Cobalt promoted Ni/MgAl2O4 catalyst in lean methane catalytic oxidation

In the present research, magnesium aluminate spinel was prepared as catalyst support using a novel, facile, and efficient mechanochemical method. The Co-promoted catalysts with 20 wt.% of Ni were fabricated using an impregnation route and the samples were analyzed by the X-ray diffraction (XRD), N₂ adsorption/desorption (BET), temperature-programmed reduction and desorption (H₂-TPR and O₂-TPD), and field emission scanning electron microscopy (FESEM) tests. The results confirmed that all samples have a mesoporous structure with a high specific surface area and the presence of cobalt caused complete CH₄ oxidation at low temperatures, and no side reactions were observed. The results indicated that the 3%Co-20%Ni/MgAl₂O₄ catalyst was the optimal sample among the prepared catalysts, owing to the improvement of reduction features and oxygen mobility. The 50 and 90% of methane conversion was obtained at 530 and 600 °C, respectively. Also, the influence of calcination temperature, GHSV, and feed ratio was determined on the catalytic activity. The obtained outcomes revealed that the calcination temperature has a significant effect on the textural properties and catalytic efficiency. The sample calcined at 700 °C showed the weakest performance, which was related to the sintering of particles at high temperatures. The catalytic stability showed that the 3%Co-20%Ni/MgAl₂O₄ has acceptable stability during 600 min time of reaction.

Graphical abstract

     

Modified lattice Boltzmann solution for non-isothermal rarefied gas flow through microchannel utilizing BSR and second-order implicit schemes

Journal of Thermal Analysis and Calorimetry - Thermal microscale gas flow was simulated into a coplanar microchannel was simulated at a broad range of Knudsen numbers. Attempts were made to improve...     

Excitation of plant growth in dormant temperature by steady magnetic field

Experimental results of applying a steady magnetic field (20 and 30 mT) on agricultural plants reveal that their growth is more than that of control plants. Considering that these plants have ferritin cells, and each ferritin cell has 4500 Fe atoms, it is obvious that they have an outstanding role in the plants’ growth. As the last spin magnetic moment (SMM) of the Fe atom posed to an external magnetic field (EMF), the composition of SMM and EMF create an oscillator in the system. Then we have a moment of force on ferritin cells. This oscillator exerts its energy, then damps and finally locates in the field direction. The relaxed energy increased the internal temperature (i.e., the effective temperature of the magnetic spin system of plant) so that it is situated in a proper temperature for growing. This phenomenon (temperature increasing) occurs in the initial minutes of applying the magnetic field. So it depends on the number of times of locating the plant in magnetic field in a day (n). If this number (n) passes the critical value, the plant reaches a burning temperature and growth is perturbed. In this paper, the plant growth rate and critical temperature in a steady magnetic field were investigated and formulated theoretically. An innovative result in this research is as follows: if a plant's environment was in the dormant temperature, we could increase the internal temperature of the plant by applying a magnetic field n times in a day (for growth).     

Effect of electric field strength and exposure time on epoxy and high density polyethylene measured by positron annihilation lifetime

Using the positron annihilation lifetime technique, the annihilation parameters have been measured for epoxy and high density polyethylene (HDPE) as a function of AC electric field strength and the exposure time. The lifetime spectra have been resolved into three components, the longest component (I₃₃) is attributed to the pick-off annihilation of o-Ps in the amorphous regions. The intermediate one (I₂₂) is due to the annihilation of free positrons, while the shorter component (I₁₁) stems from self annihilation of p-Ps. In HDPE, the o-Ps parameters ₃ andI ₃ are measured as a function of electric field strengths in the range from 10 to 100 kV/cm exposed for 24 hours. A decrease inI ₃ of 8% is observed from zero to 50 kV/cm followed by an increase of the same order from 50 to 100 kV/cm. By investigating the effect of the exposure time from 2 to 24 hours at 16 and 50 kV/cm, the effect is confirmed and is attributed to the inhibition of o-Ps formation at lower field strength. In epoxy, the effect or exposure time onI ₃ at 166 and 133 kV/cm shows a similar behavior as in HDPE. At 133 kV/cmI ₃ decreases by only 2.5%. On the other hand, the changes in ₃ occur at short exposure times. Again at large times the saturation is obtained. These effects are attributed to the expansion of free volume (increase of ₃) competing at longer exposure times with other phenomena, such as liberation of free radicals, which reduce the o-Ps intensityI ₃ through the conversion to p-Ps. The reactions between o-Ps and free radicals might also lead to free positrons, which could explain the increase ofI ₂ and the decrease of ₃ at longer exposure times.     

