Title of Invention

"A PROCESS FOR RECOVERY OF NICKEL FROM SPENT NICKEL CATALYST OF AN OIL REFINERY PLANT"

Abstract

The present invention relates to a process for recovery of nickel from spent nickel catalyst of an oil refinery plant. This invention particularly relates to a process for extraction of nickel from spent catalyst by direct leaching with sulphuric acid in presence of small amount of a small amount of promoter selected from chlorate, perchlorate, permanganate, iodate, periodate salts of sodium, potassium. The invention is useful for recovery of nickel from the waste material such as spent catalyst, which is one of the rich sources of nickel and therefore important from the view of environmental protection, resource recycling and conservation. Novelty of the present invention is in the use of a promoter which has not been used earlier for direct leaching of nickel from nickel catalyst. Another feature of the invention is complete nickel dissolution (more than 99.5%) from the spent catalyst without any prior treatment such as reduction/alkali/chlorination roasting etc. which are necessary steps in earlier developments.

Full Text

The present invention relates to a process for recovery of nickel from spent nickel catalyst of an oil refinery plant This invention particularly relates to a process for extraction of nickel from spent catalyst by direct leaching with sulphuric acid in presence of small amount of a small amount of promoter. The invention is useful for recovery of nickel from the waste material such as spent catalyst, which is one of the rich sources of nickel and therefore important from the view of environmental protection, resource recycling and conservation. The consumption of nickel in India is about 20,000 MTPY (metric tonnes per year) which is entirely imported. Though several by-products/wastes such as nickel sludge generated during the pickling of stainless steel, grinding waste of AINiCo magnets, and spent catalyst from the fertiliser, petrochemical and hydrogenation plants are available, at present very few of such sources are being exploited commercially. Recovery of metal values from such sources not only enhances the resource base but also results in corresponding decrease in the requirement of mining the ore and also reduces the problem of disposal of these wastes in environment friendly manner, besides energy conservation. Spent catalysts are one of the richest sources of nickel and considered as industrial wastes and controlled under strict environmental protection law. It is required to be disposed off in secure landfill/storage or recycled. It also contains various metals of strategic importance and therefore the recovery of such metals is important from the view of environmental protection and resource recycling. Nickel based catalysts are the catalyst of choice in several industries due to their low cost compared with other competing substitutes. Such catalysts use alumina and silica as supports. Deactivated nickel catalysts are not considered to be regenerable by ordinary techniques and also pose a significant waste disposal problem. Hence, it is necessary to develop new extraction techniques for processing of such spent catalyst to obtain pure metal for reuse. Therefore, to meet the ever-growing demand, the effort has been made to provide an innovative and cost effective process for recovery of nickel from the spent catalyst of the oil refinery plants. Considerable efforts have been made to recover nickel from spent catalyst by hydrometallurgical processes. In most of the earlier work the spent catalyst had to undergo pre-treatment step to processing (Inooka Masayoshi, Japan, Kokai, Yokyo, Koho 7811621, 11 Oct. 1978; Telly, George L., US 4, 721600, 20 Jan. 1988; Giurea et al ROM RO 85578, 29 Sept. 1984). In general chlorination (Gravey, G., LeGroff J. and Gonin C, Jan. 8, 1980, U. S. Patent 4182747), pressure leaching with ammonium hydroxide -ammonium carbonate or sodium hydroxide (Gutnikov G. March 2, 1971, U. S. Patent 3567433; Millsap W. A. and Reisler N., 1978, Eng. And Min. J., Vol. 179(5), p. 105.) and sodium carbonate roasting (Castanga H., Gravey G. and Roth A, Feb. 21, 1978, U. S. Patent 4075277) were applied. After a pre-treatment spent catalyst is directly leached with water/acid/alkali. Reduction roasting followed by sulphuric acid leaching of a spent catalyst from hydrogenation plant to produce nickel oxide reported only 83% of overall recovery (P. Alex, T. K. Mukherjee and M. Sundaresan, 1991, Metals Materials and processes. Vol. 3(2), p.