NaOH后处理对多级孔Hβ分子筛上木质素催化热解性能的影响

采用碱性条件下"后处理"脱硅的方法,制备了一系列多级孔Hβ分子筛,考察了Na OH浓度对Hβ分子筛上木质素催化热解性能的影响。结果表明,当Na OH浓度小于0.2 mol/L时,碱处理后的多级孔Hβ分子筛的介孔数量增加,木质素热解液体产物的收率随着Na OH浓度提高而显著增加。当Na OH浓度小于0.5 mol/L时,碱处理可以保持多级孔Hβ分子筛的微孔结构基本不被破坏,木质素催化热解具有较好的脱氧效果;产物以芳烃为主,含氧化合物的收率始终小于3%。当Na OH的浓度增加到1 mol/L时,会造成Hβ分子筛过度脱硅,骨架坍塌;由于Hβ分子筛的多级孔结构被破坏,此时不仅木质素热解液体产物的收率降低,而且脱氧效果变差。

Effect of NaOH post-treatment on the catalytic performance of hierarchical Hβ zeolites in the pyrolysis of lignin

A series of hierarchical Hβ zeolites were prepared by using NaOH post-treatment methods, viz., desilication under alkaline conditions; the effect of NaOH concentration on the catalytic performance of hierarchical Hβ zeolites in the pyrolysis of lignin was investigated. The results illustrated that with the increase of NaOH concentration up to 0.2 mol/L, the amount of mesopores in the hierarchical Hβ zeolites is increased, accompanying with a significant increase in the yield of liquid products for the lignin pyrolysis over Hβ zeolites. By the alkaline treatment with a NaOH concentration lower than 0.5 mol/L, the microporous structure of hierarchical Hβ zeolites remains basically intact and over them a good deoxidation effect is observed for the lignin pyrolysis; the product is mainly composed of aromatic hydrocarbons and the yield of oxygenates is always less than 3%. However, if the NaOH concentration for post-treatment is further increased to 1 mol/L, the microporous structure of Hβ zeolites is substantially destroyed, leading to a decrease in the yield of liquid products for lignin pyrolysis as well as a poor deoxidization effect.