Activity For Oxidation Of Benzyl Alcohol Research Articles

Defective Au nanoparticles manipulated by Au-MgxAl-LDH interplay for alkali-free oxidation of benzyl alcohol

Supported gold catalyst, especially in terms of nanosized particles with defective surface and low-coordinated structure, plays a vital role in the heterogeneous catalysis. However, such defective Au nanoparticles are hardly acquired when supporting on non-reducible metal oxides/hydroxides due to insufficient Au-support interaction. In this work, we found that the defective Au NPs could be fabricated via the strong interplay between Au and crystal lattices of layered double hydroxides-MgxAl-LDH. Experimental and theoretical evidences revealed that the formation of a preferential-oriented LDH(015) plane enabled the surface configuration for defective Au centers with the maximized number of step sites at Mg/Al ratio of 3.0–3.5. The optimized Au/Mg3.5Al-LDH catalyst shows a boosting catalytic activity for benzyl alcohol oxidation (TOF, 1008 h−1) at only 80 °C with the lowest activation energy in the absence of alkali. The work provides a new insight for manipulating the defective-enriched Au particles via the fine-tuning Au-LDH interplay for alkali-free selective oxidations.

Effect of loading of Pt-decorated TiO2 on the enhancement of aerobic photo-oxidation of benzyl alcohol

Using Pt loaded on semiconductor supports have created new opportunities for improving catalytic performance when exposed to light. This study used the photo-deposition method to create platinum loaded on TiO2, which was then examined using TEM, ICP, X-ray diffraction, BET analysis, and CO chemisorption. The effect of loading of Pt on P25 under UV light based on photocatalytic activity was assessed and compared, resulting facilitate the electron transfer from Pt to titanium element, which in turn facilitates the aerobic oxidation of C7H8O. Benzotrifluoride (BTF) was used as a solvent in the benzyl alcohol photooxidation. Different loading of Pt on P25 was investigated and the range between 1 wt.% to 3 wt.% Pt–TiO2 through photo-deposition method gave the highest photocatalytic activity (⁓5.8 gcat−1 h−1) than others because of the size of platinum, the surface area of sample and dispersion. The platinum particle size over 1 nm (less than 1nm not enough energy for electron transfer) to and less than 4 nm (over 4 nm cover semiconductor's active sites) were given the highest activity for benzyl alcohol oxidation. The surface area of the sample is increasing with increasing platinum loading before agglomeration is happening. Higher surface area caused more active sites and active species for adsorption and desorption, resulting in better activity.

Construction of 2D C,N-co-doped ZnO/Co3O4 over Ni(OH)2 mesoporous ultrathin nanosheets on Ni foam as high-performance electrocatalysts for benzyl-alcohol oxidation and accelerating hydrogen evolution

The synthesis of 2D C,N-co-doped ZnO/Co3O4@Ni(OH)2/NF heterostructure mesoporous nanosheets which show high activity for benzyl alcohol oxidation (a benzoic acid yield of 99%, and a faradaic efficiency over 97%) is reported.

Heterometal modified Fe3O4 hollow nanospheres as efficient catalysts for organic transformations

Iron oxides (e.g. Fe3O4) are ideal support materials for catalytic organic transformations owing to their sufficient natural abundance, excellent thermal stability and magnetic recycling property. Herein, we report the synthesis of active heterometal (M = Pd, Cu) modified Fe3O4 (M-Fe3O4) hollow nanospheres via a two-step solvothermal/annealing method. Due to the uniformly dispersed active heterometal species in the spherical shell of Fe3O4 hollow nanospheres, the as-prepared Pd-Fe3O4 catalyst exhibits remarkable catalytic activity toward 4-nitrophenol reduction with a turnover frequency of 145 min−1, and shows excellent stability and magnetic recyclability. The catalytic efficiency surpasses most of the similar Fe3O4 supported metal catalysts reported in literatures. Particularly, Cu-Fe3O4 exhibited 5 times higher activity for benzyl alcohol oxidation compared to that of bare Fe3O4 synthesized by the same procedure. An impressive conversion of 49.66% and an outstanding selectivity of 100% can be achieved. Moreover, the positive effects of Pd or Cu elements on the 4-NP molecule adsorption were further confirmed via both experimental results and theoretical studies. Our work demonstrate that the activity boost of iron oxides by heterometal modification is a promising strategy for performance improvement.

