Activity For Oxidation Of Alcohols Research Articles

A smart hydrogel carrier for silver nanoparticles: an improved recyclable catalyst with temperature-tuneable catalytic activity for alcohol and olefin oxidation

Radical polymerization reactions were employed to synthesize thermo-responsive poly(N-isopropylacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) hydrogels at room temperature.

Synthesis of active, robust and cationic Au25 cluster catalysts on double metal hydroxide by long-term oxidative aging of Au25(SR)18.

Synthesis of an atomically precise Au25 cluster catalyst was attempted by long-term, low-temperature aging of Au25(BaET)18 (BaET-H = 2-(Boc-amino)ethanethiol) on various double metal hydroxide (DMH) supports. X-ray absorption fine structure analysis revealed that bare Au25 clusters with high loading (1 wt%) were successfully generated on the DMH containing Co and Ce (Co3Ce) by oxidative aging in air at 150 °C for >12 h. X-ray absorption near-edge structure and X-ray photoelectron spectroscopies showed that the Au25 clusters on Co3Ce were positively charged. The Au25/Co3Ce catalyst thus synthesized exhibited superior catalytic performance in the aerobic oxidation of benzyl alcohol under ambient conditions (TOF = 1097 h-1 with >97% selectivity to benzoic acid) and high durability owing to a strong anchoring effect. Based on kinetic experiments, we propose that abstraction of hydride from α-carbon of benzyl alkoxide by Au25 is the rate-determining step of benzyl alcohol oxidation by Au25/Co3Ce.

Metal-Directed Self-Assembly of {Ti8L2} Cluster-Based Coordination Polymers with Enhanced Photocatalytic Alcohol Oxidation Activity.

Cooperative assembly of the neutral cluster {Ti8O5(OEt)18L2} (L = pyrazine-2,3-dicarboxylic acid) with different metal units of Mn(NO3)2, CuCl2, Zn(OEt)2, Cd(NO3)2, Ce(NO3)3, Lu(NO3)3, and Lu(NO3)2(OEt), or the [Cu2I2] cluster, generates a family of titanium-oxygen cluster (TOC)-based coordination polymers. These one-dimensional (1D) linear structures contain the same {Ti8L2} cluster but with variable bridging metal units. The regulation of the heterometal not only affects the chain geometries of the {MTi8} but also affects the way the 1D chains are stacked in the crystal lattice. Investigation of the catalytic activities toward alcohol oxidation demonstrated the synergetic effect of combining the metal site and the photosensitive {Ti8L2} cluster in the tailored structure. Under light illumination, the {MTi8} with dual catalytic sites shows greatly enhanced catalytic activity in the selective oxidation of alcohols to aldehydes. Because the compositions and structures of {MTi8} are highly tunable, this work spotlights the potential of utilizing such metal-bridged multidimensional Ti-oxo materials for cooperative photoredox catalysis for organic transformation.

Nano-Sized NiO Immobilized on Au/CNT for Benzyl Alcohol Oxidation: Influences of Hybrid Structure and Interface.

Tiny gold nanoparticles were successfully anchored on carbon nanotubes (CNT) with NiO decoration by a two-step synthesis. Characterizations suggested that Ni species in an oxidative state preferred to be highly dispersed on CNT. During the synthesis, in situ reduction by NaBH4 and thermal treatment in oxidation atmosphere were consequently carried out, causing the formation of Au-Ni-Ox interfaces and bimetal hybrid structure depending on the Ni/Au atomic ratios. With an appropriate Ni/Au atomic ratio of 8:1, Ni atoms migrated into the sub-layers of Au particles and induced the lattice contraction of Au particles, whilst a higher Ni/Au atomic ratio led to the accumulation of NiO fractions surrounding Au particles. Both contributed to the well-defined Au-Ni-Ox interface and accelerated reaction rates. Nickel species acted as structure promoters with essential Au-Ni-Ox hybrid structure as well as the active oxygen supplier, accounting for the enhanced activity for benzyl alcohol oxidation. However, the over-layer of unsaturated gold sites easily occured under a high Ni/Au ratio, resulting in a lower reaction rate. With an Au/Ni atomic ratio of 8:1, the specific rate of AuNi8/CNT reached 185 μmol/g/s at only 50 °C in O2 at ordinary pressure.

