ANHYD - Oxidation of -Xylene to Phthalic Anhydride

Ortho-xylene (A) is oxidised to phthalic anhydride (B) in an ideal, continuous flow tubular reactor. The reaction proceeds via the complex consecutive parallel reaction sequence, shown below. The aim of the reaction is to produce the maximum yield of phthalic anhydride and the minimum production of waste gaseous products (C), which are CO2 and CO. 

The reaction is carried out with a large excess of air, and the total gas mass flow rate can be taken as constant. 

Detailed modelling of the fixed bed production of phthalic anhydride from o-xylene is discussed by Froment and Bischoff (1990), involving both axial and radial temperature profile effects. 

It is assumed that the mole fraction of oxygen does not change, owing to the large excess of air. 

Considering Fig. 5.77, the steady-state balance around any segment AV, for component A, is given by 

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