| 王馨博,栾志强,李凯,栗丽,唐腾飞.气凝胶在气体吸附净化中的应用研究进展[J].材料导报,2018,32(13):2214-2222, 2240 |
| 气凝胶在气体吸附净化中的应用研究进展 |
| Progress in Application of Aerogels as Adsorbents for Gas Purification |
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| DOI：10.11896/j.issn.1005-023X.2018.13.012 |
| 中文关键词: 气凝胶 吸附剂 吸附 气体净化 修饰改性 |
| 英文关键词: aerogels, adsorbents, adsorption, gas purification, modification |
| 基金项目:国家重点研发计划项目(2016YFC0204205) |
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| 摘要点击次数: 3369 |
| 全文下载次数: 292 |
| 中文摘要: |
| 气凝胶(Aerogels)是一种以空气为介质的轻质多孔性凝聚态物质,由胶体粒子或高聚物分子相互聚集构成独特的纳米多孔三维网络结构。气凝胶的颗粒相和孔隙尺寸均为纳米量级,具有相当高的比表面积和孔隙率、可调控的开放孔隙结构、易于化学修饰的表面以及多样化的种类和形态,其气体吸附量可比同等条件下活性炭吸附量高两个数量级,因此在气体吸附净化领域逐渐受到人们的广泛关注。目前,气体吸附净化领域研究较多的气凝胶主要是SiO2气凝胶和炭气凝胶。此外,近年来对金属氧化物气凝胶以及SiC气凝胶、石墨烯气凝胶、生物质基气凝胶等新型气凝胶的气体吸附应用也有相应的研究报道。 吸附材料对目标气体需要同时具有较高的吸附容量和良好的选择性吸附能力。气凝胶的高比表面积和多孔性质提供了众多的吸附位点,但仅依靠自身物理吸附作用的吸附量有限,对目标气体的选择性不高,在实际吸附应用中,往往由于共存气体组分的竞争吸附影响对目标气体的吸附性能。因此,为了进一步提升气凝胶的吸附容量,提高对目标气体的选择性,研究人员围绕气凝胶修饰改性进行了大量的研究探索工作,并取得了一定的进展。 目前,气凝胶吸附净化研究报道的目标气体主要是温室气体CO2和大气中主要的污染物挥发性有机化合物(VOCs)。针对目标气体的不同可分别通过氨基功能化、氮掺杂等方法引入碱性位点或通过引入非极性官能团对气凝胶进行疏水改性,以提升气凝胶对CO2或VOCs的吸附量和选择性。所采用的修饰改性方式主要有以下两种:一是在湿凝胶形成后或超临界干燥后通过嫁接、浸渍等手段对气凝胶表面进行功能化改性,通过引入特定的官能团或活性组分提升气凝胶对目标气体的吸附量和选择性；另一种是在溶胶-凝胶反应过程中引入功能化前驱体,在分子或纳米尺度上赋予气凝胶网络特定的性能,进而有效平衡活性组分稳定性和对目标气体的吸附性能。此外,对于炭气凝胶,还可通过活化进一步增大比表面积,改善孔隙结构和表面化学性质,从而实现对目标气体污染物吸附性能的优化。 本文归纳了各类气凝胶在CO2与VOCs吸附净化方面的研究进展,介绍了气凝胶的制备过程和结构特点,讨论并对比了不同气凝胶对目标气体的吸附性能与吸附机理,总结了当前气体吸附净化研究中对气凝胶进行修饰改性的主要方法,最后指出提高气凝胶的结构稳定性和吸附速率、设计可同时吸附多种目标气体的气凝胶、缩短制备周期并降低成本是未来研究工作的重点。 |
| 英文摘要: |
| Aerogels are highly porous light-weight solid materials with unique three-dimensional network structures constructed from colloid particles or polymer molecules, and the whole nanoporous network of aerogels is filled with air. The particles and pore size of aerogels are of nanometer magnitude. Thanks to their high specific surface area and porosity, adjustable open pore structure, easiness of chemical modification and diverse types/forms, the aerogels have received considerable attention as adsorbents for gas purification. The adsorption capacity of aerogels can be two orders of magnitude higher than that of activated carbons under the same condition. Currently, SiO2 aerogels and carbon aerogels are the main research objects in the field of gas adsorption and purification. In addition, metal oxide aerogels and novel aerogels such as SiC aerogels, graphene aerogels and biomass-based aerogels have also been explored for gas adsorption application recently. The adsorption materials should possess high adsorption capacity and good selectivity for target gases. Although the high specific surface area and porosity of aerogels provide numerous adsorption sites, the adsorption capacity for gases is usually limited only depending on their own physical adsorption and selectivity is unsatisfactory as well. Besides, the adsorption performance of the target gas is often badly affected by the competitive adsorption of the coexisting gas components in practical application. Therefore, aiming to further enhance the adsorption capacity of aerogels and improve the selectivity of target gases, huge researches have carried out around the modification of aerogels and certain progress has been made. Currently, target gases reported in the aforementioned researches mainly include the major greenhouse gas CO2 and atmospheric pollutants volatile organic compounds (VOCs). Several methods have been proposed to improve the capacity and selectivity of aerogels. For CO2 adsorption, aerogels are principally modified by amino-functionalization and nitrogen-doping to introduce basic sites on the surfaces; and for VOCs adsorption, non-polar organic functional groups are commonly introduced to increase their surface hydrophobicity. The modification methods can be divided into the following two types. One is to functionalize the aerogel surface by graf-ting and impregnation after wet gel formation or supercritical drying, and the adsorption capacity and selectivity of aerogel to target gas can be enhanced by introducing specific functional groups or active components. The other is to introduce functionalized precursors in the sol-gel process which gives the aerogel network specific properties at molecular or nano scale, thus effectively balancing the stability of the active component and the adsorption performance of the target gas. Moreover, the specific surface area, pore structure and surface chemical properties of carbon aerogels can be further improved through activation, and finally the adsorption performance of target gas pollutants can be optimized. This review offers a retrospection of the research efforts for the application of different aerogels in CO2 and VOCs adsorption. Firstly, the general preparation process and structural characteristics of aerogels are briefly introduced. Then, the adsorption performances and mechanisms of various aerogels are mainly discussed, as well as the summary of primary methods of the aerogel modification. Based on the recent research progress, this review points out the focus of future research including improving the structural stability and adsorption rate of aerogels, designing aerogels capable of adsorbing multiple gases simultaneously, shortening the preparation period and lowering the cost. |
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