A301型氨合成催化剂物理化学性能

PHYSICO-CHEMICAL CHARACTERISTICS OF A301 CATALYST FOR AMMONIA SYNTHESIS

系统研究了A301型氨合成催化剂还原前、后的物化性能和宏观结构,并与传统熔铁催化剂作了比较.研究结果表明,催化剂的比表面积和孔结构是在还原脱氧过程中产生的,还原前的催化剂可视为无孔隙的致密固体.A301的比表面积和α-Fe晶粒度与A110-2相同,但α-Fe表面积和碱表面积比A110-2小,而酸表面积比A110-2大.A301的堆密度和颗粒密度均比A110-2大,但真密度比A110-2小.A301催化剂的孔容积、孔隙率和孔径都比传统催化剂小,这与Nielsen A的研究结果不一致.Fe_(1-x)O对基的A301催化剂活性的提高,不是因为它的比表面积或孔径增大,也不是因为它的含铁量增加,而是由于Fe_(1-x)O还原得到的α-Fe的表面性质(例如酸表面积增大)和表面结构发生变化,使比活性提高之故.

The chemical composition, crystal structure pre-reduction, and post - reduction density and the important characteristics such as surface area, pore volume, porosity, mean pore radius and pore distribution of A301 catalyst have been studied systematically. The results show that the catalyst specific area and its pore structure is generated during the reduction process and the catalyst before reduction can be regarded as a compact solid with little pore. The BET surface area and a - Fe crystalline size of the A301 are comparable with the traditional catalyst A110-2. A301' s α- Fe and alkali surface area aresmaller than A110 - 2, but its acid surface area is larger than A110-2. Its bulk density and particle density are larger than A110 - 2 too, but its true density is not. The pore volume, porosity and pore radius of A301 are smaller than the traditional catalyst. This is inconsistent with the results reported by Nielsen A. The increase of activity of the Fe1-x O based A301 catalyst is due to the change of the surface properties ( such as enlargement of the acid surface area ) and surface structure of the α- Fe reduced fromFe1-x O, rather than the enlargement of the BET specific area , pore radius or increase of Fe content .