Question

Hydrogen Cyanide (HCN), an important reactant for the synthesis of numerous products, is produced catalytically from methane, ammonia, and oxygen in the following reversible reaction: CH4 + NH3 + 3/2O2 ------> HCN + 3H2O

A continuous reactor is designed to produce HCN at 2 kmol/min. Air is fed continuously to supply the oxygen (O2), so nitrogen is present as an inert. The oxygen is the limiting reactant and the ammonia (NH3) and methane (CH4) are fed at a 20% and 35% excess, respectively. No HCN is fed and oxygen conversion has been measured at 80%. Determine the feed and product compositions (mole%), the total feed and product flowrates (kmol/min) and the extent of reaction (kmol/min).

Answer 1

CH4 + NH3 + 3/2 O2 ------> HCN + 3H2O

O_{​​​​​​2} is the limiting reactant

2 moles of HCN formed at 80% conversion

Stoichiometrically moles of O_{​​​​​​2} = 2/0.8 × 1.5 = 3.75 moles

Nitrogen fed = 300× 79 ÷ 21 = 14.107 moles

Stoichiometrically CH_{​​​​​4} required = 2.5 moles

CH_{​​​​​4} fed = 35% excess = 1.35 × 2.5 = 3.375 moles

Stoichiometrically NH_{​​​​​3} required = 2.5 moles

NH_{​​​​​3} = 20% excess = 1.2 × 2.5 = 3 moles

Oxygen converted = 80%

Oxygen remaining = 3.75 × 0.2 = 0.75 moles

CH_{​​​​​4} ​​​reacted = 2.5 × .8 = 2 moles

CH_{​​​​​4} remaining = 3.375 - 2 = 1.375 moles

NH_{​​​​​3} reacted = 2 moles

NH_{​​​​​3} remaining = 3 - 2 = 1 mole

HCN formed = 2 moles

H_{​​​​​​2}​​​​​O formed = 3×2 = 6 moles

Feed composition

product composition