Photocatalytic Oxidation Of Benzyl Alcohol Research Articles

Boosting multiple photo-assisted and temperature controlled reactions with a single redox-switchable catalyst: Solvents as internal substrates and reducing agent

An alternative and economically viable process for the synthesis of β-aryl enals, enones and the aryl amines has been developed by partial oxidation of ethanol, isopropanol and N, N-dimethyl formamide (DMF). The formation of β-aryl enals, enones and the aryl amines was catalyzed by a mixed metal oxides layer of cobalt and chromium supported on halloysite nanotubes, designated as CoCr2O4-HNT. The CC and CN bond formation reactions were found to be influenced by temperature and the nature of base. The condensation of aldehyde with in situ generated acetaldehyde by ethanol oxidation forming β-aryl enals occurred selectively at 120 °C. The partial oxidation of isopropanol to acetone and its condensation with aldehydes forming β-aryl enones occurred at room temperature. Increase in temperature caused the liberation of hydrogen gas from isopropanol and allowed the reversible reduction of aldehydes to alcohols. Increase in temperature in isopropanol and increase in base concentration in ethanol causes the selective reduction of aldehydes to alcohols. Besides being active for the Claisen-Schmidt type of reactions and the aryl halides amination process, the synthesized catalyst was also found to be highly active for the photocatalytic oxidation of benzyl alcohols in absence of any external oxidizing agent. The positive holes (h+) generated at the Co(II) site as evident from EPR analysis was considered to be responsible for high photocatalytic activity of the material reducing the recombination rate of holes and electrons (e−). Density Functional Theory calculations were performed to understand the mechanism of ethanol oxidation to acetaldehyde.

Selective Photocatalytic Oxidation of Benzyl Alcohol at Ambient Conditions using Spray-Dried g-C3N4/TiO2 Granules

In the 2010-decade, significant progresses have been made in the photocatalytic properties of graphitic-carbon nitride (g-C3N4). In this study, we synthesized and characterized a new photocatalyst, spray-dried g-C3N4/TiO2 granules, through a simple pyrolysis process of urea and TiCl4 as the precursors. The photocatalytic oxidation of benzyl alcohol (BA) to benzaldehyde (BAL) was carried out in a batch reactor in the presence of pure g-C3N4, g-C3N4/TiO2, and spray-dried g-C3N4/TiO2 granules at ambient pressure and under visible light irradiation at different conditions, including reaction time, temperature, and catalyst loading. The results showed that the new photocatalyst, spray-dried g-C3N4/TiO2 granules (TCNg), is much more effective on the photocatalytic oxidation of benzyl alcohol and also possesses high atom efficiency, high yield, and an average turnover frequency (TOF) of over 550 h-1. Finally, the DFTB + method was used to investigate the frontier orbitals and to determine the band gap of TiO2, g-C3N4, and g-C3N4/TiO2.

A novel metal-free photocatalyst polyphenylene sulfide: Synthesis, characterization and performance evaluation

Polarization has emerged as one of the most effective strategies for charge carriers separation in the bulk and on the surface of photocatalysts. Searching for novel photocatalysts with intrinsic polarity is a challenge to promote the progress of photocatalysis. Herein, a novel organic polymeric photocatalyst —— Polyphenylene sulfide (PPS) is introduced. Bearing the noncentrosymmetric structure and alternant arrangement of thioether bonds and benzene groups, the generated intrinsic polarization of PPS is proposed and proved. Compared with graphitic carbon nitride (g-C3N4), PPS exhibits 1.33–5.53 times higher activities for the photodegradation of various contaminants and 50 % more effective performance on the photocatalytic oxidation of benzyl alcohol (BA) to benzaldehyde (BAD) with high selectivity (96 %), which can be ascribed to the spatial separation of charges motivated by the polarization-induced electric field. The investigation of PPS will provide a fresh angle of view for the design and preparation of new metal-free photocatalysts.

Selective solar photocatalytic oxidation of benzyl alcohol to benzaldehyde over monodispersed Cu nanoclusters/TiO2/activated carbon nanocomposite

