Continuous microreactor, characterization

Application of On-line Raman Spectroscopy to Characterize and Optimize a Continuous Microreactor... 

The syntheses of the ZSM-5 zeolites were based on two different patents (refs. 2-3). In two of the synthesis mixtures sodium ions were, however, largely replaced by potassium ions (table 1). Protonation was achieved by ion-exchange with an aqueous 1 M solution of ammonium-nitrate followed by calcination for 8 hours at 500 °C. In addition, one H-ZSM-5 catalyst was kindly supplied from MOBIL. The zeolites were characterized by x-ray diffraction, scanning electron microscopy, pore-volume measurements (BET) and elemental analysis (ICP). Catalytic experiments were performed at atmospheric pressure by feeding methanol diluted with nitrogen (1 5) into a continuous flow quartz microreactor containing 25-300 mg H-ZSM-5. The reaction temperature was varied from 245 to 400 °C and the products were analyzed by gas-chromatography. 

This section describes numerical and experimental means for the detailed characterization of multiphase flows. Flow behavior is closely linked to the transport processes of fluid mixing and axial dispersion and therefore affects the yield of chemical reactions performed in microchannel networks. Integrated multiphase flow sensors are potentially important for observing and controlling microreactor performance during continuous operation. 

Microreactors are characterized by small dimensions, an extremely large surface to volume ratio and, therefore, different reaction conditions compared to large scale reactors Using continuous flow microreactors, fast and highly selective reactions... 

The reports mentioned above provide a systematic coverage of the nonimmobi-lized enzymatic reactors used in biocatalytic reactions under continuous flow operation. Results from microreactor experiments were comparatively higher than conventionally mixed batch reactors in terms of conversion rate and improvement of product yield as demonstrated for hydrolysis [140], dehalogenation [141], oxidation [142], esteriflcation [143], synthesis of isoamyl acetate [144,145], synthesis of cyanohydrins [147,148], synthesis of chiral metabolites [153], reduction [151], and bioluminescent reaction [149]. The small volumes involved and the favorable mass transfer inherent to these devices make them particularly useful for the screening of biocatalysts and rapid characterization of bioconversion systems. The remarkable results of such studies revealed that the product yield could be enhanced significantly in comparison with the conventional batch runs. 

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