| Abstrakt: |
Results previously obtained for the oxidation ofo-xylene ando-tolualdehyde over a 1% V2O5/TiO2catalyst have been subjected to mathematical modelling, using comprehensive “rake” networks which incorporate adsorbed intermediates, a variety of routes to CO2, and provision for the formation and removal from the surface of a “residue” formed at low conversion by both reactants. Equations representing yields of products as a function of reactant conversion are presented; these contain series of parameters that are complex functions of the rate constants for the individual steps, their values being obtained by regression analysis. The modelling confirms that phthalic anhydride is formed through a sequential process involving adsorbed forms ofo-tolualdehyde and phthalide as intermediates, but it is not formed by direct conversion ofo-xylene ando-tolualdehyde. At high conversion, phthalic anhydride selectivity generally passes through a maximum, showing that it can undergo further oxidation to CO2. The selectivity for the “residue” (SR) also passes through a maximum as it is removed from the surface; moreover, the initial slopes ofSRvs conversion curves show that the “residue” is formed early in the reaction network. |
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