Cross-flow micro reactor

Table 1.6 Characteristic quantities to be considered for micro-reactor dimensioning and layout. Steps 1, 2, and 3 correspond to the dimensioning of the channel diameter, channel length and channel walls, respectively. Symbols appearing in these expressions not previously defined are the effective axial diffusion coefficient D, the density thermal conductivity specific heat Cp and total cross-sectional area S, of the wall material, the total process gas mass flow m, and the reactant concentration Cg [114].

Reactor 5 [R 5] Cross-flow Multi-Plate Stack Micro Reactor... 

Figure 3.7 Alternated 90° turned adjacent platelets forming a stacked cross-flow configuration. Image of thermally bonded devices (top). Complete mounted multi-plate stack micro reactors (bottom) [45].

Reactor 24 [R 24] System with Series of Micro Mixers-Cross-Flow Reactor Modules... 

Reactor type System with series of micro mixers-cross-flow reactor moldules Number of reaction channels 169... 

To study the effects of molecular diffusion and formation/destabilization of reaction fronts it is advised to rely on small flow-through chambers such as capillaries or cells of sheet-type cross-section [68]. These micro reactors simply provide the small-scale environment needed for such laboratory investigations. 

Figure 3.26 Schematic of the high-throughput micro reactor with eight parallel flow passages, the micro compartments (right). Cross-section of the reactor showing details of the micro compartments (left). Dimensions are given in mm [55]...

Figure 3.29 (a) Oxygen concentration profile at the inlet and outlet of the compartments of the high-throughput micro reactor. The inlets of the sampling tubes have to penetrate into the compartments to minimize flow cross-over, (b) Area averaged oxygen concentration at one capillary outlet. Total flow velocity 50 (1), 75 (2) and 100 cm3 min-1 (3) [55] (by courtesy of ACS). 

These characteristics make the cross-flow microreactor a useful experimental tool for investigating kinetics and optimizing reaction conditions. Experiments regarding CO oxidation confirmed the ability of the micro-packed bed reactor to deliver valuable information about kinetics and mechanism, which compares well with data previously obtained in macroscale reactors. 

Multiphase packed-bed or trickle-bed microreactor [29, 30] Standard porous catalysts are incorporated in silicon-glass microfabricated reactors consisting of a microfluidic distribution manifold, a single micro-channel reactor or a microchannel array and a 25-pm microfllter. The fluid streams come into contact via a series of interleaved high aspect ratio inlet chaimels. Perpendicular to these chaimels, a 400-pm wide channel is used to deliver catalysts as a slurry to the reaction chaimel and contains two ports to allow cross-flow of the slurry. High maldistribution, pressure drop and large heat losses may occur... 

A micro-reactor is generally defined as a device consisting of a number of interconnecting micro-channels in which small quantities of reagents are manipulated, mixed and allowed to react for a specified period of time (Ehrfeld et al., 2000 Wirth, 2008). The movement of fluids within such a device can be achieved in a number of ways with the most common being mechanical micro-pumping and electro-osmotic flow, which may include electrophoresis separations. The typical cross-sectional dimensions of such micro-channels are in fhe range of 10-500 pm and are normally fabricated on the planer surface of substrates... 

Integrated reactors One type of integrated reactor is micro structured heat exchanger/reactor concepts, which may work as cross- or counter-flow reactors. Another type couples endothermic and exothermic reactions in two separate flow paths normally operated in the co-current mode. Both reactor types are designed as prototype components of future fuel processors for mobile applications. 

The concept presented here in much detail as an example of cooperative project work in micro structured reactor plant development is based on the bus system and simultaneously handles a number of tasks such as mechanical stability, fluidic flow and signal transmission. A key feature of the so-called backbone interface is its open architecture. It does not rely on standardized reactors or devices, thus allowing the combination of devices from various suppliers. A robust interface was developed which withstands high pressures and temperatures. Thermal cross-talk was minimized through the use of different heat-conducting materials. 

An important advantage of the use of EOF to pump liquids in a micro-channel network is that the velocity over the microchannel cross section is constant, in contrast to pressure-driven (Poisseuille) flow, which exhibits a parabolic velocity profile. EOF-based microreactors therefore are nearly ideal plug-flow reactors, with corresponding narrow residence time distribution, which improves reaction selectivity. 

---