1. A catalytic reactor is used to produce formaldehyde from methanol by the reac

Question

1. A catalytic reactor is used to produce formaldehyde from methanol by the reaction: CH3OH HCHO right arrow H2 The gases exit the reactor at 343 degree C and 13.7 atm with the formaldehyde produced having a partial pressure of 4.1 atm. The methanol exiting the reactor is separated from the formaldehyde and hydrogen in a separator. The formaldehyde and hydrogen gases exit the separator at 25?C and 13.7 atm at 100 m3/hr. The methanol is recycled back to the reactor. Determine the molar flowrate (moles/hr) of methanol in the recycle stream. Given: Tc (formaldehyde) = 414.3 K, pc (formaldehyde) = 66.9 K

Explanation / Answer

moles of formaldehyde formed = moles of H2 formed

for the mixture leaving the reactor, T =343oC = 616 K

mole fraction of formaldehyde = mole fraction of H2 = 4.1/13.7

mole fraction of unreacted methanol = 5.5/13.7

when formaldehyde + H2 leave reactor

flow rate = 100 m3/hr , T =298K

for 100m3 , number of moles = pv/RT = (13.7 X 105)*(100)/ 298 * 8.314 = 55296 moles

so flow rate in moles/hr = 55296 moles/hr

now ratio of moles of unreacted methanol to (formaldehyde + H2 formed) = 5.5/(4.1+4.1) = 0.670731

so flow rate of unreacted methanol = flow rate of methanol in recycle stream = 0.670731*55296 moles/h

= 37088.741 moles/hr ........Ans

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