Utilization of waste spent hydroprocessing catalyst: development of a process for full recovery of deposited metals and alumina support

Abstract

An emphasis has been placed on investigation spent hydroprocessing catalyst recovery due to environmental regulations which register spent catalysts as hazardous waste materials. Kuwait refinery produces ca. 6000 ton/year spent catalysts from the bottom of the barrel (ARDS) processes, which contain valuable metals such as molybdenum, vanadium, nickel or cobalt etc. These catalysts are not viable to regenerate mainly due to the metal deposition. The present study is carried out on industrial spent residue hydroprocessing (ARDS) catalysts that contain high levels of metals. The possibility of recycling total spent catalysts (TSC) was studied by using various steps such as deoiling, drying, grinding, sieving and decoking. In the subsequent steps, the digested spent catalysts were treated with acid-base reactions in order to separate the various components of the spent catalyst. Using various leaching reaction conditions such as acid-base concentration, reaction pH in aqueous as well as organic mediums were studied. The metals were leached out in the solution while alumina support was recovered as bulk solid in the form of boehmite. The recovered alumina is further treated hydrothermally and recovered as boehmite, samples were characterized by surface area, pore volume, and pore size distribution measurements. Hence, recovery of valuable metals from the spent catalysts is an attractive option for their recycling and utilization. Therefore, TSC recovery is not only important from an environmental point of view but also very vital from an economic viewpoint.

Enhanced recovery of valuable metals from spent lithium-ion batteries through optimization of organic acids produced by Aspergillus niger

“…A low K a value indicates greater acid strength and a smaller conjugated base has been produced by the acid. These values are related to the solution ionic strength required for interaction with metal cations (Marafi et al, 2012). An organic acid structure with more carboxyl groups is beneficial for metal leaching to form stable ligands.…”

“…Complex ion stability is denoted by its formation constant, k. A complex ion contains a central metal ion to which are bonded two, four or six ionic or neutral species (ligands) (Marafi et al, 2012).…”

Extraction of molybdenum from a spent HDS catalyst using alkali leaching reagent

“…Many research works have focused on recycling of valuable metals from the spent HDS catalyst, following the conventional pyrometallurgical and hydrometallurgical process routes along with the bioleaching route [6][7][8][9][10][11][12][13][14]. The hydrometallurgical route includes leaching by using different agents for example; i) acidic agents, i. e., sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), oxalic acid (COOH)2, and citric acid (C6H8O7) to selectively recover molybdenum or vanadium, ii) alkali leaching, i.e., sodium hydroxide (NaOH) and potassium hydroxide (KOH), iii) ammonium salts leaching using ammonium hydroxide (NH4OH), ammonium carbonate (NH4)2CO3, and ammonium sulfate (NH4)2SO4, and iv) bio-reagents involving microorganisms in which their metabolisms require aerobic oxidation of reduced sulfur compounds such as bacteria and fungi.…”

Role of Edta on Metal Removal From Refinery Waste Catalysts

“…Some other methods require high energy input and further generate environmental concerns [3]. However, mineral acids (or basic) have the disadvantage of being corrosive and require special handling and storage, and expensive materials for the equipment [1], [9]. Alternatively, organic acids can form soluble complexes with metal ions and can be extracted under mild conditions [10].…”

“…Co, Ni, Mo, and V), which is specific to its complex formation at various pH. [8], [9]. Moreover, due to the commercial importance of EDTA, its (chelant) reuse and conservation remain the second objective of this study.…”