不同铝源对SBA-15分子筛改性影响

Effects of different aluminum sources on the modification of SBA-15 molecular sieve

为比较不同铝源对SBA-15分子筛改性的影响,以正硅酸乙酯为硅源,分别用异丙醇铝、氯化铝和硝酸铝对SBA-15分子筛进行改性,运用XRD、N2等温吸附-脱附、SEM、TEM和气相色谱对样品进行表征。将3种不同铝源改性SBA-15分子筛与USY分子筛复合制备加氢裂化催化剂,在固定床微型反应装置进行加氢裂化性能评价,结果表明,异丙醇铝在酸性条件下水解生成的Al(OH)-4更容易进入SiO2骨架中,生成的产物异丙醇不影响铝离子的掺杂,由于异丙醇铝与正硅酸乙酯的水解速率一致,改性后所得材料孔分布更均一,规整性更高。将异丙醇铝对SBA-15分子筛改性后,与USY制备的复合分子筛催化剂用于正十二烷加氢裂化反应,选择性和转化率优于氯化铝和硝酸铝改性的分子筛。

In order to investigate the influence of different aluminum sources on the modification of SBA-15 molecular sieve, modified AlSBA-15 molecular sieves were prepared using tetraethyl orthosilicate as silica source,isopropanol aluminum,aluminum chloride and aluminum nitrate as aluminum sources. The as-prepared samples were characterized by means of XRD, TEM, SEM, N2 adsorption-desorption and gas chromatography. The composite molecular sieves catalysts AlSBA-15/USY were prepared by using USY zeolite and AlSBA-15 samples,The hydrocracking performance of as-prepared catalysts were evaluated in a fixed bed microreactor. The results showed that under acidic condition,isopropanol aluminum hydrolyzed and formed Al（OH） 4^-, which easily entered the framework of SiO2; hydrolysate isopropanol did not affected the doping of Al（OH） 4^-. Because hydrolysis rates of isopropanol aluminum and tetraethyl orthosilicate were consistent, the as-prepared samples after modification possessed more uniform pore size distribution and higher regularity. The composite molecular sieve catalyst prepared by USY zeolite and AlSBA-15 molecular sieve modified with isopropanol aluminum was used for n-dodecane hydrocracking, and exhibited better conversion and selectivity than the catalysts prepared with modified molecular sieves by aluminum chloride and a｜uminum nitrate.