The production of ethylene glycol from ethylene chlorohydrin and sodium bicarbon
ID: 530493 • Letter: T
Question
The production of ethylene glycol from ethylene chlorohydrin and sodium bicarbonate CH_20HCH_2Cl + NaHCO_3 rightarrow (CH_2OH)_2 + NaCl + CO_2 uparrow is carried out in a semibatch reactor. A 1.5-molar solution of ethylene chlorohydrins is fed at a rate of 0.1 mole/minute to 1500 dm^3 of a 0.75-molar solution of sodium bicarbonate. The reaction is elementary and carried out isothermally at 30degree C where the specific reaction rate is 5.1 dm^3/mol/h. Higher temperatures produce unwanted side reactions. The reactor can hold a maximum of 2500 dm^3 of liquid. Assume constant density. (a) Plot and analyze the conversion. reaction rate, concentration of reactants and products. and number of moles of glycol formed as a function of time. (b) Suppose you could vary the flow rate between 0.01 and 200 mol/min. What flow rate and holding time would you choose to make the greatest number of moles of ethylene glycol in 24 hours. keeping in mind the downtimes for cleaning. filling, etc., shown in Table 5-3? (c) Suppose the ethylene chlorohydrin is fed at a rate of 0.15 mol/min until the reactor is full and then shut in. Plot the conversion as a function of time.Explanation / Answer
The AUXILIARY EQUATIONS
K = 5.1 >Reaction Rate Constant, [dm3/mol.h]
r = K x Ca x Cb >Reaction Rate, [dm3/mol.h]
V = Vo + (Fao/1.5) x t > Volume, [dm3]
X = 1 - (Cb x V)/(0.75 x Vo) > Conversion
Nc = 0.75 x Vo x X > Moles of C formed
INITIAL CONDITIONS
Ca(0) = 0
Cb(0) = 0.75
Cc(0) = 0
Cd(0) = 0
Ce(0) = 0
Fao = 6 > Feed of A, [mol/h]
Vo = 1500 > Initial Volume, [dm3]
t(0) = 0 > Initial Time, [h]
t(f) = 250 > End Time, [h]
DIFERENTIAL EQUATIONS
d(Ca)/d(t) = - Kx Ca x Cb + (Fao/V) x (1-(Ca/1.5)) > Concentration of A
d(Cb)/d(t) = - K x Ca x Cb - (Fao x Cb)/(V x 1.5) > Concentration of B
d(Cc)/d(t) = K x Ca x Cb - (Fao x Cc)/(V x 1.5) > Concentration of C
d(Cd)/d(t) = K x Ca x Cb - (Fao x Cd)/(V x 1.5) > Concentration of D
d(Ce)/d(t) = K x Ca x Cb - (Fao x Ce)/(V x 1.5) > Concentration of E
By substituting the given values in the above equation we get reaction rate, conversions, concentration of reactants and products and number of moles of glycol formed as a function of time..
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