Ultrathin Two-Dimensional Bimetal-Organic Framework Nanosheets as High-Performance Electrocatalysts for Benzyl Alcohol Oxidation.

Ultrathin two-dimensional metal-organic frameworks (2D MOFs) have the potential to improve the oxidation of benzyl alcohol (BA) with a large surface area and open catalytic active sites. To achieve high-efficiency electrocatalysts for the oxidation of benzyl alcohol, a moderate solvothermal method was evolved to synthesize a series of 2D MOFs on nickel foam (Ni-MOF/NF, NiCo-61-MOF/NF, NiCo-21-MOF/NF). As the electrocatalyst used for the oxidation of benzyl alcohol, NiCo-61-MOF/NF presented a lower overpotential and superior chemical durability than other electrocatalysts; it only required a potential of ∼1.52 V (vs RHE) to reach 338.16 mA cm-2, with an oxidation efficiency of more than 86%. Besides, after continuous electrocatalysis for 20 000 s at 1.42 V (vs RHE), the current density of NiCo-61-MOF/NF nanosheets was still 38.67 mA cm-2 with 77.34% retention. This demonstrated that NiCo-61-MOF/NF nanosheet electrocatalysts had great potential for benzyl alcohol oxidation. From both the experimental and theoretical studies, it was discovered that NiCo-61-MOF/NF nanosheets have the highest electrocatalytic activity due to their distinctive ultrathin 2D structure, optimized electron structure, and more accessible active sites. This finding would pave a brand-new thought for the design of electrocatalysts with electrocatalytic activity for benzyl alcohol oxidation (EBO).

Passivating the pH-Responsive Sites to Configure a Widely pH-Stable Emulsifier for High-Efficiency Benzyl Alcohol Oxidation.

Widely pH-stable emulsions configured by solid emulsifiers with high chemical stabilities and anti-corrosion properties under strong acid or alkaline conditions are highly sought after for practical and wide application of Pickering interfacial catalysis. Herein, a unique strategy was reported for synthesis of a widely pH-stable and novel emulsifier by passivating the pH-responsive sites on graphene oxide nanoribbon (GONR) surface using ionic liquid (IL). The suitable wettability of GONR-IL was derived from the positive binding energy between IL and water, which ensured the stability of the emulsion in a wide pH range. Benefiting from the passivated surface chemistry of GONR, the emulsion microreactor stabilized by GONR-IL exhibited a remarkable stability over a wide range of pH values. A GONR-IL-supported Pd catalyst stabilized at the toluene-water interface achieved an excellent emulsion catalytic activity for benzyl alcohol oxidation (conversion of 92 %), which was exceedingly higher than that of Pd/GONR (<1 %), Pd/CNTs-IL (51 %), or Pd/GO-IL (8 %).

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.

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.

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.

N-Doped Porous Carbon Supported Au Nanoparticles for Benzyl Alcohol Oxidation

N-doped porous carbon (NPC) was produced through a simple and efficient method using biomass-derived pine sawdust as the carbon source, NH4Cl as nitrogen source and NaHCO3 as the activator. Both NPC and porous carbon (PC, prepared without nitrogen-doping) were used as support for Au nanoparticles to catalytic oxidation of benzyl alcohol. As expected, Au/NPC performs a substantially enhanced catalytic activity for benzyl alcohol oxidation in comparison with that of Au/PC (conversion of benzyl alcohol is 98.9% for Au/NPC and 51.4% for Au/PC under the same condition). The better catalytic performance of Au/NPC should be due to the introduction of N atoms into PC support, which not only adsorbs the benzyl alcohol molecules more easily, but also makes the Au nanoparticles smaller and more dispersed. Our experimental results also show that mild temperature (60 °C) is more beneficial for the reaction, O2 atmosphere is a necessity for benzyl alcohol oxidation and Au/NPC can also be used to catalyze oxidation of other aromatic alcohols.

