Selective Oxidation Of Benzyl Alcohol Research Articles

Selective oxidation of benzyl alcohol to benzaldehyde using sustainable catalysts: An overview

Selective oxidation of benzyl alcohol to benzaldehyde using sustainable catalysts: An overview

Selective oxidation of benzyl alcohols photocatalyzed by asymmetric cobalt thioporphyrazine supported on alumina

The sunlight-powered transformation of alcohols to corresponding carboxylic acids offers a feasible route for fine chemical synthesis. In this work, the asymmetric cobalt tri(2,3-bis(butylthio)maleonitrile)-(1,4-dithiin) porphyrazine (CoPz(SBu)6(dtn)) was synthesized, more importantly, its single crystal was further obtained by the solvent evaporation method. Then the asymmetric CoPz(SBu)6(dtn) supported on neutral Al2O3 particles to form composite photocatalyst CoPz(SBu)6(dtn)@Al2O3, which possessed strong visible light absorption. Under simulated sunlight irradiation using a xenon lamp, the composite photocatalyst CoPz(SBu)6(dtn)@Al2O3 exhibited excellent photocatalytic activity for selective oxidation of benzyl alcohol to benzoic acid in water under conditions of green H2O2 as oxidant and K2CO3 as additive. The conversion of benzyl alcohol was up to 53.8 % together with 99 % selectivity of benzoic acid over composite photocatalyst CoPz(SBu)6(dtn)@Al2O3. Meanwhile, this photocatalytic system had feasible substrate generalizability and excellent photocatalytic activity for substituted benzyl alcohols containing both electron-donating and electron-withdrawing substituents. The composite photocatalyst CoPz(SBu)6(dtn)@Al2O3 exhibited excellent photocatalytic durability, which was confirmed by the recycling experiments. This work manifests the asymmetric thioporphyrazine as photocatalyst is feasible in implementing sunlight-powered selective transformation.

Terpyridine Ni(II) Complex Grafted CdS Nanorods for Cooperative Selective Benzyl Alcohol Oxidation and Hydrogen Production.

Efficient utilization of photogenerated charge carriers to realize photocatalytic solar fuel production and oxidative chemical synthesis is a challenging task. Herein, a conventional amidation reaction route is adopted to successfully construct a novel composite photocatalyst composed of a Ni(II)-terpyridine complex with carboxyl groups grafted on CdS nanorods (labeled as CdS@Ni(terpyC)2). Experimental results have unequivocally revealed that the as-fabricated composite catalyst exhibited a remarkable enhancement in photocatalytic activity for the dehydrogenation of benzyl alcohol under visible light, demonstrating superior hydrogen evolution efficiency and benzaldehyde selectivity, surpassing both pristine CdS and the blend of CdS and Ni(terpyC)2. The carrier dynamics study demonstrated that the Ni(terpyC)2 on the surface of CdS could quickly extract the photogenerated electrons of CdS, which reduced the carrier recombination efficiency, further improving the photocatalytic activity of the catalyst. This work illustrates the effect of surface active site engineering on photocatalysis and is expected to shed substantial inspiration on future surface modulation and design of semiconductor photocatalysts.

Design of TiO2-X nanotubes with controllable oxygen vacancy concentration and performance study of selective oxidation of benzyl alcohol

Design of TiO2-X nanotubes with controllable oxygen vacancy concentration and performance study of selective oxidation of benzyl alcohol

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.

Gold supported on Bi2MoO6 based on oxygen vacancy structure: Enhanced adsorption activation for efficient photocatalytic selective oxidation of benzyl alcohol

In this work, ethylene glycol was used as a mild reducing agent to prepare Bi2MoO6 support with oxygen vacancies. By introducing Au active species, an Au/BMO-Ov (Bi2MoO6 support with oxygen vacancies) photocatalyst was synthesized, which was co-modified with oxygen vacancies and Au NPs (nanoparticles), and significantly improved the capability of Bi2MoO6 for visible light-driven BA (benzyl alcohol) conversion. The 1 wt% Au/BMO-Ov exhibited the highest conversion (98.8 %) of BA and excellent selectivity (97.4 %) of BAD (benzaldehyde) under visible light. Oxygen vacancies have an inhibitory effect on the recombination of photogenerated carriers. Au NPs acted as both photosensitizers (LSPR effect captures light and generates electrons and holes) and active species (used as Lewis acids). The results of photoelectrochemistry (PEC) tests confirmed that the synergistic interaction of Au and oxygen vacancies enhanced the photoactivity of bismuth molybdate. Meanwhile, density functional theory (DFT) calculations indicated that oxygen vacancies and Au synergistically reduced the bandgap energy of Bi2MoO6 and enhanced the adsorption of BA. Au served as the Lewis acid site for adsorption of BA, and improved the reactivity of light-driven BA conversion. The corresponding mechanism was proposed based on the experimental results and DFT calculations.

