Ethylene Oligomerization Catalyzed By Transition Metal Complexes

The discovery of the metallocene MAO catalysts has broken a new ground in organometallics chemistry and polymer synthesis. The activity of zirconocene with MAO for polymerization reaches 1 00 tons of ethylene per gram of zirconium per hour. In recent years, the discovery of late transition metal catalysts led to new revolution on polymer domain after metallocene catalysts. The activity of iron complex with MAO for polymerization is as high as 330 tons of ethylene per mole of iron per hour. There is a close relationship between polymerization and oligomerization. We studied the oligomerization of ethylene catalyzed by indyl zirconium catalysts, including the effect of reaction temperature, aging temperature, main catalysts, cocatalysts and reaction time. Ethylene oliogomerization catalyzed by late transition metal catalysts has, also been researched. The effect of main catalysts on ethylene oligomerization has been studied. The catalytic activities of Ind2Zr(OAr)2/Et2AICF were moderate and they displayed high selectivities to low carbon linear x-olefins under optimal reaction conditions. The precatalyst with an electron donating group is better than that without electron donating group and indyl group is also better than cyclopentanyl group on ethylene oligonierization. When temperaturebeyond l 10"C there was part of polymer. So it is important toselect suitabIe reaction temperature, at this temperature thecatalysts should have higher activities and no po1ymer isformed. Under optimal reaction conditions the activity ofInd,Zr(OC,H.-p-Me),/Et,AICl was l 666 g/g Zr.h withselectivity of 92.7% for C.-,, olefins and 86.0% for C.-,,l ine ar a- o l e fi ns.The effect of cocata1ysts on ethylene oligomerizationwas also discussed. Et,AlCl is a better cocatalyst thanEt,Al,Cl,, EtAlCl, and Et,Al, but with cocatalysts Et,Al,Cl,and EtAlCI, no polymer is formed even at the temperature ofl 1 0'C.'The reaction conditions have great effect on the activityand selectivity of ethylene oIigomerization. When reactiontemperature is 90"C and aging temperature is 80"C, weobtained the higher activity and highest selectivity ofo l i g o m e r s.The catalytic properties of a series of Fe(II) diimineco mpl exe s (dii mine=N,N '-o -p heny l enebi s(sal icylideneamina-to), N,N 'ethylene-bis(sal icylideneaminato), N,N '-o-phen-yl enebi sbenzal, N,N '-ethyl enebi sbenzal) in combinationwith EAO (ethylaluminoxane) for ethylene o ligomerizationhave been investigated. Treatment of the iron(II) complexeswith EAO in toluene generates active catalytic systems insilll that oligomerize ethylene to low-carbon olefins. Theeffects of reaction temperature, ratios of A1/Fe and reactiontime on catalytic activity and product distribution have beenstudied. The activity of complex FeCl,(PhCH=o-NC,H.N=CIuIPh) with EAO at 200"C is 1 .3 5xl0' g oligomers/mo1 Fe'h.The seIectivity of C.-,, olefins is 85 .5% and selectivity ofC^-,, lillear a-o1efins is 69.5%. When the P-O 1igand wasadded, the activity and the selectivity of C#-,, olefins of irondi imine complexes/EAO were increased for ethy1eneoligomerization, but the seIectivity of C#-,, Iinear a-oIefinswas decreased. The catalytic properties of a series of Co(II)di imine complexes Co(N"N)Cl, {N"N = N,N'-o-pheny1ene-bisbenzaI; NAN = N,N'-ethylenebisbenzal; NrtN = N,N'-o-plleny1eneb is(di phenyl n1ethy1 ene)] in combinati on with EAO(ethylaluminoxa11e) as cocatalyst for ethylene oligomeriza-tion have been investigated. Treatment of the cobalt(II)diin1ine complexes with EAO in toluene generated activecatalysts in silll tl1at are capabIe of oligomerizing ethyleneto Iow-carbon oIefins. Changing reaction conditions, such asreaction temperat...