氟化铵改性USY分子筛及催化脱烯烃反应的研究

STUDY OF USY MOLECULAR SIEVE MODIFIED BY AMMONIUM FLUORIDE AND ITS CATALYTIC DEOLEFIN PERFORMANCE

采用X射线衍射、扫描电镜、N 2吸附-脱附、27 Al固体核磁共振和吡啶吸附-红外光谱等分析手段对氟化铵改性前后的USY分子筛进行表征,并在微型固定床反应装置上考察该分子筛催化脱除混合芳烃中烯烃的性能。结果表明,氟化铵改性可以有效调节USY分子筛的孔结构和酸性,骨架铝组分被脱出并沉积在孔道内,微孔孔体积基本不变,但孔径减小,介孔和大孔孔体积及孔径增加,改性USY分子筛的L酸酸量为改性前的3倍,B酸酸量变化较小,适合脱烯烃反应需求。氟化铵改性后USY分子筛催化脱烯烃反应时可以大幅提高转化率,并且催化剂失活慢。

USY molecular sieves before and after ammonium fluoride modification were characterized by X-ray diffraction,scanning electron microscopy,N 2 adsorption-desorption,27 Al solid nuclear magnetic resonance,and pyridine adsorption-infrared spectroscopy,and its performance of removing trace amount of olefins from mixed aromatics was investigated in a bench-scale continuous-flow fixed bed reactor.The results showed that the pore structure and acidity of the USY molecular sieve could be effectively adjusted by ammonium fluoride modification;the framework aluminum component was extracted and deposited in the pores,the micro pore volume was basically unchanged;the pore size decreased,but the mesoporous and large pore volumes increased.The Lewis acid content of modified molecular sieve was 3 times that of before modification,but the change of Bronsted acid content was small.It is proved that the F-modified USY sieve can greatly reduced catalyst deactivation and increase the conversion rate of olfines.