A
hydrotreater is a common
process unit in an
oil refinery that is used to treat products such as
gasoline,
kerosene,
diesel, and intermediates such as
gasoil. A hydrotreater uses
hydrogen to saturate aromatics and
olefins as well as to remove undesirable compounds of elements such as
sulfur and
nitrogen.
Common major elements of a hydrotreater unit are a heater, a fixed-bed catalytic reactor and a hydrogen
compressor. The catalyst promotes the reaction of the hydrogen with the sulfur compounds such as mercaptans to produce
hydrogen sulfide or H2S, which is then usually bled off and treated with
amine in an amine treater. The hydrogen also saturates
hydrocarbon double bonds which helps raise the stability of the fuel.
A hydrocracker is a some-what similar refinery unit that uses higher severity such as a stronger catalyst and higher
pressure to crack hydrocarbon molecules into smaller ones, for example to convert gasoil and diesel to lighter hydrocarbons such as gasoline blending stocks and
butanes. A hydrocracker usually has a hydrotreater as the first step to remove the sulfur and nitrogen compounds that could act as a poison to the hydrocracking catalyst.