多级孔道ZSM-22分子筛的合成及其正庚烷加氢异构反应性能

Synthesis of Hierarchical HZSM-22 and its Catalytic Properties in n-Heptane Hydroisomerization

为了将正庚烷变成辛烷值较高的单支链或多支链异构烷烃来提高汽油组分的辛烷值和燃烧效率,采用球磨-重结晶的方法制备了多级孔道ZSM-22-M-R-2分子筛和常规水热法合成了ZSM-22-C分子筛,进而通过浸渍法制备了含Pt量为0.5%的催化剂。借助X射线粉末衍射、扫描电镜、N2物理吸附、氨吸附-程序升温脱附、吡啶红外光谱表征手段分析了催化剂样品的结构和酸性。在固定床反应器中,研究了这两种催化剂的正庚烷加氢异构反应性能。结果表明:ZSM-22-M-R-2分子筛具有的酸量和ZSM-22-C分子筛相当,但具有更小的粒径;其异构化反应活性、异构产物的选择性和收率均高于常规ZSM-22-C分子筛。在反应温度为300℃时,异构产物的最大收率为68%。

In order to increase n-heptane into a single-chain or multi-branched isoparaffin with a higher octane number to improve the octane number and combustion efficiency of the gasoline component The ZSM-22-M-R-2 zeolite and ZSM-22-C zeolite have been synthesized using ball milling-recrystallization method and conventional hydrothermal method respectively. Then Pt-loaded catalysts were prepared by impregnation treatment for comparison of catalytic performance in hydroisomerization of n-Heptane which was hypothesized for production of isomers with high octane number. As-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), nitrogen adsorption, ammonia temperature-programmed desorption (NH3-TPD) and pyridine adsorption infrared spectroscopy (Py-IR) for the elucidation of relationship between catalytic properties and structural characteristic and acidity. Research was conducted over bench-scale fixed-bed reactor and results showed that Pt/ZSM-22-M-R-2 with smaller crystal size has higher reactivity and selectivity in hydroisomerization of n-Heptane compared with Pt/ZSM-22-C, meanwhile they have similar acid amount. The highest attainable isomerization yield of 68% was obtained when reaction temperature was set to 300 ℃.