微波诱导甲烷在活性炭/碳化硅上直接转化制C2烃

 在高功率脉冲微波辐照下甲烷可在常压条件下在活性炭/碳化硅和活性炭碳化硅等 三种催化剂上直接转化为C2烃。研究结果表明,当使用合适的微波作用条件时,微波加热与微波 等离子协同作用可使甲烷在多孔碳化硅担载的活性炭催化剂上以很高的转化率和选择性直接转化为乙炔,除单独的微波加热诱导作用和微波等离子催化作用外,转移反应机制可能是微波加热与微波等离子交互作用的具体表现形式,对促进甲烷向乙炔直接转化起了重要作用。     

Microwave-assisted asymmetric organocatalysis. A probe for nonthermal microwave effects and the concept of simultaneous cooling

A series of five known asymmetric organocatalytic reactions was re-evaluated at elevated temperatures applying both microwave dielectric heating and conventional thermal heating in order to probe the existence of specific or nonthermal microwave effects. All transformations were conducted in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using fiber-optic probes. In addition, the concept of simultaneous external cooling while irradiating with microwave power was also applied in all of the studied cases. This method allows a higher level of microwave power to be administered to the reaction mixture and, therefore, enhances any potential microwave effects while continuously removing heat. For all of the five studied (S)-proline-catalyzed asymmetric Mannich- and aldol-type reactions, the observed rate enhancements were a consequence of the increased temperatures attained by microwave dielectric heating and were not related to the presence of the microwave field. In all cases, in contrast to previous literature reports, the results obtained either with microwave irradiation or with microwave irradiation with simultaneous cooling could be reproduced by conventional heating at the same reaction temperature and time in an oil bath. No evidence for specific or nonthermal microwave effects was obtained.     

离子液体-非极性溶剂微波提取法在人参化学成分研究中的应用

以离子液体作为微波吸收介质建立了离子液体-非极性溶剂微波提取法,对人参中的化学成分进行了提取,并将该法与固体微波吸收介质-非极性溶剂微波提取法、极性溶剂微波提取法以及混合溶剂微波提取法进行了对比.结果表明,极性溶剂提取的主要化学成分为极性化合物,而固体微波吸收介质-非极性溶剂微波提取法与离子液体-非极性溶剂微波提取法相比,提取所得的化学成分并无明显差别,说明离子液体是一种较好的微波吸收介质和能量传递材料.所建立的方法具有提取时间短、操作简单及绿色环保等优点,且对后期分析无明显影响,是快速提取化学成分的理想方法.     

Investigating the existence of nonthermal/specific microwave effects using silicon carbide heating elements as power modulators

The use of passive heating elements made out of chemically inert sintered silicon carbide (SiC) allows microwave transparent or poorly absorbing reaction mixtures to be heated under microwave conditions. The cylindrical heating inserts efficiently absorb microwave energy and subsequently transfer the generated thermal energy via conduction phenomena to the reaction mixture. In the case of low to medium microwave absorbing reaction mixtures, the addition of SiC heating elements results in significant reductions (30-70%) in the required microwave power as compared to experiments performed without heating element at the same temperature. The method has been used to probe the influence of microwave power (electromagnetic field strength) on chemical reactions. Six diverse types of chemical transformations were performed in the presence or absence of a SiC heating element at the same reaction temperature but at different microwave power levels. In all six cases, the measured conversions/yields were similar regardless of whether a heating element was used or not. The applied microwave power had no influence on the reaction rate, and only the attained temperature governed the outcome of a specific chemical process under microwave conditions.     

Microwave synthesis of zeolite membranes: A review

Significant progress has been achieved in the last years on microwave synthesis of zeolite membranes. In many cases, microwave synthesis has proven to remarkably reduce the synthesis time. In addition, microwave synthesis could also result in different membrane morphology, orientation, composition, and thus the different permeation characteristics as compared with those synthesized by conventional heating. This review attempts to summarize the obtained progress in microwave synthesis of zeolite membranes. Some topics are discussed, including: (1) case study of microwave synthesis of zeolite membranes, e.g. LTA, MFI, AFI, and other types of zeolite membranes; (2) differences between conventional and microwave synthesis; (3) formation mechanism and the so called “specific microwave effect” in the case of microwave synthesis of zeolite membranes; (4) scaling-up of zeolite membrane production by employing microwave heating. The latter three topics are mainly focused on LTA type zeolite membranes. Concluding remarks and future perspective are also suggested in the end.     

