Study On The Recovery Of Ammonia Synthesis Catalyst

Ammonia synthesis catalyst has important position in the chemical industry. The catalysts should be replaced after they are used for a period of time because the activity is decreased. In this paper, the application of the recoverd fused iron catalysts as reductant for synthesis of new catalysts was studied. The recovered catalysts was mixed with magnetite and promoter to prepare Fe₃O₄ based or FeO based catalyst by a high-temperature melting method. The activity of the as-synthesized catalyst was compared with the similar iron based catalyst which was prepared from refining iron powder. The major results are as following:1. The main phase of waste fused iron catalysts for ammonia synthesis isα-Fe. The different kind of waste catalysts has the same percent of total iron in the range of 90%～94%. The content ofα-Fe is in the range of 70%～85%. The total content of promoter of Co,K,Ca,Al is 5%～8%. All of the components are worth to be recovered2. The recovered fused iron catalysts for ammonia synthesis can be directly used as reductant to produce the Fe₃O₄ based and FeO based catalyst. When it was used to produce the Fe₃O₄ based catalyst, the mass ratio of the recovered catalyst to magnetite was 2.5%～7.0%; When it was used to produce the FeO based catalyst, the mass ratio of the recovered catalyst to magnetite was 30%～32.5%, and increase the content of iron powder can further raise the activity of the catalyst. 3. The promoter content should be considered when the recycled catalysts were used to prepare the new catalysts. It was found that the recycled catalyst can be used as materials to produce all kinds of ammonia synthesis catalysts, especially to make FeO based catalysts or the catalyst containing noble metal such as Co.4. The activity and the heat-resistant property of the catalyst which was made from recycled catalysts can reach the same level of the fresh made industrial catalyst which was prepared from new chemicals.