Catalyst For Oxidation Of Alcohols Research Articles

Review—In Situ X-ray and Infrared Spectroscopic Studies of Electrochemical Systems

Despite of intense research and a wealth of data, the phenomena occurring during electrocatalysis are still a major obstacle in many chemical processes. Molecular analysis of the electrode/electrolyte interface is needed to correctly describe the reaction through identifying the species involved, their interaction with the environment and kinetics in situ, i.e. while the reaction is taking place. That can be done by coupling the electrochemical system with complementary non-electrochemical techniques. Particularly revealing are in situ X-ray spectroscopic techniques to analyze the electrode itself, providing the information on the changes in the catalyst during the reaction. The synergy of the traditional electrochemical techniques with the complementary spectroscopic methodologies offer understanding of the electrode/electrolyte interface above and beyond traditional experimental mainframe. Here we demonstrate how in situ X-ray absorption spectroscopy (XAS), in situ infrared reflection/absorption spectroscopy (IRRAS), and traditional voltammetric studies can increase our understanding of electrochemical processes during oxidation of ethanol. The results show the pronounced role of electrode surface in determining reaction kineticks and revealed the selectivity of the catalyst to complete oxidation pathway. They further provide understanding of the parameters that enhance its oxidation for future designing catalysts for alcohol oxidation fuel cells.

Generation of Triplet States by Host‐Stabilized Through‐Space Conjugation for the Construction of Efficient Supramolecular Photocatalysts

AbstractPromoting the generation of triplet states is essential for developing efficient photocatalytic systems. This research presents a novel approach of host‐stabilized through‐space conjugation via the combination of covalent and non‐covalent methods. The designed building block, 4,4′‐(1,4(1,4)‐dibenzene cyclohexaphane‐1,4‐diyl)bis(1‐phenylpyridinium) chloride, features inherently stable through‐space conjugation. When this block forms a 1 : 1 host–guest complex with cucurbit[8]uril, the through‐space conjugation is further stabilized within the confined cavity. Both the generation and lifetime of triplet state are significantly increased, resulting from the host‐stabilized through‐space conjugation. Additionally, the ultrahigh binding constant of 6.58×1014 M−1 ensures the persistence of host‐stabilization effect. As a result, the host–guest complex acts as a highly efficient catalyst in the photocatalytic oxidation of thioether and aromatic alcohol. In the photodegradation of lignin, a complex natural product, the host–guest complex also exhibits high efficiency, demonstrating its robustness. This line of research is anticipated to enrich the toolbox of supramolecular photochemistry and provide a strategy for fabricating efficient supramolecular photocatalysts.

Construction of Multiphase Concave Tetrahedral PdInMo Nanocatalyst for Enhanced Alcohol Oxidation

AbstractHeterogeneous palladium‐based catalysts show excellent catalytic properties for electrocatalytic oxidation of alcohols, but the construction of such heterogeneous catalysts is a challenge. Here, a multiphase tetrahedral PdInMo nanocatalyst is prepared by a one‐pot reaction method. And the multiphase tetrahedral PdInMo nanocatalyst consists of a face‐centered cubic structure and an intermetallic structure. Due to the oxygen affinity of indium and molybdenum atoms, the interface defects of internal multiphase structure, and intermetallic structure, the multiphase concave tetrahedral PdInMo nanocatalyst shows enhanced catalytic efficiency in the electrocatalytic oxidation reaction of methanol and ethanol. Compared with commercial Pd/C catalysts, PdIn0.117Mo0.037 nanocatalyst has the best mass activity and specific activity. In electrocatalysis of methanol oxidation, the mass activity (2205.57 mA mgPd−1) and specific activity (6.67 mA cm−2) are 4.81 and 3.40 times than that of a commercial Pd/C nanocatalyst (458.5 mA mgPd−1, 1.96 mA cm−2), respectively. In the electrocatalysis of ethanol oxidation, the mass activity (2668.49 mA mgPd−1) and specific activity (8.11 mA cm−2) are 4.06 and 3.14 times than that of the commercial Pd/C nanocatalyst (655.83 mA mgPd−1, 2.58 mA cm−2), respectively. This study provides a reference for the design of highly efficient palladium catalysts for alcohol oxidation.

