Efficient Catalytic Oxidation Research Articles

Efficient Catalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid by Magnetic Laccase Catalyst.

2,5-Furandicarboxylic acid (FDCA) is a bio-based platform chemical for the production of polyethylene furanoate (PEF) and other valuable furanic chemicals. A magnetic laccase catalyst with (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) as the mediator has the remarkable capability of oxidizing 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Under optimal reaction conditions, a quantitative yield (90.2 %) of FDCA with complete HMF conversion was obtained after 96 h of reaction. More importantly, the magnetic laccase catalyst exhibited good recyclability and stability, maintaining 84.8 % of its original activity following six reuse cycles. This is the first report on the efficient catalytic oxidation of HMF to FDCA by using an immobilized enzyme catalyst.

Iodine-doped carbon fibers as an efficient metal-free catalyst to activate peroxymonosulfate for the removal of organic pollutants

Developing efficient and metal-free catalytic oxidation systems based on PMS activation has become an increasingly important and challenging objective in the environmental catalysis field.

A facile method for scalable preparation of mesoporous structured SmMnO3 perovskites sheets for efficient catalytic oxidation of toluene

Perovskite-type oxide of SmMnO3 sheet with mesoporous structures was successfully synthesized for the first time by a simple one-step calcination. Citric acid was utilized as the propellant for the construction of SmMnO3 perovskite structure and the mesoporous formation. The characterization results showed that a large number of mesoporous were evenly distributed into the SmMnO3 perovskites sheets by the effect of citric acid. The as-prepared catalyst showed superior catalytic activity and stability for toluene oxidation; the toluene conversion kept ca. 99.9% at 240 °C during the reaction of 36 h. This work could supply an impactful technique to prepare high catalytic activity of ABO3 perovskites with mesoporous structure for the practical applications.

Catalytic oxidation of aqueous organic contaminants by persulfate activated with sulfur-doped hierarchically porous carbon derived from thiophene

Sulfate radicals (SO4−) generated from persulfate (PS) activated by carbocatalysis is expected to provide an environmentally friendly and highly efficient catalytic oxidation process for aqueous organics degradation. Herein, a novel sulfur-doped hierarchically porous carbon with both structural and compositional modification was proposed for PS activation by using thiophene as sulfur/carbon precursor and KOH as activator. The effect of annealing temperature on its textural properties and surface chemistry was characterized by Elemental analysis, N2 sorption isotherms, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, Raman spectra and X-ray diffraction. The as-prepared sample treated at 800°C (SDAC-800) demonstrated outstanding catalytic activity for activation of PS to degrade 4-chlorophenol (4CP). Studies on the role of sulfur in the catalytic activity enhancement were carried out by comparing with a sulfur-free activated carbon and a carbon model (reduced graphene oxide (rGO)). The effects of catalyst dosage, initial 4CP concentration, and reaction temperature on 4CP degradation were comprehensively investigated. In addition, contrast tests with other conventional PS activation methods, SDAC-800 reusability and its general applicability tests were also carried out. The mechanism of PS activation and 4CP oxidation was elucidated by using quenching tests with chloridion, l-histidine and ethanol as radical scavengers. It revealed that the conventional radical pathway was not a critical role in 4CP degradation. In contrast, the process was controlled by both particle-surface interaction and non-radical pathway, and the latter played a dominant role.

Efficient selective catalytic oxidation of benzylic C[sbnd]H bonds by ZIF-67 under eco-friendly conditions

We report here an efficient, mild and green protocol for the chemoselective oxidization of benzylic CH bonds. The reactions were carried out with ZIF-67 as heterogeneous catalyst and tert-butyl hydroperoxide as an oxidant. The desired ketones were achieved in moderate to excellent yields at room temperature under solvent-free and open-flask conditions. Notably, the presented method avoids the use of complex catalyst, toxic organic solvent, additives and high temperature. At the same time, the heterogeneous catalyst could be conveniently reused at least six cycles without significantly decreasing yield of desired product. The gram-scale experiments were achieved with excellent yields and provided a modest and effective method for scale up applications.

