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

对SAPO-34分子筛在800℃、质量分数为100%水蒸气下进行0～100h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59.6m^2/g,微孔比表面积下降了95.0m^2/g。NH_3-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0～45h内,酸性的变化尤为明显,而水热处理45h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45h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45h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%。

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 m 2/g and micropore surface area decreased by 95.0 m 2/g with treating time increased from 0 h to 100 h.NH 3-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%.