Promotional effects of rare-earth (La, Ce and Pr) modification over HZSM-5 for methyl mercaptan catalytic decomposition

A series of rare earth elements (La, Ce and Pr) modified HZSM-5 catalysts were synthesized by incipient wetness impregnation method and then characterized by XRD, N-2 adsorption-desorption, SEM, CO2-TPD, NH3-TPD, and FT-IR measurements. Their catalytic behaviors toward methyl mercaptan decomposition reactivity were investigated. The results indicated that rare earth modified HZSM-5 catalysts demonstrated improved catalytic activity, which significantly reduced the reaction temperature for complete conversion of CH3SH, and La modified HZSM-5 catalyst exhibited higher activity than Ce and Pr doped HZSM-5 catalysts. CH3SH can be almost completely converted over 5%La/HZSM-5 at 450 degrees C compared to pure HZSM-5 at 600 degrees C. Moreover, 5%La/HZSM-5 showed high stability and no notable deactivation was observed during 30 h on stream. The improvement in catalytic performance can be attributed to the regulated acid base properties of the HZSM-5 catalysts by rare earth metal doping. Comparisons between spent HZSM-5 and spent La doped HZSM-5 catalysts were done using Raman and TG techniques. Furthermore, the optimal loading amount of La was investigated, and 9 wt% and 13 wt% La/HZSM-5 catalysts exhibited better catalytic activity. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.