Zeolite synthesis in the presence of azonia-spiro compounds as structure-directing agents (original) (raw)
Related papers
1985
The synthesis, crystallization and structure o f heteroatom containing ZSM-5 type zeolite (M-ZSM-5) (Xu Ruren and Pang Wenqin (Plenary lecture) 27 Synthesis of ZSM-5 type zeolites i n the system (Na, K) 2 0-A1 2 0 3-Si0 2-H 2 0 without and with ΤPA Br (A. Nastro, C. Colella and R. Aiello) 39 Crystallization of ZSM-5 type zeolites from reaction mixtures free o f organic cations (Ü.M. Berak and R. Mostowicz) 47 Nature and structure o f high silica zeolites synthesized i n presence of (poly) alkyl mono-and diamines (Z. Gabelica, M. Cavez-Bierman, P. Bodart, A. Gourgue, and J.B. Nagy) 55 Factors influencing the crystal morphology o f ZSM-5 type zeolites (R. Mostowicz and J.M. Berak) 65 The influence of alkali metal cations on the formation o f silicalite in NH^OH-TBAOH systems (Tu Kungang and Xu Ruren) 73 Template variation i n the synthesis o f zeolite ZSM-5 (F.J. van der Gaag, J.C. Jansen and H.van Bekkum) 81 The synthesis o f high silica zeolites i n the absence of sodium ion
Chemistry - A European Journal, 2013
Dedicated to Professor Takashi Tatsumi on the occasion of his 65th birthday Introduction Zeolites have important applications in catalysis, adsorption, and ion-exchange processes as a result of their molecularsized micropores, which confer unique properties on these materials. [1] Over the past decade, various new zeolitic materials with either large (12-membered-ring, 12-R) or extralarge (> 12-R) micropores have been synthesized with the aid of bulky structure-directing agents (SDAs). [2-4] To date, over 200 different zeolite framework type codes (FTCs) [5] have been approved by the International Zeolite Association (IZA). The MCM-68 zeolite (FTC: MSE), first reported by researchers at Mobil Corporation in 2000, is a new type of three-dimensional zeolite with a 12 10 10-R channel system. [6] This zeolite has a characteristic structure in which a straight 12-R channel intersects two independent tortuous 10-R channels and, in addition, it possesses an 18-R 12-R supercage that is accessible only through 10-R channels. [7] These unique features of the MCM-68 zeolite have attracted attention because there are only a handful of acidic zeolites that contain three-dimensional channel systems with large pores. Zeolites of this type are known to exhibit unique acid-catalytic properties [8, 9] and are potentially useful as shape-selective catalysts for the alkylation of aromatics, [10-12] as well as for the production of propylene by naphtha cracking. [13] Their use as hydrocarbon traps has also been reported. [14] In addition, titanium-substituted MCM-68 has demonstrated performance superior to that of TS-1 ([Ti]-MFI) for the oxidation of phenol and olefins with H 2 O 2 as oxidant. [15] MCM-68 has been synthesized under hydrothermal conditions by using N,N,N',N'-tetraethyl-exo,exo-bicycloA C H T U N G T R E N N U N G [2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium diiodide (TEBOP 2+ (I À) 2) as the SDA. The gel composition window for the successful crystallization of pure MCM-68 is very narrow and the product is limited to a Si/Al molar ratio in the range of 9-12. We have previously overcome this limitation by employing the steam-assisted crystallization (SAC) method [16] to obtain a precursor of the pure silica version of the MSE topology (YNU-2P) or its stabilized microporous version (YNU-2). [17, 18] Even so, the current requirement for a crystallization period of 14 days or more during the synthesis of MCM-68 remains an important unresolved issue. Recently, however, researchers at the Universal Oil Products Company (UOP) [19] reported the synthesis of the UZM-35 zeolite, which has an identical topology to MSE but can be synthesized in only 5-9 days by using a processing temperature of 175 8C in conjunction with dimethyldipropylammonium hydroxide as the SDA. The synthesis of zeolites typically involves the conversion of an amorphous phase into a specific type of zeolite. In reality, though, the formation of a given zeolite proceeds through a process of gradual transformation. This sequential process begins with the amorphous phase, which undergoes a transition through a semi-stable form of the zeolite to the final stable zeolite product. [20, 21] This phenomenon suggests the possibility of an alternative synthetic strategy involving
Chemistry
The study on the synthesis of zeolites, including both the development of novel techniques of synthesis and the discovery of new zeolitic frameworks, has a background of several decades. In this context, the application of organic structure-directing agents (SDAs) is one of the key factors having an important role in the formation of porous zeolitic networks as well as the crystallization process of zeolites. There are various elements that are needed to be explored for elucidating the effects of organic SDAs on the final physicochemical properties of zeolites. Although SDAs were firstly used as pore generators in the synthesis of high-silica zeolites, further studies proved their multiple roles during the synthesis of zeolites, such as their influences on the crystallization evolution of zeolite, the size of the crystal and the chemical composition, which is beyond their porogen properties. The aim of this mini review is to present and briefly summarize these features as well as th...
