Multi-channel reactor

Figure 5.13 SEM images of the microstructured catalyst support in the multi-channel reactor version. Overall view (channel view) (A) and detailed view of one column (B) [12],...

In order to carry out the reaction in higher temperatures and initial concentrations under controllable conditions, the continuously operated multi-channel reactor is taken into consideration. The continuous process contains a mixing step and a reaction step. Acetic acid and hydrogen peroxide are heated in heat exchangers and mixed in the mixing step. The equilibrium reaction takes place in the parallel reactor system. The scheme of the continuous process is depicted in Figure 4. 

Fait, M., Schneider, M., Kontratenko, E., etal. (2009). Combination of a Multi-Channel Reactor System with UV/vis Spectroscopy or XRD Proof of Principle, Third International Congress on Operando Spectroscopy, 19-23 April 2009, Rostock-Warnemiinde, Germany. 

Figure 8.10 Experimental compact reformer reactors 2, proof-of-concept Advantica natural gas reformer, a diffusion-bonded multi-channel reactor block (3 x 3 x 10 cm). (Reproduced by kind permission of Advantica Technologies Ltd.)...

Frequently, in evaluating catalyst performance emphasis is put on the selectivity of a desired product and not only on activity. In such cases account should be taken of the fact that selectivity depends on the degree of conversion of the key feed molecules. Under certain circumstances, e.g. selective oxidation of hydrocarbons, the flow conditions can be adjusted in such a way that the degree of oxygen conversion is 1 thus, the selectivity of all the catalysts can be compared. Otherwise it may be advisable to vary the total flow-rate to the multi-channel reactor in this way, selectivity can be obtained as a function of the degree of conversion. Comparable selectivity data for the different catalysts can be... 

Fig. 2 shows a schematic diagram of a micro-channel of reformer section to be examined in this study. A multi-physics computer-aided numerical model framework integrating kinetics, mass transport, and flow dynamics in micro-channel reactors has been established. 

The numbering-up concept demands achieving absolutely uniform flow equi-partition by placing special headers in front of the parallel micro channels [5]. Although this has been solved for tubes in conventional multi-tubular reactors, the expenditure for equipartition in micro channel stacks is assumed to be higher, since the small channels may have more relative differences in structural preci-... 

Reactor 1 [R 1] Reactor Module with Different Multi-channel Micro Reactors... 

This simple reactor concept is based on a microstructured silicon chip (Figure 3.18) covered by a Pyrex-glass plate by anodic bonding [73, 74]. The silicon microstructure comprises, in addition to inlet and outlet structures, a multi-channel array. Only the Pyrex-glass plate acts as cover and inlet and outlet streams interface the silicon chip from the rear. 

Reactor type Multi-channel chip reactor Pt film thickness 10-40 nm... 

Investigations with the modular multi-channel [28,98] and silicon chip [19, 56-62] micro reactors demonstrate that by exact temperature control the oxidation of ammonia can be run with increased and deliberately steered selectivity. A major application is provided by carrying out former high-temperature reactions in the low-temperature regime. In the case of ammonia oxidation in the chip micro reactor, the yield of the value product NO was actually lower in that regime. In the case of the multi-plate-stack micro reactor, higher yields of the value product NO2 were achieved. 

For a short description of the aims of experimental concentration cycling with respect to citraconic acid formation, see [13]. It is also demonstrated there that the response to rectangular concentration pulses for a given reactor configuration of a multi-channel-stack micro reactor can be improved by increasing the number of platelets and channels (while reducing their diameter). Such behavior was shovm for an incompressible fluid, i.e. is not solely related to the above-mentioned reaction. 

Reactor 28 [R28] Multi-channel Integrated Mixer-Heat Exchanger... 

Reactor type Multi-channel integrated mixer-heat exchanger Hydraulic diameter of cooling channel 900 pm... 

In the multi-channel version comprising 10 packed-bed reactors (Figure 5.14), the gas flow is distributed by star-type manifolds to the 10 reaction units [11,12],... 

Figure 4.97 Calculated cumulative residence time distribution function for a multi-channel well, a laminar flow reactor and a plug flow reactor [147] (by courtesy of VDI-Verlag GmbH).

The improvement in accuracy achieved by the complex closures compared to the simpler ones can also be questionable. Osenbroch ]67] and Mortensen ]60] successfully applied the combined particle image velocimetry (PIV)/planar laser induced fluorescence (PLIF) technique to measure the instantaneous velocity and reacting species concentration in mixing devices like a mixing channel, pipe, and multi-functional channel reactor. The measured... 

Compared to an equally distributed multi-injection reactor with Af = 4 a 20% reduced temperature rise at the first injection point is obtained. Especially in cases with high F, this kind of channel design can be beneficial (see Example 5.7). 

In order to work safely with multi-injection reactor, an accumulation of the limiting reactant and of heat in the main channel has to be thoroughly prevented. As the considered reactions are mostly Umited by mixing, the time required to mix can be estimated by using the correlation between specific energy dissipation and mixing time. Sufficient residence time should be provided between two injection points to minimize the hot spot. 

Product yield as a function of residence time for a fixed-bed reactor (triangles), a multi-channel microreactor (circles) and a multi-channel membrane microreactor (squares) (Lai etal., 2003) (Copyright permission 2006 Royal Society of Chemistry). 

Regular flow patterns are provided by the segmented flow in a single capillary or in multi-channel microreactors. Miniaturized packed-bed microreactors follow the paths of classical engineering by enabling tridde-bed or packed bubble column operation. M ost of the microstructured multiphase reactors are at the research stage. Due to the small reaction volumes th will find their appHcation mainly in small-scale production in the fine chemical and pharmaceutical industries. 

DifTerent types of microreactors, ranging from single-channel to multi-channel designs, and even more complex falling film reactors, have been investigated for carrying out photochemical reactions. Reported channel dimensions of photomicroreactors range from 10 to 1000 pm. 

Both reactor types R3 and R4 use the segmented flow (Taylor) principle. They are divided into two categories R3 has very small channels (<1 mm) and R4 are monolith reactors (honeycomb), well developed on the laboratory scale with at least one example of industrial application. Category R3 includes single-channel and multi-ple-channel reactors [10], etched in silicon [10] or glass [10,11], with wall-coated or immobilized catalysts in the case of gas-liquid-solid additions [12], and capillary microreactors for gas-liquid-liquid systems [13]. 

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