Miniaturization of screening devices for the combinatorial development of heterogeneous catalysts

The present work is focused on the determination of the advantages, bottlen ecks and challenges of miniaturized screening systems which are essential t o the success of combinatorial high-throughput methodologies in heterogeneo us catalysis. Two different reactor configurations with different degrees o f n-minaturization were developed for the parallel and fast screening of he terogeneously catalyzed gas phase reactions: a monolithic reactor system ac ting as a multichannel reactor and a microreaction system based on microfab rication techniques. In both cases, a scanning mass spectrometry technique was successfully applied for quantitative product analysis within 60 s per catalyst. Due to its flexibility and high spatial resolution, this three di mensional scanning MS can be used with different and highly parallel reacto r arrays. Many experiments were carried out to study the efficiency and rel iability of the different screening systems, with the oxidation of methane, the oxidation of CO, and the oxidative dehydrogenation of i-butane as mode l reactions. Moreover, chip modules in silicon-glass technology having a nu mber of parallel microchannels were developed, each of them containing a di fferent catalyst. Using this approach, "catalysis-on-a-chip" proved in meth ane oxidation was possible. Finally, a multibatch reactor consisting of a n umber of parallel mini autoclaves was developed and tested in the liquid-ph ase hydrogenation of citral in order to overcome the lack of parallel and f ast screening procedures for heterogeneously catalyzed gas-Equid reactions widely spread in the chemical industry. (C) 2001 Elsevier Science B.V. All rights reserved.