مطالعه سينتيك فروشويي نيكل از كاتاليست هاي مستعمل با اسيد نيتريك

Kinetics of Nickel Leaching from Spent Catalyst in Nitric Acid Solution

زﻣﯿﻨﻪ و ﻫﺪف : ﮐﺎﺗﺎﻟﯿﺴﺖ ﻫﺎ در ﺻﻨﺎﯾﻊ ﻣﺨﺘﻠﻒ از ﺟﻤﻠﻪ ﭘﺘﺮوﺷﯿﻤﯽ ﻫﺎ و ﺻﻨﻌﺖ ﻧﻔﺖ ﮐﺎرﺑﺮد ﻓﺮاوان دارد. اﯾﻦ ﮐﺎﺗﺎﻟﯿﺴﺖ ﻫﺎ ﺑﺎ ﮔﺬﺷﺖ زﻣـﺎن و ﭘﺲ از ﻣﺼﺮف، ﻗﺎﺑﻠﯿﺖ اﺣﯿﺎء و اﺳﺘﻔﺎده ﻣﺠﺪد را دارا ﻫﺴﺘﻨﺪ. در ﺻﻮرﺗﯽ ﮐﻪ اﺣﯿﺎء و اﺳﺘﻔﺎده ﻣﺠﺪد از آن اﻣﮑﺎن ﭘﺬﯾﺮ و اﻗﺘﺼـﺎدي ﻧﺒﺎﺷـﺪ، ﮐﺎﺗﺎﻟﯿﺴﺖ ﻣﺴﺘﻌﻤﻞ ﺑﻪ ﻋﻨﻮان ﭘﺴﻤﺎﻧﺪ ﻣﻄﺮح ﺷﺪه و ﺑﺎزﯾﺎﺑﯽ آن ﺿﻤﻦ ﮐﺎﻫﺶ ﺗﻮﻟﯿﺪ ﭘﺴﻤﺎﻧﺪ از آﻟﻮدﮔﯽ ﻣﺤﯿﻂ زﯾﺴﺖ ﺟﻠﻮﮔﯿﺮي ﻣـﯽ ﮐﻨـﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﺿﻤﻦ ارزﯾﺎﺑﯽ اﺛﺮ ﭘﺎراﻣﺘﺮﻫﺎي ﻣﻮﺛﺮ ﺑﺮ واﮐﻨﺶ ﻓﺮوﺷﻮﯾﯽ ﻧﯿﮑﻞ از ﮐﺎﺗﺎﻟﯿﺴﺖ ﻣﺴﺘﻌﻤﻞ NiO-Al2O3 ﻣﻮرد اﺳﺘﻔﺎده در ﭘﺘﺮوﺷﯿﻤﯽ رازي، ﺳﯿﻨﺘﯿﮏ واﮐﻨﺶ ﻧﯿﺰ ﺑﺮرﺳﯽ ﺷﺪ. روش ﺑﺮرﺳﯽ: در اﯾﻦ ﻣﻄﺎﻟﻌﻪ اﺛﺮ ﻣﺜﺒﺖ ﻫﺮ ﺳﻪ ﭘﺎراﻣﺘﺮ زﻣﺎن واﮐﻨﺶ، دﻣﺎ و ﻏﻠﻈﺖ اﺳﯿﺪ ﻧﯿﺘﺮﯾﮏ ﺑـﺮ ﻣﯿـﺰان اﺳـﺘﺨﺮاج ﻧﯿﮑـﻞ از ﮐﺎﺗﺎﻟﯿﺴـﺖ ﻣﺴﺘﻌﻤﻞ ﻣﺸﺎﻫﺪه ﺷﺪ و ﻣﻄﺎﻟﻌﻪ ﺳﻨﺘﯿﮏ، واﮐﻨﺶ ﺷﯿﻤﯿﺎﯾﯽ ﺳﻄﺢ ذرات را ﺑﻪ ﻋﻨﻮان ﻋﺎﻣﻞ اﺻﻠﯽ ﮐﻨﺘﺮل ﺳﺮﻋﺖ واﮐﻨﺶ ﺗﻌﯿﯿﻦ ﮐﺮد. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از XRD ﮐﺎﺗﺎﻟﯿﺴﺖ ﻣﺴﺘﻌﻤﻞ ﻣﯿﺰان اﮐﺴﯿﺪ آﻟﻮﻣﯿﻨﯿﻮم را 43% و اﮐﺴﯿﺪ ﻧﯿﮑﻞ را 12/5% ﻧﺸـﺎن داد و ﻋـﺪم واﮐـﻨﺶ اﮐﺴﯿﺪآﻟﻮﻣﯿﻨﯿﻮم ﺑﺎ اﺳﯿﺪ ﻧﯿﺘﺮﯾﮏ را ﻧﯿﺰ ﺛﺎﺑﺖ ﻧﻤﻮد. ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: اﺛﺮ ﭘﺎراﻣﺘﺮﻫﺎي ﻣﻮﺛﺮ ﺑﺮ ﻓﺮوﺷﻮﯾﯽ ﻧﯿﮑﻞ ﻧﻈﯿﺮ زﻣﺎن واﮐﻨﺶ )360- 60 دﻗﯿﻘﻪ(، دﻣﺎ )C, 85 °C° 35( و ﻏﻠﻈﺖ اﺳـﯿﺪ ﻧﯿﺘﺮﯾﮏ )30%، 20%، 10%( ﺗﻌﯿﯿﻦ ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از اﺳﺘﺨﺮاج ﻧﯿﮑﻞ ﻧﺸﺎن داد ﮐﻪ ﺣﺪاﮐﺜﺮ ﻣﯿﺰان اﺳﺘﺨﺮاج ﻧﯿﮑﻞ ﺗﺤﺖ ﺷـﺮاﯾﻂ دﻣـﺎﯾﯽ 360 دﻗﯿﻘﻪ، ﻏﻠﻈﺖ اﺳﯿﺪ ﻧﯿﺘﺮﯾﮏ 30% و دﻣﺎي C° 85 اﺗﻔﺎق ﻣﯽ اﻓﺘﺪ.

Background and Objective: 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. Method: 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. Findings: 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. Discussion and Conclusions: 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.