Diffusioosmotic micropolar liquid flows in parallel plate microchannels subject to boundary slip

Meccanica - Analytical solutions to the microrotation, linear velocity, and volume flow rate are developed for electrokinetic diffusioosmotic flows of micropolar liquids in slit microchannel...     

Passive solute separation in AC electroosmosis including surface charge-coupled hydrodynamic slip effects

Separation of electrically neutral, mutually noninteracting passive solutes via AC electroosmotic slit channel flows is investigated for general asymmetric wall surface zeta potentials and apparent hydrodynamic slip lengths. We consider the nontrivial coupling between the surface potentials (or charge densities) and the apparent slip lengths, and focus our attention on the occurrence of a so called “crossover phenomenon” for separating out the slow diffusers when both slow and fast diffusers are present. Results show that regardless of the potential-slip coupling, wider bandwidths become available for crossover phenomenon to occur when the electroosmotic velocity gradient (magnitude) is greater. Contrarily, plug-like velocity profiles inhibit crossover phenomenon, and the potential-slip parametric combinations leading to such profiles can be easily identified by the conditions for minimal transport enhancement reported in recent literature. When separating out the slow diffuser or crossover phenomenon is desired, we recommend incorporating significant asymmetry in the surface potential and apparent slip boundary conditions such that the operating frequency and flow oscillation amplitude may be lowered to more practical values. Our results also agree with and strengthen the physical picture for explaining crossover phenomenon in macroscopic pressure-driven oscillatory flows.     

Low-temperature heat capacity and standard thermodynamic functions of the novel ionic liquid 1-(2-methoxyethyl)-3-ethyl imidazolium perrhenate

Journal of Thermal Analysis and Calorimetry - The ionic liquid 1-(2-methoxyethyl)-3-ethyl imidazolium perrhenate [C22O1IM][ReO4] was prepared in the laboratory firstly, and its structure was...     

不同金属改性HZSM-5催化剂的甲醇羰基化反应性能

以具有酸性特性的HZSM-5分子筛为载体,结合金属本身具有的羰基化活性,可以更好的提高羰基化反应效率。采用负压沉积沉淀法对HZSM-5催化剂进行Pt、Pd、Cu、Au、Zn改性,制备不同酸度的催化剂。利用X射线衍射、NH₃程序升温脱附、吡啶吸附FTIR、N₂吸附-脱附和X射线荧光分析研究了不同金属对催化剂物理化学性质及不同负载型HZSM-5催化剂对甲醇羰基化产物的分布和产率的影响。结果表明,不同金属的引入对HZSM-5催化剂的比表面积、孔径和孔体积影响较小,但明显地改变了催化剂表面的酸强度。Pt、Au、Zn和Cu改性后的催化剂更有利于甲醇羰基化反应的进行,其中Cu/HZSM-5催化剂在400℃的甲醇转化率高达90.2%,比HZSM-5催化剂的甲醇转化率高12%,但目标产物的选择性比Pt/HZSM-5及Au/HZSM-5的低。总的来看,金属的引入改变了催化剂表面Brønsted酸（B酸）和Lewis酸（L酸）中心的数量,甲醇的转化率随总酸量的增加而增加,催化剂表面B酸与L酸的比例在0.3~0.5时,催化剂表现出更好的羰基化作用。