Co2+ immobilized on highly ordered mesoporous graphitic carbon nitride (ompg-C3N4/Co2+) as an efficient and recyclable heterogeneous catalyst for one-pot tandem selective photo-oxidation/Knoevenagel condensation

Design and synthesis of efficient heterogeneous photocatalysts is an important task for practical applications due to the increasing environmental challenges and energy crisis. In this work, Co2+ modified highly ordered mesoporous graphitic carbon nitride (ompg-C3N4/Co2+) was prepared through a simple procedure involving sonication treatment. The obtained catalyst was characterized using FT-IR, XRD, ICP-OES, FE-SEM, UV–vis DRS, N2 adsorption-desorption, and TGA. It was found that the ompg-C3N4/Co2+ can function as a multifunctional heterogeneous photocatalyst for the one-pot tandem selective photo-oxidation/ Knoevenagel condensation. More interestingly, the obtained ompg-C3N4/Co2+ represented a high photocatalytic activity in benzyl alcohol oxidation without any oxidant under air atmosphere and visible light irradiation.

Formation of PdO on Au–Pd bimetallic catalysts and the effect on benzyl alcohol oxidation

A series of catalysts consisting of gold–palladium bimetallic nanoparticles (Au–Pd NPs in the range of 1–6 nm) anchored on foamlike mesoporous silica were used for the aerobic oxidation of benzyl alcohol. A remarkable synergistic effect was observed on these Au–Pd NP catalysts prepared by a one-pot method. Both experimental and theoretical study revealed a close relationship between the surface PdO species on the catalysts and their catalytic performance; that is, higher surface PdO content leads to lower catalytic activity. The surface content of PdO species on the catalysts could be tuned by controlling the Au/Pd ratios, because the formation of Au–Pd alloy NPs and electron transfer between surface Au and Pd atoms prevented the oxidation of surface Pd and retarded the formation of PdO species. An optimal Au/Pd ratio of 1/4.5 on the foamlike mesoporous silica support was obtained, with nearly no surface PdO species formed, and resulted in the highest benzyl alcohol conversion of 96%. The bimetallic Au–Pd catalysts exhibited much higher catalytic activity for benzyl alcohol oxidation (TOF = 50,000–60,000 h−1) than the monometallic Pd catalyst (TOF = 12,500 h−1), on which surface Pd is easily oxidized to PdO. These results provide direct evidence for the synergistic effect of Au–Pd bimetallic catalysts in benzyl alcohol oxidation.

Benzyl alcohol oxidation with Pd-Zn/TiO2: computational and experimental studies

ABSTRACT Pd–Zn/TiO2 catalysts containing 1 wt% total metal loading, but with different Pd to Zn ratios, were prepared using a modified impregnation method and tested in the solvent-free aerobic oxidation of benzyl alcohol. The catalyst with the higher Pd content exhibited an enhanced activity for benzyl alcohol oxidation. However, the selectivity to benzaldehyde was significantly improved with increasing presence of Zn. The effect of reduction temperature on catalyst activity was investigated for the catalyst having a Pd to Zn metal molar ratio of 9:1. It was found that lower reduction temperature leads to the formation of PdZn nanoparticles with a wide particle size distribution. In contrast, smaller PdZn particles were formed upon catalyst reduction at higher temperatures. Computational studies were performed to compare the adsorption energies of benzyl alcohol and the reaction products (benzaldehyde and toluene) on PdZn surfaces to understand the oxidation mechanism and further explain the correlation between the catalyst composition and its activity.

