The synthesis of aspirin (ASA = C_9 H_8 O_4) takes place according to the follow

Question

The synthesis of aspirin (ASA = C_9 H_8 O_4) takes place according to the following reaction (in the liquid phase): The reaction is carried out in a batch reactor. After some time of reaction, the contents of the reactor are discharged to a crystallizer to recover aspirin. Suppose that the reaction is elementary with kinetic rate constant k, and the reactor is isothermal with constant mass density. If k = 0.30 l/mol-h, and the initial concentrations of salicyclic acid (SA), acetic acid (ACA), and acetic anhydride (AA) are 2.8, 2.8, and 4.2 mol/l, respectively. a) Plot C_SA versus time. b) What will be the concentrations of SA, AA, ACA, and aspirin after 2 hours?

Explanation / Answer

The equation for conversion vs time for SA in a batch reactor is and the reaction is elementary ( overall reaction is 2nd order) and for second order reaction the relation between conversion and rate constant are

2 After 2 hr, from the best fit equation, CA= -0.65*ln(2) +1.095=1.54 moles/L

This is the concentration of saliyclic acid .

Concentration of acetic anhydride after 2 hrs can be obtaine from

CAOXA= CBO*XB

XA= 0.56

XB= 2.8*0.56/4.2 =0.373 and CB= CBO*(1-XB)= 4.2*(1-0.373)= 2.63 moles/L

SAA = CAO+ CAO*XA = 2.8+0.56*2.8= 4.368 moles/L

CAO K M XA ln(M-XA)/(M*(1-XA) CAO*(M-1)*K t= ln(M*(1-XA)/(M*(1-XA)/CAO*(M-1)*K (hr) CA=CAO*(1-XA) 2.8 0.3 1.5 0.1 0.036367644 0.42 0.086589629 2.52 2.8 0.3 1.5 0.2 0.080042708 0.42 0.190577875 2.24 2.8 0.3 1.5 0.3 0.133531393 0.42 0.317931887 1.96 2.8 0.3 1.5 0.4 0.200670695 0.42 0.47778737 1.68 2.8 0.3 1.5 0.5 0.287682072 0.42 0.684957315 1.4 2.8 0.3 1.5 0.6 0.405465108 0.42 0.965393115 1.12 2.8 0.3 1.5 0.7 0.575364145 0.42 1.369914631 0.84 2.8 0.3 1.5 0.8 0.84729786 0.42 2.017375858 0.56 2.8 0.3 1.5 0.9 1.386294361 0.42 3.30070086 0.28

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