In situ-generated mononuclear half-sandwich [(η6‐p‐cymene)RuCl(amide)] complexes as efficient catalysts in the selective oxidation of benzyl alcohol to benzaldehyde

The application of in situ-generated mononuclear Ru(II)-organometallic complexes (1–7) i.e., [(η6-p-cymene)RuCl(L)], produced by the interaction of Ru dimer [(p-cymene)RuCl2]2 with some polyfunctional amide ligands(L) as highly efficient catalystsin the oxidation of various benzyl alcohols (B-OLs) by tert-butyl hydroperoxide (TBHP) oxidant to produce selectively the benzaldehydes (B-ALs) in high yields in CH3CN is described. The in situ-generated catalysts were found to be highly active than the [(p-cymene)RuCl2]2 precursor (dimer) in the oxidation of B-OL to B-AL. The influence of various reaction parameters such as type of catalyst, reaction temperature, oxidant and solvent during the B-OL oxidation was systematically monitored to optimize the catalytic conditions. In order to confirm the formation of predicted in situ-generated mononuclear Ru(II) complex catalysts during the oxidation of B-OL, one of the Ru(II) complex (1) was synthesized and characterized by Elemental analysis (EA), Infrared (IR), Proton-NMR and Mass spectral techniques and its mono nuclear structure is proposed. Further, it was observed that the activity of in-situ generated and pre-synthesized Ru(II) catalyst was almost same in the oxidation of B-OL to B-AL.

Nitrogen-doped mesoporous carbon as metal-free catalysts for the aerobic oxidation of alcohols

The selective oxidation of alcohols to carbonyl compounds is a crucial reaction in organic chemistry. In this study, we report the synthesis of nitrogen-doped mesoporous carbon material by hard template method using biomass derivative sucrose and melamine as carbon and nitrogen sources and silica sol as template agent. Using molecular oxygen as the oxidant, the obtained NC-900 exhibits excellent selectivity in the oxidation of primary alcohols to the corresponding aldehydes without generating over-oxidized acid. For example, under optimal reaction conditions, 4-methoxybenzyl alcohol is almost quantitatively converted to 4-methoxybenzaldehyde. The catalytic system showed robust tolerance to sensitive functional groups and demonstrated favorable reaction effects in gram-scale experiments and multi-step, one-pot reaction sequences. The catalyst was reused for 5 times, and its catalytic activity did not decrease significantly. Hammett correlation studies indicated that the reaction favored substrates with electron-donating substituents. Characterization and experimental results indicate that the synergistic effect of graphitic N and mesoporous structure plays a pivotal role in enhancing the catalytic activity of NC-900 in this transformation. The mechanism study shows that the reaction involves free radical process.

Electrodeposited Pt nanoparticles loaded on support composites of metal-organic frameworks and carbon quantum dots for the enhancement of alcohol electrooxidation

Metal-organic frameworks comprising divalent metal (M)-linked 4,4′-bipyridine (bpy), {[CuII4(bpy)3(OH)2(mal)3]·4H2O}n(Cubpy) and Ni2(bpy)3(NO3)4(H2O)4(Nibpy) were modified with carbon quantum dots (Mbpy/CQD; M = Cu, Ni) to prepare a composite support. Then, platinum (Pt) nanoparticles were electrodeposited onto the modified Mbpy/CQD support for the preparation of Pt-based catalysts (Pt/Mbpy/CQD) for the electrocatalytic improvement of alcohol oxidation. The influence of Mbpy with electrodeposited Pt nanostructures on CQD support electrodes is particularly discussed in detail through numerous physical characterizations, e.g., SEM, TEM, EDX, XPS, XRD, and elemental mapping. Dispersed Pt nanoparticles with diameters of 3-10 nm can be obtained on the modified Mbpy/CQD supports with suitable chemical and structural conditions for electrocatalytic oxidation improvement. The various prepared Pt/Mbpy/CQD catalysts with different compositions also enhance the kinetics of alcohol oxidation; they have a greater electrochemically active surface area (ECSA) and more development activity for alcohol oxidation than do the Pt/CQD catalysts. For the oxidation of all the selected small alcohol molecules, e.g., methanol, ethanol and isopropanol, the Pt/Cubpy/CQD catalyst composites also mostly exhibited improved catalytic activity, outstanding stability, and lower onset potential (Eonset) and CO tolerance. The favorable performance of the prepared composite catalysts is attributed to their superior ECSA owing to the suitable mixed surface of metal and functional groups of electrodeposited Pt, Mbpy, and CQD on the catalytic composites. Consequently, these as-prepared Pt/Mbpy/CQD composites, which are promising oxidative heterogeneous catalysts, can be used as active and stable catalysts for alcohol oxidation in alkaline solutions.

