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J. A. F. F. Rocco J. E. S. Lima A. G. Frutuoso K. Iha M. Ionashiro J. R. Matos M. E. V. Suárez-Iha 《Journal of Thermal Analysis and Calorimetry》2004,75(2):551-557
The thermal decomposition of ammonium perchlorate (AP)/hydroxyl-terminated-polybutadiene (HTPB), the AP/HTPB solid propellant,
was studied at different heating rates in dynamic nitrogen atmosphere. The exothermic reaction kinetics was studied by differential
scanning calorimetry (DSC) in non-isothermal conditions. The Arrhenius parameters were estimated according to the Ozawa method.
The calculated activation energy was 134.5 kJ mol-1, the pre-exponential factor, A, was 2.04×1010 min-1 and the reaction order for the global composite decomposition was estimated in 0.7 by the kinetic Shimadzu software based
on the Ozawa method. The Kissinger method for obtaining the activation energy value was also used for comparison. These results
are discussed here.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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The curing process of a polysulfide (PSF) with a triacrylate crosslinker in the presence of an amine catalyst at room temperature is a rapid Michael addition. This reaction was monitored by real‐time infrared spectrum (RTIR). The results of the RTIR show that the consumptions of thiol and acrylate are stoichiometric until 80% conversion, indicating the characteristics of a “click” reaction. Dielectric analyzer (DEA) and dynamic mechanical analyzer (DMA) were employed to investigate the curing kinetics from which the activation energies of this curing reaction were obtained and shown to correlate with each other. In addition, the influences of the types and amount of amine catalyst, the different molecular weights of PSFs, and the triacrylate crosslinkers were discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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A. S. Araujo M. J. B. Souza V. J. Fernandes Jr. J. C. Diniz 《Reaction Kinetics and Catalysis Letters》1999,66(1):141-146
The catalytic dehydration of isopropanol has been studied over a solid acid silicoaluminophosphate type SAPO-5. The reaction
was processed varying the temperature and weight hourly space velocity, using a fixed bed continous flow reactor. The isopropanol
undergoes inter- and intramolecular dehydration, forming propylene and isopropyl ether, respectively. Nevertheless, the catalyst
was selective to the olefin, with an activation energy of the order of 46.1 kJ/mol. 相似文献
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Dr. Jingyun Ren Dr. Xu Ban Dr. Xin Zhang Dr. Siu Min Tan Dr. Richmond Lee Prof. Dr. Choon-Hong Tan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9140-9143
We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium-catalyzed kinetic resolution (KR) of racemic tertiary bromides under base-free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway. 相似文献
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The kinetic spectrophotometric method for Au(III) determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of methylene blue B (3,7di-(dimethyl amino)-10-dehydro-phenotiazin chloride) by ammonium peroxo-disulfate in citric buffer solution. There was the linearity of the calibration curve in the concentration range from 0.09 to 2.90 μg ml−1 Au(III). The relative standard deviation was 2.50% and correlation coefficient of 0.9999. The limit of detection was determined as signal to noise ratio (3:1) and it was 5.5 ng ml−1. The limit of quantification, based on signal to noise ratio 10:1 was 19.25 ng ml−1. The selectivity was tested on the basis of influence of known amounts of different ions in the reaction mixture, upon the reaction rate. Kinetic and thermodynamic parameters were reported for both catalytic and non-catalytic reactions. The method was verified by Au(III) determination in anti-rheumatic drug “Tauredon” and in human urine samples, using ICP-AES as the comparative method. As the method is accurate, reliable, quick and simple it could be useful for clinical and toxicological practice. 相似文献
