CIEC Promoting Science at the University of York, York, UK

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Basic chemicals Propene (Propylene)
Propene (Propylene)

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).


However, unlike ethene, propene readily undergoes substitution reactions, which lead to a wide range of important chemicals.

 

 

 

Uses of propene (propylene)

Figure 1  The uses of propene.

The principal uses of propene are to produce:

  • poly(propene) (polypropylene)
  • propenal (acrolein) which is oxidized to propenoic acid (acrylic acid) which, in turn, is used to make acrylic polymers
  • propenonitrile (acrylonitrile) which is the monomer for poly(propenonitrile)
  • cumene ((1-methylethyl)benzene or isopropylbenzene) which is then used to make phenol and propanone (acetone)
  • epoxypropane (propylene oxide) which is used to make diols for the manufacture of polyurethanes and solvent
  • butanal (butrylaldehyde) and hence butanol, used as a solvent for surface coatings

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)

World 80.0 million tonnes1
Europe 14.3 million tonnes3
US 14.3 million tonnes2

Data from:
1.  Chemical and Petroleum Manufacturers of India,  Data for 2012
2.  American Chemical Council 2013 Statistics.  Data for 2012
3.  APPE (Association of Petroleum Producers in Europe).  Data for 2012

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.
Similarly, propene has 3 strong C-H bonds and undergoes addition reactions (for example, polymerization to poly(propene) and propene to epoxypropane).

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:

Manfacture of epoxypropane (propylene oxide)

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