A TEMPO-Functionalized Ordered Mesoporous Polymer as a Highly Active and Reusable Organocatalyst.

The properties of high stability, periodic porosity, and tunable nature of ordered mesoporous polymers make these materials ideal catalytic nanoreactors. However, their application in organocatalysis has been rarely explored. We report herein for the first time the incorporation of a versatile organocatalyst, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), into the pores of an FDU-type mesoporous polymer via a pore surface engineering strategy. The resulting FDU-15-TEMPO possesses a highly ordered mesoporous organic framework and enhanced stability, and shows excellent catalytic activity in the selective oxidation of alcohols and aerobic oxidative synthesis of 2-substituted benzoxazoles, benzimidazoles and benzothiazoles. Moreover, the catalyst can be easily recovered and reused for up to 7 consecutive cycles.

Dual-Site Cooperation for High Benzyl Alcohol Oxidation Activity of MnO2 in Biphasic MnOx–CeO2 Catalyst Using Aerial O2 in the Vapor Phase

Selective oxidation of benzyl alcohol to benzaldehyde in the vapor phase has drawn growing interest recently. In this work, MnOx–CeO2 mixed oxide compositions have been prepared by a coprecipitation method and tested for their oxidation activities of benzyl alcohol to benzaldehyde in the vapor phase. Detailed structural analyses have indicated that MnOx–CeO2 catalysts contain two phases, namely, α-MnO2 and fluorite CeO2 phases. The benzyl alcohol oxidation activity of pure MnO2 is more than 7 times higher compared to that of CeO2, indicating a much higher intrinsic oxidation ability of the MnO2 phase. Further, enhancement of the benzyl alcohol oxidation rate over MnO2 in 10%MnOx–CeO2 catalyst by 13 times is observed in relation to pure MnO2. The role of CeO2 in the MnOx–CeO2 catalyst has also been investigated, which indicates that the oxidation activity is almost independent of CeO2. However, stronger adsorption of benzyl alcohol over the MnOx–CeO2 catalysts compared to that of MnO2 points to the role of CeO2 in adsorption. Thus, both the CeO2 and the MnO2 components have different roles in the catalytic process—adsorption of benzyl alcohol on the CeO2 surface and its oxidation on MnO2 at the interface. The cooperation between the two sites toward oxidation could happen due to jumping of adsorbed benzyl alcohol from the surface of the CeO2 phase to the closest Mn4+ site in the MnO2 phase at the contact surface with MnO2 by thermal motion.

Immobilization of hexamolybdate onto carbon-coated Fe3O4 nanoparticle: A novel catalyst with high activity for oxidation of alcohols

A novel core-shell structural magnetic nanocatalyst involving carbon coatings on magnetic Fe3O4 nanoparticle (Fe3O4@C) for immobilizing polyoxometalate hexamolybdate (HM), were prepared by a facile chemical approach. The catalyst was identified by various techniques such as FE-SEM, EDX, VSM, XRD, TG, TEM, and FT-IR spectroscopy. This nanocatalyst were applied in the oxidation of alcohols using tert-butyl hydroperoxide, an oxidant in acetonitrile. The oxidation product was obtained at a high yield. The new nanocatalyst showed good recoverability without any significant loss of activity within successive runs.

