摘要
本文利用ＦＴ－ＩＲ，ＴＰＤ等技术考察了合成在ＮａＹ分子筛笼内的铂羰基簇合物［Ｐｔ_３（ＣＯ）_６］_ｎ^（２－）（ｎ＝３，４）和铑羰基簇合物Ｒｈ_６（ＣＯ）_（１６）的热稳定性．［Ｐｔ_（１２）（ＣＯ）_（２４）］^（２－）／ＮａＹ的羰基红外谱带在真空中升温至３４３Ｋ基本没有变化，表现出了比ＳｉＯ_２外表面负载的同种羰基簇合物好的热稳定性；部分脱羰基后的残存的线式羰基在高温下才能脱附．而对Ｒｈ_６（ＣＯ）_（１６）／ＮａＹ，随脱羰基过程的进行，铑羰基簇合物首先生成Ｒｈ~＋（ＣＯ）_２然后脱附．ＣＯ的ＴＰＤ给出与铂及铑羰基簇化合物化学计量相一致的ＣＯ及ＣＯ_２脱附量，从侧面支持了笼内金属羰基簇合物的归属．ＴＰＤ过程中的ＣＯ_２主要来源于ＣＯ与表面ＯＨ或吸附Ｈ_２Ｏ的作用，只有少量的ＣＯ_２来源于ＣＯ歧化反应．
The thermal stabilities of intrazeolite metal carbonyl clusters (n=3, 4)and Rh_6(CO)_(16) were studied with FT-IR and TPD techniques.The characteristic CO bands of [Pt_(12)(CO)_(24)]￣(2-)/NaY didn't change up to 363 K in vacuo,revealing the higher stability of intrazeolite clusters compared with those on SiO_2 surface,The residual carbonyls after partial decarbonylation desorbed only at high temperatures,For the decarbonylation of Rh_6(CO)_(16)/NaY,Rh￣+(CO)2 was formed first followed with CO desorption from Rh￣+(CO)_2 at higher temperatures.CO TPD results gave(CO+CO_2)/M ratios similar to the stochiometry in the metal clusters,supporting the assignments of intrazeolite metal carbonyl clusters.CO_2 desorbed during CO TPD is mainly due to the reaction between CO and surface water or hydroxyls.
出处
《分子催化》
EI
CAS
CSCD
1994年第4期257-262,共6页
Journal of Molecular Catalysis(China)
关键词
分子筛
铂
铑
羰基簇合物
热稳定性
TPD
Zeolites,Platinum,Rhodium,Carbonyl clusters,Thermal stability,TPD.
