通过"双离子键"固载于季鏻盐聚合物的[Rh(CO)I3]2–物种在多相乙醇羰基化中的应用

贵金属物种(Rh或Ir络合物)在均相羰基化和氢甲酰化催化过程得到了广泛的应用,但始终存在分离繁琐等问题,其均相多相化可很大程度上简化分离操作,故一直广受重视.单位点催化剂因其具有可与均相相比拟的较高金属利用率和选择性而成为均相多相化的重要研究方向之一.研究发现,在碘物种存在的情况下用于固载金属物种的配位键容易断裂,进而导致金属物种的流失,而通过离子键固载的[Rh(CO)₂I₂]^–物种更加稳定,比如著名的甲醇羰基化“Acetica^TM”工艺中,[Rh(CO)₂I₂]^–负一价阴离子物种是以离子键的方式固定在带有阳离子骨架的甲基化聚乙烯吡啶树脂上.与甲醇羰基化过程类似的乙醇羰基化过程是生产重要化工中间体丙酸的主要途径之一,但该过程的均相多相化始终存在着稳定性差这一关键问题.为了解决这一问题,基于之前将固载于季鏻盐聚合物的[Rh(CO)I₃]^2–应用于甲醇羰基化的工作,我们将类似的季鏻盐聚合物固载Rh基催化剂Rh-TPISP用于多相乙醇羰基化过程,通过多种表征进一步证明了Rh物种和P物种结构,并提出了“双离子键”模型.P的K边XANES证明了聚合物TPISP的季鏻化阳离子骨架特征.HAADF-STEM测试表明Rh-TPISP中的Rh呈现单位点分散的状态.Rh的XPS和XANES结果证明了Rh-TPISP中Rh物种的价态介于0~+1.通过EXAFS的拟合解析给出了[Rh(CO)I₃]^2–活性中心结构.由于[Rh(CO)₂I₂]^–为经典的羰基化活性中心,为了进一步证明该结构的正确性,我们将Rh-TPISP的EXAFS和IR谱图与标样[PPh3Et]⁺[Rh(CO)₂I₂]^–对比发现:在EXAFS谱图中,Rh-TPISP中的Rh-C峰高低于[PPh3Et]+[Rh(CO)₂I₂]^–的Rh-C峰高,而Rh-TPISP中的Rh-I峰高高于[PPh3Et]+[Rh(CO)₂I₂]^–的Rh-I峰高,这就说明Rh-TPISP中Rh物种的Rh-C配位数小于2,而Rh-I配位数大于2;在IR谱图中,标样[PPh3Et]+[Rh(CO)₂I₂]^–中有两个羰基振动峰,与该物种的两个Rh-C配位键相符,而Rh-TPISP中的只有一个羰基振动峰,说明Rh-C配位数为1.因此,Rh-TPISP催化剂的季鏻盐骨架中的每个P物种带有一个正电荷,每个带有两个负电荷的[Rh(CO)I₃]^2–通过与两个[P]⁺的静电作用进行固载,形成“双离子键”结构.该催化剂在固定床乙醇羰基化过程中表现出优异的羰基化活性、选择性和稳定性.在3.5 MPa、195 oC反应近1000 h后,Rh-TPISP催化剂TOF保持在约350 h–1,丙酰基选择性为95%以上,高出所有文献报道的均相和多相乙醇羰基化活性.其较高的活性主要是因为[Rh(CO)I₃]^2–比传统Rh活性相[Rh(CO)₂I₂]^–具有更强的富电子性,而较高的稳定性主要是由于“双离子键”这种强静电作用比“AceticaTM”工艺中“单离子键”更有利于Rh物种的固载.故Rh-TPISP催化剂中的“双离子键”对其优异的催化性能具有极其重要的作用,对后续多相乙醇羰基化的发展具有重要意义.     

Estimation of ultra-stability of methane hydrate at 1 atm by thermal conductivity measurement

Thermal conductivity of methane hydrate was measured in hydrate dissociation self-preservation zone by means of the transient plane source (TPS) technique developed by Gustafsson. The sample was formed from 99.9% (volume ratio) methane gas with 280 ppm sodium dodecyl sulfate (SDS) solution under 6.6 MPa and 273.15 K. The methane hydrate sample was taken out of the cell and moved into a low temperature chamber when the conversion ratio of water was more than 90%. In order to measure the thermal conductivity, the sample was compacted into two columnar parts by compact tool at 268.15 K. The measurements are carried out in the temperature ranging from 263.15 K to 271.15 K at atmospheric pressure. Additionally, the relationship between thermal conductivity and time is also investigated at 263.15 K and 268.15 K, respectively. In 24 h, thermal conductivity increases only 5.45% at 268.15 K, but thermal conductivity increases 196.29% at 263.15 K. Methane hydrates exhibit only minimal decomposition at 1 atm and the temperature ranging from 263.15 K to 271.15 K. At 1 atm and 268.15 K, the total gas that evolved after 24 h was amounted to less than 0.71% of the originally stored gas, and this ultra-stability was maintained if the test was lasted for more than two hundreds hours before terminating.     

