(NH_4)_2SO_4改性Cr/V双金属催化剂的制备及乙烯聚合研究

Preparation of(NH_4)_2SO_4 modified Cr/V bimetallic catalyst and its application in ethylene polymerization

在Phillips催化剂基础上开发出CrOx-VOx/SiO_2双中心催化剂,并用(NH_4)_2SO_4对其进行改性,考察了(NH_4)_2SO_4的浸渍方式、浸渍量和催化剂焙烧温度对乙烯聚合行为和产物结构与性能的影响。结果表明,(NH_4)_2SO_4改性的铬钒双金属催化剂的乙烯聚合活性得到提高,且随(NH_4)_2SO_4负载量的增加,活性呈现先增加后降低的趋势。采用共浸渍制备的催化剂的乙烯聚合活性大于分布浸渍法。(NH_4)_2SO_4对V活性组分有促进作用,使改性催化剂的均聚产物分子质量增加,加入1-己烯共聚单体后,分子质量进一步增加。

A Cr Ox-VOx/Si O2 bimetallic catalyst is developed on the basis of Phillips catalyst and modified with(NH4)2SO4.The influences of calcination temperature for catalyst,and impregnation method and amount of(NH4)2SO4 on polymerization behavior of ethylene and properties of product are investigated. The results show that the addition of(NH4)2SO4 helps Cr Ox-VOx/Si O2 bimetallic catalyst improve activity in ethylene polymerization. With the increase of(NH4)2SO4 dosage,the activity of the catalyst increases first and decreases then.The activity of the catalyst prepared by co-impregnation method is greater than that made by distribution impregnation method.(NH4)2SO4 can promote V active site and hence increases the molecular weight of homopolymer produced.The addition of 1-hexene can further increase the molecular weight of homopolymer.