Summary: | Palladium (Pd) and aluminium (Al) supported on SBA-15 were prepared as catalysts for cracking biodiesel waste from biodiesel production. Mesoporous silica SBA-15 was first synthesized by a hydrothermal method and then loaded with Al or Pd particles were loaded using postsynthesis or aqueous wet impregnation methods, respectively. The physical properties of the catalysts were characterized by X-ray diffraction (XRD), nitrogen (N<sub>2</sub>) adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The catalytic cracking performance of biodiesel waste was evaluated at reaction temperatures above 400 °C under a N<sub>2</sub> atmosphere in a batch reactor for 40 min in comparison with that for pure glycerol, where the conversion of biodiesel waste reached 86.8% with 10 wt% Pd-SBA-15 at 650 °C. The product types depended on whether the starting material was pure glycerol or biodiesel waste. The main gaseous products were carbon monoxide as synthesis gas, carbon dioxide, and 1,3-butadiene. Additionally, 2-cyclopenten-1-one and 2-propen-1-ol were major products in the liquid fraction, which can be used in pharmaceuticals and as a flame retardant, respectively.
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