Activity For Oxidation Of Alcohols Research Articles

Effect of alkali and alkaline earth metal ions on benzyl alcohol oxidation activity of titanate nanotube-supported Au catalysts

Au supported on barium titanate nanotubes showed higher catalytic activity for selective oxidation of benzyl alcohol with molecular oxygen.

ChemInform Abstract: A Highly Efficient and Recyclable Silica‐Supported Palladium Catalyst for Alcohol Oxidation Reaction.

Abstract A silica supported palladium catalyst (SiO 2 @APTES-Pd) showed excellent activity and reusability for selective oxidation of alcohols to corresponding carbonyl compounds with H 2 O 2 as oxidant under base free environment. A wide range of alcohols including aliphatic alcohols are tolerated as substrates with a low loading of palladium (0.1 mol %).

Hierarchical PS/PANI nanostructure supported Cu(ii) complexes: facile synthesis and study of catalytic applications in aerobic oxidation

Hierarchical heterogeneous copper catalysts were prepared by immobilization of a homogeneous copper(II) complex on the surface of polystyrene/polyaniline (PS/PANI) microspheres with oriented PANI nanofibers. EDX element maps and XPS spectra indicated that Cu2+ ions strongly coordinated with PANI imine. PS/PANI@Cu(OSO2CF3)2 exhibited excellent catalytic activity for selective aerobic oxidation of alcohols and highly efficient aerobic epoxidation of alkenes under mild conditions. The supported copper(II) catalyst maintained high levels of conversion and selectivity in these reactions after six cycles and showed good stability.

Cobalt(II) phthalocyanine covalently anchored to cellulose as a recoverable and efficient catalyst for the aerobic oxidation of alkyl arenes and alcohols

Cobalt(II) phthalocyanine covalently immobilized on cellulose as a heterogeneous catalyst was synthesized and characterized. The catalyst showed good catalytic activity for the aerobic oxidation of alkyl arenes and alcohols under relatively mild reaction conditions. The catalyst can readily be recovered from the reaction mixture and reused for several runs without significant decrease in catalytic activity.

Nanostructured Platinum and Carbon Supported Pt-Ni Catalyst for Polymer Electrolyte Fuel Cell

The Pt-Ni bimetallic nanoparticles supported on nano carbon (PtxNiy/C) have been synthesized by the polyol reduction under ultrasonic irradiation. The morphology, structure and specific area of synthesized materials were characterized by X-Ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET). The electrocatalytic activity for alcohol oxidation of the synthesized PtxNiy/C materials and the commercial 10wt.% Pt loaded on activated carbon catalyst (Aldrich Sigma, Pt/C_com) was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). The catalytic activity for oxygen reduction reaction (ORR) of PtxNiy/C was investigated by CV and linear sweep voltammetry (LSV). The major size of synthesized metallic particles was around 2 nm. The Pt2Ni1/C exhibited excellent catalytic properties for alcohol oxidation compared to other catalysts on the same support. The CNTs were found to be more effective than carbon Vulcan for use as a support for alcohol oxidation catalysts. The linear sweep voltammograms showed that PtxNiy/C, which has the least coverage of oxygenated species, was the best catalyst for ORR with its onset potential of 0.624 V. From the slope of Koutecky-Levich plot for ORR using PtxNiy/VC materials as catalysts it was found that the overall electron transfer number ranged from 3 to 4, leading to the suggestion of H2O2 formation as an intermediate of the ORR.

Effect of amines as activators on the alcohol-oxidizing activity of pyrroloquinoline quinone-dependent quinoprotein alcohol dehydrogenase.

Pyrroloquinoline quinone-dependent quinoprotein alcohol dehydrogenases (PQQ-ADH) require ammonia or primary amines as activators in in vitro assays with artificial electron acceptors. We found that PQQ-ADH from Pseudomonas putida KT2440 (PpADH) was activated by various primary amines, di-methylamine, and tri-methylamine. The alcohol oxidation activity of PpADH was strongly enhanced and the affinity for substrates was also improved by pentylamine as an activator.

Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate-Ag2S-CdS semiconductors.

Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O40(3-), SiW12O40(4-) and PMo12O40(3-), were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.

A highly efficient and recyclable silica-supported palladium catalyst for alcohol oxidation reaction

A silica supported palladium catalyst (SiO2@APTES-Pd) showed excellent activity and reusability for selective oxidation of alcohols to corresponding carbonyl compounds with H2O2 as oxidant under base free environment. A wide range of alcohols including aliphatic alcohols are tolerated as substrates with a low loading of palladium (0.1mol%).

