"Stopped-flow desorption" analysis of the nature of strongly adsorbed species during n-butane oxidation in a flow reactor

The presence and the evolution as a function of time of strongly adsorbed species during n-butane oxidation in a flow reactor was studied by "stopped-flow desorption" experiments and by thermogravimetric and Fourier-transform infrared analyses on a (VO)2P2O 7 catalyst highly active/selective in the conversion of n- butane to maleic anhydride. In particular, the presence of an adsorbed species was found which desorbs as crotona1dehyde only at temperatures around 100 K higher than the reaction temperature (573 K). The parallel increase in the amount of this species formed with the change in catalytic behavior (a decrease in the rate of n-butane depletion with a parallel increase in the rate of maleic anhydride formation) suggests that due to the reduced turnover number, the formation of strongly adsorbed species causes catalyst deactivation by site blocking, but at the same time allows controlled reactivity of the surface which prevents the consecutive oxidation of maleic anhydride to carbon oxides. © 1987 Elsevier Science Publishers B.V.