Performance In Aerobic Oxidation Research Articles

Cobalt-doped g-C3N4/MOF heterojunction composite with tunable band structures for photocatalysis aerobic oxidation of benzyl alcohol

Due to decrease environmental pollution and energy crisis, it is necessary to find an excellent solution to utilize visible light with photocatalyst technology. Therefore, it can be argued that the use of photocatalysts as well as clean and natural solar energy can be considered as an efficient and promising solution. Constructing heterostructure photocatalysts with metal-organic frameworks (MOFs), and graphitic carbon nitride (g-C3N4-Co) is a powerful viewpoint to obtain high performance in visible-light photocatalysis. In this work, we prepared a heterostructure photocatalyst using Zn-based MOF and cobalt-doped graphitic carbon nitride (g-C3N4-Co) termed TMU-22/g-C3N4-Co. Characterization of TMU-22/g-C3N4-Co composite was performed by PXRD, FT-IR, TGA, SEM, EDS, UV-vis DRS, and BET. This composite showed a high performance in aerobic oxidation of benzyl alcohol to benzaldehyde under visible-light irradiation in mild conditions (at atmospheric pressure and room temperature) which comes from the cooperative performance of g-C3N4-Co and TMU-22(Zn) components. Additionally, studies performed using radical scavengers indicated that electrons and holes serve as the main reactive species. The superior photocatalytic activity of the composite is attributed to the enhanced separation of the photogenerated electron-hole pairs, as well as increased visible-light absorption.

Efficient Aerobic Oxidation of 5-Hydroxymethylfurfural to 2, 5-Furandicarboxylic Acid over a Nanofiber Globule La-MnO2 Catalyst

A La-MnO2 catalyst exhibited excellent performance in aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Characterization of the samples revealed that the loos...

Metal-Support Synergy of Supported Gold Nanoclusters in Selective Oxidation of Alcohols

Gold catalysts have been reported to exhibit good performance in aerobic oxidation of alcohols, but the intrinsic origin of the catalytic reactivity is still illusive. The catalyst preparation method, the morphology of the gold particles, and even the support might be key factors that determine the activity. Here, we prepared a series of gold catalysts with different supports, i.e., the hydrotalcite (HT), ZnO, MgO, Al2O3, and SiO2, by using the atomically controlled Au25 nanoclusters (NCs) as the gold precursor. The characterization results of the X-ray diffraction (XRD), UV-vis and transmission electron microscopy (TEM) show that the gold particles were mostly uniformly distributed on the supports, with a mean particle size within 3 nm. In aerobic oxidation of benzyl alcohol, the MgAl-HT- and Al2O3-supported Au25 NCs display good performances, with turnover frequency (TOF) values of ~2927 and 2892 h−1, respectively, whereas the SiO2-, MgO-, and ZnO-supported analogues show much inferior activity. The high resolution TEM and X-ray photoelectron spectra (XPS) results suggest that the interactions between gold and the supports in different samples are differing, which influences the morphology and the nature of gold. Our results further point to the importance of acid-base property of the support and the metal-support synergy rather than the gold particle size alone in achieving high-performance in selective alcohol oxidation. Moreover, this work provided a good way to design gold catalysts with controllable sizes that is crucial for understanding the reaction process in aerobic oxidation of alcohol.

Ultralow Loading Cobalt-Based Nanocatalyst for Benign and Efficient Aerobic Oxidation of Allylic Alcohols and Biobased Olefins

The synthesis of α,β-unsaturated ketones from aerobic oxidation of allylic alcohols and biobased olefins serves as an important topic in green and sustainable chemistry. In this work, we report the utilization of a sacrificial template ZIF-8 for preparation of mesoporous Co0.05/N–C material with an ultralow cobalt loading of 0.05 wt %, in which the excellent catalytic performance in aerobic oxidation of α-pinene and cinnamyl alcohol was achieved with an 85% yield of verbenone and a yield of cinnamaldehyde, respectively. The results of control experiments and several characterization investigations further illustrate that the sacrificial template ZIF-8 plays a key role to disperse well metallic cobalt in the Co0.05/N–C-800 catalyst and an appropriate cobalt content of 0.05 wt % is beneficial for benign and efficient aerobic oxidation of various allylic alcohols and biobased olefins. In addition, the Co0.05/N–C-800 catalyst also exhibited good stability and reusability for recovering and reusing at least six times without obvious decrease in catalytic activity. The presented efficient nanocatalyst thus triggers facile synthesis of a series of α,β-unsaturated aldehydes/ketones in high yields.

