中温捕获二氧化碳和缓释薄荷醇的多孔新材料

发布时间：2018-08-26 06:54

【摘要】：针对社会发展和环境保护的需求开发新材料是科学家面临的挑战。这些新材料不仅仅来源于前所未闻的新结构,而且受惠于新理念赋予现有材料的新功能。针对合成介孔分子筛时除去模板剂胶束的步骤繁琐、浪费能源,我们利用胶束的温控效应,开拓吸附-释放薄荷醇的新途径。面对燃煤电厂烟道气里CO_2排放造成严重环境污染,我们致力研制固体碱新材料:采用石墨烯和碳微粒共同修饰氧化镁(MgO),并研制FeO-MgO二元氧化物,着重提升吸附剂里强碱中心所占的比例以增加它中温捕获CO_2的能力。我们还结合CO_2瞬时吸附(IA)和程序升温脱附(TPD)方法尝试形成IA-TPD的新检测手段,分析碳修饰MgO固体碱吸附-脱附CO_2的机制。主要研究内容如下:1.根据某些介孔氧化硅分子筛孔道中模板剂胶束的柔软度随温度改变的特性,试用介孔分子筛MCM-41合成原粉(简称as-M41)来吸附-储存和释放高挥发性香料薄荷醇。as-M41样品中的胶束在较高温度如373 K时具有柔性,允许客体分子穿越而进入孔道内部。常温时胶束失去柔性而闭锁-封存孔道里的客体分子。温度再升高到例如353 K时,胶束恢复柔软、被封装的客体分子才能从孔道中被释放。我们采用介孔分子筛合成原粉顶空吸附薄荷醇,GC-MS方法监测薄荷醇的释放。为可控吸储-释放易挥发有机分子提供新途径。2.发现MgO基吸附剂的CO_2中温吸附效率不仅仅限于样品的比表面积,因为423 K时的CO_2吸附主要依赖于强碱性位,而强碱位则来自MgO晶体上缺失Mg2+阳离子的表面缺陷位。我们采用石墨烯和碳微粒原位分隔MgO微粒防止聚集,使得MgO晶体的表面缺陷充分暴露,形成强碱位有效捕获CO_2。采用"吹扫法"和"脉冲法"两种CO_2接触方式,联合瞬时吸附和程序升温脱附组成IA-TPD新检测方法,由CO_2气体的引入量、吸附量和脱附量推算吸附剂中各种强度的碱性位的贡献。将醋酸盐原位碳化法试用于CaO样品的研制,为制备高效CO_2吸附剂提供绿色环保的新途径。3.工业排放烟道气温度通常在423～673 K。在这温度下,固体碱物理吸附CO_2难以进行,因此研制新型高效的中温CO_2捕获剂迫在眉睫。我们利用醋酸镁这种廉价易得的前驱体掺杂醋酸亚铁后、原位碳化制备了 3%FM样品,氧化亚铁含量只有3%,既满足了绿色环保的吸附剂制备需求,又达到了 473 K下CO_2吸附量为35 mg g~-1的吸附效果。这种方法使得MgO颗粒里强碱位的比例有了明显的提升,对于473 K捕获CO_2非常有利,为高效环保固体吸附剂的设计提供了新思路。
[Abstract]:It is a challenge for scientists to develop new materials to meet the needs of social development and environmental protection. These new materials not only come from new structures that have never been heard of, but also benefit from the new ideas that give new functionality to existing materials. In view of the tedious steps of removing template micelles in the synthesis of mesoporous molecular sieves and the waste of energy, we use the temperature control effect of micelles to develop a new way of adsorption-release menthol. In the face of serious environmental pollution caused by CO_2 emission from flue gas in coal-fired power plants, we are committed to develop new solid alkali materials: graphene and carbon particles are used to modify MgO (MgO), and FeO-MgO binary oxides are prepared. Emphasis is placed on increasing the proportion of strong alkali centers in the adsorbent to increase its ability to capture CO_2 at medium temperature. Combined with CO_2 transient adsorption of (IA) and temperature-programmed desorption of (TPD), we also attempted to form a new method for the detection of IA-TPD, and analyzed the mechanism of carbon-modified MgO solid base adsorption-desorption of CO_2. The main research contents are as follows: 1. According to the temperature dependence of the softness of template micelles in some mesoporous silica molecular sieve channels, Mesoporous molecular sieve MCM-41 powder (as-M41) was used to adsorb, store and release the micelles in the sample of high volatile spice menthol. As-M41 was flexible at a higher temperature, such as 373K, allowing the guest molecules to traverse and enter the pore interior. At room temperature the micelles lose flexibility and lock-up the guest molecules in the channels. When the temperature rises to 353K for example the micelle is soft and the encapsulated guest molecule can be released from the pore. The release of menthol from mesoporous molecular sieve was monitored by headspace adsorption of menthol by GC-MS. It provides a new way for controllable absorption, storage and release of volatile organic molecules. It is found that the temperature adsorption efficiency of MgO based adsorbent CO_2 is not limited to the specific surface area of the sample, because the adsorption of CO_2 at 423 K mainly depends on the strong alkaline potential, and the strong base site is derived from the absence of the surface defect site of the Mg2 cation on the MgO crystal. We use graphene and carbon particles to separate MgO particles in situ to prevent aggregation, so that the surface defects of MgO crystal are fully exposed, forming a strong alkali potential to effectively capture CO_2.. In this paper, two kinds of CO_2 contact methods, "blow sweep method" and "pulse method", are used to combine instantaneous adsorption and programmed temperature desorption to form a new method for the detection of IA-TPD. The contribution of alkali potential of various intensities in adsorbent is calculated from the amount of CO_2 gas introduced, the amount of adsorption and the amount of desorption. The method of in situ carbonization of acetate was applied to the preparation of CaO samples, which provided a new way of green environmental protection for the preparation of high efficiency CO_2 adsorbents. The temperature of industrial flue gas is usually at 423 ~ 673 K. At this temperature, the physical adsorption of solid base CO_2 is difficult, so it is urgent to develop a new high efficient medium temperature CO_2 trapping agent. 3%FM samples were prepared by in-situ carbonization with magnesium acetate, a cheap and easily available precursor. The content of ferrous oxide is only 3%, which meets the needs of green adsorbent preparation. The adsorption capacity of CO_2 at 473K was 35 mg / g ~ (-1). This method improves the ratio of strong alkali potential in MgO particles and is very favorable for capturing CO_2 at 473K, which provides a new idea for the design of high efficiency solid adsorbent for environmental protection.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.4

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