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Development of Sustainable Green Catalysts for Oxidation of Alcohols via Decorated Palladium Nanoparticles on Magnetic Carbon Nanotube/MOF)

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The fascinating properties of the naturally occurring biopolymers and enzymes are benchmark natural materials abetting us to optimize the performance of multifunctional catalytic system based on 3D orientation, propinquity amongst all the active sites and apposite stoichiometry. In the copper/TEMPO/imidazole catalytic triad the formation of (bpy)CuI(NMI) (bpy: bipyridine) (NMI: N-methyl imidazole) facilitated facile oxidation to (bpy)CuII(NMI)-O2·⁻ in the presence of molecular oxygen. In the multicomponent catalytic system TEMPO moiety boost the fixation copper-oxygen radical intermediate. These multifunctional heterogeneous and recyclable catalytic systems (1-6) were prepared by grafting silica surface by orthogonal post-functionalization or single molecule post-functionalization of azide silanes grafted silica with functionalized alkynes (7-12) by CuAAC “click chemistry”. The above said mechanistic studies were pivotal in contriving multifarious copper/TEMPO/imidazole triads involving reaction of the discrete and sequence defined catalytic triads (1-6) to expedite aerobic alcohol oxidation. The catalyst 3a having TEMPO/pyridyl triazole (pyta) dimer grafted in 1:2 stoichiometric ratio outperformed other catalytic systems for the benzyl alcohol oxidation, with high initial TOF value of 63.1. Moreover, the catalyst was recyclable for five consecutive cycles for benzyl alcohol oxidation. This minireview, highlights recent work based on multifunctional CuI/TEMPO/pyta containing triad based heterogeneous catalysts for aerobic alcohol oxidation.
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Effective treatment of emerging organic contaminants (EOCs) is a key concern for human beings. Advanced oxidation processes (AOPs) have become one of the core techniques of EOCs removal because of the high oxidation efficiency, complete mineralization, and controllable process. Sulfate radicals-based AOPs overcome the shortcomings of conventional Fenton processes. The development of efficient catalysts is major limitation of sulfate radicals-based AOPs for EOCs removal from wastewater. Metal organic framework (MOFs) receives growing global attention due to excellent properties of large surface area, flexible synthesis methods, and modifiable structure. Numerous researches have been conducted to fabricate MOFs-based catalysts. Herein, studies on MOFs-based materials as catalysts for catalytic removal of EOCs were summarized. The synthesis methods of MOFs were briefly described. Researches on MOFs materials as persulfate activators were reviewed from the perspective of Fenton-like and photo-Fenton system. Additionally, the effects of process factors including catalyst dosage, persulfate concentration, solution pH, coexisting inorganic anions, natural organic matter, and temperature on the catalytic efficiency were systematically summarized. Finally, the stability and toxicity of MOFs-based catalysts that affect the practical application was discussed. This work provides better understanding of sulfate radicals-based AOPs using MOFs-based catalysts for EOCs removal.
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Alcohol dehydrogenases (ADHs) catalyze the reversible oxidation of primary and secondary alcohols to the corresponding aldehydes or carboxylic acids and ketones, respectively, under mild conditions, which may minimize the environmental impact compared to the traditional chemical counterpart. In this short review, we briefly report recent advances in the development of ADH-catalyzed oxidation employed both as single biocatalysts but also in multienzyme cascades of reactions. Current bottlenecks, prospects, and future outlooks in the field are addressed.
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The design and use of green catalysts and catalytic systems to achieve the dual goals of environmental protection and economic benefits is an important task, and is necessary for the sustainability of the chemical industry. In this study, we reported a facile synthesis and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@[email protected] nanocomposite. Catalytic activity of Fe3O4@[email protected] nanocomposite considered in the C-C cross-coupling reaction in water as green solvent. In addition, the scope of the prepared Fe3O4@[email protected] studied in the synthesis of symmetric diaryl sulfides using 2-thioxo-4-thiazolidinone (Rhodanine) as a green sulfur source.
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From Egyptian mummies to the Chanel n°5 perfume, fatty aldehydes have long been used and keep impacting our senses in a wide range of foods, beverages and perfumes. Natural sources of fatty aldehydes are threatened by qualitative and quantitative variability while traditional chemical routes are insufficient to answer the society shift toward more sustainable and natural products. The production of fatty aldehydes using biotechnologies is therefore the most promising alternative for the flavors and fragrances industry. In this review, after drawing the portrait of the origin and characteristics of fragrant fatty aldehydes, we present the three main classes of enzymes that catalyze the reaction of fatty alcohols oxidation into aldehydes, namely alcohol dehydrogenases, flavin-dependent alcohol oxidases and copper radical alcohol oxidases. The constraints, challenges and opportunities to implement these oxidative enzymes in the flavors and fragrances industry are then discussed. By setting the scene on the biocatalytic production of fatty aldehydes, and providing a critical assessment of its potential, we expect this review to contribute to the development of biotechnology-based solutions in the flavors and fragrances industry.
