Development of a self-heating catalytic microreactor

Microchannels were fabricated on the both sides of a (100) silicon wafer by wet chemical etching, after pattern transfer using a negative photoresist. The channel (upper width = 600 mum, lower width = 515 mum, depth = 60 mum, and length = 78 mm) on one side was used as a reactor. A heating element (Pt wire) was installed in the channel on the opposite surface of the reactor channel, and a thermocouple was installed in a channel adjacent to the reactor. A thin platinum layer was coated as a catalyst on the walls of the reactor channel by sputtering. In order to increase the surface of the catalyst, a gamma-alumina support layer was formed in the reactor channel by a sol-gel process. The reactor channel, as well as the heating channel on the reverse side, was then sealed so as to be gas-tight with glass plates by an anodic bonding technique. A solution of H2PtCl6 was introduced into the reactor channel with the gamma-alumina layer, and platinum was loaded on the support. Both platinum catalysts, prepared by sputtering and impregnation techniques, were activated in a flow of hydrogen at 773 K. The self-heating microreactor was then used for the hydrogenation of benzene as a model reaction. The reaction rate of the supported catalyst was one order of magnitude higher than that of the sputtered catalyst.