Catalysis Surveys from Asia最新文献

To prepare an efficient magnetic bionanocomposite and to protect ferrite nanoparticles from oxidation and aggregation, the prepared Fe₃O₄ was supported by chitosan and tannic acid as the first and second coating layers respectively, and the presence of empty orbitals of Fe₃O₄ and multiple phenol groups on the surface of bionanocomposite leads to the activation of raw materials in acid catalyst reactions. Fe₃O₄@chitosan-tannic acid was fully characterized by FT-IR, TGA, EDX, VSM, FESEM, and TEM. To examine the catalytic activity, it was applied for the first time for the synthesis of a series of 4-nitro-5-phenyl-1,2-dihydro-5 H-benzo[g]thiazolo[3,2-a]quinolines-6,11-dione with potent antitumor activity from β-nitro-thiazolidine, 2-hydroxy-1,4-naphthoquinone and various aromatic aldehydes via an aza-ene reaction followed by intramolecular cyclization. Some of this procedure’s prominent advantages include obtaining the products in short reaction times with high yields, the environmentally benign character of the catalyst, and the facility of catalyst separation and recycling of it due to the existence of the superparamagnetic core.

Graphical Abstract

Three-dimensional nanoflowers were successfully synthesized by using a simple self-assembly reaction of sandwich polyoxometalate, [P₂W₁₈Ce₃(H₂O)₂O₇₁]¹²⁻ (P₂W₁₈Ce₃) and diethylenetriamine. The results showed that the size and morphology of the nanoflowers are controlled by diethylenetriamine concentration and reaction cultivation time. This reaction is mainly proceeded by hydrogen bonds formation and electrostatic interaction between polyoxometalate and alkylamine. The results showed that by calcining the catalytic efficiency of inorganic–organic nanohybrids improved. Further investigations showed that, the issue quality, the morphology of inorganic–organic nanohybrids and the structure of the polyoxometalate have changed due to calcination. The catalysts were characterized by Fourier transforms infrared, powder X-ray diffraction, scanning electron microscopy, N₂ adsorption–desorption isotherms and thermogravimetric analyses, and their catalytic efficiency in the decomposition reaction of cationic and anionic dyes and oxidation of sulfide was investigated.

In this work, comparative testing of the activity of low-percentage palladium and palladium-nickel catalysts supported on activated diatomite with a commercial nickel catalyst from BASF was carried out in the process of hydrogenation of polyalphaolefins (PAO-4). It has been found that palladium catalysts carry out the process under milder conditions, demonstrate higher activity compared to nickel catalysts, significantly reduce the process time, and provide a higher degree of hydrogenation. The activity of bimetallic catalysts is lower than that of monometallic palladium catalysts. Furthermore, Ni exhibits a reaction temperature of at least 150 °C, while Pd is at least 110 °C. If nickel is a single-use catalyst, then when palladium is used 5 times remains an excellent catalytic activity. Catalyst activity is related to the form of adsorbed hydrogen, and on Pd catalyst hydrogen is weakly bound form, while on Ni hydrogen is strongly bound form. The physicochemical characteristics of catalysts and polyalphaolefin oils also have been determined.

Enhanced oxygen vacancy (V_O) has been designated as an effective strategy to prepare high-performance MnO₂ nanocatalysts for the oxidation of volatile organic compounds (VOC) for thereof unbalanced electronic structure, and rapid electron transfer which may even reduce the reaction temperature down to room temperature. Herein, the effects of the V_O on the catalytic performance of nano-sized MnO₂ were discussed by classifying the V_O into surface-anchored and bulk-involved ones. Currently used introducing and modulating methods for V_O including elemental doping, energetic particle bombardment, atmosphere heat treatment, mechanical chemistry, and redox methods are detailly reviewed. Corresponding regulating mechanisms for V_O are expounded. Commonly used characterization methods including ESR, XPS, HRTEM, and UV-vis are reviewed. Furtherly, the unveiled question which is highly expected to be answered on V_O of MnO₂ nanocatalysts is proposed. The purpose of this review is to present the current status of research on MnO₂ nanoparticles and to provide researchers with basic research ideas.

Gold nanoparticles supported on hydroxyapatite functions as a very efficient catalyst for the reduction of nitroarenes as well as for the degradation of azo dyes. The reaction takes place in aqueous medium at room temperature, using sodium borohydride as the source of hydrogen. The catalyst was prepared by a deposition–precipitation process using gold (III) chloride trihydrate solution containing hydroxyapatite as the support. The catalyst was thoroughly characterized by a pltehora of analytical techniques viz., TEM, HRTEM, FESEM, powder XRD, EDX and FTIR. The catalyst was then employed after optimization of reaction conditions. No additives or inert atmosphere was required and a very low loading of gold was sufficient enough to promote the reaction. Reaction kinetics studies were performed on the reduction of 4-nitrophenol to 4-aminophenol and a very high apparent rate constant of 1.63 × 10^–2 s⁻¹ was obtained. Reaction kinetics studies have also been demonstrated for the degradation of methyl orange and congo red dyes. Appreciable apparent rate constants namely 8.678 × 10⁻³ and 3.464 × 10⁻³ s⁻¹ were obtained for the degradation of methyl orange and congo red dyes respectively. The catalyst was recoverable by simple centrifugation and can be reused for at least five reaction cycles.

