Microreactor channel

In another glass (borosilicate) microreactor [channel dimensions = 350 pm (wide) x 52 pm (deep) x 2.5 cm (long)], Wiles et al. (2004b) prepared a series of 1,2-azoles, illustrating the synthesis of a pharmaceutically relevant core motif. Reactions were performed using electroosmo-tic flow (EOF) as the pumping mechanism and employed separate... 

Employing a staked plate microreactor (channel dimensions = 100 pm, total volume = 2 ml), Acke and Stevens (2007) reported the continuous flow synthesis of a series of chromenones via a multicomponent route consisting of a sequential Strecker reaction-intramolecular nucleophilic addition and tautomerization, as depicted in Scheme 2. 

Mukae et al. (2007) also compared a Pyrex batch reaction vessel (8 mm) with several Pyrex microreactors [channel dimensions = 100 pm (wide) x 40 pm (deep) 1.20 cm (long)] for the photocycloaddition of... 

In an analogous manner, Matsushita et al. (2006) investigated the use of a quartz microreactor [channel dimensions = 500 pm (wide) x 100 pm (deep) x 0.40 cm (long)], in which the bottom and sides of the microchan-nel were coated with Ti02 (anatase), for the photocatalytic reduction of 4-nitrotoluene 193 (Scheme 56a) and benzaldehyde 116 (Scheme 56b) using a UV-LED (A = 365nm). As the photoreduction of an analyte requires a corresponding oxidation step to occur, a series of alcohols were evaluated as potential reaction solvents. 

The inlet stream contains ammonia and oxygen with partial pressmes of 0.046 and 0,068 torr, respectively, and the flow rate is 100 1/h. Solve the problem for a temp-erature of (1) 473 K and (2) 673 K and compare the results. The microreactor channel is 40 x 300 p-m, and its length is 1 cm. The governing equations are... 

R. Pohorecki, P. Sobieszuk, K. Kula, W. Moniuk, M. Zielinski, P. Cyganski, P. Gawinski, Hydrodynamic regimes of gas-liquid flow in a microreactor channel, Chem. Eng. J. 135 (2008) S185. 

The electronics needed to operate six temperature sensors on each microreactor channel are located underneath these cards. The ribbon connector, which is also visible in Fig. 12.8, is used to transfer electrical signals directly from the reactor board to the heater circuit board (described below). Serial communications for the Redwood flow manifolds is provided by two, four-conductor RJ-11 jacks on the front. The front of the board has gas inlets for the reactor feed and the purge gas. In addition, there are two gas outlets, one for each reaction channel. The inlet and outlet fittings are 1/16-inch type 316L stainless steel. The tubing assembly component having the greatest pressure sensitivity is the microreactor membrane. 

The operation of the microreactors is monitored through the Microreactors tab on the main control panel. This panel displays the position of the SOVs, the feed gas flow rate to each microreactor channel, and whether or not the microreactor heaters are enabled. Additional information on the operation of each of the microreactor channels can be obtained by clicking on the Open Panel button next to the reactor name. In addition, pressing the Configure Reactor Control button opens a sub-panel where the operator can configure the temperature control mode for each of the microreactor channels to be either manual or automatic PID control. Some salient aspects of the reactor control panel are given below since this is the key system component. 

The various Reactor Control panels allow the operator to review much more detailed information on the operation of an individual microreactor channel. It also allows the operator to make changes to the process set points. Figure 12.15 shows the Reactor Control panel for channel A of the microreactor on Reactor Board 1. Here, the operator can choose the gas stream flowing to the microreactor (either feed gas or purge gas), specify the gas flow rate, and define the set points for the microreactor heaters. The Temperature Reading indicators at the top of the channel block in the middle of the panel show the measured temperatures of the first six microreactor heaters in the channel using the microreactor RTDs (as... 

At the end of an experiment, the microreactor channels were purged with N2 or He (depending on the purge gas connected to the system at the time) and additional GC injections of feed gas were taken. During a few runs, a microreactor failed through membrane rupture or the heaters becoming inactive. At this point. 

Fig. 12.20 O2 conversion data versus temperature for the oxidation of CH4 for three microreactor channels. Open-loop temperature control was used in this experiment with each heater set to the same heater voltage. The temperature used for the plot is the average of the measured RTD temperatures. These results come from one AIMS experiment with three...

