摘要
本文研究了Sn-Mo混合氧化物催化剂的活性与焙烧温度的关系。对Sn_(0.975)Mo_(0.025)催化剂进行了不同焙烧温度的ESR研究,跟踪观察了Sn-Mo混合氧化物固溶体随焙烧温度变化的形成过程。结果表明,焙烧温度在100—300℃之间,钼以钼酸铵微晶高度分散在氧化锡表面;300—550℃时,随温度升高钼逐渐向氧化锡体相扩散;550℃时可能形成嵌入型固溶体,催化活性最好;600℃开始形成置换型固溶体,Mo以Mo^(5+)形式取代氧化锡晶格中的Sn^(4+),此时ESR信号gzz>gxx>gyy。
The correlation between the activity and the structure of Sn-Mo mixed oxide catalysts calcined at different temperatures has been investigated by using ESR. The catalysts Sn0.975Mo0.025 calcined at different temperatures were also studied by ESR in order to obtain the information about the superhyperfine structure. The process of the Sn-Mo mixed oxide solid solution formation was observed. The results showed that molybdenum highly dispersed as micro-crystal of ammonium paramolybdate on the surface of stannic oxide at temperature from 100 to 300℃. Molybdenum diffused into the SnO2 bulk as the temperature increased gradually from 350 to 550℃. The interstitial solid solution of the best catalytic activity formed at 550℃, Mo5+ ions replaced some SiT ions in SnO2 crysial lattice,and the anisotropy g values were