Alcohol Oxidation on Porous PtCu Catalyst

IntroductionDirect alcohol fuel cells (DAFCs) are promising power conversion systems developed to overcome the restrictions of hydrogen fuel in proton exchange membrane fuel cells. Liquid fuels, such as methanol, ethanol and formic acid, are easily handled, stored and transported, compared to gaseous fuels, such as H2 and natural gas1. However, DAFCs typically have lower performances than fuel cells that utilize H2. Here, we report a PtCu/C catalyst that exhibits higher activity and lower onset potential compared to Pt/C. We also utilize the ratio of the forward anodic peak current (If) over the reverse anodic peak current (Ib), If/Ib, to evaluate the CO poisoning resistance of catalysts. Our data shows that PtCu/C catalyst has higher activity and higher If/Ib value for methanol and ethanol oxidation reaction compared to commercial Pt/C catalyst in both acidic and basic medium.ExperimentalA nanoporous Cu support was formed by etching Al from an in-house prepared CuAl alloy, with composition ranging between 20 to 50 wt% Cu. Upon etching, the nanoporous support provides a high surface area of 10-15 m2/g. Pt was deposited onto the support via a galvanic displacement reaction at a constant rotation rate. Alcohol oxidation activity was evaluated using a rotating ring disc electrode (PINE Instruments) as working electrode, with a reversible hydrogen electrode as reference and a Pt mesh as a counter electrode. All experiments are performed in 0.1M HClO4 + 0.5M MeOH (or 0.5M EtOH) and 0.1M KOH + 0.5M MeOH (or 0.5M EtOH) at room temperature.Results and DiscussionFigure 1 compares the CV curves of PtCu catalyst with commercial Pt/C catalyst in a 0.5M MeOH + 0.1M HClO4. Both CVs were obtained at 1600 rpm and sweep rate of 10mV/s. The If/Ib values of the forward peaks were calculated and used to suggest poisoning resistance of the catalysts with a larger If/Ib ratio implying greater resistance to electrode poisoning. Our data shows that the If/Ib value of PtCu (~1.5) is much higher than Pt/C (~0.5). Our data indicates that smaller overall Pt surface area gave higher If/Ib ratio (>1), as the deposited Pt surface area reaches a value closer to the Pt/C, the If/Ib ratio starts to ressemble those of Pt/C (at ca. 0.7). Finally, Figure 3 exhibits the bar graph of If/Ib for methanol and ethanol oxidation vs. Pt deposition time in both acidic and alkaline conditions. Alkaline conditions were performed in 0.1M KOH + 0.5M alcohol and acidic conditions were in 0.1M HClO4 + 0.5M alcohol. CVs were collected at 1600 rpm and 100 mV/s. Figure 2 shows that the PtCu catalysts consistently gave higher If/Ib ratios compared to Pt/C. Figure 3 also illustrates that the 2.5min Pt deposition shows the greatest resistance to poisoning during methanol oxidation and the 0.5min Pt deposition catalysts is the most resistant to carbonaceous poisoning during ethanol oxidation in 0.1M KOH. In acidic conditions, both methanol and ethanol oxidation gave the least poisoning characteristic for 0.25min Pt deposition. In this paper we will discuss PtCu as a promising catalyst for alcohol oxidation reactions in DAFCs.

Electrochemical Polymerization of Pyrrole Containing TEMPO Side Chain on Pt Electrode and Its Electrochemical Activity

Poly(4-(3-(pyrrol-1-yl)propionyloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy) (PPy-TEMPO) electrode is prepared by electrochemical polymerization on Pt electrode in NaClO4-CH3CN solution. The electrocatalytic activity of PPy-TEMPO for benzyl alcohol in NaClO4-CH3CN solution is investigated by cyclic voltammetry and in situ FTIR. Results show that PPy-TEMPO electrode exhibits high electrocatalytic activity for benzyl alcohol oxidation in the presence of 2,6-lutidine as the base, as compared with the bare Pt electrode under the similar conditions. On the basis of in situ FTIR data, it shows that TEMPO is oxidized to its cation at the potential about 0.4V, and benzyl alcohol is oxidized to benzaldehyde instead of benzoic acid. Further studies of preparative electrolysis experiments by constant current electrolysis are carried out to confirm the high conversion to benzaldehyde, and the results are in good agreement with those from in situ FTIR investigations.