Pd nanoparticles supported on pyrazolone-functionalized hollow mesoporous silica as an excellent heterogeneous nanocatalyst for the selective oxidation of benzyl alcohol

Hollow mesoporous silica nanoparticles (HMSNs), by exploiting both their organo-functionalized surface and porous shell were chosen as the ideal support for the immobilization of palladium nanoparticles (Pd-NPs). The HMSNs were created by acidic removal of Fe3O4 nanoparticles from silica-coated Fe3O4 core-shell. The catalyst was prepared following surface modification of HMSNs by (3-chloropropyl)-triethoxysilane (CPTES), functionalization by pyrazolone-based ligand, and stabilization of Pd-NPs on HMSNs. The resulting catalyst was fully characterized by different analytical techniques. This new heterogeneous catalyst showed high catalytic activity and excellent selectivity in the selective oxidation of benzyl alcohols in ethanol at ambient temperature. Easy separation by centrifuge and reusability for five successive cycles without significant loss of catalytic activity were some advantages of this catalyst.

Synthesis of Fe3O4@GO Nanocomposites Modified with La2O3 Nanoparticles as an Efficient Catalyst for Selective Oxidation of Aromatic Alcohols to Aldehydes

Graphene oxide (GO)-based nanocomposites decorated with metal oxide nanoparticles are promising catalysis fields owing to their multi-component interactions. In this research, a green approach for selective oxidation of benzyl alcohols to benzaldehydes was presented using novel Fe3O4@GO-La2O3 nanocomposite for the first time. The proposed nanocomposite exhibits excellent selectivity and catalytic activity for benzyl alcohol oxidation. Apart from that, this protocol can be scaled up. Absence of toxic solvent, simple product isolation, magnetic catalyst separation, and high recoverability are remarkable advantages of this approach.

A new catalytic approach for aerobic oxidation of primary alcohols based on a Copper(I)-thiophene carbaldimines

• Novel in situ copper(I) iodide schiff base catalysts. • High activity for the aerobic oxidation of benzylic, allylic and aliphatic alcohols. • Quantitative yields for benzaldehyde in 3 h with a catalyst loading of 2.5 mol%. • Diol oxidation to the corresponding lactol. We report here novel Cu(I) thiophene carbaldimine catalysts for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to lactones or lactols. In the presence of the in situ generated Cu(I) species, a persistent radical (2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO)) and N-methylimidazole (NMI) as an auxiliary ligand, the reaction proceeds under aerobic conditions and at ambient temperature. Especially the catalytic system of 1-(thiophen-2-yl)-N-(4-(trifluoromethoxy)phenyl)methanimine (ligand L2 ) with copper(I)-iodide showed high reactivity for all kind of alcohols (benzylic, allylic and aliphatic). In the case of benzyl alcohol even 2.5 mol% of copper loading gave quantitative yield. Beside high activity under aerobic conditions, the catalysts ability to oxidize 1,5-pentadiol to the corresponding lactol (86% in 4 h) and N-phenyldiethanolamine to the corresponding morpholine derivate lactol (86% in 24 h) is particularly noteworthy.

SBA-15 Supported 1-Methyl-2-azaadamanane N-Oxyl (1-Me-AZADO) as Recyclable Catalyst for Oxidation of Alcohol.

Herein, we designed and synthesized an SBA-15 supported 1-methyl-2-azaadamanane N-oxyl (1-Me-AZADO) and investigated its catalytic performance for selective oxidation of alcohols under Anelli's conditions. The first example of immobilization of 1-Me-AZADO was very important to advance the oxgenation effectively because this supported N-oxyl has excellent catalytic activity for oxidation of alcohols to carbonyl compounds, and more importantly, it can be conveniently recovered and reused at least 6 times without significant effect on its catalytic efficiency.

