Hydrogen-rich gas production via steam gasification of food waste over basic oxides (MgO/CaO/SrO) promoted-Ni/Al2O3 catalysts

Abstract

Food waste, a renewable resource, was converted to H₂-rich gas via a catalytic steam gasification process. The effects of basic oxides (MgO, CaO, and SrO) with 10 wt% Ni/Al₂O₃ on the gasification properties of food waste were investigated using a U-shaped gasifier. All catalysts prepared by the precipitation method were analyzed by X-ray diffraction, H₂-temperature-programmed reduction, NH₃-temperature-programmed desorption, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The Ni/Al₂O₃ catalyst was reduced incompletely, and low nickel concentrations were detected on the surface of the alumina. The basic oxides minimized the number of acid sites and suppressed the formation of nickel-aluminate (NiAl_xO_y) phase in catalyst. In addition, the basic oxides shifted nickel-aluminate reduction reaction to lower temperatures. It resulted in enhancing nickel concentration on the catalyst surface and increasing gas yield and hydrogen selectivity. The low gas yield of the Ni/Al₂O₃ catalyst was attributed to the low nickel concentration on the surface. The maximum gas yield (66.0 wt%) and hydrogen selectivity (63.8 vol%) of the 10 wt% SrO- 10 wt% Ni/Al₂O₃ catalyst correlated with the highly dispersed nickel on the surface and low acidity. Furthermore, coke deposition during steam gasification varied with the surface acidity of the catalysts and less coke was formed on 10 wt% SrO- 10 wt% Ni/Al₂O₃ due to efficient tar cracking. This study showed that the steam gasification efficiency of the Ni/Al₂O₃ catalyst could be improved significantly by the addition of SrO.

Keywords: Basic oxides (MgO/CaO/SrO) promotion; Food waste steam gasification; Hydrogen-rich gas; Ni/Al(2)O(3) catalyst.