高等学校化学学报 ›› 1982, Vol. 3 ›› Issue (2): 162-168.
• 论文 •
忻新泉, 朱龙根, 孟庆金, 张雪琴, 吴沛成, 戴安邦
Xin Xinquan, Zhu Longgen, Meng Qingjin, Zhang Xueqin, Wu Peicheng, Dai Anbang
Abstract: This report points out that chloride ion is a poison for iron catalyst of ammonia synthesis promoted by alkali metal. Results of the experiment on adding KCl to the system Fe-AC (active carbon)-Kshowed a very marked decrease in catalytic activity (Fig. la), while the addition of KCl to the system, Ru-AC-K, activity decreases much less (Fig. lb), indicating that chloride ion is a poison for iron catalyst but has little effect on ruthenum catalyst for ammonia synthesis.Gas chromotographic study on Fe2(C2O4) S-AC and Fe2(C2O4)3-KCl-AC systems showed that in hydrogen atmosphere the decomposition of the iron salt took place at different temperatures. In the system that contained KCl, the decomposition products COand CO3 appeared at a higher temperature (Fig. 2a, 2b). In hydrogen atmosphere, the reduction of FeOfrom pure Fe2(C3O4)3 crystals was almost completed at 300-420℃, but FeOof the Fe2(C3O4)3-AC system was reduced only slightly even at 500℃. Under the same condition, FeOfrom the Fe2(C3O4)3-AC-KCl system was reduced much more as indicated by the amount of water evolved (Fig. 2c). It was therfore postulated that the presence of KCl lowered the degree of dispersion of FeO and made it more easily reduced to form large particles of a-iron of low or no catalytic activity.X-ray diffraction study of the catalysts by the powder method revealed that the product of the decomposition of Fe2(C3O4)3-KCl-ACgave the characteristic spectrum of a-iron(Fig. 3) while that of Fe2(C3O4)3-ACgave no spectrum. It was also found, by comparing the Mossbauer spectra of the two systems, that in the catalyst from Fe2(C2O4)3-KCl-ACsystem the spectral lines of the fine particulate a-iron in paramagnetic region which corresponded to high catalytic activity disappeared.In conclusion, it is considered probable that the poisonous effect of chloride ion is due to the agglomeration of the superfine particles of a-iron which are the active centers of the catalyst for ammonia synthesis and ruthenum catalyst is much less sensitive to this agglomeration effect.
忻新泉, 朱龙根, 孟庆金, 张雪琴, 吴沛成, 戴安邦. 碱金属助催合成氨铁催化剂的研究(Ⅴ)——氯离子的效应[J]. 高等学校化学学报, 1982, 3(2): 162-168.
Xin Xinquan, Zhu Longgen, Meng Qingjin, Zhang Xueqin, Wu Peicheng, Dai Anbang. STUDIES ON ALKALI METAL PROMOTED IRON CATALYST FOR AMMONIA SYNTHESIS (V)——EFFECT OF CHLORIDE ION[J]. Chemical Journal of Chinese Universities, 1982, 3(2): 162-168.