乙炔氢氯化制氯乙烯无汞催化剂的研究

发布时间：2018-06-14 08:59

  本文选题：乙炔氢氯化 + 汞替代　； 参考：《中国科学技术大学》2017年博士论文

【摘要】：当前工业上,乙炔法生产氯乙烯过程仍依靠氯化汞催化剂,然而,氯化汞高毒,在反应条件下易被还原成金属态汞导致挥发,为环境和人类健康带来了巨大压力。在中国大量应用乙炔法生产氯乙烯的国情下,汞催化剂的替代问题亟待解决。本论文围绕这个问题,开发了两种无金属的非汞催化剂,表现出优异的催化活性和氯乙烯选择性,以及稳定性,具有一定的应用前景。对碳氮基催化剂的工业应用进行了前期探索,尤其放大制备和反应性能的评价,取得了一定成果;研究了不同非金属催化剂的反应机理和失活原因,开发了简单的再生方法。主要研究内容和结果如下:1.氮掺杂的碳催化剂的研制。以葡萄糖为原料,通过水热聚合和高温氨化制备所得。催化剂具有丰富的微孔结构和高的氮掺杂量(10 wt. %以上)。催化剂表现出良好的催化乙炔氢氯化反应的能力,在给定反应条件下,乙炔转化率可达80-90%以上,氯乙烯的选择性95%左右;催化剂在200℃稳定反应300 h以上,反应至600 h其转化率下降至85%;催化剂失活的主要原因为积碳,可以通过在较低温度下(300℃)空气中焙烧,再转移至氨气中焙烧(450℃)实现再生,再生后的催化剂初始转化率80%以上(所用失活催化剂的活性降低至10%以下);2.催化剂在企业工况下的性能。在同样乙炔空速条件下,通过提高催化剂装填量,可增加反应气体线速度,减少外扩散阻力,提高催化性能。在较高线速度条件下,反应温度可适当降低,在维持催化活性的前提下减缓反应积碳,延长催化剂稳定性。通过降低反应温度至180℃,提高催化剂装填量,其稳定性可延长至900 h,期间无显著失活现象;3.多孔氮化硼p-BN催化剂的研制。(1)材料制备和结构:以硼酸和三聚氰胺为原料,高温反应获得多孔氮化硼,该材料呈六方氮化硼结构,具有高的比表面积,丰富的孔结构(微孔和介孔),丰富缺陷和边界;(2)催化性能:反应结果表明,催化剂在280℃时乙炔转化率可达99%,氯乙烯选择性99%,连续反应1000 h左右失活较为缓慢,乙炔转化率缓慢降至95%,综合性能优于碳氮材料;(3)催化作用机理及失活原理和再生:研究发现催化剂失活原因为积碳;积碳可通过在较低温度的空气气氛中烧除,烧除积碳后的材料在氨气气氛高温活化后可实现再生。结合DFT计算,发现氮化硼的扶手椅边界具有催化活性,反应遵循Eley-Rideal反应机制,通过吸附活化乙炔实现催化活化;通过动力学模拟,提出了可能的反应路径,其过程可能涉及一个类似碳正离子的中间物种的形成。
[Abstract]:At present, the production of vinyl chloride by acetylene process still relies on mercuric chloride catalyst. However, mercuric chloride is highly toxic and can easily be reduced to metallic mercury under reaction conditions, resulting in volatilization, which brings great pressure to environment and human health. In China, the substitution of mercury catalyst for vinyl chloride production by acetylene process needs to be solved. In this paper, two kinds of non-mercury-free catalysts without metal have been developed, showing excellent catalytic activity and vinyl chloride selectivity, as well as stability, and have a certain application prospect. The industrial application of carbonitrogen-based catalysts has been explored, especially in the preparation and evaluation of the reaction performance. The reaction mechanism and deactivation of different non-metallic catalysts have been studied, and a simple regeneration method has been developed. The main contents and results are as follows: 1. Development of nitrogen-doped carbon catalyst. Glucose was prepared by hydrothermal polymerization and high temperature ammoniation. The catalyst has abundant micropore structure and high nitrogen doping amount more than 10 wt.%. Under given reaction conditions, the conversion of acetylene is over 80-90%, the selectivity of vinyl chloride is about 95%, and the catalyst is stable at 200 鈩，

本文编号：2016828