Pt catalysts modified with Bi: Enhancement of the catalytic activity for alcohol oxidation in alkaline media

Recent developments on anion-exchange membranes for fuel cell application renewed the interest in the study of alcohol oxidation at high pHs for applications in anion-exchange membrane direct alcohol fuel cells (AEM-DAFC). Although platinum is still the most studied catalyst for oxidation of alcohols in alkaline media, the introduction of one or more metals in order to increase the oxophilicity of the catalyst is a common approach in the development of improved materials for these reactions. In this manuscript, we report the enhancement of the catalytic activity of Pt/C toward ethanol, methanol, and propanol oxidation in alkaline media by simple adsorption of Bi surface. The activity was checked by cyclic voltammetry, and the reaction products and intermediates were analyzed by “in situ” infrared spectroscopy. The presence of Bi was shown to increase the activity of Pt toward the oxidation of the referred alcohols by acting as a third body (impeding surface poisoning) and also by an electronic effect (on water adsorption at the surface).

Binary Pd–Polyoxometalates and Isolation of a Ternary Pd–V–Polyoxomolybdate Active Species for Selective Aerobic Oxidation of Alcohols

Binary Pd-polyoxometalates [Pd(dpa)2]3 [PW12 O40]2 ⋅12 DMSO (2), [Pd(dpa)2]3 [PMo12 O40]2 ⋅12 DMSO⋅2 H2 O (3), and [Pd(dpa)(DMSO)2]2 [HPMo10 V2 O40 ]⋅4 DMSO (4) were synthesized by reaction of [Pd(dpa)(OAc)2]⋅2 H2 O (1; dpa=2,2'-dipyridylamine) with three Keggin-type polyoxometalates and fully characterized by single-crystal and powder XRD analyses, IR spectroscopy, and elemental analyses. The synthesis is facile and straightforward, and the complicated ligand-modification procedure often used in the traditional charge-transfer method can be omitted. In 2-4, Pd complexes and polyoxometalate anions are coupled through electrostatic interaction. Compound 4 is more active than the other three compounds in the selective aerobic oxidation of alcohols at ambient pressure. Interestingly, during catalytic recycling of compound 4, unprecedented ternary Pd-V-polyoxometalate [Pd(dpa)2 {VO(DMSO)5}2][PMo12 O40]2 ⋅4 DMSO (5), which was captured and characterized by single-crystal XRD, proved to be the true active species and showed high catalytic activity for the selective aerobic oxidation of aromatic alcohols (98.1-99.8 % conversion, 91.5-99.1 % selectivity). Moreover, on the basis of control experiments and EPR and UV/Vis spectra, a plausible reaction mechanism for the oxidation of alcohols catalyzed by 5 was proposed.

Triple nanocomposites of CoMn2O4, Co3O4 and reduced graphene oxide for oxidation of aromatic alcohols

A composite of reduced graphene oxide (RGO) with oxides of manganese and cobalt together was prepared by a solvothermal method. During synthesis, both the reduction of graphene oxide as well as the growth of nanorod shaped CoMn2O4 and Co3O4 occurred simultaneously having a crystallite size of ~8 nm calculated from X-ray diffraction (XRD). The as-obtained triple nanocomposite material designated as RGO–MnCoO exhibited excellent activity for the liquid phase aerobic oxidation of aromatic alcohols under base-free conditions selectively giving the corresponding aldehydes (>85%). RGO loading was varied in the range of 1–10%, among which 1% RGO–MnCoO showed maximum catalytic activity enhancement of 24% as compared to the bare mixed oxide (MnCo-MO) for the oxidation of vanillyl alcohol. HR-TEM of RGO–MnCoO revealed that it was a composite material having uniform nanotubes of ~25 nm length and 6 nm diameter with a fringe pattern showing the (103) and (004) planes and lattice spaces of 0.26 nm and 0.22 nm, respectively, for the spinel CoMn2O4. The detailed studies on the morphology, size and composition of the as-prepared RGO–MnCoO nanocomposite by XRD, XPS, N2-adsorption/desorption and O2-TPD techniques were used to understand the role of RGO in the enhancement of catalytic activity for oxidation reaction.

New p-tolylimido rhenium(v) complexes with carboxylate-based ligands: synthesis, structures and their catalytic potential in oxidations with peroxides

