Efficient Oxidation of Cyclohexane over Bulk Nickel Oxide under Mild Conditions

Nickel oxide powder was prepared by simple calcination of nickel nitrate hexahydrate at 500 °C for 5 h and used as a catalyst for the oxidation of cyclohexane to produce the cyclohexanone and cyclohexanol—KA oil. Molecular oxygen (O₂), hydrogen peroxide (H₂O₂), t-butyl hydrogen peroxide (TBHP) and meta-chloroperoxybenzoic acid (m-CPBA) were evaluated as oxidizing agents under different conditions. m-CPBA exhibited higher catalytic activity compared to other oxidants. Using 1.5 equivalent of m-CPBA as an oxygen donor agent for 24 h at 70 °C, in acetonitrile as a solvent, NiO powder showed exceptional catalytic activity for the oxidation of cyclohexane to produce KA oil. Compared to different catalytic systems reported in the literature, for the first time, about 85% of cyclohexane was converted to products, with 99% KA oil selectivity, including around 87% and 13% selectivity toward cyclohexanone and cyclohexanol, respectively. The reusability of NiO catalyst was also investigated. During four successive cycles, the conversion of cyclohexane and the selectivity toward cyclohexanone were decreased progressively to 63% and 60%, respectively, while the selectivity toward cyclohexanol was increased gradually to 40%.     

CuII@PAA/PVC mesoporous fibers: A hybrid wedding as a high-performance versatile heterogeneous catalyst for A3, KA2, and decarboxylative A3 reactions

Efforts made on the development of a novel, simple, cost-effective, and efficient approach to fabricate a copper catalyst immobilized on mesoporous poly (acrylic acid)/poly (vinyl chloride) hybrid fibers (Cu^II@PAA/PVC) for versatile catalytic applications in A₃, KA₂, and decarboxylative A₃ couplings has been described in this present work. The characterization of the mesoporous hybrid fibers was well performed by BET, FTIR, SEM, EDX, XPS, and TGA techniques. The pore structure and surface area were calculated by using BET measurement analysis. The obtained mesoporous Cu^II@PAA/PVC fibers exert high catalytic performance in the synthesis of propargylamines via one-pot A₃, KA₂, and decarboxylative A₃ reactions over a series of substrates without employing expensive ligands or inert atmosphere. The active Cu²⁺ species chelating with carboxylate groups in PAA/PVC hybrid fibers plays a key role in the catalysis. Meanwhile, the unique mesoporous structure and fiber morphology facilitate a better mass transfer and enlarge its contact area with substrates in the course of a reaction. Moreover, the Cu²⁺–carboxylate chelation could suppress the leaching of active Cu²⁺ species from the catalyst and thus lead to the catalyst has excellent performance and good durability as well as reusability.     

Ultrasonic and bio‐assisted synthesis of Ag@HNTs‐T as a novel heterogeneous catalyst for the green synthesis of propargylamines: A combination of experimental and computational study

A novel heterogeneous catalyst is prepared through functionalization of halloysite nanotube with 1H‐1,2,3‐triazole‐5‐methanol and subsequent immobilization of silver nanoparticles through bio‐assisted approach using Arctiumplatylepis extract. The resulting catalyst, Ag@HNTs‐T, was characterized by using SEM/EDX, BET, XRD, FTIR, ICP‐AES, TGA, DTGA and elemental mapping analysis. Moreover, we computationally assessed metal‐ligand interactions in Ag@HNTs‐T complex model to interpret the immobilization behavior of silver nanoparticles on HNTs surface via quantum chemistry computations. The catalytic activity of the catalyst was studied for the synthesis of propargylamines via A³ and KA² coupling reactions under ultrasonic irradiation. The results demonstrated that Ag@HNTs‐T could efficiently promote these reactions to furnish the corresponding products in high yields and short reaction times. The study of the recyclability of the catalyst and Ag(0) leaching confirmed that the catalyst was recyclability up to four reaction runs with slight Ag(0) leaching.     

An iterative analytic–numerical method for scattering from a target buried beneath a rough surface

An efficiently iterative analytical-numerical method is proposed for two-dimensional （2D） electromagnetic scattering from a perfectly electric conducting （PEC） target buried under a dielectric rough surface. The basic idea is to employ the Kirchhoff approximation （KA） to accelerate the boundary integral method （BIM）. Below the rough surface, an iterative system is designed between the rough surface and the target. The KA is used to simulate the initial field on the rough surface based on the Fresnel theory, while the target is analyzed by the boundary integral method to obtain a precise result. The fields between the rough surface and the target can be linked by the boundary integral equations below the rough surface. The technique presented here is highly efficient in terms of computational memory, time, and versatility. Numerical simulations of two typical models are carried out to validate the method.     

