水热处理对SAPO-34分子筛在MTO反应中的影响

Effect of steaming treatment on the performances of SAPO-34 in MTO reaction

关键词:  MTO  SAPO-34  低碳烯烃  水热处理

Key words:  methane to olefin (MTO)  SAPO-34  olefin  steaming treatment

摘要:

对SAPO-34分子筛在800 ℃、质量分数为100%水蒸气下进行0~100 h水热老化。结果 表明:随着老化时间的延长,相对结晶度呈下降趋势；总比表面积下降了59.6 m²/g,微孔比表面积下降了95.0 m²/g。NH₃-TPD酸性测试表明,老化后SAPO-34的酸量大幅下降,尤其是强酸量下降幅度更大。在水热处理0~45 h内,酸性的变化尤为明显,而水热处理45 h以后,酸量变化幅度明显减少。固定床评价结果显示,在水热处理45 h之内,MTO反应中SAPO-34分子筛的寿命明显增加,但低碳烯烃的选择性未有改变,水热处理45 h以后,寿命几乎不变,但低碳烯烃的选择性明显变好,乙烯和丙烯收率最高可提高7.43%。

Abstract:

SAPO-34 was undergone by hydrothermal treating with 800 ℃, 100 w% steam for 0-100 h. XRD results showed that the relative crystallinity was decreased with the increase of the hydrothermal treating time. The BET surface area was decreased by 59.6 m²/g and micropore surface area decreased by 95.0 m²/g with treating time increased from 0 h to 100 h. NH₃-TPD indicated that when hydrothermal treating time was between 0~45 h, the total acidities sharply deceased, especially the strong acidities. After 45 h, the change of acidities was little. Fixed bed reaction tests showed that when hydrothermal treating time was between 0~45 h, the catalytic life of SAPO-34 was prolonged over two times, while the selectivity for C=₂ + C= _3remained nearly the same with SAPO-34 untreated. After 45 h, the selectivity for C=₂ + C=₃ was improved greatly but catalyst life didn’t chang. The yield of C=₂ + C=₃ was up to 7.43%.