环氧丙烷诱导下介孔氧化铝的控制制备研究

发布时间：2018-02-27 21:06

  本文关键词： 介孔氧化铝 无机铝盐 环氧丙烷 合成 表征　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：本工作以无机铝盐作前驱体,分别采用阳离子季铵盐类表面活性剂(C_nTAB,n=12,14,16,18)和非离子嵌段共聚物(F127,F68,P123和Brij56)作模板剂,在未加酸或碱作pH调节剂的水及非水(乙醇EtOH)体系中,首次通过引入环氧丙烷(PO)作凝胶促进剂,在温和的条件下控制合成了具有不同结构特征的介孔氧化铝材料,并对材料的控制制备规律利用各种表征技术如XRD、N_2吸附、TG、SEM和TEM等进行了系统的研究。具体的研究结果如下:1、在Al(NO_3)3·9H_2O-EtOH-C_nTAB-PO组成的非水体系中,控制合成了比表面积高达456m2/g的具有类γ-Al2O_3相的介孔氧化铝材料。研究发现PO的用量在介孔氧化铝的形成中起着至关重要的作用,过低的PO量将使体系难以凝胶化,而过高的PO量又会使反应自组装的过程无法控制而难以形成有序的介孔氧化铝物相。通过对PO/Al摩尔比的调节可实现材料孔径在3.4~4.8nm范围内的调节。与无模板的空白样相比,模板剂的引入将使材料的比表面积和孔容显著增加。将该方法扩展至F127模板体系,采用40℃敞口凝胶化的方式获得了热稳定性可达800℃的介孔γ-Al2O_3,通过对模板剂种类的调节可实现对材料孔径在4.6~7.8nm范围内的控制。2、在AlCl_3·6H_2O-C_nTAB-H_2O-PO构成的纯水体系中,控制合成了热稳定性高达800℃的孔壁晶化的介孔γ-Al2O_3,研究发现PO/Al的摩尔比在3~7,模板剂浓度在8.08~19.47%范围更有利于有序介孔氧化铝的合成,随着体系中EtOH/H_2O体积比的增加,样品有序性变差。而烷基链长度的改变对材料孔径的影响较小。3、在AlCl_3·6H_2O-H_2O-F127-PO体系中,采用40℃敞口凝胶化程序控制合成了高热稳定且高度有序的介孔γ-Al2O_3材料,实验发现随着PO量或EtOH量的增加,样品的有序性均变差;模板剂浓度可在1.6~9.77%范围内进行有效调节。然而,对孔结构的分析表征却显示该材料的比表面积极低,仅为65m2/g,具有双介孔(3.8nm、6.2nm)分布特征,其原因目前尚不清楚,可能暗示样品在焙烧脱模板过程中介孔孔道发生了部分的闭合,进一步的研究仍在进行中。本工作提出的利用环氧丙烷的开环作用控制合成介孔氧化铝的思想,与已有工作相比,不仅合成过程更加简洁、高效、环保,而且易于实现对材料结构和性能的有效调控,预期这种合成思想可进一步拓展至其它非硅基介孔金属氧化物的合成中去,更为广泛的扩展研究工作已经展开。
[Abstract]:In this work, inorganic aluminum salts were used as precursors, using CnTABN surfactants CnTABN 1214 (16 / 18) and Nonionic block copolymers (F127, F68P123 and Brij56) as templates, respectively, in aqueous and non-aqueous (EtOH) systems without acid or alkali as pH regulators. For the first time, mesoporous alumina materials with different structural characteristics were synthesized under mild conditions by introducing propylene oxide (PO) as gel accelerator. The controlled preparation rules of materials were systematically studied by using various characterization techniques such as TEM and TEM. The specific results are as follows: 1. In the non-aqueous system composed of Al(NO_3)3 路9H _ 2O -EtOH-CnTAB-PO, the main results are as follows: (1) in the non-aqueous system composed of Al(NO_3)3 路9H _ 2O -EtOH-CnTAB-PO, A mesoporous alumina material with 纬 -Al _ 2O _ 3-like phase with a specific surface area of 456m2 / g was synthesized. It was found that the amount of PO played an important role in the formation of mesoporous alumina, and that too low PO content would make it difficult to gel the system. However, the excessive amount of PO can make the reaction self-assembly process uncontrollable and difficult to form an ordered mesoporous alumina phase. The pore size of the material can be adjusted in the range of 3.4 ~ 4.8nm by adjusting the molar ratio of PO/Al. Compared with the blank sample without template, With the introduction of template agent, the specific surface area and pore volume of the material will be significantly increased, and the method will be extended to F127 template system. Mesoporous 纬 -Al _ 2O _ 3 with thermal stability up to 800 鈩，

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