Study on the formation of mesopore during hydrothermal dealumination of Y zeolite
Study on the formation of mesopore during hydrothermal dealumination of Y zeolite
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DOI：
10.3866/pku.whxb20020303
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发表时间：
2002-03-01
影响因子：
10.9
通讯作者：
Kang, XH
中科院分区：
文献类型：
--
作者：
Dong, ST;Li, XW;Kang, XH
研究了不同Na2O含量的NH4NaY水热脱铝过程中Y沸石介孔的形成。仅通过将温度升高至650℃就观察到“伪稳态”(PSS)，维持了IR特性吸光度并且在此阶段很少发生脱铝，因此BET表面积、孔体积显着下降。然而，通过引入蒸汽，它们可以增加，甚至可以在1小时内大于原始NaY，并且可以通过进一步处理而减少。表明升温阶段形成的高电子亲和力质子与骨架氧发生强烈相互作用，引起沸石骨架的扭曲、弛豫和分裂。然而，含有一定量Na+的方钠石笼保持相对稳定。稳定后的方钠石在高温、水热条件下可以重新排列结构，但由于骨架脱铝产生的骨架外氧化铝和无定形二氧化硅的存在而无法愈合，只能形成方钠石有损伤（缺陷）的锋利八面沸石。这可能是介孔形成的机制。
Mesopore formation of Y zeolite in hydrothermal dealuminated process was studied over NH4NaY with different Na2O content. A "pseudo-steady state" (PSS) was observed by merely raising temperature to 650 degreesC, IR characteristic absorbency maintained and few dealumination occurred in this stage, therefore BET surface area, pore volume leveled down substantially. However, they could increase by introducing steam, even could be larger than that of the original NaY in 1 h, and could decrease by further treatment. It was pronounced that protons with high electron affinity formed in temperature-raising stage interacted strongly with frame oxygen, and brought about twist, relaxation and split of zeolite frame. However, sodalite cages with a certain amount of Na+ kept relatively stable. Then structure could be rearranged based on the stabilized sodalites under the high temperature, hydrothermal condition, but it couldn't heal over due to the existance of extraframe alumina and amorphous silica coming from framework dealumination, only sharp faujasite with damage (defects) in sodalite could be formed. This probably is the mechanism of mesopore formation.