Kinetics of Nickel Leaching from Spent Catalyst in Nitric Acid Solution

Most industrial synthesis and processes require catalysis. Large quantities of catalysts are used in petroleum and petrochemical industry. These catalysts deactivate over time, and when the activity of a catalyst declines below an acceptable level, the catalyst has to be regenerated and reused. However, when regeneration is not possible, 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 wastes.

Recycling of spent catalysts has become an unavoidable task to reduce the catalyst waste and prevent the environmental pollution. The kinetics of spent nickel oxide catalyst (NiO/Al2O3) from Razi petrochemical company leaching in nitric acid solutions was investigated. The effects of time reaction (60-360 min), nitric acid concentration (10%, 20%, 30%) and temperature (35oC, 85oC) on the rate of nickel leaching were studied. In addition, the reaction residues at various levels of nickel extraction were examined by XRD.

The results of XRD analysis of catalysts showed that the most important elements in the catalyst were aluminum (43%) in the form of aluminum oxide and nickel (12.15%) in the form of nickel oxide. A maximum extraction of 92% was achieved at 85oC, 30% HNO3 and 360min.

Time reaction, temperature and acid concentration showed positive effect. The leaching kinetics indicates that chemical reaction at the surface of the particles is the rate-controlling process during the reaction.