title: A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial tests.
abstract: The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic reduction (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amount of sorbed ammonia under reaction conditions. To support classical temperature-programmed desorption (TPD) experiments, a correlation of the dielectric properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a laboratory test setup, which enables direct measurements of the dielectric properties of catalytic powder samples under a defined gas atmosphere and temperature by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at constant temperatures of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia.
authors.affiliation: Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. Markus.Dietrich@uni-bayreuth.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Dietrich
authors.affiliation: Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. Dieter.Rauch@uni-bayreuth.de.
authors.forename: Dieter
authors.initials: D
authors.lastname: Rauch
authors.affiliation: School of Engineering, Cardiff University, Cardiff, CF24 3AA, Wales, UK. PorchA@cardiff.ac.uk.
authors.forename: Adrian
authors.initials: A
authors.lastname: Porch
authors.affiliation: Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. Ralf.Moos@Uni-Bayreuth.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Moos