提出了一种有效改善SBA-15介孔材料水热稳定性的简单溶剂热后处理方法. SBA-15材料经环己烷、甲苯和正丁醇等有机溶剂在157和190 oC密闭容器中分别处理6–24 h后,可呈现很好的水热稳定性.它们在800 oC经100%水蒸气处理12 h,依然能保持很好的有序介孔结构,比表面积可高达192–281 m2/g.其中,经环己烷190 oC溶剂热处理24 h的样品表现出最优的水热稳定性.溶剂热处理能显著提升材料孔壁中类似Si(OSi)2(OH)2和Si(OSi)3OH结构的Si–OH基间脱水,形成稳定的Si(OSi)4结构,从而有效减少了SBA-15材料孔壁的缺陷.由此,介孔材料的水热稳定性得到明显改善.溶剂热处理对SBA-15材料水热稳定性的这种提升作用与所用溶剂性质、处理温度以及SBA-15前驱体的类型密切相关.其中,以低沸点的非极性溶剂处理焙烧后的SBA-15材料表现出最好的稳定化效果.该方法具有简单、低能耗的特点,其在制备高水热稳定的有序硅基介孔材料上有很好的潜在应用价值.
A simple and effective approach is demonstrated to improve the hydrothermal stability of mesopo-rous SBA-15 zeolite via a post-synthesis treatment of organic solvents, such as cyclohexane, toluene and n-butanol, at 157 or 190 °C for 6–24 h. After hydrothermal treatment at 800 °C for 12 h in 100%steam, the treated SBA-15 retained a well-ordered mesostructure, and retained high surface areas of 192–281 m2/g. SBA-15 zeolite treated by cyclohexane at 190 °C for 24 h showed the highest hy-drothermal stability. The stabilization mechanism suggests that the solvothermal treatment has a significant promoting effect on dehydrating Si–OH groups in silica walls to form stable Si(OSi)4 from Si(OSi)2(OH)2 or Si(OSi)3OH groups. As a result, the wall defects after solvothermal treatment de-crease, and the stability of silica is improved remarkably. This promoting effect strongly depends on the solvent properties, treatment temperature, and precursors of SBA-15 zeolite. The treatment by a nonpolar and low boiling point organic solvent displays the highest promoting effect on the cal-cined SBA-15 zeolite. This approach is simple, has low energy consumption and has potential appli-cation in the laboratory and for industry to prepare hydrothermally stable well-ordered mesopo-rous SBA-15 zeolite.
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