Question

E. Prodan and I.L Shahkova [Kinet.Catl.,24,891-894(1984)] studied the kinetics of the decomposition of trpolyphosphoric acid in aqueous solution :

H2O + H5P3O10 ----K1----> H4P2O7 + H3PO4
H4P2O7 + H2O -----K2----> 2H3PO4

Analysis of their earlier data indicates that at 40 celcius , the values of the pseudo first order rate constants k1 and k2 are .353 and 5.28*10^-3 h^-1 respectively. Consider the situation in whivh a stream is available containing H5P3O10, H4P2O7 and H3PO4 at concentrations 0.20, 0.004 and 0.004 M respectively.

a) Determine the space time for a single CSTR at which the effulent conecentration of H4P2O7 is a maximum . The reactor operates at 40 celcius. In addition determine the effluent concentrations of the three acids.

b) Repeat part (a) for the case in which these reactions are carried ouy in a cascade of two identical CSTRs, both operating at 40 celcius . In this case prepare plots of effluent comcentrations versus the space time for the cascade. Comment and indicate how your results would compare with optimum value of the space time for a PFR.

Answer 1

Solution:

a) The space time computation are expressed below,

b) by computing for we get V= 13.36 lt and the plot for series reaction between PFR vs CSTR is shown below, among them PFR is the best suitable reactor for series reaction to get ,aximum yield of product.