大孔径Cr-MCM-48合成及其催化性能  

Direct synthesis of Cr-MCM-48-like large pore mesoporous silica and its catalytic properties

作　　者：汪磊[1] 王灵芝[1] 陈国栋[1] 张金龙[1] 

机构地区：[1]华东理工大学先进材料实验室精细化工研究所,上海200237

出　　处：《中国科技论文在线》2009年第3期232-238,共7页

基　　金：高等学校博士学科点专项科研基金项目(20070251006)

摘　　要：用三嵌段共聚物P123(EO20PO70EO20)作为模板剂,正丁醇作助剂,通过pH值调节合成出了铬掺杂的大孔径三维立方介孔二氧化硅。反应体系中,Si/Cr摩尔比为10～80.产物的真实Cr含量用原子吸收光谱(ICP-AES)测得;通过X射线衍射(XRD)、透射电子显微镜(TEM)、N2吸附脱附表征表明,产物具有规整的三维立方介孔结构。紫外可见吸收光谱、电子顺磁共振表征显示当掺杂量较小时(Si/Cr摩尔比大于30),铬的存在形态为Cr(VI)和Cr(V),当掺杂量较大时,产生Cr(III).用产物催化氧化环己烷,当用过氧化氢(H2O2)作为氧化剂时,环己烷的最大转化率达到53%;用叔丁基过氧化氢作氧化剂时,环己酮的转化率为86%.Chromium substituted MCM-48-like large pore mesoporous silica with average pore size up to 10 nm was directly synthesized by using P123（EO20PO70EO20） as template,n-butanol as assistant and chromium nitrate as chromium source.The Cr species were doped by simply adjusting the pH value of the synthesis system with ammonia from strong acid to nearly neutral after crystallization for 24 h.The Si/Cr ratios in the initial gel ranged from 10 to 80 and the actual weight percentage of Cr content was analyzed by ICP.X-ray diffraction pattern（XRD）,transmission electron microscopy（TEM） and N2 adsorption-desorption isotherm were employed to investigate the pore structure properties of these materials.The results indicate the pH adjusting method is an efficient way to incorporate large amount of chromium into the large pore Ia3d mesostructure.UV-vis and ESR spectra reveal that at lower Cr content（Si/Cr30）,only Cr（VI） and Cr（V） species exist in the mesoporous framework,and at higher Cr content,the Cr（III） species appeares.The catalysis ability of Cr-doped MCM-48-like large mesoporous silica for the oxidation of cyclohexane by hydroperoxide（H2O2） was also investigated and the conversion percent was high to 53%.The experiment using tert-butylhydroperoxide（TBHP） as oxidatnt got 86% cyclohexnone selectivity.

关 键 词：MCM-48 大孔径 铬掺杂 氧化环己烷 

分 类 号：O643.36[理学—物理化学]