Experimental and theoretical investigation of H2 oxidation in a high-temperature catalytic microreactor

A sample and flexible quartz-glass-based microreactor design is presented for high-temperature catalytic gas-phase reactions. The reactor was tested with the platinum-catalysed hydrogen oxidation reaction, withstanding extremely high reaction temperatures in excess of 1000 degreesC without ally signs of degradation. Experimental results are compared to those from a previous, alternative microreactor configuration, indicating substantially reduced heat losses. No homogeneous flames or explosions are observed under any reaction conditions, indicating that homogeneous reactions can be very effectively suppressed in a microreaction channel. A theoretical analysis of the explosion limits in the homogeneous H-2/O-2-system confirms that reactors with characteristic dimensions in the sub-millimetre range become intrinsically safe at ambient pressure conditions. Furthermore, the analysis shows that the suppression of the explosive reaction behaviour in these microreactors can be traced to a kinetic quenching of the radical chain mechanism rather than a thermal quenching due to increased heat transfer rates. (C) 2001 Elsevier Science Ltd. All rights reserved.