Pilot-scale extraction of zinc from the spent catalyst of vinyl acetate synthesis by microwave irradiation

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• 作者：Wei Li ; Jinghui Peng ; Libo Zhang ; Zebiao Zhang ; Lei Li ; Shimin Zhang ; Shenghui Guo
• 关键词：Spent catalyst ; Microwave irradiation ; Leaching ; Vinyl acetate
• 刊名：Hydrometallurgy
• 出版年：2008
• 出版时间：May 2008
• 年：2008
• 卷：92
• 期：1-2
• 页码：79-85
• 全文大小：872 K

文摘

A pilot-scale experiment of extracting zinc from spent catalyst of vinyl acetate synthesis by pretreatment using microwave irradiation was investigated. A variety of factors that affect zinc leaching were evaluated systematically. The experiment results indicated that the pretreatment with microwave irradiation could improve the zinc leaching rate greatly. Taking into consideration the experimental results and the industry production practice, the optimum conditions were obtained as follows: the temperature of pretreatment with microwave irradiation was 950 °C; the leaching agent was a mixture of ammonium bicarbonate, ammonia and water; the dose of leaching agent was 2.5 times more than the theoretical dose; the ratio of liquid to solid was 2:1; leaching time at room temperature was 3 h; the residue was washed 4 times. The average zinc extraction was 93.45 % under the optimal conditions. The surface morphology and compositions of spent catalyst before and after microwave irradiation, and before and after being leached using the leaching agents were observed and characterized by SEM and XRD techniques. The results showed that the spent catalyst untreated by microwave irradiation was mainly composed of zinc acetate and activated carbon, but that of being treated by microwave irradiation was mainly composed of carbon and zinc oxide, and furthermore the pores of activated carbon were opened. The zinc oxide was adsorbed onto the surface and pores of spent catalyst, so the leaching agents could react with zinc oxide effectively. The spent catalyst after being leached was mainly composed of carbon; indicating the extraction of zinc from spent catalyst was very effective.