Aluminum phosphate molecular sieve

When this method is applied to cyclohexanone, it produces a mixture of 50% adipic acid, 19% glutaric acid, and 3% succinic acid. Further work is needed to steer the reaction to a high yield of the desired adipic acid. A chromium aluminum phosphate molecular sieve has been used with oxygen and a catalytic amount of a hydroperoxide to convert cyclohexane to a mixture of 48% cyclohexanone, 5% cyclohexanol, 6% cyclohexanehydroperoxide, and 40% adipic acid, at 10% conversion. The catalyst could be reused four times without loss of activity.205 Presumably, the products other than adipic acid could be recycled to the next run. The authors do not give the selectivity at higher conversions. Ideally, one would like a similar system that would give only adipic acid at 100% conversion. 

Potassium fluoride on alumina is a solid base.69 (It forms potassium hydroxide by exchange of fluoride for hydroxyl groups on the surface of the alumina.) An example of its use is given by Reaction 6.21.70 It has also been used without solvent in the Tishchenko reaction of benzaldehyde to give benzyl benzoate if 94% yield.71 Potassium fluoride on an aluminum phosphate molecular sieve was a weaker base in the isomerization of 1 -butene.72... 

A milestone was achieved with the discovery of aluminum phosphate molecular sieves [1]. These compounds have neutral frameworks of very low acidity. Thus, their use as catalysts and to some extent as sorbants is limited. However, it was subsequently shown that silicon could be incorporated into the aluminum phosphate framework [3-4] (SAPO s). This discovery was followed in short order by introduction of many metals (Mg2+, Mn +, Fe -, Cq2+, Zn2+) [5-6] into the framework by isomorphous... 

The discovery of aluminum phosphate molecular sieves has fueled the search for new sieve like materials. This search has been amply rewarded. Newsom and Vaughan [13] were able to prepare new gallosilicate phases and gallophosphates have also been prepared [14]. One of the most interesting and startling discoveries is that of zincophosphate and beryllophosphate molecular sieves [15]. They can be prepared under very mild conditions [16] and have structures which closely resemble those of aluminosilicate zeolites [16-17]. These compounds have frameworks [(Zn02)(P02)] which are isoelectronic with the aluminosilicate framework... 

Aluminum phosphate molecular sieve fibers were obtained by Yates et al. [334] by hydrothermal treatment (180 C/6 h) of a microemulsion system containing (a) toluene, (b) n-butanol,(c) cetylpyridinium chloride, CPC (surfactant) and (d) an aqueous phase made up of aluminum triisopropoxide, phosphoric acid, hydrofluoric acid and triethylamine in water. The treatment yielded long fibers (200-300 nm wide, 15-30 im long), confirmed by X-ray powder diffraction to be AIPO4-5 with preferred orientation. 

VPI-5 is an aluminum phosphate molecular sieve that contains extra-large pores circumscribed by 18-membered oxygen rings with a free diameter of approximately 1.2 nm. VPl-5 is characterized by the absence of an electric field. 

A series of aluminum phosphite and phosphite-phosphate molecular sieves were synthesized by using P (III) (phosphorous acid) partly or completely replaced P (V) (phosphoric acid) as the source of phosphorus materials. DPA (di-n-propylamine), TEA (triethylamine) and CHA (cyclohexylamine) were used as the template respectively. SEM photographs showed the shapes of these crystalline inorganic solid. It was very interesting that a kind of aluminum phosphite NKX-4 can be synthesized with or without template. 

These structures are unique for several reasons. First, they represent three new multidimensional 12-MR systems, which are rare even among zeolites. Second, the amount of framework substitution by metals such as Mn2+ and Mg2+ was unknown prior to this series. Also, the ease of forming both gallium and aluminum phosphates appear to be comparable. Finally, it would appear the charge-matching approach has proven to be a successful strategy for the synthesis of new molecular sieves. It is not clear whether these materials are thermally or hydrothermally stable but they do represent novel pore structures that should impart some unusual properties. 

Chen, C. and Jehng, J. (2003) Effect of synthesis pH and H20 molar ratio on the structure and morphology of aluminum phosphate (AlPO-5) molecular sieves. Catal. Lett., 85 (1-2), 73-80. 

Conditions for A1PQ4-H3 and MCM-1 Synthesis. From previous section it cSh Be concluded that as far as the coordination of A1 is concerned, AlPC -EU is a hybrid between the aluminum phosphate hydrates like variscite and metavariscite and the aluminophosphate molecular sieves. It can be expected that the synthesis conditions under which it crystallizes will also be intermediate between those of hydrates and molecular sieves. Literature together with the present new data seem to confirm this. 

The neutral molecular sieve, aluminum phosphate (ALPO, Chapter 10) can also serve as a shape selective support for metal catalysts. These catalysts are normally prepared by the incipient wetness process followed by appropriate drying and reduction procedures. Fig. 13.19 illustrates the selectivity observed using a Ni/ALPO catalyst to hydrogenate a mixture of styrene and a methyl styrene (Eqn. 13.13). The rates of hydrogenation of cyclic alkenes over a Rh/ALPO catalyst decreased in the order cyclopentene cyclohexene > cycloheptene > cyclooctene but no selectivity was observed in a competitive hydrogenation of a mixture of cyclohexene and cyclooctene. 75... 

