Recovery of Nickel from Spent Ni/Al2O3 Catalysts using Acid Leaching, Chelation and Ultrasonication

Pages: 14 (4182 words) Published: June 19, 2013
Research Journal of Recent Sciences ________________________________________________ ISSN 2277 - 2502 Vol. 1(ISC-2011), 434-443 (2012) Res.J.Recent.Sci.

Review Paper

Recovery of Nickel from Spent Ni/Al2O3 Catalysts using Acid Leaching, Chelation and Ultrasonication Oza R.* and Patel S.
Chemical Engineering Department, Institute Of Technology, Nirma University, Ahmedabad–382 481, INDIA

Available online at: www.isca.in
(Received 7th November 2011, revised 13th January 2012, accepted 30th March 2012)

Abstract
Supported nickel catalysts, containing 2.5% to 20% of nickel metal, are widely used in chemical industry for hydrogenation, hydrotreating, and steam-reforming reaction. These catalysts have specific life and are subsequently discarded due to its deactivation owing to coke deposition on its surface. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste and also it requires compliance with stringent environmental regulations. Also the cost and demand of nickel has been rising significantly. In this context recovery of nickel can serve both of the important issues. This review cum research work focuses on the recovery of nickel from spent nitrogenous catalyst using conventional acid leaching & chelation route and a novel technique Ultrasonication developed & implemented successfully by the authors. Using ultrasonication technique significantly faster recovery of nickel salt (50 minutes) was accomplished compared to chelation route (7-8 h) and acid leaching (5-6 h). The %recovery and purity is significantly high for ultrasonication route compared to conventional acid leaching and chelation technique. The recovered nickel salts can be recycled for the preparation of fresh catalysts and promises to be a good industrial process for handling 1-2 t per batch of spent nickel catalyst. Keywords: Spent catalyst, ultrasonication, chelation, leaching, nickel recovery.

Introduction
Catalysis is the key to chemical transformations. Most industrial synthesis and processes require catalysis. Large quantities of catalysts are used in the fertilizer industry (i.e., ammonia plants), in petroleum refineries, in the chemicals sector, in various conversion processes, and in automotive catalytic converters for pollution control. The development of chemical products in advanced, industrialized societies is technically, economically and ecologically possible by means of specific catalysts. 95% of all products (volume) are synthesized by means of catalysis while 20% of the world economy depends directly or indirectly on catalysis. The importance of catalysis to chemical processes is enormous. An estimated 70% of all the chemical products (processes) are based on catalytic technologies, encompassing four major market sectors: fuel refining, polymerization, chemical production and environmental remediation. It has been estimated that more than 80% of the added value in chemical industry is based on catalysis. Approximately 80% of all catalytic processes require heterogeneous catalysts. Heterogeneous supported nickel catalysts are commonly used for various industrial processes such as hydrogenation reactions, hydro-treating, steam reforming, and methanation14 . Nickel is cheap and sufficiently active, and allows suitable catalysts to be economically produced. These catalysts deactivate over time, and when the activity of a catalyst International Science Congress Association

declines below an acceptable level, the catalyst has to be regenerated and reused. However, when online/in situ regeneration is not possible, or even after a few cycles of regeneration and reuse, the catalyst activity might decrease to very low levels, so that further regeneration might not be economically feasible. In such cases, spent catalysts tend to be discarded as solid wastes4. Ni catalysts deactivate over a lifespan of about 5-7 years because of the harsh conditions in the primary and secondary reformer5....
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