阳离子(K^+、Na^+)对非水体系合成ZSM-48沸石性能的影响

INFLUENCES OF CATIONS(K^+,Na^+)ON ZSM-48 ZEOLITES SYNTHESIZED IN NO-AQUEOUS MEDIUM

研究了在非水体系(双胺体系)中KZSM-48和NaZSM-48沸石的晶化过程,发现NaZSM-48的晶化速度明显较KZSM-48为快。通过SEM、IR和TG-DTA的测定,发现K^+、Na^+离子对非水体系合成的ZSM-48沸石物性有较大的影响。晶化过程中在液相未检出SiO_2和Al_2O_3,表明在非水体系中ZSM-48沸石的生成属于固相转化。并且随着SiO_2/Al_2O_3比的增加,KZSM-48的晶粒粒径增大。通过CO+H_2生成烯烃反应可以看出NaZSM-48较KZSM-48有较高的活性和烯烃选择性。

The crystallizations of K-ZSM-48 and Na ZSM-48 in nouaqueous medium are reported. The crystallization of NaZSM-48 is quick er than that of KZSM-48. Studies with SEM, IR and TG-DTA show that the cations(K^+Na^+) exert important influences on the properties of ZSM-48. The average crystal size of KZSM-48 is large than that of NaZSM-48. The morphologies of KZSM-48 and NaZSM-48 are different. The cations (K^+, Na^+) have more effects on the IR patterns of ZSM-48, especially on the vibration of the double ring(about 550cm^(-1)).The exothermic peak of KZSM-48 is located at 494℃, while that of NaZSM-48 is at 386℃. The average crystal size of KZSM-48 increases with the increase of the mole ratio of SiO_2/Al_2O_3. With the increase of SiO_2/Al_2O_3, the wave number for the vibration of the external asymmetric stretch band increases. During the whole course of crystallization, no Si or Al was detected in the organic solvents. This result shows that the crystallization of ZSM -48 is probably a solid phase transformation process in the non-aqueous medium. KZSM-48 can be synthesized when SiO_2/Al_2O_3 is 54, which has not been reported in the literature. With the extending of crystallization period, the strenth of the band at 545cm^(-1) in the IR patterns increases. As catalysts for the reaction of CO+H_2, the activity of NaZSM-48 is higher than that of KZSM-48. When NaZSM-48 is loaded with a certain amount of K and Fe, the convertion of CO is 34.7%.