Solar-initiated photocatalytic degradation of carbamazepine on excited-state hexadecachlorophthalocyanine in the presence of peroxymonosulfate

In the field of environmental catalysis, the construction of highly efficient and stable catalytic oxidation processes has raised considerable attention. In this study, a novel solar-initiated photocatalytic oxidation system, FePcCl16/PMS/Sunlight, was established by iron hexadecachlorophthalocyanine (FePcCl16) with peroxymonosulfate (PMS) in the presence of sunlight excitation. Under sunlight irradiation, the phthalocyanine ring of the FePcCl16 is motivated to FePcCl16∗ in the excited state, which activates PMS to generate free radicals or high–valent iron(IV)-oxo intermediates (Fe(IV)=O) to oxidize carbamazepine (CBZ). The system could degrade CBZ effectively and total-organic-carbon removal from solution reached nearly 80% within 90min. FePcCl16 catalytic activity was almost without loss and without iron leaching after twenty recycles, indicating that the FePcCl16/PMS/Sunlight was a stable and efficient photocatalytic oxidation system. Electron paramagnetic resonance, gas chromatography-mass spectrometry and photocatalytic-activity-experiment analysis shows that Fe(IV)=O species, singlet oxygen (1O2), hydroxyl and sulfate radicals (OH, SO4−) are the main active species in the catalytic oxidation of CBZ. Density functional theory (DFT) calculations exhibits that the electronic cloud for excited state FePcCl16∗ is transferred from the porphyrazine ring and peripheral substituents to the central Fe atom and its axial position. The main degradation intermediates and possible degradation pathway of CBZ were proposed by ultra-performance liquid chromatography and high-resolution mass spectrometry (UPLC Synapt G2-S HDMS). This study provides efficient catalytic oxidation support for wastewater treatment.

Catalytic asymmetric S -oxidation of N -benzoyl-1,5-benzothiazepines

An efficient catalytic asymmetric oxidation reaction of N-benzoyl-1,5-benzothiazepines using a chiral titanium complex formed in situ from Ti(O-iPr)4, (R, R)-diethyl tartrate was developed. This reaction is helpful for the synthesis of the active form of (E, aS, 1S)-sulfoxide of N-benzoyl-1,5-benzothiazepines which should be recognized by vasopressin receptors. Furthermore, a prospective dynamic kinetic resolution utilizing this system was achieved.

Active and efficient Co-N/C catalysts derived from cobalt porphyrin for selective oxidation of alkylaromatics

The development of highly active and efficient heterogeneous catalytic oxidation systems has become an attractive research area. In this study, nano cobalt-coordinated nitrogen-doped carbon catalysts (Co-N/C), which were prepared by the pyrolysis of cobalt porphyrin supported on carbon black precursor, were used as highly active catalysts for the oxidation of hydrocarbons with tert-butyl hydroperoxide as the oxidant. The results showed that the catalyst was efficient in the selective oxidation of a variety of saturated (including primary, secondary, and tertiary) CH bonds. The catalyst displayed the best catalytic performance, which was comparable to those for previously reported metal oxide catalysts and even better. The resultant Co-N/C catalysts were characterized in detail by XRD, nitrogen adsorption/desorption isotherms, TEM, SEM and XPS. The homogeneous distribution of the Co species and interactions between the Co-N species could improve the synergistic effect between the CoO, CoN and NC species, which led to their excellent catalytic performance. A first order kinetics was observed for the reaction with the apparent activation energy for ethylbenzene oxidation was 22.2±2.1kJmol−1.

Rapid and efficient catalytic oxidation of As(III) with oxygen over a Pt catalyst at increased temperature

The pre-oxidation of arsenite (As(III)) to arsenate (As(V)) is a critical step for the removal of toxic arsenic in wastewater. In this work, a Pt catalyst supported on metal oxide was applied to the pre-oxidation step of As(III) without UV irradiation. It is demonstrated that Pt catalyst can effectively promote the oxidation of As(III) using oxygen at neutral pH due to the catalytic activity of Pt itself. The Pt/ZrO2 catalyst possessed excellent stability and could be used repeatedly with high catalytic performance. The oxidation rate of As(III) was structure-insensitive to Pt particle size and obeyed pseudo-first-order kinetics in As(III). The apparent activation energy was about 31.1kJ/mol, which was obtained on the premise of order of 0.5 with respect to oxygen.

