SiO_2负载的氮化钼催化剂的合成与表征  

SYNTHESIS AND CHARACTERIZATION OF SiO_2 SUPPORTED MOLYBDENUM NITRIDE HYDRODENITROGENATION CATALYSTS

作　　者：杨树武[1] 徐江[1] 阎卫宏[1] 应品良[1] 辛勤[1] 

机构地区：[1]中国科学院大连化学物理研究所催化基础国家重点实验室

出　　处：《催化学报》1998年第2期125-129,共5页

摘　　要：采用ＭｏＯ３／ＳｉＯ２和ＮＨ３程序升温反应的方法合成了一系列不同Ｍｏ含量的Ｍｏ２Ｎ／ＳｉＯ２催化剂，并采用ＸＲＤ、ＢＥＴ、ＸＰＳ、ＴＰＲ、Ｈ２ＴＰＤ和ＩＲ等手段，结合中压下吡啶加氢脱氮反应，研究了它们的表面性质和反应性能．发现Ｍｏ２Ｎ／ＳｉＯ２催化剂在反应性能和吸氢性质等方面类似于非负载的氮化钼．氮化前后，低Ｍｏ担载量催化剂的比表面积降低不大，在高Ｍｏ担载量下，由于氮化态的Ｍｏ／ＳｉＯ２催化剂上出现了粒径更小的晶相γＭｏ２Ｎ，而使其比表面积比前身态的增加．在钝化态的Ｍｏ２Ｎ／ＳｉＯ２表面，有Ｍｏ６＋、Ｍｏ４＋和Ｍｏδ＋（０＜δ＜２）三种价态的Ｍｏ存在，其中高价钼以氮氧化物或无定形的ＭｏＯ２的形式存在，它们可在高温被还原．ＮＯ和吡啶吸附的红外结果表明，在Ｍｏ２Ｎ／ＳｉＯ２催化剂上有配位不饱和的Ｍｏ中心和Ｌ酸中心存在，它们是吡啶加氢脱氮的吸氢活性中心和脱氮活性中心．A series of SiO_2 supported Mo nitrides were prepared by temperatureprogrammed reaction of supported molybdates with NH3, and they were studied by means of pyridine hydrodenitrogenation (HDN), XRD, XPS, H_2TPD, TPR and IR techniques. The results show that the hydrogen adsorption properties and activity for pyridine HDN of Mo_2N/SiO_2 catalysts are similar to those of unsupported molybdenum nitride. XRD results show that the nitride domains in the lowloading materials are X-ray amorphous while the highloading catalysts consist of γMo_2N crystallites. Three types of Mo cations, Mo^6+, Mo^4+ and Moδ+ (0<δ<2), are present on the passivated catalysts. The Mo^6+ and Mo^4+ cations, which present as oxynitrides or amorphous MoO_2, can be reduced at elevated temperatures. Also the results of NO and pyridine adsorbed on nitrided Mo/SiO_2 suggest that there are coordinatively unsaturated Mo sites with nitrogen deficiency and Lewis acid sites on the catalysts. Those active sites are contributed to the hydrogenation and CN bond cleavage in pyridine HDN reaction.

关 键 词：氮化钼 二氧化硅 负载型 催化剂 吡啶 加氢 脱氮 

分 类 号：O643.38[理学—物理化学] O626.321[理学—化学]