Catalytic performance of microtube-type copper-based catalyst for methanol steam reforming, prepared on the inner wall of an aluminum tube by electroless plating

In order to construct a high-performance microreactor for conducting heterogeneous catalytic reactions, one must prepare a porous catalytic wall with high surface area on the microchannel. In this study, with the purpose of preparing such a catalyzed wall, microchannels plated with copper-based components by electroless plating were prepared on the inner walls of aluminum tubes with micron-order diameter. The electroless plating consisted of an activation of the inner walls of aluminum tubes by hydrogen chloride solution, a displacement plating of zinc, an intermediate plating of iron, and chemical reduction plating of copper. Each process solution was flowed into the aluminum tube by a suction pump system. The physicochemical properties and the steam reforming properties of methanol for the plated channel were then investigated. Scanning electron microscopy (SEM) photographs of the surface and section of the plated wall showed that the preparation used in this study produced catalytic components with a film thickness of about 100 μm that were deposited porously on the inner surfaces of microtubes. An elemental analysis indicated that the plated walls consisted of copper and zinc, with the latter being detected in a wide area from the bulk to the surface of the wall. The microtube-type copper-based catalyst oxidized by air was significantly higher in activity of methanol reforming than that reduced by hydrogen, indicating that the conversion was 100% and the hydrogen production was about 0.07 mol/h at 160 °C with the channel length of 450 mm. Even after the activity of the oxidized catalyst declined, its initial activity could be restored by reoxidation. The activity restoration by reoxidation could be repeated. These results show that the microtube-type catalysts prepared in this study have high catalytic performance for microreformer.