The transformation of ethanol via the steam-reforming reaction can produce 6 mol H2 per mol of ethanol:
C2H5OH + 3H2O → 6H2 + 2CO2
We have studied the catalytic properties of Rh-Co supported on CeO2 and on ZrO2 for bio-ethanol steam reforming at 250-500 oC. The promotional effect of Co on Rh/CeO2 indicates that addition of Co can not only improve the activity for the H2 production, but also increase the selectivity to C2H4O and decrease the selectivity to CH4 at lower temperatures (< 350 oC). This implies that a new approach to high purity H2 production via C2H4O at lower temperatures may be made possible, because only C2H4O steam reforming can produce H2 free of CO and CH4: C2H4O + 3H2O → 2CO2 + 5H2. 4.6 mol H2 per mol of ethanol can be obtained at 450 oC.
To get an insight into the relationship between catalytic performance and bimetallic catalyst, we have studied the surface chemistry of Rh, Co, (Rh-Co) supported on CeO2 and on ZrO2 by temperature programmed reduction (TPR) and transmission electron microscopy (TEM). TPR study suggests that Rh-Co alloy particles can be more efficiently formed from (Rh(NO3)3 + Co(NO3)2) than from other monometallic compounds. TEM study indicates that such Rh-Co alloy particles are fairly fine. The results are of significance for the preparation of alloy catalysts from monometallic compounds and their applications in bio-ethanol steam reforming and water gas shift for the purpose of suppressing coking on the catalyst surfaces.