材料期刊网

采用化学反应法，以氯化镁、醇化合物以及Ti和Hf化合物等为原料，制备了新型Ti-Hf双金属载体催化剂．乙烯聚合结果表明所得载体催化剂具有良好的催化活性，所得聚合产物呈现良好的颗粒形态．与在相同条件下制备的只含Ti的催化剂相比较，Ti-Hf双金属载体催化剂具有更良好的综合性能且生成分子量更高、分子量分布更宽的聚乙烯，在乙烯-丁烯共聚中可生成密度更低的乙烯共聚物．产物的熔流比随H2气分压的增加而降低．结合GPC观察的结果，表明Ti活性中心生成低到中等分子量的聚乙烯，而Hf活性中心生成高分子量的聚乙烯．因此新型双金属催化剂可以用于合成宽分子量分布的聚乙烯及其共聚物．

Titanium and hafnium bimetallic catalyst prepared by chemical reaction method usingMgCl2 as support shows a high activity and good polymer particle size distribution. Compared withcatalyst containing only titanium, the titanium-hafnium bimetallic catalyst exhibits better performanceand produces polyethylenes with higher molecular weight and wider molecular weight distribution andgives lower density copolymer of ethylene with butene-1. The MFR values of polyethylene obtaineddecrease with increase in partial hydrogen pressure. High molecular weight shoulders in GPC profiledemonstrates that moderate or low molecular weight polyethylene is due to the titanium species whilethe hafnium active species produce high molecular weight polyethylene. This bimetallic catalyst issuggested to have a promising application in production of polyethylenes with broad molecular weightdistributions.