Catalyst deactivation is usually indispensable, although the rate at which it occurs varies greatly. At first, this article discusses the causes of deactivation in a commercial hydrocracking unit called Isomax. Then, a 5-lump kinetic model including catalyst decay function for hydrocracking of vacuum gas oil in a commercial plant is proposed. The model considers vacuum gas oil (VGO) having boiling point higher than 380oC (380+°C), diesel (260-380°C), kerosene (150-260°C), naphtha (IBP:150°C), and gas as products. By using selective catalyst decay function in the kinetic model, the effect of the catalyst deactivation on the yield of products over time is studied. The prediction of the model during 1.5 years is in good agreement with the actual commercial data. The average absolute deviation (AAD%) of the model for the strategic products like naphtha, kerosene and diesel are about 1.784%, 1.983% and 1.971%, respectively. Also it is observed that the estimated parameters are consistent with the reported characteristics of amorphous catalysts.
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