掺钡纳米氧化镁负载钌基氨合成催化剂的还原性能及其机理  

Reduction Performance and Mechanism of Ba-Doped Nano-magnesia-Supported Ru Catalysts for Ammonia Synthesis

作　　者：霍超[1] 夏庆华[1] 骆燕[1] 杨霞珍[1] 刘化章[1] 

机构地区：[1]浙江工业大学化学工程与材料学院,浙江杭州310032

出　　处：《催化学报》2009年第6期537-542,共6页

基　　金：国家自然科学基金(20203016);浙江省自然科学基金(Y406294)

摘　　要：采用超声共沉淀法制备了掺钡纳米氧化镁负载的钌基氨合成催化剂Ru/Ba-MgO和Ru/La-Ba-MgO.催化剂中Ba是以BaCO3的形式存在于MgO载体中,使用时需还原活化为BaO.采用升温-恒温-升温阶梯式的还原程序考察了还原条件对催化剂还原性能及催化性能的影响,并利用透射电镜、X射线衍射、H2脉冲化学吸附、热重及程序升温还原等分析手段,对催化剂在氢气气氛中的还原机理进行了探讨.结果表明,催化剂中BaCO3的热稳定性及Ru粒子是否聚结长大是影响催化剂活性的主要因素.在氢气气氛中,Ru/Ba-MgO催化剂的还原过程存在偶合反应,Ru的存在可加速该偶合反应的进行,进而促进催化剂还原,提高其催化活性.Novel Ru-based catalysts were prepared using barium-doped nano-magnesia （Ba-MgO） as supports, which were originally prepared by chemical co-precipitation with ultrasonic treatment. Ba existed in the form of BaCO3 in the support, and thus Ru/Ba-MgO and Ru/La-Ba-MgO catalysts were reduced due to BaO acting as the most activate form. The effect of reduction conditions on the catalytic per- formance of the ruthenium catalysts was studied using a heating-holding-heating reduction program, and the reduction mechanism of ruthenium catalysts in hydrogen atmosphere was analyzed by transmission electron microscopy, X-ray diffraction, H2 pulse chemical adsorption, thermogravimetry, and temperature-programmed reduction. The results show that the thermal stability of BaCO3 and the agglomeration of Ru particles were the main factors for the catalytic activity of the ruthenium catalysts. Coupling reaction occurred in hydrogen atmosphere, and Ru accelerated the coupling reaction, thus promoting the reduction of the catalyst and enhancing its catalytic activity.

关 键 词：钡 纳米氧化镁 钌 负载型催化剂 氨合成 还原性能 偶合反应 

分 类 号：O643.36[理学—物理化学] TQ113.2[理学—化学]