Ni(II)-Al(III) layered double hydroxide as catalyst precursor for ethanol steam reforming:: Activation treatments and kinetic studies

The kinetic behaviour of the steam reforming reaction using Ni(II)-Al(III) layered double hydroxide (LDH) as catalyst precursor is studied. The carbonate form of Ni(II)-Al(III) LDH (takovite) was prepared using an homogeneous alkalinization procedure, by means of the thermal hydrolysis of urea. Different activation treatments of Ni(II)Al(III) precursor are analysed; it was found that the catalyst which presents the higher activity in methane steam reforming, is that obtained by pure H-2 reduction of precursor without previous calcination. The H-2 yield for ethanol steam reforming using the reduced LDH sample reaches values of 5 mol of H-2 per mol of ethanol in the feed. The others products obtained, operating between 823 and 923 K, are CO, CO2 and CH4. It is found that the reaction order respect to ethanol is lower than 1. It is verified that, for each reaction temperature, there is a water/ethanol molar ratio at which ethanol conversion has a maximum. It means that a competition between both reactants adsorbed on the same active sites is verified. (C) 2007 Elsevier B.V. All rights reserved.