The Working State of the Barium Promoter in Ammonia Synthesis over an Active-Carbon-Supported Ruthenium Catalyst Using Barium Nitrate as the Promoter Precursor
The Working State of the Barium Promoter in Ammonia Synthesis over an Active-Carbon-Supported Ruthenium Catalyst Using Barium Nitrate as the Promoter Precursor
复制标题
DOI：
10.1006/jcat.2002.3727
复制
发表时间：
2002-10
影响因子：
7.3
通讯作者：
H. Zeng;K. Inazu;K. Aika
中科院分区：
文献类型：
--
作者：
H. Zeng;K. Inazu;K. Aika
钡促进的Ru/HTAC（氢处理活性炭）是一种很有前途的氨合成催化剂。然而，在某些条件下已经观察到失活和再生。本研究对该催化剂的活性变化进行了详细的研究。考察了反应温度、Ba（NO3）2分解温度和水蒸气压对合成氨活性的影响，并探讨了其原因。结果表明，反应条件下的助催化剂组分为BaO和Ba（OH）2，其摩尔比随温度和水蒸气压的变化而变化，服从可逆反应BaO + H2O = Ba（OH）2。得出的结论是，根据化学形式，BaO或Ba（OH）2的活性可逆地改变。与Ba（OH）2相比，BaO对Ru的促进作用更强，这是由于其对Ru的电子贡献更强。在823 K下活化的样品在588 K下的活性下降的结论是由于所包含的水蒸气导致的BaO部分的减少（10 Pa是648 K下的阈值）。在高温下，由于BaO/Ba（OH）2的热力学平衡，不会发生失活。对于碱金属，它们的氢氧化物（CsOH或KOH）在通常的氨合成条件下不会转变为活性氧化物相。2002年Elsevier Science（美国）
Barium-promoted Ru/HTAC (hydrogen-treated active carbon) is reported to be a promising ammonia catalyst. However, deactivation and regeneration have been observed under some conditions. In this study, the activity change of this catalyst was studied in detail. The effects of the reaction temperature, Ba(NO3)2 decomposition temperature, and the water vapor pressure on the ammonia-synthesis activity were investigated to elucidate the cause. It was found that the promoter components under reaction conditions were BaO and Ba(OH)2, of which the molar ratio varied with the temperature and water vapor pressure, obeying the reversible reaction BaO + H2O = Ba(OH)2. It was concluded that the activity was changed reversibly depending on the chemical form, BaO or Ba(OH)2. The stronger promoting effect of BaO vs. Ba(OH)2 was attributed to its stronger electron donation to Ru. The activity drop at 588 K of the sample activated at 823 K was concluded to be due to the decrease of the BaO portion resulting from the contained water vapor (10 Pa is the threshold at 648 K). At high temperature, deactivation can not occur because of the thermodynamic equilibrium of BaO/Ba(OH)2. For alkali metals, their hydroxides (CsOH or KOH) are not considered to turn to the active-oxide phase under the usual ammonia-synthesis conditions. c � 2002 Elsevier Science (USA)