Conversion Of Benzyl Alcohol Research Articles

Physico-chemical properties and catalytic activity of the sol-gel prepared Ce-ion doped LaMnO3 perovskites

Ce-doped LaMnO3 perovskite ceramics (La1−xCexMnO3) were synthesized by sol-gel based co-precipitation method and tested for the oxidation of benzyl alcohol using molecular oxygen. Benzyl alcohol conversion of ca. 25–42% was achieved with benzaldehyde as the main product. X-ray diffraction (XRD), thermogravimetric analysis (TGA), BET surface area, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2-TPR), temperature-programmed oxidation (O2-TPO), FT-IR and UV-vis spectroscopic techniques were used to examine the physiochemical properties. XRD analysis demonstrates the single phase crystalline high purity of the perovskite. The Ce-doped LaMnO3 perovskite demonstrated reducibility at low-temperature and higher mobility of surface O2-ion than their respective un-doped perovskite. The substitution of Ce3+ ion into the perovskite matrix improve the surface redox properties, which strongly influenced the catalytic activity of the material. The LaMnO3 perovskite exhibited considerable activity to benzyl alcohol oxidation but suffered a slow deactivation with time-on-stream. Nevertheless, the insertion of the A site metal cation with a trivalent Ce3+ metal cation led to an enhanced in catalytic performance because of atomic-scale interactions between the A and B active site. La0.95Ce0.05MnO3 catalyst demonstrated the excellent catalytic activity with a selectivity of 99% at 120 °C.

Ru nanoparticles supported on N-doped reduced graphene oxide as valuable catalyst for the selective aerobic oxidation of benzyl alcohol

The catalytic performance of a series of Ru-based catalysts was evaluated for the selective aerobic oxidation of benzyl alcohol to benzaldehyde under base-free mild conditions. The effect of metal precursor (RuCl3, RuNO(NO3)3 and Ru3(CO)12) and support on catalyst performance was investigated by comparing undoped (rGO) and N-doped (NrGO) reduced graphene oxide with commercial activated carbon and high surface area graphite supports. The surface chemistry and structure of materials were characterized by nitrogen physisorption (BET), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The average Ru nanoparticle sizes were in the range from 1.4 to 2.4 nm, with the smallest particle sizes obtained on rGO support owing to its highest surface area.Catalysts prepared from RuNO(NO3)3 and Ru3(CO)12 precursors exhibit the highest benzyl alcohol conversion to the corresponding aldehyde, with highest conversions observed when NrGO support is employed. Catalysts prepared from Ru3(CO)12 on NrGO support exhibit the highest activity for benzaldehyde formation, which is over three times that of commercial activated carbon supported Ru catalysts.The differences in catalytic performance are attributed to interactions between the acidic product of the reaction and the basic surface sites of the NrGO support, and modification of the surface hydrophobicity. These factors confer a significant rate enhancement in the selective oxidation of benzyl alcohol over Ru/NrGO compared to Ru/rGO. Ru/NrGO is stable under reaction conditions, however progressive deactivation is observed owing to water accumulation at the active site. Catalysts are easily reactivated via heating, with >90% of the original activity recovered on reuse.

Oxygen‐Vacancy‐Mediated Photocatalysis over Bi2Sn2O7: Exceptional Catalytic Activity and Selectivity

AbstractA series of Bi2Sn2O7 photocatalysts was developed with the aim to regulate defect chemistry as well as electronic structure by modulating the charge states of tin species for boosting photocatalytic selective oxidation of alcohols performance. Defective centers, such as oxygen vacancies (OVs), were beneficial to enhancing the adsorption and activation of molecular oxygen. Meanwhile, the valence band edge potential of Bi2Sn2O7 with higher OVs content exhibited a distinct downshift, improving the thermodynamical driving force of photooxidation. Additionally, OVs contributed to promoting the separation efficiency of photogenerated carriers, which can be confirmed by the surface photovoltage measurement. By optimizing the electronic structure as well as defect chemistry, the optimal benzyl alcohol conversion efficiency was 76.0 % with selectivity toward benzaldehyde being about 100 %. It's found that photogenerated holes and .O2− active species played critical role in photocatalytic aerobic oxidation. This work may provide a novel insight to clarify the role of defect chemistry during the selective benzyl alcohol oxidation over Bi2Sn2O7 photocatalyst.

