Micro structured reactors


Micro structured reactors or more general structured catalyst systems are most probably the needed counter part in the development of advanced processes. Despite the fact that modern methodologies like “combinatorial catalysis (link)” or a development of nano structured materials yield state-of-the-art superior catalyst formulations, there are prominent examples where powder / shaped particles in a fixed bed configurations have severe drawbacks. Major processes in chemical industry or energy technology would not be possible with conventional reactors. For example the catalyst in fluid catalytic cracking [1] (installed worldwide process capacity: 86,000,000 tons / year in 1997 just for residuals processing [2]) cokes within seconds and needs to be regenerated frequently. This is easily accomplished by reaction engineering measures in the Kellogg-orthoflow process using a riser-regenerator configuration. Other reactions like the ammoxidation of propylene in the Sohio process [3] (installed worldwide process capacity: 4,000,000 tons / year in 1983) require an evacuation of the reaction heat (∆Hr = -515 kJ/mol of acrylonitrile) that can hardly be accomplished in normal fixed beds. Moreover, reactions that still allow to be carried out in fixed beds, e.g. the selective oxidation of ethylene to ethylene oxide [4] (installed worldwide process capacity: 15,000,000 tons / year in 2000) lead to massive costs for multi tubular reactors (up to 10,000 individual tubes per reactor) to be operated selectively and safely.


Just the few examples above highlight the importance of process engineering in terms of heat management. However, in many cases the catalysts required are not suitable for operation in fluidized beds and multi-tubular reactors cause high investment costs. Furthermore, flexible adjustment of production capacity and an intrinsically more save design of reactors are often desired. Hence, micro structured reactors [5] promising major advances in this field are desirable configurations, as the have already shown their potential in these examples:


1) Secure operation when reacting an explosive stoichiometric hydrogen-oxygen mixture [6]:




2) The oxidation of ethylene to ethylene oxide [5]:




Activities on structured catalyst systems by the group aim on maintaining the advantage of low service needs in new advanced reactor configurations. The research spectrum is as wide as:



[1] W.W. Irion, O.S. Neuwirth; “Oil refining” in “Ullmanns encyclopedia of industrial chemistry” 6th edition (2003), Vol. 24; Wiley-VCH, Weinheim;  p. 205-256

[2] based on “OGC Special” Oil Gas J. 95 (Dec. 22 1997); p. 41-44

[3] P.W. Langvardt; “Acrylonitril” in “Ullmanns encyclopedia of industrial chemistry” 6th edition (2003), Vol. 1; Wiley-VCH, Weinheim;  p. 307-315

[4] S. Rebsdat, D. Mayer; “Ethylene oxide” in “Ullmanns encyclopedia of industrial chemistry” 6th edition (2003), Vol. 12; Wiley-VCH, Weinheim;  p. 609-635

[5] W. Ehrfeld, V. Hessel, V. Haverkamp; “Microreactors” in “Ullmanns encyclopedia of industrial chemistry” 6th edition (2003), Vol. 22; Wiley-VCH, Weinheim;  p. 1-31

[6] M.T. Janicke, H. Kerstenbaum, U. Hagendorf, F. Schüth, M. Fichtner, K. Schubert; J. Catal. 191 (2000); p. 282-293