Hydrogen Production from Ethanol by Equilibrium Shifting Using Lithium Silicate Pellet as CO₂ Absorbent

Abstract

Equilibrium shifting is considered to be effective for promoting H₂ production by ethanol (C₂H₅OH) steam reforming. In this study, a packed bed reactor with a mixture of reforming catalyst and CO₂ absorbent was used. Lithium silicate (Li₄SiO₄) was applied as the absorbent, which Toshiba has developed. In the case of Li₄SiO₄, CO₂ emission occurs at considerably lower temperature than in the case of the well-known calcium oxide (CaO) and the reaction between Li₄SiO₄ and CO₂ is highly reversible. This is a report of the equilibrium-shift effect on steam reforming of C₂H₅OH, which was obtained by using Li₄SiO₄ pellet (ca. 5 mm). Experiments showed obvious effect, which resulted in keeping not only the concentration of H₂ at 99.3 dry vol% but also that of CO at 0.11 dry vol% for 0.5 hour. This result indicates the possibility of dispensing with a CO-shift reactor and simplifying either CO removal reactor or purification apparatus, in the case of a reformer using a packed bed of pellets. We believe that it would improve the conventional H₂ production system.