-81). Roasting followed by selective chlorination at 400 °C of spent catalyst under CI2 + air, CI2 + N2 and CI2 + N2 was investigated and maximum recovery of only 80% was reported (Gaballah I. and Dona M., 1993, The Paul E. Queneau Int. Symp. on Extractive Metallurgy of Copper, Nickel and Cobalt, Vol. I, p. 1253, Ed. R. G. Reddy and R. N. Weizenbach, minerals, Metals and Material Society). Al-Mansi et. al. reported (Al-Mansi, N. M. and Abdel Monem, N. M., 2002, Waste Management, Vol. 22, p. 85) the leaching of nickel from a alumina based spent catalyst using very high concentration of sulphuric acid (up to 50%) to recover nickel as sulphate crystal suggested neutalisation method to consume extra acid. Therefore, direct leaching of spent catalyst reported having several disadvantages such as requirement of high strength acid and poor nickel dissolution with simultaneous dissolution of other metal ions, which are the major problems for the subsequent processing steps of final product recovery. Neutralisation of highly acidic leach liquor requires high amount of alkali and will generate huge quantity of waste cake, which will add cost to the process and often found impossible, besides creating environmental problem. Though several attempts have been made to recover nickel by various processes involving pre-treatment such as roasting, reduction/alkali/chlorination roasting etc. followed by acid/alkali/neutral leaching to recover nickel. However, there is rarely any attempt made to accelerate the metal dissolution process by adding a promoter such as sodium/hydrogen peroxide, potassium permanganate etc. The main object of the present invention is to provide a process for recovery of nickel from spent catalyst of an oil refinery plant, which obviates the drawbacks as detailed above. Another object of the present invention is to provide a leaching process for extraction of nickel from spent nickel catalyst in presence of little amount of promoter which eliminates necessity of pre-treatment steps usually common to all established processes and avoids requirement of high strength acid for selective and quantitative dissolution of nickel from this resource. Still another objective of the present invention is to develop a suitable process for the recovery of nickel from an indigenous spent catalyst generated in substantial quantity in hydrogenation plant, which can operate in medium and small scale. Accordingly, the present invention provides a process for recovery of nickel from spent nickel catalyst of an oil refinery plant which comprises: i) removing the oil by burning the spent catalyst in the temperature range of 300 to 600 °C, ii) adding the above nickel catalyst to the sulphuric acid solution while stirring and maintaining the solid liquid ratio in the range of 1/5 - 1/20 (w/v), iii) adding a chlorate, perchlorate, permanganate, iodate, periodate based additive in the range of 0.01 - 1.0% (w/w) of the catalyst, iv) keeping the temperature of the slurry in the range of 60 to 100 °C for a period of 0.5 to 4 h, v) allowing the slurry to settle and then filtering the slurry to obtain leach liquor containing nickel, vi) purifying the said leach liquor by precipitating iron and other impurities using known method to obtain pure nickel sulphate solution, vii) evaporating the purified leach liquor and crystallising nickel as nickel sulphate crystal, viii) precipitating nickel as nickel hydroxide from the solution obtained in step (vi) and reducing it by known process for producing nickel metal powder or nickel oxide. In an embodiment of the present invention the spent nickel catalyst used may be selected from the nickel catalyst having particle size in the range of 10 to 100 [ivn and may have composition in range : Ni : 5-50%, Fe : 0.1-2%, AI2O3 : 0-10%, Si02 : 10-60% In another embodiment of the present invention the promoter may be selected from chlorate, perchlorate, permanganate, iodate, periodate salts of sodium, potassium and like, and may have concentration in the range of 0.01 - 1.0% (w/w). In still another embodiment of the present invention the sulphuric acid may be of commercial grade and may have concentration in the range of 3 -15% (v/v). In the process of present invention the leach slurry is filtered and the residue is washed with fresh deionised water. The wash liquor containing 5-30 g/L Ni is recycled for the leaching of the fresh spent catalyst by adding the desired amount of acid. In the present invention the nickel catalyst is leached in sulphuric acid medium using a promoter. Nickel present in the spent catalyst is in oxide phase and dissolution in sulphuric acid occurs as : Promoter ^ NiO + H2SO4 ► NiS04 + H2O (1) The iron and silica free leach liquor is evaporated and crystallise nickel as nickel sulphate. The purified leach liquor can also be precipitated as nickel hydroxide and nickel metal from this can be obtained by known method called hydrogen/carbothermic reduction process. Alternatively nickel metal powder can be produced by the known process by aqueous hydrogen