Great efforts have been made to enhance the efficiency of the solar light-activated photocatalyst in recent years. In this work, monodispersed copper nanoclusters protected by N-acetyl-L-cysteine ligand (Cu@NALC) were synthesized. The optical properties and chemical composition of the synthesized copper clusters were studied by UV-vis and FTIR spectroscopies, and thermogravimetric analysis (TGA), respectively. The charge of copper atoms in Cu@NALC clusters was zero as was confirmed by X-ray photoelectron spectroscopy (XPS). A novel nanocomposite consisting of ∼1 nm copper clusters, Degussa TiO2 P25, and activated carbon (Cu@NALC/TiO2/AC) was prepared to use as a solar light-activated photocatalyst. The synthesized copper clusters showed significantly increase solar light absorption and improved the efficiency of Cu@NALC/TiO2/AC nanocomposite for photocatalytic oxidation of benzyl alcohol (BA), compared with Cu@NALC/AC and TiO2/AC nanocomposites. Cu@NALC clusters induce the TiO2 to absorb the visible light, where the copper nanoclusters absorb visible light from 400-700 nm. The copper clusters mainly adsorb on the surface of TiO2 nanoparticles, as well on the activated carbon surface as shown in HR-TEM analysis. The highly efficient photocatalytic activity of this nanocomposite is attributed also to the large surface area of activated carbon as shown in surface area analysis (692.8 m2/g). Cu@NALC/TiO2/AC nanocomposite achieved 100% conversion of BA with ≥99 % selectivity after 6 h solar irradiation; however Cu@NALC/AC, TiO2/AC and TiO2-P25 showed only 66.35 %, 55.43 % and 44.78 %, respectively. All the components of this nanocomposite are cheap and available, in addition to the high photocatalytic activity, were found to be the most economically and suitable system for the industrial application.

Highly Crystalline Mesoporous Titania Loaded with Monodispersed Gold Nanoparticles: Controllable Metal-Support Interaction in Porous Materials.

We report the syntheses of mesoporous Au/TiO2 hybrid photocatalysts with ordered and crystalline frameworks using co-assembly of organosilane-containing colloidal amphiphile micelles (CAMs) and poly(ethylene oxide)-modified gold nanoparticles (AuNPs) as templates. The assembled CAMs can convert to inorganic silica during calcination at elevated temperatures, providing extraordinary thermal stability to preserve the porosity of TiO2 and the nanostructures of AuNPs. Well-defined AuNPs supported within mesoporous TiO2 (Au@mTiO2) can be prepared using thermal annealing at temperatures up to 800 °C. High-temperature treatment (≥500 °C) under air is found to not only improve the crystallinity of TiO2 but also induce oxidative strong metal-support interactions (SMSIs) at Au/TiO2 interfaces. For oxidative SMSIs, the surface oxidation of AuNPs can generate positively charged Auδ+ species, while TiO2 gets reduced simultaneously. Using photocatalytic oxidation of benzyl alcohol as a model reaction, Au@mTiO2 calcined at 600 °C for 12 h exhibited the best activity under UV irradiation, while Au@mTiO2 calcined at 600 °C for 2 h showed the best activity under visible light. The delicate balance between the crystallinity and porosity of TiO2 and the SMSIs at Au-TiO2 interfaces is found to impact the photocatalytic activity of these hybrid materials.

Selective photocatalytic oxidation of aromatic alcohols to aldehydes with air by magnetic WO3ZnO/Fe3O4. In situ photochemical synthesis of 2-substituted benzimidazoles.

Recently, visible light-driven organic photochemical synthesis has been a pioneering field of interest from academic and industrial associations due to its unique features of green and sustainable chemistry. Herein, WO3ZnO/Fe3O4 was synthesized, characterized, and used as an efficient magnetic photocatalyst in the preparation of a range of 2-substituted benzimidazoles via the condensation of benzyl alcohol and o-phenylenediamine in ethanol at room temperature for the first time. The key feature of this work is focused on the in situ photocatalytic oxidation of benzyl alcohols to benzaldehydes under atmospheric air and in the absence of any further oxidant. This new heterogeneous nanophotocatalyst was characterized via XRD, FT-IR, VSM and SEM. Short reaction time, cost-effectiveness, broad substrate scope, easy work-up by an external magnet, and excellent product yield are the major advantages of the present methodology. A number of effective experimental parameters were also fully investigated to clear broadness and generality of the protocol.

Nano-WO3 -SO3 H as a New Photocatalyst Insight Through Covalently Grafted Brønsted Acid: Highly Efficient Selective Oxidation of Benzyl Alcohols to Aldehydes.

Modification of nano-WO3 with -SO3 H groups as a covalently grafted solid acid reduced its band-gap energy from 2.8 to 2.4eV and made it an ideal nominee for photocatalytic reaction under visible light irradiation. This nano-photocatalyst has been successfully used for the selective oxidation of different benzyl alcohols to corresponding aldehydes under blue LED irradiation. The reaction became approximately two times faster with excellent yields. It has shown that the nitrobenzene as an available industrial oxidant is applicable for photocatalytic oxidation of benzyl alcohol; remarkably high yield and selectivity have been observed.

