Paradox of Late Transition-Metal Catalysts in Ethylene Polymerization

Abstract

Polyolefin materials are the most synthesized polymer used nowadays and symbolize the development level of the national petrochemical industry, in which polyethylenes are major along with alternative product α-olefins for co-monomer and substrates for fine chemicals. Likely operating catalysts such as Ziegler-Natta and metallocene meet all demanding of various polyethylene materials, what is any business in developing late-transition metal catalysts for ethylene reactivity? In the past two decades, we realized the advantages of late-transition metal catalysts, such as easy variousness and easy preparation, good stability and high catalytic activity. Besides these, the characteristic different polyethylenes have been achieved as either highly linear polyethylene or highly branched polyethylenes. Therefore, there are some spaces in developing new catalytic system on the base of late-transition metal catalysts to compromise the demanding for new polyethylenes from sole ethylene polymerization.

Cobalt Catalysts Bearingortho‐(4,4′‐Dichlorobenzhydryl) Substituents and Their Use in Generating Narrowly Dispersed Polyethylene of High Linearity

“…Subsequently, the activity gradually decreased to 5.63×10 6 g (PE) mol −1 (Co) h −1 after 1 hour, which indicated that the active species was not only formed quickly following the addition of MAO but also gradually underwent deactivation over the course of time [61] . Nevertheless, it was evident that longer polyethylene chains were produced with longer reaction time (Figure 4), which suggests that there were still sufficient active sites to maintain effective chain propagation [62] …”

“…[61] Nevertheless, it was evident that longer polyethylene chains were produced with longer reaction time (Figure 4), which suggests that there were still sufficient active sites to maintain effective chain propagation. [62] To examine the effect of ethylene pressure on Co1/MAO, we additionally conducted the polymerizations at 5 atm and 1 atm. At 5 atm, the catalytic activity dropped by more than half from 8.96 × 10 6 g (PE) mol À 1 (Co) h À 1 to 3.49 × 10 6 g (PE) mol À 1 (Co) h À 1 (entries 3 and 14, Table 2).…”

Polyethylene Waxes with Short Chain Branching via Steric and Electronic Tuning of an 8-(Arylimino)-5,6,7-trihydroquinoline-nickel Catalyst

“…With particular regard to late transition metal polymerization catalysts, α-diimine nickel complexes have been central to the development of the field . Indeed, these catalysts, first reported in 1995 ( A in Chart ), have the capacity to mediate the formation of branched polyethylenes from a single ethylene feed via a process known as chain walking .…”

Trapping the Short-Chain Odd Carbon Number Olefins Using Nickel(II)-catalyzed Tandem Ethylene Oligomerization and Friedel-Crafts Alkylation of Toluene

“…Recently the area of nickel-catalyzed oligomerization and polymerization of olefins received a new boost. Nickel complexes are being widely employed for processes of chain-walking ethylene polymerization [4,5,[14][15][16][17][18][19][20][21][22][23]6,[24][25][26][27][7][8][9][10][11][12][13] and copolymerization of ethylene with polar monomers [22,24,[35][36][37][38][39][40][41][42][43][44][27][28][29][30][31][32][33][34]. However, the interest in the development of new nickel-based catalytic systems for ethylene oligomerization is still high [4,6,[53][54]…”