Hydrogen production from steam reforming of ethanol with nano-Ni/SiO2 catalysts prepared at different Ni to citric acid ratios using a sol-gel method

Steam reforming of ethanol to produce hydrogen was carried out using a two-stage reaction system with several nano-Ni/SiO₂ catalysts prepared at different citric acid (CA) contents using the sol-gel process. The fresh (non-calcined and calcined) catalysts and the reacted catalysts were analysed using surface area and pore size analysis, Fourier-transform infrared (FTIR) spectroscopy, thermo-gravimetry analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that a meso-structured material was produced at Ni:CA ratios lower than 1:0.5; and the pore volume of the catalyst was increased when more citric acid was used during the sol-gel preparation. Gas and hydrogen yield were observed to be increased when the Ni:CA ratio was reduced from 1:0.5 to 1:3.0; however, gas concentration was slightly changed for the catalysts prepared at different Ni:CA ratios. In addition, coke formation was increased from 0.7 to 7.5wt.% when the Ni:CA ratio decreased from 1:0.5 to 1:3.0. It was also found that the Ni/SiO₂ catalyst prepared at the low CA content (Ni:CA=0.5) was non-stable during the ethanol steam reforming process; since sintering was obtained as observed using TEM analysis of the used catalyst.