Catalysis Surveys from Asia最新文献

The catalytic activity of KMgF₃ catalysts for a Knoevenagel condensation reaction was enhanced by synthesizing the catalysts mechano-chemically. The Brunauer–Emmett–Teller specific surface area and number of strongly basic site on KMgF₃ were increased by applying greater mechanical energy (i.e. a higher rotation rate) during the mechano-chemical process. These increases were caused by stronger mechano-chemical effects such as micronization of the particles and the introduction of lattice defects onto the surface, which resulted in an enhancement of the catalytic activity of KMgF₃ toward a Knoevenagel condensation reaction. X-ray photoelectron spectroscopic analysis revealed that the elemental composition of the KMgF₃ surface was similar to that for K₂MgF₄, indicating the possibility that the true active component for this reaction was K₂MgF₄ rather than KMgF₃. Kinetic measurements revealed that Knoevenagel condensation catalyzed by KMgF₃ was a first-order reaction with an estimated apparent activation energy of 55.8 kJmol⁻¹. A soluble component capable of acting as a catalyst was not present in the solution; the KMgF₃ acted as a true solid catalyst.

The aim of the present work is to investigate an environmentally benign method for the catalytic conversion of biomass derived compounds into fine chemicals. Levulinic acid (LA) is one of the key biomass-derived chemicals that can be converted into biofuels and various other value-added chemicals. n -Butyl levulinate ester is an important chemical used in the production of fuel additives, solvents, plasticizing agents, and odorous substances. The work presented here focused on the esterification of n-butyl levulinate by reaction of LA and n-butanol in the presence of synthesized 20% tungstophosphoric acid (TPA) supported zeolite β (TPA-Zβ), CsTPA-Zβ and Cs-Zβ catalysts. Various catalyst characterization techniques have been used, specifically, XRD, SEM–EDS, FT-IR, nitrogen physisorption and NH₃ -TPD. The highest % yield of n -butyl levulinate is obtained with shorter reaction time in the case of a 20% TPA supported zeolite β catalyst, calcined at 300 °C. The addition of Cs ions to TPA appears to improve catalytic performance.

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Fabrication of composite photocatalysts that provide an easy charge transfer mechanism to enhance the photocatalytic activity is a promising approach for the removal of organic contaminants from the water bodies. In this series, for the first time, we have decorated Ni, Pt, and Pd on the surface of hydrothermally synthesized Cu-doped biphasic Bi2O3. The synthesized composites were analyzed using advanced characterization techniques to uncover the physicochemical properties of the materials. The XRD results revealed well crystalline nature of the materials with enhanced particle size as compared to binary composite. The optical analysis showed the improved optical characteristics of ternary composites. The photocatalytic activity was tested against the RhB and observed the ternary materials with enhanced activity when compared with the binary composite and 5 wt% was the optimum loading of the metal on the surface of Cu- doped Bi2O3. Pd decorated samples showed the highest photo removal of RhB where complete mineralization of dye is achieved only in 50 min which is ascribed to the increased absorption and reduced reunion of charge carriers. The effect of pH of the reaction medium and the role of reactive oxygen species were also examined. In the acidic medium, complete degradation of dye is achieved in 10 min only and holes are found prominent active species for the degradation of RhB. The synthesized materials were stable and could be used many times without significant loss in the photocatalytic activity.

Catalytic synthesis of urea is a bright substitutable to Haber–Bosch progression and industrial urea synthesis. Electrochemical C–N coupling of carbon dioxide and nitrogen oxides under environmental conditions is a newly developed method, which also provides a novel opinion for solving nitrate contamination. Conjugated organic frameworks (COFs) have been used as prospective electrocatalysts for nitrogen reduction reactions and carbon dioxide reduction reactions (CO₂RR) as a result of their regulate structure and multihole properties, resulting in efficient electron transfer. This paper reports the efficient synthesis of urea from carbon dioxide and nitrate over MoM₁S-Pc-M₂PPs COF (M as a transition metal) electrocatalyst. According to the calculation of DFT, it was found that it was difficult for carbon dioxide and nitrogen oxide to coadsorb on MoM₁S-Pc to synthesize urea, so we chose to synthesize CO on the metal porphyrin (M₂PPs) structural unit, and then overflow on the bimetallic phthalocyanine and nitrogen oxide to synthesize urea. The possibility of nitrate adsorption on different catalysts was verified by calculation. We screened the stability, nitrate adsorption strength, and catalytic activity of MoM₁S-Pc candidates, and the results showed that the most promising candidate catalyst was MoFeS-Pc. At the same time, the CO₂RR M₂PPs substrate was also screened, and the VPPs structure was selected as the best. In the study of coupling between different nitrogen-containing intermediates and *CO, the C–N coupling mechanism shows that *NOH and *CO are two possible C–N coupling nitrogen intermediates, which are shown to be thermodynamically spontaneous and have an inferior activation barrier. This study not only provisions novel perceptions into urea synthesis by coupling nitrogen oxides with carbon dioxide under environmental conditions, but also paves the way for boosting the sustainable production of carbon and nitrogen-coupled products.

