Activity For Oxidation Of Alcohols Research Articles

Radical pathways and O2 participation in benzyl alcohol oxidation, and catechol and o-aminophenol oxidase activity studies with novel zinc complexes: an experimental and theoretical investigation

Diphenoxo bridged dinuclear zinc complexes were found to be capable of oxidation of benzyl alcohol, catechol and o-aminophenol.

Porous chitosan–MnO2 nanohybrid: a green and biodegradable heterogeneous catalyst for aerobic oxidation of alkylarenes and alcohols

A porous chitosan–manganese dioxide (PC–MnO2) nanohybrid was synthesized using an in situ reduction method, in which potassium permanganate solution and nanoporous chitosan acted as precursor and reducing agent. The chemical and structural properties of PC–MnO2 were characterized using scanning and transmission electron microscopies, X‐ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy. Highly dispersed MnO2 nanoparticles in a matrix of porous chitosan showed high catalytic activity for selective aerobic oxidation of alkylarenes and alcohols without using any bases or expensive oxidants. Short reaction time, ease of product separation by filtration and recyclability of the catalyst make it environmentally and economically favoured for the synthesis of versatile aldehydes and ketones. Copyright © 2015 John Wiley & Sons, Ltd.

Silicate intercalated cobalt chromium–hydrotalcite (CoCr–HTSi): An environment-friendly recyclable catalyst for organic transformations

Silicate intercalated cobalt chromium hydrotalcite (CoCr–HTSi) was prepared for the first time by a simple sol–gel method. The resultant CoCr–HTSi yielded remarkable activity for allylic oxidation of cyclohexene and aromatic alcohols in the presence of environmentally-friendly conditions, viz., H2O2 as oxidant and methanol as oxidant. More importantly, the active species remain intact on the surface and no leaching occurred under the reaction conditions. The catalysts are recyclable even after four cycles, and have shown to be as truly heterogeneous in nature.

Selective Aerobic Oxidation of Alcohols into Carbonyl Compounds Promoted by Recyclable Cuo-Ceo2 Nanocomposite in Aqueous Media

An efficient procedure is reported for the selective aerobic oxidation of alcohols to the corresponding carbonyl compounds promoted by CuO-CeO2 nanocomposite in aqueous media. The latter nanocomposite showed high catalytic activity for the aerobic oxidation of various primary and secondary alcohols using oxygen as oxidant. This procedure provides several advantages such as catalyst recyclability, simple work-up, clean procedure, relatively short reaction time and high yields of the products.

Selective aerobic oxidation of alcohols by a mesoporous graphitic carbon nitride/N-hydroxyphthalimide system under visible-light illumination at room temperature

By combination of photocatalysis and organocatalysis, a metal-free system composed of mesoporous graphitic carbon nitride (mpg-C3N4) and N-hydroxyphthalimide (NHPI) offers an efficient and environmentally friendly method for the oxidation of alcohols at room temperature. As a wide-band gap semiconductor, mpg-C3N4 absorbs visible light and uses the energy to activate NHPI, resulting in high catalytic activity in the subsequent oxidation of alcohols. Interestingly, the main oxidation product of benzyl alcohol can be tuned from benzoic acid to benzaldehyde by increasing the ratio of mpg-C3N4 in the catalyst system. To further understand the reaction route, electron spin resonance and Fourier transform infrared measurements were carried out, confirming that active oxygen and phthalimide N-oxyl radicals formed in the mpg-C3N4/NHPI system. Based on these results, a catalytic mechanism for the mpg-C3N4/NHPI system was proposed. Moreover, this metal-free system also works well for the oxidation of various aromatic alcohols with good selectivity for aldehydes or ketones.

