Alkanes
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What is catalytic reforming and octane rating?
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Ulex writes
Catalytic reforming is a process which takes place in an oil refinery. I’m sure you know what ‘cracking’ is. Well, reforming takes place at the same time; cracked hydrocarbon fragments re-join or alter in a variety of reactions to give hydrocarbons which were not there in the original crude oil fraction. By varying the conditions (temperature, catalyst) the reforming can be controlled so as to give products with desirable and saleable properties.
‘Octane rating’ is a way of grading hydrocarbon fuels which are to be used in petrol-driven engines. Modern high-performance engines ignite a mixture of petrol vapour and air using a spark generated electrically at a precisely defined moment. It can happen, however, that the minute carbon particles produced in combustion can do the igniting of the next charge of mixture before the spark gets there. This is called pre-ignition or ‘knocking’ and results not only in a nasty noise but also loss of power.
A careful blend of fuel can minimise this problem. Actual fuels are rated on their ability to minimise knocking, heptane being given a rating of 0 and 2,2,4-trimethyl pentane (otherwise called iso-octane) being given a rating of 100. This is the so-called ‘octane’ scale.
Risk assessment
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updated: 21 February 2009
