By fractionation, we can separate crude into its constituent fractions. Chemical treatment on these fractions will yield newer quality products. The chemical processing brings about changes in the molecular masses and the structures of raw materials. Cracking and reforming are the two major processes involved here. Cracking involves a change in the molecular mass and reforming alters the molecular structure. Cracking is a process by means of which crude petroleum with long chain hydrocarbons splits into smaller fragments such as kerosene, petrol and diesel. Cracking is usually accompanied by secondary processes where small molecules recombine to give branched chain alkanes, alkenes and aromatic hydrocarbons. Thermal cracking and catalytic cracking are the main two cracking processes. Reforming method is employed to enhance the octane number of petrol fraction and to produce aromatic hydrocarbons for use as feed stocks in the synthesis of petrochemicals. In this method, molecular arrangement of hydrocarbons is made possible without any change in the number of carbon atoms to form new compounds. The process is brought about by passing the petroleum fraction at about 500 degree temperature over platinum coated on alumina catalyst.
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