High Performance Cu2 O–CoO/SiC Nanocomposites for Gas-Phase Oxidation of Benzyl Alcohol to Benzaldehyde

High-performance CoO–Cu2 O/SiC is prepared for the gas-phase aerobic oxidation of benzyl alcohol of benzaldehyde, which delivers much higher catalytic performance (92% benzyl alcohol conversion and 99% selectivity at 260 °C) than the solo CoO/SiC and Cu2 O/SiC. TEM image indicates that the small size CoO and Cu2 O nanoparticles are homogeneously distributed on the support. Control experiments indicate that Cu2 O–CoO interfaces are responsible for their better reaction performance.

Mannich base Cu(II) complexes as biomimetic oxidative catalyst

Galactose Oxidase (GOase) and catechol oxidase (COase) are the metalloenzymes of copper having monomeric and dimeric sites of coordination, respectively. This paper summarizes the results of our studies on the structural, spectral and catalytic properties of new mononuclear copper (II) complexes [CuL(OAc)] (1), and [CuL2] (2), (HL = 2,4‑dichloro‑6‑{[(2′‑dimethyl‑aminoethyl)methylamino]methyl}‑phenol) which can mimic the functionalities of the metalloenzymes GOase and COase. The structure of the compounds has been elucidated by X-ray crystallography and the mimicked Cu(II) catalysts were further characterized by EPR. These mimicked models were used for GOase and COase catalysis. The GOase catalytic results were identified by GC–MS and, analyzed by HPLC at room temperature. The conversion of benzyl alcohol to benzaldehyde were significant in presence of a strong base, Bu4NOMe in comparison to the neutral medium. Apart from that, despite of being monomeric in nature, both the homogeneous catalysts are very prone to participate in COase mimicking oxidation reaction. Nevertheless, during COase catalysis, complex 1 was found to convert 3,5‑ditertarybutyl catechol (3,5-DTBC) to 3,5‑ditertarybutyl quinone (3,5-DTBQ) having greater rate constant, kcat or turn over number (TON) value over complex 2. The generation of reactive intermediates during COase catalysis were accounted by electrospray ionization mass spectrometry (ESI-MS). Through mechanistic approach, we found that H2O2 is the byproduct for both the GOase and COase catalysis, thus, confirming the generation of reactive oxygen species during catalysis. Notably, complex 1 having mono-ligand coordinating atmosphere has superior catalytic activity for both cases in comparison to complex 2, that is having di-ligand environment.

HKUST-1 catalyzed efficient in situ regeneration of NAD+ for dehydrogenase mediated oxidation

The combination of enzymatic and chemical reactions to achieve co-operative chemo-enzymatic processes has presented many challenges for decades. In this work, alcohol dehydrogenase (ADH) was encapsulated into metal-organic framework HKUST-1 crystals through an in situ approach to construct a synergistic chemo- and bio-catalysis system, where ADH was for the conversion of benzyl alcohol to benzaldehyde, and HKUST-1 was in charge for the regeneration of β-nicotinamide adenine dinucleotide (NAD+, the oxidized cofactor). It was found that HKUST-1 was a versatile catalyst for efficient oxidation of NADH in different buffers. The Michaelis-Menten kinetic parameters of immobilized ADH exhibited an increased KM (approximately 1.3-fold) and a decreased Vmax (approximately 4.7-fold) compared to free ADH. Due to the protection of HKUST-1, the immobilized enzyme showed a better resistance against urea and organic solvents compared with free enzyme, and still maintained 93% of its original activity after 6 cycles. The immobilized enzyme was successfully applied to the enzymatic transformation of benzyl alcohol to benzaldehyde in aqueous media at room temperature. Owing to the oxidized cofactor regeneration by HKUST-1, ADH@HKUST-1 composites achieved a benzaldehyde yield of 28.5%, which was approximately 4.3-fold higher than that of the individual bio-catalysis. This concept of combining chemo- and bio-catalysis may provide a novel and versatile technique for applications in biochemical catalysis, biosensors and drug delivery.

