A highly stable Pd/SiO2/cordierite monolith catalyst for 2-ethyl-anthraquinone hydrogenation

Abstract

Catalyst stability is an urgent issue for ethyl-anthraquinone (EAQ) hydrogenation to produce the environment friendly oxidant H₂O₂. Herein, a highly stable egg-shell Pd/SiO₂/cordierite monolith catalyst (PSC) was prepared by an impregnation method. For comparison, a Pd/Al₂O₃/cordierite monolithic catalyst (PAC) was also prepared. The stability tests of the catalysts were conducted in a continuous trickle bed reactor at 40 °C with a high liquid space velocity of 25 h⁻¹. It turned out that the PSC catalyst obtained a stable H₂O₂ yield in the 1000 h test while the PAC catalyst deactivated in 100 h. The as-prepared catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption, NH₃ temperature programmed desorption (NH₃-TPD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H₂ temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS). N₂ adsorption and NH₃-TPD results showed that the PSC catalyst had a regular structure and very weak acidity, which contributed to improving the catalyst selectivity and stability. Besides, the lower support calcination temperature was found to be beneficial to improving the hydrogenation efficiency because of higher Pd dispersion and lower Pd loss.