Propene (often known as propylene), like ethene, is a very important building block for a large number of chemicals, including the addition polymer, poly(propene).
Uses of propene (propylene)
Figure 1 The uses of propene.
The principal uses of propene are to produce:
The data given in Figure 1 are for global production. However, the data vary from country to country. For example, the proportion used to make poly(propene) varies from only 55% in North America and 56% in Europe to 90% in the Middle East and the proportion used to make propenal is 15% in Japan but 9% in China.
Data from IHS 2011
Annual production of propene (propylene)
Manufacture of propene (propylene)
Propene is manufactured by:
Steam cracking accounts for ca 56% and catalytic cracking for 33% of the global production. Much of the rest is made from the production of oil from coal and from the cracking of gas oil under vacuum,
Increasingly, propane is being catalytically cracked to form propene, using the same cat cracker as that used to crack gas oil:
The reason for the increase in production of the alkene from propane is because of the increasingly large amounts of the feedstock obtained from shale gas in the US.
'Green' propene is also being produced in larger amounts.
Note on the chemistry of ethene (ethylene) and propene (propylene)
All the C-H bonds in ethene are very strong and thus the majority of its reactions involve addition to the double bond.
However, the C-H bonds in the methyl group are much weaker and propene has many reactions in which the double bond is preserved and the methyl group undergoes substitution reactions, for example:
Epoxypropane is manufactured in three main ways:
(i) By reacting propene with an aqueous solution of chlorine to form a mixture of 1-chloropropan-2-ol (90%) and 2-chloropropan-1-ol (10%). Epoxypropane (propylene oxide) forms on addition of a solution of either sodium hydroxide or calcium hydroxide. For example:
(ii) By reacting propene with a hydroperoxide such 1,1-dimethylethyl hydroperoxide.Propene is passed into liquid 1,1-dimethylethyl hydroperoxide under pressure at about 400 K with a soluble molybdenum salt as catalyst:
(iii) By reacting propene with hydrogen peroxide. New plants have been built, adjacent to the plants producing propene, to manufacture large quantities of hydrogen peroxide. The peroxide reacts directly with propene:
Alhough hydrogen peroxide is expensive to produce, the large scale of the plant, coupled with the lower costs associated with the eflfuent means that this new process is very attractive.
Manufacture of butanal (butrylaldehyde) and butanol
Butanal is produced by passing propene, carbon monoxide and hydrogen over a solid cobalt salt (a process known as the OXO process or hydroformylation):
(The isomer of butanal, 2-methylpropanal, (CH3)2CHCHO, is also formed).
Butanal is hydrogenated to butanol.
Date last amended: 24th November 2013