Controllable synthesis of novel nanoporous manganese oxide catalysts for the direct synthesis of imines from alcohols and amines

Abstract A novel template-free oxalate route was applied to synthesize different mesoporous manganese oxides (amorphous manganese oxide (AMO), Mn5O8, Mn3O4, MnO2) in the narrow temperature range from 350 °C to 400 °C by controlling the calcination conditions, which were employed as the efficient catalysts for the oxidative coupling of imines from alcohols and amines. The chemical and structural properties of the manganese oxides were characterized by the methods of thermal analysis and heat flow (TG-DSC), X-ray diffraction (XRD), nitrogen sorption, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), and inductively coupled plasma optical emission spectrometry (ICP-OES) techniques. The structures of different manganese oxides were confirmed by characterization. The M-350 (AMO) presented the maximum surface area, amorphous nature, the lowest reduction temperature, the higher (Mn3+ + Mn4+)/Mn2+ ratio, and the higher adsorbed oxygen species compared to other samples. Among the catalysts, M-350 showed the best catalytic performance using air as an oxidant, and the conversion of benzyl alcohol (BA) and the selectivity of N-benzylideneaniline (NBA) reached as high as 100% and 97.1% respectively at the lower reaction temperature (80 °C) for 1 h. M-350 had also the highest TOF value (0.0100 mmol·mg−1·h−1) compared to the other manganese oxide catalysts. The catalyst was reusable and gave 95.8% conversion after 5 reuse tests, the XRD pattern of the reactivated M-350 did not show any obvious change. Lattice oxygen mobility and (Mn3+ + Mn4+)/Mn2+ ratio were found to play the important roles in the catalytic activity of aerobic reactions.

Efficient Conversion of Benzyl Alcohol on a Mesoporous Co3O4

High-efficiency conversion of benzyl alcohol to benzaldehyde on heterogeneous catalysts using oxygen as oxidant is important in industrial catalysis due to economic and environmentally friendly sup...

Continuous flow aerobic oxidation of benzyl alcohol on Ru/Al2O3 catalyst in a flat membrane microchannel reactor: An experimental and modelling study

A flat Teflon AF-2400 membrane microchannel reactor was experimentally and theoretically investigated for aerobic oxidation of benzyl alcohol on a 5 wt% Ru/Al2O3 catalyst. The reactor consisted of gas and liquid channels (75 mm (L) × 3 mm (W) × 1 mm (D)), separated by a 0.07 mm thick semipermeable Teflon AF-2400 flat membrane, which allowed continuous supply of oxygen during the reaction and simultaneously avoided direct mixing of gaseous oxygen with organic reactants. A catalyst stability test was first carried out, and the experimental data obtained were used to estimate the kinetics of benzyl alcohol oxidation with a 2D reactor model. Using these kinetics, predictions from the 2D reactor model agreed well with the experimental data obtained at different liquid flow rates and oxygen pressures. The mass transfer and catalytic reaction in the membrane microchannel reactor were then theoretically studied by changing the membrane thickness, the liquid channel depth, and the reaction rate coefficient. Oxygen transverse mass transport in the catalyst bed was found to be the controlling process for the system investigated, and decreasing the liquid channel depth is suggested to improve the oxygen supply and enhance the benzyl alcohol conversion in the membrane reactor.

