Reactivation of Spent Pd/AC Catalyst by Supercritical CO2 Fluid Extraction

In this article, we reported a nondestructive and environmentally friendly method for the reactivation of a spent Pd/AC catalyst for the hydrogenation of benzoic acid by using supercritical CO2 (scCO(2)) fluid extraction. The effects of reactivation conditions, such as extraction temperature, pressure, CO2 flow rate, and time, on the activity of the reactivated Pd/AC catalyst, were presented. The catalyst was characterized by N-2 physisorption, laser particle size analysis, and transmission electron spectroscopy, and the liquid extract was analyzed by GC-MS. It is found that scCO(2) fluid extraction was very efficient in eliminating organic substances blocking the pores of the catalyst, while did not affect noticeably the granule size of the catalyst and the particle size of Pd. The reactivated Pd/AC catalyst regained more than 70% of the activity of the fresh 5.0 wt % Pd/AC catalyst, and has been successfully used in an industrial unit for the hydrogenation of benzoic acid. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 2382-2388, 2009