286 Science and Human Welfare
to take place at high temperature in the vapor phase. The
vapor phase processes, like the deFlorez and the Gyro, pro-
duced a higher octane product but gave a mixture rich in
unsaturated hydrocarbons and thus suffered in stability. The
problem confronting the chemist a decade ago was to convert
the straight-chain hydrocarbons, which have low octane
numbers, to the so-called side-chain hydrocarbons which
have much higher octane numbers. Most of the development
in recent years has been along the line of catalytic cracking.
By means of suitable catalysts the desired reactions have
been made to take place at lower temperature and the effect
of the undesirable high temperature reactions has been
minimized.
Gasoline may be made from petroleum gases by poly-
merizing, which is the combining of two or more simple
hydrocarbon molecules into a more complex one. Thus, for
example, when two molecules of the unsaturated hydrocar-
bon butylene combine they form dibutylene which is still an
olefin, but is now a liquid instead of a gas. The catalyst,
phosphoric acid, polymerizes olefins in cracked gases to motor
fuel of high octane rating. This same catalyst is used for the
production of loo-octane aviation gasoline by selectively
polymerizing butylene to iso-octene and hydrogenating the
latter to iso-octane. This simple polymerization process made
a revolutionary change in the oil industry. This process is
conserving crude oil at the rate of many million barrels per
year, and in addition is producing a motor fuel superior to
that derived directly from crude oil. The interesting point is
that these gasolines are being obtained from refinery gases
which were once burned only as fuel.
Another process, called “Alkylation,” refers to the uniting
of an olefin and an iso-paraffin in the presence of sulphuric or
hydrofluoric acid catalysts. What makes these processes so