Thermal control of the defunctionalization of supported Au25(glutathione)18 catalysts for benzyl alcohol oxidation.

Au25(SG)18 (SG – glutathione) clusters deposited on ZrO2 nanoparticles have been used as a catalyst for benzyl alcohol oxidation. Calcination was performed at different temperatures to study the ligand and particle size effect on the catalytic activity. In contrast to most gold nanoclusters which have to be completely defunctionalized for maximum catalytic activity, the partially defunctionalized Au25(SG)18@ZrO2 catalyst, thermally treated at 300 °C, exhibits full conversion of benzyl alcohol within 15 h under atmospheric pressure with 94% selectivity towards benzaldehyde.

Metal nanoparticles decorated MIL-125-NH2 and MIL-125 for efficient photocatalysis

Metal nanoparticles (NPs) decorated MOFs for photocatalysis has drawn enormous attention in the past decade. Here, a series of M/Ti-MOFs (M = Pt and Au, Ti-MOFs = MIL-125-NH2 and MIL-125) has been synthesized through a facile post-synthetic method and the metal NPs highly dispersed on surface of MOFs with major sizes of 3–9 nm. Light absorption edges of scaffolds are crucial in the photocatalytic oxidation of benzyl alcohol over M/MIL-125-NH2 and M/MIL-125. The conversion of benzyl alcohol over Pt/MIL-125-NH2 is 2.4 times and 1.9 times higher than that of pristine MIL-125-NH2 and Au/MIL-125-NH2, respectively. Besides, Pt/MIL-125-NH2 photocatalyst also exhibited good activity for Cr(VI) reduction compared to that of MIL-125-NH2. The enhanced photocatalytic activity of Pt/MIL-125-NH2 is contributed to the rapid transfer of photo-induced electrons and decreased recombination of electron-hole pairs, which is verified by measurements of photocurrent and Electrochemical Impedance Spectroscopy. We hope that this study will provide worthy information for designing metal/MOFs or metal/MOFs-NH2 photocatalysts.

Synthesis of benzaldehyde with high selectivity using immobilized AuNPs and AuNPs@zeolite in a catalytic microfluidic system.

In the present work, gold based catalysts were synthesized and immobilized on the surface of cyclic olefin copolymer (COC) microreactors. The microreactors were subsequently applied in a homemade microfluidic system for synthesizing benzaldehyde by oxidation of benzyl alcohol in water medium. The Au nanoparticles (NPs) immobilized on the inner surface of the microchannel showed a very high selectivity (94%) for benzaldehyde, while zeolite NPs exhibited only an adsorption feature to this reaction. Moreover, the results showed that the AuNP catalytic activity was maintained for at least 9 hours. However, the obtained conversion with AuNPs was only 20%, indicating a relatively low productivity. In comparison, AuNPs assembled on the surface of zeolite NPs (AuNPs@zeolite) and immobilized in the microchannel showed the best catalytic performance, as the highest benzaldehyde selectivity (>99%) with a relatively high benzyl alcohol conversion of 42.4% was achieved under the same conditions. To the best of our knowledge, this is the first example demonstrating the use of AuNP or AuNP@zeolite catalysts in a microsystem performing such high selectivity for benzaldehyde in water medium.

Noble metal nanoparticle-functionalized Zr-metal organic frameworks with excellent photocatalytic performance

