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微波辐照下(Bi_2O_3)_(0.8)(La_2O_3)_(0.2)固熔体对甲烷氧化偶联的催化行为陈长林,洪品杰,戴树珊,阚家德(云南大学化学系,昆明,650091)关键词微波,甲烷氧化偶联,(Bi_2O_3)_(0.8)(La_2O_3)_(0.2)甲烷氧化... 相似文献
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《Arabian Journal of Chemistry》2014,7(1):79-86
Microwave-assisted photocatalytic degradation of dyes is one of the emerging technologies for waste water remediation. Microwave effectively accelerates photocatalytic degradation, when microwave electrodeless lamp (MEL) substitutes traditional UV lamp as light source. This setup can be extremely simplified if MEL and photocatalyst can be replaced by a catalyst which can work under microwave irradiation in the absence of any light source. The present work reports for the first time degradation of acid orange 7 (AO) under microwave irradiation using polyaniline (PANI) as catalyst in the absence of any UV lamp as light source. The degradation/decolourization was carried out in neutral acidic and basic media and was monitored spectrophotometrically to evaluate the ability of microwave irradiation to degrade AO. Microwave irradiation showed excellent performance as it completely decolourizes AO dye solution in 10 min. With the advantages of low cost and rapid processing, this novel catalyst is expected to gain promising application in the treatment of various dyestuff wastewaters on a large scale. 相似文献
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一种新的催化方法:微波辐射-酶耦合成催化有机合成 总被引:19,自引:2,他引:19
微波辐射和酶催化是现代有机合成化学中两种强有力的催化手段。目前一种新 的研究动向是将两者结合起来用于催化有机合成反应,这种新型催化方法可以被称 作微波辐射-酶耦合催化(MIECC)。由MIECC方法催化的有机合成反应可以被分为 湿法和干法两大类型。介绍了这一新型耦合催化方法的研究进展以及一些典型 MIECC反应。对MIECC反应中可能存在的耦合催化机理,即微波在生物催化体系中的 “非热效应“进行了初步理论探讨,同时展望了这种新的耦合催化方法的前景。 相似文献
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Langa F de la Cruz P de la Hoz A Espildora E Cossio FP Lecea B 《The Journal of organic chemistry》2000,65(8):2499-2507
The regioselectivity of the cycloaddition of N-methylazomethine ylide to C70 can be modified by using microwave irradiation as the source of energy. Under microwave irradiation and by choosing the appropriate solvent and irradiation power, the 5-6 isomer is the major product, a situation that is in contrast to conventional heating where the 1-2 isomer predominates. Moreover, isomer 7-21, which represents 13% of monoadducts under classical heating, is not formed under microwave irradiation and with ODCB as solvent. Theoretical calculations predict an asynchronous mechanism and suggest that the modification of the regiochemical outcome is related to the relative energies and hardnesses of the transition structures involved. 相似文献
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A polymeric system capable of delivering 5-fluorouracil (5-FU) at increased rates on demand by external microwave irradiation was developed. Sustained-release systems were made by incorporating 5-FU into an ethylene-vinyl alcohol copolymer. When exposed to release medium, the delivery systems released the drug slowly and continuously. Upon exposure to microwave irradiation, the drug was released at a much higher rate. Release rates returned to base line levels when the microwave irradiation was discontinued. This study demonstrated that release rates of 5-FU from a polymer matrix can be increased at desired times by external microwave irradiation. 相似文献
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通过微波对溴化银乳剂胶片的照射可以达到使感光胶片增感的目的.研究表明,短时间的微波照射就可以使溴化银胶片的感光度有明显提高,而一定时间的微波照射后,感光胶片的感光度并不象外加热方式那样出现衰退的现象.增加硫金比,微波照射后,感光度增加较多,说明感光中心与[Ag2S·Ag]+有关.并且,微波照射产生的增感效应有一定的时效性. 相似文献
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二酰亚胺是一个很有用的官能团, 它广泛存在于天然产物和有药物活性的分子中. 通过微波辐射条件合成它吸引了很多化学家的注意. 极性反应物可以吸收微波辐射, 化学家将微波应用于一些化学反应中. N-烷基酰胺(NH邻位有一个亚甲基CH2)和N上没有取代的内酰胺可以被过氧化物和过渡金属盐氧化成二酰亚胺. 报道了在乙酸乙酯中过氧叔丁醇和乙酰丙酮锰(III)在微波条件(90 W, 5 min)下, 酰胺迅速、高选择性地、高产率地转变为二酰亚胺的方法. 相似文献
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《大分子反应工程》2018,12(1)
A comprehensive kinetic model based on the method of moments is developed for understanding the kinetics of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) under microwave irradiation. Both the experimental data and the simulation results show that the polymerization under microwave irradiation is much faster than the thermal polymerization. Simulation results indicate that the acceleration of polymerization can be attributed to the increase of propagation rate coefficient and the radical generation by microwave irradiation. Kinetic behaviors, such as the effect of catalyst concentration and initial initiator, are investigated in detail. Results show that the catalyst concentration has negligible influence on polymerization rate while the initiator concentration can affect both the molecular weight and the reaction rate. In conclusion, this work thoroughly investigates the kinetic mechanism of ARGET ATRP under microwave irradiation, providing both theoretic and experimental supports to improve the product property of polymer materials. 相似文献
