Ethylene polyethylene from

When many moleeules eombine the maeromoleeule is termed a polymer. Polymerization ean be initiated by ionie or free-radieal meehanisms to produee moleeules of very high moleeular weight. Examples are the formation of PVC (polyvinyl ehloride) from vinyl ehloride (the monomer), polyethylene from ethylene, or SBR synthetie rubber from styrene and butadiene. 

Exxpol [Exxon polymerization] A gas-phase process for making polyethylene from ethylene. The process uses single-site catalysis (SSC), based on a zirconium metallocene catalyst. Developed by Exxon Chemical Company in 1990 with plans to be commercialized in 1994. 

Another important aspect of supercritical fluids application is in polymer fractionation, in order to obtain mono-dispersed molecular weights. The simulation of the fractionation of polyethylene from ethylene and hexane solutions into fractions of different molecular weights was proposed by Chen et al. [7]. 

Polymerization is a process in which similar molecules (usually olefins) are linked to form a high-molecular-weight product such as the formation of polyethylene from ethylene... 

Plastics require such a wide variety of raw materials that it is difficult to select the major petroleum chemical developments. Styrene, vinyl chloride, and polyethylene from ethylene, formaldehyde from petroleum methanol, and urea from petroleum ammonia are the chief contributions of petroleum chemicals. 

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

OTHER COMMENTS used as a catalyst in the production of polyethylene from ethylene used as a chlorinating agent for aryl or alkyl acids and salts, ketones and aldehydes also used as a dehydrating agent. 

The ability to predictably prepare linear low-density polyethylenes from ethylene alone represents an opportunity to design ethylene homopolymers for target applications. 

For example, the synthesis of polyethylene from ethylene is shown in Fig. 3.12. 

The simplest type of addition reaction is the formation of polyethylene from ethylene monomer ... 

The simplest example of a polymerization reaction is the formation of polyethylene from ethylene molecules (t FIGURE 12.35). In this reaction, the double bond in each ethylene molecule opens up, and two of the electrons originally in this bond are used to form new C—C single bonds with two other ethylene molecules. This type of polymerization, in which monomers are coupled through their multiple bonds, is called addition polymerization. 

From the perspective of the chemical industry, the single most important reaction of ethylene and other low-molecular-weight alkenes is the production of chain-growth polymers (Greek poly, many, and meros, part). In the presence of certain catalysts called initiators, many alkenes form polymers by the addition of monomers (Greek mono, one, and meros, part) to a growing polymer chain, as illustrated by the formation of polyethylene from ethylene ... 

Quijada, R., Rojas, R., Bazan, G., Komon, Z.J.A., Mauler, R.S., Galland, G.B., Synthesis of branched polyethylene from ethylene by tandem action of iron and zirconium single site catalysts. Macromolecules 2001,34 2411-2417. 

Figure 25.1 Addition polymerization to form polyethylene from ethylene. Each curved, single-headed arrow represents the movement of one electron.

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