Reactor alumina micro-channel

Aluminium substrates are frequently pre-treated by anodic oxidation to generate a porous surface, which may serve as the catalyst support itself or as an adhesion layer for a catalyst support [122]. The surface area of the obtained alumina layer may reach 25 m g , with a thickness of 70 pm or higher. Assembled alumina micro-channel reactors can also be oxidised. The layer generated by anodic oxidation of aluminium and aluminium alloys is amorphous hydrated alumina. It is believed to contain boehmite, pseudoboehmite and physically adsorbed water [123]. It has the morphology of a packed array of hexagonal cells, each containing a pore in the centre. Thus the layer has a highly ordered porous structure and uniform thickness, when an... 

GL 18] [R 6a] [P 17] A sol-gel deposited catalyst used in a fixed-bed reactor gave higher conversion than a micro-channel catalyst impregnated on a porous alumina layer [17]. This was due to the higher geometric surface area of the sol-gel deposited catalyst. 

The ceramic 64-channel reactor of Rodemerck et al. [28-30] bridges the gap between micro- and macroscopic fixed-bed reactors (Fig. 4.11). The catalyst containers consist of a massive tubular disc of alumina with borings for the catalyst powder clamped between two massive cordierite discs. This set-up can be operated up to 550 °C at pressures of up to 3 bar. 

Additionally, thin-film layers of the catalyst may be deposited on to the surface of the micro channels by sputtering [73] or CVD [63], In the latter case, aluminum isopropoxide, Al[(CH3)2CHO]3, was used as alumina precursor, which was passed through a ready-stacked reactor at 300 °C for 1 h in a flow containing nitrogen and oxygen in addition. The flow direction was subsequently changed and the procedure repeated. 

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