Question

Acetylene is hyrodgenated to form ethane. The feed to the reactor contains 1.30 mol H₂/mol C₂H₂. The reaction proceeds to completion.

a. Calculate the stoichiometric reactant ratio (mol H₂ reacted/mol C₂H₂ reacted) and the yield ratio (mol C₂H₆ formed/mol H₂ reacted).

b. Determine the percentage by which acetylene is in excess.

c. Calculate the mass feed rate of hydrogen (kg/s) required to produce 4.00 x 10⁶ metric tons of ethane per year, assuming that the reaction goes to completion and that the process operates for 24 hours a day, 300 days a year.

Answer 1

The balanced reaction

C2H2 + 2H2 => C2H6

In the feed

Mol H2 / mol C2H2 = 1.30

Part a

stoichiometric reactant ratio

mol H2 reacted/mol C2H2 reacted = 2

yield ratio

mol C2H6 formed/mol H2 reacted = 1/2 = 0.50

Part b

From the stoichiometry of the reaction

2 mol H2 required = 1 mol C2H2

1.30 mol H2 required = 1.30/2 = 0.65 mol C2H2

Excess reactant = C2H2

% C2H2 in excess = (1 - 0.65)*100/1 = 35%

Part c

mass feed rate of hydrogen =?

Ethane formed = 4*10^6 MT/year

30 MT ethane formed from = 4 MT H2

4*10^6 MT/year ethane formed from = 4*4*10^6/30 = 5.33*10^5 MT/year H2

Mass of H2 required

= 5.33*10^5 MT/year x 1000kg/MT x 1year/300days x 1day/24hr x 1hr/3600s

= 20.576 kg/s