Novel method for synthesis of titanium silicalite-1 (TS-1)

Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3· H2O, HDA or TEAOH etc. as base sources. In this system, TPA cations (come from TPABr or TPAOH) served as tern-plating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, ER spectroscopies, SEM, 29 Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.     

Experimental Researches on Milled Wood Lignin Pyrolysis Based on Analysis of Bio-oil

The structure of milled wood lignin(MWL), isolated via the Bjrkman procedure, was studied by means of 1H NMR spectroscopy and Fourier transform infrared spectroscopy, and then its pyrolytic product distribution was investigated on a pyrolysis device. MWL obtained from Manchurian Ash(MA) contained more methoxyl and free phenolic hydroxyl groups per C9 unit than MWL from Mongolian Pine(MP) due to the existence of both guaiacyl and syringyl units, which have a major influence on the pyrolysis behavior of lign...     

PROMOTING TEACHING BY USING COMPETITION PROBLEMS IN ENGINEERING MECHANICS TEACHING1)

本文提出以课堂教学为载体,强化力学竞赛试题在培养学生创新思维能力和力学建模能力的作用,激发学生学习工程力学课程兴趣的教学改革思路和方法。通过调整教学例题内容、增加例题的趣味性、强化力学建模训练以及增强定性分析意识,有效解决了力学竞赛培训中遇到的问题。实践证明,"以赛促教"教学模式可有效激发学生学习工程力学的热情,有助于掌握课程的核心内容及其工程应用。     

中国催化三十年进展:理论和技术的创新

中国的催化科学与技术始于20世纪初,经过先辈的努力使其经历了发展初期和稳定发展阶段,在历史上由于人为因素的严重破坏使其处于停滞并失去了宝贵的十余年大好发展时机.20世纪80年代,中国催化事业进入了快速发展时期.在这一历史时期,迅速恢复和建立了以中科院、高校和产业部门研究院组成的三个方面军的研究队伍.开展了以形式动力学为主要方法和手段的研究,基础研究方面提炼出新催化材料、新催化表征方法和新催化反应为主要研究方向.表面科学、纳米科学的出现大大促进和深化了催化的基础探索,催化正从艺术走向科学…….在应用催化研究方面,在不同历史时期结合国家重大需求,在煤、石油、天然气优化利用,先进材料,环境,人类健康等领域做出了重大贡献.当前的中国已成为催化大国并正在走向催化强国.     

雕白粉与食品亚硫酸盐漂白剂

本文分析了目前社会上反应强烈的在食品中所添加的雕白粉的毒性 ,对食品工业中使用的亚硫酸及其盐类漂白剂的漂白、抗氧化、防腐及可能的毒副作用进行了综述。     

Influence of lanthanum on the performance of Zr-Co/activated carbon catalysts in Fischer-Tropsch synthesis

The influence of La loading on Zr-Co/activated carbon （AC） catalysts has been studied for Fischer-Tropsch synthesis. The catalyst samples were characterized by XRD, TPR, CO-TPD, and temperature programmed CO hydrogenation. The catalytic property was evaluated in a fixed bed reactor. The experimental results showed that CO conversion increased from 86.4% to 92.3% and the selectivity to methane decreased from 14.2% to 11.5% and C5＋ selectivity increased from 71.0% to 74.7% when low La loading （La = 0.2wt%） was added into the Zr-Co/AC catalyst. However, high loadings of La （La = 0.3-1.0 wt%） would decrease catalyst activity as well as the C5＋ selectivity and increase methane selectivity. XRD results displayed that La-modified Zr-Co/AC catalyst had little effect on the dispersion of Co catalyst. But, the results of TPR, CO-TPD, and temperature programmed CO hydrogenation techniques indicated that the extent of cobalt reduction was found to greatly influence the activity and selectivity of the catalyst. The addition of a small amount of La increased the reducibility of the Zr-Co/AC catalyst and restrained the formation of methane and improved the selectivity to long chain hydrocarbons. However, excess of La led to the decrease of the reducibility of Co catalyst thus resulted in higher methanation activity.     

Stability constants of amino acids, peptides, proteins, and other biomolecules determined by CE and related methods: recapitulation of published data

The stability (affinity, association, binding, complexation, formation) constant characterizes binding interaction between the analyte and the complexing agent. Knowledge of the stability constant makes possible the prediction and estimation of the binding behavior of constituents (amino acids, peptides, proteins, drugs, antibiotics, enzymes, enantiomers) to their partners, and the finding of a suitable partner for the given analyte to form a stable complex. The present paper summarizes the stability constant determination methods and the approaches used to evaluate the experimental data. Further, the paper recapitulates the published stability constant values determined, mainly, by capillary electrophoretic methods, taken from the Web of Science database covering the last decade. Details of the experimental conditions employed for the determination of the stability constants are also given. The review attempts to give a critical evaluation of the problems that accompany the determination of stability constant and discusses their solution.     

Prediction and understanding system peaks in capillary zone electrophoresis

Introduction of a sample into the separation column (microchip channel) in capillary zone electrophoresis (microchip electrophoresis) will cause a disturbance in the originally uniform composition of the background electrolyte. The disturbance, a system zone, can move in some electrolyte systems along the separation channel and, on reaching the position of the detector, cause a system peak. As shown by the linear theory of electromigration based on linearized continuity equations formulated in matrix form, the mobility of the system zone--the system eigenmobility--can be obtained as the eigenvalue of the matrix. Progress in the theory of electromigration allows us to predict the existence and mobilities of the system zones, even in very complex electrolyte systems consisting of several multivalent weak electrolytes, or in micellar systems (systems with SDS micelles) used for protein sizing in microchips. The theory is implemented in PeakMaster software, which is available as freeware (www.natur.cuni.cz/gas). The linearized theory also predicts background electrolytes having no stationary injection zone (water zone, water gap, water dip, EO zone) or unstable electrolyte systems exhibiting oscillations and creating periodic structures. The oscillating systems have complex system eigenmobilities (eigenvalues of the matrix are complex). This paper reviews the theoretical background of the system peaks (system eigenpeaks) and gives practical hints for their prediction and for preparing background electrolytes not perturbed by the occurrence of system peaks and by excessive peak broadening.     

Asymmetric aza-Henry reaction with α-substituted nitroacetates catalyzed by a bifunctional thiourea-guanidine catalyst

The asymmetric aza-Henry reaction of α-substituted nitroacetates and N-Boc imines was achieved with a new-type thioureaguanidine bifunctional organocatalyst.The novel transformations exhibited high diastereoselectivities,and the adducts bearing adjacent quaternary and tertiary chiral centers were generally obtained in moderate to good enantioselectivities(up to 88%ee).     

P/Rh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应的影响

研究了P/Kh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应性能的影响.结果表明,当P/Rh比为15时,丙烯氢甲酰化反应性能最好,丙烯转化率为25.9%,产物丁醛正异比为14,转换频率为241 h-1.PPh3-Rh/SiO2催化剂的固体31P核磁共振结果表明,在合成气气氛下,物理吸附的PPh3能够溢流到Rh/S...