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用EPR实验证实直接法合成分子筛原粉经酸交换(HZSM-5),150℃烘干(不焙烧)样品骨架存在L酸中心。随着焙烧温度升高,L酸中心数量增长,且在600%~700%焙烧温域有突变上升。对不同温度焙烧的HZSM-5样品的NMR观察证实,随预焙烧温度升高,B酸中心数量减少,也在600℃~700℃焙烧温域有突变式的骤降。研究L酸中心的增加和B酸中心数量的减少之间的关联有助于深化对分子筛酸中心认识,并提供分子筛改性的依据。
EPR experiments confirmed that the direct synthesis of molecular sieve powder by acid exchange (HZSM-5), 150 ℃ drying (non-baking) skeleton of the sample exists L acid center. With the increase of calcination temperature, the number of L acid sites increased, and the temperature increased abruptly from 600% to 700% calcination temperature. NMR observation of HZSM-5 samples calcined at different temperatures confirmed that as the pre-calcination temperature increased, the number of B acid sites decreased and there was a sudden drop in the calcination temperature range from 600 ° C to 700 ° C. The study of the relationship between the increase of L acid sites and the decrease of B acid sites will help to deepen the understanding of molecular sieve acid centers and provide a basis for molecular sieve modification.