Effect Of Substitution Of Hyperbranched Nickel Catalysts On The Performance In Ethylene Oligomerization

In this paper,hyperbranched polyamidoamine branch was synthesized using laurylamine,then reacted with 3-methyl salicylaldehyde,3-tert butyl salicylaldehyde,3-methoxy salicylaldehyde respectively via Schiff base reaction,forming hyperbranched salicylaldimine ligands with different substituent groups,which reacted with nickel chloride hexahydrate to obtain hyperbranched salicylaldehyde nickel complexes with different substituents;Infrared spectroscopy,UV spectroscopy,1H NMR spectroscopy(1H-NMR)and electrospray ionization mass spectrometry(ESI-MS)methods were taken to characterize the stuctrues of series of hyperbranched substituted salicylaldimine ligands and series of hyperbranched substituted salicylaldimine nickel complexes.And the behavior of series of hyperbranched substituted salicylaldimine nickel complexes for ethylene oligomerization were studied,and the effect of substituents of the hyperbranched salicylaldimine complexes on the catalytic performance of catalysts was explored.?Using the Methylaluminoxane(MAO),Diethylaluminum chloride(DEAC),sesquiethyl aluminum chloride(EASC)as cocatalysts,toluene as solvent,the performance of series of hyperbranched substituted salicylaldimine nickel complexes for ethylene oligomerization were studied.The results showed that,at Al/Ni 500,pressure 0.5MPa,time 30 min,temperature 25?,the activity of the hyperbranched nickel catalysts were 104 g mol-1 h-1 order of magnitude when using MAO and DEAC as coatalysts while 106 g mol-1 h-1 order of magnitude and when using EASC as cocatalyst and resulting in alkylation by-products for the latter.The study indicated that for all the tree cocatalysts,the acativities of the hyperbranched nickel catalysts in descending order: 3-methoxy catalyst,3-tertbutyl catalyst,3-methyl catalyst.In order to study the reaction mechanism of hyperbranched nickel catalysts and analysize quantitatively the influence of various factors on activity of these catalysts,simple apparent kinetics of the behavior of the hyperbranched nickel catalysts in ethylene oligomerization reaction were sudied,obtaining the apparent reaction oder of pressure,temperature and catalyst concentration,then to eatablish the apparent kinetics equations of the tree catalysts.