【作者】 昝慧宁；

【导师】 施荣富；

【作者基本信息】 南开大学 ， 高分子化学与物理， 2013， 博士

【摘要】 强碱性阴离子交换树脂广泛应用于水处理、电力行业、生物及化学药剂的分离纯化及催化合成等领域。但是,由于其在水中的热稳定性较低,普通商业强碱性阴离子交换树脂特别是氢氧型阴离子交换树脂的使用温度仅限于60℃以下,这是由于其结构中均含有季铵基团,它是以氯甲基化树脂与叔胺反应得到的。在高温下,季铵基团受到自身结构特点的影响易于发生Hofmann降解反应,造成季铵基的脱落或由强碱基团转变为弱碱基团,大大限制了强碱性阴离子交换树脂的应用。目前针对于强碱阴离子交换树脂耐高温性的改造都是以改变季铵基团与树脂骨架的连接方式,从而间接提高季铵基的热稳定性为主要方向,这些改进方法合成路线较长,生产成本高,更重要的是,受到季铵基团结构的局限,树脂的热稳定性并没有根本得到改善。本论文利用小分子胍具有强碱性、较高的热稳定性、特殊的化学结构特点创新性地将小分子胍基化合物通过两种不同的方法(即直接键联和原位反应)固载到树脂上,合成出一类含有新型功能团结构的强碱阴离子交换树脂,首次对这类胍基树脂的热稳定性进行了详细地研究,总结出胍基树脂热稳定性与树脂功能团连接方式之间的规律,从根本上改变了季铵基团对树脂热稳定性的影响,改善了强碱阴离子交换树脂的热稳定性。为了拓宽强碱胍基耐高温树脂的应用范围,以其作为吸附剂应用到对香菇多糖脱色工艺中,优化了吸附条件；其次将其作为催化剂应用于催化Knoevenagel缩合反应中,考察了耐高温胍基树脂的催化性能,运用多种实验技术对耐高温胍基树脂进行了表征,主要得到了如下具有创新性的结果：第一部分：首次系统研究了树脂热稳定性与树脂固载胍基官能团的连接方式之间的规律。以凝胶氯甲基化树脂为原料通过一步亲核取代反应将分子胍固载到树脂上,合成出胍基树脂,经红外、元素分析、酸碱滴定法测定了树脂的胺基交换量,对其反应条件进行了优化。采用树脂热稳定性测试方法,研究了不同胍基固载量树脂的热稳定性,提出了树脂的稳定性与树脂官能团的连接方式有关,热重分析测试结果也证明了上述结果,合成胍基树脂的热稳定性较商用树脂201热稳定性得到了提高。按照此思路,将二氯甲基苯(XDC)引入树脂中,改善胍基固载量高但热稳定性差的树脂,通过热稳定性和热重分析实验,表明了树脂的热稳定性得以改善,同时验证了上述树脂热稳定性解释的合理性。利用制备的胍基树脂和胍基-XDC树脂作为吸附剂分别考察了其对苯甲酸和甲基橙的吸附行为,树脂对其吸附等温线符合Freundlich模型,对不同的吸附结果进行了解释。第二部分：首次利用胍基官能团与树脂的连接方式,制备出功能基固载量高且热稳定性好的强碱阴离子交换树脂。以凝胶聚苯乙烯苄胺树脂为原料,将分子胍类化合物的原位合成方式应用到树脂合成上,采用两种方法(氰胺法和硫脲法)一步由弱碱阴离子交换树脂转化成为强碱阴离子交换树脂,然后与二氯甲基苯(XDC)反应合成出胍基-XDC强碱阴离子交换树脂,通过红外、酸碱滴定、元素分析、SEM对树脂进行了表征。另外,优化了pH值、投料比、温度等条件,树脂经热稳定性和热失重分析法测定,树脂的耐热性能得到改善,并对其原因进行了解释。为了考察胍基官能团连接方式对其它骨架树脂热稳定性的影响,以丙烯酸树脂骨架和氯乙酰化树脂为原料,将分子胍固载到树脂上,制备得到不同类型连接方式的胍基树脂,并且测定了树脂的热稳定性。第三部分：首次将耐高温胍基树脂作为吸附剂应用于香菇多糖提取液的脱色工艺中。为了拓宽耐高温胍基树脂的应用领域,利用一步原位反应由大孔聚苯乙烯苄胺树脂和单氰胺反应,得到的树脂再与二氯甲基苯(XDC)发生亲核反应制备出大孔型胍基-XDC强碱阴离子交换树脂,树脂经酸碱滴定、元素分析、SEW、N2吸附／脱附表征。通过筛选实验,考察了商品化大孔树脂、阳离子交换树脂、阴离子交换树脂对香菇多糖脱色性能的影响,筛选出胍基-XDC树脂对香菇多糖脱色效果最好,并对其原理进行了解释。在静态吸附实验中,考察了树脂用量、温度、pH值对脱色实验的影响,建立了吸附热力学模型。此外,确定了以胍基-XDC树脂为脱色剂对香菇多糖的动态工艺。第四部分：首次详细探讨了耐高温胍基树脂作为非均相催化剂催化Knoevenagel缩合反应过程。以凝胶型胍基-XDC强碱树脂为催化剂,选择环己酮和氰基乙酸乙酯为反应模板,探讨了反应温度、催化剂用量、反应物配比、反应溶剂、反应时间、反应选择性、树脂重复使用等因素对产率的影响,确定了反应的最佳条件。探讨了以胍基-XDC树脂为催化剂的Knoevenagel缩合反应的机理,并将其应用到不同反应底物的Knoevenagel缩合反应,实验结果表明,该树脂具有良好的催化活性,反应产率达到83.1-95.3%,反应条件温和、后处理简单、产物易于分离、胍基强碱树脂可循环使用,在7次重复实验中,其催化活性基本保持。所有的反应产物经核磁、红外、质谱、气相色谱表征,与文献的结果相一致。更多还原

