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本文利用红外光谱法考察了HZSM-5型沸石在100—600℃之间表面结构OH基的吸收谱带(3720与3608厘米~(-1)及3668厘米~(-1)处的肩峰),比较了用乙胺与四乙基氢氧化铵为原料合成的HZSM-5型沸石的表面性质(OH基与氘交换性质)。化学吸附吡啶的红外光谱表明该沸石表面上有质子酸中心与非质子酸中心,这两种酸性中心在一定的条件下可相互转化。表征质子酸的3608厘米~(-1)谱带强度大于3720厘米~(-1)。当温度由100增到400℃时,酸性不断增加,超过这个温度时,3608厘米~(-1)处的谱带强度开始下降,非质子酸开始增大。
In this paper, the absorption bands (3720, 3608 cm -1 and 3668 cm -1) of the OH groups of the surface structure of HZSM-5 zeolite at 100-600 ℃ were investigated by infrared spectroscopy. The surface properties of HZSM-5 zeolite synthesized by using ethylamine and tetraethylammonium hydroxide (OH group and deuterium exchange properties) were compared. Infrared spectra of chemisorbed pyridine indicate that the zeolite has a protonic acid center and an aprotic acid center on the surface, and these two kinds of acid centers can be transformed into each other under certain conditions. Characterization of the proton acid 3608 cm ~ (-1) band intensity greater than 3720 cm ~ (-1). The acidity increases as the temperature increases from 100 to 400 ° C, and beyond this temperature the intensity of the band at 3608 cm -1 begins to decrease and the aprotic acid begins to increase.