxysilane]. A titania coating was carried out on these Au-decorated SiO2 spheres, followed by calcination to enhance the crystallinity of these SiO2@Au@TiO2 structures. Thereafter, the SiO2 template was etched out using NaOH leaving behind Au NPs encapsulated in TiO2 hollow shell nanospheres Void@Au@TiO2. These structures were characterized by using TEM, XRD, UV–Vis-DRS, Raman and FTIR spectroscopy. The catalytic activity was evaluated using the selective oxidation of 4-methoxy benzyl alcohol as a test reaction. Further the photo-electrocatalytic activity of these nanostructures was evaluated.

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.

Halogen-Site Regulation in Cs3Bi2X9 Quantum Dots for Efficient and Selective Oxidation of Benzyl Alcohol Driven by Solar Light.

Sluggish charge kinetics and low selectivity limit the solar-driven selective organic transformations under mild conditions. Herein, an efficient strategy of halogen-site regulation, based on the precise control of charge transfer and molecule activation by rational design of Cs3Bi2X9 quantum dots photocatalysts, is proposed to achieve both high selectivity and yield of benzyl-alcohol oxidation. In situ PL spectroscopy study reveals that the Bi─Br bonds formed in the form of Br-associated coordination can enhance the separation and transfer of photoexcited carriers during the practical reaction. As the active center, the exclusive Bi─Br covalence can benefit the benzyl-alcohol activation for producing carbon-centered radicals. As a result, the Cs3Bi2Br9 with this atomic coordination achieves a conversion ratio of 97.9% for benzyl alcohol and selectivity of 99.6% for aldehydes, which are 56.9- and 1.54-fold higher than that of Cs3Bi2Cl9. Combined with quasi-in situ EPR, in situ ATR-FTIR spectra, and DFT calculation, the conversion of C6H5-CH2OH to C6H5-CH2* at Br-related coordination is revealed to be a determining step, which can be accelerated via halogen-site regulation for enhancing selectivity and photocatalytic efficiency. The mechanistic insights of this research elucidate how halogen-site regulation in favor of charge transfer and molecule activation toward efficient and selective oxidation of benzyl alcohol.

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.

Icosahedral AuPd/carbonized poly-dopamine sphere@TiO2 yolk-shell nano-photoreactor for plasmon-enhanced catalytic activity and stability

Icosahedral AuPd bimetallic nanoparticles exhibit the localized surface plasmon resonance effect with their excellent thermocatalytic activity. However, the nanoparticle aggregation and recovery difficulty challenge the widespread adoption. In this work, we designed and fabricated a yolk-shell structured icosahedral AuPd/carbonized poly-dopamine sphere@titanium dioxide (I-AuPd/C-PDA@TiO2), which exhibited excellent catalytic performance towards photocatalytic selective oxidation of benzyl alcohol (BA). Specifically, the introduction of C-PDA not only improved the chemical stability of AuPd nanoparticles but also promoted electron transfer. Meanwhile, the controlled growth of monodisperse icosahedral AuPd benefited the selective oxidation of BA due to the LSPR effect. Compared to yolk-shell Pd/C-PDA@TiO2, Au/C-PDA@TiO2 and spherical AuPd/C-PDA@TiO2 (S-AuPd/C-PDA@TiO2) photocatalysts, I-AuPd/C-PDA@TiO2 showed the highest catalytic performance with 96.0% conversion rate and 99% selectivity in 6 h under an O2-saturated reaction environment. Moreover, no obvious performance decay was observed with I-AuPd/C-PDA@TiO2 after five successive cycles, confirming the outstanding stability of I-AuPd/C-PDA@TiO2. The current strategy would be a significant contribution of AuPd bimetallic nanocrystals for plasmon-enhanced catalysis.

Single-Atoms on Crystalline Carbon Nitrides for Selective C─H Photooxidation: A Bridge to Achieve Homogeneous Pathways in Heterogeneous Materials.

Single-atom catalysis is a field of paramount importance in contemporary science due to its exceptional ability to combine the domains of homogeneous and heterogeneous catalysis. Iron and manganese metalloenzymes are known to be effective in C─H oxidation reactions in nature, inspiring scientists to mimic their active sites in artificial catalytic systems. Herein, a simple and versatile cation exchange method is successfully employed to stabilize low-cost iron and manganese single-atoms in poly(heptazine imides) (PHI). The resulting materials are employed as photocatalysts for toluene oxidation, demonstrating remarkable selectivity toward benzaldehyde. The protocol is then extended to the selective oxidation of different substrates, including (substituted) alkylaromatics, benzyl alcohols, and sulfides. Detailed mechanistic investigations revealed that iron- and manganese-containing photocatalysts work through a similar mechanism via the formation of high-valent M═O species. Operando X-ray absorption spectroscopy (XAS) is employed to confirm the formation of high-valent iron- and manganese-oxo species, typically found in metalloenzymes involved in highly selective C─H oxidations.