Fabrication of microreactors for dehydrogenation of cyclohexane to benzene

Novel microreactors have been fabricated on silicon in order to dehydrogenate cyclohexane to benzene. There are 12 reactor chips on one single silicon wafer. The microreactor consists of three chips, which are reaction chamber, separation membrane and reactor cap. The whole dimension of the reactor is 20 mm long, 14 mm wide and 3 mm high. As for reaction chamber, 80 microchannels 50 mum wide, 400 mum deep and 8 mm long have been etched. We use silicon (110) wafers to obtain high-aspect-ratio microstructures. Twenty nanometer Ti is sputtered and oxidized as the adhesion layer and catalyst carrier. Twenty nanometer Pt is sputtered as the catalyst. For the separation membrane, it is 6 mm by 8 mm, with 80 folded rectangular 4 mum thick Pd foil structures 50 mum wide, 200 mum high and 6 mm long anchored on silicon. This utilizes the combination of silicon (110) wet etching and dry etching together. These folded Pd microstructures contribute to increase the separation area of hydrogen. The reactor cap for inlet and outlet gas pipes is made of PDMS, which is a kind of relatively new material for MEMS applications. Finally, the reaction chamber, separation membrane and reactor cap have been bonded using Polyimide with very good contact strength between chips. The microreactors have been tested using a GC with a conversion value of 18.4%. (C) 2000 Elsevier Science B.V. All rights reserved.