Petrochemicals

Saudi Arabian petrochemical plant. Source: Creative Commons

Published: September 25, 2011, 12:00 am

Updated: March 4, 2012, 7:20 pm

Lead Author: Milton Beychok

This article has been reviewed by the following Topic Editor: C Michael Hogan

Petrochemicals are chemical products made from the hydrocarbons present in raw natural gas and petroleum crude oil. The largest petrochemical manufacturing industries are to be found in the USA, Western Europe, Asia and the Middle East.

A relatively small number of hydrocarbon feedstocks form the basis of the petrochemical industries, namely methane, ethylene, propylene, butanes, butadiene, benzene, toluene and xylenes.^[1][2]

As of 2007, there were 2980 operating petrochemical plants in 4320 locations worldwide.^[3] The petrochemical end products from those plants include plastics, soaps, detergents, solvents, paints, drugs, fertilizer, pesticides, herbicides, explosives, synthetic textile fibers and rubber, flooring and insulating materials and more.

Petrochemicals are found in such common consumer products as aspirin,automobiles, clothing, compact discs, video tapes, electronic equipment, furniture, and a host of others.^[4]

1 Feedstock sources

1.1 Worldwide usage of optional steam cracking feedstock sources

1.2 The effect of feedstock on the steam cracking yields of intermediate petrochemical products

2  Feedstocks and example petrochemical products

3 References

The adjacent block flow diagram schematically depicts the major hydrocarbon sources used in producing petrochemicals:

• Methane, ethane, propane and butanes: Obtained primarily from natural gas processing plants.
• Naphtha: Obtained primarily from petroleum refineries.
• Benzene, toluene and xylenes, as a whole referred to as BTX: Primarily obtained from petroleum refineries by extraction from the reformate produced in catalytic reformers.
• Gas oil: Also obtained primarily from petroleum refineries.

Methane and BTX  (benzene, toluene and xylenes) are used directly as feedstocks for producing petrochemicals. However, the ethane, propane, butanes, naphtha and gas oil serve as optional feedstocks for steam-assisted thermal cracking plants referred to as steam crackers that produce these intermediate petrochemical feedstocks:^[5][6]

• Ethylene
• Propylene
• Benzene
• Butenes and butadiene

In 2007, the amounts of ethylene and propylene produced in steam crackers were about 115 Mt (megatonnes) and 70 Mt, respectively.^[7] The output ethylene capacity of large steam crackers ranged up to as much as 1.0 – 1.5 Mt per year.^[8][9].

Steam crackers are not to be confused with steam reforming plants used to produce hydrogen and ammonia.
As of 2004, the percentage of the worldwide steam cracking plants using each of the optional steam cracking feed sources was:^[10]

• Ethane: 35%
• Propane: 9%
• Butanes: 3%
• Naphtha: 45%
• Gas oil: 5%
• Other: 3 %

The effect of feedstock selection upon the yields of steam cracking products is summarized in the table below:

The table below includes some representative examples of the petrochemical end products produced from the eight hydrocarbon feedstocks – methane, ethylene, propylene, butenes, butadiene, benzene, toluene and xylenes:

1. ^Sami Matar and Lewis F. Hatch (2001), Chemistry of Petrochemical Processes, Gulf Professional Publishing, ISBN 0-0-88415-315-0.
2. ^Staff (March, 2001), "Petrochemical Processes 2001", Hydrocarbon Processing, pp. 71-246, ISSN 0887-0284.
3. ^Petrochemical Industry – Worldwide.
4. ^Petrochemicals Chart From the website of the National Petrochemical & Refiners Association.
5. ^SBS Polymer Supply Outlook
6. ^Editor: Jean-Pierre Favennec (2001), Petroleum Refining: Refinery Operation and Management, Editions Technip, ISBN 2-7108-0801-3.
7. ^Editors: Hassan E. Alfadala, G.V. Rex Reklaitis and Mahmoud M. El-Halwagi (2009), Proceedings of the 1st Annual Gas Processing Symposium, Volume 1: January, 2009 - Qatar, 1st Edition, Elsevier Science|pages, pp. 402-414, ISBN 0-444-53292-7.
8. ^Cracker capacities From the website of the Association of Petrochemicals Producers in Europe (APPE).
9. ^Ethylene Production (pdf page 3 of 12 pdf pages).
10. ^Richard Meyers (2003), The Basics of Chemistry, Greenwood Press, ISBN 0-313-31664-3.