Hβ改性Co/SiO2对费托合成航空燃油类烃的影响

摘要

Bi-functional catalysts were prepared using hybrid supports, mesoporous SiO2(SG) and microporous Hβzeolites with different Si/Al ratios of 25, 60 and 80 for direct jet fuel-range hydrocarbon synthesis (C8-C18). The textual and structural properties of the catalysts were studied by Fourier transform infrared (FTIR), X-ray diffraction(XRD), H2-temperature-programmed desorption(H2-TPR) and N2 physisorption. The results showed that catalysts supported on tailor-made SiO2 and Hβhybrid maintained both meso-and micro-pores with acid centers. With the decrease of Si/Al ratio, the bands corresponding to the characteristic adsorptions of Co/SG/Hβcatalysts shifted to the lower wave num-bers, which accompanied by increased acidity. SiO2 decreased the acidity of Hβand the interaction between Co and support, resulting in high Co dispersion, reduction and CO conversion for Co/SG/Hβ. The microporous structure and acidity of Hβaccelerated the hydrocracking/hydroisomerizaion reaction, which contributed to the high selectivity to jet fuel-range isoparaffins. The increased BET surface area and microporous volume with moderate acidity of Co/SG/Hβ(80) were essential for its high CO conversion (95.7%) and selectivity to jet fuel-range hydrocarbons (42.3%, including 27.6%of isoparaffins).%在中孔SiO2(SG)和微孔Hβ分子筛(Si/Al=25、60、80)组成的复合载体上，制备了多功能Co基费托合成催化剂，考察了其合成航空燃油类烃(C8~C18)的性能。XRD、FTIR、H2-TPR、N2-物理吸附研究表明：Hβ的引入，使得Co/SG/Hβ催化剂具有一定酸性和微孔结构。随分子筛硅铝比的降低，催化剂红外图谱的特征波数向低波数移动，酸性有所提高，中孔 SiO2消弱了其酸性及载体与金属粒子相互作用，提高了 Co分散和还原度及加氢活性。Hβ的微孔结构和酸性促进了初级产物裂解及异构化反应，提高了异构烃类选择性。Co/SG/Hβ(80)催化剂较大的比表面积和微孔体积及适当的酸性中心是其高活性(CO转化率95.7%)及高航空燃油类烃选择性(42.3%，其中异构烃为27.6%)的关键因素。