reduction of purified leach liquor. Novelty of the present invention is the use of a promoter which has not been used earlier for direct leaching of nickel from nickel catalyst. Another feature of the invention is complete nickel dissolution (more than 99.5%)) from the spent catalyst without any prior treatment such as reduction/alkali/chlorination roasting etc. which are necessary steps in earlier developments. The following examples are given by way of illustration and should not be construed to limit the scope of invention. EXAMPLE -1 300 g of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% SiOa is heated at 300 0C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. Total weight loss was found to be 54.3%. After heat treatment the treated material was found to contain 47.8% Ni and 38.2% Si02. 20 g of treated spent nickel catalyst sample is added to 200 ml of 5.5 vol% sulphuric acid in three naked flask and kept over a thermostatically controlled hot plate having stirring arrangement by a magnetic needle. The temperature of the slurry is maintained at 90 °C. Samples collected at different time intervals are filtered and analysed for nickel content. Recovery of nickel increases with leaching time. Recovery data at different time intervals are incorporated in Table 1. A maximum of 11.6% nickel recovery is achieved in 2 h. Table 1: Percentage nickel recovery at different time intervals. (Table Removed) EXAMPLE - 2 300 g of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% Si02 is heated at 300 °C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. Total weight loss was found to be 54.3%. After heat treatment the treated material was found to contain 47.8% Ni and 38.2% Si02. 20 g of treated spent nickel catalyst sample is added to 200 ml of 11.0 vol% sulphuric acid in three naked flask and kept over a thermostatically controlled hot plate having stirring arrangement by a magnetic needle. The temperature of the slurry is maintained at 90 °C. Samples collected at different time intervals are filtered and analysed for nickel content. Recovery of nickel increases with leaching time. Recovery data at different time intervals are incorporated in Table 2. A maximum of 12.6% nickel recovery is achieved in 2 h. Table 2 : Effect of acid concentration on recovery of nickel at different time intervals. (Table Removed) EXAMPLE -3 300 g of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% Si02 is heated at 300 °C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. Total weight loss was found to be 54.3%. After heat treatment the treated material was found to contain 47.8% Ni and 38.2% Si02. 20 g of treated spent nickel catalyst sample is added to 200 ml of 5.5 vol% sulphuric acid in three naked flask and kept over a thermostatically controlled hot plate having stirring arrangement by a magnetic needle. 0.005 g of potassium permanganate is added to the reaction mixture. The temperature of the slurry is maintained at 90 °C. Samples collected at different time intervals are filtered and analysed for nickel content. Recovery of nickel increases with leaching time. Recovery data at different time intervals are incorporated in Table 3. A maximum of 94.6% nickel recovery is achieved in 2 h. Table 3 : Effect of promoter on the percentage nickel recovery at different time intervals. (Table Removed) EXAMPLE-4 300 g of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% Si02 is heated at 300 °C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. Total weight loss was found to be 54.3%. After heat treatment the treated material was found to contain 47.8% Ni and 38.2% Si02. 20 g of treated spent nickel catalyst sample is added to 200 ml of 5.5 vol% sulphuric acid in three naked flask and kept over a thermostatically controlled hot plate having stirring arrangement by a magnetic needle. 0.01 g of potassium permanganate is added to the reaction mixture. The temperature of the slurry is maintained at 90 °C. Samples collected at different time intervals are filtered and analysed for nickel content. Recovery of nickel increases with leaching time. Recovery data at different time intervals are incorporated in Table 4. A maximum of 97% nickel recovery is achieved in 2 h. Table 4 : Effect of promoter on the percentage nickel recovery at different time intervals. (Table Removed) EXAMPLE -5 300 g of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% SiOa is heated at 300 °C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. Total weight loss was found to be 54.3%. After heat treatment the treated material was found to contain 47.8% Ni and 38.2% Si02. 20 g of treated spent nickel catalyst sample is added to 200 ml of 5.5 vol% sulphuric acid in three naked flask and kept over a thermostatically controlled hot plate having stirring arrangement by a magnetic needle. 