Bimetallic synergistic Au/CuO-hydroxyapatite catalyst for aerobic oxidation of alcohols

A catalyst consisting of Au supported on copper oxide-modified hydroxyapatite (Au/CuO-HAP) was prepared using a homogeneous deposition-precipitation method. The catalyst was characterized using atomic absorption spectrometry, N2 adsorption-desorption, powder X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalytic performance in liquid-phase aerobic oxidation of alcohols was investigated. The catalytic activity and benzaldehyde selectivity in benzyl alcohol oxidation with the bimetallic Au/CuO-HAP catalyst were significantly better than those with monometallic Au/HAP and CuO-HAP catalysts. The conversion of benzyl alcohol and selectivity for benzaldehyde at 120 °C for 1.5 h under aerobic oxidation conditions were 99.7% and 98.4%, respectively. Various aromatic alcohols were selectively converted to their corresponding aldehydes or ketones over Au/CuO-HAP. The Au/CuO-HAP catalyst could be reused at least four times without loss of activity.

Theoretical Studies on the Synergetic Effects of Au–Pd Bimetallic Catalysts in the Selective Oxidation of Methanol

The selective oxidation of methanol to formaldehyde with molecular O-2 on Au-Pd alloy surfaces has been studied by using density functional theory (DFT). We show that the existence of Pd remarkably improves the adsorption and activation of O-2 on Au-Pd surfaces. In particular, the second-neighbor Pd monomer pair (Pd-SNMP) surrounded by gold atoms can provide unique active sites for the coadsorption of O-2 center dot center dot center dot CH3OH, thus facilitating the activation of O2 via a hydroperoxyl radical (*OOH). With the involvement of *OOH and its decomposed fragments (*O and *OH), the oxidative dehydrogenation of methanol to formaldehyde is facilely achieved on bimetallic Au-Pd surfaces, the barriers of which are calculated to be 0.02-0.45 eV on Au2Pd/(111) and AuPd/(100) surfaces. Importantly, we find that the unusual activation of O-2 via an OOH pathway instead of direct dissociation on Au-Pd catalysts is mainly responsible for the enhanced activity and selectivity in the selective oxidation of alcohols. This hydroperoxyl-based mechanism reveals the intrinsic synergy of Au-Pd bimetallic catalysts in the selective oxidation of alcohols and may provide insights for designing better bimetallic catalysts

Synthesis of UiO-66-NH2 derived heterogeneous copper (II) catalyst and study of its application in the selective aerobic oxidation of alcohols

The three-dimensional Zr-based metal-organic framework UiO-66-NH2 was functionalized with salicylaldehyde using a post-synthetic modification (PSM) strategy, and then three kinds of copper (II) salts were successfully immobilized onto the surface of the amino-functionalized Zr-MOF. The SEM and PXRD results showed that the morphology and structure of Zr-MOF were retained after multiple transformations. The obtained UiO-66-Sal-CuCl2 catalyst exhibited excellent activity for the selective aerobic oxidation of primary aromatic alcohols using molecular oxygen as the oxygen source. Furthermore, the UiO-66-Sal-CuCl2 catalyst showed a good cycle performance.

Facile synthesis of α-Fe2O3 nanoparticles and their catalytic activity in oxidation of benzyl alcohols with periodic acid

α-Fe2O3 nanoparticles (NPs) were synthesized by homogeneous chemical precipitation followed by calcination. Size-tuning of NPs was achieved by using polyethylene glycol with a molecular weight of 400 and 4000 as surfactant. Synthesized α-Fe2O3 NPs were characterized by powder XRD, transmission electron microscopy, N2 adsorption–desorption isotherm and vibrating sample magnetometry. These α-Fe2O3 NPs were used as magnetically recoverable catalyst in oxidation of benzyl alcohols to aldehydes with periodic acid. The catalyst showed higher efficiency with decrease in their sizes.

Selective oxidation of alcohols with H2O2 catalyzed by long chain multi-SO3H functionalized heteropolyanion-based ionic liquids under solvent-free conditions

Two novel long chain multi-SO3H functionalized heteropolyanion-based ionic liquids were prepared and characterized. They as homogeneous catalysts showed high catalytic activity in selective oxidation of alcohols with 35% aqueous hydrogen peroxide under solvent-free conditions without adding any phase transfer catalyst. Two ionic liquids can be recovered readily and reused five times without any significant loss in their catalytic activities.

