水热处理对SAPO-34分子筛在合成气一步法制烯烃反应中性能的影响

Effect of hydrothermal treatment on performances of SAPO-34 zeolites in direct conversion of syngas to light olefins

对SAPO-34分子筛在700℃、质量分数为100%的水蒸汽下进行水热处理,采用XRD、NH;-TPD及固体MAS-NMR等表征分析了水热处理对分子筛的结构、酸性的影响。结果表明,SAPO-34分子筛在水热处理过程中结晶度提高,Si(4Al)物种逐渐向Si(3Al)物种转变,SAPO-34分子筛酸强度增加。固定床评价结果显示,SAPO-34分子筛经水热处理12 h后与ZnCr_(2)O_(4)制得的双功能催化剂(BS-12)在合成气一步法制烯烃反应中性能最佳,CO转化率约为23%,C_(2)^(=)~C_(2)^(=)的烯烃选择性约为75%。长周期实验显示,催化剂运行120 h无明显失活。

SAPO-34 zeolites were hydrothermally treated by water steam with a mass fraction of 100%under 700℃.Fresh and hydrothermally treated SAPO-34 zeolites were characterized by XRD,NH;-TPD and solid-state MAS-NMR to investigate the effects of hydrothermal treatment conditions on the structure and acidity of SAPO-34 zeolites.The results show that the crystallinity of SAPO-34 zeolites increases,Si(4Al) species gradually transform to Si(3Al) species,and acid strength of SAPO-34 zeolites increases during hydrothermal treatment.The results of fixed-bed evaluation show that the bifunctional catalyst (BS-12) prepared by mixing ZnCr_(2)O_(4)and SAPO-34 after 12 h of hydrothermal treatment,has the best reaction performance in direct conversion syngas to light olefins reaction.The CO conversion and C_(2)^(=)-C_(2)^(=)selectivity in hydrocarbon is about 23% and 75%,respectively.The long period experiment shows that the catalyst has no obvious deactivation after 120 h running.