0.05 g of potassium permanganate is added to the reaction mixture. The temperature of the slurry is maintained at 90 °C. Samples collected at different time intervals are filtered and analysed for nickel content. Recovery of nickel increases with leaching time. Recovery data at different time intervals are incorporated in Table 5. ~95% of nickel recovery is achieved within 0.5 h time interval. A maximum of 99.5% nickel recovery is achieved in 2 h. Table 5 : Effect of promoter on the percentage nickel recovery at different time intervals. (Table Removed) EXAMPLE - 6 1 kg of nickel catalyst of composition : 21.9% Ni, 0.08% Fe, 0.07% S, and 17.5% Si02 is heated at 300 °C for 2 h to remove major part of the oil and subsequently heated at 600 °C for 1 h for complete removal of the volatile material. The above material mixed with 0.5 g of potassium permanganate is added to 4 L of 6.25 vol% sulphuric acid in a 5 L capacity beaker and kept over a hot plate. It is kept under stirring with the help of a glass stirrer fitted to a motor. The temperature of the slurry is maintained at 90 °C through out the leaching experiment. After 2 h of leaching the slurry is kept for settling. The leach liquor, wash solution and residue analysis are given in Table 6. Residue basis recovery obtained is 99.2%. (Table Removed) he major advantages of the present invention are given here ; 1. The process requires only little excess to the stoichiometric amount of acid for almost complete dissolution of nickel. 2. Leach residue containing silica can be produced as a value added by-product. 3. The process operates at low temperature and low acid concentration, and therefore special material of construction is not required. 4. The process require less amount of hydroxide/carbonate in the purification step and generates less amount of residue, and therefore account for low loss of metal values at this stage. 5. Leaching generates concentrated leach solution and requires less heat energy for crystallisation. 6. The process is much less corrosive as compared to chlorination roasting often followed. 7. The process is much easier and involves lesser number of steps. 8. The process requires much less capital investment and can be operational in medium and small scale. We Claim 1. A process for recovery of nickel from spent nickel catalyst of an oil refinery plant which comprises: i) removing the oil by burning the spent catalyst in the temperature range of 300 to 600 °C, ii) adding the above nickel catalyst to the sulphuric acid solution while stirring and maintaining the solid liquid ratio in the range of 1/5 - 1/20 (wt./vol.), iii) adding a chlorate, perchlorate, permanganate, iodate, periodate based additive in the range of 0.01 - 1.0% (w/w) of the catalyst, iv) keeping the temperature of the slurry in the range of 60 to 100 °C for a period of 0.5 to 4 h, v) allowing the slurry to settle and then filtering the slurry to obtain leach liquor containing nickel, vi) purifying the said leach liquor by precipitating iron and other impurities using nickel hydroxide/carbonate and filtering to obtain pure nickel sulphate solution, vii) evaporating the purified leach liquor and crystallising nickel as nickel sulphate crystal, viii) precipitating nickel as nickel hydroxide from the solution obtained in step- vi) and reducing it by known process for producing nickel metal powder or nickel oxide. 2. A process as claimed in claim 1, wherein the spent catalyst used is selected from the nickel catalyst of particle size in the range 10 to 100 µm and have composition in the following range: Ni : 5-50%, Fe : 0.1-2%, Al2O3 : 0-10%, SiO2 : 10-60% 3. A process as claimed in claims 1 - 2, wherein the additive is selected from chlorate, perchlorate, permanganate, iodate, periodate salts of sodium, potassium and like and have concentration in the range of only 0.1 - 1% (w/w). 4. A process as claimed in claims 1 - 3, wherein the used sulphuric acid is of commercial grade and have concentration in the range 5-15 vol.%. 5. A process for recovery of nickel from spent nickel catalyst of an oil refinery plant substantially as herein described with reference to the examples.

Documents:

1868-DEL-2004-Abstract-(16-03-2011).pdf

1868-del-2004-abstract.pdf

1868-DEL-2004-Claims-(16-03-2011).pdf

1868-del-2004-claims.pdf

1868-DEL-2004-Correspondence Others-(16-03-2011).pdf

1868-DEL-2004-Correspondence-Others-(18-05-2011).pdf

1868-del-2004-correspondence-others.pdf

1868-DEL-2004-Description (Complete)-(16-03-2011).pdf

1868-del-2004-description (complete).pdf

1868-DEL-2004-Form-1-(16-03-2011).pdf

1868-DEL-2004-Form-1-(18-05-2011).pdf

1868-del-2004-form-1.pdf

1868-del-2004-form-18.pdf

1868-del-2004-form-2.pdf

1868-DEL-2004-Form-3-(16-03-2011).pdf

1868-del-2004-form-3.pdf

1868-del-2004-form-5.pdf