Activity of hydroprocessing catalysts prepared by reprocessing spent catalysts

The importance of pre-treatment of spent hydrotreating catalysts on metals recovery

“…FeS, NiS and MoS 2 were prepared according to procedure described in the literature. 20 3 were supplied by Merck and were used as received. The mass of each compound cited above employed in the experiments contains the same amount of the element present in the 5g of the catalyst sample.…”

“…1,2 The goal is to meet the increasing demand for ultra-low sulfur fuels. 3 These feedstocks contain considerable amounts of sulfur, nitrogen and metals. NiMo and CoMo/Al 2 O 3 are typical examples of spent catalysts coming from hydrotreating (HDT) units.…”

“…[4][5][6] The lifetime of the catalysts tends to decrease due to the more severe operations required. 3,4,7 Catalyst deactivation is basically due to coke and metals deposition over its surface. This phenomenon is characterized by a considerable loss of surface area and especially by a dramatic decrease of the catalytic activity.…”

“…10 Spent HDT catalysts have been classified as dangerous wastes by the "United States Environmental Protection Agency" (USEPA). [1][2][3][4][5] They may release toxic gases, are subject to spontaneous ignition and present heavy metals and carcinogenic compounds. Even after calcination at high temperature metals such as nickel, vanadium, cobalt and molybdenum may be leached with water.…”

“…4 Particularly many researches have been performed to process spent non-regenerable samples, because there is a limited number of regeneration cycles. 3 A slow but irreversible degradation of the catalyst structure takes place after each cycle. 2 In some cases it is possible to restore much of the original catalytic activity by removing the deactivation agent and/or reversing its effects on the active phase.…”