The Study on the Effect of Ethanol Concentration on Co/SiO2 Catalyst for the Steam Reforming of Ethanol

Abstract

Ethanol obtained from the fermentation process can be steam reformed to hydrogen in the presenceof suitable catalyst, to be further used in fuel cells. In this study, the 10%Co/SiO₂catalyst was studied todetermine the suitable concentration of ethanol during the steam reforming. The ethanol concentrationwas varied from 15%, to 20% and 25% by volume at 450 ^oC reaction temperature and atmosphericpressure. The results showed that although the amount of hydrogen generated increased with ethanolconcentration, in term of hydrogen yield it decreased. It implied that smaller fraction of ethanol wasconverted to hydrogen at higher ethanol concentration, as shown by the decrease in hydrogen selectivity.On the other hand, the selectivity toward carbon monoxide was nearly constant with ethanol concentration.Thus, in term of product quality and hydrogen yield, 15% ethanol by volume seems to be the bestcondition for ethanol steam reforming. This result implied that bio-ethanol from fermentation process canbe directly used without distillation. The degree of utilization of the catalyst can be shown in term ofturnover frequency (TOF). It showed that higher TOF was obtained at higher ethanol concentrationmeaning that catalyst was more utilized at higher ethanol concentration. When increasing the cobalt loadingto 20%, it was found that the product quality was improved. In addition, the TOFs of the 10% and20% Co/SiO₂ were approximately the same at the same reaction condition, thus, the steam reforming ofethanol is the structural insensitive reaction. It suggested that at the same reaction temperature, siteactivity of cobalt metals varies only with the concentration of ethanol, not the percent loading. Resultsfrom the deactivation study after 6 hours of reaction showed no sintering of silica support but a slightdecrease in pore volume and pore size was observed, probably by a slight coke formation inside themesopores.

Keywords : Ethanol Steam Reforming / Co/SiO₂ Catalyst / Ethanol Concentration