Rational design of nitrogen and carbon co-decorated mesoporous TiO2 composites for photocatalytic selective oxidation of alcohols

Photocatalytic organic synthesis has attracted much attention in recent years. Herein, a N and C co-decorated mesoporous TiO2 (mp-NCT) photocatalyst was synthesized for selective oxidation of alcohols. Notably, the as-prepared mp-NCT composites possess large specific surface areas and mesoporous structures, which could provide sufficient active sites and improve mass transfer. Furthermore, the co-doping of N and C species could not only extend the light absorption, but also tune the valence band of TiO2. Meanwhile, numerous oxygen vacancies and intra-band could be introduced, which helps to reduce the combination of the photogenerated carriers. As a result, the mp-NCT composites show excellent photocatalytic performance towards selective oxidation of benzyl alcohol and its derivatives to corresponding aldehydes under simulated sunlight irradiation. Mechanism studies revealed that the photogenerated electrons, holes and high dynamic equilibrium concentration of O2•- radicals were responsible for the efficient conversion of alcohols to aldehydes.

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.

Synergistic coupling of photocatalytic H2 evolution and selective oxidation of benzyl alcohol over ZnIn2S4/Ni in aqueous solution

The synergistic coupling of photocatalytic hydrogen evolution and selective organic matter conversion is extremely attractive, as clean fuel and high value–added chemicals can be produced simultaneously with light as the sole energy input. Herein, we developed a dual functional photocatalyst (ZnIn2S4/Ni) for efficient photocatalytic conversion of benzyl alcohol into benzaldehyde with simultaneous hydrogen production. Consequently, ZnIn2S4/Ni displayed a top-level benzaldehyde and H2 evolution rate even in aqueous media. The yield of benzaldehyde reaches 19.3 mmol/g/h, which is 33 times higher than that of naked ZnIn2S4 and even exceeds that of precious metal systems (Pt, Pd, Ru). Here, Ni site not only acted as an effective co–catalyst for charge separation, but also played an important role in accelerating the α–C–H bond cleavage during the dehydrogenation of benzyl alcohol. This work provides a cost-effective and green reference path for the efficient conversion of solar energy to chemical energy.

Interfacial interactions of polyoxometalate and Au0Pdδ+ alloy boosting aerobic oxidation of alcohols

It is significant to gain insights into the electronic interfacial interactions on non-reducible oxides as they can effectively improve the catalytic performance. Herein, we reported the fabrication of Au0Pdδ+ alloy (average size: 1.9 nm) co-modified with Na12[α-P2W15O56] (P2W15) nanoclusters on aluminum oxide (denoted as AuPd/P2W15-Al2O3) by deposition–precipitation and covalent immobilization strategy. The as-prepared AuPd/P2W15-Al2O3 exhibited 92 % conversion, 96 % selectivity of benzaldehyde with the reaction rate of 4.9 × 104h−1 when applied for the selective oxidation of benzyl alcohol, which was superior to AuPd/Al2O3, Au/P2W15-Al2O3 and Pd/P2W15-Al2O3 catalysts. Such excellent catalytic performance can be ascribed to the fact that: the electrons transfer from P2W15 to Au0Pdδ+ alloy resulted in the electron-rich Au0Pdδ+ alloy species, and the enhanced interfacial interactions between Au0Pdδ+ alloy and P2W15 nanoclusters facilitated activation of O2 to generate superoxide radicals •O2–. Moreover, density-functional theory (DFT) calculation confirmed that the P2W15 clusters modulated the d-band center of Au0Pdδ+ alloy and accelerated the adsorption of benzyl alcohol, O2 activation and desorption of benzaldehyde.

