Structure Control And Its Performance Based Or Ru/AC, Co/AC Catalyst For Ammonia Synthesis

Ruthenium catalyst is recognized the second generation of ammonia synthesis catalyst, and the characteristics of high activity at low temperature and low pressure is considered a major breakthrough in the history of the development of synthetic ammonia industry. In order to further improve the cost performance and stability of ruthenium catalyst, this article improves the carrier, Ru precursor and preparation method of ruthenium catalysts based on the graphitized carbon carrier. It uses the self-made water-soluble chlorine-free ruthenium complex as the precursor to prepare the catalyst by co-impregnation method for preparing more cost-effective and more excellent thermal stability catalyst. It took advantage of a series of methods of CO chemisorption, H2-TPR, H2-TPD, N2-TPD, N2 adsorption, MS, FT-IR, XPS, GC to discuss the different Ru precursor structures and its influence on the properties of Ru/AC ammonia synthesis catalyst, the effect of the different additives types, content and the ratio for the Ru/AC catalyst activity and stability. This paper also studies the citric acid affecting Co dispersion and catalytic performance as a chelating agent. This article has achieved the following significant results:The water-soluble chlorine-free Ru precursor synthesized from K2RuO4 and hydroxyl organic compounds, it used to prepare the Ru/AC catalyst by co-impregnation method. Research shows that the application of water-soluble chlorine-free precursor, compared with other precursor, not only ensures the high catalytic activity, but also reduces the cost of preparation by simplifying the preparation process, and shortening the preparation time. Water-soluble chlorine-free Ru precursor as ammonia synthesis catalyst precursor had not been reported in the literature. Hence, it is expected to become a new precursor for ruthenium catalyst. Different ligands, the size of ligand molecular and solubility could affect the catalytic properties. The catalyst based on the ruthenium complex precursor synthesized of small molecular weight, water-soluble ligand has better catalytic activity.The influence of different content of Ru and Ba on the performance of Ru/AC catalyst was investigated by co-impregnation method. For the catalysts with different Ru content, the K-Ba-Ru/AC catalyst prepared with 8 wt% Ba and 16 wt% KOH has highest ammonia synthesis activity, but the catalysts with 10 wt% Ba both has high activity and stability.Investigation was treated on the stability of ru(?) catalyst for ammonia synthesis. The Ru/AC catalyst doped with Al, alkaline earth metal and rare earth metal for ammonia synthesis had obvious influence on the activity and thermal stability. Ba promoter dopped with La has a good synergistic effect on delay of the methanation reaction and the service life of the catalyst. Effectively La doping has not bad influence for the activity of ammonia synthesis.The effects of citric acid on the catalytic performance of Ba-Co/AC catalyst for ammonia synthesis were studied. When loading of citric acid is 12 wt%, the activity of the catalyst is the highest. The key reason for catalyst activity increased is the greatly increased dispersion of cobalt metal.