Plate heat exchangers and microstructured reactors

In order to meet the requirements of a 20 kW fuel processor, which vreis the final target of their work, Dudfield et al. [161] scaled their reactors up to a dual stage design of 41 total volume. Each reactor was 108 mm high, 108 mm wide, and 171 mm long had a volume of 1.851 and 2.5 kg weight and carried 8.5 g catalyst The air feed was split in a ratio of 2/1 between the first and second reactor. When the reactors were operated at a temperature of 160°C and a feed flow rate of2001/min, the carbon monoxide content could be decreased from 2.0 vol.% to values below 15 ppm at an OICO ratio of 5.0 [162]. The reactors were operated at full load (20 kW equivalent power output) for approximately 100 h without apparent deactivation [161]. 

A silicon microreactor for preferential oxidation was designed by Srinivas et al. [163], which was 6 cm x 6 cm wide and long, while the flow path was only 400 pm high. Instead of microchannels, pillars were chosen for the flow distribution in the reactor. The reactor was coated with 2 wt.% platinum/alumina catalyst with a thickness of 10 pm. Tests were performed at an O/CO ratio of 2.0 and a high VHSV of 120 l/(h gcat)- Not more than 90% conversion of carbon monoxide could be achieved in the reactor at 210°C reaction temperature, while similar results were obtained for a small fixed catalyst bed. 

Ouyang et al. [147] studied the preferential oxidation of carbon monoxide in silicon reactors of the smallest scale fabricated by photolithography and deep reactive ion etching. The reactors had two gas inlets for reformate and air, a premixer, a single reaction channel, and an outlet zone where the product flow was cooled. The chaimels were sealed by anodic bonding with a Pyrex glass plate. Full conversion of carbon monoxide was achieved between 170 and 300° C reaction temperature. 

A microstructured plate heat exchanger for preferential oxidation in the kilowatt size range was developed by Kolb et al. [139]. The reactor had three-stage cross-flow design for the sake of easier fabrication. Platinum catalyst supported by alumina 

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