Mixing tee

As a second example, several Hantzsch syntheses using diverse ring-substituted 2-bromoacetophenones and 1-substituted-2-thioureas are given. For these reactions, comparative and better yields were achieved when using a micro-mixing tee chip reactor as compared with conventional laboratory batch technology. The increase in yield amounted to about 10-20% [156, 157]. 

Figure 2.39 Schematic design of a mixing tee (above) and CFD results for mixing of gases in a channel of500 jm width and 300 jm depth, taken from [134] (below).

Reactor 4 [R 4] Chip Reactor with Micro-channel Mixing Tee(s)... 

Version (a) comprises one mixing tee only (Figure 4.4) [11]. Version (a2) can be heated up to 70 °C [9]. A T-shaped Peltier heater attached to the lower plate was used to adjust temperature. 

Figure 4.4 Mounted chip reactor with (right) and single micro-channel mixing tee chip (left) [8],...

Reactor type Chip micro reactor with one micro-channel mixing tee Channel width depth 200 pm (at top) x 100 pm... 

Version (b) has a four-channel flow guidance that encompasses two mixing tees in two simple mixing tees (Figure 4.5) [8]. An example of this function is the flow guidance for the Michael addition. In a first step, the base and 1,3-dicarbonyl compound streams merge. The enolate stream thus formed is then mixed with the Michael acceptor. Microporous silica frits are set into the channels to minimize... 

Figure 4.5 Schematic of the chip reactor with two micro-channel mixing tees.

In version (c), three mixing tees were realized in another version of the above-mentioned chip reactor concept [16]. 

Reactor 6 [R 6] Chip Micro Reactor with Multiple Micro Channel-Mixing Tees... 

Mixing tee channel diameters in connector 150 pm 500 pm 800 pm for all (three) channels Tube length (stainless steel) Not reported... 

A chip-type micro reactor array comprises parallel mixer units composed of inverse mixing tees, each followed by a micro channel that it is surrounded by heat exchange micro channels (so called channel-by-channel approach similar to the tube-in-tube concept). Such an integrated device was developed as a stack of microstructured plates made of a special glass, termed Foturan (Figure 4.26). The integrated device was attached to PTFE tubes of various lengths. 

Figure 4.39 Comparison of benzal chloride hydrolysis performed in a slit-shaped micro mixer and in a mixing tee [46],...

OS 1] [R 20] [P 1] A comparison of the selectivity/conversion behavior of an interdigital micro mixer-tube reactor with that of a mixing tee of about 1.5 mm inner diameter (and thus of larger internal dimensions) was made (Figure 4.39). For all data gathered, the performance of the micro mixer was much better, e.g. about 30% more selectivity at a given conversion [46]. 

P 33] The catalyst bed was manually positioned in the micro channel (300 pm wide 115 pm deep) at room temperature using a 10% (v/v) solution offormamide and potassium silicate [6, 7]. Micro reactor bottom and top plates were thermally bonded thereafter. Then, 75% THF (aqueous) solutions of 4-bromobenzonitrile and phenylboronic acid having equimolar concentrations were placed in the two reservoirs of a micro-mixing tee chip. In the collection reservoir, 30 pi of the THF solution was placed. Voltages ranging from 100 to 400 V were used, but kept constant only for one reservoir. The other one was switched on and off at 200 V for given time periods. 

Figure 4.70 Flow configuration for the Michael addition using 2,4-pentanedione and ethyl propiolate in a two-mixing tee microreactor [8].

OS 52[ [OS 53[ [OS 54[ [OS 55[ [R 4b[ [P 38[ In a two-micro-mixing tee chip reactor, substrates with diketone moieties of known different reactivity, such as 2,4-pentanedione, benzoylacetone and diethyl malonate, were processed, each with the same acceptor ethyl propiolate [8]. Also, a reaction with the less alkynic Michael acceptor methyl vinyl ketone was carried out. 

The Hantzsch synthesis was primarily chosen to evaluate the potential of a micro-mixing-tee chip reactor for carrying out reactions above room temperature (e.g. 

Table4.9 Benchmarking of mixing-tee chip micro-reactor operation to macro batch-scaie synthesis for a series of 2-aminothiazoies [10],...

P 54] A 50 gl volume of a 0.3 M solution of cyclohexanone in anhydrous methanol with about 1 mg of DCC is placed in one reservoir of a micro-mixing tee chip reactor [11] 50 gl of a 0.3 M solution of pyrrolidine is added to the other reservoir and anhydrous methanol is filled in the third, the collection reservoir. Voltages ranging from 300 to 1000 V are applied for a period of 40 min to transport the reaction species. The reaction is carried out at room temperature. 

Figure 4.85 Flow configuration for the aldol reaction of silyl enol ethers in a mixing-tee chip micro reactor [15],...

Figure 4.89 Comparison between yields obtained by one mixing tee micro reactor and batch operation using five different aldehydes at 2 1 stoichiometry [13. ...

Mass transfer efficiency by conversion analysis - benchmarking to mixing tee... 

GL 22] [R 3] [R 9] [R 10] [P 23] The mass transfer efficiency of different gas/liquid contactors as a function of residence time was compared qualitatively (Figure 5.29), including an interdigital micro mixer, a caterpillar mini mixer, a mixing tee and three micro bubble columns using micro channels of varying diameter [5]. 

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],...

All other devices showed only the increasing part of such a dependence, i.e. the highest performance measured was obtained at the longest residence time [5], The best conversions with the interdigital micro and caterpillar mini mixers (-78 and -70%, respectively) still exceed considerably the performance of a conventional mixing tee (1 mm inner diameter). 

P 21] Solutions of 10 M 4-(l-pyrenyl)butyric acid in ethanol and 10 M sulfuric acid in ethanol were contacted in a micro-mixing tee/micro channel flow configuration at room temperature and at 50 °C [91]. Pressure-driven feed was used. The glass surface of the micro channels was either tuned hydrophobic (by exposure to octadecyltrichlorosilane) or hydrophilic (by wetting with a sulfuric acid/hydrogen peroxide mixture). 

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