Monolith reactors

Electrochemical Promotion Using a Bipolar Monolithic Reactor... 

I., Mikkola, J.-P., and Salmi, T. (2004) The development of monolith reactors general strategy with a case study. Chem. Eng. Sci., 59, 5629-5635. 

Irandoust, S., Cybulski, A., and Moulijn, J.A. (1998) The use of monolithic reactors for three-phase reactions, in Structured Catalysts and Reactors,... 

Figure 13.2 Internally illuminated monolith reactor (IIMR) scheme with a detail of the cross section of the monolith channels and the fiber-optic bundle.

The low density of gases makes it more difficult to keep the bubbles dispersed. The bubbles will move to the low-pressure areas, that is, behind the impellers, in the trailing vortices close to the impeller, behind the baffles, and at the inner side after a bend. The bubbles will coalesce in these areas with high gas holdup. It is very difficult to design reactors without low-pressure regions where the low-density fluid will accumulate. One such reactor is the monolith reactor for multiphase flow [32, 33]. 

Kreutzer, M.T. et al. (2005) Multiphase monolith reactors chemical reaction engineering of segmented flow in microchannels. 7th International Conference on Gas-Liquid and Gas-Liquid-Solid, 2005,... 

Static mixing catalysts Operation Monolithic reactors Microreactors Heat exchange reactors Supersonic gas/liquid reactor Jet-impingement reactor Rotating packed-bed reactor... 

Describe the advantages and disadvantages of the following reactor types with reference to heat and mass transfer. For each reactor discuss one reaction for which it may be appropriate to use that reactor, (a) fluidized bed reactor, (b) A continuous counter-current flow reactor, (c) A monolith reactor. 

Concerning the reaction pathway, two routes have been proposed the sequence of total oxidation of methane, followed by reforming of the unconverted methane with CO2 and H2O (designated as indirect scheme), and the direct partial oxidation of methane to synthesis gas without the experience of CO2 and H2O as reaction intermediates. The results obtained by Schmidt and his co-workers [4, 5] indicate that the direct reaction scheme may be followed in a monolith reactor when an extremely short contact time is employed at temperatures in the neighborhood of 1000°C. However, the majority of previous studies over numerous types of catalysts show that the partial oxidation of methane follows the indirect reaction scheme, which is supported by the observation that a sharp temperature spike occurs near the entrance of the catalyst bed, and that essentially zero CO and H2 selectivity is obtained at low methane conversions (<25%) where oxygen is not fully consumed [2, 3]. A major problem encountered... 

The whole set-up for partial oxidation comprises a micro mixer for safe handling of explosive mixtures downstream (flame-arrestor effect), a micro heat exchanger for pre-heating reactant gases, the pressure vessel with the monolith reactor, a double-pipe heat exchanger for product gas cooling and a pneumatic pressure control valve to allow operation at elevated pressure [3]. 

Figure 3.49 Comparison of yields of a micro reactor and monolithic reactors, both operating in the same flow regime [2],...

Reactors with a packed bed of catalyst are identical to those for gas-liquid reactions filled with inert packing. Trickle-bed reactors are probably the most commonly used reactors with a fixed bed of catalyst. A draft-tube reactor (loop reactor) can contain a catalytic packing (see Fig. 5.4-9) inside the central tube. Stmctured catalysts similar to structural packings in distillation and absorption columns or in static mixers, which are characterized by a low pressure drop, can also be inserted into the draft tube. Recently, a monolithic reactor (Fig. 5.4-11) has been developed, which is an alternative to the trickle-bed reactor. The monolith catalyst has the shape of a block with straight narrow channels on the walls of which catalytic species are deposited. The already extremely low pressure drop by friction is compensated by gravity forces. Consequently, the pressure in the gas phase is constant over the whole height of the reactor. If needed, the gas can be recirculated internally without the necessity of using an external pump. 

Bubble column Loop reactor Packed column Plate column Monolithic reactor... 

If, from tran.sport-reaction considerations, a particle size smaller than 1 mm is chosen, slurry or monolith reactors will be considered. For larger particles, packed-bed reactors are more suitable. 

The trickle-bed reactor (TBR) and slurry reactor (SR) are the most commonly used for multiphase reactions in the chemical industries. A new reactor type, the monolithic reactor (MR), offers many advantages. Therefore, these three types of reactors are discussed below in more detail. Their general characteristics are given in Table 5.4-44. With respect to slurry reactors, the focus will be on mechanically agitated slurry reactors (MASR) because these are more widely used in fine chemicals manufacture than column slurry reactors. 

Figure 5.4.77. Monolith reactor with external liquid recycle.

Fig. 9. Reversed-phase separations of cytochrome c digests obtained with trypsin-modified beads (left) and trypsin-modified monolithic reactor (right) in a tandem with a chromatographic column (Reprinted with permission from [90]. Copyright 1996 Wiley-VCH). Conditions digestion (left curve) trypsin-modified beads reactor, 50 mm x 8 mm i.d., 0.2 mg of cytochrome c, digestion buffer, flow rate 0.2 ml/min, 25 °C, residence time, 15 min (right curve) trypsin immobilized onto molded monolith other conditions the same as with trypsin-modified beads. Reversed-phase chromatography column, Nova-Pak C18,150 mm x 3.9 mm i.d., mobile phase gradient 0-70% acetonitrile in 0.1% aqueous trifluoroacetic acid in 15 min, flow rate, 1 ml/min, injection volume 20 pi, UV detection at 254 nm...

---