粗糙面重构问题的混合算法研究

基于Desanto的谱表示法,采用数值和近似算法相结合的混合算法对一维粗糙面的重构问题进行了研究.对于正问题,采用数值算法——矩量法(MOM)得到一维粗糙面的相关散射数据,对于逆问题,考虑不同粗糙度的粗糙面,分别采用两种近似算法——微扰近似(SPA)、基尔霍夫近似(KA)与矩量法的混合算法,对粗糙面轮廓进行了重构;数值结果以高斯粗糙面为例,给出了混合算法对不同粗糙度粗糙面的重构算例,并进行了数据比较和分析. 关键词： 粗糙面重构 矩量法 微扰近似 基尔霍夫近似     

KAlF_4∶ Ce,Tb磷光体的发光特性及Ce~(3+)对Tb~(3+)的敏化作用

采用溶液反应法和高温固相反应法合成了ＫＡ１Ｆ４基质化合物及ＫＡ１Ｆ４∶Ｃｅ，Ｔｂ磷光体，测定了磷光体的激发光谱和发射光谱，研究了在碱金属氟铝酸盐基质中Ｃｅ３＋对Ｔｂ３＋的能量传递，根据Ｃｅ３＋、Ｔｂ３＋在ＫＡｌＦ４中的能级关系，分析了其发光特性和Ｃｅ３＋对Ｔｂ３＋能量传递过程     

Preparation of Ag‐doped g‐C3N4 Nano Sheet Decorated Magnetic γ‐Fe2O3@SiO2 Core–Shell Hollow Spheres through a Novel Hydrothermal Procedure: Investigation of the Catalytic activity for A3, KA2 Coupling Reactions and [3 + 2] Cycloaddition

Taking advantageous of both g‐C₃N₄ and magnetic core‐shell hollow spheres, for the first time a heterogeneous and magnetically separable hybrid system was prepared through a novel and simple hydrothermal procedure and used for immobilization of bio‐synthesized Ag(0) nanoparticles. The hybrid system was fully characterized by using SEM/EDS, FTIR, VSM, TEM, XRD, TGA, DTGA, ICP‐AES, BET and elemental mapping analysis. The catalytic utility of the obtained system, h‐Fe₂O₃@SiO₂/g‐C₃N₄/Ag, for promoting ultrasonic‐assisted A³, KA² coupling reactions and [3 + 2] cycloaddition has been confirmed. The results established that the catalyst could efficiently catalyze the reaction to afford the corresponding products in high yields in short reaction times. The reusability study confirmed that the catalyst could be recovered and reused for at least five reaction runs with only slight loss of the catalytic activity. The hot filtration test also proved low silver leaching, indicating the heterogeneous nature of the catalysis.     

The Mechanism Study on the Catalytic Synthesis of 2,6‐Dimethylphenol from KA‐Oil and Methanol over Magnesium Oxide Catalysts

Catalytic synthesis of 2,6‐dimethylphenol from KA‐oil (a mixture of cyclohexanol and cyclohexanone) and methanol was achieved by using magnesium oxide‐supported chromium oxide catalysts in one step. At higher conversion (> 90%), dimethylphenol was formed in high yield (>60 %). The activity of Cr/MgO catalysts depended on the concentration of chromium. The yield of 2,6‐dimethylphenol was also affected by the composition of the ratio of cyclohexanol to cyclohexanone in KA‐oil. Cyclohexanol and cyclohexanone reacting with methanol under the same conditions indicated that pure cyclohexanol or cyclohexanone is less reactive than their mixture, KA‐oil. The adsorption properties of cyclohexanol and cyclohexanone on the surface of Cr/MgO determined by FT‐IR spectroscopy suggest that cyclohexanone is easily reduced to cyclohexanol by the hydrogen which formed in the reaction, and then further reacted with methanol to form 2,6‐dimethyphenol.     

Numerical and experimental studies on the effects of stage risers

The acoustic effects of stage risers, especially on the sound of lower string instruments, are numerically and experimentally analyzed. To discuss the effects of the vibration of riser’s boards due to the mechanical force from an instrument, a structural-acoustical coupling approach is applied based on the mode expansion and the boundary element technique. Measurement results of the mechanical force from real instruments are used in the numerical study. The vibration of the top board of a riser affects the sound field only around the natural frequencies of the board and the cavity of the riser. In contrast, the acoustic diffraction due to the riser affects the sound field in a wide frequency range. The riser’s sideboard that faces to receiving points increases the sound pressure levels because it reflects waves diffracted at the riser’s edge to the front. To verify the numerical results, the effects of acoustic diffraction due to risers are especially investigated in detail through a scale model experiment.     

Rapid analysis of interaction between six drugs and β2‐adrenergic receptor by injection amount‐dependent method

Drug–protein interaction analysis has become a considerable topic in life science which includes clarifying protein functions, explaining drug action mechanisms and uncovering novel drug candidates. This work was to determine the association constants (K _A ) of six drugs to β ₂‐adrenergic receptor by injection amount‐dependent method using stationary phase containing the immobilized receptor. The values of K _A were calculated to be (25.85 ± 0.035) × 10⁴ m ⁻¹ for clorprenaline, (42.51 ± 0.054) × 10⁴ m ⁻¹ for clenbuterol, (6.67 ± 0.008) × 10⁴ m ⁻¹ for terbutaline, (33.99 ± 0.025) × 10⁴ m ⁻¹ for tulobuterol, (7.59 ± 0.011) × 10⁴ m ⁻¹ for salbutamol and (78.52 ± 0.087) × 10⁴ m ⁻¹ for bambuterol. This rank order agreed well with the data determined by zonal elution, frontal analysis and nonlinear chromatography, even using different batches of β ₂‐AR column. A good correlation was found between the association constants by the current method and radio‐ligand binding assay. Our data indicates that the injection amount‐dependent method is a powerful alternative for rapid analysis of ligand–receptor interactions.