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本文用红外光谱法以重水和吡啶为探针分子考察了AlPO_4-5,SAPO-5和HZSM-5分子筛上的表面羟基和酸性质。结果表明,在SAPO-5上3745cm~(-1),3677cm~(-1),3630cm~(-1)和3520cm~(-1)附近出现四个羟基谱带,并且都是酸性羟基,而AIPO_4-5仅在3677cm~(-1)和3630cm~(-1)处存在两个非常微弱的羟基峰。吡啶吸附的红外光谱实验结果进一步表明SAPO-5上同时存在B酸和L酸中心。从氨的程序升温脱附谱明显看出HZSM-5沸石上存在有强酸和中强酸两类酸中心,而AlPO_4-5和SAPO-5上只有中强酸这一类酸中心,其总酸量和酸强度的大小次序为:HZSM-5>SAPO-5>AlPO_4-5。
In this paper, the surface hydroxyl and acid properties of AlPO 4 -5, SAPO-5 and HZSM-5 zeolites were investigated by infrared spectroscopy using heavy water and pyridine as probe molecules. The results showed that four hydroxyl bands appeared at 3745 cm -1, 3677 cm -1, 3630 cm -1 and 3520 cm -1 on SAPO-5, and all of them were acidic hydroxyl groups. However, AIPO_4-5 has two very weak hydroxyl peaks only at 3677cm -1 and 3630cm -1. Pyridine adsorption infrared spectroscopy experimental results further show SAPO-5 on the existence of B acid and L acid center. It is obvious from the temperature-programmed desorption spectra of ammonia that HZSM-5 zeolites have two kinds of acid centers: strong acid and medium strong acid, while the only acid sites such as medium strong acid in AlPO4-5 and SAPO-5, The order of acid strength is HZSM-5> SAPO-5> AlPO_4-5.