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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