Catalytic microstructured reactors microreactors

Integration of various components is an important issue for the DCF systems. The simple scale-up of microreactors is not enough as the DCF system. A DCF system should consist of not only reactors but also other factory parts like a mixer, separator, and temperature controller. Many integrated microreaction systems have been reported and some of these are commercially available. For example, K. F. Jensen s group has reported an integrated microreactor system for gas-phase catalytic reactions using microstructured reactors and other devices on a computer board [13]. They have achieved computer control over the reaction system through this device as shown in Fig. 6. 

Of course, not all multiphase microstructured reactors are presented in Table 9.1. Either because they have attracted (too ) little interest, because they may have been qualified as microreactors in spite of their overall size but caimot be considered as microstmctured , or because they combine several contacting principles. Examples are a reactor developed by Jensen s group featuring a chaimel equipped with posts or pillars, thus resembling more a packed bed but with a wall-coated layer of catalyst [20], and a string catalytic reactor proposed by Kiwi-Minsker and Renken [21], that may applied to multiphase reactions. 

DSO via molybdate-catalyzed disproportionation of HjOj provides a readily scalable alternative to photooxidation. It can be carried out in commonly available stirred-tank reactors. However, the reaction does not work at low temperatures and organic media are limitedto alcoholic polar solvents (methanol or the safer ethylene glycol) or to microstructured media such as one-, two-, or three-phase microemulsion systems. The latter based on balanced catalytic surfactants advantageously combine low surfactant concentration with easy product isolation and catalyst recycling via simple phase separation. Safe processing may be further enhanced by microreactors, which minimize peroxide hold-up. 

The small dimensions in microreactors imply the presence of laminar flow. This type of flow makes it easier to extract chemical kinetic parameters and fully characterize phenomena. The correct incorporation of the active catalyst onto the surface of the membrane is one of the important aspects of catalytic microreactors. Drott et al. (1997) investigated the use of porous silicon as a carrier matrix in microstructured enzyme reactors. The matrix was created by anodization and the fabrication of the microreactor used flow-through silicon cell comprising 32 channels of 50 pm wide, 250 pm deep and separated by 50 pm. The aim was to increase the surface area on which the enzymes (glucose oxidase) could be coupled. Comparisons were made with the classical non-porous reference device and the glucose turnover rates. The results showed that when compared with the reference reactor the enzyme activity increased 100-fold. 

Delsman et al. investigated the advantages of a microstructured methanol reformer coupled with a catalytic burner for anode off-gas over a conventional fixed-bed system [36]. Two ranges of electrical power output of the corresponding fuel processor-fuel cell system were considered, namely 100 W and 5kW. The calculations revealed a more than 50% lower reactor size and more than 30% less catalyst mass required for the microreactor in case of the 100 W system. For the 5 kW system, the reactor volume was only 30% lower, but the catalyst savings were up to 50%. 

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