Yield of Ethylene and Propylene from Lighter Feedstock

Yield of Ethylene and Propylene from Lighter Feedstock 

Normal-butane gives very similar yields of ethylene and propylene to propane cracking. Methane is lower and more butadiene, C5 + aliphatic hydrocarbons and BTX are produced. 

Isobutane reverses the relative composition of the olefin products with the major olefin being propylene (over 30% ultimate yield), double the yield for propane or n-butane, with a commensurate high methane yield. A major product is isobutene. The ultimate ethylene yield is only about 7%. 

Note that in the yield of the desired olefins on a weight basis are about 80% for ethane and less than 60% of the other feeds. 

Of the gaseous feeds ethane, propane and n-butane are preferred for the production of ethylene and high isobutane content should be avoided. However, for some operations, propylene and isobutene are valuable products and butane streams of high isobutane content can be preferred . 

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