Aluminophosphates AlPO

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,... 

Other materials, closely related to zeoHtes, with zeo-type structures are silico-aluminophosphates (SAPOs) and aluminophosphates (ALPOs) [6]. 

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),... 

The acidity of thermally stable mesoporous aluminophosphates (AlPO) and sili-coaluminophosphates (SAPO) has also been stndied by microcalorimetry [245]. By contrast with microporous crystalline alnminophosphate molecnlar sieves, mesoporous compounds are amorphous and characterized by Al/P ratios greater than 1. These particularities are responsible for a strong Lewis acidity, making these mesoporous materials more acidic than the microporons analognes, with an amonnt of strong acid sites that increases with the silicon content. 

Hydrogen uptake at 77 K and 0.1 MPa have been studied in some aluminophosphate (AlPOs) molecular sieves [149], These materials are produced when the Si, located in tetrahedral sites, is... 

Phosphorus. Previous P solid-state NMR studies of SAPO materials have detected only a single type of local environment for phosphorus T-atoms four aluminum second nearest neighbors as in a pure aluminophosphate (ALPO ) material (3,4). This environment is illustrated in Figure 1. The NMR chemical shifts from this environment t)q)ically range from -25 to -35 ppm. 

The entrapment-type nanocomposites can be prepared from zeolites and they are of two types zeolite-inorganic and zeolite-organic. Zeolite crystals are three-dimensionally linked network structures of aluminosilicate, aluminophosphate (ALPO), and silicoaluminophosphate (SAPO) composition and are porous, the pores being in the range of 2.8 to 10 A. Many of the highly siliceous, ALPO, and SAPO zeolites have been synthesized using organic templates such as tetrapropyl... 

Fig. 7 Sheared 3QMAS NMR spectrum of microporous aluminophosphate AlPO-40 recorded at 9.4 T. The lengths of the first and second hard pulses were 2.5 ps and 0.8 ps, (Ri=100 kHz). The soft pulse kHz) length was 9 ps. 200 data points (240 transients...

The increasingly indispensable role of atomistic and quantum mechanical simulations in inorganic crystallography is perhaps no more strikingly illustrated than in the field of silicates and zeolitic materials. The two classes of material with which we shall be concerned in this chapter, namely microporous zeolites (including both aluminosilicate-based materials and their sister compounds, the aluminophosphates (ALPOs)), and the dense silicate materials and related oxides which constitute the bulk of the Earth s mantle, have in common the fact that their structural properties may be difficult to determine by conventional experimental means. Yet highly detailed and accurate structural information is critical in understanding the properties of both these important types of material. 

Useful zero thermal expansion composites are made by combining materials that show the unusual property of negative thermal expansion (i.e. contraction) with normal (positive) expansion materials. Examples of phosphates showing negative thermal expansion are the diphosphate-divanadate solid solutions ZrP2 xVx07 and the microporous aluminophosphate AlPO-17 which shows a particularly large effect. 

Diffuse reflectance IR spectroscopy (DRIFT) was, furthermore, successfully employed in studying molecular sieves of the new generation [957] such as aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs). Thus, Zscherpel et al. and Loeffler et al. [563,564] studied by DRIFT the range of fundamental OH stretching, OH deformation and framework vibrations of AIPO4-18 (upon decomposition of the template, tetraethylanunonium hydroxide), the fundamental and combination vibrations of hydroxy groups of SAPO-5 and SAPO-17 as well as the framework region of SAPO-34. In the latter case a comparison was made with the transmission spectrum. 

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. 

Al and P solid-state NMR spectra obtained at high field for the aluminophosphate AlPO-36 show that the hydration process produces both 5- and 6-coordinate A1 sites. Al MQ MAS spectra of the hydrated form show at least four tetrahedral aluminium sites, as well as one octahedral and one five coordinate site. ... 

A series of mesostructured aluminophosphate (AlPO)-based lamellar materials have been characterised by several solid-state NMR techniques. The average number of A1 atoms and identify the nature of other ancillary groups in the second coordination sphere for each P site was estimated. A combination of several dipolar coupling-based P/ Al double-resonance techniques e.g. TRAPDOR, REDOR, and HETCOR as well as H P CP can provide more detailed structural information regarding the local environments of P and A1 atoms in AlPO-based mesostructured materials, which is not readily available from straightforward P and Al MAS experiments. ... 

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