A mathematical model based on 34days continuous operation of an industrial isomerization unit was developed. The unit involves a radial-flow reactor with a catalyst capable of converting xylenes and ethylbenzene to mixed xylenes. The catalyst contains EU-1 zeolite, platinum, and alumina as binder. Two reactions are considered, i.e., ethylbenzene isomerization and xylene isomerization. The rates are based on the Hougen-Watson model according to the literature. An optimization procedure based on the trust-region-reflective algorithm was carried out in order to obtain new kinetic constants that minimize the difference between the actual and the calculated values. The standard error of the parameters estimated was calculated through the deleted-one Jackknife method.