Novel oxovanadium and dioxomolybdenum complexes of tridentate ONO-donor Schiff base ligand: Synthesis, characterization, crystal structures, Hirshfeld surface analysis, DFT computational studies and catalytic activity for the selective oxidation of benzylic alcohols

Two new oxovanadium and dioxomolybdenum Schiff base complexes, [VvO(L)(OCH3)(CH3OH)] and [MoVIO2(L)(CH2CH3OH)], were synthesized by treating an ONO-donor type Schiff base ligand (H2L) derived by condensation of 5-nitrosalicylaldehyde and nicotinic hydrazide with oxo and dioxo acetylacetonate salts of vanadium and molybdenum, [VO(acac)2 and MoO2(acac)2], respectively. The synthesized ligand and complexes were characterized by various spectroscopic techniques like FT-IR, multinuclear (1H, 13C) NMR, elemental analysis and the most authentic single crystal X-ray diffraction analysis. In both complexes the geometry around the central metal ions was distorted octahedral as revealed by the data collected from diffraction studies. Theoretical calculation of the synthesized compounds were carried out by DFT as well as TD-DFT using B3LYP method by employing the Def2-TZVP basis set. The findings of theoretical data indicated that the calculated results are in accordance with the experimental findings. Moreover, the catalytic efficiencies of both complexes were investigated by oxidizing the benzylic alcohols in the presence of urea hydrogen peroxide (UHP) in acetonitrile.

Recognition of Water-Induced Effects toward Enhanced Interaction between Catalyst and Reactant in Alcohol Oxidation.

Pickering emulsion stabilized by solid nanoparticles provides a diverse solvent microenvironment and enables to promote the phase transfer of reaction substrates/products in catalytic reactions, but the intrinsic role of solvent is still not clear. Herein, using benzyl alcohol (BA) as a model reactant, we demonstrate the nature of the water-promoted activity for alcohol oxidation over the Pd/MgAl-LDO catalyst. Depending on the water in the solvent, we observe different reactivities regarding the proportion of the water in the system. Kinetic isotope effects confirm the participation and positive effects of water for oxidation of BA. The water promotion effects are recognized and identified by the water vapor pulse adsorption coupled with temperature program desorption. Moreover, the adsorption behavior of BA or benzaldehyde at the interface of water and Pd/MgAl-LDO is also investigated by quasi-in-situ Raman spectroscopy. In addition, the mechanism of water-promoted alcohol oxidation is rationally proposed based on the Langmuir-Hinshelwood mechanism. The general applicability of the water promotion effects is further demonstrated over different supports and substrates, which well achieves excellent catalytic activity and selectivity in Pickering emulsion compared to that in the pure toluene system.

Ternary synergistic catalyst system of Pt–Cu–Mo2C with high activity and durability for alcohol oxidation

Efficient catalyst system of high activity and durability is urgently required to convert alcohols directly on the anode in the direct alcohol fuel cells technique. Herein, an efficient ternary catalyst system of Pt–Cu–Mo2C catalyst is compositionally optimized and mechanically probed for the oxidation of methanol and ethanol fuels. Outstanding catalytic capabilities including high catalytic activity, stability, fast kinetics and high anti-poisoning ability are found due to the strong electronic effect, ligand effect and multi-oxophilic component synergism. Cu and Mo2C play different roles in the oxophilic functionalities formation as well as the anti-poisoning effect, and the combined advantages of Mo2C and Cu in the catalyst system make this ternary system more efficient for alcohols fuel oxidation compared with the traditional binary catalysts. Specifically, the peak current density of Pt–Cu–Mo2C is 80.31 mA cm−2 for methanol oxidation with a nearly 3.5-fold enhancement compared to the state-of-the-art commercial Pt/C catalyst (23.61 mA cm−2); the highest CO-tolerance ability is demonstrated by the lowest CO-oxidation peak at 0.451 V(117 mV less than Pt/C), and as high as 74.55 and 86.81% of the initial current density are maintained, respectively, after a 1000-cycle accelerated stability test towards methanol and ethanol oxidation for fuel cell reaction.

