Secondary Screening 48-Channel Fixed-bed Reactor

Secondary screening is carried out in parallel fixed-bed reactors sized for catalyst loadings between 15 and 500 mg. The system is a 48-channel reactor consisting of six modules of eight reactor wells. Six channels are analyzed in parallel and stream selection valves provide fluidic multiplexing between reactor vials and analytical hardware. A typical system is shown in Fig. 3.11. 

Reactant feeds are generated by vaporizing liquid flows from HPLC pumps with manometric pulse dampeners or high-pressure syringe pumps and mixing this vapor with gas components metered through mass flow controllers. This reaction feed is then divided between the 48 channels equally by using flow restrictors such as silica capillaries or micromachined channels (Fig. 3.12). The capillaries feed into the inlet stand-offs of the reactor modules. 

The reactor wells are pre-loaded with catalyst (diluted with silicon carbide if desired) and inserted into the module. Two graphite seals are used per well, one to pressure seal each vial and one to prevent bypass flow around the vial. A single central bolt in tension supplies the sealing force onto these seals (Fig. 3.12b). 

Each of the eight reaction product streams leaving the reactor module are fed into a Valeo stream selection valve where one of the eight effluents is selected and sent to a GC for on-line analysis. The remaining channels, combined, are sent through a back pressure controller to a waste. The selected channel from each 

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