Effect of higher alcohols on the performances of a l%Rh/ MgAl_2O_4/Al_2O_3 catalyst for hydrogen production by crude bioethanol steam reforming

摘要

The object of the present study was to study the role of alcohols, which are the major impurities found in a crude bioethanol feed, on the catalytic performances of a l%Rh/ MgAl_2O_4/Al_2O_3 catalyst during ethanol steam reforming. The alcohols studied were methanol, propan-1-ol, butan-1-ol, pentan-1-ol, isopropanol, 2-methyl propan-1-ol, 3-methyl butan-1-ol. Whereas the presence of 1% of methanol in the ethanol and water feed only slightly increased the hydrogen yield, the addition of the same amount of higher alcohols strongly decreased the stability of the catalyst during ethanol steam reforming, with a direct impact on the ethanol conversion and the hydrogen yield. It was shown that the deactivation is increased when the amount of carbon atoms in the molecule is increased. This effect is more pronounced in the presence of branched alcohols compared to the linear ones. It was demonstrated by studying the steam reforming of these higher alcohols that they are dehydrated to the corresponding olefin. The strong deactivation of the catalyst observed in the presence of higher alcohols was explained in terms of coke deposition.