Zeolites aluminophosphates

Encapsulation Zeolites, aluminophosphates, in situ (Nitro)phthalocyanines Meyer et al. (123), Parton et al. (124-126)... 

Besides MeAPO, several heterogeneous systems have been proposed for the oxidation of cydohexane vith various oxidants [2c], but almost all of them yield 01/ One as the main reaction products, with AA being only a minor product. Heterogeneous catalysts can be either oxides or metal cations and complexes incorporated on inorganic matrixes, such as active carbon, zeolites, aluminophosphates or conventional supports such as alumina and silica. The activity of these systems is greatly affected by the choice of solvent, which determines the polarity of the medium. In addition, the hydrophobicity of the support is important, since a hydrophobic environment rapidly expels the oxidized products from the reaction zone. When oxygen is used as the oxidant, these systems often need small amounts of hydroperoxides as co-catalysts. 

Regarding their use as cracking and isomerization catalysts, bulk oxides such as clays and amorphous silica-aluminas have been widely displaced by molecular sieve compounds (e.g., zeolites, aluminophosphates), whose well-defined pore structures generally offer higher selectivity and flexibility. Nevertheless, bulk oxides continue to be used for various cracking and isomerization applications in the petroleum industry. 

We focus here specifically on reactions in solid organic inclusion componnds, for which the host structure is constructed from the crystal packing of organic molecnles. However, we note in passing that a major area of research that exploits many of the uniqne facets of reactivity in solid host-guest systems is heterogeneous catalysis, and the importance of microporous inorganic host structures (such as zeolites, aluminophosphates, and related families of materials) in this field has been well documented elsewhere. ... 

The papers by Conner, Kaneko, Rouquerol, Unger and their co-workers underline the importance now attached to the determination of physisorption isotherms at very low levels of surface coverage or fractional micropore filling, i.e. in the region of very low p/p . Such high resolution adsorption (HRADS) measurements have been shown to be especially useful for the characterization of the adsorptive properties of zeolites, aluminophosphates and molecular sieve carbons. 

Additional to tire aluminosilicate-based zeolites, a number of otlier crystalline microporous tliree-dimensional oxides have been syntliesized [25]. Most prominent among tliese are tire aluminophosphates (ALPO series) [26,... 

The same periodic structures can also be formed from alternating AIO4 and PO4 tetrahedra the resulting aluminophosphates are not called zeolites but AlPOs. Zeolites are made by hydrothermal synthesis under pressure in autoclaves, in the presence of template molecules such as tetramethylammonium, which act as structure directing agents. 

Aza macrocycles have also been used as templating agents in the formation of zinc and other metal cation-containing aluminophosphates via hydrothermal synthesis.705 The zeolite-like structures have been formed in the presence of cyclam- and hexaaza-based macrocycles. 

Aluminide alloys, 13 530 Aluminium powder, 10 738. See also Aluminum entries Aluminohydride derivatives, 13 624 Aluminohydrides, 13 621-624 Aluminophosphate zeolites, 14 98 Aluminosilicate gels, 16 830 Aluminosilicate glass, matrix for... 

Zeolite structures typically consist of silicon and aluminum finked by tetrahedrally coordinating oxygen atoms. However, similar structures as found for these aluminosilicates can be formed by substitution of the aluminum by other elements (e.g., Ga in gallosilicates or Ti in titanosilicates). Even the substitution of both Si and A1 is possible, as for example in aluminophosphates or... 

AEL (n defines a number indicating a specific material) zeolite structure types aluminophosphate eleven (A1P04-11)... 

The past nearly six decades have seen a chronological progression in molecular sieve materials from the aluminosilicate zeolites to microporous silica polymorphs, microporous aluminophosphate-based polymorphs, metallosilicate and metaHo-phosphate compositions, octahedral-tetrahedral frameworks, mesoporous molecular sieves and most recently hybrid metal organic frameworks (MOFs). A brief discussion of the historical progression is reviewed here. For a more detailed description prior to 2001 the reader is referred to [1]. The robustness of the field is evident from the fact that publications and patents are steadily increasing each year. 

