Effects of ethylene glycol addition on the properties of Ru/Al2O3 catalyst prepared by sol-gel method

Ru/Al₂O₃ catalysts were prepared by sol-gel method with an organic additive (ethylene glycol). The effect of the addition of ethylene glycol on the properties of Ru/Al₂O₃ was characterized by BET, XRD, EXAFS, and TGA/DTA. Ethylene glycol was effective to promote the phase transition of -Al₂O₃ even at 800°C calcination with high surface area. This finding is ascribed to the modified structure of aluminum alkoxide by ethylene glycol addition in the solution state. Ethylene glycol is also effective to get small particles of ruthenium after the reduction at 500°C. The EXAFS and UV-Vis spectra of Ru complex revealed that the coordination structure of Ru depended on the additive used. The ethylene glycol sol prefers to form octahedral Ru complex. This Ru complex in alumina matrix is stable up to 200°C and forms small Ru oxide particles even at 300°C calcination. This suggests that ethylene glycol coordinates to the Ru complex as well as to aluminum ion in the initial state, which is important to control the final properties of the Ru/Al₂O₃ catalyst.