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Anikó Szepes Anke Fiebig J. Ulrich Piroska Szabó-Révész 《Journal of Thermal Analysis and Calorimetry》2007,89(3):757-760
The aim of this work was to investigate the influence of different levels of microwave irradiation on the structure and particle
size characteristics of α-lactose monohydrate. The structural study of the samples was carried out by XRD, the presence of
lactose polymorphs in the test samples was determined by DSC and the particle size distribution was measured by laser diffraction.
The samples subjected to microwave irradiation retained their original X-ray patterns. No significant differences in thermal
transition characteristics and particle size were observed. Hence, neither the occurrence of crystalline-amorphous transition
resulted by microwave irradiation nor the presence of lactose polymorphs in the test samples can be assumed. The unmodified
properties can be attributed to the fact that the water of crystallization is very difficult to remove from the crystal structure
and is not free to move during microwave treatment, which results in stability to microwaves. 相似文献
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Ipsita RoyMunishwar N. Gupta 《Tetrahedron》2003,59(29):5431-5436
The non-thermal effects of microwave irradiation on enzyme-catalyzed reactions have been evaluated by keeping the reaction temperature constant during irradiation. Subtilisin-catalyzed transesterification and α-chymotrypsin-catalyzed esterification have been carried out in six solvents of differing polarities and at three different temperatures. In all cases, microwave irradiation was found to increase the initial reaction rates by 2.1-4.7 times at all hydration levels. It is also shown that microwave irradiation can be used in conjunction with other strategies (like pH tuning and salt activation) for enhancing initial reaction rates. 相似文献
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Esterification-chlorination of glycerol provides chlorohydrin esters in high yields. A ratio of reagents close to equivalence can be used, so that atom economy of the reaction is optimized. The reaction can be carried out using either classical or microwave heating, and no solvent is required. 2-Chloro-1-(chloromethyl)ethyl esters can be obtained in high regioisomeric relationship when either low or moderate temperature is used. In contrast, microwave irradiation allows the use of higher reaction temperatures that render mixtures of both regioisomers in variable relationships. Kinetic control of the process is proposed for classical heating, and experimental results are analyzed with the aid of ab initio calculated values. Non-thermal phenomena can be used to explain the high efficiency of microwave irradiation at low temperature. 相似文献
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Sterilization system using microwave and UV light 总被引:2,自引:0,他引:2
Shiro Iwaguch Kentaro Matsumura Yoshikazu Tokuoka Shiro Wakui Norimichi Kawashima 《Colloids and surfaces. B, Biointerfaces》2002,25(4):458-304
We constructed a novel microwave–UV light sterilization system and investigated its sterilization effect. This sterilization system can emit UV light by irradiation of microwave without other power. When irradiating UV light with and/or without microwave on aqueous DMPO solution, active oxygen species such as hydroxyl radical or superoxide were generated in the solution. The amount of active oxygen species generated by irradiation of microwave and UV light was larger than that by irradiation of UV light alone. This would be due to the promotion of emission of UV light photons by microwave and UV light irradiation. Moreover, microwave–UV light sterilization was highly effective to sterilize microorganisms. The generation of active oxygen species would play an important role in sterilization of the sterilization system. 相似文献
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Jhung SH Jin T Hwang YK Chang JS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(16):4410-4417