Novel p-tolylimido rhenium(v) complexes trans-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(pyz-2-COO)(PPh3)]·MeCN (1), trans-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(pyz-2-COO)(PPh3)] (2), trans-(Br,Br)-[Re(p-NC6H4CH3)Br2(pyz-2-COO)(PPh3)] (3), cis-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(ind-3-COO)(PPh3)]·2MeOH (4), 2[Re(p-NC6H4CH3)Cl2(ind-3-COO)(PPh3)]·MeCN (5), 2[Re(p-NC6H4CH3)Br2(ind-3-COO)(PPh3)]·MeOH (6) and 2[Re(p-NC6H4CH3)Br2(ind-3-COO)(PPh3)]·MeCN (7) were obtained in the reactions of [Re(p-NC6H4CH3)X3(PPh3)2] (X = Cl, Br) with pyrazine-2-carboxylic (pyz-2-COOH or PCA) and indazole-3-carboxylic (ind-3-COOH) acids. The compounds were identified by elemental analysis, IR, (1)H, (13)C and (31)P NMR spectroscopy and X-ray crystallography. To get a deeper understanding of the structural and bonding properties of the imido rhenium(v) complexes, calculations at the DFT level were undertaken for trans-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(pyz-2-COO)(PPh3)] and cis-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(ind-3-COO)(PPh3)]. Complexes 1, 3, 4 and 6 exhibited high catalytic activity in oxidation of alkanes with H2O2 and tert-butyl hydroperoxide (TBHP) and of alcohols with TBHP. The selectivity parameters measured in the reactions with linear and branched alkanes indicated that the processes with H2O2 or TBHP proceed with the participation of hydroxyl or tert-butoxyl radicals, respectively. The composition of isomers from oxygenation of methylcyclohexane corresponds to the existence of some steric hindrance around the reaction centers.

Solvothermal synthesis of mesoporous manganese oxide with enhanced catalytic activity for veratryl alcohol oxidation

Solvothermally prepared Mn3O4 showed excellent performance for veratryl alcohol oxidation to veratraldehyde due to formation of monoclinic and hausmannite phases.

Synthesis and Characterization of Metal Salen Complexes Immobilized MCM-41 and their Catalytic Activity for Benzyl Alcohol Oxidation

Co(Ⅱ)-, Mn(Ⅲ)- and Cu(Ⅱ)- salen type complexes were immobilized over mesoporous MCM-41 through coordinating the metal atom to amino groups covalently attached to the MCM-41 functionalized 3-aminopropyl triethoxysilane (3-APTES). The XRD patterns shown that mesostructure of MCM-41 remains intact after various modifications, while spectral techniques shown the successful anchoring the neat complexes inside MCM-41. The catalytic activity results shown that Co-salophen/MCM-41 exhibited the highest catalytic performance in the water phase selective oxidation of benzyl alcohol.

Synthesis and catalytic alcohol oxidation and ketone transfer hydrogenation activity of donor-functionalized mesoionic triazolylidene ruthenium(ii) complexes

We report on the synthesis of a variety of C,E-bidentate triazolylidene ruthenium complexes that comprise different donor substituents E (E = C: phenyl anion; E = O: carboxylate, alkoxide; E = N: pyridine at heterocyclic carbon or nitrogen). Introduction of these donor functionalities is greatly facilitated by the synthetic versatility of triazoles, and their facile preparation routes. Five different complexes featuring a C,E-coordinated ruthenium center with chloride/cymene spectator ligands and three analogous solvento complexes with MeCN spectator ligands were prepared and evaluated as catalyst precursors for direct base- and oxidant-free alcohol dehydrogenation, and for transfer hydrogenation using basic iPrOH as a source of dihydrogen. In both catalytic reactions, the neutral/mono-cationic complexes with chloride/cymene spectator ligands performed better than the solvento ruthenium complexes. The donor functionality had a further profound impact on catalytic activity. For alcohol dehydrogenation, the C,C-bidentate phenyl-triazolylidene ligand induced highest conversions, while carboxylate or pyridine donor sites gave only moderate activity or none at all. In contrast, transfer hydrogenation is most efficient when a pyridyl donor group is linked to the triazolylidene via the heterocyclic carbon atom, providing turnover frequencies as high as 1400 h(-1) for cyclohexanone transfer hydrogenation. The role of the donor group is discussed in mechanistic terms.

Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols

M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 ± 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ∼0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h(-1)) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.

Immobilized complexes of the salen Schiff’s base with metal as oxidation catalysts

The immobilized metal complexes with the Schiff’s base of salen have shown high catalytic activity in oxidation of alkenes, cycloalkenes, and alcohols as compared with their unsupported analogs. Due to the heterogeneous nature of such catalysts, their separation and recycling is rather simple.

Cr(iii)-containing Fe3O4/mercaptopropanoic acid–poly(2-hydroxyethyl acrylate) nanocomposite: a highly active magnetic catalyst in solvent-free aerobic oxidation of alcohols

In this study, polymer-grafted magnetic nanoparticles containing chromium(iii) ions incorporated onto Fe3O4/mercaptopropanoic acid-poly(2-hydroxyethyl acrylate) (Fe3O4/MPA-PHEA-Cr) was prepared via a simple and in situ method. The obtained magnetic nanocomposite exhibited a high catalytic activity and excellent selectivity in the aerobic oxidation of alcohols under solvent-free conditions. The magnetic catalyst could also be separated by an external magnet and reused seven times without any significant loss of activity/selectivity.