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Petrochemical feedstocks
Petrochemical feedstocks
Petrochemical
feedstocks
Oil, gas and coal provide the
hydrocarbons for feedstocks.
Feedstocks are the various hydrocarbons derived
from the refining of oil, gas and coal. These are
then further refined to produce petro chemical
products. They are the building blocks of
petrochemical products.
These building blocks are converted into a
wide range of chemical products with a wide
range of uses. At the feedstock stage, they are
usually known as intermediates – then the intermediates
are processed into plastics, liquids and
resins which ultimately are turned into useful
products. Some feedstocks, however, are used
directly to produce petrochemicals, such as
methane and BTX. But ethane, propane, butanes,
naphtha and gas oil are optional feedstocks for
steam crackers that produce intermediate petrochemical
feedstocks. Other examples of intermediate
feedstocks include ethylene, propylene,
butenes and butadiene.
Gas and oil are the most common starting
points for feedstocks because they are still readily
available, can be processed efficiently and are
usually less expensive than other raw materials.
This is why petrochemical companies often build
their plants close to oil and gas refineries – as a
result, operational costs, such as transportation,
are reduced. Coal-derived feedstock, meanwhile,
is mainly methanol, obtained from a coal-toliquids
process. Coal can also be gasified to
produce feedstocks.
Methane, ethane, propane and butanes are
mainly obtained from natural gas. Naphtha and
gas oil, as well as benzene, toluene and xylenes, (a
group commonly referred to as BTX) are obtained
from petroleum refineries. Ethylene, propylene
and butadiene are the basic building blocks of all
olefins (also known as alkenes) and these form the
basis for many common products (see diagram on
page 34).
Synthesis gas, also known as syngas, is the term
for gas obtained from synthesising hydrogen and
carbon monoxide, and this can also be converted
into feedstock. Syngas can also be an intermediate
by-product developed during the processing of
ammonia, methanol, synthetic petroleum or
synthetic natural gas. Petroleum by-products that
might otherwise end up as waste can be
conserved as feedstock. During the gasfication
refining process, any material which contains
carbon can also be converted.
Since feedstocks and the end products vary,
there are many different production methods (see
page 22). For example, an ethylene-producing
plant is most likely to use catalytic cracking, a
technique that uses high pressure and high
temperatures to crack natural gas. But in a
methanol-producing plant, a reforming process,
using high temperature steam, medium pressure
and a catalyst, will produce the product.
While oil, gas and coal are still in plentiful supply
in many parts of the world, alternative sour ces
for petrochemical feedstocks have been developed
and will continue to be developed as fossil
fuels are depleted (see page 102). For example, feed -
stocks can be produced from sugar cane, corn and
other organic agricultural sources. While there is
controversy over using food for fuel, this is seen as
a viable alternative for areas with few fossil fuel
sources but space for large-scale agriculture.
Feedstock and geography
Feedstock supplies vary between different regions
and supply trends can change, especially when new.
Ethane feedstock supply has decreased in the
Middle East and Canada, for example. New oil and
gas discoveries have impacted on the petrochemi
cal industries of the US, Brazil and Canada.
In the case of the US and Brazil, both countries
have benefited with the respective discoveries of
shale gas and pre-salt reserves.
In Canada, ethane production is down because
of reduced natural gas supply from the Western
Canadian Sedimentary Basin. The Canadian petrochemistry
sector is now focusing on a discovery of
bituminous oil, which now accounts for more
than 50% of the country’s crude oil production,
for meeting future feedstock needs.
The petrochemical sectors of Saudi Arabia, Iran
and Qatar use ethane as the main petrochemical
feedstock, but securing new ethane supplies has
become difficult because of high demand from
existing petrochemical plants and the energy
sector. As such, planned petrochemical plants in
the Middle East are based on naphtha feedstock.
Natural gas production increased in Saudi Arabia,
Iran and Qatar but it’s not enough to satisfy the
requirements. Despite the increases in nat ural gas
production in Saudi Arabia and Iran, ethy lene
capacity has increased even more. Qatar’s ethane
production has been restricted because of a mora
torium on its North Dome gas field.
The emergence of China’s shale gas and coal
industries has also changed the face of the world’s
feedstock supplies. This ongoing development in
China will serve to bolster the country’s growing
economy. For more detailed information on the
world’s petrochemical markets, turn to page 82.
FPSO Cidade de São Paulo leaving port bound for the Sapinhoá field, offshore Brazil. Pre-salt discoveries, though challenging to extract, will
have a major impact on the country’s oil and gas industries.
32 WPC Guide
Petrochemicals and Refining 33