Platinum quantum dots enhance electrocatalytic activity of bamboo-like nitrogen doped carbon nanotubes embedding Co-MnO nanoparticles for methanol/ethanol oxidation

Interaction of multi-active components can effectively maximize the overall catalytic ability of alcohol fuel cells. Herein, the self-assembled nitrogen doped carbon nanotubes (NCNTs) containing Co-MnO composite (Co-MnO/NCNTs) are successfully synthesized using dihydrodiamine as carbon and nitrogen source through one-step synthesis. In order to further improve the catalytic activity of Co-MnO/NCNTs for alcohol oxidation, small amounts of platinum quantum dots are uniformly loaded on Co-MnO/NCNTs formation of quaternary hybrid (named Pt/Co-MnO/NCNTs) during microwave reduction stage. Notably, the prepared Pt/Co-MnO/NCNTs hybrids possess the excellent methanol and ethanol oxidation mass current density of 1775.4 and 1112.8 mA mg−1 in alkaline condition, which are 3.6 and 2.25 times higher than that of Pt/C catalysts, respectively. The current density of ethanol catalytic oxidation is lower than that of methanol, which may be due to the partial oxidation of acetyl (the intermediate product of ethanol) on the Pt (1 1 1) crystal surface. More importantly, CO oxidation experiments reveal that strong electronic synergistic effect between MnO and Pt quantum dot can greatly improve the CO anti-poisoning ability. Another significant advantage of Pt/Co-MnO/NCNTs is that low platinum loading leads to low cost effective, which demonstrates that the modification non-noble metal catalysts with a few noble metals quantum dots is a promising choice to mass produce high performance catalyst with remarkably boosting electrocatalytic activity for alcohol oxidation.

Study of Methanol Electro-Oxidation on Thin Nickel Films by Sampled Current Voltammetry

Nickel-based electrocatalysts have shown good catalytic activity for the electrochemical oxidation of alcohols in alkaline media, which has generated significant interest in using nickel films and nickel oxides in alcohol fuel cells. In this work, Ni films were deposited by the galvanostatic method on gold electrodes. The electrocatalytic activity for the electro-oxidation of methanol from these deposits was evaluated by cyclic voltammetry (CV) and sampled current voltammetry (SCV). Cyclic voltammetry measurements showed that depending on the Au electrode roughness, the position NiOOH formation peak of the electrodeposited Ni deposits could differ. The deposits were divided depending on whether the NiOOH formation peak was below or above 0.39 V vs. Ag|AgCl reference electrode. Sampled current voltammograms showed that the former presented greater specificity for the oxidation of methanol, and the latter, showed electrocatalytic activity for both the oxidation of methanol and for the oxygen evolution reaction.

Ultrasmall amphiphilic zeolitic nanoreactors for the aerobic oxidation of alcohols in water.

Organic reactors in a green solvent (water) is the goal of sustainable development. Green nanoreactors with excellent amphiphilicity and catalytic activity are strongly desired. Herein, a novel amphiphilic nanoreactor Pd@amZSM-5 with ultrasmall size has been successfully synthesized via a simple one-step oil bath method, subjected to the modification-etching-modification strategy and in situ reduction of Pd2+. Ultrasmall Pd@amZSM-5 nanoreactors (60 nm) with hierarchical structures showed outstanding amphiphilicity for forming Pickering emulsions with fine uniform droplets (50 μm). Fine droplets formed short diffusion distances, which can significantly improve the catalytic activity in biphasic reactions. Moroever, the ultrasmall Pd@amZSM-5 nanoreactors demonstrated excellent catalytic activity for the selective oxidation of alcohols in water using air as the oxidant. Alkali was not present in the reaction system. The hydrophilic aminopropyl groups on the surface of the Pd@amZSM-5 nanoreactors not only changed the affinity of the zeolite surface and provided targeting points for Pd nanoparticles but also provided an alkaline environment for the selective oxidation of alcohols. The ultrasmall Pd@amZSM-5 nanoreactors presented excellent universality for aromatic alcohols (with >90% conversion and >90% selectivity) and allylic alcohols (with 100% conversion and 100% selectivity).

