New Ammonia Synthesis Catalyst And Catalytic Properties

This thesis reports the preparation and the activity of the ruthenium catalysts for ammonia synthesis with three kinds of supports, such as alumina, active carbon and spinel Fe304. The effects of supports, promoters and preparation conditions on the activity of ammonia synthesis have been investigated. The supports and the catalysts were characterized by element analysis, physical adsorption, chemical adsorption and SEM respectively. When alumina is used as support to prepare the ruthenium catalyst, it is found that Ru dispersion of catalyst is not completely determined by specific surface area of alumina support. The pore volume and pore size of supports would influence metal dispersion. The activity of ammonia synthesis increases with the increase of the reduction temperature because high temperature can remove chlorine ions from surface of catalysts. When the sample of Ru/A1203 was washed with dilute ammonia solution and deionized water, the chlorine ions would be removed, and the activity of catalyst would increase obviously. When ruthenium catalysts for ammonia synthesis are supported on active carbon, high degree purity and proper specific surface area of the carbon support are beneficial to the high activity for ammonia synthesis. With the Ru loading increasing, the activity of ammonia synthesis is increased. For double promoted system, it is found that the catalysts are more active when the promoters are impregnated step by step than that the promoters are co-impregnated. The activity of ruthenium catalyst supported on active carbon is high, but it is suitable for the catalyst to work under the low temperature. The ruthenium catalyst for ammonia synthesis supported on spinel Fe304 is studied. Among the promoters used, i.e., alkali metal, alkali earth metal and rare earth metal elements, the Cs compound is found to be more effective than the others. The activityof catalyst promoted by alkali metal compound increased with the content of promoter increasing. Moreover the different precursor of promoters affects the activity of catalysts.