Development of Mesoporous Carbon Cryogels with Desired Porous Characteristics by Using Sol-Gel Method and Freeze Drying

本论文以间苯二酚和甲醛为原料，采用溶胶-凝胶法和冷冻干燥法制备了多种具有独特介孔特性的碳冷冻材料。并提出了一种控制其多孔性能的方法。取得了以下研究成果：1.通过光散射实验和基于粒子数平衡模型的计算机模拟，研究了间苯二酚-甲醛(RF)水溶液的凝胶化过程。研究发现，催化剂在RF水溶液中的浓度是决定溶胶-凝胶转变过程中结构形成的主要因素。以间苯二酚和甲醛为原料，采用溶胶-凝胶法和冷冻干燥法制备了碳冷冻。碳气凝胶的介孔性能丝毫不逊色于超临界干燥法制备的碳气凝胶。研究了RF溶液的溶胶-凝胶条件对碳冷冻干酪介孔性能的影响。研究发现，它们的介孔性质与催化剂在RF溶液中的浓度有关。通过改变催化剂的浓度可以控制碳制冷剂的介孔性质。以RF溶液为原料，通过反相乳液聚合，在惰性气氛中冷冻干燥和热解，成功地合成了冷冻碳凝胶(CC)微球。证实了CC微球具有双重结构，即介孔内部被微孔表面层覆盖。通过改变乳液温度和热解温度，可以制备出具有超微孔表面的介孔微球和具有超微孔表面的微球。结果表明，CC微球是一种潜在的碳材料，可用于高效液相色谱柱的填充材料，但其性能有待进一步研究。

In the present work, many kinds of carbon cryogels with unique mesoporous characteristics were prepared from resorcinol and formaldehyde by using sol-gel method and freeze drying. A method for controlling their porous properties was also proposed. The following results were obtained.1. The gelation process of resorcinol-formaldehyde (RF) aqueous solution was studied by using the light scattering experiment and the computer simulation based on the population balance model. It is found that the catalyst concentration in the RF aqueous solution is a main factor for determining the structure formation during the sol-gel transition.2. Carbon cryogels are successfully prepared from resorcinol and formaldehyde by using sol-gel method and freeze drying. The mesoporous properties of carbon cryogels are by no means inferior to those of the carbon aerogels prepared by supercritical drying.3. The influence of sol-gel condition of RF solution on mesoporous properties of carbon cryogels was investigated. It is found that their mesoporous properties are correlated with the catalyst concentration in the RF solution. The mesoporous properties of carbon cryogels can be controlled by changing the catalyst concentration.4. Carbon cryogel (CC) microspheres were successfully synthesized via an inverse emulsion polymerization of RF solution followed by freeze drying and pyrolysis in an inert atmosphere. CC micrspheres are confirmed to possess a dual structure, i.e. a mesoporous inner part covered by a microporous surface layer. It is possible to prepare both mesoporous microspheres and microspheres having utramicroporous surface which pore sizes can be controlled by changing the temperature of emulsion and the pyrolysis temperature. CC microspheres are demonstrated to be potential carbons, which are applicable to column packing materials for HPLC although further investigation is necessary for improving their performances.