微波场中T型分子筛的合成及晶化研究

研究了微波场中T型分子筛的结晶过程。考察了微波加热体系中合成参数如合成时间、溶胶组成、反应压力和模板剂用量对分子筛晶化的影响。微波加热的主要优点是减少合成时间,无模板剂的溶胶在普通加热条件下的晶化时间需要120 h,而在微波场中则仅需要20～25 h。另一方面,由于微波的快速加热特性促进了稳定相钙十字沸石的生成,从而减小了次稳定相T型分子筛的结晶区间。在未添加模板剂条件时,100 ℃下微波水热合成T型分子筛的结晶区间为：20≤n_SiO2/n_Al2O3≤22和0.31≤ n_M2O/n_SiO2≤0.33(其中M₂O=Na₂O+K₂O, n_Na/n_K=3和n_M2O/n_SiO2=11.70)。在普通加热和微波加热合成体系中,添加模板剂均能扩大结晶区间,同时还可以进一步减少合成时间。     

Template-Free Synthesis of AlPO 4 -H1 by Microwave Heating

Microwave heating enhanced the crystallization of aluminophosphate gels, and AlPO 4 -H1 was successfully obtained without using organic template reagents in a short reaction time. The use of amorphous aluminum hydroxide as an aluminum source and the addition of hydrochloric acid were found to be essentially important to obtain AlPO 4 -H1 as a single phase. Nitrogen and water adsorption properties were studied by measuring the adsorption isotherms.     

Synthesis of Compact NaA Zeolite Membrane by Microwave Heating Method

A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 rim. The gas H2/N2 mixture separating results indicated that the mixture selectivity increased with increasing of synthesis times. In addition, selectivity of the three-step synthesis was higher than the value(3.74) expected from Kundsen diffusion.     

Evolution of Er^3＋ Distribution in the Oxyfluoride Glass Ceramics with Heating

The distribution characteristics of Er3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er3+ in LaF3 nanocrystals increases with prolonging of heating time. The anomalous phenomena of Er3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results.     

微波法制备掺碳LiFePO4正极材料

Cathode material LiFePO₄ of lithium-ion battery was synthesized by microwave heating. The “carbon-included” LiFePO₄ with improved conductivity was synthesized by the addition of graphite. And the influence of microwave-heating time on structure, morphology and charge/discharge performance of the products was discussed. The results of XRD, SEM, XPS, CV and charge/discharge testing measurements showed that the LiFePO₄ product after 9 min in microwave oven had more advantages than other products.     

Highly Efficient Synthesis of Tricyclic Perimidines under Microwave Heating

A new and efficient access to (Z)‐N‐(2‐argio‐1‐(1H‐perimidin‐2‐yl)vinyl)benzamide derivatives from readily available substrates in HOAc is described with aid of microwave irradiation. The results of our study provide a simple, straightforward synthetic route to these interesting classes of 2‐substituted perimidines analogs in excellent yields.     

Fast Synthesis of Submicron Zeolite Y Using Microwave Heating

Kinetics and Catalysis - Submicron zeolite has become the focus of research because of its high thermal stability, high catalytic activity, and uniform size. A rapid method for synthesizing...     

Microwave Heating in Synthesis: Preparation of Allyldiphenylphosphine Oxide

A new one-pot synthesis of allyldiphenyl-phosphine oxide has been developed using a tandem Sn2′ / Michaelis-Arbuzov sequence. The application of microwave heating lowers the reaction time significantly.     

Changing Perspectives on the Strategic Use of Microwave Heating in Organic Synthesis

This Personal Account describes collaborative investigations into apocryphal microwave effects in organic chemistry. Focused research on microwave‐assisted organic synthesis has been fraught with confusion, controversy, and misinformation. Microwave heating is an undoubtedly useful tactic for organic synthesis, but whether or not it can offer strategic advantages remains an open question in the minds of many people. (Ironically, those who do not consider it an open question are split as to whether it has been resolved affirmatively or negatively.) Our research in this area is guided by the hypothesis that microwave heating can alter reaction kinetics in ways distinct from what is observable under conventional heating. Here we provide a succinct record of the origins of our interests, our initial queries and associated controversies, and recent efforts to identify, quantify, and begin to leverage selective microwave heating for strategic advantage in organic synthesis.     

微波场对SrTiO3化学合成中热过程的影响

在分析微波场中 SrTiO3化学合成体系与电磁场相互作用的基础上 ,探讨合成体系在微波场中的加热机制和影响升温的主要因素（如合成体系的介电性质、保温材料的结构、生坯的致密度等） .结果表明 ,TiO2和 SrCO3在低温阶段对体系的升温速率的贡献相接近 ;高温阶段体系升温主要是 TiO2的贡献 ,同时产物对升温有较大的影响 .微波合成与常规合成在加热方式上的明显不同,对合成过程、合成时间等影响较大 .     