Pdni-Based Catalysts for Anion-Exchange Membrane Direct Methanol Fuel Cell (AEM-DMFC)

New processes like oxidative bi-reforming of methane (e.g. from natural gas) developed by Olah et al. allows to produce methanol in an overall economic and energetically efficient process.[1,2] Compared to methane, methanol is a useful intermediate material in many chemical manufacturing processes as well as a safe-to-handle liquid fuel for transportation and mobile applications. Direct Methanol Fuel Cells (DMFCs) have attracted enormous attention as potential power sources for electronic devices and back-up power solution due to higher energy density than gaseous fuels such as hydrogen. However, problems like slow electro-kinetics of alcohol oxidation, costs of membranes and catalysts and alcohol crossover are hindering their commercialization.[3] Recent studies have shown that the electrocatalytic activity for alcohol oxidation in alkaline media is much higher than that in acidic media. The oxidation of methanol (MeOH) in alkaline media has shown higher current densities and smaller overpotentials compared to those in acidic media.[4] Besides this the catalyst materials used for alcohol oxidation reaction (AOR) and oxygen reduction in Anion-Exchange Membrane Direct Methanol Fuel Cells (AEM-DMFCs) are cheaper and more efficient than Pt.[5] Pd has proved to be a good electrocatalyst for AOR in alkaline medium, showing higher activity and better steady-state currents than Pt.[6] To improve the activity and stability towards alcohol oxidation, Pd-based catalysts including Pd-oxide composite, Pd-based binary and Pd-based ternary catalysts have been investigated by several research groups. In a former study we reported the high activity of carbon supported binary PdNi/C anode catalysts for AEM DMFCs.[7] Inspired by these findings we investigated on ternary PdNiSn/C and PdNiRu/C anode catalysts for AEM-DMFCs. Table 1 summarizes the electrocatalysts synthesized in this study. Table 1: Summary of synthesized electrocatalysts. Loading on carbon and composition of the catalysts were measured by thermogravimetric analysis coupled with inductively coupled plasma optical emission spectroscopy. Catalyst Ratio Pd:Metal Catalyst Composition Pd:Ni:Metal Loading [wt%] Pd/C 21.0 Pd3Ni1/C 3:1 3:0.95 19.6 Pd5Ni1/C 5:1 5:0.97 20.0 Pd3Ni0.5Ru0.5/C 3:1 3:0.43:0.49 19.7 Pd5Ni0.5Ru0.5/C 5:1 5:0.46:0.49 20.6 Pd3Ni0.5Sn0.5/C 3:1 3:0.44:0.51 19.4 Pd5Ni0.5Sn0.5/C 5:1 5:0.47:0.55 20.7 Electrochemical evaluation of the methanol electrooxidation in alkaline media was done via cyclic voltammetry (CV) and chronoamperometry (CA) in a standard 3-electrode set-up with mercury/mercury oxide reference electrode (MMO). In Figure 1A&B, it is observed that the tested materials present a lower onset potential and higher current densities for the AOR compared to Pt/C, Pd/C and PdNi/C. This is an evidence that the electrocatalysts presented here have an improved catalytic activity than the one reported before. Membrane electrode assemblies (MEAs) with the electrocatalysts were fabricated using a Tokuyama A201 as membrane and SGL 10AA and Freudenberg H2315 as anodic and cathodic diffusion layer, respectively. Figure 1C shows the Tafel plots derived from single cell performance tests. A significant increase of power densities for ternary catalysts compared to Pd/C or PdNi/C catalysts at fuel cell working potentials was observed. For a cell potential of 0.5V the performance magnifies from 4.8mW cm-2 for Pd/C to 23.2mW cm-2 for Pd3Ni0.5Ru0.5/C. These results are in accordance with the ones illustrated in Figure 1A&B. Further work will include tests on an AEM-DMFC short stack based on Pd3Ni0.5Ru0.5/C anode catalyst. Fig. 1 - Cyclic voltammetry (A) and chronoamperometry (B) curves of Pt/C, Pd/C, Pd3Ni/C and Pd3Ni0.5M0.5/C (M=Ru, Sn) catalysts for methanol electrooxidation in 0.5M KOH + 0.5M MeOH at room temperature; Tafel plots (C) from single cell performance tests of MEAs with Pd/C, Pd3Ni/C and Pd3Ni0.5M0.5/C (M=Ru, Sn) anode catalysts and Acta S.p.A. HYPERMEC™ 4020 cathode catalyst measured with 1M MeOH + 2M KOH and synthetic air as fuels at 60°C.

