Recycling and Recovery Routes for Spent Hydroprocessing Catalyst Waste H. Al-Sheeha, Meena Marafi, Vira Raghavan, and Mohan S. Rana* Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109 Ahmadi, Kuwait ABSTRACT: This study investigates the recovery of Mo, V, and Ni metals from the industrial spent hydroprocessing catalyst. These catalysts are not viable to regenerate mainly due to the metal deposition. The study was carried out on industrial spent residue hydroprocessing (ARDS) catalysts that contained high levels of metals. In the extraction process, metals were recovered through pyrometallurgical and hydrometallurgical routes. The possibility of recycling of total spent catalyst (TSC) was studied 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 was studied. The metals were leached out in the solution while the 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. 1. INTRODUCTION In recent years, due to the depletion of light crude, poor quality (high metals, high asphaltene, and low API gravity) crude oil is being explored and processed in petroleum refineries. It has been also estimated that about 80% of the petroleum streams pass though hydroprocessing in order to improve fuel quality. Thus, depending on the type of feedstock and process unit severity, the cycle length of a fixed bed hydroprocessing catalyst is typically between 6 months and 2.5 years. Moreover, in order to maintain the quality of the product, time-on-stream is compensated by a progressive increase in catalyst bed temperature. When the catalyst fails to produce the product of the required quality, the catalyst is deactivated and requires regeneration or replacement. Usually, catalyst deactivation is due to three main causes: carbon (coke) laydown, active phase sintering, and metal poisoning. In recent years, catalysts have played a key role in the refining of petroleum to produce clean fuels and many other valuable products. 1,2 Therefore, hydro- processing catalysts have become widely accepted and are even preferred by the industry due to a number of reasons. One reason is that they result in purification of various petroleum streams, particularly for the upgrading of heavy oils and residues. 3 In the residue hydrotreating process, the catalysts which consist of Mo with promoter Co (Ni) on alumina support enhance the removal of undesirable impurities such as sulfur, nitrogen, and metals by hydrodesulfurization, hydro- denitrogenation, and hydrodemetallization reactions, respec- tively. 4-6 Hence, catalysts used for this process are deactivated rapidly by coke and metal (V and Ni) deposits and have a short life (6-12 months). Spent hydroprocessing catalysts are the major solid wastes of refinery industries and contain various hazardous components, such as Al, V, Mo, Co, Ni, As, and Fe as well as nonmetallic elements such as elemental sulfur, carbon, and oils that are potentially hazardous to the environment. 7 In the refinery, one of the main causes of industrial pollution is the discharge or disposal of spent hysroprocessing catalysts, which contains valuable components of the catalyst. Spent hydroprocessing catalysts recovery have gained importance due to environ- mental regulations which registers spent catalyst as hazardous waste materials. For example, Kuwait refinery produces ca. 6000 ton/y spent catalyst from bottom of barrel (ARDS) processes, which contain valuable metals such as molybdenum, vanadium, nickel, cobalt, etc. Thus, besides the environmental issues with disposal, spent catalysts containing high metal concentrations can serve as secondary raw materials. A variety of processing approaches for recovering metals from the spent catalysts has been proposed. 2 Techniques such as direct smelting, calcination and smelting, chlorination, and salt roasting are applied for metal recovery from spent hydro- processing catalysts. 8,9 Also, many reagents, such as NaOH, H 2 SO 4 , NH 3 , (NH 4 ) 2 SO 4 , and oxalic acid with H 2 O 2 and Fe(NO 3 ) 2 , have been tested. 10-12 Hence, the disposal of spent catalyst poses an unavoidable environmental issue, 13 which essentially requires high capital investment, huge swaths of land, and massive efforts. Kuwait, at present, is producing around 2.6 million bbl/d (Mbpd) of conventional crude oil. It has a refining capacity of about 936 000 bbl/d in its three refineries, which is likely to increase to 2 Mbpd with the addition of the fourth refinery. Kuwait has a total atmospheric residue (AR) hydrotreating capacity of around 216 000 bpd. 14 The Kuwait oil industry has already embarked on plans to expand the exploitation of Kuwait heavy oil reserves, including Lower Fars. Plans are on to construct a Received: June 17, 2013 Revised: August 12, 2013 Accepted: August 14, 2013 Published: August 14, 2013 Article pubs.acs.org/IECR © 2013 American Chemical Society 12794 dx.doi.org/10.1021/ie4019148 | Ind. Eng. Chem. Res. 2013, 52, 12794-12801