Prediction of catalyst lifetime from short-term experimental results: A case study on dehydrogenation of heavy n-paraffins over Pt-based catalysts

Abstract

The deactivation behavior of Pt-based catalysts in dehydrogenation of normal paraffins was investigated by different methods to elucidate the long-term behavior from short-term (10–100 h) data. Empirical power-law, kinetic modeling and accelerated deactivation tests were employed for analysis of the rate data. The methods were evaluated for extrapolating the conversion-time data using long-term (700 h) test results (temperature 475˚C, pressure 1.7 bar, H₂/HC=6 mol/mol, liquid hourly space velocity 20 h⁻¹) of a benchmark commercial catalyst in a fixed-bed reactor. The fresh and used catalysts were characterized by BET, XRF and TG-DTA methods. The kinetic model showed superior results in predicting the deactivation trend. It was used to compare the effect of Li and Mg promoters on a multimetallic catalyst. From the kinetic parameters of the model the order of activity was Pt-Sn-In-Mg/Al₂O₃ > Pt-Sn-In/Al₂O₃ > Commercial > Pt-Sn-In-Li/Al₂O₃ and the order of stability was Pt-Sn-In-Li/Al₂O₃ > Pt-Sn-In/Al₂O₃ > Pt-Sn-In-Mg/Al₂O₃ > Commercial.