Benzyl Alcohol Oxidation Using Gold Catalysts Derived from Au8 Clusters on TiO2

Atomically-precise gold clusters have gained attraction in catalysis due to high fraction of low-coordinated gold atoms, unique structural geometry and ligand effect. Phosphine-ligated gold clusters offer an advantage in the light of the labile gold-phosphorous bond for easy ligand removal. Here, heterogeneous gold catalysts were prepared by depositing atomically-precise phosphine-ligated gold clusters, Au8(PPh3)8(NO3)2 onto anatase-phase TiO2 nanoparticles. The catalysts were then calcined under two different conditions: O2 (Au8/TiO2:O2) and O2 followed by H2 (Au8/TiO2:O2–H2) at 200 °C, to dislodge phosphine ligands from the Au core. It was found that Au8/TiO2:O2–H2 catalyst showed a decent catalytic activity in benzyl alcohol oxidation while Au8/TiO2 and Au8/TiO2:O2 were completely inactive. Such results imply that small-size gold clusters (2–3 nm) alone do not always contribute to high catalytic activity of gold catalysts. It is suggested that the presence of NO3− species defines the catalytic activity of supported gold clusters in benzyl alcohol oxidation in the case of these catalysts and reinforces our initial claim in the previous work.

The Evolution of Gold Nanoparticles in the Presence of Configurational Ion Cu2+ of Hydrotalcites Supports

AbstractControlled synthesis of gold nanoparticles had attracted much attention in catalysis. The evolution of gold nanoparticles by impregnation was investigated in the presence of configurational ion Cu2+ of hydrotalcites supports. The formation of Au nanoparticles experienced two steps. In the drying step, part of Au ions was reduced by H2O. The reducing extents of Au ions and the dispersion of Au nanoparticles were affected by configurational ion Cu2+ in the hydrotalcites supports. In the reduction step, all the residue Au ions were reduced by H2 and the Au nanoparticles formed in the previous step was redistributed. Both the redistribution of Au nanoparticles formed in the previous step and the distribution of Au nanoparticles formed in the second step was affected by the surface reaction between Au on the surface of supports and Cu embedded in the supports. The surface reaction controlled the dispersion of Au nanoparticles. The size of gold nanoparticles was 2.7 nm, which showed high activity in benzyl alcohol oxidation with benzaldehyde yield of 95%.

Aerobic Oxidation of Benzyl Alcohol on a Strontium-Based Gold Material: Remarkable Intrinsic Basicity and Reusable Catalyst

The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)2 by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of O2 and without extra-base addition, the calcined support reached 54.6% (100 °C) and 67.4% (140 °C) of conversion, presenting the remarkable and unexplored intrinsic basicity that strontium-based materials retain. With sub-stoichiometric K2CO3 adding, under the same catalytic conditions, the catalyst conducted the reaction with similar activity, but with excellent reusability in the process, without any gold leaching. We investigated the influence that the support synthesis method and the solvent used for the NPs stabilization have on the oxidation activity. The produced materials were fully characterized by XPS, Rietveld refinement, and TEM.

Catalytic oxidation of alcohols with novel non-heme N4-tetradentate manganese(ii) complexes.

We report the preparation and characterisation of a series of novel non-heme N4-tetradentate Mn(OTf)2 complexes of the type, [(L)MnOTf2], where L = R,R and S,S enantiomers of BPMCN, its 6-methyl and 6-bromo derivatives as well as the novel ligand BMIMCN (BPMCN = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-(R,R/S,S)-1,2-diaminocyclohexane, BMIMCN = N,N'-dimethyl-N,N'-bis(1-methyl-2-imidazolemethyl)-(R,R/S,S)-1,2-diaminocyclohexane). Solid state structural analysis of the BMIMCN-ligated Mn-triflate complexes (R,R-C4 and S,S-C4) revealed opposite helicity but identical metal site accessibility. This feature was exploited in the catalytic oxidation of primary and secondary alcohols, with hydrogen peroxide as oxidant and acetic acid as co-catalyst. Complexes R,R-C4 and S,S-C4 displayed the highest activity in benzyl alcohol oxidation, attributed to the electron-donating property of the BMIMCN ligand. Complex S,S-C4, displayed high activity for a variety of primary alcohol substrates, but the reaction suffered from reduced selectivity and side-reactions due to the presence of acetic acid. In contrast, secondary alcohol substrates could be oxidised to the corresponding ketone products in excellent isolated yields under mild reaction conditions and short reaction times.

