Question

Ethanol (EtOH) can be produced by the hydration of ethylene, C2H4 + H2O ? C2H5OH, at 300?C and high pressure with a phosphoric acid catalyst. Downstream of the reactor, a condenser is used to separate the product, which contains only EtOH and H2O, from a recycle stream that mixes with the fresh feed before entering the reactor. The fresh feed contains 30 mol% C2H4 and the remainder is steam. The single pass conversion is 20%.
a. Draw and label the process flowchart. (4)
b. Determine how many moles of product are produced per mole of fresh feed. (5)
c. Determine how many moles of ethylene are recycled per mole of fresh feed. (4)
d. What is the overall conversion of ethylene? (2)
e. If inert species are present in the feed, what other type of stream will be required in the process? (2)

Answer 1

molar mass of Ethanol (C2H5OH) = 46 g/mol

molar mass of water (H2O) = 18 g/mol

molar mass of Ethylene (C2H4) = 28 g/mol

C2H4+H2O-->C2H5OH

a) To draw & lable process flow chart

b)

to determine the moles of product produced per mole of fresh feed

for steady state reactor

consider F= 100 mol/h

M =F+R

M=100+R

as there is 20% single pass conversion of ethylene

80% unreacted ethylene is recycled back

ethylene in mixed feed = 30+R

0.80 *(30+R)=R

0.2R=24

R=120 mol/h

M=220 mol/h

moles of ethylene in mixed feed=150 mol/h

30 moles of ethylene reacts in reactor per pass so 30 moles of water will react & unreacted water(i.e 40 moles) & ethanol produced 30 moles will be separated as product

therefore ,

P=70moles/h

therefore moles of product produced per mol of fresh feed = 30/100=0.3

as our product is ethylene 30 mol are produced per 100 moles of fresh feed

c.

to determine how many moles of ethylene recycled per mole of fresh feed

in above part we got

R= 120 mol/h

so R/F = 120/100 = 1.2

d.to calculate overall conversion of ethylene

overall conversion of ethylene = (moles of ethylene in fresh feed - ethylene in output of overall process)/moles of ethylene in fresh feed

overall conversion of ethylene =(30-0)/30 = 1

e.

If inert species are present in feed we need purge stream in the process to stop the aacumulation of inert in the system .