摘要
在敞开体系中,以工业用水玻璃为硅源,TiCl3为钛源,十六烷基三甲基溴化铵(CTMAB)为模板剂,用H2SO4调节浆料的pH值,浆料混合物的物质的量比为n(SiO2)∶n(Na2O)∶n(CTMAB)∶n(TiCl3)∶n(H2O)=7∶2.08∶1.4∶0.14∶530时,373 K搅拌晶化一定时间,合成了Ti-MCM-41,并测试其对环己烯氧化合成环氧环己烷的催化性能。利用X射线衍射(XRD)、红外光谱(FT-IR)、紫外-可见光谱(UV-Vis)和孔结构测定对所合成的样品进行了表征,并讨论了晶化时间对分子筛晶化和催化氧化性能的影响。结果表明:在所考察的晶化时间范围内(0.5～5 d),利用敞开体系都能合成出具有良好长程有序性和结晶度的中孔分子筛Ti-MCM-41;将样品用于催化环己烯合成环氧环己烷,在晶化时间为0.5～3 d的范围内,随着晶化时间的增加,进入分子筛骨架的Ti含量也随之增加,导致介孔硅骨架趋向混乱,使分子筛骨架对称性降低,样品的孔径、比表面积和比孔容减小,但并不影响样品催化氧化活性的增加;晶化3 d后,钛含量不再增加,分子筛的孔结构和反应的转化率和选择性也几乎不再变化。
The mesoporous molecular sieve was synthesized by using silica from water glass in industry,titanium from TiCl3,H2SO4 for adjusting the pH of the slurry and CTMAB as template in an open-vessel.The mole ratio of the slurry mixture was：n（SiO2）∶n（Na2O）∶n（CTMAB）∶n（TiCl3）∶n（H2O）=7∶2.08∶1.4∶0.14∶530.The product was prepared by making the mixed slurry crystallizing at 373 K for certain time and used as catalyst in catalytic oxidation of cyclohexene to epoxy cyclohexane.The characterization of its crystallinity and framework titanium was carried out by means of X-ray diffraction（XRD）,fourier transform infrared spectrometer（FT-IR）,visiblespectroscopy（UV-Vis） and mensuration of pore structure.The effect of crystallization time on the crystal parameter and catalytic oxidation activity of the mesoporous molecular sieve was discussed.The results showed that within the limits of discussed crystallization time（0.5-5 d）,mesoporous molecular series Ti-MCM-41 with good long-range order and crystallinity could be prepared in an open system.The framework symmetry,specific surface area,pore volume and pore diameter of Ti-MCM-41 reduced gradually along with increasing crystallization time in range of 0.5-3 d and Ti content into the molecular sieve framework which leads to mesoporous silica skeleton tending to chaos,but its increasing activity wasn＇t affected in catalytic oxidation of cyclohexene to epoxy cyclohexane.After crystallizing for 3 d,titanium content no longer increased,and the pore structure of molecular sieve,conversion and selectivity of reaction almost no longer changed.
出处
《硅酸盐通报》
CAS
CSCD
北大核心
2011年第6期1399-1403,共5页
Bulletin of the Chinese Ceramic Society
关键词
敞开体系
中孔分子筛
催化氧化
晶化时间
open system
mesoporous molecular sieve
catalytic oxidation
crystallization time
