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

Abstract

Steam and autothermal reforming reactions of LPG (propane/butane) over high surface area CeO 2 (CeO 2 (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/Al 2O 3. These benefits of CeO 2 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. C 4H 10, C 3H 8, C 2H 6, C 2H 4, and CH 4) and the lattice oxygen (O O x ) take place on the ceria surface. The reactions of these adsorbed surface hydrocarbons with the lattice oxygen (C n H m + 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 (C n H m ⇔ nC + 2 mH 2). Afterwards, the lattice oxygen (O O x ) can be regenerated by reaction with the steam present in the system (H 2O + V O + 2e′ ⇔ O O x + H 2). It should be noted that V O denotes as an oxygen vacancy with an effective charge 2 +. At 900 °C, the main products from steam reforming over CeO 2 (HSA) were H 2, CO, CO 2, and CH 4 with a small amount of C 2H 4. The addition of oxygen in autothermal reforming was found to reduce the degree of carbon deposition and improve product selectivities by completely eliminating C 2H 4 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 CeO 2 (HSA) was 0.6.