Studies to the Functioning of Automotive Exhaust Catalysts Using In-Situ Positron Emission Tomography

Mass Transfer of Alkanes in Zeolite Packed-Bed Reactors Studied with Positron Emission Profiling. 2. Modeling

“…This situation stresses the importance of the need for different mass transport properties of reactant and reaction product in the PEP experiments. This requirement was fulfilled in the experiments of Jonkers and co-workers (Jonkers et al, 1992;Vonkeman et al, 1991), but in a biporous bed this requirement is probably only achievable with a significant difference in the effective microparticle diffusion coefficient of reactant and reaction product. Even when this condition is met, the shape of the PEP profiles is only directly influenced by the reaction when micropore diffusion is the dominant contribution in the second moment of the PEP profiles.…”

“…This detection system is the one-dimensional analog of the detection systems used in nuclear medicine for positron emission tomography (PET) and provides information on the concentration distributions of reactants and products as a function of time and position along a reactor bed. The first study in which the PET technique was applied in catalysis as an in situ probe for reaction kinetics deals with the oxidation of 11 CO on Pt/CeO 2 /Al 2 O 3 (Jonkers et al, 1992;Vonkeman et al, 1991). In that study, the reaction kinetics was modeled using the rates of the elementary adsorption/desorption and reaction steps.…”

A Simplified Coldstart Catalyst Thermal Model to Reduce Hydrocarbon Emissions

“…Detailed physical models, based on fundamental chemical and thermofluidic dynamic principles of reacting flows, e.g. (Vonkeman, 1991). These models include the effects of heat and mass transfer in three dimensions and account for the change in composition of the exhaust gases as they continually react with each other in the catalytic environment.…”