Polyethylenes iron catalysts

Keywords 2-6-Bis(arylimino)pyridine, Cobalt catalysts, Iron catalysts, Olefin polymerisation, Polyethylene... 

The introduction of metal alkyls to an MAO-activated bis(imino)pyridine iron catalyst has also been the subject of a number of studies. Both AlMe3 and AlEt3 have been added to 5a/MAO-based polymerisation catalysts leading to polyethylene displaying a bimodal distribution similar to that observed using 5a/M AO,... 

As is showm in Figure 2, methane is formed over nickel and ruthenium catalysts, especially at low pressures (atmospheric up to 10 bar) and elevated temperatures. Paraffins and olefins are produced over nickel and cobalt catalysis at mild temperatures (< 200 0) and pressures of I -10 bar. With iron catalysts, olefins,parafllns.and minor amounts of alcohols are formed at medium pressures (10 100 bar) and temperatures of 210--340 C. Ruthenium catalysts give, at elevated pressures (150-1000 bar) and low temperatures (100-180 C), poly methylene with a molecular weiglii of up to I 000000. This polymer has similar properties as Ziegler-type low pressure polyethylene. 

Iron catalysts [20-24] have been used to make polyethylene-clay nanocomposites where the polyethylene had very broad molecular weight distribution (MWD). Ziegler-Natta [25, 26], organo-chromium (Phillips) [27], and bis(imino)pyridine iron and cobalt catalysts [28] have also been used to make polyolefin-late transition metal catalysts [29, 30], capable of producing highly branched polyethylene from only ethylene and of promoting the copolymerization of ethylene with polar comonomers, have also been apphed to make polyolefin-clay nanocomposites. 

The primary products from iron catalysts are linear polyethylenes and aluminum polymeryls. The iron complexes can be prepared in a few simple steps and are not particularly sensitive to air, contrasting with many metallocenes of group 111 and IV or rare earth complexes. A body of literature on ethylene polymerization studies with these complexes allows a picture to be created of the catalytic action [31]. Here, a summary is given oti the catalytic activity of these complexes, also in combination with solid supports, and an outlook towards the preparation of composites. 

Polyethylene was previously prepared by the authors (1) using catalyst, (II), consisting of the co-catalyst with bis(l,5-cyclooctadiene)-nickel. Polyethylene was also prepared by Salon et al. (2) and Baugh et al. (3) using iron- and nickel-based organometallic catalysts, (III) and (IV), respectively. 

Boutevin et al. [177-180] treated different types of wastes of polyolefins (more often low density polyethylene) with a mixture air/ozone. They focused their studies on the quantification of the formed oxygenated species based on colorimetric titration using stable radicals such as diphenylpicryl-hydrazyl. They investigated the influence of mineral compounds (iron oxide, for example) used as catalysts for oxidative reactions. The ozonized polymers have been used as binders for composites materials containing mineral materials (sand, stones, etc.). 

Terminally brominated PE as PE macroinitiator can be produced by other methods. It has been reported that vinyl terminated PE produced by a bis(phenoxy-imine)metal complex and MAO catalyst system (Mn = 1800, Mw/Mn = 1.70) was converted to terminally 2-bromoisobutyrate PE through the addition reaction of 2-bromoisobutyric acid to the vinyl chain end. Polyethylene-Wodc-poly( -bulyl acrylate) (PE-fo-PnBA) from terminally brominated PE by ATRP procedure has also been produced [68]. It was reported that degenerative transfer coordination polymerization with an iron complex can be used to prepare terminally brominated PE as a macroinitiator [69]. A Zn-terminated PE prepared using an iron complex and diethylzinc,... 

In co-hydropyrolysis experiments without catalysts the degree of pine wood/ polyethylene mixture (1 1 weight ratio) conversion was 80% wt. and yield of the light liquid fraction - 23% wt. The addition of iron ore catalyst activated by mechanochemical treatment increased the degree of mixture conversion by 5-13%. This increase was mainly due to light liquid fraction formation. The variation of catalyst nature (pyrite, pyrrhotite, haematite) influences on the product composition. Pyirhotite catalyst yields the highest amount of the light fraction (about 40% wt.). 

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