摘要
合成了H_4SiMo_(12)(?)nW_nO_(40)(n=0,6,12)的SiO_2负载样品,XRD、TEM、LRS测定结果表明杂多酸在低负载量时在载体表面高度分散,但仍保持Keggin单元结构,然后随负载量的增加逐渐聚集成较大的晶粒。XPS结果显示杂多酸同载体之间有一定的相互作用,但负载化对杂多酸的热稳定性影响不大。负载化使杂多酸在载体表面分散而提高其对异丙醇脱水的催化能力,当杂多酸在载体表面聚集形成较大晶粒后活性不再上升。吡啶吸附红外光谱结果显示负载样品同时具有B酸和L酸中心,异丙醇脱水催化反应发生在B酸位上。
Supported heteropolyacids H4SiMo12.n WnO40/SiO2, (n = 0, 6, 12) have been prepared and characterized. The results of XRD, TEM, LRS show that heteropolyacids tend to be highly dispersed at the surface of SiO2 while retaining the Keggin Units when the supported amount is low. They gradually accumulate and form larger crystalline particles with increasing the amount supported. The XPS results suggest that there is some kind of interaction existing between heteropolyacids and support.The thermal stabilities of heteropolyacids are not influenced by the support, but their acid catalytic activity for 2-propanol dehydration is increased when heteropolyacids are highly dispersed on the surface of SiO2. When the supported amount reaches a certain level, the catalytic activities will no longer increase. IR results of pyridine adsorption reveal that supported samples have both Bronsted and Lewis acid centers, and 2-propanol dehydration is a Bronsted acid catalysed reaction.
出处
《分子催化》
EI
CAS
CSCD
1990年第1期13-20,共8页
Journal of Molecular Catalysis(China)
基金
石油化工科学研究院资助
