Hydrogen Production from Ethanol Using a CO₂ Absorption Ceramic and Base Metal Catalysts

Abstract

With the aim of developing a non-equilibrium reactor with a CO₂ recovery function for proton exchange membrane fuel cell (PEMFC) systems and other applications, steam reforming of ethanol was performed in a preliminary study in the presence of a CO₂ absorption ceramic at atmospheric pressure in a temperature range of 450–650°C using a plug flow reactor and commercially available reforming catalysts. The CO₂ absorption ceramic consisted of lithium silicate powder, which was granulated and coated with coarse alumina particles. Reaction products were analyzed by gas chromatography. The effects of the CO₂ absorption ceramic on hydrogen selectivity and species concentrations were estimated. It was concluded that steam reforming ethanol in the presence of the CO₂ absorption ceramic has high potential for application to a non-equilibrium reactor. Hydrogen production was enhanced and CO and methane production was suppressed significantly in the presence of the CO₂ absorption ceramic. For example, at a temperature of 500°C and with a commercial FCR-4-02 catalyst, hydrogen selectivity was 1.3 times higher than that in the absence of the CO₂ absorption ceramic, and the hydrogen concentration was 95 mol%-dry. This hydrogen concentration was considerably higher than that at chemical equilibrium, which was 63 mol%-dry. The methane concentration decreased from 10 to 4.2 mol%-dry, and the CO concentration decreased dramatically from 2.0 mol%-dry to less than the detection limit, which was about 100 ppm. The CO and methane concentrations were considerably lower than those at chemical equilibrium, which were 3.4 and 11 mol%-dry, respectively. These results indicate the potential for constructing a fuel processor system, which will not need either a high-temperature shift reactor (HTS) or a low-temperature shift reactor (LTS), for PEMFC applications.