Phenanthroline-functionalized MCM-41-immobilized copper(I) chloride complex: A highly active and recyclable catalyst for aerobic oxidation of alcohols

A new 1,10-phenanthroline-functionalized MCM-41-immobilized copper(I) complex [MCM-41-Phen-CuCl] was prepared from 1-(1,10-phenanthrolin-5-yl)-3-(3-(triethoxysilyl)propyl)urea via immobilization on MCM-41, followed by reacting with copper(I) chloride. It was found that this heterogenized copper(I) complex is a highly efficient catalyst for the oxidation of a wide variety of alcohols into aldehydes and ketones using molecular oxygen as the stoichiometric oxidant and 5 mol% of di-tert-butyl hydrazine-1,2-dicarboxylate (DBAD-H2) as additive, and can be recycled more than eight cycles with almost consistent activity.

Ceria nanocatalyst-supported oxidative organic transformations of aromatic alcohols and p-nitrotoluene

Hydrothermally derived nanocubes of CeO2(10 nm) were explored as an efficient heterogeneous catalyst in the partial oxidation of aromatic alcohols to the corresponding aldehydes and aerobic oxidation ofp-nitrotoluene top-nitrobenzoic acid. The CeO2nanocatalyst was characterized by x-ray diffraction, transmission electron microscopy (TEM), energy dispersive spectroscopy, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis and ultraviolet-visible spectroscopy. TEM/high-resolution TEM micrographs reveal a morphology of mostly cubic nanostructures with exposed highly active {100} and {110} facets. The surface area of nanoceria was determined by BET analysis and found to be 33.8 m2g-1. To demonstrate the universality of the catalytic system, the selective oxidation of different substrates of benzylic alcohol and complete oxidation ofp-nitrotoluene was investigated under mild conditions. Absolute selectivity towards their respective aldehydes was found to be 99.50% (benzaldehyde), 90.18% (p-chlorobenzaldehyde), 99.71% (p-nitrobenzaldehyde), 98.10% (p-fluorobenzaldehyde), 94.66% (p-anisaldehyde) and 86.14% (cinnamaldehyde). Moreover, the catalytic oxidative transformation of nitrotoluene results in 100% conversion with 99.29% selectivity towards nitrobenzoic acid.

Material Dynamics of Nickel (oxy)Hydroxide As an Alcohol Oxidation Electrocatalyst