A zeolite with interconnected 8-, 10- and 12-ring pores and its unique catalytic selectivity
Nature Materials, 2003
nature materials | VOL 2 | JULY 2003 | www.nature.com/naturematerials 493 Z eolites are built up by TO 4 tetrahedra (where T represents the central tetrahedrally coordinated atom) forming definite crystalline structures that enclose a large number of small cavities, which may be interconnected by a number of still smaller channels. These cavities and channels are highly uniform in size and shape within a specific zeolite material. Because the dimensions of the channels are such that they adsorb molecules of a certain size, these materials are known as molecular sieves, and are widely used in a variety of ways in industrial catalytic applications. Moreover, tailor-made host systems with designed topologies and adapted surface properties are an important prerequisite for supramolecular inorganic host-guest chemistry 1 . To date, the reported zeolite pore topologies of interest in catalysis were formed by uni-, bi-or tridirectional pore structures with the pores constructed by either 8-(small pores), 10-(medium pores) or 12-(large pores) membered rings (MRs) 2 .Two silica-based zeolites with a unidirectional system of 14MR pore apertures (extra-large pores) have been described (UTD-1 and CIT-5) 3,4 . Among the different structures available,the most successful zeolite catalysts up to now have been those containing either medium or large pores. However, it could be expected that a system containing both 12-and 10MR channels in the same structure could open possibilities for shape selectivity effects. The structure of a naturally occurring zeolite (boggsite), which has 10and 12MR windows bounding a three-dimensional channel system,has been described 5 , showing the possibility for those materials to be synthesized. Indeed, zeolites SSZ-26, SSZ-33 and CIT-1, which form a family of intergrown materials of two polymorphs 6-8 have been synthesized, and are formed by connected 12-and 10MR channels. However, this topology could be better described as a structure containing parallel 12MR channels that are perpendicularly connected by 10MR windows. Therefore, from the catalytic point of view, the diffusion properties of molecules through this zeolite structure will be mostly driven by the 12MR system 9 .Another zeolite,named NU-87,has connected pores with 10-and 12MR apertures, but in this case, only the 10MR pores are opened to the exterior 10,11 .A third zeolite,MCM-22 and its analogues SSZ-25, ERB-1 and PSH-3, have been reported, whose structures are formed by a 10MR system and large cavities delimited by 12MRs,but they are independent and the molecules cannot diffuse from one channel system to the other 12 .