Functional polymers as solid-supported reagents and catalysts for organic synthesis were conventionally based on cross-linked polystyrene (PS). Polyacrylamide (PAM), modified PAM and their copolymers as hydrophilic support, alternatively can be used as heterogeneous systems in several areas of chemistry and industry. After Regen’s report in 1979 that applied cross-linked PAM as a solid phase cosolvent, PAM-supported reagents and catalysts manifest an excessively important function in various organic reactions. This review summarizes the entire features of PAM and its modified forms and focuses on their most recent and relevant applications in organic transformations. Oxidation–reduction reactions, C–C cross-coupling reactions, and Michael addition reactions are among the most important transformation in which PAM and its derivatives have been widely used. Other reactions like substitution reactions, H₂O₂ decomposition, 1,3-thiazoles synthesis, oxidative esterification, dichlorocyclopropanation, protection of carbonyl compounds, ring opening of epoxides, and dye decolorization have also been investigated. Furthermore, the efficiency, reusability, and limitations associated with these supported systems are discussed.

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Herein, applications of functional polymers based on polyacrylamide, modified PAM and their copolymers for the production of polymer supported reagents and catalysts are reviewed. This review summarizes the entire features of PAM and its modified forms and focuses on their most recent and relevant applications in organic transformations such as oxidation–reduction reactions, C–C cross-coupling reactions, Michael addition reactions etc. Furthermore, the efficiency, reusability, and limitations associated with these supported systems are discussed.

Anisole (methoxybenzene) often serves as a potent biomass model compound in hydrodeoxygenation (HDO) reactions with the primary aim to underpin conditions and operations that facilitate conversion of bio-oil into non-oxygenated fuel. However, the majority of studies in literature has focused on its HDO in a solvent environment under excessive conditions of high hydrogen flow rate and elevated pressures. Herein, we investigate HDO of an evaporated stream anisole on a continues flow reactor over four combination of Ni/Co catalysts supported on Zeolite or Al₂O₃. Catalysts were characterized by various methods which span XRD, SEM-EDS and TPR. The reaction was carried out between 300–600 °C. The highest conversion at 87% was acquired using the Ni–Co/Zeolite catalyst (87%) while producing high yield of phenols and cresols. Synergistic effects brought by the incorporation of Co in the lattice of the catalyst has been discussed. Overall, we obtained a viable HDO path for this biomass model compound using combination of different supported catalysts at moderate operational conditions (relatively intermediate temperatures, ambient pressure, and low H₂/Feed ratio).

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Ni/ZrO₂ (Ni/Zr) and Ni/WO₃-ZrO₂ (Ni/xWZr, x denotes WO₃/ZrO₂ mass ratios) were prepared by the impregnation-direct reduction method and tested for the aqueous phase hydrogenation of phenol to cyclohexanone in an autoclave reactor. It has been found that the Ni-W alloy forms in Ni/xWZr, and a charge transfer occurs from Ni to W. The presence of W species promotes the Ni dispersion and increases the amounts of acid sites and spilt-over hydrogen species. This leads to higher hydrogenation and direct deoxygenation activity of Ni/xWZr than that of Ni/Zr. In addition, the W⁶⁺ and W⁴⁺ species, acted as Lewis acidic sites, may stabilize cyclohexanone and the hydrogenation of cyclohexanone to cyclohexanol is inhibited. Under suitable condition, the phenol conversion and the cyclohexanone selectivity reach 93.1 and 90.6% on Ni/0.8WZr, respectively.

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.

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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.