摘要
详细研究了用Si（OCH3）4化学蒸气沉积法（C．V．D．）精细调节丝光沸石孔口尺寸的方法，制备了一系列孔口尺寸不同的SiHM沸石，并对这些样品的吸附性能、酸性质和择形催化作用进行了考察．结果表明，通过Si（OCH3）4C．V．D．方法制备的孔口尺寸各异的SiHM沸石，内表面酸性质保持不变；将其用于甲苯歧化反应，对位选择性明显增加，在相近转化率条件下，二甲苯产物中对二甲苯的摩尔分数可提高到0．40以上；但对邻二甲苯异构化反应，由于反应不是单纯由反应产物扩散控制，它们的对位选择性并无明显改善．
The fine control of the pore-opening size of HM zeolite by chemical vapor deposition of Si(OCH3)4 has been investigated. Si(OCH3)4 can be deposited by reaction with the hydroxyl groups on the zeolie. After calcination in oxygen silica is deposited on the externai surface of the zeolite and produces silica coated HM zeolite (SiHM). The SiHM samples with different amount of silica deposited have been characterized by adsorption experiments and temperature-programmed desorption of NH3. It has been found that the deposition of silica does not change the acdity of the zeolite internal surface but reduces the pore-opening size. For toluene disproportionation reaction the para-selectivity of the SiHM zeolite catalysts is increased markedly. Under the same reaction conversion the mole fraction p-xylene in the xylee mixture can be raised up to above 0.40 when using SiHM as the reaction catalyst instead of the original HM zeolite. For isomerization of o-xylene the improvement in para-selectivity has not been observed, because the reaction is not mainly controlled by the diffusion of the reaction products.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
1994年第6期514-520,共7页
Acta Physico-Chimica Sinica
基金
国家基础研究重大项目
关键词
丝光沸石
孔口
改性
甲苯
歧化
Mordenite, Pore-opening modification, Toluene disproportionation, o-xylene isomerization
