含介孔的Y型分子筛的合成及其催化裂化性能

Preparation and Catalytic Cracking Performance of Zeolite Y with Mesopores

采用X射线衍射、透射电子显微镜和氮气物理吸附等方法对水热法合成的含介孔Y型分子筛样品进行表征。合成样品的X射线衍射谱图与Y型分子筛的特征衍射谱图一致,衍射角0~5°范围内无明显的衍射峰,说明合成样品中不含有序介孔。合成样品的介孔孔径与CTAB模板剂形成的胶束直径相近,约为2~5nm,介孔比表面高达229m2/g。与Na Y分子筛的吸附等温曲线不同,在相对压力0.5附近,合成样品的吸附等温线上出现了第二个饱和吸附。合成样品的吸-脱附等温曲线上,没有出现明显的吸-脱附回滞现象,其可能原因为合成样品的介孔孔径较小。ACE评价结果表明,与稀土改性的Na Y分子筛相比,稀土改性的含介孔Y型分子筛具有更高的转化率、更低的柴油和重油收率、更高的液化气和汽油选择性、更低的干气和焦炭产率,这可能是由于分子筛富含2~5nm的介孔,使得烃类分子的扩散更加容易所致。

Technicians used a series of methods,including X-ray diffraction,transmission electron microscopy and nitrogen physical absorption,to characterize Y-typed Zeolite samples with mesopores synthesized in the hydrothermal process.The X-ray diffraction spectrogram of the synthesized samples is identical to the characteristic diffraction spectrogram of Zeolite Y.The diffraction angle had no obvious diffraction peak within the range of 0-5° ,meaning that the sample does not have ordered mesopores.The aperture of the mesopores in the synthesized samples is similar to the diameter of the micella generated by CTAB template agent, standing at about 2-5nm.The specific surface area of mesopores is as high as 229m2/g.Different from the adsorption isothermal curve of NaY molecular sieve,near the relative pressure of 0.5,second saturation adsorption oc- cured on the adsorption isothermal curve of the sythesized samples.No obvious adsorption-desorption hysteresis occured on the adsorption-desorption isothermal curve of the synthesized samples,possibly due to the small aperture of mesopores of the samples.ACE results show that compared with NaY molecular sieve from rareearth modification,Zeolite Y with mesopores from rare-earth modification has higher conversion rate,lower diesel and heavy oil yields,higher LPG and gasoline selectivity and lower dry gas and coke yields,possibly due to the extensive distribution of 2-5nm mesopores of the molecular sieve ,which makes diffusion of hydrocarbon molecules easier.