微波辐射-酶耦合催化(MIECC)反应

将微波辐射用于非水相酶催化可以获得很多有别于常规加热下的反应结果。本文讨论了微波的非热效应在酶促反应中的表现,探讨了微波辐射对酶的结构、构象、活性及酶催化反应动力学的影响,以及微波辐射-酶耦合催化对反应的对映选择性、底物专一性、前手性选择性和区域选择性的影响。在大多数场合,适当的微波辐射不会损伤酶活而且可以提高反应速率,而对酶特异性的影响则不一而论。     

微波等离子体光谱技术的发展(二)

微波等离子体光源是一类重要的有较强激发能力的原子发射光谱光源,主要包括微波感生等离子体光源,电容耦合微波等离子体光源及微波等离子体炬光源。本文是微波等离子体光谱技术发展的第二部分,主要介绍了电容耦合微波等离子体光源及微波等离子体炬光源的结构原理和性能。并对它们的技术特点和进展进行评述。     

Microwave Flow: A Perspective on Reactor and Microwave Configurations and the Emergence of Tunable Single‐Mode Heating Toward Large‐Scale Applications

Microwave heating in chemical reactions was first reported in 1986. There have since been many reports employing microwave heating in organic chemistry, where microwave heating has afforded higher yields of products in shorter time periods. However, such reactions are challenging to scale in batch due to the limited penetration depth of microwaves as well as the wave propagation dependence on cavity size. Continuous flow has addressed both these issues, enabling scalability of microwave processes. As such, a host of reports employing microwave flow chemistry have emerged, employing various microwave heating and reactor configurations in the context of either custom‐built or commercial apparatus. The focus of this review is to present the benefits of microwave heating in the context of continuous flow and to characterize the different types of microwave flow apparatus by their design (oscillator, cavity type and reactor vessel). We advocate the adoption of tunable, solid‐state oscillator single‐mode microwave flow reactors which are more versatile heaters, impart better process control and energy efficiency toward laboratory and larger‐scale synthetic chemistry applications.     

用于气相色谱的微波等离子体原子发射光谱检测器的发展

分别介绍和评价了用于气相色谱的微波诱导等离子体、电容耦合微波等离子体和微波等离子体炬等3种微波等离子体原子发射光谱检测器的发展、应用以及局限性。对用于气相色谱的微波等离子体原子发射光谱检测器的发展作了展望。     

控温下微波反应装置用于壳聚糖羧甲基化反应

微波加热近年来被广泛应用在化学合成中。本文报道了通过外接恒温槽的恒温循环水的方法，实现了微波反应系统的恒温控制。将该装置应用于壳聚糖的羧甲基化反应，采用水溶剂代替传统加热方法的异丙醇溶剂，制备出取代度达0．85的羧甲基壳聚糖。     

有机溶剂和二元体系溶液在9590兆赫的微波吸收分析应用

在９５９０兆赫和室温下，研究了一些有机溶剂和二元体系溶液的微波吸收。首次使用诱导效应指数来表达同系化合物的分子结构与其微波吸收之间的关系。研究了一些缔合和非缔合二元体系溶液的微波吸收，并提出了一个计算二元非缔合体系微波吸收的经验公式。此外，建立了利用微波测定白酒中乙醇含量的方法。     

Microwave‐Assisted Polymer Synthesis: State‐of‐the‐Art and Future Perspectives

Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step‐growth and ring‐opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave‐assisted and conventional heating as well as the “microwave effects”.

Results of search on number of publications on microwave‐assisted polymerizations, sorted by year.     

微波辐照下（Bi_2O_3）_（0．8）（La_2O_3）_（0．2）固熔体对甲

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...     

Engineering and scale-up considerations for microwave induced reactions

Researchers in the area of microwave induced reactions have used many types of hardware, from modified kitchen microwave ovens to commercial generators with waveguide applicators. While in many instances the engineering performance of the hardware is not important in laboratory scale, there are also performance-sensitive experiments. When an experiment becomes successful enough to make one think of scale-ups, then microwave engineering considerations become critical. In this paper figures of merit of microwave systems and applicator configurations are discussed. Prospects for scale-up of microwave chemical reactions are considered by citing recent development in the commercial microwave industry, as well as off-the-shelf equipment. Various large scale applicator configurations are also compared for their possible suitability for inducing reactions.     

Practical and Scalable Organic Reactions with Flow Microwave Apparatus

Microwave irradiation has been used for accelerating organic reactions as a heating method and has been proven to be useful in laboratory scale organic synthesis. The major drawback of microwave chemistry is the difficulty in scaling up, mainly because of the low penetration depth of microwaves. The combination of microwave chemistry and flow chemistry is considered to overcome the problem in scaling up of microwave‐assisted organic reactions, and some flow microwave systems have been developed in both academic and industrial communities. In this context, we have demonstrated the scale‐up of fundamental organic reactions using a novel flow microwave system developed by the academic‐industrial alliance between the University of Shizuoka, Advanced Industrial Science and Technology, and SAIDA FDS. In this Personal Account, we summarize the recent progress of our scalable microwave‐assisted continuous synthesis using the SAIDA flow microwave apparatus.     

