Mesoporous silica （MS）, 3-aminopropyltriethoxysilane （APTES） modified mesoporous silica （AMS）, bis（3- trimethoxysilylpropyl）amine modified mesoporous silica （BAMS） and APTES modified solid spherical silica ...Mesoporous silica （MS）, 3-aminopropyltriethoxysilane （APTES） modified mesoporous silica （AMS）, bis（3- trimethoxysilylpropyl）amine modified mesoporous silica （BAMS） and APTES modified solid spherical silica （AS） were prepared and used to immobilize metallocene catalysts for ethylene polymerization. Gel permeation chromatography results showed that polyethylenes （PEs） catalyzed by AMS （or BAMS） supported metallocene catalysts at the molar ratios of Al/Zr = 100, 300 and 500 were of bimodal molecular weight distribution （BMWD）; while PEs catalyzed by the above catalysts at the molar ratios of Al/Zr 〉 800 were of monomodal molecular weight distribution （MMWD）. However, MS （or AS） supported metallocene catalysts could only produce PEs with MMWD in spite of the molar ratio of Al/Zr. It was because that AMS （or BAMS） supported catalysts possessed two active sites for ethylene polymerization at low molar ratios of Al/Zr due to the combination effects of mesopore geometrical constraint and amino groups of the supports, which was confirmed by X-ray photoelectron spectroscopy. This brings forward a novel and easy method for the synthesis of polyolefin with BMWD.展开更多
A series of unsymmetrical a-diimine nickel complexes with various backbones and substituted aniline moieties were synthesized and characterized. The crystallographic analysis of the nickel complexes confirmed the exis...A series of unsymmetrical a-diimine nickel complexes with various backbones and substituted aniline moieties were synthesized and characterized. The crystallographic analysis of the nickel complexes confirmed the existence of meso-and rac-configuration in solid structure. Nickel complexes after activation by MAO were screened for ethylene polymerization to evaluate backbone substituent effect on synthesis of bimodal PE. Acenaphthyl nickel complex with planar backbone afforded a bimodal PE with a broad polydispersity, whereas camphyl nickel complex with rigid and bulky backbone afforded a monomodal PE with a narrow polydispersity. Steric effect of aniline moiety for acenaphthyl nickel complex was also examined, and bimodal PE with dominant high-molecular-weight fraction was obtained by modifying substituents on aniline moiety.展开更多
基金supported by the National Natural Science Foundation of China(Nos.50525311,20734006 and 50621302)
文摘Mesoporous silica （MS）, 3-aminopropyltriethoxysilane （APTES） modified mesoporous silica （AMS）, bis（3- trimethoxysilylpropyl）amine modified mesoporous silica （BAMS） and APTES modified solid spherical silica （AS） were prepared and used to immobilize metallocene catalysts for ethylene polymerization. Gel permeation chromatography results showed that polyethylenes （PEs） catalyzed by AMS （or BAMS） supported metallocene catalysts at the molar ratios of Al/Zr = 100, 300 and 500 were of bimodal molecular weight distribution （BMWD）; while PEs catalyzed by the above catalysts at the molar ratios of Al/Zr 〉 800 were of monomodal molecular weight distribution （MMWD）. However, MS （or AS） supported metallocene catalysts could only produce PEs with MMWD in spite of the molar ratio of Al/Zr. It was because that AMS （or BAMS） supported catalysts possessed two active sites for ethylene polymerization at low molar ratios of Al/Zr due to the combination effects of mesopore geometrical constraint and amino groups of the supports, which was confirmed by X-ray photoelectron spectroscopy. This brings forward a novel and easy method for the synthesis of polyolefin with BMWD.
基金supported by NSFC (Nos. 21274167, 51173209 and 21174164)CNPC Innovation Foundationthe Fundamental Research Funds for the Central Universities (Project 10lgpy10)
文摘A series of unsymmetrical a-diimine nickel complexes with various backbones and substituted aniline moieties were synthesized and characterized. The crystallographic analysis of the nickel complexes confirmed the existence of meso-and rac-configuration in solid structure. Nickel complexes after activation by MAO were screened for ethylene polymerization to evaluate backbone substituent effect on synthesis of bimodal PE. Acenaphthyl nickel complex with planar backbone afforded a bimodal PE with a broad polydispersity, whereas camphyl nickel complex with rigid and bulky backbone afforded a monomodal PE with a narrow polydispersity. Steric effect of aniline moiety for acenaphthyl nickel complex was also examined, and bimodal PE with dominant high-molecular-weight fraction was obtained by modifying substituents on aniline moiety.
