Sorption and diffusion parameters from vacuum-TPD of ammonia on H-ZSM-5

• Published in: Chemical engineering science 2013-02, Vol.89, p.40-48
• Main Authors: Kouva, Sonja, Kanervo, Jaana, Schüβler, Florian, Olindo, Roberta, Lercher, Johannes A., Krause, Outi
• Format: Article
• Language: English
• Subjects: adsorption; Ammonia; Chemical engineering; desorption; Dynamic tests; Dynamical systems; Dynamics; heat; Kinetics; Mass transfer; Mathematical modeling; NH3-TPD; Porous materials; Sorption; temperature; Transient response; Zeolites
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2012.11.025

This work aims at filling the gap in vacuum-TPD modeling methodology for microporous samples. The specific objective was to assess and distinguish external and internal mass transfer effects from the intrinsic sorption dynamics during temperature-programmed desorption, as illustrated by ammonia on H-ZSM-5. The external mass transfer pattern was confirmed to be free of bed-depth effects, the intraparticle mass transfer resistance proved to be significant in the ammonia-TPD system, and equipment-related artefacts showed to be negligible based on preliminary experiments. Thus a consistent set of 10 TPD curves was collected, including two adsorption temperatures, three heating rates and two separate particle fractions. The experimental data was successfully modeled with a system including intraparticle mass transfer phenomena and intrinsic sorption kinetics. By combining a transient kinetic approach to a well-designed set of high-quality experiments vacuum-TPD can provide decoupled information on mass transfer and sorption for porous materials as we demonstrate in this work. [Display omitted] ► TPD is widely used to characterize porous solids; also provides kinetic information. ► Novel modeling methodology is established to describe the vacuum-TPD system. ► TPD modeling results: intraparticle diffusion and adsorption equilibrium parameters. ► Example: NH3-TPD of H-ZSM-5—adsorption and mass transfer parameters are reported.