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催化动力学光度法测定痕量苯酚 总被引:5,自引:0,他引:5
研究了在硫酸介质中苯酚对I^-1催化Ce^4+-As(Ⅲ)反应的抑制作用及其动力学条件。建立了用催化动力这光度法测定痕量苯酚的新方法,结果表明,在0.001mol/LCe(SO4)2,0.00125mol/L,As2O3,0.01mg/L,KI,0.0125mol/L,H2SO4和0.13%(w/v)NaCl溶液中测定苯酚,其表面摩尔吸光系数为2.1×10^5L.mol^-1.cm^-1,线性范围 相似文献
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The ring-opening reaction of the cyclopropylcarbinyl radical proceeds via heavy-atom tunneling at low temperature. We used instanton theory to calculate tunneling rates and kinetic isotope effects with on-the-fly calculation of energies by density functional theory (B3LYP). The accuracy was verified by explicitly correlated coupled-cluster calculations (UCCSD(T)-F12). At cryogenic temperatures, we found protium/deuterium KIEs up to 13 and inverse KIEs down to 0.2. We also studied an intramolecular tautomerization reaction. A simple and computationally efficient method is proposed to calculate KIEs with the instanton method: the instanton path is assumed to be independent of the atomic masses. This results in surprisingly good estimates of the KIEs for the cyclopropylcarbinyl radical and for the secondary KIEs of the tautomerization. Challenges and capabilities of the instanton method for calculating KIEs are discussed. 相似文献
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在氢氧化钠介质中,芦丁对高碘酸钾氧化偶氮胂Ⅲ褪色反应有明显的催化作用,据此建立了测定芦丁含量的催化动力学光度法.最大吸收波长为590nm,该方法的线性范围为0.03~1.0mg/L.对实验数据进行回归处理的线性方程为ΔΑ=0.4485c(芦丁)+0.0011,相关系数为r=0.9985,检出限为0.0167mg/L.该方法简便,快速,灵敏度高,用于实际样品的测定,结果令人满意. 相似文献
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Jingyun Ren Xu Ban Xin Zhang Siu Min Tan Richmond Lee Choon‐Hong Tan 《Angewandte Chemie (International ed. in English)》2020,59(23):9055-9058
We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium‐catalyzed kinetic resolution (KR) of racemic tertiary bromides under base‐free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway. 相似文献
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Adriana Popa Smaranda Iliescu Nicolae Doca Titus Vlase Gabriela Vlase 《International Journal of Polymer Analysis and Characterization》2017,22(1):43-50
A commercial styrene–divinylbenzene copolymer was functionalized by multistep reactions with alpha-isopropylaminophosphonic acid groups. Three different functionalized copolymers were obtained in which the phosphonic groups are in meta (1E), para (2E), and ortho (3E) positions. The thermal behavior was studied using the TG/IR hyphenated technique and kinetic analysis of thermo-oxidation under nonisothermal conditions. The evolved gas analysis confirms the partial thermo-oxidative degradation of polymeric materials, with significant preservation of the aromatic ring. The kinetic analysis was performed by three methods: Friedman, Flynn–Wall–Ozawa, and nonparametric kinetic. 相似文献
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研究了银阻抑高碘酸钾氧化玫瑰桃红R的褪色反应,建立了阻抑动力学光度法测定痕量银的新方法。找到了最佳试验条件,该方法线性范围为0~2.0μg/mL,应用于水中银的测定,结果满意。 相似文献
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阻抑动力学光度法测定食品中的痕量铜 总被引:3,自引:1,他引:3
研究了铜阻抑高碘酸钾氧化玫瑰桃红R的褪色反应 ,建立了阻抑动力学光度法测定痕量铜的新方法 ,找到了最佳试验条件。该法线性范围为 0~ 0 0 0 8μg/mL ,检出限为 0 3 9× 1 0 - 3μg/mL ,应用于食品中铜的测定 ,结果满意 相似文献
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C. Santi M. Tiecco L. Testaferri C. Tomassini F. Marini L. Bagnoli 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):1071-1075
Abstract The first example of a kinetic resolution process promoted by an electrophilic selenium reagent is reported. Racemic allylic alcohols react with half equivalents of a selenenylating agent in methanol leading to the regiospecific formation of the corresponding addition products with a very high level of facial selectivity (98% de). The unreacted alcohol can be recovered in a optically enriched form (92% ee). 相似文献
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萃取阻抑动力学光度法测定痕量镍 总被引:19,自引:0,他引:19
研究了在pH5.5的弱酸性介质中,利用镍(Ⅱ)阻抑邻菲罗啉活化铜(Ⅱ)催化过氧化氢氧化邻氨基酚的指示反应,用萃取手段控制反应时间、建立了萃取阻抑动力学光度法测定镍的新方法。方法的线性范围为1.0 ̄80μg/L;检测限为9.1×10^-7g/L。用于环境水样,铝合金和人发中镍的测定,结果满意。对反应机理谱进行了探讨。 相似文献