Noble metal nanoparticles (NPs) functionalized MOFs are attractive materials for photocatalytic reactions, and outstanding catalytic performances can be expected, especially when they have intrinsically matched crystal faces between metals and MOFs. This study discovered that the photocatalytic oxidation of aromatic alcohols to aldehydes was enhanced over Au/UiO-66-NH2 or Au/UiO-66 but suppressed over Pt loaded counterparts, whereas the reduction of Cr(VI) was boosted over both two catalysts. In reactions, the conversion of benzyl alcohol was 17.1% over UiO-66-NH2 and 7.6% over UiO-66, and an enhanced conversion was obtained over Au/UiO-66-NH2 (30.5%) and Au/UiO-66 (24.1%). However, the conversion was decreased over Pt/UiO-66-NH2 (9.3%) and Pt/UiO-66 (<1%). Experimental results revealed strong correlations between Zr-MOFs and loaded metal NPs, as Zr centers promoted the formation of Pt(200) planes that suppressed the production of ·O2− intermediates to oxidize aromatic alcohols, whereas Pt(200) exhibited no effect on the Cr(VI) reduction triggered by photo-induced electrons. The findings in this study on constructing noble metal NPs functionalized Zr-MOFs catalysts with specially-matched crystal structures and on distinguishing photocatalytic mechanisms on oxidation of alcohols and reduction of Cr(VI) would provide valuable information for designer (photo)catalysts based on MOFs and their applications in such as catalysis and environmental remediation.

Synthesis, Crystal Structure, and Catalytic Activity of a Calcium(II) Complex with 4-Formylbenzene-1,3-disulfonate-isonicotinic Acid Hydrazone

A new calcium(II) complex was synthesized by one-pot synthesis method from disodium 4-formylbenzene-1,3-disulfonate, isonicotinic acid hydrazide and Ca(ClO4)2•2H2O. The structure of calcium(II) complex was determined by elemental analysis, IR and single crystal X-ray diffraction. The results show that the Ca(II) complex molecules form 3D network structure by the interactions of π-π stacking and hydrogen bonds. The Ca(II) complex catalyst could efficiently catalyse oxidation of benzylic alcohol with good conversion of benzyl alcohol (78 %) and excellent selectivity of benzaldehyde (98 %).

Aerobic Oxidation of Alcohols Catalyzed by V2O5 Rods Decorated on Graphene Oxide

AbstractThe present work reports the preparation of two different nanocomposites, namely, 5 wt% V2O5 rods supported on graphene oxide (GO) (GV1) and 10 wt% V2O5 rods supported on GO (GV2). These nanocomposites are prepared by mixing V2O5 precursor and GO suspension with the assistance of sonication method as a non conventional source of energy. The structural features of these nanocomposites are characterized by powder X‐ray diffraction (XRD), Fourier transform‐infrared spectroscopy (FT‐IR), Raman, scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM) and UV‐Visible spectroscopy. These analyses confirm the existence of V2O5 rods decorated on GO sheets. Furthermore, the catalytic activity of these nanocomposites is examined in the aerobic oxidation of benzyl alcohol under mild reaction conditions. The observed catalytic data indicate that the present experimental conditions afford complete conversion of benzyl alcohol with 100% selectivity to benzaldehyde with GV2 as a solid catalyst. On the other hand, this catalyst is also effective to promote secondary alcohol oxidation to its corresponding carbonyl compound, thus demonstrating wide substrate scope. The reusability experiments indicate that the activity is decreased in consecutive recycles in the aerobic oxidation of benzyl alcohol. On the other hand, the process is heterogeneous in nature as evidenced by hot filtration experiment.

Graphene Oxide: Carbocatalyst or Reagent?

Metal-free heterogeneous carbon-based materials have the potential to facilitate a wide range of organic transformations in an economical and environmentally-friendly manner. However, the mechanism of their action is often obfuscated by their ill-defined nature, so careful analysis of the reaction products is essential before they can be labelled "catalysts" in accordance with the IUPAC definition. We present here our findings on the archetypal "carbocatalytic" conversion of benzyl alcohol to benzaldehyde, in which graphene oxide is reduced and a major side product, dibenzyl ether, is also formed. Thus, our work reclassifies graphene oxide as a reagent and presents an important step in the proper evaluation of reactions in the nascent field of carbocatalysis.

Graphene Oxide: Carbocatalyst or Reagent?

