加压条件下无机铬钒双中心乙烯聚合催化剂及其烷基铝预还原研究

发布时间：2018-02-15 22:52

本文关键词： 铬钒双中心 Phillips催化剂乙烯聚合烷基铝预还原　出处：《华东理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚乙烯是目前世界上应用最广泛,使用量最大的高分子聚合材料。虽然我国近年来聚乙烯总产能不断提升,但是高附加值的高等级双峰聚乙烯国内产能依旧不足,大幅度依赖于进口。而且随着我国的经济不断发展,双峰聚乙烯的缺口也在进一步扩大。又由于近年来对节能减排的高要求,相比于现在主流的双釜双峰工艺,在单反应器中直接生产双峰聚乙烯的工艺拥有显著优势,因此对应催化剂的研发很重要。本文研究了之前在传统Phillips铬系催化剂基础上开发的无机铬钒双中心催化剂在加压条件下的聚合性能同时进一步使用烷基铝对无机铬钒双中心催化剂进行预还原研究。通过对加压条件下的乙烯均聚和与1-己烯的共聚行为及聚合产物比较,研究催化剂的制备方式,聚合温度,钒含量,助催化剂浓度,催化剂种类和预还原剂种类等因素对催化性能的影响。实验结果表明,在实验的加压条件下(0.4MPa),共浸渍和分步浸渍醋酸铬和偏钒酸铵制备的双中心催化剂在聚合活性和产物性能上并没有显著差异,考虑到更简单的步骤和操作以及工业生产中较低的生产和设备费用,共浸渍法是较优的选择。比较了共浸渍制备的不同钒金属含量的双中心催化剂的聚合活性,确定催化剂的最佳铬钒比为1:1之后分别选用三乙基铝(TEA)和三异丁基铝(TIBA)作为助催化剂以及预还原剂对该双中心催化剂进行研究。以TEA与TIBA作为预还原剂的催化剂在聚合过程中助催化剂的用量大大降低。使用相同助催化剂时,这两种催化剂聚合活性的高低和变化趋势基本一致,得到的产品分子量高低和分子量分布宽窄基本相同,说明TEA和TIBA的预还原效果相近。同时预还原后催化剂共聚产物的1-己烯插入率显著提高,体现出催化剂预还原处理的独特优势。
[Abstract]:Polyethylene is the most widely used and used polymer polymeric material in the world at present. Although the total production capacity of polyethylene in China has been increasing in recent years, the domestic production capacity of high-grade bimodal polyethylene with high added value is still insufficient. The gap of bimodal polyethylene is also expanding with the economic development of our country. And because of the high demand for energy saving and emission reduction in recent years, compared with the current mainstream double-pot bimodal process, The process of producing bimodal polyethylene directly in a single reactor has significant advantages. Therefore, the development of corresponding catalysts is very important. In this paper, the polymerization performance of inorganic chromium vanadium double center catalysts developed on the basis of traditional Phillips chromium system catalysts under pressure and the further use of alkyl aluminum to inorganic materials were studied. The prereduction of Cr-V double center catalyst was studied. The copolymerization behavior and polymerization products of ethylene homopolymer and 1-hexene under pressure were compared. The effects of preparation method, polymerization temperature, vanadium content, cocatalyst concentration, type of catalyst and type of prereductant on the catalytic performance were studied. Under the experimental pressure of 0.4MPA, there was no significant difference in the polymerization activity and the properties of the products prepared by co-impregnation and stepwise impregnation of chromium acetate and ammonium metavanadate. In view of simpler steps and operations and lower production and equipment costs in industrial production, co-impregnation is the preferred choice. The polymerization activity of bicentral catalysts with different vanadium metal contents prepared by co-impregnation is compared, When the optimum Cr / V ratio of the catalyst was 1: 1, triethylaluminotriethylaluminotrimethylammonium (TIBA) and triisobutyl aluminum (TIBA) were used as cocatalysts and pre-reductant respectively. The binocentral catalyst was studied with TEA and TIBA as prereductants. The amount of cocatalyst is greatly reduced during polymerization. When the same cocatalyst is used, The polymerization activity of the two catalysts is basically the same as the change trend, and the molecular weight and the molecular weight distribution of the products obtained are basically the same. The results show that the prereduction effect of TEA and TIBA is similar, and the insertion rate of 1-hexene in the copolymerized product of the catalyst after prereduction is improved significantly, which shows the unique advantage of the pre-reduction treatment of the catalyst.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ325.12;O643.36

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