Catalytic dehydrogenation of ethane to produce ethylene: C2H6 -> C2H4 + H2 Endot

Question

Catalytic dehydrogenation of ethane to produce ethylene:

C2H6 -> C2H4 + H2

Endothermic rxn. Temp. must be above 500 degrees fahrenheit for rxn to move forward. Will be placing a steam coil to reactor that circulates steam at 650 psia saturated through coil. A steam trap at low point of coil allows condensate to be removed. (Reactor is well insulated and heat loss negligible)

a) If it does work, how much steam is required per mole of ethylene produced?

b) If doesn't work, use own values to find flow rates of heating fluids.

Explanation / Answer

Look up steam @ 650 psia in steam tables:

T=4950F (from table @ 650 psia)

So this will not work because it is not above 5000F. Pick another pressure: 750 psia --> T=5110F & H=1200.6 Btu/lbm (tables).--> 1200.6 Btu/lbm * ((1KJ/kg)/(.43Btu/lbm))=2792.1 KJ/kg

Now the standard heat of reaction for the ethane to ethylene and hydrogen: 52.28-(-84.67)=136.95 KJ/mol.-->136.95 KJ/mol*(1mol/.028kg)=4891.07 KJ/kg ..>

4891.07/2792.1=1.75kg steam/kg ethylene --> 1.75 kg/kg*.028kg/mol= .049 kg steam/mol ethylene

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