Page 171 - Encyclopedia of Chemical Compounds 3 Vols

BUTANE

90 percent) of methane. Other components include ethane
Butane. Black atoms are
(about 9 percent), propane (about 3 percent), and butane
carbon; white atoms are
hydrogen. All sticks are single (about 1 percent). The remaining 1 to 2 percent of natural
bonds. PUB L I S H E RS RE SO URCE gas is impurities, including nitrogen, carbon dioxide, com-
GRO U P pounds of sulfur, and water. The process of separating natural
gas into its components begins with the removal of water.
The natural gas is forced through some drying agent, such as
diethylene glycol (HO(CH 2 ) 2 O(CH 2 ) 2 OH), which efficiently
removes water from the gas. The dry gas is then treated with
an agent to remove carbon dioxide, compounds of sulfur, and
other impurities. Diethanolamine (HO(CH 2 ) 2 NH(CH 2 ) 2 OH) is
an efficient ‘‘scavenger’’ of many of these impurities.
After dehydration and removal of impurities, the remaining
gas consists almost entirely of simple hydrocarbons, primarily
methane, ethane, propane, and butane. These hydrocarbons can
be separated from each other by cooling them until they reach
the point at which they become liquid. As each component
liquefies, it can be removed from the gas and further purified.

For example, butane changes from a gas to a liquid at 0.5 C

(31 F) and propane liquefies at about 42 C( 44 F). So as the

120 CHEMICAL COMPOUNDS