载体对负载型过渡金属氮化物催化氨分解性能的影响

采用等体积浸渍法结合NH3程序升温氮化制备出一系列负载型金属Co、Mo氮化物催化剂。并利用XRD、TPD-MS和H2-TPR及氨分解活性测试等手段，考察了载体［Mg(Al)O、MgO和γ-Al₂O₃］对负载型金属氮化物的表面形态及组成的影响。结果表明，（1） 负载催化剂的氨分解速率远远高于非负载的催化剂；（2） 氮的脱附峰可以归为以下三类：a.吸附态的NHx分解；b.氮化物结构转变；c. β-Mo₂N_0.78和Co₂Mo₃Nx 还原成Co和Mo金属；（3） 载体表面的酸碱性和孔结构对其负载的金属氮化物的催化活性和表面形态及化学组成有重要的影响，镁铝复合氧化物MgAlO［n(Al)∶n(Mg)=1∶3］为载体的钴钼双金属氮化物对于氨分解反应具有最好的催化活性。

Effects of supports on ammonia decomposition activity of bimetallic transition metal nitrides

SEveral bimetallic nitrides were prepared by temperature-programmed reaction of the corresponding oxides precursor with NH3 flow. XRD, TPD-MS, H2-TPR and test of the activity for ammonia decomposition were used to investigate the effects of supports on the surface morphology and chemical composition of the supported metallic nitrides. It was found that: (1) ammonia decomposition activity of supported metallic nitrides was much higher than that of unsupported metallic nitrides; (2) The N₂-TPD peaks were ascribed to decomposition of absorbed NHx species, structural change of nitrides and partial reduction from β-Mo₂N_0.78 and Co₂Mo₃Nx to metal Co and Mo; (3) activity, surface morphology and composition of the supported nitrides were significantly dependent upon surface acidity/alkalinity and pore structure of the support, and nitride supported on MgAlO［n(Al)∶n(Mg)=1∶3］showed the optimum activity for ammonia decomposition.