Reactor 3 Micro Bubble Column

LIGA-dispersion unit atiaotied to reactior and cooling charnels 

Reactor type Micro bubble column Mini heat exchange channel width depth length 3000 pm 500 pm 40 mm 

Housing, heat exchange and reaction plate material Steel Pressure stability 30 bar 

Micro mixer plate material Nickel Temperature stability Up to 180 °C 

Outer dimensions (without connectors) 95 X 50 X 36 mm Residence time 0.14-0.56 s (at 10 ml h liquid flow 600-3300 ml h gas flow) 

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For toluene fluorination, the impact of micro-reactor processing on the ratio of ortho-, meta- and para-isomers for monofluorinated toluene could be deduced and explained by a change in the type of reaction mechanism. The ortho-, meta- and para-isomer ratio was 5 1 3 for fluorination in a falling film micro reactor and a micro bubble column at a temperature of-16 °C [164,167]. This ratio is in accordance with an electrophilic substitution pathway. In contrast, radical mechanisms are strongly favored for conventional laboratory-scale processing, resulting in much more meta-substitution accompanied by imcontroUed multi-fluorination, addition and polymerization reactions. 

Figure 5.17 Comparison of performance of a typical laboratory column (LBC) with those of micro-reactor devices falling film micro reactor (FFMR) micro bubble column (MBC I and MBC II) [38].

The laboratory and the micro bubble column show decreasing selectivity with increasing conversion. The falling film micro reactor shows a near-constant selectivity-conversion relationship [3, 38]. 

GL 1] [R 1] [R 3] [P le] The falling film micro reactor has a better selectivity-conversion performance than the two micro bubble columns tested (Figure 5.18) (3, 38]. The micro bubble column with narrow channels has a better behavior at large conversion than the version with wide channels. The behavior of the falling film micro reactor and the micro bubble column with narrow channels is characterized by a nearly constant selectivity with increasing conversion, while the bubble column with wide channels shows notably decreasing selectivity with conversion (similar to the laboratory bubble column). 

GL 1] [R 1] [R 3] [P la-d] Space-time yields higher by order of magnitude were found for the falling film micro reactor and the micro bubble column as compared with the laboratory bubble column [38], The space-time yields for the micro reactors ranged from about 20 000 to 110 000 mol monofluorinated product m h. The ratio with regard to this quantity between the falling film micro reactor and the micro bubble column was about 2. The performance of the laboratory bubble column was of the order of 40-60 mol monofluorinated product m" h. ... 

Figure 5.19 Conversion of the direct fluorination of toluene in different reactor types as a function of the molar ratio of fluorine to toluene (a) and efficiency of these reactors, defined as conversion normalized by the molar ratio of fluorine to toluene, as a function of the molar ratio of fluorine to toluene (b). Falling film micro reactor (FFMR) micro bubble column (MBC) laboratory bubble column (LBC) [38].

Figure 5.29 Special-type multi-purpose micro devices and mixing tee used for investigation of CO2 absorption. Comparison of their reactor performance as a function of the residence time. Micro bubble columns ( ) 1100 pm x 170 pm, (A) 300 pm x 100 pm and (T) 50 pm x 50 pm Interdigital mixer ( ) (40 pm) caterpillar mixer (A) (850 pm ramp) mixing tee (0) (1 mm) [5],...

Reactor model of micro bubble column performance... 

GL 26] [R 3] [P 28] See the discussion of results in the section Reactor model of micro bubble column performance, above [10]. 

Microstructured falling film and micro bubble column reactor Single micro channel operating in annular flow regime Microstructured falling film reactor Microstructured falling film reactor... 

Figure 7.23 Schematic presentation of (a) microstructured falling film reactor and (b) micro bubble column (b) [75]. (Adapted with permission from Elsevier.)...

Aspect Micro slurry reactor Jet loop reactor Stirred slurry reactor Slurry bubble column reactor Three-phase fluidized reactor Packed bubble column reactor Trickle bed reactor... 

Similar to the numbered up Taylor-flow reactor, the micro bubble column achieved dispersion by an interdigital mixing element with many miniaturized mixing tees (Figures 9.17 and 9.18) [4,26,66,67,71,74,75]. This was one of the very... 

The mass transfer efficiency of the falling film microreactor and the micro bubble column was compared quantitatively to literature reports on conventional packed columns (see Table 9.5) [141]. The process conditions were chosen as similar as possible for the different devices. The conversion of the packed columns was 87-93% the microdevices had conversions of 45-100%. Furthermore, the space-time yield was compared. Here, the microdevices resulted in larger values by orders of magnitude. The best results for falling film microreactors and the microbubble columns were 84 and 816 mol/(m s), respectively, and are higher than for conventional packed bed reactors of about 0.8 mol/(m s). 

Dream reactions can be performed using chemical micro process engineering, e.g., via direct routes from hazardous elements [18]. The direct fluorination starting from elemental fluorine was performed both on aromatics and aliphatics, avoiding the circuitous Anthraquinone process. While the direct fluorination needs hours in a laboratory bubble column, it is completed within seconds or even milliseconds when using a miniature bubble column. Conversions with the volatile and explosive diazomethane, commonly used for methylation, have been conducted safely as well with micro-reactors in a continuous mode. 

GL 1] [R 1] [R 3] [P le] The performance of a typical laboratory bubble column was tested and benchmarked against the micro reactors (Figure 5.17). Using acetonitrile as solvent, the conversion of the laboratory bubble column ranged from 6 to 34% at selectivities of 17-50% [3, 38]. This corresponds to yields of 2-8%. Hence the yields of the laboratory tool are lower than those of the micro reactors, mainly as a consequence of lower selectivities. 

The above-mentioned space-time yields were referred solely to the reaction volume, i.e. the micro channel volume. When defining this quantity via an idealized reactor geometry, taking into accoimt the construction material as well, natarally the difference in space-time yield of the micro reactors from the laboratory bubble column becomes smaller. Still, the performance of the micro reactors is more than one order of magnitude better [38], The space-time yields for the micro reactors defined in this way ranged from about 200 to 1100 mol monofluorinated product... 

GL 1] [R 1] [R 3] [P la-d] For micro-channel processing, an analysis of the content of fluorine actually consumed as a function of the fluorine-to-toluene ratio was made [38]. The curves for two micro reactors and one laboratory bubble column do not show the same trend a decrease of converted fluorine with increasing ratio results for the falling-film micro reactor, whereas the micro and laboratory bubble columns show increasing performance. The two micro reactors use about 50-75% of all fluorine offered, whereas the laboratory tool has an efficiency of only 15%. 

Classical heterogeneous catalytic reactor types used in various process technologies include packed beds, wall-catalyzed reactors, bubble columns, stirred tanks, risers, and fluidized beds. Monoliths and micro reactors have also made inroads in the last couple of decades. Novel designs attempt to... 

Reaction Studies. The reaction system consisted of a flow micro-reactor using helium as a carrier gas bubbled through a saturator containing 2-propanol. The partial pressure of 2-propanol was adjusted by controlling the temperature of the saturator. Approximately 200-400 mg of the layered hydroxide were heated In the reactor under a flow of helium In order dehydrate and dehydroxylate the material. The partial pressure of 2-propanol was maintained at 100 torr and the helium flow was varied between 10-20 ml/min. The in-situ calcination temperature was varied between 400-500°C and the reaction temperature between 150-350°C. Analyses of the reactants and the products were performed by an on-line GC fitted with a capillary column. 

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