Based on MFe2O4 (M=Co,Cu, and Ni): Magnetically recoverable nanocatalysts in synthesis of heterocyclic structural scaffolds

Abstract

Catalysis research under magnetically recoverable nanocatalysts is a well-known topic in organic synthesis. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of ferrite nanoparticles based on their ability to recovery and reusability. In this review, the focus is on the fabrication, characterization and of application the MFe₂O₄ (M=Co, Cu, and Ni) nanocatalysts in synthesis of heterocyclic structural scaffolds.     

4,4-Acetalidine-bis-(3-methyl isoxazolone-5) as a new colorimetric reagent for the determination of palladium and uranium

Summary Palladium and uranium react with 4,4-acetalidine-bis-(3-methyl isoxazolone-5) in acid medium to give yellow color having a visual limit of identification at 2 and 15g per ml. This color reaction provides the basis of a new method for colorimetric determination of palladium and uranium. Copper also gives yellow color but it cannot be determined with this color reaction because the color intensity is not stable. The maximum tolerable limit of various ions is reported.

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Zusammenfassung Pd und U reagieren in saurem Milieu mit 4,4-Acetalidin-bis-(3-methyl-isoxazolon-5) unter Gelbfärbung mit einer Erfassungsgrenze von 2 bzw. 15g/ml. Diese Farbreaktion dient als Grundlage für eine neue kolorimetrische Methode für Pd und U. Cu gibt zwar auch eine Gelbfärbung, kann aber damit nicht bestimmt werden, da die Farbintensität nicht beständig ist. Die maximal tolerierbare Menge der Fremdionen wird angegeben.

     

Domino "[3+3]-cyclization-homo-Michael" reactions of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes

The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied.     

Low-Field NMR Relaxation Analysis of High-Pressure Ethane Adsorption in Mesoporous Silicas

Understanding the behaviour of short-chain hydrocarbons confined to porous solids informs the targeted extraction of natural resources from geological features, and underpins rational developments in separation, storage and catalytic conversion processes. Herein, we report the application of low-field (12.7 MHz) ¹H nuclear magnetic resonance (NMR) relaxation measurements to characterise ethane dynamics within mesoporous silica materials exhibiting mean pore diameters between 6 and 50 nm. Our measurements provide NMR-based adsorption isotherms within the range 25–50 bar and at ambient temperature, incorporating the ethane condensation point (40.7 bar at our experimental temperature of 23.6 °C). The quantitative nature of the acquired data is validated via a direct comparison of NMR-derived excess adsorption capacities with ex situ gravimetric ethane adsorption measurements, which are demonstrated to agree to within 0.2 mmol g⁻¹ of the observed ethane capacity. NMR relaxation time distributions are further demonstrated as a means to decouple interparticle and mesopore dominated adsorption phenomena, with unexpectedly rapid relaxation rates associated with interparticle ethane gas confirmed via a direct comparison with NMR self-diffusion analysis.     

Magnetically reusable nanocatalysts in biginelli synthesis of dihydropyrimidinones (DHPMs)

Abstract

Molecules containing dihydropyrimidinone (DHPMs) structures are very important in pharmaceutical and medicinal chemistry due to their excellent biological activities application in synthesis of natural products. Biginelli condensation reaction between an aldehyde, urea/thiourea and a carbonyl compound is the most popular strategy for the synthesis of dihydropyrimidinones. Magnetic recoverable nanocatalysts can be readily separated from reaction medium by using an external magnet, without the need for filtration, centrifugation or other tedious workup processes. In recent times, the catalytic potential of magnetically recoverable nanocatalysts was evaluated in a variety of Biginelli reactions. In this review, we focus on the application of magnetically recoverable gold nanocatalysts in Biginelli synthesis of dihydropyrimidinone derivatives.     

SOLVENT-FREE CONVERSION OF OXIRANES TO THIIRANES WITH THIOUREA

A simple and efficient method for the conversion of various oxiranes to the corresponding thiiranes using thiourea under solvent free conditions is described.