Microreactor selection

Improvement of product yield and selectivity in microreactors by combining fluid segments of different concentrations and sizes... 

We have studied the steady-state kinetics and selectivity of this reaction on clean, well-characterized sinxle-crystal surfaces of silver by usinx a special apparatus which allows rapid ( 20 s) transfer between a hixh-pressure catalytic microreactor and an ultra-hixh vacuum surface analysis (AES, XPS, LEED, TDS) chamber. The results of some of our recent studies of this reaction will be reviewed. These sinxle-crystal studies have provided considerable new insixht into the reaction pathway throuxh molecularly adsorbed O2 and C2H4, the structural sensitivity of real silver catalysts, and the role of chlorine adatoms in pro-motinx catalyst selectivity via an ensemble effect. 

Jahnisch, K., Baerns, M., Hessel, V, Haverkamp, V, Lowe, H., Wille, C., Selective reactions in microreactors -fluorination of toluene using elemental fluorine in a falling film microreactor, in Proceedings of tlie 37tli ESF/EUCHEM Conference on Stereocliemistry (13-19 April 2002), BUrgenstoclc, Switzerland. 

OS 34] [R 17] [R 19] [R 26] [P 23] By performing naphthalene nitration with fuming HNO3 in micro reactors, the selectivity for mononitronaphthalenes can be significantly enhanced (Figrue 4.48) [98]. The selectivity could be raised to more than 95%, independent of the microreactor used. 

However, the detailed description of the FT product distribution together with the reactant conversion is a very important task for the industrial practice, being an essential prerequisite for the industrialization of the process. In this work, a detailed kinetic model developed for the FTS over a cobalt-based catalyst is presented that represents an evolution of the model published previously by some of us.10 Such a model has been obtained on the basis of experimental data collected in a fixed bed microreactor under conditions relevant to industrial operations (temperature, 210-235°C pressure, 8-25 bar H2/CO feed molar ratio, 1.8-2.7 gas hourly space velocity, (GHSV) 2,000-7,000 cm3 (STP)/h/gcatalyst), and it is able to predict at the same time both the CO and H2 conversions and the hydrocarbon distribution up to a carbon number of 49. The model does not presently include the formation of alcohols and C02, whose selectivity is very low in the FTS on cobalt-based catalysts. 

Fig. la-e. Selected microreactors, a Stainless steel microreactor system designed by Ehrfeld Mikrotechnik. b Glass microreactor (Watts and Haswell 2005). c Stainless steel microreactor of the CYTOS Lab system (http //www.cpc-net.com/cytosls.shtml). d Silicon-based microreactor designed by Jensen (Ratner et al. 2005). e Glass microreactor of the AFRICA System... 

Chambers RD, Holling D, Spink RCH, Sandford G (2001) Elemental Fluorine - Part 13. Gas-Liquid Thin Film Microreactors for Selective Direct Fluori-nation. Lab Chip 1 132-137... 

Chambers RD, Fox MA, Sandford G (2005) Elemental fluorine - Part 18. Selective Direct Fluorination of 1,3-Ketoesters and 1,3-Diketones using Gas/ Liquid Microreactor Technology. Lab Chip 5 1132-1139 Cheng RP, Gellman SH, DeGrado WF (2001) Beta-Peptides From Structure to Function. Chem Rev 101 3219-3232... 

Yube, K. and Furuta, M. and Mae, K. (2007). Selective oxidation of phenol with hydrogen peroxide using two types of catalytic microreactor, Catalysis Today, 125, 56-63. 

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