Steam Reforming of Sunflower Oil over Ni/Al Catalysts Prepared from Hydrotalcite-Like Materials

Abstract

Using catalytic steam reforming of biofuels to produce hydrogen for energy systems based on fuel cells is an option that may help to reduce the net emissions of CO₂ into the atmosphere. Vegetable oils are some of the most interesting options because of their high potential yield of hydrogen. They are, however, more difficult to reform than the light hydrocarbon feedstocks that are used for producing hydrogen industrially by steam reforming. Catalysts prepared from hydrotalcite-like materials are promising for use in the steam reforming of vegetable oils, since their catalytic activity is significantly higher than that of commercial catalysts for hydrocarbon steam reforming. In this paper, a study is made of how the nickel content of HT-derived catalysts affects their activity for steam reforming of sunflower oil. Three catalysts were prepared with Ni/Al atomic ratios of 1, 2, and 3, respectively. The samples were characterized by various techniques to correlate their activity with the structural characteristics of the catalysts: X-ray diffraction (XRD), BET, thermogravimetric analysis (TGA), and hydrogen chemisorption. The results showed that the catalyst activity increased as the nickel content in the material decreased. The support and its properties seemed to play a key role in the performance of the HT-derived catalysts. This is probably because a decrease in the Ni content produces a better dispersion of the metal and higher BET areas, which leads to a higher capacity for water adsorption. With the most active catalyst (Ni/Al of 1), 2.2 mol H₂/(g_cat h) was produced at 575 °C, 2 bar, and a steam-to-carbon ratio of 3.