Facile Preparation of Ultrathin Co3 O4 /Nanocarbon Composites with Greatly Improved Surface Activity as a Highly Efficient Oxygen Evolution Reaction Catalyst.

The efficient catalytic oxidation of water to dioxygen plays a significant role in solar fuel and artificial photosynthetic systems. It remains highly challenging to develop oxygen evolution reaction (OER) catalysts with high activity and low cost under mild conditions. Here, a new composite material is reported based on ultrathin 2D Co3 O4 nanosheets and reduced graphene oxides (rGO) by means of a one-pot hydrothermal strategy. The ultrathin Co3 O4 /rGO nanocomposite shows superior stability under alkaline conditions and exhibits an overpotential of 290 mV with a Tafel slope of 68 mA dec-1 , which is much smaller than that of bare Co3 O4 catalyst. Extensive experiments were also carried out using 0D CS and 1D CNTs (CS=carbon spheres, CNTs=carbon nanotubes) in place of the 2D rGO. The overpotentials of as-prepared nanocomposites decrease with the increase of the dimension of nanocarbons, suggesting the electrochemistry activity is closely related to the surface area of carbon substrates. In addition, compared with ultrathin 2D Co3 O4 nanosheets with a Co2+ /Co3+ ratio of 1.2, the as-prepared ultrathin Co3 O4 /rGO nanocomposite with a Co2+ /Co3+ ratio of 1.4 contributes to the better OER performance as more oxygen vacancies can be formed in the ultrathin Co3 O4 /rGO nanocomposite under the experimental conditions. Compared with other Co3 O4 -containing composite materials reported so far, the ultrathin Co3 O4 /rGO nanocomposites show excellent OER performance.

Efficient Catalytic Oxidation of 3-Arylthio- and 3-Cyclohexylthio-lapachone Derivatives to New Sulfonyl Derivatives and Evaluation of Their Antibacterial Activities.

New sulfonyl-lapachones were efficiently obtained through the catalytic oxidation of arylthio- and cyclohexylthio-lapachone derivatives with hydrogen peroxide in the presence of a Mn(III) porphyrin complex. The antibacterial activities of the non-oxidized and oxidized lapachone derivatives against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Staphylococcus aureus were evaluated after their incorporation into polyvinylpyrrolidone (PVP) micelles. The obtained results show that the PVP-formulations of the lapachones 4b–g and of the sulfonyl-lapachones 7e and 7g reduced the growth of S. aureus.

Mesoporous CuO-TiO2 microspheres for efficient catalytic oxidation of CO and photodegradation of methylene blue

Mesoporous CuO-TiO2 microspheres were synthesized by a simple solution based process. The synthesized products were characterized by XRD, FTIR, Raman spectroscopy, N2 adsorption-desorption study, FESEM, TEM, XPS and UV–vis spectroscopy. The catalytic performances for oxidation of CO and photocatalytic degradation of methylene blue (MB) were studied with the synthesized microspheres. For higher concentration of CuO in the microspheres, the T50 (50% conversion) and T100 (100% conversion) of CO oxidations were found to be 139°C and 168°C, respectively. For lower concentration of CuO in the microspheres having BET surface area of 67.7m2g−1 showed the maximum (about 93%) photodegradation of MB.

Gravity driven ultrafast removal of organic contaminants across catalytic superwetting membranes

Flexible and superwetting carbon nanofibrous membranes were prepared for efficient catalytic filtration oxidation of refractory organic pollutants.

Theoretical investigation of CO catalytic oxidation by a Fe–PtSe2 monolayer

Theoretical prediction of efficient catalytic CO oxidation over a Fe–PtSe2 monolayer.

Low temperature modified sludge-derived carbon catalysts for efficient catalytic wet peroxide oxidation of m-cresol

A sludge-derived carbon catalyst modified at 0 °C revealed excellent catalytic performance in the CWPO reaction of m-cresol.

Manganese complex-catalyzed oxidation and oxidative kinetic resolution of secondary alcohols by hydrogen peroxide.