Electrochemical alcohol oxidation is an attractive reaction for renewable-energy driven production of value-added chemicals, like precursors for acrylic (acrolein from glycerol) and nylon (adipic acid from cyclohexanol). Implementing selective, earth-abundant catalysts for alcohol oxidation can improve electrolyzer efficiency and economics. For example, replacing the energy intensive oxygen evolution reaction (OER) in CO2 electrolyzers with alcohol oxidation can decrease operating voltage by about 0.85 V and reduce electricity requirements up to 53% while also reducing carbon emissions from chemical production.1 Electrochemical alcohol oxidation catalyzed by as synthesized nickel oxyhydroxide (NiOOH) is hypothesized to proceed through two pathways, a chemical, redox pathway preferred by aldehydes (geminal diols in alkaline electrolyte), and a potential dependent pathway preferred by alcohols.2 Many studies have focused on understanding reaction mechanisms and device performance, however, transition metal alcohol oxidation catalysts, such as NiOOH, are known to undergo reduction/oxidation, phase changes, and even dissolution in the same potential window as alcohol oxidation.3 It is still unclear how these processes affect catalyst material stability and electrochemical performance.In this work, we probe the performance stability and material stability of Ni(OH)2 for alcohol oxidation in alkaline media through electrochemical cycling and chronoamperometry. We use a rigorously Fe-free environment to mitigate performance impacts from Fe-contamination common in non-purified alkaline electrochemical studies.4 We show that the rate of change of alcohol oxidation current density (mA cm-2) depends on reaction pathway (redox vs. potential dependent), alcohol concentration, and side chain structure. Using EC-MS and NMR, we also probe changes in performance in yield and selectivity by quantifying oxidation products, including oxygen gas. These changes in performance are correlated to material changes through monitoring dissolution with on-line ICP-MS. Furthermore, to disentangle the role of potential and reactant (e.g. alcohol or water) on stability, we elucidate oxidation state and local structural changes using in situ X-ray Absorption Spectroscopy (XAS). Insights from this rigorous model system are directly translatable to the broader goal of developing efficient, long-lasting catalysts for industrial deployment of electrochemical organic reactions powered by clean energy. References. Verma, Sumit, Shawn Lu, and Paul JA Kenis. Nature Energy 4.6 (2019): 466-474.2.Bender, Michael T., and Kyoung‐Shin Choi. ChemSusChem 15.13 (2022): e202200675.Klaus, Shannon, et al. The Journal of Physical Chemistry C 119.13 (2015): 7243-7254Wei, Lingze, et al. ACS Catalysis 13.7 (2023): 4272-4282.

Nitrogen-Tungsten Oxide Nanostructures on Nickel Foam as High Efficient Electrocatalysts for Benzyl Alcohol Oxidation.

Electrocatalytic alcohol oxidation (EAO) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts is a major challenge. Herein, we developed a nitrogen-doped bimetallic oxide electrocatalyst (WO-N/NF) by a one-step hydrothermal method for the selective electrooxidation of benzyl alcohol to benzoic acid in alkaline electrolytes. The WO-N/NF electrode features block-shaped particles on a rough, inhomogeneous surface with cracks and lumpy nodules, increasing active sites and enhancing electrolyte diffusion. The electrode demonstrates exceptional activity, stability, and selectivity, achieving efficient benzoic acid production while reducing the electrolysis voltage. A low onset potential of 1.38 V (vs. RHE) is achieved to reach a current density of 100 mA cm-2 in 1.0 M KOH electrolyte with only 0.2 mmol of metal precursors, which is 396 mV lower than that of water oxidation. The analysis reveals a yield, conversion, and selectivity of 98.41%, 99.66%, and 99.74%, respectively, with a Faradaic efficiency of 98.77%. This work provides insight into the rational design of a highly active and selective catalyst for electrocatalytic alcohol oxidation.

High-Efficiency Photocatalytic Oxidation of Benzyl Alcohol by NH2-UiO-66-(Indole-2,3-Dione)-Fe.

The photocatalytic oxidation of biomass-derived benzyl alcohol provides a promising way for the synthesis of benzoic acid, which is an important intermediate with wide applications. To improve the efficiency of photocatalytic benzyl alcohol oxidation to benzoic acid is of great interest. In this work, we propose the utilization of NH2-UiO-66-ID-Fe catalyst for photocatalytic oxidation of benzyl alcohol to benzoic acid, where NH2-UiO-66 is a typically used metal-organic framework, ID is indole-2,3-dione (ID) that has biocompatibility, light absorption property and can be covalently combined with amino-functionalized substances. The NH2-UiO-66-ID-Fe catalyst exhibits improved light absorption and photo-generated electron-hole separation ability compared with NH2-UiO-66. The photocatalytic performance of NH2-UiO-66-ID-Fe was examined for the oxidation of bio-based benzyl alcohol under mild conditions of air atmosphere, room temperature and no additive or additional oxidant involved. The results show that the conversion of benzyl alcohol and the selectivity to benzoic acid could both reach over 99 % in 6 h, and the generation rate of benzoic acid per gram of catalyst is 3.36 mmol g-1 h-1. The reaction mechanism was detected by radical trapping method and in situ electron paramagnetic resonance. This study presents an efficient and environmentally benign avenue for the synthesis of carboxylic acid compounds.

La(FeCuMnMgTi)O3 High-Entropy Oxide Nanoparticles as Highly Efficient Catalysts for Solvent-Free Aerobic Oxidation of Benzyl Alcohol.

