Characterization and catalytic performance of methyl-grafted Ti-HMS catalysts prepared by the CVD method

Methyl-grafted Ti-HMS catalysts were prepared by the chemical vapor deposition (CVD) method using TiCl₄ as titanium source and various organic silanes as silylating agents. The catalysts were characterized by XRD, N₂-adsorption-desorption, FTIR, ²⁹Si NMR, TGA, DR UV-vis, and evaluated by the epoxidation of propylene using cumene hydroperoxide (CHP) as oxidant. The results reveal that the silylated Ti-HMS catalysts are more active than the unsilylated Ti-HMS catalyst, and the methyl-grafted Ti-HMS catalyst silylated with hexamethyldisilazane (HMDSZ) exhibits better epoxidation performance than the analogues silylated with trimethylchlorosilane (TMCS) or dimethyldichorosilane (DMDCS). It is proposed that not only the form of T-O-SiMe_n (n = 2 or 3) but also the breakage of Ti-O-T (Si-O-Si or Si-O-Ti) are observed in silylation using Cl-containing silylating agents (TMCS or DMDCS), which decrease the hydrophobicity of Ti-HMS catalysts and destroy the tetracoordinated titanium species that responsible for the epoxidation performance. This phenomenon has not been observed in silylation with HMDSZ.     

Chemical Constituents of Artemisia frigida

Chemistry of Natural Compounds -     

Crystals of 4-(2-benzimidazole)-1,2,4-triazole and its hydrate: preparations,crystal structure and Hirshfeld surfaces analysis

Research on Chemical Intermediates - Single crystals of compound L (C9H7N5): 4-(2-benzimidazole)-1,2,4-triazole and its hydrate were obtained via slow evaporation. The structures of the crystals...     

一维链状希夫碱铜配合物的高效光芬顿试剂活性

合成了2个希夫碱配合物[Cu(HL1)Cl O4]n(1)和[Cu(HL2)NO3]n(2)(H2L1=N-[(2-oxy-acetate)benzyl]-2-amino ethanol,H2L2=Nsalicylidene-3-amino propanol),并将其在无酸化条件下用作甲基橙降解的光芬顿催化剂。1和2均为一维链状结构且铜为六配位的拉长八面体配位构型。它们均具有优秀的均相光芬顿试剂活性且1的光催化活性更优秀。实验结果表明,本研究中的配体结构对铜配合物的光催化活性有影响。     

Controllability and quadratic stability quadratic stabilization of discrete-time interval systems--an LMI approach

^** Email: qlzhang{at}mail.neu.edu.cn This paper presents necessary and sufficient conditions fordiscrete-time interval systems to be quadratically stable orquadratically stabilizable, and sufficient conditions for discrete-timeinterval systems to be controllable. All the results are obtainedin terms of linear matrix inequality (LMI). With the LMI toolbox,the problems can be conveniently solved. Illustrative numericalexamples show that the results are effective and less conservativeto check the robust controllability and stability and to designthe stabilizing controller for discrete-time interval systems.     

铝化β沸石的硅铝分布及表面酸性质

研究了铝酸钠溶液处理对β沸石硅铝分布及表面酸性质的影响。通过XRD，NH3－TPD，Pyridine-IR及NMR表征了经NaAlO2溶液处理后的Hβ沸石的表面酸性质。结果表明，Hβ沸石的总酸量增加，B酸量和L酸量亦增加。NaAlO2溶液处理对β沸石具有补铝功能，补铝机理为Al(OH4)^-阴离子在Si(0Al)A位发生同晶取代。甲苯歧化与C9芳烃烷基转移反应的催化性能考察结果表明，NaAlO2溶液处理可以提高β沸石催化剂的芳烃转化率和（B＋X）选择性。     

B2O3/TiO2-ZrO2的结构表征及其与酸性和催化性能间的关系

采用XRD、N₂吸附、 ¹¹B MAS NMR、NH₃-TPD和催化性能评价等方法研究了B₂O₃/TiO₂-ZrO₂催化剂的结构、酸性及催化环己酮肟气相Beckmann重排反应性能间的关系。结果表明,催化剂中的B₂O₃同时以三配位的BO₃和四配位的BO₄结构单元存在;     

Synchronization of spatiotemporal chaos in a class of complex dynamical networks

This paper studies the synchronization of complex dynamical networks constructed by spatiotemporal chaotic systems with unknown parameters. The state variables in the systems with uncertain parameters are used to construct the parameter recognizers, and the unknown parameters are identified. Uncertain spatiotemporal chaotic systems are taken as the nodes of complex dynamical networks, connection among the nodes of all the spatiotemporal chaotic systems is of nonlinear coupling. The structure of the coupling functions between the connected nodes and the control gain are obtained based on Lyapunov stability theory. It is seen that stable chaos synchronization exists in the whole network when the control gain is in a certain range. The Gray--Scott models which have spatiotemporal chaotic behaviour are taken as examples for simulation and the results show that the method is very effective.     

非晶态合金表面的水润湿动力学

采用分子动力学模拟方法研究了改进的Simple pointcharge模型SPC/E水滴在Cu_(50)Zr_(50)非晶薄膜上的润湿行为和铺展过程.通过与CuZr(110)和(100)晶面对比研究发现,水滴在Cu_(50)Zr_(50)非晶薄膜表面上表现出较高的铺展速度.水滴在非晶合金表面的铺展过程中形成了明显的吸附层;而在晶态表面,水滴铺展前沿呈脚状形态.分析结果表明非晶表面的水分子在吸附层内呈现完全无序的单层排列方式,而在晶态表面,特别是(100)晶面,吸附层水分子呈双层有序排列.这种吸附层结构的差异导致了吸附层内水分子方向的差异:非晶表面吸附层内水分子方向倾向平行于表面,而晶态基底上吸附层内的水分子倾向于指向液滴内部.由此造成了非晶表面吸附层中的水分子与液滴内部以相对较弱的氢键相互作用,这使得上层水分子能够较容易扩散至吸附层前沿,促进液滴铺展.     

Backstepping synchronization of uncertain chaotic systems by a single driving variable

In this paper a parameter observer and a synchronization controller are designed to synchronize unknown chaotic systems with diverse structures. Based on stability theory the structures of the observer and the controller are presented. The unknown Coullet system and Rossler system are taken for examples to demonstrate that the method is effective and feasible. The artificial simulation results show that global synchronization between the unknown Coullet system and the Rossler system can be achieved by a single driving variable with co-operation of the observer and the controller, and all parameters of the Coullet system can be identified at the same time.