Photocatalytic hydrogen production coupled with selective benzyl alcohol oxidation via WOx/CdS S-scheme heterojunction

Photocatalytic hydrogen production coupled with high value-added organic conversion is a mild and effective way to obtain green energy and fine chemicals simultaneously. In this work, a CdS-based S-scheme photocatalyst is designed for efficient hydrogen production and highly selective conversion of benzyl alcohol in aqueous solution. With further assistant of Ni co-catalyst, the hydrogen production rate of WOx/CdS S-scheme photocatalyst can reach ∼131 μmol h−1, and benzyl alcohol has ∼91% conversion with selectivity of the target product benzaldehyde ∼100 %. The quality photocatalytic activity is inclined towards the construction of S-scheme heterojunction composing of WOx and CdS can ensure the redox ability while reducing the recombination of photogenerated carries. Meanwhile, reactive species involved in benzyl alcohol oxidation were confirmed by radical capture experiments, the excellent conversion and selectivity could not be achieved without the significant contribution of photogenerated holes.

Design and fabrication of Zr-based MOF photocatalyst with functionalized moieties for CO2 reduction and coupling selective oxidation of benzyl alcohol

Zirconium-based metal organic frameworks (Zr-MOFs) are considered as promising photocatalysts due to their excellent stability, unique pore structure, and versatile photocatalytic applications. To strengthen the visible-light absorption, a well-designed targeted MOFs photocatalyst was fabricated by a solvothermal method with Co-tetrakis (4-carboxyphenyl) porphyrinate (Co-TCPP), 1,3,6,8-tetra(4-carboxyphenyl) pyrene (TBAPy), and Zr clusters as sensitizer, ligands and active sites, respectively. Benefiting from the excellent photo-responsiveness of Co-TCPP, the robust catalytic ability of Zr clusters, the promising electron transfer ability of pyrene moiety, the prepared Zr-Co MOF@TBAPy exhibit excellent photocatalytic performance and stability. A high reduction rate of 127.42 μmol g−1 h−1 from CO2 to CO, this is 3.5 and 2.8 times that of Zr-TBAPy and Zr-Co MOF, respectively. The photocatalytic performance of CO2 reduction coupling with selective oxidation of benzyl alcohol (BA) to benzaldehyde (BD) was also tested. The transferring pathway of photogenerated electron from the photosensitive unit to the active site mediated by the electron transport unit was further confirmed by density-functional theory (DFT) calculations, providing intuitive insights into the catalytic mechanism. This work manifests that well-designed MOFs integrated with functional moieties is a feasible strategy for developing high performance MOF based photocatalyst.

Unprecedented stepwise electron transfer and photocatalysis in supramolecular assembly derived hybrid single-layer two-dimensional nanosheets in water

Herein, a simple and effective outer-surface interactions assisted supramolecular hierarchical assembly has been first exploited to uniformly distribute tungstosilicic acid (TSA) inside the porous structure of cucurbit[10]uril-based single-layer 2D supramolecular-organic-frameworks (Q[10]-SOFs) in water. Importantly, the 2D Q[10]-SOFs can further serve as light harvesting antenna, achieving fast energy transfer to the embedded redox-active TSA upon photoexcitation, resulting in efficient visible light-driven selective oxidation of benzyl alcohols into the corresponding aldehydes in high yield at room temperature. Further studies revealed that the integrated of 2D Q[10]-SOFs and TSA played a key role in the catalytic process, due to the presence of a novel stepwise electron transfer route in the single-layer hybrid 2D structures.

Impact of Ceria Support Morphology on Au Single‐Atom Catalysts for Benzyl Alcohol Selective Oxidation

AbstractAlcohol oxidations are a key industrial chemical transformation, with aldehydes and ketones finding use in an array of applications. Nobel metals are known for their activity towards this chemoselective transformation, however, sustainable catalyst synthesis requires optimal utilisation of these scarce elements. Here, we report Au catalytic systems based on the deposition of isolated Au sites on different morphologies of ceria in which different surface facets of the support are exposed. Through tailoring the support morphology and from extensive catalyst characterisation, it is shown that the exposed facet is critical for controlling the formation (or not) of isolated Au sites. Both the 110 and 111 facets are capable of this feat, yielding single‐atom sites for rod, octahedron, and polyhedron morphologies. In contrast, the 100 facet is not, resulting in Au nanoparticles on cubic ceria. This dictation over Au species is critical to benzyl alcohol oxidation capacity at mild conditions and in the absence of a soluble base, with only single‐atom catalyst (SAC) systems demonstrating activity. Furthermore, the exposed surface facet also governs the degree of surface oxygen vacancies, which is critical to catalyst activity due to their control over substrate adsorption strength, as revealed through T1/T2 NMR relaxation measurements.

