铝基载氮体化学链合成氨是一种具有良好发展潜力的新型合成氨技术,在高效合成氨的同时实现煤炭等碳基能源的清洁利用。然而,在氮化反应温度下铝基载氮体不可避免会转化为活性较低的α-Al2O3,降低氨合成效率。为解决这一问题,利用共沉淀法制备了一系列Cr掺杂的CA-x%(x=0、2.5、5.0、7.5、10.0)载氮体样品用于化学链合成氨反应特性研究。XRD、XPS表明,Cr原子均匀掺杂进入Al2O3晶格内部并提高了其氧活性。将5种载氮体样品用于氮化-氨化反应试验,结果表明CA-5%载氮体的合成氨性能最佳,其NH3收集量约为未掺杂时的3倍,Cr掺杂同时促进了氮化和氨化反应的进行。利用MaterialStudio软件建立载氮体的氮化反应模型,DFT计算结果表明Cr原子的掺杂可显著降低氮化反应过程中CO的生成以及N2解离吸附过程的能垒,Cr掺杂后Al2O3的晶格氧稳定性降低,氧原子更易从载氮体表面解离且更易与N2反应生成氮化铝。最后选用CA-5%载氮体进行10次氮化-氨化反应试验验证了Cr掺杂铝基载氮体的循环稳定性。

Aluminum-based nitrogen carriers for chemical looping ammonia generation represent a novel technique with promising potentialfor the efficient production of ammonia and the clean utilization of carbon-based energy sources like coal. However, at the temperaturesrequisite for nitridation reactions, the aluminum-based nitrogen carriers inevitably transform into α-Al2O3, which possesses lower activityand adversely affects the efficiency of ammonia synthesis. To address this issue, a series of Cr-doped CA-x% (x = 0, 2.5, 5.0, 7.5,10.0) nitrogen carrier samples were prepared using the co-precipitation method for the study of their characteristics in chemical loopingammonia synthesis reactions. XRD and XPS analyses confirm that Cr atoms are uniformly doped into the Al2O3 lattice, enhancing its oxygen activity. When the five nitrogen carrier samples were tested in nitridation-ammoniation reactions, the CA-5% sample demonstratedsuperior ammonia synthesis performance, with an ammonia yield approximately 3 times higher than that of the undoped counterpart. Theinclusion of Cr also facilitates both nitridation and ammoniation reactions. Utilizing Material Studio software to construct a model for the nitridation reaction of the nitrogen carrier, analysis of the computational results reveal that Cr doping significantly reduces the formation of COduring the nitridation process and the energy barrier for the dissociative adsorption of N2. After Cr incorporation, the stability of lattice oxygen in Al2O3 decreases, rendering oxygen atoms more prone to dissociate from the surface of the nitrogen carrier and to react with N2 toform aluminum nitride. Finally, repeated nitridation-ammoniation reaction experiments conducted with CA- 5% nitrogen carrier affirmthe cyclic stability of Cr-doped aluminum-based nitrogen carriers

0 引言

1 试验

   1.1 载氮体的制备

   1.2 试验装置及方法

   1.3 密度泛函(DFT)计算方法

2 结果与讨论

   2.1 表征分析

   2.2 载氮体氮化-氨化反应活性

   2.3 载氮体表面氮化过程的DFT计算

   2.4 Cr掺杂载氮体的循环反应性能

3 结论