The Synthesis, Characterization and Microwave Properties of ZnCo-Substituted W-Type Barium Hexaferrite, from a Sol-Gel Precursor

The preparation of BaZn_{2 – x} Co _x Fe₁₆O₂₇ W-type hexaferrites powders by a citrate sol-gel method has been investigated. The samples were characterized by TG-DSC, X-ray diffraction (XRD), scanning electron microscopy (SEM). The complex dielectric constant and complex permeability of hexaferrite-paraffin wax composites were measured by the transmission/reflection coaxial line method in the range from 50 MHz to 3 GHz. The dependence of complex dielectric constant and permeability on annealing temperature, composition and measuring frequency was presented.     

微波加热法快速合成T型分子筛

由于具有高的水热稳定性和优良的孔道结构．T型分子筛已成为一种高选择性的催化剂．在低碳化合物的催化和重整等方面有较多的应用。近年来．报道采用晶种法在无机多孔陶瓷支撑体上制备的T型分子筛膜．在脱除有机物／水混合物中的水时．表现出优异的渗透汽化分离性能。然而，提高T型分子筛膜的致密性和生长速率仍是亟待解决的问题。T型分子筛的合成研究较少．制备过程均采用普通加热（Conventional Heating．CH）法。在无模板剂的条件下．T型分子筛的结晶区间较窄，结晶速率慢．合成时间通常需要6d以上。     

Palladium-Catalyzed Synthesis of Symmetrical Biaryls Under Microwave Irradiation and Conventional Heating

The activity of the [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(µ-Br)]₂ complex was investigated in the synthesis of symmetrical biaryls under both conventional and microwave irradiation conditions, and their results were compared. This complex is efficient, stable, and not sensitive to air or moisture and is a catalyst for the homo-coupling reaction of aryl iodides, bromides, and even chlorides. The products were produced in excellent yields in short reaction times using a catalytic amount of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)(µ-Br)]₂ complex in N-methylpyrolidine (NMP) at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave better yields in shorter reaction times.     

An Efficient and Environmentally Friendly Method for the Synthesis of Cellulose Carbamate by Microwave Heating

An efficient, solvent‐free, and catalyst‐free microwave synthesis of cellulose carbamate from a mixture of native cellulose and urea is reported. The structure of the samples are characterized by elemental analysis, FT‐IR spectroscopy, X‐ray diffraction, and NMR spectrometry. Cellulose carbamates with a nitrogen content of 0.651–2.427% are obtained by microwave heating at 255 W for 2–5 min. With the introduction of carbamate groups, the hydrogen bonding and crystalline structure of the native cellulose are partially destroyed. The products retain the cellulose I crystalline form of the native cellulose, and display good solubility in NaOH solutions.

     

微波加热法测定灯盏花素的水分

药物中水分的测定一般是根据中国药典规定,在105℃控温烘箱中加热5h,称量至恒重,然后计算失去的水分[1].目前微波加热在化学领域已得到了广泛的应用,用微波加热对药物中水分的测定,已有报道[2,3].但是用微波加热测定灯盏花素中水分,与药典方法相比,微波法具有操作简便,快速,低耗能的优点.本法用微波加热法测定灯盏花素的水分含量,并与药典法进行比较,结果满意.     

[AEIM]Cl的合成及微波溶解微晶纤维素

以氯丙烯和N-乙基咪唑为原料合成了离子液体氯化1-烯丙基-3-乙基-咪唑盐([AEIM]Cl),利用FT-IR和¹HNMR对其化学结构进行了表征。采用微波加热法溶解微晶纤维素(MCC),考察 [AEIM]Cl对纤维素的溶解性能。研究了NaOH、微波和高压等3种预处理方式对微晶纤维素的相对结晶度、聚合度及溶解率的影响。利用FT-IR、XRD、TGA和SEM分别对溶解后得到的再生纤维素的化学结构、晶型变化、热稳定性及表观形貌进行测试与分析。结果表明,合成的离子液体是目标产物,对微晶纤维素表现出很好的溶解能力,且高温高压条件下15％的NaOH水溶液对微晶纤维素处理后,得到的纤维素相对结晶度最小,聚合度最低,溶解率最高。溶解过程中纤维素没有发生衍生化反应,溶解后得到的再生纤维素的相对结晶度和微晶尺寸变小,热稳定性降低。