The alkylation of toluene with methtmol at 400°C over H-ZSM-5 gave, at 36% conversion, a 69% selectivity for xylene formation, of which 27% was the para isomer. 2 Aluminum phosphate based molecular sieve catalysts such as CoAPO gave a lower conversion but higher selectivities for p-xylene formation. 2 Metallosilicates such as As-silicate having a ZSM-5 structure produced an 82% selectivity for p-xylene at 21% conversion. 

There are other microporous solids that are not aluminosilicates hence, they are not zeolites. The titanosili-cates, such as titanium silicalite (TS-1), which are selective catalysts for oxidations, are discussed in Chap. 4. Much work is going into extending these findings to materials with larger pores to accommodate larger substrates for oxidation. Molecular sieves also include the aluminum phosphate (AIPO) family.145 These have been modified by inserting a variety of cations into them, including... 

Mesoporous molecular sieves having chemical compositions different from silicates and alumina including aluminum phosphates, various transition-metal oxides, chalcogenide and nitridic framework, metals, and carbons were recently nicely reviewed by Schiith [79]. 

The recent syntheses of zeolitelike crystalline silicas, which contain infinitesimal amounts of aluminum, and the more recent syntheses of zcolitelike crystalline aluminum phosphates, chemical analogues of crystalline silica, have further confused the zeolite versus molecular sieve question. The conservative position contends that these molecular sieve crystals are not zeolites on two counts They are not aluminosilicates, and they do not contain exchangeable cations. Furthermore, some of the relatively high silicon-containing materials have an average of less than one... 

Although the title of this book, Perspectives in Molecular Sieve Science, avoids the zeolite definition controversy, a large majority of the research reported here centers on traditional zeolites. Only three of the 39 chapters comprising the book deal with materials that are clearly nonzeolitic Two cover clay-type derivatives, and one deals with carbon molecular sieves. Not surprisingly, interest in these materials lies in their possible use as catalysts. Only four chapters present work on mineral zeolites and three on aluminum phosphate-type molecular sieves. Two of those chapters are by workers from Union Carbide, the laboratory that did the pioneering work in this field. It is surprising that other workers have not submitted papers on the aluminum phosphates, but perhaps this situation indicates that although much activity may be underway, laboratories hesitate to publish until patent positions are established in this potentially lucrative area. Union Carbide s synthetic faujasites (zeolites X and Y) and zeolite A receive the most attention, while ZSM-5-class materials are accorded more attention than zeolite A alone. This reflects the important roles that zeolites X and Y and ZSM-5 materials have already played as catalysts. 

Structure and Catalysis of Aluminum Phosphate Type Molecular Sieves. Ono, Yoshio Hyomen, 27(11), 857-64, 1989. 

Aluminum Phosphate-Based Molecular Sieves. Although still in the early stages of development, aluminum phosphate-based molecular sieves have shown great promise as a microporous catalyst and an adsorbent material. They were first reported in 1982 with a neutral aluminum phosphate (AlP04)-n framework (15), Si, other metals (such as Be, Mg, Ti, Mn, Cr, Fe, Co, and Zn), and other elements (such as Li, B, Ga, Ge, and As) have subsequently been incorporated into the AIPO4 framework these substitutions have allowed additional applications for the catalyst. Some of the applications reported are catalytic dewaxing, hydrocracking, methanol conversion, and toluene alkylation. 

Aluminum phosphate based molecular sieves, role in environmentally benign synthesis of chemicals, 128 Amines, organic isocyanate generation, 49-57... 

The abihty of the aluminiun to attain six coordination when associated with phosphate ligands results in the aluminophosphate molecular sieves exhibiting some unusual thermal properties. As discussed previously, D Yvoire s (n = 1 -6) materials were hydrated species with some of the aliunimun in octahedral coordination, four points attached to the phosphate in the framework, and the two remaining coordination sites occupied by molecules of water. The labihty of these water molecules is dependent on the structure. AIPO4S prepared fi-om organic-containing systems can also exhibit expanded coordination around the aluminum. 

The second most important class of molecular sieves besides the alumo-silicates are without any doubt the alumophosphates and their derivatives containing elements other than aluminum and/or additional elements in the framework. Chapter 6 authored by R. Szostak is a review covering the synthesis of these molecular sieve phosphates. 

In particular, Alberti et al. (1991) proposed zeolite-based sensors for detection of hydrocarbons such as butane and Balkus et al. (1997) used thin film aluminophosphate (AlPO)-5 molecular sieve as the dielectric phase in a capacitance-type chemical sensor for CO and CO. AlPO-n is a family of phosphorus molecular sieves which, similar to zeolites, have ordered molecular-sized pores. The AlPO-5 structure used for the dielectric layer consists of four- and six-membered rings of alternating phosphate and aluminum ions bridged by oxygen. These rings are arranged to produce one-dimensional channels 0.73 nm in diameter. The properties of AlPO-n are reviewed in detail by Ishihara and Takita (1996), and one of the attractive properties of these materials is their heat stability. The properties of zeolites as they relate to zeolite-based gas sensors are discussed in a special section in Vol. 2. 

Various metal complexes such as metal-phthalocyanines, metal-salenes or Ru-pyridyl complexes were incorporated in molecular sieves such as cavity-structured zeolites (faujasites, supercages with 1.3 nm diameter), channel-structured aluminum phosphates... 

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