摘要
采用TPR-MS技术研究了Ba(NO3)2/AC(AC:活性炭)、KNO3/AC和Ba-Ru-KNO3/AC在H2中的还原情况。实验结果表明,KNO3/AC和Ba(NO3)2/AC分别在400℃和350℃发生还原,生成N2O和N2两种较高价态的还原产物,且助剂的还原不完全。与Ba(NO3)2/AC和KNO3/AC相比,Ba-Ru-KNO3/AC催化剂在加入活性物质钌的情况下,不仅使助剂的还原温度显著降低,而且反应的主要产物也发生了变化,大部分的硝酸根离子被彻底还原成NH3。这可能是由于Ru的存在使氢发生溢流现象,氢活化能力增强,使催化剂表面富含还原所需活化氢物种,导致助剂在较低的温度下被彻底还原。由于Ru的催化作用,载体的甲烷化温度明显降低。提高还原温度虽然对催化剂中氯离子的脱除有利,但同时也会使钌晶粒长大烧结,抑制氨合成的活性。实验结果表明,在制备钌催化剂时,还原除氯的适宜温度为200℃左右。
The hydrogen reduction processes of Ba（NO3）2/AC, KNO3/AC and Ba-Ru-KNO3/AC samples were studied by TPR-MS technology. It was found that KNO3/AC and Ba（NO3）2/AC were reduced at 400℃ and 350℃ respectively. Furthermore, the samples were not reduced completely, and formed higher valence （state） nitrogen compound N2 and N2O （for their reduction products）. Compared to Ba （NO3）2/AC and KNO3/AC, Ba-Ru-KNO3/AC sample was reduced more completely and thoroughly at approximately 200℃ in hydrogen flow, and formed a main reduction product NH3. The role of Ru can be suggested to activate hydrogen and form hydrogen spillover on carbon support. Ru atom could facilitate the ability of formation of active hydrogen atom for reduction and hydrogen spiUover which lead to low reduction temperature of promoter. However, the presence of Ru also promoted the methanation of carbon support. More chloride ion can be removed at higher temperature, but it is unfavorable to catalyst activity because of support methanation and Ru particle sintering at high temperature. The results showed that the optimal reduction temperature was about 200 ℃ .
出处
《化学通报》
CAS
CSCD
北大核心
2007年第6期439-444,共6页
Chemistry
基金
中国石油化工股份有限公司(499051)
国家自然科学基金(20203016)资助项目