Jensen and coworkers [25] demonstrated the photochemical synthesis of benzo-pinacol (Scheme 6.9) within a sUicon/quartz microreactor (channel dimensions 500 pm wide x 250 pm deep), which enabled UV light to pass through the quartz layer and irradiate the reaction mixture contained within the microchannel network. Employing on-line UV analysis, they were able to assess the reaction progress rapidly and with ease. Preliminary investigations conducted at flow rates of >10.0 pi min showed no benzopinacol formation. Only recovery of the unreacted starting materials benzophenone and 2-propanol was observed. By reducing the flow rate to... 

Mizuno and coworkers demonstrated an intramolecular version of [2 -I- 2] photo-cydoaddition using glass or poly(dimethoxysilane) (PDMS) microreactors (channel dimensions 100-300 pm wide, 40-50 pm deep) [27]. The reaction using a microreactor gave a better regioisomeric ratio than that with a batch reactor, since the possibility of the reverse reaction was reduced by a much shorter residence time, i.e. Imin, inside the microchannel (Scheme 6.11). 

Figure 4.3 Variation of the error induced in the measured rate constant ks under plug-flow assumptions as a function of the Damkohler number D, for various values of the radial Peclet number Pe and a microreactor channel length L= lOR. Reproduced from Commenge et al. [69].

Karagiannidis S, Mantzaras J, Boulouchos K Stability of hetero-Zhomogeneous combustion in propane and methane fueled catalytic microreactors channel confinement and molecular transport effects, Proc Combust Inst 33 3241—3249, 2011. 

One of the first reports was published by Lu and coworkers [46], who demonstrated the use of a glass microreactor [channel dimensions, 220 pm (wide) x 60 pm (deep) X 1.4cm (length)] for the rapid synthesis of a series of radiolabeled compounds (Scheme 6.14). A premixed solution of 3-pyridin-3-yl-propionic acid (41) (0.01 M) and tetra-n-butylammonium hydroxide (0.01 M in DMF) was introduced from one inlet of the reactor and a solution of premade radioactive tosylate (42) (0.01 M in DMF) was added from the other inlet. A residence time of 12 s afforded the respective labeled ester (43) (Scheme 6.14) with a radiochemical yield (RCY) of 10%. Although, in this first example, the yield was not significantly better than other techniques, the advantage was that the overall processing time was reduced to just 10 min, which is ideal for PET tracer synthesis. 

Figure 4.14 Coupling a microreactor channel with an analytical microdevice on one chip.

Figure 7.8 Microreactor channel design with droplet jet injector, (a) Channel schematic showing dimensions, (b) Optical micrograph of droplet injection cross, (c), (d) Cross-sectional view of the channel, (e) Side view of the channel. (Reproduced form Ref [99].)...

Several approaches have been reported for the reactions with solid catalysts [11]. Catalytically active metals may be used to cover the inner walls of a microchannel [12-14] or catalysts can be loaded on polymer beads in the microreactor channel [15]. These methods of catalyst deployment in the microchannel benefit from a high surface area-to-volume ratio. Otherwise, regeneration of the catalyst causes great... 

Sebastian, V., de la Iglesia, O., Mallada, R. et al. (2008) Preparation of zeolite films as catalytic coatings on microreactor channels. Microporous and Mesoporous Materials, 115,147-155. 

Zamaro, J.M. and Miro, E.E. (2009) Confined growth of thin mordenite films into microreactor channels. Catalysis Communications, 10,1574-1576. 

Stability of Hetero-ZHomogeneous Combustion in Propane- and Methane-Fueled Catalytic Microreactors Channel Confinement and Molecular Transport Effects... 

All channel elements had an emissivity Sj = e = 0.6, j = 1, N, while examples of the calculated factors Fk-j are presented in Fig. 8.2 for two channel wall elements and the inlet channel enclosure. The inlet and outlet planes of the enclosure had emissivities equal to those of the channel wall surfaces, jj,j = squt — — 0.6, while the inlet and outlet exchange temperatures were set equal to the inlet mixture and outlet mixing cup temperatures, respectively. This arrangement mimics the tight space in microreactor systems, wherein the entry and outlet sections cannot usually be of large enough size to allow for a black body enclosure treatment. The outer horizontal wall of the microreactor channel was treated as adiabatic (see Fig. 8.1) nevertheless, the reactor itself was non-adiabatic due to radiation heat losses, primarily from the channel wall inner surface as well as from the vertical front solid wall face towards the colder inlet enclosure. 

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