AbstractMetal‐free heterogeneous carbon‐based materials have the potential to facilitate a wide range of organic transformations in an economical and environmentally‐friendly manner. However, the mechanism of their action is often obfuscated by their ill‐defined nature, so careful analysis of the reaction products is essential before they can be labelled “catalysts” in accordance with the IUPAC definition. We present here our findings on the archetypal “carbocatalytic” conversion of benzyl alcohol to benzaldehyde, in which graphene oxide is reduced and a major side product, dibenzyl ether, is also formed. Thus, our work reclassifies graphene oxide as a reagent and presents an important step in the proper evaluation of reactions in the nascent field of carbocatalysis.

Magnetically recoverable Fe3O4/g-C3N4 composite for photocatalytic production of benzaldehyde under UV-LED radiation

Selective production of aromatic aldehydes is an important challenge in the synthesis of fine chemicals. This study presents a viable strategy for the production of benzaldehyde using a magnetic recoverable photocatalyst. Graphitic carbon nitride was submitted to a thermal post-treatment, for partial exfoliation (g-CN-T) and combined with magnetic nanoparticles of Fe3O4. The composite containing 18 wt.% of Fe3O4 shows a remarkable magnetic response. The efficiency of this composite was evaluated in the selective photocatalytic conversion of benzyl alcohol into benzaldehyde. A good compromise was observed in terms of selectivity for benzaldehyde formation and ability of recovery at the end of the photocatalytic reaction by the application of a magnetic field. Reutilization experiments using this hybrid material revealed a slight decrease of efficiency after the first run only. Moreover, hydrogen was generated during the photocatalytic production of benzaldehyde. Thus, the combination of gCN-T and magnetic nanoparticles provided an impetus to design a photocatalyst with easy and inexpensive features for selective synthesis of organic compounds.

Supported Ag Catalysts on Mg–Al Oxides toward Oxidant-Free Dehydrogenation Reaction of Benzyl Alcohol

Oxidant-free dehydrogenation of alcohols has attracted considerable attention, owing to the largely improved utility value of alcohols. Herein, mixed metal oxides (MMOs) via topological transformation of Mg–Al hydrotalcite precursors were prepared and used as support for the immobilization of metallic Ag nanoparticles. The resulting Ag/MgAl-MMO shows an excellent catalytic performance toward oxidant-free dehydrogenation of benzyl alcohol (conversion of benzyl alcohol: 95.9%; selectivity of benzaldehyde: 93.3%), which is close to platinum-group catalysts commonly used in this reaction. A combination study based on a series of characterization methods reveals a synergistic catalysis between Agδ+ and medium-strong acid/basic sites (Mgδ+–Oδ−) from support: Agδ+ facilitates the breakage of α-C–H bond while Mgδ+–Oδ− accelerates the cleavage of O–H bond. This work provides an effective approach to enhance catalytic behavior toward dehydrogenation reactions by virtue of metal–support interactions.

TiO2 nanorods loaded with Au[sbnd]Pt alloy nanoparticles for the photocatalytic oxidation of benzyl alcohol

In this study, homogeneous alloy AuPt nanoparticles were successfully immobilized on ultrathin TiO2 nanorods via a facile photodeposition technique. The AuPt/TiO2 hybrid exhibited high photocatalytic activity and stability during the selective photosynthesis of benzaldehyde from benzyl alcohol under visible light. The optimal performance was obtained with the Au1Pt1/TiO2 sample, which had a benzyl alcohol conversion rate of 65.3%. The engineered TiO2 nanorods (304 m2/g) can be employed as a stabilizing matrix and an excellent dispersant for noble metal particles. Moreover, the formation of the alloy structure substantially enhances the photoinduced carrier separation efficiency compared with loading Au or Pt alone on TiO2. The bimetallic nanoparticles exhibited the properties related to the individual metals, as well as new properties due to synergistic effects of the electron-accumulating function of Pt and the surface plasmon resonance of Au.