亚临界水中废弃铸型尼龙非均相催化降解的研究
发布时间：2018-08-06 19:58
【摘要】：铸型尼龙(Monomer casting nylon,MC尼龙)是一种优质的聚酰胺类工程塑料,但伴随着相关制品应用需求的增长,废弃的MC尼龙对环境保护及资源再利用的压力也在与日俱增。在众多废弃材料的再资源化方法中,亚临界水技术由于具有传质性能好、扩散系数高以及来源绿色等特质,在聚合物材料的回收领域中拥有巨大的应用潜力。然而在现有的聚酰胺类材料水解的研究工作中,缺乏对降解具体反应过程和提高降解效率技术的详细分析。基于以上背景,本文研究了废弃MC尼龙在亚临界水中的降解反应,并通过引入不同类型的非均相催化剂实现了提高水解反应效率、降低能耗并避免二次污染的目标。本文在无催化剂添加的条件下对MC尼龙水解的反应产物进行了定性分析,并在此基础上进一步研究了影响水解度和单体产率的主要因素。在完善MC尼龙水解反应过程的研究后,进而提出了其在亚临界水中的降解机理。MC尼龙在亚临界水环境中可以完全降解为水溶性低聚物和单体己内酰胺(ε-caprolactam,CPL)。在其水解过程中,原料完全降解之前的固相残余物为未分解完全的尼龙,随着水解的进行残余MC尼龙的含量逐渐减少,热稳定性不断下降,颗粒尺寸也随水解时间的增加持续减小。作为水解反应的中间产物,水溶性的环状及线型低聚物在液相中通过进一步的断链及脱水反应生成目标单体CPL。通过低聚物的逐步解聚反应,单体CPL在345℃亚临界水中的最高产率可达85%以上。为了提高水解效率并克服传统均相催化剂分离困难和严重腐蚀设备等弊端,本文从来源广泛、制备简易、绿色环保等方面考虑,制备了γ-Al_2O_3负载型固体酸催化剂并评价了它们在MC尼龙水解反应中的催化性能。研究发现,在此系列非均相催化剂中,SO_4~(2-)/ZrO_2/γ-Al_2O_3(AZS1)固体酸催化剂由于酸性较强,对MC尼龙的降解催化效果最为显著。当水解反应条件为温度320℃、时间30 min时,使用AZS1可使MC尼龙水解度由无催化反应时的28%增加至51%,单体CPL产率提高4倍以上。根据反应过程及单体增长趋势研究,本文建立了由两个连续的一级反应步骤组成的动力学模型。通过动力学分析显示,与无催化反应相比,AZS1可有效提升不同水解步骤的反应速率常数并降低其表观活化能。高效稳定的非均相催化剂能够与亚临界水技术协同实现废弃聚合物材料的高产出低投入式回收,而固体酸AZS1的循环使用能力有待提高,所以本文选取并研究了水热稳定性较好的H型沸石分子筛在MC尼龙水解反应中的催化行为。在一系列不同孔道结构的沸石分子筛中,H-Beta-25分子筛由于较大的孔径及丰富的强酸位点展现了最为优异的催化水解性能。在同样的水解条件下(320℃,30 min)时,单体产率与无催化反应相比可以提高7倍以上,甚至优于固体酸AZS1。MC尼龙的酸催化水解遵循正碳离子反应机理,但是具有不同结构的催化剂所对应的催化水解进程略有差异。与AZS1相比,H-Beta-25沸石分子筛主要通过提高特定结构中间产物的形成与消耗速度来促进MC尼龙的水解。此外H-Beta-25在水热环境中催化性能更为稳定,是一种较为理想的聚酰胺材料水解用非均相催化剂。
[Abstract]:Monomer casting nylon (MC nylon) is a high quality Polyamide Engineering plastic, but with the increasing demand for related products, the pressure of waste MC nylon on environmental protection and resource reuse is increasing day by day. In the reresource method of many waste materials, the subcritical water technology has the mass transfer performance. Well, high diffusion coefficient and green source have great potential for application in the field of polymer recovery. However, in the current research work on the hydrolysis of polyamide materials, the detailed analysis of the specific degradation process and the technology of improving the degradation efficiency is lack. Based on the above background, the waste MC nylon is studied in this paper. The degradation reaction of subcritical water was carried out by introducing different types of heterogeneous catalysts to improve the efficiency of hydrolysis, reduce energy consumption and avoid two times of pollution. In this paper, the product of hydrolysis of MC nylon was qualitatively analyzed under the condition of no catalyst addition, and on this basis, the hydrolysis of hydrolysis was further studied. The main factors of degree and monomer yield. After improving the hydrolysis process of MC nylon, the degradation mechanism of.MC nylon in subcritical water can be completely degraded into water-soluble oligomers and monomer caprolactam (epsilon -caprolactam, CPL) in the subcritical water environment. As the residual MC nylon content decreases gradually with the hydrolysis, the thermal stability decreases and the particle size decreases with the increase of hydrolysis time. As the intermediate product of the hydrolysis reaction, the water-soluble ring and linear oligomers are in the liquid phase through further chain breaking and dehydration reaction. The maximum yield of monomer CPL in subcritical water at 345 degrees centigrade can reach more than 85% through gradual depolymerization of oligomer CPL.. In order to improve hydrolysis efficiency and overcome the disadvantages of traditional homogeneous catalyst separation and serious corrosion equipment, this paper has prepared gamma -Al_2O_3 from a wide range of sources, preparation and green environmental protection. The catalytic performance of the supported solid acid catalysts in the hydrolysis of MC nylon was evaluated. It was found that, in this series of heterogeneous catalysts, SO_4~ (2-) /ZrO_2/ gamma -Al_2O_3 (AZS1) solid acid catalyst has the most remarkable catalytic effect on the degradation of MC nylon because of its strong acidity. When the hydrolysis reaction conditions are 320 C, 30 min time. The use of AZS1 can increase the degree of hydrolysis of MC nylon from 28% to 51% and increase the yield of monomer CPL by 4 times. Based on the reaction process and the growth trend of the monomer, a kinetic model composed of two successive first order reactions is established. The dynamic analysis shows that AZS1 can be effective compared with the non catalytic reaction. The reaction rate constant of different hydrolysis steps is improved and its apparent activation energy is reduced. The high efficiency and stable heterogeneous catalyst can be used in collaboration with subcritical water technology to achieve high yield and low input recovery of waste polymer materials, while the recycling ability of solid acid AZS1 needs to be improved. The catalytic behavior of H zeolite molecular sieves in the hydrolysis of MC nylon. In a series of different pore structure zeolite molecular sieves, H-Beta-25 molecular sieves exhibit the most excellent catalytic hydrolysis performance due to the larger pore size and rich acid sites. Under the same hydrolysis conditions (320, 30 min), the monomer yield and the non catalytic reaction Compared with the solid acid AZS1.MC nylon, the acid catalyzed hydrolysis follows the mechanism of the positive carbon ion reaction, but the catalytic hydrolysis process corresponding to the catalysts with different structures is slightly different. Compared with AZS1, H-Beta-25 zeolite molecular sieve is mainly by improving the formation and consumption rate of the intermediate products of the specific structure. In addition, H-Beta-25 is more stable in hydrothermal environment and is an ideal heterogeneous catalyst for hydrolysis of polyamide.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X705;O643.32
