Chemical Engineering Journal 135S (2008) S254–S258 Novel design of a microstructured reactor allowing fast temperature oscillations M. Luther a,b,∗ , J.J. Brandner a , K. Schubert a , A. Renken b , L. Kiwi-Minsker b a Forschungszentrum Karlsruhe, Institute for Microprocess Engineering, D-76344 Eggenstein-Leopoldshafen, Germany b ´ Ecole Polytechnique F´ ed´ erale de Lausanne, CH-1015 Lausanne, Switzerland Abstract Two types of stainless steel microstructured reactors for catalytic gas-phase reactions have been developed and characterized with respect to their thermal behaviour under non-stationary temperature conditions. One of the reactors used (FTC-I) allowed periodic temperature changes up to 100 K with a frequency of 0.05 Hz. However, a broad temperature gradient of 80 K developed inside the reactor. A second reactor (FTC-II) enabled periodic temperature variations of maximum 60 K with a frequency of 0.06 Hz while avoiding temperature non-homogeneity. The CO oxidation taken as a test reaction was carried out over a Pt/Al 2 O 3 catalyst in the FTC-II reactor. In this way it was possible to study the effect of non-stationary temperature conditions on the reactor performance. A significant increase in CO conversion was observed with periodic temperature cycling as compared to values obtained under steady-state conditions. © 2007 Elsevier B.V. All rights reserved. Keywords: Microstructured reactor; Unsteady-state operation; CO oxidation; Temperature oscillations 1. Introduction Commonly chemical reactors are operated under station- ary conditions after optimization of their reaction parameters. Selectively imposed regular variations of reaction parameters like concentration, pressure or temperature improve the prod- uct selectivity and yield for some reactions. The values attained exceed steady-state values as shown by Silveston et al. [1]. In most of the studies on unsteady-state or periodic operation, the parameters to vary are pressure or concentration of the reactants, but not the reaction temperature. This is due to the high thermal inertia of conventional chemical reactors. In these reactors fast and reproducible temperature changes are difficult to obtain. The experimental study by Hansen and Joergensen [2] was the first report on the performance of fixed bed reactors under forced temperature variations. But the theoretically predicted increase in performance of catalytic reactor [3] has not been observed up to now. ∗ Corresponding author at: Forschungszentrum Karlsruhe, IMVT, Hermann- von-Helmholtz Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany. Tel.: +49 7247 826657; fax: +49 7247 823186. E-mail address: martin.luther@imvt.fzk.de (M. Luther). Microstructured reactors developed during the last decade have low thermal inertia and therefore allow temperature changes up to 100 ◦ C within few seconds [4]. This opens an opportunity to validate experimentally theoretical predic- tions. Brandner [4] recently reported the qualitative features of increased conversion under non-stationary temperature condi- tions compared to thermal steady-state reactor values. Catalytic CO oxidation was taken as the model reaction. This work provides quantitative data for an increase in CO oxidation rate under fast periodic temperature oscillations. We report two types of microstructured reactors, which have been developed and characterized towards this objective. 2. Experimental 2.1. Microstructured reactors The first microstructured reactor (FTC-I) used during this work has been discussed elsewhere [4,5]. It consists of three metal plates with eight holes for electric heater cartridges and three hole channels for thermocouples as presented in Fig. 1. Three cooling and two microstructured foils with reaction chan- nels are placed symmetrically above and under the central heating plate in alternating order. The reactor parts are made of 1385-8947/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2007.07.004