Microwave drying of granules containing a moisture-sensitive drug: a promising alternative to fluid bed and hot air oven drying

The impact of microwave drying and binders (copolyvidone and povidone) on the degradation of acetylsalicylic acid (ASA) and physical properties of granules were compared with conventional drying methods. Moist granules containing ASA were prepared using a high shear granulator and dried with hot air oven, fluid bed or microwave (static or dynamic bed) dryers. Percent ASA degradation, size and size distribution, friability and flow properties of the granules were determined. Granules dried with the dynamic bed microwave dryer showed the least amount of ASA degradation, followed by fluid bed dryer, static bed microwave oven and hot air oven. The use of microwave drying with a static granular bed adversely affected ASA degradation and drying capability. Dynamic bed microwave dryer had the highest drying capability followed by fluid bed, static bed microwave dryer and conventional hot air oven. The intensity of microwave did not affect ASA degradation, size distribution, friability and flow properties of the granules. Mixing/agitating of granules during drying affected the granular physical properties studied. Copolyvidone resulted in lower amount of granular residual moisture content and ASA degradation on storage than povidone, especially for static bed microwave drying. In conclusion, microwave drying technology has been shown to be a promising alternative for drying granules containing a moisture-sensitive drug.     

微波用于破乳的研究

原油自井下开采出来要穿过窄隙,与水和气混在一起。油中含有沥青质、石油环烷酸;水中含有各种矿物质,都是天然的乳化剂。因此,大量原油将以乳状液的形式被开采出来,大多数为油包水型(W/O),开发到中后期还会出现油包水、水又包油(O/W/O)型。这种原油无法进一步加工,于是,原油脱水成为采油和集输中一个普遍关注的问题。原油脱水国外较多使用化学破乳法,我国各油田多使用电—化学破乳。电—化学脱水法对高含水原油的适应性差,还需增设预脱水工序。而纯化学脱水,试剂昂贵,生产费用较高。因而,近年来人们开始探索将超声技术、微波技术用于破乳。本文考察了微波破乳效果及其机制,并与常规法进行比较。     

Stability improvement of immobilized Candida antarctica lipase B in an organic medium under microwave radiation

The influence of microwave heating on the stability of immobilized Candida antarctica lipase B was studied at 100 degrees in an organic medium. The microwave radiation was carried out before enzymatic reaction (storage conditions) or during the enzymatic catalysis (use conditions). In both cases, enzymatic stability was higher under microwave heating than under conventional thermal heating, in strictly identical operating conditions. Furthermore, the gain of enzymatic stability under microwave heating appears to be higher in a more polar solvent, which interacts strongly with the microwave field. Our results suggest that microwave radiation has an effect, not related to temperature, on the process of enzymatic inactivation.     

微波技术在催化剂制备中的应用

微波作为一种独特的加热手段在化学领域已得到广泛应用。本文综述了微波技术在催化剂的合成、活性组分的负载等方面的研究应用,重点探讨了在分子筛催化剂的合成中微波技术所表现出的优越性,对微波合成催化剂的作用机理及影响因素作了评述,并展望了微波技术在催化领域的发展前景。     

Microwave synthesis of zeolites. 2. Effect of vessel size, precursor volume, and irradiation method

The enhancement of synthesis reactions under microwave heating is dependent on many complex factors. We investigated the importance of several reaction engineering parameters relevant to microwave synthesis. Of interest to this investigation were the reaction vessel size, volume of precursor reacted, microwave power delivery, and microwave cavity design. The syntheses of NaY zeolite and beta-zeolite were carried out under a number of varying conditions to determine the influence of these parameters on the nucleation rate, the crystallization rate, and the particle size and morphology. The rates of NaY and beta-zeolite nucleation and crystallization were more rapid in the multimode CEM MARS-5 oven compared to the more uniform field CEM Discover. The faster synthesis rate in the MARS-5 may be the result of the multimode microwave electric field distribution. Slower rates of NaY and beta-zeolite formation observed in the Discover and a circular waveguide may be the result of a more uniform microwave electric field distribution. Changes in reaction vessel size and precursor volume during the microwave synthesis of beta- and NaY zeolite were found to influence the rate of zeolite formation. These results indicate that reactor geometry needs to be considered in the design of systems used for microwave synthesis. Comparative synthesis reactions were carried out with conventional heating, and microwave heating was shown to be up to over an order of magnitude faster for most of these syntheses.