仿生模糊直接自适应控制

针对一类不确定非线性系统,设计了一种具有仿生特性的模糊直接自适应控制方法.方法将反应生物特性的生态位态势理论函数作为模糊规则的后件,将生物个体对外界扰动的适应对策引入控制器设计中,利用超稳定理论设计自适应控制律,保证了闭环系统的稳定性和收敛性.仿真结果表明了方法的有效性,比常规控制方法有更好的控制效果.     

Ultra-Stable Rubidium-Stabilized External-Cavity Diode Laser Based on the Modulation Transfer Spectroscopy Technique

We construct an ultra-stable external-cavity diode laser via modulation transfer spectroscopy referencing on a hyperfine component of the ST Rb D2 lines at 780 nm. The Doppler-free dispersion-like modulation transfer signal is obtained with high signal-to-noise-ratio. The instability of the laser frequency is measured by beating with an optical frequency comb which is phase-locked to an ultra-stable oven controlled crystal oscillator. The Allan deviation is 3.9 × 10-13 at I s averaging time and 9.8 ×10-14 at 90s averaging time.     

A Hertz-Linewidth Ultrastable Diode Laser System for Clock Transition Detection of Strontium Atoms

The frequencies of two 698 nm external cavity diode lasers （ECDLs） are locked separately to two independently located ultrahigh finesse optical resonant cavities with the Pound Drever-Hall technique. The linewidth of each ECDL is measured to be -4.6 Hz by their beating and the fractional frequency stability below 5 × 10^-15 between 1 s to lOs averaging time. Another 698nm laser diode is injection locked to one of the cavity-stabilized ECDLs with a fixed frequency offset for power amplification while maintaining its linewidth and frequency characteristics. The frequency drift is H1 Hz/s measured by a femtosecond optical frequency comb based on erbium fiber. The output of the injection slave laser is delivered to the magneto-optical trap of a Sr optical clock through a iO- ta-long single mode polarization maintaining fiber with an active fiber noise cancelation technique to detect the clock transition of Sr atoms.     

超稳定玻璃

非晶态物质处于热力学非平衡状态,稳定性是非晶态材料应用的重要瓶颈,也是理论研究的关键问题.最近人们开发出相当于普通金属玻璃退火上百万年的"超稳定玻璃",为研究非晶态材料的稳定性和非晶态物质的本质提供了新契机.本文简要介绍超稳定玻璃的特点、形成机理以及其对非晶态物理学基本问题提供的新见解和新思路.     

800MHz超屏蔽磁体（800US2）

世界上第一台高分辨率越屏蔽超、稳定磁体800US2诞生在布鲁克公司，成为布鲁克磁体系列中又一项无可争辨的世界第一.     

超稳定结构的MCNTs/CeO2纳米粒子复合材料的制备

采用溶剂热的方法,通过改变反应体系中水的含量,合成制备了不同形态、粒度和复合方式的二氧化铈纳米粒子(ceria nano-particles)/碳纳米管(multi-walls carbon nanotubes-MCNTs)复合材料.反应溶液甲醇中存在少量水的条件下,二氧化铈纳米粒子为球形,具有单晶结构,平均粒度为100 nm左右,与碳纳米管形成超稳定的"串珠"结构的复合材料;反应溶液为甲醇时,二氧化铈纳米粒子粒度约为20 nm的不规则形状,粒子的长轴沿碳管径向分布.X射线衍射分析表明,二氧化铈纳米粒子晶体结构为面心立方.     

同时抑制低频振荡和次同步振荡的多通道广域自适应阻尼控制

设计了一种的自适应控制算法并证明了其正确性. 通过总体最小二乘旋转不变技术辨识出系统降阶模型及相关振荡模态,利用带通滤波器将不同的振荡模态分解到多个通道,然后基于所提的自适应算法对每个振荡模态设计了自适应控制器,减小了各个控制器间的影响. 在电磁暂态程序PSCAD/EMTDC中对向上直流孤岛运行方式进行了仿真验证. 结果表明：所提控制方法相对传统比例积分微分控制有更好的控制效果;对于系统发生不同故障时具有鲁棒性. 对于系统信号传输引起的时滞导致的控制器效果变差的问题,可以通过相位补偿解决. 关键词： 超稳定理论 系统辨识 振荡 自适应阻尼控制