Copper nanoparticles advance electron mobility of graphene-like boron nitride for enhanced aerobic oxidative desulfurization

Recently, graphene-like boron nitride (g-BN), has been developed a new application, as a catalyst for aerobic catalysis, which gives it a passport to catalytic field. However, its way to be a high-active one is blocked by its insulation property. In this work, copper nanoparticles (Cu NPs) with nano-size and low resistivity, are confined through g-BN (Cu NPs/g-BN) to boost electron mobility by a simple one-pot pathway. Experiments show that Cu NPs/g-BN hosts a better performance in aerobic oxidation of aromatic sulfur compounds with a catalytic activity of >97%. Cyclic voltammetry (CV) curves give a testimony that the presence of Cu NPs for raised electron mobility is a key element to the high catalytic activity. Besides, the catalyst can be recycled for 10 times without significant decrease in aerobic catalytic activity, which is found to be related with the idiosyncratic oxidation-resisting property of Cu NPs. Experiments find that the extraordinary oxidation-resisting property of Cu NPs mainly relates to the existence of g-BN, which can keep Cu NPs away from being oxidized. This work provides another sight for enlargement of application of g-BN for aerobic catalysis and a new strategy for preservation of NPs.

Sulfur-Modified SBA-15 Supported Amorphous Palladium with Superior Catalytic Performance for Aerobic Oxidation of Alcohols

A series of sulfur-modified SBA-15 supported amorphous palladium catalysts are prepared, and the effects of preparation parameters on the aerobic oxidation of benzyl alcohol are systematically investigated. The optimal catalyst exhibits remarkably enhanced catalytic activity (conversion 100 % and selectivity 99 %) and could be separated conveniently. The catalysts are characterized by X-ray diffraction patterns, BET, ICP, X-ray photoelectron spectroscopy, CO chemisorption and transmitting electron microscopy, and the results show that disulfur bond framework in the optimal catalyst act as both a stable linker and a good chelator for Pd species. Pd2+ is reduced to Pd0 with the increasement of the carbon chain lengths between sulfur bonds, which is the cause of deactivation. The mechanism is that a base abstracts a proton from the coordinated alcohol to form a Pd alcoholate species that subsequently undergo β-hydride elimination to give benzyl aldehyde, which is confirmed by the catalytic and characteristic results.

Fabrication and Characterization of Perovskite-Type Oxide LaFe0.9Co0.1O3 Nanoparticles and Its Performance in Aerobic Oxidation of Thiols to Disulfide

LaFe 0.9 Co 0.1 O 3 (LFCO) perovskite nanoparticles were prepared using a sol-gel method. The physical and chemical properties of the catalyst were determined using X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy, scanning tunneling microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The catalytic activity of the sample was evaluated using aerobic oxidation of thiols to disulfides. The XRD results indicated that the LFCO had a good crystalline phase at 750 °C. The experimental data revealed that the LFCO particles were nano-sized. LFCO nanoparticles can catalyze the oxidation of various thiols, including aromatic and aliphatic thiols. The effects of reaction parameters such as temperature, solvent, and the amount of catalyst on the oxidation of 4-chlorothiophenol were investigated. In comparison with reactions using the corresponding neat complexes, i.e., Co(NO 3 ) 2 ·6H 2 O and Fe(NO 3 ) 3 ·9H 2 O, higher yields were obtained in the oxidation reaction catalyzed by LFCO nanoparticles. This study investigates the characterization and catalytic processes of a perovskite-type nanocatalyst (LaFe 0.9 Co 0.1 O 3 ) in the oxidation of various aromatic and aliphatic thiols.