Crude oil provides the principal source of carbon for the whole of the chemical industry, to fabricate products ranging from plastics to pharmaceuticals. However, oil is a finite resource, and predictions from the Energy Information Administration (EIA) are that the world supply of crude oil may begin to fail demand for it within a year, which is in accord with studies from both the U.S. and German military. p-Xylene is a raw feedstock for the polyester industry, and is produced by catalytic reforming of petroleum naphtha. p-Xylene is oxidized to form terephthalic acid, which by condensation with ethylene glycol forms polyethylene terephthalate, of which some 5 million tonnes annually is manufactured. A process is under development for making polyesters which is independent of crude oil, since it uses ethylene as its feedstock. First, a trimer molecule, containing 6 carbon atoms, is formed from ethylene. Following dehydrogenation, this material undergoes a Diels–Alder reaction with an additional ethylene molecule to form 3,6-dimethylcyclohexene. By dehydrogenation of the latter material, using a platinum catalyst supported on alumina, a good yield of p-xylene is obtained, with minimal side-products, so obviating the need for complex, energy-intensive separation processes. In contrast to cracking light hydrocarbons from oil at high temperatures to form ethylene, it might instead be generated from biomass, and thus this development might be perceived as a first step on the path to the extrication of an industry from its utter dependency on crude oil. In the medium term, ethylene can be made from Natural Gas Plant Liquids, or even shale gas.
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