稀土改性Y型分子筛的酸性研究

摘要

用稀土对NaY型分子筛进行改性,考察分子筛改性前后酸性质以及Al原子配位状态的变化.研究结果表明:稀土改性NaY分子筛后,酸密度、总B酸量和强B酸量、总L酸量和强L酸量均增加;但当稀土超过一定量后,酸密度、B酸量和L酸量又会下降.因此,稀土含量可根据对酸性的要求调节;四配位、五配位和六配位的Al原子影响B酸的产生,低配位的非骨架Al原子影响L酸的产生.%The acidic properties and the coordination of aluminum in zeolite Y modified by rare earth exchange were studied. Results show that after rare earth exchange, the acidic properties of zeolite Y change significantly,the acid density, the total amount of Br(o)nsted(B) acid and the amount of strong B acid, as well as the total amount of Lewis(L) acid and the amount of strong L add all increase. However, when the degree of rare earth exchange exceeds a certain amount, the acid density, the amount of B acid and L acid decrease, thus the acidic properties of zeolite Y could be adjusted by rare earth exchange. Results also show that the formation of B acid site is affected by the tetra-coordinated, penta-coordinated and hexa-coordinated aluminum, and L acid site is affected by the non-framework aluminum in lower coordination.