30-channel microstructured reactor

Figure 5.27 A 30-channel microstructured reactor for the direct fluorination of ethyl 3-oxobutanoate (by courtesy of the Royal Society of Chemistry) [60].

Following extensive laboratory studies at the University of Durham, UK, on the direct fluorination of ethyl 3-oxobutanoate in formic add, scale-out was made from a three- to a nine-channel microstructured reactor, in cooperation with Asahi Glass Co. in Yokohama, Japan [60],... 

The process was performed for many months yielding 700 g of monofluorinated product with a nine-channel microstructured reactor [60]. A continuous 150 h operation was performed without decline of yield or conversion. Even in the scale-out to a 30-channel reador (see Figure 5.27), no loss in performance was noticed. A single feed system distributed the reactants and reagents to the various microchannels. 

V. Hessel, C. Ziegler, Parallel screening of Cu/Ce02/y-Al203 for steam reforming of methanol in a 10-channel microstructured reactor, Catal. Commun. 2004, 5, 671-675. 

Another pilot microstructured reactor uses a smart scale-up of the reactor plate dimensions by a factor of 3.3, each for the width and channel length (see Fig. 13). Stacking further plates is here one concept for future production reactors with another tenfold increase in structured area. 

Figure 11.17 Fluid reactant distribution in a microstructured reactor by a binary tree channel network. (From Berg, S.H. and Guan, S., W000/51720 to Symyx Technologies, Inc., March 1999.)...

Investigations on Taylor flow in noncircular channels originated from flows in porous materials, for instance, in enhanced oil recovery. They are also relevant to microstructured reactors and to the many monolithic systems which in many cases have noncircular reaction channels. 

The approach can also be used for multichannel reactors. Because of the small volume of a single channel, many channels have to be used in parallel to obtain sufficient reactor throughput. A uniform distribution of the reaction mixture over thousands of microchannels is necessary to obtain an adequate performance ofthe microstructured reactor. Flow maldistribution will enlarge the RTD in the multitubular reactor and lead to a reduced reactor performance along with reduced product yield and selectivity. Therefore, several authors have presented design studies of flow distribution manifolds [9-13]. 

The comparion of pressure drop in three different types of microstructured reactors, foam reactor, square channels and packed bed, is shown in Example 6.2. 

The same SSA is imposed for the two other microstructured reactors. The volume of the microchannel corresponds to the volume occupied by the fluid. Therefore, a = a = with dy as the hydraulic diameter of the channel. In consequence, channels with a hydraulic diameter of dy = 720 pm have the required SSA of 5556 m m . ... 

Mass Transfer in Catalytic Microstructured Reactors 247 Table 6.3 Mass transfer characteristics for different channel geometries [53],... 

The main problem for controlling the flow pattern is its dependence on many experimental parameters such as flow velocity, flow ratio of phases, fluid properties, channel geometry, microchannel material, wall roughness, pressure, and temperature. All these parameters influence the relative importance of the different forces. Different flow regimes in gas-liquid flows in microstructured reactors are discussed in the following section. 

In a vertically placed 20 parallel channel microstructured falling film reactor of 60 mm length, 1 mm width, and 0.3 mm depth, gas and liquid flows with 46 ml min and 3.6 ml min , respectively, estimate (1) thickness ofthe wall film, (2) mean velocity of liquid film, (3) Fourier number, (4) Reynolds number, and (5) mass transfer coefficient, k. ... 

Heat transfer is promoted by thin walls between the reaction channels and the heating or cooling channels, which leads to an improved energy efficiency [17], excellent temperature control [18] often enables higher selectivity and catalyst lifetime [19], Another promising feature of microstructured reactors is their modularity, which facilitates the scale-up and the adaptation of the plant to the changing process needs. 

Microstructured reactors have high potential for the controlled combustion of all types of fuels, even for hydrogen at high temperatures due to the flame arresting features of small channel systems (see also Section 5.3). 

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