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Photocatalytic oxidation of alcohols has received more and more attention in recent years following the numerous studies on the degradation of pollutants, hydrogen evolution, and CO2 reduction by photocatalysis. Instead of the total oxidation of organics in the degradation process, the photo-oxidation of alcohols aims at the selective conversion of alcohols to produce carbonyl/acid compounds. Promising results have been achieved in designing the catalysts and reaction system, as well as in the mechanistic investigations in the past few years. This review summarizes the state-of-the-art progress in the photo-oxidation of alcohols, including the development of photocatalysts and cocatalysts, reaction conditions including the solvent and the atmosphere, and the exploration of mechanisms with scavengers experiment, electron paramagnetic resonance (EPR) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The challenges and outlook for the further research in this field are also discussed.
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Alpha and gamma-alumina are materials used as continuous coatings and also in various fields such as ceramics, catalysis and catalytic support, lubricants, and electronics. Boehmite (AlOOH) is used as the raw material for the preparation of alpha and gamma-alumina phases whose properties such as morphology, specific surface area, and porosity, are strongly dependent on the boehmite structure. In this review, various methods for synthesizing boehmite nanoparticles (NPs); including, sol-gel, sedimentation, sewage, and hydrothermal have been reported. The most appropriate method for the production of various forms of boehmite is the hydrothermal method. The shape, morphology, and tissue properties of the boehmite NPs depend heavily on the conditions of the process, i.e. the pH of the solution, the temperature, and the reaction time which will be described in this review. Moreover, the application of boehmite as the catalyst or catalytic support is studied in this review. Therefore, metallic, acidic, basic, ionic, organic, and organometallic catalysts which are immobilized on boehmite NPs are discussed in this review.
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In this paper, the synthesis and characterization of zirconium ferrite ((ZrO)2Fe2O5) magnetic nanoparticles (MNPs) and their application as a catalyst in C–C cross-coupling reaction will be described. The structure of the catalyst was studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM) and ICP-OES analysis. The resulting zirconium ferrite [(ZrO)2Fe2O5] was efficient for C–C coupling reactions, affording the desired products in good to excellent yields. Moreover, the catalyst could be easily recovered by magnetic separation and recycled for four times without significant loss of its catalytic activity.
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Remarkable developments have been accomplished in silica-supported palladium nanoparticles (PdNPs) mediated organic transformations for the generation of Suzuki (C-C), Heck (C=C) and Sonogashira (C≡C) coupling reactions in academic as well as industrial communities. Various synthetic methods were adopted to prepare highly dispersed PdNPs encapsulated within various forms of silica supports. The type of reaction examined, size and shape, stability, and recycling ability of silica-supported PdNPs, and the influence of different reaction parameters on carbon−carbon bond forming reactions are discussed. In these reactions, the silica-supported PdNPs exhibited superior performances compared to their unsupported colloidal metal nanoparticle (MNP), revealing the advantages of designing nanocatalysts. Recent progress in the synthesis, catalytic results, stability, and recycling possibilities of silica-supported PdNPs are discussed along with the prospective outlook of relevant research fields.
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In this study, a new glassy carbon electrode chemically modified with multi-walled carbon nanotubes (MWCNTs) and core-shell structured Fe3O4@[(EtO)3Si–L] was constructed and used for the sensitive and selective electrochemical determination of trace amounts of citalopram (CT). New Schiff base functionalized magnetic Fe3O4 nanoparticle was prepared to use as an effective ionophore in electrochemical responses of the potentiometric sensor for the determination of CT in aqueous solutions. The influences of the effective parameters such as working solution pH and scan rate on the electrochemical behavior of modified electrode were investigated. This electrochemical sensor responds to CT in the wide linear range of 3.00 × 10− 7 to 1.00 × 10− 1 mol L− 1. The detection limit of 5.32 × 10− 8 mol L− 1 was obtained at pH range 3–11. The proposed sensor has a fast response time and can be applied for at least 4 months without any significant divergences in the currents. It shows simple preparation, good reproducibility (RSD = 0.73%), long-term stability (RSD = 1.31%), accuracy in analysis and stable electrochemical sensing of CT in the presence of a large number of vitamins, carboxylic acids, ions and drugs.
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A Pd(II) Schiff base complex as an efficient and highly heterogeneous catalyst was developed by immobilization of a palladium complex on the surface of modified Fe3O4 magnetite nanoparticles. These surface-modified nanoparticles were characterized using various techniques such as transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, elemental analysis and Fourier transform infrared spectroscopy. The palladium catalyst exhibited efficient catalytic activity in Suzuki and Heck coupling reactions. This method has notable advantages such as excellent chemoselectivity, mild reaction conditions, short reaction times and excellent yields. The yields of the products were in the range 85–100%. Also, the nanocatalyst can be easily recovered with a permanent magnet and reused at least five times without noticeable leaching or loss of its catalytic activity. Copyright
Article
Nano Ag/ZnO catalysts were prepared by varying load of Ag on ZnO supports using a new and very simple method. The structure of nano Ag/ZnO has been confirmed by various techniques. The Ag/ZnO with 7.4 × 10-5 mol% of Ag has pore size distribution about 2.74 nm and this nano Ag/ZnO is found to be the best catalyst for oxidation of primary and secondary benzyl alcohols into corresponding aldehydes and ketones in oxidant-free at the atmospheric pressure. The influence of various parameters such as: solvent, base, temperature, time of reaction, etc. has been systematically studied on nano Ag/ZnO catalyst.
