Reactivation of spent Pd/AC catalyst by supercritical CO₂ fluid extraction

Abstract

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 CO 2 (scCO 2 ) fluid extraction. The effects of reactivation conditions, such as extraction temperature, pressure, CO 2 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. V

Morphology-Tuning-Induced Highly Efficient Regeneration of Pt/C Nanoelectrocatalysts

“…On the other hand, in order to further confirm that the above regeneration protocol can be generalized to other practical Pt/C system, − the spent anode Pt/C (noted as Spent-Pt60/C ) nanocatalyst with Pt 60 wt% from direct methanol fuel cell (DMFC) system was studied here. As shown in Figure , after long-term working in DMFC system as anode catalyst for methanol electro-oxidation, the apparent activity (mA/mg cata ) decreased 64% on three-electrode system compared with the fresh Pt60/C .…”

“…In recent years, regeneration of supported precious metal catalysts through the redispersion of metals has been very desirable due to the limited resources of precious metals. − Traditionally, the catalysts were regenerated based on a simple reforming process without decreasing of metal loading or increasing of metal utilization (defined as activity per unit mass of metal). − In this way, the apparent activity of the regenerated catalysts and the utilization of precious metals are always lower than those of the fresh ones. Recently, we reported a new regeneration method for a Pt/C catalyst based on the additional carbon support (Scheme ).…”

Coke Removal from a Deactivated Industrial Diesel Hydrogenation Catalyst by Tetralin at 300–400 °C

“…Abdullah et al treated a deactivated industrial catalyst (D-cat) at 200 °C in N 2 atmosphere with toluene, tetrahydrofuran, dichloromethane, pyridine, and methanol and showed about 45% (including about 30% toluene soluble) coke removal in 5 min. Sagdeev et al and Zhang et al extracted deactivated industrial catalysts with supercritical CO 2 at 80 °C and 15 MPa and showed 70% recovery of the catalyst’s activity along with 73% recovery of the catalyst’s surface area, 86% recovery of the pore volume, and an increase in pore size from 1.82 to 1.87 nm. The high pressure used, however, hampers its application in the hydrotreating units.…”

Reactivation and Reuse of Platinum‐Based Spent Catalysts for Combustion of Exhaust Organic Gases

“…Although activation or rejuvenation of the spent catalysts was frequently reported, either by using chemical leaching solutions and/or oxidative thermal treatment [5][6][7][8][9][10], such traditional recovery processes are environmentally and atomically unfriendly due to the partly consumption of the support and acid, destruction of the catalyst structure, emission of CO 2 , and pollution of the waste acid. Moreover, these factors all lead to significantly increase capital and operating costs of the process [11,12]. Thus, it is highly desirable to develop a mild and environmentally friendly alternative to the recovery of the spent catalyst.…”

“…Thus, it is highly desirable to develop a mild and environmentally friendly alternative to the recovery of the spent catalyst. Although supercritical fluid-CO 2 extraction has been reported to be a nondestructive and environmentally friendly regenerating method [11,12], it still suffers from the special requirement for setup and process conditions.…”