摘要
采用XRD、ESR和穆斯堡尔谱(MBS)考察了新鲜和经过丁烯还原处理的纯ZnFe_2O_4、α-FeO_3和双物相铁系催化剂的固态性质.实验发现这些丁烯氧化脱氢反应性能不同的样品,其固态性质也有较大的差异.对于双物相样品,由于物相间发生了相互作用,使其中α-Fe_2O_3和ZnFe_2O_4相的固态性质产生了不同程度的变化.与纯物相相比,双物相中α-FeO_3出现晶格畸变,ZnFe_2O_4相铁离子周围晶格氧离子的配位对称性增加,Fe^(3+)-O^(2-)键强度减弱.在无气相氧存在的反应条件下,双物相中的α-Fe_2O_3比纯α-Fe_2O_3更容易被丁烯还原.α-Fe_2O_3的作用是为氧化反应活化和传递氧离子.结合催化剂鲜品的催化反应性能,认为铁系催化剂具有双物相协同作用的机理特征.
The solid state properties of fresh and reduced α-Fe2O3, ZnFe2O4 and biphase catalyst containing ZnFe2O4and α-Fe2O3 have been examined by XRD, ESR, and Mossbauer Spectroscopy. It was found that there were great differences in the solid state properties of these catalysts which gave quite different reactivities for the oxidative dehydrogenation of butene to butadiene. For the biphase catalyst, changes of the solid state properties of eacil phase were brought about as a result of the interaction between α-Fe2O3and ZnFe2O4. In comparison with the pure phase, the lattice distortion of α-Fe2O3 occurred, while the symmetry of Fe-O octahedron of the ZnFe2O4 phase was increased and the strength of Fe3+-O2- bond became weekened. In the absence of gaseous oxygen, α-Fe2O3 in the biphase catalyst was more easily reduced by butene than the pure α-Fe2O3.α-Fe2O3in the biphase catalyst may be distributed in such sites which favorably provide the oxygen ions necessary for the oxidation reaction. With the reactivity of these catalysts taken into account a synergetically acting mechanism for the ferrite biphase catalyst is proposed as follows.
The roles of α-Fe2O3 here are basically similar to those of MoO3 in the Mo-Bi-O catalysts which were considered to be responsible for the adsorption and activation of molecular oxygen.
出处
《分子催化》
EI
CAS
CSCD
1989年第2期96-103,共8页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金资助课题
