Industrial polyethene production

Transesterification is a crucial step in several industrial processes such as (i) production of higher acrylates from methylmethacrylate (for applications in resins and paints), (ii) polyethene terephthalate (PET) production from dimethyl terephthalate (DMT) and ethene glycol (in polyester manufacturing),... 

By far the most important industrial coordination polymerization processes are Ziegler-Natta polymerizations of 1-olefins [107-110], most notably the production of high-density polyethene [111] and stereo-specific olefin polymers and copolymers [108], However, these processes employ solid catalysts, and the complex kinetics on their surfaces have no place in a book on homogeneous reactions. 

The earliest Ziegler-Natta catalysts were insoluble bimetallic complexes of titanium and aluminum. Other combinations of transition and Group I-III metals have been used. Most of the current processes for production of high-density polyethene in the United States employ chromium complexes bound to silica supports. Soluble Ziegler-Natta catalysts have been prepared, but have so far not found their way into industrial processes. With respect to stereo-specificity they cannot match their solid counterparts. 

Only a limited number of building blocks are required by the large scale chemical industry. Of these ethene occupies a prime position. It is the principal feedstock for the manufacture of about 30% of all petrochemicals. In 1985 about 13.8m tonnes were produced in the USA alone. Of this 44% was converted into polyethene, 18% into ethene oxide and 14% into vinyl chloride (for PVC). Ethene oxide is the precursor to 1,2-ethane diol (ethylene glycol) which is used as an antifreeze and as a component for polyester production. These figures emphasize the dominant position of polymers in the petrochemical industry. Some of the processes, described below, which employ homogeneous catalysts are carried out on a much smaller scale and may represent only a small fraction of the total usage of chemical feedstocks. 

Although PVC is second only to polyethene in terms of polymer production volumes, recycling is not widespread this is attributable to the long-term nature of its major applications in the construction industry, e.g. pipes and window frames. A potentially valuable source of PVC in municipal waste is the water bottle (especially in areas of high bottled water consumption like France). PVC has found widespread use in this application since it does not taint the water. 

Ethene (ethylene) can serve as a case study for the significance of alkenes in industrial chemistry. This monomer is the basis for the production of polyethene (polyethylene), millions of tons of which are manufactured in the United States annually. The major source of ethene is the pyrolysis of petroleum, or hydrocarbons derived from natural gas, such as ethane, propane, other alkanes, and cycloalkanes (Section 3-3). 

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