Hydrogen production from steam and autothermal reforming of LPG over high surface area ceria

Steam and autothermal reforming reactions of LPG (propane/butane) over high surface area CeO2 (CeO2 (HSA)) synthesized by a surfactant-assisted approach were studied under solid oxide fuel cell (SOFC) operating conditions. The catalyst provides significantly higher reforming reactivity and excellent resistance toward carbon deposition compared to the conventional Ni/Al2O3. These benefits of CeO2 are due to the redox property of this material. During the reforming process, the gas-solid reactions between the hydrocarbons present in the system (i.e. C4H10, C3H8, C2H6, C2H4, and CH4) and the lattice oxygen (O-o(x)) take place on the ceria surface. The reactions of these adsorbed surface hydrocarbons with the lattice oxygen (CnHm + O-o(x) -> nCO + m/2(H-2) + V-o(..) + 2e') can produce synthesis gas (CO and H-2) and also prevent the formation of carbon species from hydrocarbons decomposition reactions (CnHm double left right arrow nC + 2mH(2)). Afterwards, the lattice oxygen (Oox) can be regenerated by reaction with the steam present in the system (H2O + V-o(..) + 2e' double left right arrow Oox + H2)- It should be noted that Vo(..) denotes as an oxygen vacancy with an effective charge 2(+). At 900 degrees C, the main products from steam reforming over CeO2 (HSA) were H-2, CO, CO2, and CH4 with a small amount of C2H4. The addition of oxygen in autothermal reforming was found to reduce the degree of carbon deposition and improve product selectivities by completely eliminating C2H4 formation. The major consideration in the autothermal reforming operation is the O-2/LPG (O/C molar ratio) ratio, as the presence of a too high oxygen concentration could oxidize the hydrogen and carbon monoxide produced from the steam reforming. A suitable O/C molar ratio for autothermal reforming of CeO2 (HSA) was 0.6. (c) 2005 Elsevier B.V. All rights reserved.