In this work, a solid-state method for the synthesis of perovskite La(FeCuMnMgTi)O3 high-entropy oxide (HEO) nanoparticles is detailed. Additionally, the high performance of these nanoparticles as catalysts in the aerobic and solvent-free oxidation of benzyl alcohol is demonstrated. The structural features of HEO nanoparticles are studied by X-ray diffraction and high-resolution transmission electron microscopy. The La(FeCuMnMgTi)O3 nanoparticles demonstrate excellent benzyl alcohol conversion rates and selectivity for benzaldehyde, reaching 10.6% conversion and 52.8% selectivity after reaction for only 4 h and ≤75.6% conversion after 24 h. In addition, the as-prepared HEO catalyst displays robust stability in benzyl alcohol oxidation. Density functional theory calculations demonstrate that the adsorption energy of benzaldehyde on the HEO surface is lower than that of the benzoic acid. This, in turn, hinders the gradual conversion of benzaldehyde to benzoic acid on the surface of HEO and retains benzaldehyde as the main product.

Solvothermal synthesis of PdCu nanorings with high catalytic performance for alcohol electrooxidation

Two-dimensional (2D) Pd-based nanostructures with a high active surface area and a large number of active sites are commonly used in alcohol oxidation research, whereas the less explored ring structure made of nanosheets with large pores is of interest. In this study, we detail the fabrication of PdCu nanorings (NRs) featuring hollow interiors and low coordinated sites using a straightforward solvothermal approach. Due to increased exposure of active sites and the synergistic effects of bimetallics, the PdCu NRs exhibited superior catalytic performance in both the ethanol oxidation reaction (EOR) and the ethylene glycol oxidation reaction (EGOR). The mass activities of PdCu NRs for EOR and EGOR were measured at 7.05 A/mg and 8.12 A/mg, respectively, surpassing those of commercial Pd/C. Furthermore, the PdCu NRs demonstrated enhanced catalytic stability, maintaining higher mass activity levels compared to other catalysts during stability testing. This research offers valuable insights for the development of efficient catalysts for alcohol oxidation.

A broad-spectrum oxidation capability Ru-CeO2 catalyst for efficient synergistic selective oxidation of benzyl alcohol

Selective oxidation of alcohols to aldehydes by molecular oxygen is one of the most important transformations in multiphase catalysis. In this paper, a catalyst with selective oxidation ability was designed and synthesized for the selective catalytic oxidation of benzyl alcohol. N-doped carbon materials were prepared by high-temperature calcination using hydrothermal reaction products of citric acid and melamine as a carbon source, and a bimetallic catalyst supported by Ru-CeO2 was constructed using the mixture as the carrier for the selective oxidation of benzyl alcohol to benzaldehyde. The results showed that the introduction of CeO2 could effectively improve the oxidizing ability and catalytic activity of the catalyst. The Ru-Ce0.05/NC170–600 catalyst was able to convert 85.5 % benzyl alcohol into benzaldehyde at 140 °C, 6 h, and 2 MPa, and the selectivity for benzaldehyde was 100 %. It was demonstrated by DFT that it was theoretically feasible to generate benzaldehyde by extracting hydrogen atoms from benzyl alcohol molecules. Further, the selective oxidation experiments on other alcohols showed that the catalyst has high activity for the oxidation of various alcohols to generate the corresponding carbonyl products, and it is a catalyst with broad-spectrum selective oxidation ability. In this study, a green synthesis route of benzaldehyde was proposed to solve the problems in the traditional process. Meanwhile, it provides a new idea for the synthesis of carbonyl products by selective oxidation of alcohols.