Heptazine-based porous polymer for selective CO2 sorption and visible light photocatalytic oxidation of benzyl alcohol

Heptazine units with highly rich nitrogen sites were employed to fabricate a new porous organic polymer (POP-HE) via direct coupling of 2,5,8-trichloro-s-heptazine and 4,4′,4″,4‴-(ethene-1,1,2,2-tetrayl)tetraaniline with the mild base N, N′-diisopropylethylamine (DIPEA) in tetrahydrofuran (THF) solution. POP-HE displays good CO2 uptake capacity (50.6 cm3 g−1, 10 wt%, 1 bar/273 K) and highly selectively adsorptive separation of CO2 over CH4 under ambient conditions. Impressively, at 273 K, the predicted IAST selectivity of POP-HE is 47.0-13.4 for the natural gas mixture (CO2/CH4 = 5:95) at pressures varying from 0 to 1 atm. Meanwhile, the result of calculated band gap value based on Tauc plot motivated us to investigate its photocatalytic activity. POP-HE was applied as heterogeneous photocatalyst for visible light-induced selective oxidation of benzyl alcohol to benzaldehyde, and exhibited great conversion of 33.6% under irradiation of white LED light, which is much higher than that of g-C3N4. Moreover, POP-HE can be recycled up to three times without significant decrease in catalytic activity.

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.

Enhancement of the visible-light photocatalytic activity of CeO2 by chemisorbed oxygen in the selective oxidation of benzyl alcohol

Enriched chemisorbed oxygen on CeO2 significantly improved the activity of photocatalytic oxidation of benzyl alcohol under visible light.

Visible-light-initiated one-pot clean synthesis of nitrone from nitrobenzene and benzyl alcohol over CdS photocatalyst

The controlled visible-light mediated conversion of nitroaromatics to versatile nitrogen-containing intermediates is of great significance but still remains a challenge. Herein, we report for the first time a facile visible-light-initiated one-pot strategy for clean and efficient synthesis of nitrone from nitrobenzene and benzyl alcohol. It integrates the controlled photocatalytic reduction of nitrobenzene to phenylhydroxylamine by photogenerated electrons with the selective photocatalytic oxidation of benzyl alcohol to benzaldehyde by photoinduced holes over a low-cost CdS photocatalyst with a suitable reduction capability, followed by spontaneous condensation of the as-formed hydroxylamine and aldehyde at ambient pressure and room temperature. Furthermore, by modulating cocatalyst and illumination time, for the conversion of the same reactants, the other two useful nitrogen-containing compounds, imine and secondary amine, were also successfully synthesized. The reaction mechanisms for flexible synthesis of the three target products are proposed.

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.

Selective Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde or C–C Coupled Products by Visible-Light-Absorbing Quantum Dots

This Forum Article describes the photocatalytic oxidation of benzyl alcohol by visible-light-absorbing colloidal CdS quantum dots (QDs), with 99% selectivity for benzaldehyde or 91% selectivity for...

Template-free synthesis of hollow TiO2 nanospheres supported Pt for selective photocatalytic oxidation of benzyl alcohol to benzaldehyde

Heterogeneous photocatalytic system are widely applied to degrade organic pollutants or converse into high value-added chemicals. Both environmental and energy aspects should be considered to improve these chemical processes, favoring reaction conditions that involve room temperature and ambient O2 pressure. In the present work, hollow titanium dioxide nanospheres were fabricated via template-free method. The prepared samples were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation of benzyl alcohol to benzaldehyde with visible light under atmospheric pressure at room temperature. The designed hollow structure (2%Pt–TiO2–5) not only exhibited a very high surface area, but also promoted photonic behavior and multiple light scattering, which as an efficient photocatalyst performed moderate conversion (about 20%) and high selectivity (> 99%) for oxidation of benzyl alcohol to benzaldehyde at room temperature with visible light in solvent of toluene. This work suggests that both hollow structure and Pt nanoparticles have great potential for execution of oxidative transformations under visible light.

Nickel-Doped Excess Oxygen Defect Titanium Dioxide for Efficient Selective Photocatalytic Oxidation of Benzyl Alcohol

In this study, a novel composite Ni-OTiO2 was prepared by doping nickel and introducing excess oxygen defects in TiO2. The as-synthesized Ni-OTiO2 particles were characterized by scanning electron ...

Facile preparation of mixed-phase CdS and its enhanced photocatalytic selective oxidation of benzyl alcohol under visible light irradiation

Selective oxidation is one green technique for routine organics synthesis and environmental remediation. However, the conversion ratio resulted from environment-friendly method employing traditional photocatalytic materials like CdS is relatively low as compared with homogeneous catalytic reaction. Herein, in this paper, a facile method is reported to prepare mixed-phase CdS nanocrystals at room temperature. The as-prepared CdS samples were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic oxidation of benzyl alcohol into benzaldehyde catalyzed by as-prepared CdS was carried out with high conversion of 68% generated within 60 min using O2 as a benign oxidant under ambient condition. The enhanced catalytic activity could be attributed to the mixed-phased crystal structure which facilitates the separation of photogenerated charge carriers.

