CrMCM-41分子筛的合成与表征

直接合成了含铬 MCM- 4 1中孔 (mesoporous)分子筛 ;通过 XRD、骨架 IR、ESR、紫外漫反射(DRS)、2 9Si MASNMR等测试 ,表明铬处在分子筛骨架上 ,同时也存在非骨架铬。骨架红外光谱中除发现铬分子筛的特征峰 690 cm-1 外 ,还发现被归属于 O3 Si- O- T振动的吸收峰 960 cm-1 ;ESR中观察到 g=2 .4处有信号 ,可能与骨架铬直接有关 ;固体魔角核磁 2 9Si谱也进一步证实骨架铬的存在。同时对 Cr MCM- 4 1分子筛的热稳定性、吸附量和酸性进行了考察。

SYNTHESIS AND CHARACTERIZATION OF Cr MCM-41 MOLECULAR SIEVE

A mesoporous crystalline molecular sieve Cr MCM- 4 1has been synthesized directly by the hydrothermal method.By the characterizations with XRD,framework IR,DR UV- VIS, 2 9Si MAS NMR techniques,it is confirmed that small chromium is incorporated into frame- work positions,and extra- framework chromium is also presence. On the framework IR spec- trum,except of the absorption bands6 90 cm-1 ,characteristic of the chromium silicate,an absorption band at96 0 cm-1 which isassigned to the streching vibration of O3 Si- O- T linkages is observed. The signal of g=2 .4 in the ESR spectra isalso observed,which could be direct- edly correspendent to the framework Cr.The solid- state MAS NMR spectrum of sample provided furtherevidence of the presence of the framework Crspecies. The adsorption capac- ity,acidity,and thermal stability of the Cr MCM- 4 1samples have also been elucidated.