Simple Quaternary Ammonium Cations-Templated Syntheses of Extra-Large Pore Germanosilicate Zeolites
Simple Quaternary Ammonium Cations-Templated Syntheses of Extra-Large Pore Germanosilicate Zeolites
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DOI：
10.1021/acs.chemmater.6b03179
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发表时间：
2016-09-27
影响因子：
8.6
通讯作者：
Yu, Jihong
中科院分区：
文献类型：
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作者：
Bai, Risheng;Sun, Qiming;Yu, Jihong
沸石是一类由TO4 （T= Si、Ge、Al、P等）四面体单元形成的具有均匀孔隙和规则通道的无机微孔晶体材料。它们具有独特的多孔结构、高表面积、中等酸度和优异的热稳定性，在离子交换、吸附和催化方面具有重要意义。3,4然而，沸石的狭窄孔洞严重阻碍了大分子的运输，从而限制了沸石在大分子催化转化中的性能。这样的问题可以通过使用介孔材料或分级沸石来解决。7−9但介孔材料的水热稳定性和酸性不如结晶沸石；10另一方面，使用表面活性剂分子和有机阳离子组合模板合成分级沸石时，通常会生成由沸石晶体和无定形介孔材料组成的杂质相，而不是分级沸石。为了克服这些问题，人们在合成超大孔径沸石（T - bbb12）方面做了很大的努力，并取得了很大的进展，如成功制备了VPI-5 (VFI, 18- r)， 12个UTD-1 (DON, 14- r)， 13个ITQ-33 (ITT, 18- r)， 14个ITQ-37 (-ITV, 30-R)， 15个ITQ-40 (-IRY, 16- r)， 16个ITQ-43 (28-R)， 17个ITQ-44 (IRR, 18- r)， 18个ITQ-51 (IFO, 16- r)， 19和ITQ-54 (-IFU, 20- r)， 20等。最近，成功合成了一种新的锗硅酸盐沸石，命名为ndd -1，具有18环通道，进一步丰富了超大孔沸石家族。值得注意的是，超大孔沸石在裂解稠油方面很有前景。14使用设计合理的模板，具有体积大、刚性适中、碳氮比合适等特点，是合成具有新型沸石拓扑结构的超大孔沸石的关键策略之一。然而，这些模板的合成过程复杂，成本昂贵，有时毒性高，这些都限制了超大孔沸石的大规模工业应用。值得注意的是，Strohmaier等人以四乙基铵（TEA）阳离子与碱金属为模板，成功制备了含有18环通道体系的ECR-34 (ETR)， 23 Lin等人以N， N-二异丙基乙基甲基铵为模板，以N， N-二异丙基乙基乙胺和剧毒的碘化甲基为原料合成了PKU-12 （-CLO, 20-R）。24然而，当使用简单、廉价和商业上可用的季铵碱，如四乙基氢氧化铵（TEAOH）、四丙基氢氧化铵（TPAOH）和四丁基氢氧化铵（TBAOH）作为唯一的有机模板时，所获得的沸石框架的最大开窗不超过12环，如沸石MFI、25* BEA、26 SZR、27和MEL、28等。本文以一系列简单季铵氢氧化铵TEAOH （~ 8 Å）、TPAOH （~ 9 Å）和TBAOH （~ 10 Å） 29为唯一有机模板，首次通过引入成功合成了特大孔锗硅分子筛ITQ-33 （18R× 10R× 10R）、ITQ-44 （18R× 12R× 12R）和nad -1 （18R× 12R× 10R）
Zeolites are a class of inorganic microporous crystalline materials formed by TO4 (T= Si, Ge, Al, P, etc.) tetrahedral units with uniform pores and regular channels. 1, 2 They are of great importance in ion-exchange, adsorption, and catalysis, because of the unique porous structures, high surface areas, moderate acidities, and excellent thermal stabilities. 3, 4 However, the narrow pore openings of zeolites strongly hinder the transportation of bulky molecules, and thus restrict the performance of zeolites in the catalytic conversion of large molecules. 5, 6 Such a problem can be solved by the utilization of mesoporous materials or hierarchical zeolites. 7− 9 However, the hydrothermal stability and acidity of the mesoporous materials are not as sufficient as those of the crystalline zeolites; 10 on the other hand, using the combined templates of surfactant molecules and organic cations in synthesizing hierarchical zeolites usually generates impurity phases composed of zeolite crystals and amorphous mesoporous materials instead of the hierarchical zeolites. 11 To overcome these problems, great efforts have been made to synthesize zeolites with extra-large pores (T> 12), and so far much progress has been achieved, for instance, the successful preparation of VPI-5 (VFI, 18-R), 12 UTD-1 (DON, 14-R), 13 ITQ-33 (ITT, 18-R), 14 ITQ-37 (-ITV, 30-R), 15 ITQ-40 (-IRY, 16-R), 16 ITQ-43 (28-R), 17 ITQ-44 (IRR, 18-R), 18 ITQ-51 (IFO, 16-R), 19 and ITQ-54 (-IFU, 20-R), 20 etc. Very recently, the successful synthesis of a new germanosilicate zeolite, named NUD-1, possessing 18-ring channels, further enriches the extra-large pore zeolite family. 21 Significantly, the extra-large pore zeolites are promising in cracking heavy oils. 14 Using rational designed templates, with characteristics of bulky size, appropriate rigidity and proper C/N ratio, etc., is one of the key strategies for synthesizing the extra-large pore zeolites possessing novel zeolite topologies. 22 However, the complicated synthesis procedure, expensive cost, and sometimes high toxicity involved in synthesizing these templates may limit the large-scale industrial applications of the extra-large pore zeolites. Notably, Strohmaier and co-workers used tetraethylammonium (TEA) cations together with alkali metal as templates successfully prepared ECR-34 (ETR), containing 18-ring channel systems, 23 Lin and co-workers synthesized PKU-12 (-CLO, 20-R) using diisopropylethylmethylammonium as the template that was prepared from N, N-diisopropylethylamine and the highly toxic methyl iodide. 24 However, when the simple, cheap, and commercially available quaternary ammonium bases, such as tetraethylammonium hydroxide (TEAOH), tetrapropylammonium hydroxide (TPAOH), and tetrabutylammonium hydroxide (TBAOH), were used as the sole organic template, the maximum opening windows of the obtained zeolite frameworks is no more than 12-rings, such as zeolites MFI, 25* BEA, 26 SZR, 27 and MEL, 28 etc. Herein, with a series of the simple quaternary ammonium hydroxide TEAOH (∼ 8 Å), TPAOH (∼ 9 Å), and TBAOH (∼ 10 Å) 29 as the sole organic template, we have for the first time successfully synthesized the extra-large pore germanosilicate zeolites ITQ-33 (18R× 10R× 10R), ITQ-44 (18R× 12R× 12R), and NUD-1 (18R× 12R× 10R) by introducing