Solvent‐Free Oxidation of Benzyl Alcohol Using Modified Zeolitic Imidazolate Frameworks‐8 (ZIF‐8) Catalysts

AbstractSelective oxidation of alcohols towards carbonyl‐based products, such as aldehydes, is a subject of significant interest in the field of catalysis. Herein, a Zn‐based MOF with 2‐methylimidazolate linker (ZIF‐8) is modified and introduced as catalysts in a selective oxidation of alcohol with benzyl alcohol as the model of the reaction. Modification of ZIF‐8 includes the inclusion of Co(II), Cu(II) or Ni(II) ions as partial replacements for the original Zn(II) metal ions during the synthesis process. The resulting modified ZIF‐8 displays similar PXRD patterns to that of ZIF‐8, indicating no alteration of structures after the introduction of Co(II), Cu(II) or Ni(II) ions. However, the addition of Co(II) was found to modify the resulting ZIF‐8 composition to a higher extent compared to that of Cu(II) and Ni(II) ions. The catalytic test of benzyl alcohol oxidation was performed in a solvent‐free condition with TBHP as the oxidant. Reaction optimization includes reaction temperature, mass of catalysts, TBHP concentration, and reaction time. Among all the catalysts employed in the oxidation of benzyl alcohol, Co(II)‐ and Cu(II)‐modified ZIF‐8 show the highest catalytic activity with 64 % and 62 % conversion, respectively. Furthermore, the catalyst leaching and recyclability tests show that the reactions proceed in heterogeneous systems.

Dehydrogenation of primary alcohols to carboxylic acids in water catalyzed by PNHN-manganese(I) carbonyl complexes

Three classes of manganese(I) complex cation, [(PNHN)Mn(CO)3]Br (Mn1), [(SNHN)Mn(CO)3]Br (Mn2) and [(NRNHN)Mn(CO)3]Br (Mn3 (NMe), Mn4 (NEt), Mn5 (NiPr)), all incorporating a chelating 5,6,7,8-tetrahydro-8-quinolinamine (NHN) but distinct in their third donor atom, have been assessed as catalysts for the dehydrogenative oxidation of primary alcohols to form their corresponding carboxylic acids. Using water as solvent and NaOH as base, PNHN-containing Mn1 proved the most effective allowing both aromatic and aliphatic alcohols to be converted at 160 °C with excellent functional group tolerance (25 examples disclosed). A possible mechanism for this process, that makes use of an acceptorless dehydrogenation pathway, has been proposed and supported by targeted experimentation. Overall, these catalysts show great promise for applications in atom-economic carboxylic acid synthesis as well as in the development of organic hydride-based hydrogen storage systems.

Immobilized transition metal (II) bis–imine chelate on ZnO@TiO2 nanoparticles as sufficient catalysts for alcohol oxidation and for α,β‐cinnamic acid decarboxylative bromination

Based on the strong coordination ability of substituted imines towards transition metals of different oxidation states, the coordination of the HL imine ligand with the Cu2+ ion to form the Cu–bis–imine complex was achieved in 2:1 molar ratios. Their structures were confirmed with various spectroscopic tools. Heterogeneously, CuL2 was successfully appended on ZnO@TiO2 nanoparticles, as the less harmful materials, within the deprotonated p‐hydroxy chain of the bonded ligand in CuL2. The surface and internal structural morphologies of ZnO@TiO2@CuL2 were analyzed using X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), high‐resolution transmission electron microscopy (HRTEM), energy‐dispersive X‐ray spectroscopy (EDS), and infrared (IR) spectroscopy, in addition to thermogravimetric analysis (TGA). The catalytic behavior of both catalysts, CuL2 (the homogeneous catalyst) and ZnO@TiO2@CuL2 (the heterogeneous catalyst), was examined in the benzyl alcohol redox protocols using H2O2 for their optimization. α,β‐Cinnamic acid decarboxylative bromination in the presence of potassium bromide and H2O2 in water was studied with both catalysts, in which (2‐bromovinyl)benzene was the chemoselective product. Both Cu catalysts displayed appreciable catalytic effectiveness for the oxidation protocols and the decarboxylative bromination reactions. CuL2 recorded less required time for optimization than that of the heterogeneous catalyst. The catalytic effectiveness of CuL2 was less promoted than that of ZnO@TiO2@CuL2. Despite the less performance in yield of benzaldehyde for the oxidation protocols with ZnO@TiO2@CuL2, ZnO@TiO2@CuL2 had more recycling than its homogeneous counterpart, with seven to three times, respectively.

