Meena Marafi

Heavy oil hydrotreating catalyst rejuvenation by leaching of foulant metals with ferric nitrate-organic acid mixed reagents

Abstract Much effort has been devoted in recent years to develop processes for the rejuvenation of metal fouled spent catalysts from residue hydroprocessing units. In this paper we report the influence of adding ferric salts to some organic acids in selective extraction of foulant metals from the spent catalyst prior to decoking. Leaching experiments were carried out using two different organic acids, namely, oxalic acid and tartaric acid with and without ferric nitrate addition. The spent and the treated catalysts were characterized and the improvements in surface area, pore volume and HDS activity as a result of leaching with different reagents compared. The studies revealed that in the absence of ferric salts, the acids showed very poor activity for leaching foulant metals from coked spent catalyst. Addition of ferric nitrate enhanced the leaching efficiency of each acid to a different degree. The selectivity for the removal of the major metal foulant (vanadium) was different for different leaching reagents. The enhanced leaching by the ferric nitrate-organic acid system has been explained in terms of a synergistic mechanism involving oxidizing and complexing reactions. The improvements in surface area and pore volume recovery was found to be related to the extent of vanadium removal from the catalyst. The HDS activity of the catalyst also increased significantly by leaching of the deposited metals. The study showed that oxalic acid-ferric nitrate reagent was superior to other reagent systems in terms of selectivity for vanadium leaching as well as for surface area, pore volume and activity recovery.

Rejuvenation of residual oil hydrotreating catalysts by leaching of foulant metals: modelling of the metal leaching process

Abstract Increasing emphasis has been paid in recent years on the development of processes for the rejuvenation of spent residual oil hydroprocessing catalysts, which are deactivated by deposition of metals (e.g. vanadium) and coke. As part of a research program on this subject, we have investigated selective removal of the major metal foulant from the spent catalyst by chemical leaching. In the present paper, we report the development of a model for foulant metals leaching from the spent catalyst. The leaching process is considered to involve two consecutive operations: (i) removal of metal foulants along the main mass transfer channels connected to the narrow pores until the pore structure begins to develop and (ii) removal of metal foulants from the pore structure. Both kinetic and mass transfer aspects were considered in the model development, and a good agreement was noticed between experimental and simulated results.

Utilization Of Waste Spent HydroprocessingCatalyst: Development Of A Process For FullRecovery Of Deposited Metals And AluminaSupport

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.

Metal Reclamation from Spent Hydroprocessing Catalysts

Considering stringent environmental and safety regulations, metal recovery from spent catalysts is a more attractive option than landfilling. Metals such as Mo, Ni, Co, and V are highly valuable and are used extensively in the steel industry and in the manufacture of special alloys. They are usually manufactured from the ores and minerals containing them. Spent hydroprocessing catalysts could be used as a cheap source for these valuable metals. There are several studies that focus on recovery of Mo, Ni, V, and Co from the spent hydroprocessing catalysts. In addition, several companies are established for large-scale reclamation of metals and metal compounds from spent hydroprocessing catalysts. This chapter discusses reclaiming metal from spent hydroprocessing catalysts. It reviews the information available in the literature both on the laboratory studies and industrial scale processes for recovery of metals from spent hydroprocessing catalysts. Most of the studies on recovery of metals from spent hydroprocessing catalysts involve leaching with the solutions of both inorganic and organic agents. Leaching with the aid of a microorganism, i.e., bioleaching, is attracting attention as well. The dissolution of metals in water may also be enhanced by roasting spent catalysts with compounds containing alkali metals, such as sodium and potassium. Two-stage processes may employ both leaching and roasting. The volatilization or dissolution of metals of interest can be enhanced by chlorination. Attempts are made to develop novel methods, which could be competitive with conventional methods for metal reclamation.

The recovery of valuable metals and recycling of alumina from a waste spent hydroprocessing catalyst: extraction with Na salts

Considering the refinery importance, a spent catalyst recovery study was carried out on industrial spent residue hydroprocessing catalysts that contained high levels of metals. The spent catalyst was de-oiled, de-coked, crushed and ground to a fine powder, which was then subject to further treatment for metal recovery. In the extraction process, metals were recovered through hydrometallurgical routes using NaOH, and Na2CO3 as roasting mediator as well as an extracting agent. The effectiveness of the aqueous basic solution extraction of Mo, V, Ni and Al from the refinery spent catalyst is reported as a function of roasting agent, temperature, concentration, leaching time and temperature. The optimum leaching conditions were achieved in order to obtain a maximum recovery of Mo, Ni and V metals, corresponding to a time of 1 h, a temperature of 700°C and a concentration of 30 wt% with soda roasting, while the caustic digestion process’s maximum recovery for all metals was at 250°C in temperature. The metals were recovered as corresponding salt, while alumina was recovered as boehmite, which was further dried and calcined in order to get the corresponding oxides in pure form. The aim of this study is to recover or recycle a waste catalyst as valuable metals and support (alumina) from the spent catalyst.