Monodispersed poly(4-vinylpyridine) spheres supported Fe(III) material: An efficient and reusable catalyst for benzylic oxidation

A novel ferric chloride immobilized poly(4-vinylpyridine) (P4VP) catalyst was developed via a coordination chemistry-based approach. The pyridine moiety of poly(4-vinylpyridine) spheres functioned as the nitrogen donor to bind iron ions, as well as to decrease the amount of pyridine used in the catalytic reaction system. The monodispersed catalyst was well dispersed in the organic solvent during the catalytic procedure, taking advantage of its nanomorphology and uniform size. The catalytic activity of various monodispersed catalysts based different mass fractions of the divinylbenzene (DVB) was investigated, meanwhile the capacities of supported Fe(III) in the various catalysts were also discussed. The P4VPDVB10%-Fe(III) catalyst exhibited high catalytic activity in the benzylic oxidation of benzylic methylenes and secondary benzylic alcohols. It was easily separated from the reaction system and reused several times without obvious degradation of catalytic activity. Moreover, leaching tests suggested that the as-synthesized P4VPDVB10%-Fe(III) catalyst was a true heterogeneous catalyst without significant metal leaching.

Novel Coordination Polymers with (Pyrazolato)-Based Tectons: Catalytic Activity in the Peroxidative Oxidation of Alcohols and Cyclohexane

Coupling five rigid or flexible bis(pyrazolato)-based tectons with late transition metal ions allowed us to isolate 18 coordination polymers (CPs). As assessed by thermal analysis, all of them possess a remarkable thermal stability, their decomposition temperatures lying in the range of 340–500 °C. As demonstrated by N2 adsorption measurements at 77 K, their Langmuir specific surface areas span the rather vast range of 135–1758 m2/g, in agreement with the porous or dense polymeric architectures retrieved by powder X-ray diffraction structure solution methods. Two representative families of CPs, built up with either rigid or flexible spacers, were tested as catalysts in (i) the microwave-assisted solvent-free peroxidative oxidation of alcohols by t-BuOOH, and (ii) the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone by H2O2 in acetonitrile. Those CPs bearing the rigid spacer, concurrently possessing higher specific surface areas, are more active than the corresponding ones with the flexible spacer. Moreover, the two copper(I)-containing CPs investigated exhibit the highest efficiency in both reactions, leading selectively to a maximum product yield of 92% (and TON up to 1.5 × 103) in the oxidation of 1-phenylethanol and of 11% in the oxidation of cyclohexane, the latter value being higher than that granted by the current industrial process.

Synthesis and Heterogenization of Siloxane Functionalized Cobalt Complex: Potential Catalyst for Oxidation of Alcohols

Cobalticinium complex containing siloxane moiety on ligand center was first time synthesized, characterized and heterogenized on the surface of SBA-15 molecular sieves. FT-IR and 29Si-MAS-NMR spectrum evidence the successful grafting of the cobalt complex on the surface of SBA-15. N2 sorption isotherm of cobalticinium complex grafted sample showed the decrease in surface area, pore volume, further confirms the presence of complex inside the channel of mesoporous SBA-15. The heterogenized complex exhibited promising activity for oxidation of alcohols with good selectivity of ketone. Further the catalytic activity remains intact after two recycles. Cobalticinium complex possessing siloxane functionality was prepared first time and heterogenized on SBA-15 surface. The resultant materials showed as promising recyclable heterogeneous catalyst for oxidation of alcohols.

