摘要
测定了不同方法改性的Y沸石样品的N_2吸附和脱附等温线,并计算了样品的微孔、大孔和二次孔的孔容和表面积,以及样品的二次孔分布,证实改性方法对样品的孔结构有显著的影响。同时,还考察了不同尺码探针分子在改性Y沸石样品上的酸催化反应活性,将所得数据与样品的酸量、酸强度和二次孔容相关联,取得了满意的结果。说明对大尺码反应分子,改性过程中生成的大孔径二次孔,对提高沸石催化剂的反应活性是有利的。
The N_2 adsorption and desorption isotherms of Y zeolites modified by hydrother-mal treatment (HUSY), H_4EDTA dealumination (HEY) and (NH_4)_2SiF_6 isomorphoussubstitution (HSY) were measured and compared with that of the original NaY andHY zeolites. The size and the shape of the hysteresis loops on the isotherms are dif-ferent, which shows that the secondary pore systems of these zeolites vary with themodification procedures. The sequence of the secondary pore volumes of the samplesis as follows HY (2. 6)<HSY (5. 7)<HSY (9. 8)<HUSY (2. 9)<HEY (4. 9)The pore distributions of the samples deduced from the theoretical treatment of theN_2 desorption isotherms according to non interconnected cylindrical pore model (BJHmodel) show that the maximum of secondary porosity of all the modified zeolite Ysamples is due to pores of ～20A radius. However, for HUSY and HEY there arepores with radii>20A and<20A as well. Reactant with various molecular sizes such as propanol, cumene aud 1,3,5-tri- tert-butylbenzene were used as probes to study the catalytic behavior of the modifiedzeolite samples. The catalytic activities of the probe molecules on the zeolite werecorrelated with the data of the acidity and the secondary pore volume. It is clearthat for larger molecules as cumene and 1,3,5-tri-tert-butylbenzene the presence ofsecondary mesopores in the zeolite structure promotes the cracking reactions considerably.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
1992年第5期595-601,共7页
Acta Physico-Chimica Sinica
基金
国家自然科学基金
关键词
Y沸石
孔结构
酸催化反应
Y zeolite
Zeolite modification
Pore structure
Secondary mesopore
Acid catalyzed reaction
