Molecular sieves AIPO

In this study, the structure of the vanadium species supported on AIPO -S molecular sieve has been studied by X-ray diffraction, infrared, diffused reflectance, and EPR spectroscopy, temperature programmed desorption, and their properties compared with those of VAPO -S. 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

Takahashi et al. [25] reported that the dispersed tetravalent vanadium (l 7/2) showed a hyperfine structure but broad band could be observed in the agglomerated vanadium. Miyamoto et al. [8] and Jhung et al. [7] reported that EPR spectra of VAPO -S showed hyperfine structure. Miyamoto et al. [8] suggested that the hyperfine structure indicated atomically dispersion of vanadium in VAPO -S molecular sieve, in other words, vanadium was substituted in the framework of AIPO -S. 

A-, X-, Y-, and AIPO-5-molecular sieves and synthetic mordenite Se Predominantly trigonal helical chains of selenium were incorporated into the zeolite channels 559... 

The silico-aluminophosphate molecular sieves represent a new class of microporous solid acid catalyst. The framework of the aluminophosphate molecular sieves is formed by tetrahedral arrangements of equal numbers of AIO4 and PO4 tetrahedra, with AT+ and alternating. The framework of AiPO is neutral. However, the AIO4 or/and PO4 may be substituted... 

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... 

Fig. 5. Dye moleculel-ethyl-4-[4-(p-dimethylaminophenyl)-l,3-butadienyl]-pyridiniumperchlorate inserted in the one-dimensional channel of AIPO-5 molecular sieve. Ref. 27b...

The acidity of metal-substituted, alumi nophosphate molecular sieves is not well understood [1]. There is no clear picture of what site concentrations are present in these materials, how strong the sites are, or whether one should even think in terms of discrete sites. The effects of various calcination and pretreatment conditions are also difficult to quantify, in this paper, we have tried to address these questions by examining the adsorption of simple amines in materials formed by the substitution of Mg, Co and Si into an AIPO-5 structure. 

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