Correlation between the Properties of Sol-Gel Synthesized Graphene/Titania Hybrid Nanostructures and Their Catalytic Activity in Selective Aerobic Oxidation of Alcohols

A low-cost sol-gel process was used to synthesize hybrids of graphene and titania without the use of surfactants or additives. A less frequently used titania precursor, titanium oxychloride, was used to yield TiO2 nanoparticles and dispersed graphene was used in the reaction mixture to provide a surface for the nano-sized titania particles’ dispersion. The obtained samples after filtration and drying were calcined at 400 °C to get an anatase phase titania powder. Various techniques like XRD, SEM, and TEM have investigated the structure of the prepared samples. The hybrid’s structural morphology shows the incorporation of the transition metal oxide (TiO2) particles into the dispersed layers of graphene. The size of the TiO2 particles and the nature of the interaction among the prepared hybrid materials were explored. Nitrogen gas physisorption studies revealed that graphene adds variety to the pore size of hybrid materials which is a special property of hybrid structures. Additionally, the catalytic performance of hybrid nanostructured samples was investigated in the catalytic reaction for benzyl alcohol oxidation. It was found that the addition of graphene content in the hybrid increases the rate of reaction. The increase in the reaction rate is attributed to the ease of electron transfer through graphene layers. This study provides a systematic view of graphene/titania hybrids’ preparation, their resulting properties, and their catalytic performance in the benzyl alcohol oxidation reaction. Results and conclusions show interesting possibility of using two-dimensional graphene with nanoparticles for further studies in benzyl alcohol oxidation.

Nitrate Radical Facilitates Indirect Benzyl Alcohol Oxidation on Bismuth(III) Vanadate Photoelectrodes

AbstractBismuth(III) vanadate (BiVO4) films show activity for direct benzyl alcohol (PhCH2OH) oxidation to benzaldehyde (PhCHO) in acetonitrile solvent. Introducing tetrabutylammonium nitrate (Bu4NNO3) drastically reduces the overpotential required to generate the PhCHO product while maintaining a high faradaic efficiency (FE) >90 %. BiVO4 corrosion accompanies PhCH2OH oxidation. However, the presence of nitrate ions (NO3−) results in significantly less bismuth‐ and vanadium‐ion leaching (determined by ICP‐MS analysis), as well as reduced surface roughening (determined by SEM imaging). In this reaction, it is proposed that rate‐determining NO3− oxidation generates a highly reactive nitrate radical (NO3⋅) that reacts with PhCH2OH by hydrogen‐atom abstraction (HAT). NO3− is stoichiometrically consumed by the irreversible formation of electrochemically inert HNO3, characterized by an ECi mechanism, rather than a catalytic EC′ mechanism. In the presence of PhCH2OH, NO3− oxidation on BiVO4 becomes more facile; every order of magnitude increase in PhCH2OH concentration shifts the NO3−/ NO3⋅ equilibrium potential negatively by 200 mV. The shift results from the introduction of a consumption pathway for the nitrate radical intermediate via a coupled chemical step with benzyl alcohol. This report is the first example of photoelectrochemical NO3⋅ generation to initiate indirect PhCH2OH oxidation.

2D/2D MXene/g-C3N4 for photocatalytic selective oxidation of 5-hydroxymethylfurfural into 2,5-formylfuran

The selective oxidation of 5-hydroxyfurfural (HMF) into the corresponding aldehyde is one of the key reactions in the production of chemical products. Here, we prepared the MXene/g-C3N4 composite (MX/CN) for photocatalytic selective oxidation of HMF into 2,5-diformylfuran (DFF). At the mild reaction conditions, both DFF selectivity and yield can reach up to ≥ 90% over 6% MX/CN. In addition, the MX/CN also shows high activity for selective oxidation of other non-aromatic and aromatic alcohols. Moreover, the reaction conditions are surveyed and the mechanism has been studied. This study provides a way for HMF conversion under mild conditions.