The characteristics of aluminophosphate molecular sieves include a univariant framework composition with Al/P = 1, a high degree of structural diversity and a wide range of pore sizes and volumes, exceeding the pore sizes known previously in zeolite molecular sieves with the VPI-5 18-membered ring material. They are neutral frameworks and therefore have nil ion-exchange capacity or acidic catalytic properties. Their surface selectivity is mildly hydrophilic. They exhibit excellent thermal and hydrothermal stability, up to 1000 °C (thermal) and 600 °C (steam). 

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. 

Flanigen, E.M., Lok, B.M., Patton, R.L, and Wilson, S.T. (1987) Aluminophosphate molecular sieves and the periodic table, in New Developments in Zeolite Science and Technology, Proc. 7th Inti. Zeolite Conf, Tokyo, 1986 (eds Y. Murakami, A. Ijima, and J.W. Ward) Elsevier, Amsterdam, pp. 103-112. 

The crystal structures of several metal aluminophosphate molecular sieves, in Innovation Zeolite Mater. Sci. (eds P.J. Grobet, W.J. Mortier, E.F. Vansant, and G. Schulz Eklofi), Stud. Surf. Sci. Gatal., vol. 37, Elsevier, Amsterdam, pp. 269-279. 

Similarly, reactive oxide mixtures are also used to synthesize aluminophosphate molecular sieves, usually starting from phosphoric acid along with the addition of alumina and silica sources analogous to those used in zeolite synthesis with a notable exception alkylammonium salts and amines were ultilized in structure-direchng and space filling to the exclusion of alkali hydroxide solutions and alkali metal salts. 

Beale, A.M. and Weckhuysen, B.M. (2007) Understanding the crystallisation processes leading to the formation of microporous aluminophosphates, in Zeolites to Porous Materials-The 40th Anniversary of International Zeolite Conference, Studies in Surface Science and Catalysis, vol. 170, Elsevier Science Publishers B V, Amsterdam,... 

Makarova, M.A., Ojo, A.E., Karim, K., Hunger, M., and Dwyer, J. (1994) ETIR study of weak hydrogen bonding of Bronsted hydroxyls in zeolites and aluminophosphates./. Phys. Chem.,... 

The catalysts for xylene isomerization with EB dealkylahon are dominated by MFI zeolite. The de-ethylation reaction is particularly facile over this zeolite. There have been several generations of catalyst technology developed by Mobil, now ExxonMobil [84]. The features in their patents include selectivation and two-catalyst systems in which the catalysts have been optimized separately for deethylation of EB and xylene isomerization [85-87]. The crystallite size used for de-ethylation is significantly larger than in the second catalyst used for xylene isomerization. Advanced MHAI is one example. The Isolene process is offered by Toray and their catalyst also appears to be MFI zeoUte-based, though some patents claim the use of mordenite [88, 89]. The metal function favored in their patents appears to be rhenium [90]. Bimetallic platinum catalysts have also been claimed on a variety of ZSM-type zeolites [91]. There are also EB dealkylation catalysts for the UOP Isomar process [92]. The zeolite claimed in UOP patents is MFI in combination with aluminophosphate binder [93]. 

Many books, reviews and treatises have been pubUshed on related subjects [1-7]. Thus the objective of this chapter is the deUneation of the key features of the catalytic surface and the process conditions which enable better control of the reaction pathways for more efficient and environmentally friendly processes and minimal utiHzation of precious natural resources. As it stands today, hundreds of known framework types have been synthesized and scaled-up [8], but only a handful have found significant application in the hydrocarbon processing industries. They are zeolite Y and its many variants, ZSM-5, Mordenite and zeohte Beta. Other very important crystalline materials (including aluminophosphates (ALPOs),... 

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