High-efficiency PdCu alloy nanocube catalyst supported on N-doped multiwalled carbon nanotubes for alcohol electrooxidation

N-doped of the support is generally important to immobilize metal nanoparticles on the support, produce some active Me–N sites, and generate good electrocatalytic activity and stability. A facile and low-cost preparation of N-doped multiwalled carbon nanotube (N-MWCNTs)-supported hollow PdCu alloyed nanocube catalyst (H–PdCu/N-MWCNTs) was introduced in this paper. To increase the stability and utilization ratio of the noble metal, a two-step strategy was employed, which included the synthesis of N-MWCNTs using polypyrrole (ppy) as the source of nitrogen and the preparation of the hollow PdCu alloyed nanocubes. According to transmission electron microscopy (TEM) measurements, the as-prepared hollow PdCu alloyed nanocube catalyst has superior dispersibility, and the average diameter is about 50 nm. X-ray photoelectron spectroscopy (XPS) measurements reveal that N atoms have been doped in multiwalled carbon nanotubes (MWCNTs) and there is abundance of pyridinic N and graphitic N species on N-MWCNT surface. The electrochemical measurements indicate that the hollow PdCu alloyed nanocube catalyst has a better electrocatalytic activity and stability for the alcohol oxidation. It is concluded that the H–PdCu/N-MWCNTs would be a potential candidate as an anode electrocatalyst in direct alcohol fuel cell.

Hierarchical electroless Pt deposition at Au decorated reduced graphene oxide via a galvanic exchanged process: an electrocatalytic nanocomposite with enhanced mass activity for methanol and ethanol oxidation

The electronic and synergistic effects of Au core and thin layer of Pt shell are the promising properties for the enhanced catalytic activity in alcohol oxidation compared to commercial catalysts.

Novel approach to synthesizing polymer-functionalized Fe3O4/SiO2–NH2via an ultrasound-assisted method for catalytic selective oxidation of alcohols to aldehydes and ketones in a DMSO/water mixture

A Fe3O4/SiO2/PATL/MnO2 core/shell nanocomposite was synthesized via an ultrasound-assisted method and its catalytic activity for the aerobic oxidation of alcohols to aldehydes and ketones was evaluated .

Preparation and Evaluation of Bimetallic Au Nano-Catalyst with Aerobic Oxidation of 1-Phenylethanol

ABSTRACTContributions of electronic (or ligand) and geometric (or ensemble) effects on the AuM bimetallic nano-catalyst were elucidated by using a simple aerobic oxidation of 1-phenylethanol to acetophenone on the basis of difference in the ionization energy values (Ei) between Au and M elements. The poly(N-vinylpyrrolidone) (PVP)-protected Au60M40 bimetallic NPs (M = Ag, Cu, Pd, Pt and Ir) were prepared with a polyol reduction method, and stabilized onto the solid base hydrotalcite support affording the Au60M40-PVP/HT catalysts. The yields for acetophenone were observed as the following order; Au60Pd40-PVP/HT (>99%) >> Au60Ag40-PVP/HT (17.4%) > Au60Cu40-PVP/HT (13.8%) > Au60Pt40-PVP/HT (7.1%) > Au60Ir40-PVP/HT (5.5%), at 343 K for 6 h. Differences in the Ei between Au and M (EiAu-EiM) indicted that the yields over the Ag, Cu, Pt, and Ir incorporated Au catalysts were well-understood on the ligand effects theory, though geometric factors such as differences in nanostructure around Au atom in Au60M40 NPs on HT should be further considered as other contributed factors. The significant activity on Au60Pd40-PVP/HT was studied in terms of the electron density of Pd atoms. It was observed that the Pd 4d density was varied by the amount of Au loading. According to these observations combined with our previous studies, we suggest that the advantages in AuPd bimetallic catalyst are not only in the ligand effect serving negatively-charged Au but also the ensemble effect of neighbor Pd, and they synergistically contribute to the novel activity for aerobic alcohol oxidation over AuPd catalyst.

Factors influencing the catalytic oxidation of benzyl alcohol using supported phosphine-capped gold nanoparticles

The nature of Au cluster precursor and activation treatments affect catalyst activity in aerobic benzyl alcohol oxidation.

Reactivities of platinum subnanocluster catalysts for the oxidation reaction of alcohols

The size-dependent catalytic activity for alcohol oxidation was investigated using the platinum subnanoclusters synthesized by the dendrimer template method.