Question

During the process of preparing ethylene from the cracking of pure ethane, the conversion per pass of ethane is 60%. If 46.4kg of ethylene can be obtained from 100kg of ethane which was input into the cracker. After the separation of pyrolysis gas, most of the unreacted ethane is recycled back to the cracker (suppose the circulating gas is only ethane). It is also known that the products still contain 4kg of ethane except ethylene and other gases. Question: Please figure out the selectivity, the yield per pass, the total yield and the total mass yield of ethylene, as well as the total conversion of ethane. Notice: you can draw the block diagram of circulation process firstly.

Answer 1

C₂H₆ <=>C₂H₄ + H₂

Conversion per pass is 60%

From stoichiometry it is clear from 30 gram of ethane 28 gram of ethylene is obtained.

So 46.4 kg of ethylene is obtained from nearly 77.6 kg of ethane. Since conversion is 60%

And remaining 22.4kg of ethane will be responsible of forming 12.54 kg

Since 4kg of ethane is not converted to ethylene so 2.23kg of ethylene is not formed.

Total yield of ethylene 46.4+12.54-2.23 = 56.71 kg