CATALYTIC
REFORMING
Catalytic reforming is a chemical process used to convert petroleum
refinery naphthas, typically having low octane ratings, into
high-octane liquid products called reformates. Reformates are
components of high octane gasoline . It is also known as petrol.
The most important reactions occuring
are :
1.
Dehydrogenation of
naphthenes
2.
Dehydrocyclisation of paraffins
3.
Isomerisation
4. Dehydroisomerisation
Dehydrogenation is
a chemical reaction that involves the elimination of hydrogen (H2).
It is the reverse process of hydrogenation.
catalytic dehydrocyclization. A reaction in which an alkane is
converted into an aromatic hydrocarbon and hydrogen. For example, heptane →
toluene + 4H2
isomerisation is
the process by which one molecule is transformed into another molecule which
has exactly the same atoms, but the atoms are rearranged e.g. A-B-C → B-A-C
(these related molecules are known as isomers
Reforming is a process which uses heat, pressure and a catalyst (usually
containing platinum) to bring about chemical reactions which upgrade naphthas
into high octane petrol and petrochemical feedstock. The naphthas are
hydrocarbon mixtures containing many paraffins and naphthenes. In Australia,
this naphtha feedstock comes from the crudes oil distillation or catalytic
cracking processes, but overseas it also comes from thermal cracking and
hydrocracking processes. Reforming converts a portion of these compounds to
isoparaffins and aromatics, which are
used to blend higher octane petrol.
- paraffins are converted to
isoparaffins
- paraffins are converted to
naphthenes
- naphthenes are converted to aromatics
- The catalyst employed in reforming is bifunctional in nature consisting of a noble metal supported on alumina. Catalytic reforming is done without significantly changing their carbon numbers. Basically, the process re-arranges or re-structures the hydrocarbon molecules in the naphtha feedstocks as well as breaking some of the molecules into smaller molecules.
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catalyst
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||||||
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heptane
|
->
|
toluene
|
+
|
hydrogen
|
||
C7H16
|
->
|
C7H8
|
+
|
4H2
|
catalyst
|
||||||
|
cyclohexane
|
->
|
benzene
|
+
|
hydrogen
|
||
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C6H12
|
->
|
C6H6
|
+
|
3H2
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