Present study focused on the green nanocomposites synthetization to treat textile wastewater and its reusability for agriculture crops. Punica granatum (leaves and peels) and biomass (almond shells, sugar cane bagasse, eggshells) are used for synthesis of zinc oxide nanocomposites (PGL-ZnO), copper nanocomposites (PGP-Cu) and iron nanocomposites (PGL-Fe). It is characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, X-ray powder diffraction and Brunauer–Emmett–Teller. The highest adsorption efficiency of all synthesized nanocomposites was accomplished at pH 2 which is acidic, 0.01 g dose, 50 mg/L initial dye concentration and 90 min contact time at 40 °C temperature. The highest adsorption proficiency Punica granatum = 18 < Zinc Oxide nanocomposites = 78 < Iron nanocomposites = 65 < Copper nanocomposites = 85 mg/g of all synthesized nanocomposites was obtained. The model Freundlich showed good fitness results which indicate complex nanocomposites nature. The 1st order showed best results on fitness of isotherm on kinetic data and rate constants determined the best fitness of model. The negative value of ΔH^o and ΔS^o of nanocomposites exhibited the exothermic nature and decrease in disorderness of adsorption process for dye exclusion. When values of (Delta {G}^{o}) is positive then the reaction is spontaneous. Desorption of acidic dye from maximum efficient nanocomposites was 99 mg/g using eluent. Hence, it was determined that these nanocomposites serve as the novel, feasible, cost-effective, ecofriendly, and bio recyclability for treating acid dye-containing wastewater.

Graphical Abstract

The loss of catalyst activity over time is a serious challenge in the industry and therefore performing the regeneration process is essential, especially for the catalysts that contain rare and expensive metals with adverse environmental impacts. This work focuses on the recovery of the Pt-based catalysts deactivated in the alkanes’ industrial dehydrogenation process. The Pt re-dispersion process on the catalyst surface was successful in the case of the regenerated catalyst. While fresh catalysts stayed intact when exposed to water during H₂ reduction, the regenerated catalysts were sensitive to hydrogen humidity throughout the reduction period. This could be related to the kinetic inhibiting effect of water molecules due to chlorine stripping. The design of experiments (DOE) technique was applied to statistically evaluate the factors that affect the activity of the regenerated catalysts. The optimum levels for the operating variables such as purity, flow rate, the humidity of hydrogen, as well as temperature and duration of the reduction were found to be 99%, 13 L/h, 20 ppm, 460 °C, and 4 h, respectively. These findings are very important as they are obtained based on realistic conditions, close to those applied in the industrial process. Consequently, this study offers new opportunities for the industrial dehydrogenation of long-chain alkanes from a practical, economic, and environmental point of view.

Two organic–inorganic mesoporous hybrid materials containing iron complexes covalently attached to mesoporous silica MCM-41 have been successfully prepared via post-functionalization modification of MCM-41 (with trifunctional ligand and without the ligand). The catalysts were characterized by Fourier transforms infrared spectra, powder X-ray diffraction, scanning electron microscopy, and N₂ adsorption/desorption. For the composite MCM-41/3,4,5-tri hydroxyphenyl acetic acid/Fe and MCM-41/Fe materials, in the presence of DTAB (dodecyl trimethylammonium bromide), results showed the formation of more stable MCM-41 structure with the higher surface area than in the presence of CTAB (cetyltrimethylammonium bromide) surfactants. The catalysts were tested in the synthesis of 5-substituted 1H-tetrazoles. This catalyst is an efficient catalyst for [3 + 2] cycloaddition with NaN₃ to prepare 5-substituted 1H-tetrazoles. The catalyst was recycled for up to seven cycles without significant loss of activity.

By employing the Knoevenagel–Michael tandem cyclocondensation of malononitrile, aldehydes, and resorcinol, we developed a green method for the radical synthesis of 2-amino-4 H-chromene scaffolds. A photo-induced electron transfer (PET) photocatalyst was employed in an aqueous solution to use visible light as a renewable energy source. This study aims to develop a non-metal dye that is inexpensive and easily accessible. In addition to having speed-saving features and being simple to use, the photochemically catalyzed AYG demonstrates high yields, energy efficiency, and environmental friendliness. This makes it possible to track changes in chemical and environmental variables throughout time. It is amazing that gram-scale cyclization is practical, proving that it has industrial applications.