Chapter 13 – Future Perspectives

Publisher Summary This chapter discusses the future perspectives of the spent hydroprocessing catalysts. The consumption of hydroprocessing catalysts and the associated generation of spent catalysts can be influenced by the future developments in petroleum refining. It is anticipated that during the next few years the consumption of crude will increase until it may level off before it will begin to decline under the pressure of the environmental lobby. In view of the political turmoil and other problems in various parts of the world, it is not easy to make an accurate prediction. However, a gradual decline in the supply of light and medium crudes, offset by an increased supply of heavy and extra heavy crudes, seems to be inevitable. Then, even during the period of an unchanged crude consumption, generation of spent catalysts will increase because heavy and extra heavy crudes will account for a greater portion of the overall crude envelope. Furthermore, emission of compounds such as CO2, SOX, NOX, and particulates create a problem for the development of the process. The transportation sector accounts for a large portion of emissions, such as CO2, SOX, NOX, and particulates. In the case of diesel fuel, sulfur in the fuel affects the performance of catalysts in catalytic converters. Consequently, emissions of NOX and particulate matter are increased. These problems may be alleviated by using ultra low sulfur fuels. In petroleum refineries, this translates into an increased consumption of catalyst and hydrogen.

Metal leaching from refinery waste hydroprocessing catalyst

ABSTRACT The present study aims to develop an eco-friendly methodology for the recovery of nickel (Ni), molybdenum (Mo), and vanadium (V) from the refinery waste spent hydroprocessing catalyst. The proposed process has two stages: the first stage is to separate alumina, while the second stage involves the separation of metal compounds. The effectiveness of leaching agents, such as NH4OH, (NH4)2CO3, and (NH4)2S2O8, for the extraction of Mo, V, Ni, and Al from the refinery spent catalyst has been reported as a function of reagent concentration (0.5 to 2.0 molar), leaching time (1 to 6 h), and temperature (35 to 60°C). The optimal leaching conditions were achieved to obtain the maximum recovery of Mo, Ni, and V metals. The effect of the mixture of multi-ammonium salts on the metal extraction was also studied, which showed an adverse effect for Ni and V, while marginal improvement was observed for Mo leaching. The ammonium salts can form soluble metal complexes, in which stability or solubility depends on the nature of ammonium salt and the reaction conditions. The extracted metals and support can be reused to synthesize a fresh hydroprocessing catalyst. The process will reduce the refinery waste and recover the expensive metals. Therefore, the process is not only important from an environmental point of view but also vital from an economic perspective.

Chapter 8 – New Catalysts From Spent Catalysts

There are several options for catalyst preparation after the operating size and form of spent catalysts is altered. Reprocessing of spent catalysts involves de-oiling, decoking, crushing and formatting to operating size and shape of catalyst particles. Metals which can be isolated from spent catalysts may be returned to the catalyst manufacturing companies and used for catalyst preparation. Other than hydroprocessing catalysts can be prepared as well. The extracts containing Mo, V and Ni obtained by leaching spent catalysts may be used directly for catalyst preparation by impregnating conventional supports. The same extract can be introduced to heavy feeds and as such act as catalyst during slurry bed hydroprocessing operations. There is a potential for the use of the crushed spent hydrodesulfurization catalyst for the hydrocracking of residual feeds in slurry bed reactor. Non-petroleum applications of spent catalysts have not yet been fully explored.

Valuable Materials From Spent Hydroprocessing Catalysts

The utilization of spent catalysts as raw materials in the production of a wide range of commercial products is an attractive option for their recycling from both environmental and economic points of view. In this regard, construction materials, e.g., cement, concrete, etc.; water treatment applications; abrasive materials; and synthetic aggregates have been receiving attention. Other useful materials prepared from spent hydroprocessing catalysts include fused alumina, synthetic aggregates, anorthite glass-ceramics, refractory cement, and refractory brick.

Spent Unconventional Hydroprocessing Catalysts

The unconventional hydroprocessing catalysts consist of precious metals such as platinum, palladium, ruthenium, and rhodium, usually referred to as platinum-group metals (PGMs). Although not a PGM, rhenium may also be a part of unconventional catalysts. In the case of bifunctional catalysts, the PGMs are combined with acidic supports with a wide range of surface acidity. Other supports include the traditionally used γ-Al 2 O 3 , SiO 2 , ZrO 2 , carbons, etc. The PGM-supported catalysts have been evaluated for upgrading of nonpetroleum feeds (biofeeds, Fischer–Tropsch syncrude, tight oil, etc.) as well as for applications under aqueous conditions. Despite extensive information on the development and testing of such catalysts, the properties of the corresponding spent catalysts (e.g., regenerability, toxicity, flammability, leachability, etc.) are little known. Because of their high value, regeneration for reuse and metal reclamation are the only options for the utilization of PGM-containing catalysts.