Influence of solid–acid catalysts on steam reforming and hydrolysis of dimethyl ether for hydrogen production
Influences of solid–acid catalyst on dimethyl ether steam reforming (DME SR) and DME hydrolysis for hydrogen production were investigated. Series of zeolite (JRC-ZHM20(5), JRC-ZHM90(1) as H-mordenite type and JRC-Z5-90H(1) as ZSM-5 type) and of alumina (ALO8, TA1301, TA3301, DK503, NKHD24, NKHO24 and NK324) were used as acidic catalysts for DME hydrolysis. The composite catalysts of the acidic catalyst and CuFe2O4 spinel catalyst were employed for DME SR. DME SR activity strongly depended on the acidic catalyst that is active for DME hydrolysis. The hydrolysis of DME, the rate-determining step in DME SR, is equilibrium-controlled. Zeolite exhibited high activity for DME SR at a low temperature range of 200–275 °C, since the hydrolysis could effectively proceed over strong BrØnsted acid-sites approaching its equilibrium. Alumina possessing Lewis acid-sites was active for DME hydrolysis in the higher temperature range from 275 to 450 °C. CO2 and CO with relatively small amounts of CH4 were found as primary carbon-containing compounds when alumina was used as the acidic catalyst. In the case of zeolite, besides those carbon compounds, C3H8, i-C4H10, and n-C4H10 were detected during SR and hydrolysis of DME. It was found that not only the acid amount of the acidic catalysts, but also the acid strength and the type of acid-site definitely affected the steam reforming and hydrolysis activity. γ-Alumina (ALO8) mixed with CuFe2O4 exhibited the highest DME conversion and hydrogen production with optimum reforming temperature at 350–375 °C. Stable activity for DME hydrolysis was attained over ALO8 with high durability for 25 h.
Journal: Applied Catalysis A: General - Volume 304, 10 May 2006, Pages 40–48