Ethylene-propylene-dimer

Ethylene-propylene-dimer (EPDM) rubber has a good balance of toughness, durability, chemical resistance, and barrier performance that makes this rubber suitable for the manufacture of parts for power transmission, i.e., belts, etc., gaskets, and hoses. EPDM also has utility as a dispersed phase to toughen thermoplastics. 

Elastomers examined included NR, nitrile rubber, ethylene-propylene dimer and a vinylidene fluoride - hexafluoropropylene copolymer. Examination of migrating species was carried out by methods discussed in the EC Framework Directive 89/109/ EC (see Chapter 16). Distilled water and diethyl ether extractants were included in this study. 

Since the above reaction is reversible, it can be used to produce either propylene or ethylene and butenes depending on relative prices. For example, when propylene is inexpensive, ethylene and butenes are produced. When ethylene is inexpensive and there is a high demand for propylene, ethylene is dimerized to butene and then the reverse reaction is utilized. A commercial plant based on the reverse reaction has been built on the Gulf Coast. 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

Some types of reactions involving gases that have been studied in IFs are hydrogenations [16, 25-37 ], oxidations [38, 39], and hydroformylations [25, 40 5]. In addition, some dimerizations and allcylations may involve the dissolution of condensable gases (e.g., ethylene, propylene, isobutene) in the IF solvent [46-50]. 

EP is abbreviation, EPM means ethylene and propylene only, EPDM means ethylene, propylene, and dimer Most, about 85%, of EP is EPDM 55% Ethylene, 40% propylene, 5% dimer for cross-linking... 

Although the preceding discussion of the sulfuric and hydrofluoric acid processes has been confined to butene alkylation, isobutane has also been alkylated commercially with other olefins. Ethylene, propylene, pentenes, and dimers of butenes have been used for this purpose. It is also possible to use these olefins for the alkylation of isopentane. Such an operation, however, has not achieved commercial acceptance because it produces an inferior alkylate with a high catalyst consumption, and because isopentane is a satisfactory aviation gasoline component in its own right. 

Steam cracking of various petroleum fractions is gaining widespread use for the production of olefins. These olefins are produced essentially for use as feed stock for numerous petrochemical processes, but the by-product butylenes and propylenes are sometimes used as feed stock for aviation and motor alkylation units. Ethylene is the most important of the olefins produced from this type of cracking, and propylene is second in importance. These two olefins are normally charged to either alkylation or polymerization units for the production of petrochemicals or petrochemical intermediates. Polyethylene and propylene dimers, trimers, tetramers, and penta-mers are some of the more important polymers produced, while ethybenzene, dodecylbenzene, cumene, diisopropylbenzene, and alkylated... 

Figure 7.6 Industrial use of (from the top) propylene dimerization, butadiene dimerization, butadiene trimer-ization, and butadiene plus ethylene codimerization. In EPDM rubber, the terminal double bond of 1,4-hexadiene takes part in polymer formation. The internal double bond is used during curing.

Olehns with four to eight carbon atoms can be obtained by dimerization and codimerization of ethylene, propylene and butenes. 

The IR spectra of an AES film recorded in the hydroxyl vibration region during the first 38 h of irradiation showed an increase in a broad absorption band centered around 3450 cm-1 attributed to hydroperoxides. The development of a complex band with a maximum at 1713 cm-1 and shoulders around 1690, 1730 and 1770 cm-1 was observed in the carbonyl vibrations region (Figure 30.6). These maxima correspond to carbonylated photoproducts that have been previously identified during photooxidation of EPDM [17] and ethylene-propylene copolymer [18]. The bands at 1713, 1730 and 1770cm-1 correspond, respectively, to the absorption of saturated acids (dimer form) and ketones, esters and lactones or peresters the absorption around 1690 cm-1 is related to the presence of unsaturated carbonyl species. 

An excellent review on soluble systems, including also the more recent progresses in ethylene polymerization, is that of Sinn and Kaminsky who even developed soluble catalytic systems with extremely high activities by using alumoxane and biscyclopentadienyl-titanium or-zirconium compounds. Interesting results have also been obtained in ethylene oligomerization and in propylene dimerization... 

