Coke deactivation and regeneration of HZSM-5 zeolite catalysts in the oligomerization of 1-butene

Abstract

The deactivation phenomenon of HZSM-5 catalysts (SiO2/Al2O3 ratio = 30–280) in the 1-butene oligomerization has been studied. Experiments were performed in a fixed-bed reactor at 175−325 °C; 1.5−40 bar; and, 2−6 g h molC−1. Used catalysts were analyzed by: temperature-programmed sweeping with N2 (TPS-N2), soluble coke analysis by gas chromatography/mass spectrometry (GC/MS); Fourier-transform infrared spectroscopy (FTIR); temperature-programmed oxidation (TPO), and; combined TPO/FTIR. The main deactivation cause is the oligomer (soft coke) confinement in the catalyst matrix, which depends on the reaction conditions (temperature and pressure). Soft coke is removed by TPS-N2 at 400 °C, whereas the remaining hard coke, by combustion. Two types of hard coke are distinguished, which are located in the catalyst matrix and in the zeolite micropores, being the second fraction more refractory to combustion. The low developed nature of soft coke facilitates catalyst regeneration, which is fully achieved by the combustion of hard coke at 500 °C.