Zeolite SAPO

Immobilized nitrile hydratase Mixed metal oxides Zeolites, SAPO Zeolite... 

B MAS NMR yields quantitative information about the incorporation of boron into zeolite frameworks. H MAS NMR and IR spectroscopy show that OH groups introduced into the framework by boron substitution are non-acidic. 2D proton spin diffusion measurements of the zeolite SAPO-5 reveal that defect OH groups are adjacent to acidic bridging hydroxyl groups and do not exist in an amorphous phase. Strongly adsorbed water molecules in mildly steamed zeolites H-Y can be explained by Lewis sites. 

Principal Characteristics. - Large-pore molecular sieves like mordenite, X and Y zeolite, SAPO-5, MeAPO-5, and MAPO-5 have also been used as catalysts for methanol conversion into olefins. 

An interesting example is the conversion of methanol to hydrocarbons catalyzed by the zeolitic SAPO-34 material[ °l This microporous AlP04-based material has the structure of chabazite. The protonic sites are similar to those in the zeolite, but of slightly less intrinsic acidity because of their embedding in the AIPO4 structure. The formation of a C-C... 

It is the aim of the present paper to review the synthesis of a selected number of microporous materials which have more recently attracted the attention of zeolite scientists. The following selection criteria were appUed (i) the review is restricted to aluminosiUcates, hence, isomorphously substituted zeolites, SAPOs, MeAPOs and the Hke are not considered, (ii) crystalline microporous aluminosilicates are exclusively dealt with, the synthesis of ordered mesoporous molecular sieves (i.e. MCM-41) is not discussed and, (iii) especially those zeolites have been selected which, based on their particular structural or physicochemical properties, have a certain potential for appHcations in catalysis or adsorption. Some readers might miss such important and interesting zeolites like Beta, EMC-2, ZSM-12, etc. However, although there is still intensive research going on in the synthesis of these zeoHtes, their main synthesis principles have been summarized earUer [5,6] and will therefore not be discussed here. 

Recently, Yu and coworkers have successfully controlled the crystal size and morphology of the silicoaluminophosphate zeolite SAPO-34 (CHA) under microwave irradiation in the system of AljOj-P Oj-SiOj-TBAOH-H O by studying the synthetic factors such as the silica source, water content, crystallization time, and aging time [52]. Microwave-assisted synthesis proved to be an efficient approach to produce nanosized zeolite crystals [53]. As a comparison to traditional hydrothermal synthesis at 200°C for 72 h, the microwave-assisted synthesis of SAPO-34 needed only 1 h at 200°C, which greatly reduced the reaction time. 

Figure 1. SEM images of the zeolite crystals under investigation a) CrAPO-5 b) SAPO-34 c) SAPO-5 and d) ZSM-5.

In order to illustrate the general applicability of the methodology we have extended our approach to other large zeolite crystals, such as SAPO-34, SAPO-5 and ZSM-5. Our study on the rhombic SAPO-34 crystals reveals a four-pointed star fluorescence pattern at 445 K, which is transformed into a square-shaped feature at 550 K. This is illustrated in Figure 4a. Confocal fluorescence slices, summarized in Figures 4b-d, recorded at different temperatures show the cubical pattern, which proceed from the exterior of the crystal inwards. Both observations are consistent with a model which involves six components of equal tetragonal pyramids as illustrated in Figure 3b. 

In this paper, three zeolitic materials were used silicalite-2, pure silica ZSM-11 with MEL framework, synthesized according to Bibby et.al. [7] zeolite A synthesized via the Chamell hydrothermal method [8] SAPO STA-7 was synthesized according to Wright et. al. [9]... 

In Ag-SAPO-ll/C2H4 zeolite the EPR at 77 K shows the spectra of Ag° atoms and C2H5 radicals. After annealing at 230 K those species disappeared and then an anisotropic EPR sextet was recorded. Based on DFT calculation the structure of complex was proposed in which two C2H4 ligands adopted eclipsed confirmation on either side of the Ag atom. As a result the overwhelming spin density is localised on ethylene orbitals. 

The zeolite structure also plays a large role in RC product distribution. Weitkamp et al.62 conducted experiments with Pt/HZSM-5 catalysts, which have very narrow pore sizes when compared with other zeolites, such as USY or SAPO. They found that c is I trans-1,3-dime thylcyclopentane was formed, while 1,1 and 1,2-DMCP were not. This indicates that the more oval shaped 1,3-DMCP was able to diffuse through the pores, while the more bulky and spherical isomers were not, and thus not seen in the product distribution. In short, when compared with dealkylation to cyclohexane, ring contraction of MCH is a more effective pathway to yield higher ON products. However, in order to further improve the ON, ring-opening of the RC isomers may be necessary, as shown below. 

Saponite, idealized formula, 33 337 SAPO-n-zeolite-supported Pd catalysts, 39 208 Sarin, reaction with cyclohexaamylose, 23 237 Saturation in ESR, 22 280 SbF 37 168-172... 

The silicoaluminophosphate (SAPO) family [30] includes over 16 microporous structures, eight of which were never before observed in zeolites. The SAPO family includes a silicon analog of the 18-ring VPI-5, Si-VPI-5 [31], a number of large-pore 12-ring structures including the important SAPO-37 (FAU), medium-pore structures with pore sizes of 0.6-0.65 nm and small-pore structures with pore sizes of 0.4-0.43 nm, including SAPO-34 (CHA). The SAPOs exhibit both structural and compositional diversity. 

In the metal aluminophosphate (MeAPO) family the framework composition contains metal, aluminum and phosphorus [27]. The metal (Me) species include the divalent forms of Co, Fe, Mg, Mn and Zn and trivalent Fe. As in the case of SAPO, the MeAPOs exhibit both structural diversity and even more extensive composihonal variation. Seventeen microporous structures have been reported, 11 of these never before observed in zeoUtes. Structure types crystallized in the MeAPO family include framework topologies related to the zeolites, for example, -34 (CHA) and -35 (LEV), and to the AIPO4S, e.g., -5 and -11, as well as novel structures, e.g., -36 (O.Snm pore) and -39 (0.4nm pore). The MeAPOs represent the first demonstrated incorporation of divalent elements into microporous frameworks. 

Martens, J.A., Mertens, M Grobet, P.J., and Jacobs, P.A. (1988) Synthesis and charaderization of siJicon-rich SAPO-5, in Innovation Zeolite Mater. Sci. (eds P.J. Grobet, W.J. Mortier, E.E. VansanL and G. Schulz EHoff), Stud. Surf Sd. Catal. 37, Elsevier, Amsterdam, pp. 97-105. 

Synthetic forms Beryllophosphate X, Li-LSX, LZ-210, SAPO-37, siliceous Na-Y, zeolite X (Linde X), zeolite Y (Linde Y), zincophospate X... 

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