Preparation And Catalytic Properties Of Ru-based Ammonia Synthesis Catalyst

The promoted ruthenium-based catalyst has been expected to be the second-generation catalyst for ammonia synthesis. The studies on Ru-based catalyst for ammonia synthesis catalyst have many importances in catalytic sciences and technology. In spite of industrialized process, there are many fundamental konwladges on the preparation of Ru-based catalyst haven't been revealed, such as effects of promoters, supports on the catalytic activity, reaction mechanism, structure sensitivity and so on. Therefore, it is essential to study the preparation conditions of ruthenium-based catalyst for ammonia synthesis.The ruthenium catalysts supported on active carbon were prepared by impregnation method. In this thesis, the effects of impregnation, drying conditions, chemical composition of active carbon-supported catalyst and reduction conditions on the activity of Ru/AC for ammonia synthesis were studied by the employment of activity test. The experimental results are as follows:1) The effect of impregnation solvent of RuCl3 on activity was explored and the results show that the catalyst has higher activity that prepared with H₂O solvent than with acetone solvent. To reach a high activity of Ru/AC catalyst, a suitable pH of RuCl3 solution, and over 18h impregnation time should be conducted in the preparation. Furthermore, the activity of catalysts will decrease when the competitive adsorbents are added into RuCl3 solution.2) Experimental results on the effect of drying time and temperature on the activity indicate that the completely drying time is about 8¹4 h, the suitbal drying temperature is 110℃ for RuCl3 and 150℃ for Ba(NO3)2. In the preparation of Ru/AC, infrared drying method is favarable to increace the activity of catalyst.3) K and Ba are effective promoters for Ru/AC, and the catalysts promoted with bi-promoters show higher activity than promoted with single one. For Ba, K bi-promoted Ru/AC catalysts, the optimal content of Ba and K is 4 wt% and 16 wt% respectively. Moreover, the type of precursor of promoters can also affect the activity of catalysts, the orders of activity of catalyst promoted with different precursor ofpromoters are as follows: Ba (NO3)2>Ba (OH)2>BaC03>BaCl2, KNO3>KOH>K2CO3. But, the activity of catalysts will decrease with the addition of Co or Mo.4) The studies on the reduction conditions of Ba-Ru/AC indicate that a suitble reduction temperature is needed to reach a high activity of Ru catalyst. The reduction time should be above 9 h and H₂ space velocity is about 1080 h^-1.5) The activity of catalyst will increase if it was washed with NH₃.H₂O before reduction of Ba-Ru/AC .At last, it has been done to summarize the article and make a prospect for the research of Ru/AC catalysts for ammonia synthesis.