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Applied Petrochemical Research

, Volume 3, Issue 3–4, pp 101–105

First Online: 09 October 2013Received: 25 June 2013Accepted: 24 September 2013

Abstract

Bi-nickel-center catalysts were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-di-isopropylaniline; 2-5-butylaniline, 2-isopropylaniline and 1,4-phenylene diamineI. More Schiff-base ligands were prepared by condensation of 2,3-butandione with 2,6-diisopropylaniline; 2,4-6-trimethyl aniline and 4,4-diaminophenyl benzidineII, and subsequent metathesis reaction with DMENiBr2. Bisalpha diiminenickelIIdibromide complexes are suitable catalysts and are precursors for the polymerization of ethylene after activation with methylaluminoxane MAO. In comparison with these complex analogs, mono-nickel-center catalysts, the new catalysts have much bigger molecules, illustrated by the distance between every two active centers II and III. For bi-nickel-center catalysts, the catalyst’s structural credibility had profound influence on the catalytic activity. When the substituent was diisopropyl; t-butyl or methyl, the catalysts demonstrated much higher catalytic activity than the corresponding mono-nickel-center catalysts. Catalyst II with phenyl bridge showed high activity compared with catalyst III with diphenyl bridge. The catalytic properties of these complexes and the character of the obtained polymers depend on the ligand structure of the used catalysts. Substituents on the arene moiety and-or the backbone of the ligand influence the polymerization reaction. Small aryl substituents result in the formation of low molecular weight oligomers, whereas bulky aryl substituents gave high molecular weight polyethylene. Catalysts are cheap and can be prepared easily with available starting material and stable in air. The effect of Al-Ni ratio, of reaction time, variation of ethylene pressure, and the effect of temperature on catalyst performance will be discussed.

KeywordsOrganometallic Polymerizations Late transition metals Ethylene  Download fulltext PDF



Autor: Abdulhamid A. Alsaygh

Fuente: https://link.springer.com/







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