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Synthesis of ZSM-5 structures via template-free sol–gel method
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Hierarchical porous materials with ZSM-5 structures were synthesized by a three-step procedure. The first step consists of the preparation of ZSM-5 precursor sol. In a typical synthesis, 25.4 g of 20% aqueous solution of TPAOH was added to the mixture of 20.8 g of TEOS and 0.4 g of Al(i-OPr)3 under vigorous stirring at 273K to obtain a turbid solution with molar composition of 1.0TEOS: 0.02Al(i-OPr)3: 0.25TPAOH: 11.3H2O. Clear ZSM-5 precursor sol containing a little floccule was obtained by stirring the turbid solution at 323K for 48 h. In the second step, the ZSM-5 precursor sol filtrated floccule was dried at 303K in a vacuum box retaining the vacuum value of 6.65 kPa until it became xerogel. Thesilica content in the xerogel was about 7.7*10-3mol/g. The third step involves the recrystallization of the xerogel. The mixture of xerogel and water (1Si: 150 water, molar ratio) was transferred into Teflon-lined stainless steel autoclaves and carried out hydrothermal synthesis at a certain temperature for 24 h. Finally, the solid products were filtered, washed, dried at 303K in a vacuum box and calcined at 823K in air for 6 h. The obtained hierarchical porous materials were named as HPM-X, where X indicates the temperature of recrystallization. For comparison, the direct-calcined xerogel (DCX) was also prepared. |
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jiangguofeng
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RXMCDM: 金币+1 2014-05-21 11:29:16
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无模板溶胶-凝胶法合成ZSM-5结构 通过一种三步方法合成具有ZSM - 5结构的分层多孔材料。 第一步制备ZSM -５前体溶胶。在一种曲型的合成方法当中，强烈搅拌下于273K温度中，将25.4克20%四丙基氢氧化铵水溶液加到20.8克正硅酸乙酯和0.4克三异丙氧基铝的混合物中，得到一种浑浊液，其摩尔组成为1.0正硅酸乙酯：0.02三异丙氧基铝：0.25四丙基氢氧化铵：11.3 H2O。于323K温度中搅拌这种浑浊液48小时，得到含有少量?occule的透明的ZSM-5前体溶胶。 第二步,于一个保持6.65 kPa真空度的真空箱中，于303K温度干燥这种ZSM - 5前体溶胶?ltrated ?occule直至成为干凝胶。干凝胶中的含硅量为大约7.7×10 - 3mol／克。 第三步包括干凝胶的再结晶。将这种干凝胶和水（1 Si : 150 水,摩尔比）的混合物移至Te?on -衬里的白钢高压釜中，于一定温度进行热液合成24小时。 最后，固体产物经过滤、洗涤、于真空箱中303k温度干燥以及于823K温度在大气环境下焙烧６小时。得到的分层多孔材料命名为HPM - X,其中X表示再结晶温度。作为对比，也制备了直接焙烧干凝胶（DCX）。 |
2楼2014-05-21 11:16:53