本文编号：2168830
[Abstract]:Monomer casting nylon (MC nylon) is a high quality Polyamide Engineering plastic, but with the increasing demand for related products, the pressure of waste MC nylon on environmental protection and resource reuse is increasing day by day. In the reresource method of many waste materials, the subcritical water technology has the mass transfer performance. Well, high diffusion coefficient and green source have great potential for application in the field of polymer recovery. However, in the current research work on the hydrolysis of polyamide materials, the detailed analysis of the specific degradation process and the technology of improving the degradation efficiency is lack. Based on the above background, the waste MC nylon is studied in this paper. The degradation reaction of subcritical water was carried out by introducing different types of heterogeneous catalysts to improve the efficiency of hydrolysis, reduce energy consumption and avoid two times of pollution. In this paper, the product of hydrolysis of MC nylon was qualitatively analyzed under the condition of no catalyst addition, and on this basis, the hydrolysis of hydrolysis was further studied. The main factors of degree and monomer yield. After improving the hydrolysis process of MC nylon, the degradation mechanism of.MC nylon in subcritical water can be completely degraded into water-soluble oligomers and monomer caprolactam (epsilon -caprolactam, CPL) in the subcritical water environment. As the residual MC nylon content decreases gradually with the hydrolysis, the thermal stability decreases and the particle size decreases with the increase of hydrolysis time. As the intermediate product of the hydrolysis reaction, the water-soluble ring and linear oligomers are in the liquid phase through further chain breaking and dehydration reaction. The maximum yield of monomer CPL in subcritical water at 345 degrees centigrade can reach more than 85% through gradual depolymerization of oligomer CPL.. In order to improve hydrolysis efficiency and overcome the disadvantages of traditional homogeneous catalyst separation and serious corrosion equipment, this paper has prepared gamma -Al_2O_3 from a wide range of sources, preparation and green environmental protection. The catalytic performance of the supported solid acid catalysts in the hydrolysis of MC nylon was evaluated. It was found that, in this series of heterogeneous catalysts, SO_4~ (2-) /ZrO_2/ gamma -Al_2O_3 (AZS1) solid acid catalyst has the most remarkable catalytic effect on the degradation of MC nylon because of its strong acidity. When the hydrolysis reaction conditions are 320 C, 30 min time. The use of AZS1 can increase the degree of hydrolysis of MC nylon from 28% to 51% and increase the yield of monomer CPL by 4 times. Based on the reaction process and the growth trend of the monomer, a kinetic model composed of two successive first order reactions is established. The dynamic analysis shows that AZS1 can be effective compared with the non catalytic reaction. The reaction rate constant of different hydrolysis steps is improved and its apparent activation energy is reduced. The high efficiency and stable heterogeneous catalyst can be used in collaboration with subcritical water technology to achieve high yield and low input recovery of waste polymer materials, while the recycling ability of solid acid AZS1 needs to be improved. The catalytic behavior of H zeolite molecular sieves in the hydrolysis of MC nylon. In a series of different pore structure zeolite molecular sieves, H-Beta-25 molecular sieves exhibit the most excellent catalytic hydrolysis performance due to the larger pore size and rich acid sites. Under the same hydrolysis conditions (320, 30 min), the monomer yield and the non catalytic reaction Compared with the solid acid AZS1.MC nylon, the acid catalyzed hydrolysis follows the mechanism of the positive carbon ion reaction, but the catalytic hydrolysis process corresponding to the catalysts with different structures is slightly different. Compared with AZS1, H-Beta-25 zeolite molecular sieve is mainly by improving the formation and consumption rate of the intermediate products of the specific structure. In addition, H-Beta-25 is more stable in hydrothermal environment and is an ideal heterogeneous catalyst for hydrolysis of polyamide.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X705;O643.32
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