A mechanistic study of the synthesis of zeolite SSZ-24
Microporous Materials, 1996
X-ray diffraction, elemental analysis, scanning electron microscopy, and 295i magic angle spinning (MAS), 1H-13C cross-polarization (CP) MAS and 1H-29Si CP MAS NMR spectroscopies are used to study SSZ-24 synthesis from aqueous silicate mixtures containing alkali and N,N,N-trimethyl-l-adamantammonium (TMAA +) cations. SSZ-24 only forms from mixtures prepared using fumed silica, KOH, and TMAAOH, with TMAA/Si > 0.15. SSZ-24 nuclei form through Van der Waals and coulombic interactions between the anionic silicate species and the TMAA ÷ cations in the gelatinous synthesis mixture. The results cannot distinguish whether SSZ-24 nuclei form in the liquid or solid phase of the synthesis mixture. No evidence was found for occlusion of the TMAA + cations in the solid phase of the gel prior to SSZ-24 crystallization, suggesting that the rates of zeolite nucleation and crystallization may be comparable. Computer simulations reveal that the non-bonded interactions between TMAA + and the SSZ-24 lattice are weaker than the non-bonded interactions between tetrapropylammonium (TPA ÷) cations and the silicalite-1 framework, which may explain why silicalite forms much faster than SSZ-24 when TPAOH is substituted for TMAAOH in the synthesis mixture.
Applied Sciences, 2021
The nature of organic structure directing agents (OSDAs) is of paramount importance in the final properties of zeolites, particularly the framework and porosity. Recently, the use of P-containing OSDAs has been employed for new zeolites, but there is little discussion compared to their analogues N-OSDAs. The main objective of this work is the characterization of pure silica MFI zeolite (silicalite-1) prepared by the dual-template route with tetrapropylammonium (TPA), tetrapropylphosphonium (TPP) cations, and mixtures thereof aiming to understand by advanced NMR methods how the nature of the organic influences the physico-chemical properties of the zeolite. Silicalite-1 has been successfully synthesized using the dual-template procedure with TPA and TPP molecules. Both OSDAs are incorporated into the zeolite without any specific preference, differently to that observed before for the TEA/TEP system, and homogenously mixed inside of the zeolite voids. The presence of TPP leads to the ...
Synthesis and characterization of the MCM-22 zeolite
Zeolites, 1995
MCM-22 has been synthesized as a unique phase and with good crystallinities in a range of different Si02/AI=O3 ratios using hexamethylenimine as a template. For Si02/AI=O3 ratios around 30, MCM-22 can be obtained as a pure phase and with good yields in a relatively broad range of OH/SiO2 ratios, although the efficiency in Si incorporation decreases with increasing pH. For low Al=O3 contents (SiOJAI203 /> 70) the sample becomes contaminated by ZSM-5. This contamination can be eliminated by lowering the crystallization temperature. If the synthesis is carried out under static conditions, ferrierite also appears in the crystallized sample. Upon calcination to eliminate the organic template, some dealumination occurs, while strong acid sites are formed, pyridine being accessible to all hydroxyl groups associated to framework AI. This together with the large void volume of the zeolite suggest the presence of a multidirectional system of channels where at least some of the channels are formed by large pores.
A Short Review on Synthesis, Characterization, and Applications of Zeolites
Advances in Materials Science and Engineering
The review emphasizes on synthesis, characterization, and application of zeolite. Zeolite is a hydrated aluminosilicate having a tetrahedral structural framework; it contains channels and cages which are occupied by exchangeable active metal ions and water molecules. Zeolite was synthesized through different synthesis methods, particularly, hydrothermal and green synthesis methods. The review also has tried to address the structure of zeolite such as morphology, functional group, and particle size using different characterization methods as reported via different authors. The characterization results verify that zeolite shows many unique properties such as uniform pore size, acidic properties, thermal stability, mobile extra cation, hydrophilicity, and hydrophobicity. These lead to a number of applications in catalysis, water purification, adsorption, and agriculture.
Progress in zeolite synthesis promotes advanced applications
Microporous and Mesoporous Materials, 2014
This article outlines the importance of zeolite synthesis and their unique physicochemical characteristics promoting advanced applications. The main strategies for preparation of zeolites including organic-template assisted, organic-template free and alternative procedures are considered for synthesis of crystallites offering control and fine-tuning of their properties. Besides, rational design of zeolites with pre-determined structure, porosity, size, morphology, and composition are more viable by studying carefully the chemical and physical parameters controlling the zeolite synthesis and understanding the crystallization mechanism. Finally, a particular attention to the preparation of zeolites with nanosized dimensions and their utilization in innovative applications including photovoltaic, medicine and holographic sensors are presented.