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排序方式: 共有1246条查询结果,搜索用时 46 毫秒
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2‐hydroxyethylammonium formate ionic liquid grafted magnetic nanoparticle as a novel heterogeneous catalyst for the synthesis of substituted imidazoles
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Catalytic one‐pot condensation of benzil, aldehyde and ammonium acetate have been successfully carried out using 2‐hydroxyethylammonium formate (HEAF) grafted on a magnetic nanoparticles as a new heterogeneous catalyst. The as‐prepared catalyst was characterized by FT‐IR, TEM, FESEM, VSM, TGA and XRD. This catalyst indicated significant advantages, such as excellent yields, shorter reaction time, reusability of the catalyst and easy workup process. 相似文献
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Magnetic‐based picolinaldehyde–melamine copper complex for the one‐pot synthesis of hexahydroquinolines via Hantzsch four‐component reactions
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A picolinaldehyde–melamine copper complex was loaded on a magnetic Fe3O4 core, so that it contained 0.33 mmol of Cu per gram, and was used as an efficient catalyst. The as‐synthesized catalyst was characterized using various techniques, including Fourier transform infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and thermogravimetric analysis. The catalyst was used to activate the raw materials in the synthesis of hexahydroquinoline derivatives in one‐pot four‐component reactions. Low reaction time (minutes versus half an hour), solvent‐free condition and magnetically separable catalyst are some salient features of the developed catalyst. Also, the optimum amount of catalyst and temperature were determined as 0.07 g and 87.6 °C, respectively, which were obtained using response surface methodology and optimization techniques. 相似文献
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Mizoroki–Heck and Suzuki–Miyaura reactions mediated by poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐stabilized magnetically separable palladium catalyst
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The purpose of this work was to synthesize and characterize a new magnetic polymer nanosphere‐supported palladium(II) acetate catalyst for reactions requiring harsh conditions. In this regard, an air‐stable, moisture‐stable and highly efficient heterogenized palladium was synthesized by the coordination of palladium(II) acetate with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐grafted modified magnetic nanoparticles with a core–shell structure. The structure of the newly developed catalyst was characterized using various techniques. The catalytic activity of the resultant nano‐organometallic catalyst was evaluated in Mizoroki–Heck and Suzuki–Miyaura reactions to afford the corresponding coupling products in good to excellent yields. High selectivity as well as outstanding turnover number (14 143, 4900) and turnover frequency (28 296, 7424) values were recorded for the catalyst in Suzuki–Miyaura and Mizoroki–Heck reactions, respectively. Magnetic separation and recycling of the catalyst for at least six runs became possible without any significant loss of efficiency or any detectable palladium leaching. 相似文献
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A template-free seeded short-time in situ hydrothermal treatment was carried out in a brass autoclave to synthesize crystalline mordenite (MOR) membranes on alumina-silicate disk supports with micro-scale pores. According to XRD analysis, MOR was the only zeolitic material present in the membrane layers on the supports. SEM examination of the membranes showed three different layers of the membrane thickness: (i) support sub-layer, (ii) mix penetrated mid-layer, the MOR crystals filling the pores among the support (about 4–5 μm), and (iii) MOR top-layer (about 4–5 μm). The crystalline bonds between MOR crystals of the membrane top-layer and the crystals of the support were clearly observed within the mid-layer. The continuous top-layer of zeolitic membrane was formed by many large and well-shaped crystals. The seeding treatment significantly enhanced the formation of MOR crystals onto the surface of the supports. EDAX analysis showed a Si/Al ratio of 6.8 for the MOR layer of the membrane. Due to their hydrophilic natures, the polycrystalline MOR membranes were found to be selective for continuous dehydration of different EtOH–water mixtures through an adsorption–diffusion–desorption mechanism. Both total permeation flux and separation factor of the membrane were found to increase by increasing temperature and water concentration of feed. The continuity and high crystallinity of the membrane top-layer led to the fairly high dehydration of EtOH. It was found that there was no pinhole within the layer and the morphology of the membrane was almost defect-free. 相似文献
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Sajjad Rashidi Farshad Farzin Mehdi Shanbedi Masoud Rahimipanah Maryam Savari 《Journal of Dispersion Science and Technology》2016,37(9):1277-1286
In order to enhance the thermal properties of turbine oil (TO), three different nanoparticles (CuO, Al2O3, and TiO2) are loaded into the TO. To measure the thermal performance of nanoparticle-based TO nanofluids at laminar flow and under constant heat flux boundary conditions, an experimental setup was applied. The obtained data clearly demonstrate the positive effect of all nanoparticles on the heat transfer rate of TO. As the most important factor, the heat transfer coefficient of the abovementioned two-phase systems is increased upon increasing both the volume concentration and the flow rate. An adaptive neuro-fuzzy inference system (ANFIS) is applied for modeling the effect of critical parameters on the heat transfer coefficient of nanoparticle-TO based nanofluids numerically. The results are compared with experimental ones for training and test data. The results suggest that the developed model is valid enough and promising for predicting the extant of the heat transfer coefficient. R2 and MSE values for all data were 0.990208751 and 108.1150734, respectively. Based on the results, it is obvious that our proposed modeling by ANFIS is efficient and valid, which can be expanded for more general states. 相似文献