Ethylene and Propylene Dimerization u/ith wAllylnickel Halide Catalysts... 

Even as a toluene emulsion, these complexes show catalytic activity towards ethylene and propylene which is several orders higher than that of TT-allylnickel halides. Paralleling the increase in catalytic activity, the selectivity of this catalyst is also increased—i.e., the products are mainly ethylene or propylene dimers. The most active catalytic systems for dimerizing ethylene and propylene are obtained by replacing toluene with halogenated hydrocarbons such as chlorobenzene since in these more polar solvents, the complexes XIII are soluble. 

Of prime importance for utilizing the new catalyst was the observation that the products of propylene dimerization with phosphine-modified catalyst system, XVI, are strongly influenced by the nature of the phosphine PR3 (24, 25). To understand the phosphine effect, it is necessary to examine the dimerization of ethylene and of propylene in some detail. The dimerization of ethylene formally involves the addition of the C-H bond of one olefin molecule across the double bond of a second one ... 

The dimerization reaction has been carried out under two different conditions. In laboratory experiments, the reaction is conveniently carried out under 1 or less than 1 atmosphere and at a temperature of —20° to — 10°C. These relatively low temperatures are necessary to obtain a sufficient concentration of ethylene or propylene in the catalyst solution. The dimerization catalyst for laboratory experiments is usually prepared by mixing, for example, chlorobenzene solutions of a 7r-allylnickel halide and an aluminum halide (or alkylhalide) in molar ratio of at least 1 1. The phosphine-modified catalyst is obtained by simply adding 1 mole of a phosphine per mole of nickel to the solution of the catalyst. When ethylene or propylene is introduced into the catalyst solution, reaction starts immediately, as evidenced by a sudden rise in temperature. Dimerization is exothermic to the extent of about 28 kcal./mole propylene dimer. Hence, the mixture must be stirred and cooled intensively during the reaction. Under these conditions (Table V), reaction rates of about 6 kg. 

Propene and higher a-olefins also may be dimerized or oligomerized by these catalysts. Generally, reactivity is much lower than that of ethylene and decreases in the order ethylene propylene > 1-butene > 1-hexene > 1-octene > 1-decene. Also the selectivity is lower and mainly branched dimers or oligomers are formed. ... 

Propylene is, next to ethylene, the most important basic chemical to produce not only polypropylene but also other intermediates for example propylene oxide and acrylonitrile. Just like ethylene, propylene can be produced via a hydrocarbon feedstock produced from a biomass [35-37]. Bio-glycerol produced as a byproduct of biodiesel can be dehydrogenated to produce propylene [48]. Bio-based ethylene can be dimerized to produce n-butene, which can then react with remaining ethylene via metathesis to produce propylene [49]. The use of fermentation products of biomass such as 1-butanol [50] enables the formation of n-butene, followed by a subsequent methathesis [49]. Alternatively, hydrothermal carboxylate reforming of fermentation products such as butyric acid or 3-hydroxybutyrate is also proposed as a viable option to propylene [51]. 

The dimerization of ethylene to form a mixture of butene isomers is not particularly useful in the field of commodity chemicals at this time because this mixture of butenes is usually cheaper than ethylene. Selective dimerization of ethylene to 1-butene using a titanium catalyst is practiced, but this chemistry occurs through metallacycles and is described in the next section. The dimerization of propylene by migratory insertion chemistry typically produces the mixture of isomeric olefins shown in Equation 22.32. Four skeletal isomers of the intermediate metal alkyl can arise from the two different directions of M-H insertion, followed by two different inodes of M-R insertion. The dimerization of ethylene is particularly fast when catalyzed by the combination of NiBr(-r) -C3H5)(PCy3) and EtAlCl this dimerization in chlorobenzene at 25 °C occurs witii turnover frequencies up to 60,000 per second. The more selective dimerization of propene to 2,3-dimethylbutene is conducted on an industrial scale with titanium catalysts, again via metallac clic intermediates described in the next section. 

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