Article
The three-dimensional Zr-based metal-organic framework UiO-66-NH2 was functionalized with salicylaldehyde using a post-synthetic modification (PSM) strategy, and then three kinds of copper (II) salts were successfully immobilized onto the surface of the amino-functionalized Zr-MOF. The SEM and PXRD results showed that the morphology and structure of Zr-MOF were retained after multiple transformations. The obtained UiO-66-Sal-CuCl2 catalyst exhibited excellent activity for the selective aerobic oxidation of primary aromatic alcohols using molecular oxygen as the oxygen source. Furthermore, the UiO-66-Sal-CuCl2 catalyst showed a good cycle performance.
Article
Nano-mushroom ZnO and Cu-doped ZnO were prepared by co-precipitation method and characterized by general techniques. The particle size of ZnO is 28 nm, while it decreased to 17 nm by doping Cu²⁺ ion on it. Then, catalytic properties of these nanoparticles were studied in oxidation of benzylic alcohols by 30% H2O2 with nano-catalyst at room temperature. The results showed, a solvent free, green, selective, high yield and effective oxidation. Also, the catalytic performance such as: % conversion, % selectivity and rate of reaction of ZnO are significantly enhanced by doped 1% Cu metal cation on nano ZnO. The ketone and aldehyde are the main product of secondary and primary benzylic alcohols respectively under this condition.
Article
This review gives an overview of direct CH arylation catalyzed by heterogeneous Pd catalysts. The efficiency of the different forms of heterogeneous Pd catalysts is discussed with a critical view of the transformations attainable. If experimental evidence is provided, mechanistic considerations on the true nature of the catalysis, that is, heterogeneous versus homogeneous, are discussed as well.
Article
Palladium catalysts supported on different carbon materials, i.e. graphene, carbon nanotube and activated carbon, have been prepared by improved wet impregnation and employed in the solvent-free aerobic oxidation of aromatic alcohols using molecular oxygen as oxidant. High catalytic activity as well as high selectivity to corresponding carbonyl compounds can be obtained on Pd/graphene. Typically, an extremely high turnover frequency of 30,137 mol/h molPd is observed in the aerobic oxidation of benzyl alcohol to benzaldehyde using Pd/graphene as catalyst. Palladium catalysts on different carbon supports are fully characterized by a series of techniques, e.g. Raman, XRD, SEM, TEM, TG, XPS, FTIR spectra of benzyl alcohol adsorption and O2-TPD. Based on the catalytic and characterization results, the superior reactivity of Pd/graphene in the aerobic oxidation of aromatic alcohols is attributed to the promotion role of graphene support in the adsorption of reactant alcohol and oxygen.
Article
The aerobic oxidation of benzhydrol, 1-phenylethanol and cyclohexanol to corresponding ketones was carried out in poly(ethylene glycol) (PEG-600)/supercritical CO2 (SCCO2) biphasic system using unsupported and supported CoCl2·6H2O as the catalysts. It was demonstrated that CoCl2·6H2O, Co(II)/Al2O3, and Co(II)/ZnO were all active and selective for the reactions. The reactivity of the substrates followed the order benzhydrol>1-phenylethanol>cyclohexanol. Co(II)/ZnO was most stable and could be reused four times without considerable reduction of activity. The effect of CO2 pressure, reaction time and solvent was further investigated. The Co(II)/ZnO/PEG-600 system is active, selective, cheap, clean, and recyclable for the aerobic oxidation of secondary alcohols.
Article
A polyoxometalate–zirconia (POM/ZrO2) nanocomposite was prepared through entrapment of H3PW12O40 polyoxometalate into zirconia matrix by sol–gel technique involving the hydrolysis of zirconium (IV) n-butoxide, Zr(n-OBu)4, as the ZrO2 source. The catalyst was characterized by using XRD, FT-IR, SEM, TEM and surface area measurement and used as an efficient heterogeneous photocatalyst for aerobic oxidation of alcohols. Various primary and secondary benzylic alcohols were oxidized into the corresponding aldehydes and ketones in high yields under O2 atmosphere in the presence of photoexcited POM/ZrO2 nanocomposite. Also, nonactivated aliphatic alcohols were oxidized in good yields albeit after longer reaction times in comparison with benzylic alcohols, so that the selective oxidation of a benzylic OH group in the presence of a non-benzylic OH group could be achieved by the appropriate choice of the reaction time. The photocatalyst has been reused several times, without observable loss of activity and selectivity. Indeed, the photocatalytic activity of the POM/ZrO2 was higher than that of pure POM.