Microporous materials, such as silicalite-1 and VSB-5 molecular sieves, have been synthesized by both microwave irradiation (MW) and conventional electric heating (CE). The accelerated syntheses by microwave irradiation can be quantitatively investigated by various heating modes conducted in two steps such as MW-MW, MW-CE, CE-MW, and CE-CE (in the order of nucleation-crystal growth). In the case of synthesis by MW-CE or CE-MW, the heating modes were changed for the second step just after the appearance of X-ray diffraction peaks in the first step. We have quantitatively demonstrated that the microwave irradiation accelerates not only the nucleation but also crystal growth. However, the contribution to decrease the synthesis time by microwave irradiation is larger in the nucleation stage than in the step of crystal growth. The crystal size increases in the order of MW-MW相似文献
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Lin SS Wu CH Sun MC Sun CM Ho YP 《Journal of the American Society for Mass Spectrometry》2005,16(4):581-588
The work describes the accelerated enzymatic digestion of several proteins in various solvent systems under microwave irradiation. The tryptic fragments of the proteins were analyzed by matrix-assisted laser desorption/ionization mass spectrometry. Under the influence of rapid microwave heating, these enzymatic reactions can proceed in a solvent such as chloroform, which, under traditional digestion conditions, renders the enzyme inactive. The digestion efficiencies and sequence coverages were increased when the trypsin digestions occurred in acetonitrile-, methanol- and chloroform-containing solutions that were heated under microwave irradiation for 10 min using a commercial microwave applicator. The percentage of the protein digested under microwave irradiation increased with the relative acetonitrile content, but decreased as the methanol content was increased. These observations suggest that acetonitrile does not deactivate the enzyme during the irradiation period; in contrast, methanol does deactivate it. In all cases, the digestion efficiencies under microwave irradiation exceed those under conventional conditions. 相似文献
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The reaction of 2-pyridone with benzyl bromide in the absence of base and under solvent-free conditions has been studied experimentally and by computational methods. This reaction was one of the first reported examples in which modification of selectivity under microwave irradiation was observed. C- and/or N-alkylations were obtained depending on the benzyl halide and the heating system. N-Alkylation through mechanism A (SN2 mechanism) is kinetically favoured while C-alkylation through an SN1-type mechanism is thermodynamically favoured and is observed under microwave irradiation. Two SN1-type mechanisms (mechanisms B and C) have been calculated, mechanism C being a kind of SNi. The influence of the pyridone/benzyl bromide ratio was studied. A second molecule of pyridone stabilizes the transition state and assists the leaving of the bromide ion. The occurrence of C-alkylation under microwave irradiation is explained by the predominance of the thermodynamic control in these conditions. Under microwave irradiation N-alkylation through an SN1-type mechanism (mechanism C) can also occur. The dependence of the outcome of N-alkylation on the benzyl bromide ratio has been explained by a shift in the mechanism from SN2 to SN1 under microwave irradiation. Computational calculations have shown to be a useful tool for determination of the origin of the selectivity under microwave irradiation. 相似文献
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The effect of traveling microwave irradiation on the crystallinities of CdS nanoparticles and Bi2S3 nanorods was studied. Results showed that as compared with stationary microwave irradiation the crystallinities and the crystal growth of sulfide nanoparticles were improved. Traveling microwave irradiation can supply narrower frequency distribution and stronger power density of irradiation, CdS nanoparticles and Bi2S3 nanorods obtained are better in crystallinities and larger in size than under stationary microwave irradiation. 相似文献
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Hemetsberger-Knittel indole synthesis can be carried out under microwave activation. The optimum reaction conditions were found by using different solvents and by varying irradiation times and temperature. After 10 min of microwave irradiation, high conversion into the corresponding indole products was achieved without formation of any side products. 相似文献