Development of Reaction/Separation Devices for Microfabricated Chemical Systems by Ice-Templating

微制造化学系统（MCS）是近年来的研究热点。冰模板法是以微米级冰晶为模板，制备具有微生物体、微蜂窝等多种形貌的多孔材料的方法。本工作利用该方法研制了微胶囊的反应/分离装置，采用冰模板法制备了硅胶微蜂窝（SMH）。冰晶作为模板，其中有一个连续的棒形，多边形的横截面和有序的直径，内前体二氧化硅水凝胶生长的条件下，他们的伪稳态生长继续。除了它们的有序的大孔，微孔/介孔内的蜂窝壁通过浸泡在叔丁醇中的SMHs的冷冻干燥发展。SMH具有直的和多边形的大孔空隙，这些空隙是通过冰晶的形成和去除而产生和保留的。微形态 ...更多信息 通过扫描电镜观察、氮气吸附-脱附测试和热重分析等手段对SMH的大孔尺寸、壁厚、孔壁内部的微孔/中孔结构以及热稳定性进行了详细的研究。有人发现，大孔尺寸的SMHs可以通过改变浸入率到一个冷浴和冷冻温度控制，而不改变其蜂窝壁的微/中孔。研究还发现，SiO_2浓度和大孔孔径对蜂窝壁厚度有影响。另一方面，通过在碱性水溶液中对制备的SMH进行水热处理，可以将蜂窝壁的孔隙率控制为微孔和中孔。此外，发现具有发达的中孔的SMH对热处理表现出更高的稳定性。成功制备了1/16 ~ 1/2英寸的SMH高效液相色谱分离柱，并将其应用于高效液相色谱，其压降小。采用冰模板法制备了具有布朗斯台德酸活性和催化活性的SiO_2-Al_2O_3冻胶微蜂窝。Al原子在纳米水平上被引入到二氧化硅骨架中。成功制备了TiO_2-SiO_2晶胶微蜂窝。用透射电子显微镜观察到TiO_2以极细的颗粒存在。与商业光催化剂相比，该微蜂窝对大分子有机物的分解具有更高的光催化活性。少

Microfabricated chemical systems (MCSs) have been greatly interested in recent years. The unthors have proposed the ice-template method, which uses micrometer-sized ice crystals as a template, to prepare porous materials with various morphologies such as microbiber and microhoneycomb. In the present work the reaction/separation devices for MCSs were developed by using this method.Silica gel microhoneycombs (SMHs) were prepared through the ice-template method. Ice crystals used as a template, which had a continuous rod shape, a polygonal cross section and ordered diameters, were grown inside precursor silica hydrogels under a condition where the pseudo-steady-state growth of them continues. Besides their ordered macroporosity, micro-/mesopores develop inside the honeycomb walls through the freeze-drying of SMHs soaked in tert-butyl alcohol. SMHs had straight and polygonal macroporous voids, which are created and retained through the formation and removal of the ice crystals. Micromorpho … More logy including macropore size and wall thickness, micro-/mesoporosity inside the honeycomb walls, and thermal stability of SMHs were investigated in detail through scanning electron microscopy observation, nitrogen adsorptiondesorption measurements, and thermogravimetric analysis. It was found that the macropore size of the SMHs can be controlled by changing the immersion rate into a cold bath and the freezing temperature without changing the micro-/mesoporosity of their honeycomb walls. It was also found that the thickness of the honeycomb walls was affected by the SiO_2 concentration and the macropore size. On the other hand, the porosity of the honeycomb walls could be controlled to be microporous as well as mesoporous by hydrothermal treatment of as-prepared SMHs in basic aqueous solutions. Moreover, it was found that SMHs with developed mesopores showed a higher stability against heat treatment. SMHs were successfully fabricated as separation columns of 1/16 to 1/2 inch for high performance liquid chromatography (HPLC), and the columns prepared showed small pressure drop when they were applied to HPLC.SiO_2-Al_2O_3 cryogel microhoneycobs, which had bronsted acid cites and catalytic activities, were prepared by ice-templating. Al atoms were incorporated into silica frameworks at a nanometer level. TiO_2-SiO_2 cryogel microhoneycombs were also successfully prepared. It was found that TiO_2 existed as extremely fine particles by using a transition electron microscope. The microhoneycombs showed higher photocatalytic activities for decomposition of large-organic molecules than a commercial photocatalyst. Less