Understanding contributions of zeolite surface hydroxyl groups over Au/USY in selective oxidation of aromatic alcohols

Metal-zeolites catalysts are of great importance in selective organic conversions. Zeolites possess features of highly-ordered porous network, adjustable acidic properties (Brønsted/Lewis), spatial nanoconfinement effects, unique shape selectivity and the strong (hydrothermal-) stability. The role of zeolite hydroxyl (z-OH) groups, such as bridging ones in Si-O(H)-Al (B acids) and terminal ones in Al-OH and Si-OH (silanols), in catalysis is an interesting topic, particularly when they are not catalytic active sites, while they affect the catalytic performances. This study comprehensively investigated series of Au/USY catalysts in the selective oxidation of benzyl alcohol to benzaldehyde and clarified the dominating contributions of Al-associated z-OH groups to affecting catalytic conversions and selectivity via altering the Si/Al ratio and reducing z-OH groups by amorphous silica species derived from diethoxydimethylsilane under high-temperature calcination. The catalysts were characterized by XRD, BET, TEM, XPS, UV/Vis, FT-IR and in-situ DRIFT to investigate crystal structures, textural properties, morphologies, size distribution, chemical state of gold, acidity, and adsorptive properties. The experimental results proved that zeolites with a higher amount of z-OH groups tuned by Si/Al ratios or by diethoxydimethylsilane silylation exhibited higher catalytic activity because of the adsorption effect. Finally, a possible mechanism was discussed based on the experimental results and literature.

Nitridated Nickel Mesh as Industrial Water and Alcohol Oxidation Catalyst: Reconstruction and Iron‐Incorporation Matters

AbstractNickel mesh (NM) is used in industrial alkaline water electrolyzers due to its cost‐effectiveness and conductivity. However, the decisive factors that advance the efficiency and sustainability of such electrodes are only partially understood. Herein, an efficient NM‐based electrocatalyst for the oxygen evolution reaction is developed via a single‐step nitridation route on a commercially used NM substrate and sheds light on the role of reconstruction and iron content to boost catalyst performance and durability. Remarkably, the activated Ni3N/NM catalyst required an overpotential of 0.46 V to deliver 1 A cm−2 in ambient conditions (1 M KOH, 25 °C). This overpotential decreases substantially to 0.28 V in industrially relevant conditions (6 M KOH, 85 °C) and is maintained for 235 h. Ni3N/NM partially transformed into NiFe layered (oxy)hydroxide in both conditions, while the active structure's Fe content is reconstruction condition dependent (temperature and KOH concentration). Electrodes reconstructed under industrially relevant conditions performed better than ambient reconstructed ones due to a more pronounced iron‐incorporation from KOH and the evolution of porous morphologies. In industrial environments, activated Ni3N/NM excels in selectively converting benzyl alcohol to benzoic acid, achieving an impressive yield of 96%.

Dihalosalicylaldehyde based molybdenum(VI) complexes: Synthesis, spectral characterization, crystal structures, and catalytic activities for the selective oxidation of benzylic alcohols

Three ONO donor Schiff base ligands were obtained by the condensation of 3,5-dihalosalicylaldehydes with nicotinoylhydrazide (H2Cl2SN: (E)-N'-(3,5-dichlorosalicylaldehyde) nicotinoylhydrazone, H2Br2SN: (E)-N'-(3,5-dibromosalicylaldehyde) nicotinoylhydrazone, and H2I2SN: (E)-N'-(3,5-diiodosalicylaldehyde) nicotinoylhydrazone on refluxing in ethanol. The treatment of [MoO2(acac)2] (acac = acetylacetonato) with these ligands in methanol afforded cis-dioxidomolybdenum(VI) complexes [MoO2(Cl2SN)(CH3OH)] (1), [MoO2(Br2SN)(CH3OH)] (2), and [MoO2(I2SN)(CH3OH)] (3). Various techniques like NMR (1H and 13C), FT-IR, Mass, TGA, elemental (CHN), and single-crystal X-ray diffraction analysis (for H2Cl2SN·H2O, 2a, [MoO2(Br2SN)(C2H5OH)], and 3a, [MoO2(I2SN)(H2O)].DMF) were utilized to characterize the synthesized compounds. The data collected from diffraction studies revealed that the geometry around Mo(VI) ions was distorted octahedral. Additionally, all complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide.