Steam Reforming of Ethanol Using Silica-Coated Alumite Catalysts on Aluminum Plates (JIS A1050)

Abstract

With the aim of developing a high performance reactor for proton exchange membrane fuel cell (PEMFC) systems and other applications, steam reforming of ethanol using silica-coated alumite catalysts on aluminum plates (JIS A1050) was performed at atmospheric pressure in a temperature range of 300–600°C. The aluminum material (JIS A1050) was used in a plate type aluminum-clad material which has been used for electrically heatable alumite catalysts having high heat durability. Initial ethanol steam reforming tests performed with either an alumite support (γ-Al2O3/Al) or an alumite catalyst (Ni/γ-Al2O3/Al) produced ethylene (C2H4) as the main byproduct because of the dehydration reaction of ethanol. With the aim of eliminating ethylene formation, a silica coating was applied to anodized aluminum plates (JIS A1050 Al) using a commercially available silica sol with a particle diameter of 22–25 nm. The resulting silica-coated alumite support (silica/Al2O3/Al) and silica-coated alumite catalyst (Ni/silica/Al2O3/Al) dramatically reduced the formation of ethylene. For example, in the case of the silica-coated alumite catalyst (Ni/silica/Al2O3/Al) with a silica-coating time of 20 h, C2H4 was reduced by 100% at 450°C and by 59% at 500°C compared with the levels seen for the alumite catalyst (Ni/γ-Al2O3/Al). A silica-coating time of 20 h was found to be the best for reducing ethylene formation. A temperature programmed desorption analysis with ammonia desorption also showed that the number of acidic sites per apparent surface area of the silica-coated alumite support (silica/Al2O3/Al) and the silica-coated alumite catalyst (Ni/silica/Al2O3/Al) was smaller than that of the alumite support (γ-Al2O3/Al) and the alumite catalyst (Ni/γ-Al2O3/Al) without any silica coating, respectively. These results suggest that the low level of ethylene formation with the silica-coated alumite support and silica-coated alumite catalyst was due to the smaller number of acidic sites. It is concluded that the silica-coating method is preferable for improving the properties of alumite supports and alumite catalysts for use in ethanol steam reforming.