NaY和NaM分子筛上非晶相钼(Ⅵ)性质的研究

STUDIES ON PROPERTIES OF NON-CRYSTALLINE Mo(Ⅵ) ON NaY AND NaM ZEOLITES

负载型MoO_3催化剂是含硫石油加氢脱硫的主要工业催化剂.关于MoO_3/Al_2O_3催化剂上非晶相表面层钼的配位状态和稳定性的研究曾有过报道.我们曾用XRD、激光Raman光谱、IR光谱等方法研究了MoO_3同NaY,NaM(丝光沸石)分子筛的表面相互作用,证明MoO_3能以非晶相状态分散在分子筛的孔道结构中.本文用紫外反射光谱、氨溶和TPR技术研究了NaY,NaM分子筛上分散的非晶相钼(Ⅵ)的配位状态和稳定性.

MoO3 catalysts supported on NaY and NaM zeolites have been prepared by calcination of the solid mixture. UV teflectance spectra show that the non-crystalline MoO3 dispersed on NaY and NaM can be classified as two kinds of surface species, one is Mo6+ ion in tetrahedral coordination with oxide ion and the other is in octahedral coordination. The results of the extraction of molybdenum with ammonia water show that there are also two different surface species, one is soluble and the other insoluble. After removing the soluble species, the samples are heated at certain temperature and then extracted once again in ammonia water,a lot of soluble species are reproduced. The non-crystalline MoO3 dispersed on NaM is more difficult to be reduced than that on NaY as evidenced by TPR, indicating that the interaction between non-crystalline MoO3 and framework of NaM is stronger than that of NaY.