(247c) Boosting Catalytic Activity By Forced Dynamic Operation of Catalytic Reactors

The influence of dynamic operating conditions on catalytic reaction systems has been an inherent topic of emission control devices, because in common automotive applications, the chemical composition temperature, and mass flows of the exhaust gases vary inherently due to the dynamic operation of the vehicle. Exhaust-gas after-treatment systems for stationary applications experience way less transients, reactors in chemical industry are usually designed for steady-state operation. Since many investigations show that the structure of solid catalysts, and thus their catalytic activity, vary significantly with reaction conditions, dynamic operation is of great interest for another reason: the enhancement of catalyst performance by forced dynamic operation. In this contribution we will highlight some recent achievements in boosting catalytic activity by forced dynamic operation of catalytic reactors with a special focus on recent research obtained at the University of Houston, namely Michael P. Harold and colleagues (e.g., [1, 2]), and in our group at KIT. Two of the examples are listed below.

1. Forced dynamics can be used to mitigate water inhibition in Pd-Pt catalysts for methane oxidation supported on alumina and a ceria-zirconia mixed oxide, which are commonly used in the exhaust tailpipe of lean-burn engines running on natural gas or renewable biogas. Analysis of spatially resolved concentration and temperature profiles indicates that introducing hydrogen into the lean reaction mixture generates significant heat and enhances methane conversion. [2]

2. The impact of temperature, amplitude, split cycle, mean lambda, gas hourly space velocity, and oxygen storage capacity on average pollutant conversion and product selectivity of three-way catalysts was investigated in periodic operation. [3]