The highly efficient catalytic oxidation and oxidative kinetic resolution (OKR) of secondary alcohols has been achieved using a synthetic manganese catalyst with low loading and hydrogen peroxide as an environmentally benign oxidant in the presence of a small amount of sulfuric acid as an additive. The product yields were high (up to 93%) for alcohol oxidation and the enantioselectivity was excellent (>90% ee) for the OKR of secondary alcohols. Mechanistic studies revealed that alcohol oxidation occurs via hydrogen atom (H-atom) abstraction from an α-CH bond of the alcohol substrate and a two-electron process by an electrophilic Mn-oxo species. Density functional theory calculations revealed the difference in reaction energy barriers for H-atom abstraction from the α-CH bonds of R- and S-enantiomers by a chiral high-valent manganese-oxo complex, supporting the experimental result from the OKR of secondary alcohols.

Co-Zeolite Imidazolate Frameworks (ZIF-9@Zeolite) as Heterogen Catalyst for Alcohols Oxidation

Cobalt zeolitic imidazolate framework (ZIF-9@Zeolite) was synthesized by Co(II) nitrate, benzylimidazole and zeolite. It was characterized by the FTIR, SEM, TEM and BET methods. Efficient catalytic oxidation of benzyl alcohols into corresponding benzaldehydes was studied using catalytic system of ZIF-9@Zeolite. The effect of different factors such as the amount of oxidant, reaction time and reaction temperature on the oxidation reaction was investigated. Interestingly, ZIF-9@Zeolite was very efficient for the oxidation reaction of alcohols and a high yield of aldehydes could be obtained.

Studies on green and efficient catalytic oxidation of a triazole compound

1-Methyl-3,5-dinitro-1,2,4-triazole is an insensitive energetic compound that can be prepared by oxidizing the nitrate salt of 1-methylguanazole. The influence of the reaction time, reaction temperature, reactant ratio, feeding method and catalytic oxidation method on the yield were discussed. The results show that the optimum reaction conditions are as follows: mass ratio of sodium tungstate to nitrate salt to 1-methylguanazole, 4:4.4; time, 5.5h; and temperature, 65-75°C. The yield of this oxidation reaction reached 51.36%.

Highly efficient microwave catalytic oxidation degradation of p-nitrophenol over microwave catalyst of pristine α-Bi2O3

Microwave catalytic oxidation degradation (MCOD) process over microwave (MW) catalyst of pristine bismuth oxide (Bi2O3) was developed to high-efficiently treat p-nitrophenol (PNP) polluted water. The facile prepared catalyst was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption. The major influencing parameters were investigated and the results showed that the degradation efficiency and the TOC removal ratio reached up to 99.74% and 94.20% respectively in the absence of extra oxidants or air bubbling under the optimal conditions. The PNP degradation efficiency of the seventh round still highly reached 97.80%. Furthermore, the reaction kinetics were studied which were accorded well with pseudo-first-order model and the rate constant was 0.883min−1. Moreover, the existence of hydroxyl radical (OH) was confirmed by the fluorescent probe technique. The mechanism of the MCOD process was that the Bi2O3 could be excited to generate electron–hole pairs by MW irradiation, then the H2O absorbed on the surface of the catalyst could be transformed into OH due to the holes. This work provides a clear demonstration that the MCOD method can high-efficiently degrade PNP and develops new MW catalytic pathways for the treatment of wastewater containing refractory organic contaminants.

CuO catalysts supported on activated red mud for efficient catalytic carbon monoxide oxidation

Red mud was activated by digestion in hydrochloric acid and re-precipitation with ammonia, and the activated red mud (ARM) was used as the support for preparation of CuO/ARM catalysts by a simple deposition–precipitation method. The prepared catalysts possessed well-structured porosity and high surface area, as characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2-temperature-programmed reduction, X-ray photoelectron spectroscopy, and nitrogen sorption techniques. High activity was observed for CO oxidation on the resultant CuO/ARM catalysts, and the CuO content and precalcination temperature had significant impacts on the catalytic properties. The catalyst calcined at 200°C with 20% CuO loading amount demonstrated the highest catalytic activity, suggesting the CuO/ARM as a promising catalyst in the CO oxidation reaction, on the sake of the utilization of waste solids with much low cost of ARM.