碱酸联合处理介孔改性丝光沸石及其结构表征

Mesoporous Modification of Mordenites by Treatment with Alkali-Acid and Their Characterization

以硅溶胶为硅源、铝酸钠为铝源,采用含氟水热合成体系制备了结晶度保留率高、晶体尺寸大的氢型丝光沸石(H-MOR),并采用水热碱蚀-碱溶滤-酸洗法(简称碱酸联合处理法)对H-MOR进行介孔改性,考察了水热碱蚀、碱溶滤与酸洗处理过程对不同硅铝比的H-MOR的介孔结构、晶体形貌、介孔分布、结晶度保留率及收率的影响。实验结果表明,采用碱酸联合处理法可制得介孔率高、孔分布窄的改性H-MOR;水热碱蚀过程诱导晶内介孔的形成与空间分布,酸洗过程促进沸石骨架脱铝且有拓孔作用;随骨架硅铝比的增大,介孔体积和最可几介孔孔径逐渐增大,结晶度保留率和收率呈下降趋势。由硅铝比为50的凝胶得到的改性H-MOR的介孔体积为0.127 cm3/g,介孔比表面积为206.8 m2/g,最可几介孔孔径为5.2 nm。

H-type mordenites（H-MORs） were synthesized from silica sol as silicon source and sodium aluminate as aluminium source in a hydrothermal system containing fluorine, and then modified by hydrothermal alkaline etching, alkaline leaching and acidpickling in turn. The modified H-MORs were characterized by XRD and SEM, and the effects of the hydrothermal alkaline etching, alkaline leaching and acid pickling on the mesoporous structured, crystal morphology, mesopore size distribution, relative crystallinity and yield of the modified H-MORs were investigated. The results revealed that H-MORs with high mesopore volume and narrow pore distribution could be obtained by the alkali-acid treatment. The hydrothermal alkaline etching induced the formation of intracrystalline mesopores and led to the spatial distribution of mesopores while the acid leaching promoted desilication in the framework and broadened the pore diameter. With increasing silica- alumina ratio in the framework, both the mesoporous volume and most probable mesopore size of the modified H-MORs increased whereas the crystallinity retention rate and yield decreased. The mesoporous volume, specific surface area and most probable mesopore size of a typical H-MOR sample from gel with silica-alumina ratio 50 were 0.127 cm^3/g, 206.8 m^2/g and 5.2 nm, respectively.