Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H-2 production. SRE activity tests were performed using EtOH:H2O:N-2 (molar ratio 1:3:51) at a gaseous space velocity of 70,600 h(-1) between 400 and 700 degrees C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 degrees C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H-2 yield above 600 degrees C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H-2 selectivity of RhPt/CeO2 was ascribed to the formation of small (similar to 5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.