Non-Equilibrium Hydrogen Production from Ethanol Using CO2 Absorption Ceramic and Precious Metal Catalysts

Abstract

Non-equilibrium H2 production from ethanol was achieved with precious metal catalysts using a CO2 absorption ceramic. The ceramic consisted of lithium silicate, which was granulated and coated with coarse alumina particles. H2 production in steam reforming of ethanol was enhanced and CO production was suppressed significantly in the presence of the CO2 absorption ceramic. The optimum temperature region for non-equilibrium H2 production was 500–550°C. For example, at a temperature of 500°C, at atmospheric pressure and with a 1 wt% Rh/CeO2 catalyst, the H2 concentration was 91 mol%-dry, which was considerably higher than that at the chemical equilibrium of 63 mol%-dry, and it was 1.4 times higher than that obtained without the CO2 absorption ceramic. A highest H2 concentration of 96 mol%-dry was obtained at 550°C. The CO concentration decreased dramatically at 500°C from 1.5 mol%-dry to less than the detection limit, which was about 1 × 10–2 mol%-dry. It was markedly lower than that of the chemical equilibrium. Similar results were also obtained with a 1 wt% Pt/CeO2 catalyst. At 500°C in particular, the concentration of H2 was fairly high at 89 mol%-dry and the CO concentration was lower than the detection limit. Carbon deposition was not observed visually in each case. It is concluded that non-equilibrium H2 production from ethanol with a precious metal catalyst in the presence of the CO2 absorption ceramic has a high potential for application to a non-equilibrium reactor for proton exchange membrane fuel cell (PEMFC) systems. A markedly low concentration of CO and a fairly high concentration of H2 will contribute to simplifying the complicated system configuration and to improving PEMFC performance, respectively.