Steam reforming of ethanol with co-fed oxygen and hydrogen over Ni on high surface area ceria support

Ethanol steam reforming with/without co-fed oxygen and hydrogen over Ni on high surface area (HSA) CeO2 support, synthesized via a surfactant-assisted method, (Ni/CeO2 (HSA)) was studied under solid oxide fuel cell (SOFC) operating conditions for later application as an in-stack reforming catalyst. The catalyst provides considerably higher reforming reactivity and excellent resistance towards carbon deposition in comparison with Ni/Al2O3 and Ni on conventional ceria (Ni/CeO2 (low surface area; LSA)). At the temperature above 800 °C, the main products from the reforming processes over Ni/CeO2 (HSA) were H2, CO, and CO2 with some amount of CH4 depending on the inlet steam/ethanol and co-fed reactant (i.e. O2 and H2)/ethanol ratios, whereas high hydrocarbon compound i.e. C2H4 was also observed from the reforming of ethanol over Ni/CeO2 (LSA) and Ni/Al2O3. An addition of O2 (as oxidative steam reforming) and H2 significantly reduced the degree of carbon deposition. The presence of both reactants also promoted the conversions of hydrocarbon presented in the system (i.e. CH4 and C2H4) to CO and H2. The major consideration of these additions is the suitable co-fed reactant/C2H5OH ratio. The presence of too high oxygen concentration could oxidize Ni particles to NiO, which resulted in a lower reforming reactivity, and also combusts H2 to H2O. The suitable O2/C2H5OH molar ratio for the oxidative steam reforming of Ni/CeO2 was 0.4, which is less than that of Ni/Al2O3. An addition of too high hydrogen content slightly decreased the catalyst activity, which could be due to the active site competition of nickel particle and the inhibition of gas–solid redox reactions between the gaseous hydrocarbon components with the lattice oxygen (OOx) on the surface of CeO2 support in the case of Ni/CeO2.

Graphical abstractNi on high surface area CeO2 support (Ni/CeO2 (HSA)) provides considerably higher ethanol steam reforming reactivity (with/without co-fed oxygen and hydrogen) with excellent resistance toward carbon deposition compared to Ni/Al2O3 and Ni on conventional ceria (Ni/CeO2 (LSA)). The additional of O2 (as oxidative steam reforming) and H2 significantly reduced the degree of carbon deposition. The presence of both reactants also promoted the conversions of hydrocarbon presented in the system (i.e. CH4 and C2H4) to CO and H2. Importantly, the major consideration of these adding is the suitable co-fed reactant/C2H5OH ratio.Comparison of the conversion and product distributions (EtOH (×), H2 (●), CO (○), CO2 (♢), CH4 (♦), C2H6 (▵), and C2H4 (▴)) from steam reforming (small symbols with dot lines) (4 kPa C2H5OH, and 12 kPa H2O) and autothermal reforming (large symbols with solid lines) (4 kPa C2H5OH, 12 kPa H2O, and 1.6 kPa O2) of ethanol over Ni/CeO2 (HSA). Figure optionsDownload full-size imageDownload as PowerPoint slide