Hydrogen production by steam reforming of ethanol on a RhPt/CeO2/SiO2 catalyst: Synergistic effect of the Si:Ce ratio on the catalyst performance

• Catalyst and operational conditions that maximized H2 yield from the steam reforming of ethanol was assessed.
• The new RhPt/CeO2-SiO2 (Si = 33 mol%) catalyst provided 30% more H2 compared to the reference RhPt/CeO2 catalyst.
• SiO2 in RhPt/CeO2 alters catalyst crystalline phase, basicity, surface area, and active particle size, increasing H2 yield.
• The new RhPt/CeO2-SiO2 (Si = 33 mol%) catalyst was active and stable during 72 h of continuous and startup/shutdown operation.

The effect of the Si content (0–100%) on a RhPt/CeO2-SiO2 catalyst was studied with respect to the steam reforming of ethanol (SRE) for H2 production. Activity tests were performed between 400 and 700 °C at atmospheric pressure; the stability was tested for 72 h in time-on-stream (TOS) and under several startup/shutdown perturbations. The maximum benefits were achieved with 33 mol% Si content in the support. The new RhPt/CeO2-SiO2 (RhPt/CeSi-33) catalyst delivered a H2 yield of 5.2 ± 0.2 mol H2/mol EtOH inlet, higher than the 4.0 ± 0.1 mol H2/mol EtOH inlet over the reference RhPt/CeO2 catalyst. The extra H2 production on RhPt/CeSi-33 was ascribed to the additional water activation on the SiO2 surface. A Si content of 33% in the support (RhPt/CeSi-33, Si:Ce ratio of 1:2) was found to provide the best catalyst. This Si content in the RhPt/CeSi-33 reduced catalyst sample promoted the following changes compared to the RhPt/CeO2 reference catalyst: (i) decreased the basicity of the support (from 341 to 259 μL CO2/g catalyst), (ii) reduced the crystalline size of CeO2 (from 46.0 to 22.6 nm), (iii) increased the catalyst surface area (from 36 to 129 m2/g catalyst), and (iv) decreased the active particle size (from 5.6 to 5.1 nm). The RhPt/CeSi-33 catalyst maintained its H2 yield by 72 h TOS and during the on/off test, showing promising features for future use in fuel cells.

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