A novel catalytic system to prepare branched polyethylene with single catalyst activated by two different co-catalysts is reported in this paper via the tandem catalysis,with ethylene as single monomer.Such catalytic ...A novel catalytic system to prepare branched polyethylene with single catalyst activated by two different co-catalysts is reported in this paper via the tandem catalysis,with ethylene as single monomer.Such catalytic system is composed of β-diketonate zirconium complexes,i.e.(acac)2ZrCl2(Ⅰ)and(dbm)2ZrCl2(Ⅱ)as catalyst precursors,diethylaluminium chloride(AlEt2Cl)as a co-catalyst for ethylene oligomerization and methylaluminoxane(MAO)as another one for the in situ copolymerization with ethylene.The oligomers obtained were mainly α-olefins,and the contents of them in weight were 76.84 for Ⅰ and 65.99 for Ⅱ,while the part being able to be copolymerized was 62.12 and 55.32 for Ⅰ and Ⅱ,respectively.The branched polyethylene via in situ copolymerization of ethylene was prepared by the tandem catalytic system Ⅰ/AlEt2Cl/MAO or Ⅱ/AlEt2Cl/MAO.13C NMR spectrum reveals that the resultant copolymer was branched polyethylene with total branches of 2.1/1000C,including ethyl group of 1.2/1000C,butyl group of 0.8/1000C and longer branches of 0.1/1000C.With increasing the molar ratio of AlEt2Cl to MAO,the melting temperature of the polymer obtained decreased from 133.7 to 116.7 ℃ for Ⅰ/AlEt2Cl/MAO and from 131.7 to 118.8 ℃ for Ⅱ/AlEt2Cl/MAO as well as the change of crystallinity.The catalytic activities for catalyst Ⅰ/AlEt2Cl/MAO and Ⅱ/AlEt2Cl/MAO were from 2.48×104 to 0.10×104 g PE/(mol Zr·h)and from 1.00×104 to 0.32×104 g PE/(mol Zr·h),respectively.The results indicate that the branched polyethylene can be obtained by such a catalytic system.展开更多
文摘A novel catalytic system to prepare branched polyethylene with single catalyst activated by two different co-catalysts is reported in this paper via the tandem catalysis,with ethylene as single monomer.Such catalytic system is composed of β-diketonate zirconium complexes,i.e.(acac)2ZrCl2(Ⅰ)and(dbm)2ZrCl2(Ⅱ)as catalyst precursors,diethylaluminium chloride(AlEt2Cl)as a co-catalyst for ethylene oligomerization and methylaluminoxane(MAO)as another one for the in situ copolymerization with ethylene.The oligomers obtained were mainly α-olefins,and the contents of them in weight were 76.84 for Ⅰ and 65.99 for Ⅱ,while the part being able to be copolymerized was 62.12 and 55.32 for Ⅰ and Ⅱ,respectively.The branched polyethylene via in situ copolymerization of ethylene was prepared by the tandem catalytic system Ⅰ/AlEt2Cl/MAO or Ⅱ/AlEt2Cl/MAO.13C NMR spectrum reveals that the resultant copolymer was branched polyethylene with total branches of 2.1/1000C,including ethyl group of 1.2/1000C,butyl group of 0.8/1000C and longer branches of 0.1/1000C.With increasing the molar ratio of AlEt2Cl to MAO,the melting temperature of the polymer obtained decreased from 133.7 to 116.7 ℃ for Ⅰ/AlEt2Cl/MAO and from 131.7 to 118.8 ℃ for Ⅱ/AlEt2Cl/MAO as well as the change of crystallinity.The catalytic activities for catalyst Ⅰ/AlEt2Cl/MAO and Ⅱ/AlEt2Cl/MAO were from 2.48×104 to 0.10×104 g PE/(mol Zr·h)and from 1.00×104 to 0.32×104 g PE/(mol Zr·h),respectively.The results indicate that the branched polyethylene can be obtained by such a catalytic system.