Versatility in the catalytic and photocatalytic reactions of composites based on Zr- and Zr-Pd-doped titania nanoparticles

A series of Zr-doped titanium oxide-based nanomaterials with different amounts of Zr (1%, 2% and 5%) have been prepared by a simple method based on sol-gel procedures. The materials have been calcined at different temperatures (400, 500 or 600 °C). The calcined materials have been characterised by different methods and the structural features compared and analysed in detail. In general, the incorporation of different quantities of Zr lead to changes in the structural features in terms of morphology, particle size and crystallinity of the sample. The Zr-doped titanium oxide nanomaterials were studied in the photodegradation of a model of organic pollutant such as methylene blue. The results show differences in the photocatalytic activity of the materials with different quantities of Zr and the calcination temperature. In view of the interesting results of photodegradation, the Zr-doped materials were also tested in the oxidation and photooxidation of benzyl alcohol to benzaldehyde. Furthermore, the nanomaterials which showed better catalytic properties were also doped with Pd nanoparticles, which were prepared in situ by reduction of a Pd salt. All the Pd-Zr-doped systems present significant physico-chemical differences with the analogous materials without Pd (changes in the band gap, surface area, crystallite size, and structural agglomeration). The Pd-doped systems were tested in C-C coupling reactions, catalytic and photocatalytic oxidation of benzyl alcohol and photodegradation of methylene blue at different pH values, showing an interesting catalytic and photocatalytic versatility which may be exploited in the future to other catalytic green processes.

Selective aerobic photocatalytic oxidation of benzyl alcohol over spherical structured WO3/TiO2 nanocomposite under visible light irradiation

TiO2/WO3 nanocomposite with nanodisk morphology was prepared and successfully used as a photocatalyst. The nanocomposite was obtained via sonochemical and hydrothermal methods, using pomegranate juice as a capping agent. The products were characterized by FE-SEM imaging, BET, EDAX spectroscopy, X-ray diffraction, DRS, and FT-IR spectroscopy. TiO2/WO3 nanocomposite showed high sensitivity to absorb visible light in compared to TiO2. In an optimized condition, the yield of the aerobic photocatalytic oxidation of benzyl alcohol derivatives reached to 65% for the TiO2/WO3 nanocomposite, while the conversion percent of the derivatives was less than 8% and 50% on the TiO2 and WO3 nanoparticles, respectively. Experimental results were supported by density functional theory (DFT) calculations. The DFT results in several solvents of different dielectric constants, confirmed the strong dependence of light absorption and photocatalytic activity to adsorption energy of the substrates on the surface of the nanoparticles (Ead). In addition, the theoretical results showed an inverse correlation between the adsorption energy of benzyl alcohol and its conversion percent, accordance to the experimental trend.

Efficient and Selective Photocatalytic Oxidation of Benzylic Alcohols with Hybrid Organic–Inorganic Perovskite Materials

The impressive optoelectronic performance and low production cost of metal halide perovskites have inspired applications well beyond efficient solar cells. Herein, we widen the materials engineering options available for the efficient and selective photocatalytic oxidation of benzylic alcohols, an industrially significant reaction, using formamidinium lead bromide (FAPbBr3) and other perovskite-based materials. The best performance was obtained using a FAPbBr3/TiO2 hybrid photocatalyst under simulated solar illumination. Detailed optical studies reveal the synergetic photophysical pathways arising in FAPbBr3/TiO2 composites. An experimentally supported model rationalizing the large conversion enhancement over the pure constituents shows that this strategy offers new prospects for metal halide perovskites in photocatalytic applications.

Modelling and Simulation of the Radiant Field in an Annular Heterogeneous Photoreactor Using a Four-Flux Model

This work focuses on modeling and simulating the absorption and scattering of radiation in a photocatalytic annular reactor. To achieve so, a model based on four fluxes (FFM) of radiation in cylindrical coordinates to describe the radiant field is assessed. This model allows calculating the local volumetric rate energy absorption (LVREA) profiles when the reaction space of the reactors is not a thin film. The obtained results were compared to radiation experimental data from other authors and with the results obtained by discrete ordinate method (DOM) carried out with the Heat Transfer Module of Comsol Multiphysics® 4.4. The FFM showed a good agreement with the results of Monte Carlo method (MC) and the six-flux model (SFM). Through this model, the LVREA is obtained, which is an important parameter to establish the reaction rate equation. In this study, the photocatalytic oxidation of benzyl alcohol to benzaldehyde was carried out, and the kinetic equation for this process was obtained. To perform the simulation, the commercial software COMSOL Multiphysics v. 4.4 was employed.