膨润土的改性及其催化酯化反应的研究

发布时间：2018-06-30 21:17

  本文选题：膨润土改性 + 催化剂　； 参考：《湘潭大学》2016年硕士论文

【摘要】：膨润土(Bent)是一种以蒙脱石为主要成分的天然矿物材料,因其特殊的结构和独特的化学组成而具有较大的比表面积和较高的热稳定性,常用作各种环境友好型催化剂的载体。为了使载体具有更大的比表面积和更高的热稳定性,往往需要对天然膨润土进行纯化以去掉杂质得到高含量的蒙脱石,然后通过负载等手段制得不同类型的固体催化剂。这种以膨润土作为载体的催化剂与传统的液相催化相比,具有制备成本低、催化活性高、易分离和可多次循环使用的优点,是一种有广泛应用前景的绿色催化剂。本文以纯化酸化后的膨润土为载体,制备出负载磷钨酸、钛交联、羟基铁铝柱撑三种催化剂,并通过FTIR、XRD、SEM、TG、BET等手段对其结构与形貌加以表征,研究了三种催化剂对不同酯化反应的催化性能。主要内容如下:1.以纯化酸化膨润土为载体,Ti(n-C4H9O)4为钛源,采用溶胶-凝胶法将二氧化钛与蒙脱石交联,得到了比表面积为243.3094 m2.g-1,总孔体积为0.20296cm3.g-1,且热稳定高的(640℃结构不改变)钛交联催化剂(Ti-PILC)。同时,对催化剂催化谷氨酸卞酯的产率进行研究。结果表明,钛交联蒙脱石具有优良的催化性能,谷氨酸卞酯的产率最高可达77.9%[n(谷氨酸):n(苯甲醇)=1:6,温度:60℃,反应回流时间:2 h,催化剂用量占反应物总质量的8%]。这也为其在固体酸催化领域的应用提供了借鉴。2.采用浸渍蒸发法制备酸化蒙脱石负载不同量的磷钨酸催化剂(HPW/AAB)。通过XRD,IR,SEM等对催化剂进行表征分析,结果显示,负载后的催化剂具有Keggin结构。对棕榈酸甲酯的催化性能研究表明,在反应温度为65℃,醇酸比为25:1时,磷钨酸负载量为20%,反应6 h时,催化效率最佳产率达到了87.2%。同时,反应后的催化剂容易分离。六次重复使用后的催化效率依然保持95%。3.本章使用Fe-Al柱撑蒙脱石,考察了不同条件对柱撑蒙脱石性质的影响及其在催化油酸酯化的反应中,对其产率的影响。结果表明,在500℃时柱撑蒙脱石仍有良好的热稳定性。500℃以后,XRD图谱中d001峰降低,说明热稳定性变差,红外图谱中也有一些峰消失。结果显示,在温度80℃,焙烧温度500℃,催化剂为原料总质量的1.5%,反应时间8 h,反应醇酸摩尔比为9:1时油酸乙酯的产率达到最大86.7%。该方法简单易得,原料成本也低。
[Abstract]:Bentonite (Bent) is a kind of natural mineral material with montmorillonite as its main component. Because of its special structure and unique chemical composition, bentonite has large specific surface area and high thermal stability. Bent is often used as the carrier of various environment-friendly catalysts. In order to make the carrier have larger specific surface area and higher thermal stability, it is often necessary to purify natural bentonite in order to get high content of montmorillonite by removing impurities. Compared with the traditional liquid phase catalyst, this kind of catalyst with bentonite as the carrier has the advantages of low preparation cost, high catalytic activity, easy separation and multiple recycling. It is a green catalyst with wide application prospect. In this paper, supported phosphotungstic acid, titanium cross-linking and hydroxy-iron-aluminum pillared catalysts were prepared by using purified acidified bentonite as carrier, and their structure and morphology were characterized by FTIR, XRDX, SEM, TGG-BET, etc. The catalytic properties of three catalysts for different esterification reactions were studied. The main content is as follows: 1. Using purified acidified bentonite as carrier Ti (n-C _ 4H _ 9O) _ 4 as titanium source, titanium dioxide and montmorillonite were crosslinked by sol-gel method. The specific surface area was 243.3094 m2.g-1, the total pore volume was 0.20296 cm 3.g-1, and the structure of Ti-PILC was high (640 鈩，

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