Hollow heterojunction with dual-vacancy engineering to boost photocatalytic performance for photoreduction of CO2 coupled with selective oxidation of benzyl alcohol to benzaldehyde

CO2 photoreduction into chemical fuels is hopeful and sustainable for a carbon–neutral future. Herein, a bifunctional dual-vacancy-modified hollow heterojunction photocatalyst is ingeniously designed for CO2 photoreduction to CO coupling with selective oxidation of benzyl alcohol to benzaldehyde. Synergistic catalysis effect resulted from hollow heterostructures, TiO2 with O vacancies (TiO2-x) and Zn0.3-xCd0.7S with Zn vacancies (ZCS) leads to excellent photoreduction and photoxidation performances. The optimized sample (TiO2-x/ZCS hollow sphere) exhibits highest photocatalytic activity of all the obtained samples. The yields of CO and benzaldehyde are 105 and 323.5 μmol g–1h−1, respectively. The construction of Z-scheme heterojunction realizes the spatial separation of redox reaction sites, and the dual-vacancy distributed on the heterojunction enhance the interfacial reactivity. Additionally, density functional theory calculation and in-situ technology reveal that Zn vacancy in ZCS and O vacancy in TiO2-x function as active sites for the binding and activation of *COOH and *PhCH2O-, respectively, thereby stabilizing the crucial step in the formation of intermediates such as CO and benzaldehyde. This work enhances the utilization of photogenerated carrier, and affords a new opportunity to design hollow heterojunction with dual-vacancy engineering to boost photocatalytic performance for coupling reaction system.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance.

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

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.

A binary dumbbell visible light driven photocatalyst for simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde

Photocatalytic H2 production with selective oxidation of organic moieties in an aqueous medium is a fascinating research area. However, the rational design of photocatalysts and their photocatalytic performance are still inadequate. In this work, we efficiently synthesized the MoS2 tipped CdS nanowires (NWs) photocatalyst using soft templates via the two-step hydrothermal method for efficient H2 production with selective oxidation of benzyl alcohol (BO) under visible light illumination. The optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst exhibits the highest photocatalytic H2 production efficiency of 13.55 mmol g−1 h−1 with 99 % selective oxidation of BO, which was 42.34 and 2.21 times greater photocatalytic performance than that of pristine CdS NWs and MoS2/CdS NWs, respectively. The directional loading of MoS2 at the tips of CdS NWs (as compared to nondirectional MoS2 at CdS NWs) is the key factor towards superior H2 production with 99 % selective oxidation of BO and has an inhibitory effect on the photo corrosion of pristine CdS NWs. Therefore, the amazing enhancement in the photocatalytic performance and selectivity of optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst is due to the spatial separation of their photoexcited charge carriers through the Schottky junction. Moreover, the unique structure of the MoS2 flower at the tip of 1D CdS NWs offers separate active sites for adsorption and surface reactions such as H2 production at the MoS2 flower (confirmed by Pt photo deposition) and subsequently the selective oxidation of BO at the stem of CdS NWs. This rational design of a photocatalyst could be an inspiring work for the further development of an efficient photocatalytic system for H2 production with selective oxidation of BO (a strategy of mashing two potatoes with one fork).

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.

Radical-driven selective oxidation of benzyl alcohol on MnCoOx catalysts with no oxidant other than air in reactor

Mn reinforced Co3O4 catalysts (MnCoOx) were prepared by a facile solid phase mixed foaming method with an in-situ heating enhancement for the formation of spinel phase mixed oxide species, and studied in the selective oxidation of benzyl alcohol just the air in reactor as oxygen donor. It was found that the MnCoOx catalysts are composed of relatively minimal spinel MnCo2O4 mixed oxide and massive Co3O4 to form MnCo2O4-Co3O4 oxide pair. The micro-domains of MnCo2O4-Co3O4 oxide pair present two redox couples of Mn3+/Mn2+ and Co3+/Co2+ instead of the single one of Co3+/Co2+ in Co3O4, and then dramatically enhance the formation of superoxide radicals (•O2–) species from the O2 in air, which can efficiently initiate the conversion of benzyl alcohol to benzaldehyde in a Fenton-like processes. With no oxidant other than air in reactor, the interaction between MnCo2O4 and Co3O4 in MnCoOx catalysts leads to a benzyl alcohol conversion up to 98 % with a 100 % benzaldehyde selectivity at atmospheric pressure while single component Co3O4 can only present a benzyl alcohol conversion at 37 %. This embodiment of highly efficient heterogeneous selective oxidation just with air as oxidant provides a probability for developing a low-cost and super-facile radical-induced selective oxidation process for alcohols.