《Table 1Acidic properties of ZSM‐35 zeolites after sodium ion‐exchange treat‐ment.》

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《HZSM-35分子筛酸性质对甲缩醛和乙酸甲酯羟醛缩合反应的影响（英文）》

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*Calculated through integration of IR peak.

The IR characterization is used to clarify the change in the acidic properties of zeolites after the treatment.The intensity of the bridging OH groups at 3599 cm–1 suffers a significant de‐crease after sodium ion exchange，as illustrated in Fig.5（a），which indicates that the Br?nsted acidic proton of HZSM‐35zeolite is substituted by Na+.A higher exchange degree leads to a lower intensity of the Br?nsted acid hydroxyl groups.In HZSM‐35 zeolite，the IR band of Py H+appears at 1545 cm–1after adsorption of pyridine at 623 K for 30 min with the band of pyridine adsorbed on typical Lewis acid sites at 1445 cm–1（Fig.5 （b）） [41，42].The Lewis acid sites in HZSM‐35 are as‐signed to the extra‐framework aluminum species.The intensity of the band at 1545 cm–1 drops significantly with the pretreat‐ment of the sodium ion‐exchange process，which indicates a decrease in the concentration of Br?nsted acid in ZSM‐35 zeo‐lite.As shown in Table 1，the concentration of the Br?nsted acid in HZSM‐35 zeolite，obtained by the integration of the band at1545 cm–1，is 0.049 mmol/g，which decreases to 0.037 mmol/g in Na‐Z‐25 zeolite and even falls to 0.011 mmol/g in Na‐Z‐49zeolite.The concentration of the Lewis acid remains constant at0.004 mmol/g.