Critical evaluation of in situ probe techniques for catalytic honeycomb monoliths

• DOI: 10.1016/j.cattod.2013.05.005
• Publication Date: 2013-06-06T04:18:41Z
• Authors: Matthias Hettel; Claudia Diehm; Bentholhoda Torka...; Olaf Deutschmann
• Keywords: Monolith; Isothermal process; Honeycomb

Abstract Collecting spatially resolved gas-phase concentration profiles in catalytic monoliths by applying suction probe techniques has become an important tool for understanding the reaction sequence and for optimizing the design of structured catalysts. Here, the significance of the probing technique’s impact on the measured data is investigated by means of CFD simulations and experimental investigation of catalytic partial oxidation of CH 4 on a Rh-coated honeycomb catalyst. Different positions of a suction probe (diameter = 170 μm) inside a rectangular channel (height = 795 μm) of a monolith are compared with respect to the influence on flow field, residence time, and reaction progress. The influence of the probe on the measured data is shown to strongly depend on its position. The maximum error can be over 50% with respect to the residence time. For an isothermal process, the error in the concentration profiles can be corrected by using a function which is only dependent on the geometrical structure of the monolith. However, for a process with a temperature gradient along the catalytic channel, such as CPOX of methane, the correction function is not applicable. An appropriate comparison of experiments and simulations requires a three-dimensional CFD simulation taking the probe into account.