【Abstract】 Strongly basic anion exchange resin is widely used in water treatment, electric power industry, the separation and purification of biological and chemical agents, as well as catalytic synthesis. However, the temperature range in which conventional strongly basic anion exchange resin, especially in the form of hydroxyl group as counter ion can be applied has an upper limit of60℃due to the resin’s low thermal stability in water. This phenomenon arises as a result of the structure of quaternary ammonium group through the reaction of chloromethylated resin with tertiary amine. The resin having quaternary ammonium group suffers from Hofmann degradation at higher temperatures, leading to the desquamation or conversion of strongly basic groups attached to the polymeric matrix. Therefore, the application of strongly basic anion exchange resin is greatly limited. At present, many efforts have been devoted to improving the thermal stability of polymeric resins by modification of the linkage between the quaternary ammonium groups and the polystyrene. However, it has been concluded that such modifications would not be economical for application to large-scale preparations because of the complicated synthetic processes required. Moreover, although these methods lead to slight improvements, it is difficult to fundamentally enhance the thermal stability due to the inherent nature of the quaternary ammonium group.Small molecule guanidine has the advantage of strong alkalinity, high thermal stability, special chemical structure, which has been applied to immobilize onto the resin innovatively through two different methods (namely direct immobilization and the in situ reaction) to afford novel guanidine resin. In the thesis, the thermal stability of the guanidine resin synthesized was studied in detail, for the first time, summing up the rule between thermal stability and the connection mode. The resin synthesized changed the influence of quaternary ammonium groups on the thermal stability of resin, improving the thermal stability of the strong-base anion exchange resin. The applications of guanidine resin both as adsorbent in lentinan decoloring process and as catalyst in catalyzing Knoevenagel condensation reaction were also investigated. The main research contents and conclusions are as follows:Part I:The connection mode between thermal stability and guanidine groups was study for the first time. The guanidine resins were prepared by the nucleophilic substitution reaction of free guanidine and gel chloromethylated resin as the raw material. The guanidine resins were characterized by FT-IR, TQ and the contents of the basic functional groups bound to the resin were determined by acid-base titration and elemental analysis. The reaction conditions were optimized. It was shown that the thermal stability of the resin was inversely proportional to the amounts of guanidine groups attached on the resin, which was confirmed by thermogravimetric analysis. The more stable guanidine resin was, the lower contents of guanidine resin were. It can be attributed to the unique structure of guanidine and the cross-linking connection mode between the guanidine and the polymeric matrix. According to the explanation to the result, p-xylylene dichloride (XDC) was selected as a post-synthesis cross-linking agent to react with guanidine incorporated into the resin in order to improve thermal stability of resin with high contents of guanidine groups. The experiment result was demonstrated that the thermal stability of resin had been improved, which verified the above explanation in the meanwhile. The adsorption performance of guanidine resin and guanidine-XDC resin were both studied. The benzoic acid and methyl orange were selected as adsorbates. Experimental results were showed that the isotherms could be represented by Freundlich model reasonably. The adsorption mechanism indicated that the adsorption was the synergistic effect of hydrophobic interaction, dipole-dipole interaction and hydrogen bonding.Part II:To obtain a thermally stable resin with high contents of guanidine groups loaded, gel benzylamine polystyrene had been allowed to react nucleophilic addition with cyanamide or thiourea in situ to generate strongly basic resin from weak basic one, followed by the reaction with p-xylylene dichloride (XDC) to give guanidine-XDC resin. The resins synthesized were determined by FT-IR, acid-base titration, elemental analysis and SEM. The effects of pH value, material ratio and temperature on the reaction were also investigated. The experiment results had been indicated that the resin had good thermal stability. At the same time, different types of guanidine resins were prepared by the reaction of the resins having different matrixes, as raw materials, with free guanidine.Part III:The guanidine resin as the adsorbent was, for the first time, applied in lentinan decoloring process. The macroporous guanidine-XDC resin had been prepared through the one-step reaction of primary amine resin with cyanamide, followed by the reaction with p-xylylene dichloride (XDC) to obtain macroporous resin with guanidine groups. The resins synthesized had been characterized by acid-base titration, elemental analysis, SEM and N2adsorption-desorption experiments. Under the same conditions, guanidine resins, commercial cation exchange resins, commercial anion exchange resins, macroporous resins were screened to carry out the decolorization of lentinan. It was shown that guanidine-XDC resin had the best decoloring efficiency, which had been explained using the corresponding principle. The static adsorption experiments of the lentinan on guanidine-XDC resin were performed under different temperature, amounts of the resin, pH value, and were set up the adsorption thermodynamics model. Besides, the technology on the decolorization of lentinan were studied.Part IV:The Knoevenagel condensation reaction catalyzed by gel guanidine-XDC resin as heterogeneous catalyst had been investigated for the first time. The effect of reaction temperature, amounts of the resin, ratio of reactants, reaction solvent, reaction time, reaction selectivity, reusability on the Knoevenagel condensation reactions between cyclohexane and ethyl cyanoacetate were also discussed. The catalytic mechanism had been proposed. The guanidine-XDC resin had been found to efficiently catalyze Knoevenagel condensation reactions with the yield of83.1-95.3%, and even the reactions of relatively inactive substrates can be accomplished at higher temperatures. The resin can be removed after reaction by simple filtration with the advantages of easy separation, mile reaction condition, recyclability without losing catalytic activity more than7times. All the reaction products were characterized by NMR, FT-IR, MS, GC, which were consistent with the literature results.更多还原