Efficient and recyclable novel Ni‐based metal–organic framework nanostructure as catalyst for the cascade reaction of alcohol oxidation–Knoevenagel condensation

A novel Ni‐based metal–organic framework (Ni‐MOF) with a Schiff base ligand as an organic linker, Ni3(bdda)2(OAc)2⋅6H2O (H2bdda = 4,4′‐[benzene‐1,4‐diylbis(methylylidenenitrilo)]dibenzoic acid), was synthesized and characterized using powder X‐ray powder diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, elemental analysis and Fourier transform infrared spectroscopy. The synthesized Ni‐MOF exhibited a high catalytic activity in benzyl alcohol oxidation using tert‐butyl hydroperoxide under solvent‐free conditions. Also, the efficiency of the catalyst was investigated in the cascade reaction of oxidation–Knoevanagel condensation under mild conditions. The Ni‐MOF catalyst could be recovered and reused four times without significant reduction in its catalytic activity.

Solvent Effects on Preparation of Pd-Based Catalysts: Influence on Properties of Palladium and Its Catalytic Activity for Benzyl Alcohol Oxidation

Solvent effects are important for the solution preparation of nanoscale metal materials, in which the sizes and properties of the nanomaterials are greatly influenced by the solvents. In this study, a series of Pd/XC-72 catalysts were synthesized by a facile solvothermal method in solvents with different numbers of hydroxyl groups, including ethanol, ethylene glycol, and glycerine. The as-prepared catalysts Pd/XC-72(EA), Pd/XC-72(EG) and Pd/XC-72(GI) were characterized by XRD, TEM, TGA, ICP-MS and multipoint nitrogen adsorption-desorption experiments. It was found that Pd/XC-72(GI) had the highest metallic dispersion and the smallest particle size (4.9 nm). Furthermore, Pd/XC-72(GI) exhibited the best catalytic performance for solvent-free selective oxidation of benzyl alcohol while the catalytic activities of Pd/XC-72 catalysts decreased in the order: Pd/XC-72(GI) > Pd/XC-72(EG) > Pd/XC-72(EA).

Cu and Fe-doped monolacunary tungstosilicate catalysts with efficient catalytic activity for benzyl alcohol oxidation and simulation gasoline desulfurization

The heterogeneous catalysts of Fe and Cu-doped monolacunary tungstosilicate have been prepared and characterized by SEM, XRD, IR, XPS, ICP, TG-DSC and H2-TPR techniques. The influence factors on the structure of catalysts and catalytic properties have been investigated, such as the additive graphite, doped amount and calcination temperature. After being calcined at appropriate temperature, the graphite was totally decomposed and catalysts of irregular bulk-type structure were converted to uniform nanoplate materials. The catalytic activity of as-prepared catalysts was evaluated by the benzyl alcohol selective oxidation and the simulation gasoline desulfurization. It is proved that transition metal Cu/Fe-codoped tungstosilicates are more active than the corresponding undoped compounds under mild conditions and Cu/Fe-doped amount greatly impacted the catalytic activity, and Cu1.00Fe1.00SiW11 sample exhibited the best catalytic activity with 98.0% conversion and 98.3% selectivity in benzyl alcohol selective oxidation into benzaldehyde at 80°C only for 60min, and above 98% of the desulfurization rate at 65°C just for 80min.