The Structure of Zeolite and Aluminophosphate Molecular Sieves

Zeolites and other molecular sieves are microporous crystalline solids whose main uses are in catalysis, ion-exchange reactions and as adsorbents. Their crystalline structures and different ways of identification of molecular sieve structure are reviewed, together with a short introduction into the catalytic activity of these materials. Synthesis and structural overview of aluminophosphates, a new and fast-growing family of microporous materials, are presented and strategy for introducing different metal atoms into aluminophosphate framework is discussed. These chemical framework modifications lead to a broad range of structure types and offer a nearly unlimited number of design parameters for the tailoring of catalityc and adsorptive properties of aluminophosphate materials. Our results in the areas of synthesis and X-ray diffraction structural characterization of metal-substituted aluminophosphates are reviewed

Recent Developments in Zeolite-like Materials Synthesis and Characterisation

In the last few years considerable effort has been directed at the targeted synthesis of zeolites and zeolite-like microporous materials with predetermined physical and catalytic properties. With new computational techniques, it has become possible to design templates for the synthesis of specific microporous structures with desired pore siže and connectivities. With regard to zeolite-like materials, much attention has been focused on transition metal containing systems, like zincosilicates, titanosilicates and various metalloaluminophosphates with a potential to generate specific redox conditions, in addition to Br0nsted and Lewis active catalytic centres. Experimental determination of subtle structural features such as the nature and position of the catalytically active metal sites, and the location, orientation and disorder of templates, metals or complexes within the microporous hosts has become possible using new characterisation techniques, mostly based on X-ray diffraction and the use of synchrotron and neutron radiation sources. In situ studies of the kinetics of nucleation, crystal growth and phase transitions or catalyst activation and operation at elevated temperatures have remarkably benefited from the new high-flux and well-collimated third-generation synchrotron radiation sources, and from the advances in the X-ray detector design and data handling

A Study of the Mn, Co and Ni Environment in the As-synthesized and Rehydrated-calcined Aluminophosphate with Chabazite-like Topology

Diffuse-reflectance spectroscopy (DRS), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods are applied to an investigation of Mn, Co and Ni local environments in MnAlPO, CoAlPO, and NiAlPO materials with chabazite-like topology. For all three products, insertion of the transition metals into tetrahedral Al-sites has been found. Calcination and rehydration of the as-synthesised materials cause a change of the oxidation number and co-ordination geometry of Mn and Co, while the oxidation and co-ordination number of Ni remain unaffected

Isomorphous Substitution of Framework Atoms by Titanium in VPI-5 Aluminophosphate Molecular Sieve

Extra-large pore aluminophosphate molecular sieve TiVPI-5 was synthesised hydrothermally in the presence of di-n-butylamine and transformed by the calcination process at 500 °C to a large pore TAPO-8. Incorporation of titanium(IV) into VPI-5 framework was studied by elemental and thermogravimetric analyses, combined with X-ray Absorption Near Edge Structure (XANES) spectroscopy and UV-VIS absorption spectroscopy. We found that titanium(IV) incorporated in TiVPI-5 isomorphously substitutes framework aluminium on octahedral sites and that it is not present in the structure in the form of TiO2 anatase. In situ IR measurements of pyridine adsorption/desorption were used to check the presence of catalytically active centres in the product resulting from titanium incorporation into the VPI-5 framework. Weak Lewis and Brønsted acid sites were found in small amounts in the calcined product TAPO-8

New two-component water sorbent CaCl2FeKIL2 for solar thermal energy storage

) and similar mesopore dimensions as the matrix. The maximum water sorption capacity of FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix. Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40°C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite

A Study of the Mn, Co and Ni Environment in the As-synthesized and Rehydrated-calcined Aluminophosphate with Chabazite-like Topology

Diffuse-reflectance spectroscopy (DRS), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods are applied to an investigation of Mn, Co and Ni local environments in MnAlPO, CoAlPO, and NiAlPO materials with chabazite-like topology. For all three products, insertion of the transition metals into tetrahedral Al-sites has been found. Calcination and rehydration of the as-synthesised materials cause a change of the oxidation number and co-ordination geometry of Mn and Co, while the oxidation and co-ordination number of Ni remain unaffected

The Influence of Manganese and Silicon on Some Physicochemical Properties of Aluminophosphates Having the Sodalite Structure

Aluminophosphate and silicoaluminophosphate materials of the sodalite structure type with manganese have been synthesized. A comparative study of A1PO4-20, AlPO4-20(Mn), SAPO-20, and SAPO-20(Mn) properties has been carried out by using the X-ray powder diffraction analysis, SEM, qualitative EDAX-micro analysis, chemical and thermal analysis, IR, EPR and diffuse reflectance spectroscopy. Chemical modification of AIPO4-2O with manganese and silicon leads to changes in the cubic unit cell parameters and in the thermal properties. The EPR and DRS data for as-synthesized AlP04-20(Mn) and SAPO-20(Mn) materials show the presence of octahedrally coordinated non-framework Mn, while the unit cell parameter data and the thermal behaviour of the samples are not so conclusive regarding the location of Mn

Preparation and Properties of Sodalite-Type Aluminophosphates Containing Silicon, Cobalt and Zinc

The SAPO, MeAPO and MeSAPO microporous materials (Me=Co2+ and/or 2n2+) having a sodalite structure have been obtained hydrothermally at 200°C in the presence of tetramethylammonium ion as the template. The SAPO and MeSAPO products prepared at lower template concentrations are formed through a partial replacement of both aluminium and phosphorus by silicon in the parent aluminophosphate lattice; at higher pH only phosphorus is replaced. While the Me2+ ions are in all cases constituents of the framework, most zinc-containing materials have a fraction of the Zn2+ ions located in the cavities. T.g.a . shows that complete removal of the trapped organic component can not be easily accomplished. This can be explained by the small size of the openings in the sodalite cages. Powder diffraction analysis shows that replacement of aluminium by silicon, cobalt and zinc, and phosphorus by silicon leads to an expansion of the parent aluminophosphate unit cell. Kinetic studies suggest that crystallization of the silicon-containing products is preceded by an induction period of about 2 h, the nucleation taking place both in the liquid and solid phase

3-(Metilamino)propilamin kao strukturni agens u sintezi neorganskih polimera na bazi fosfata

3-(Methylamino)propylamine (MPA) was studied as a structure-directing agent (template) in the synthesis of open-framework phosphate-based materials. The influence of temperature, mole ratio of reactants, crystallization time and presence of fluoride ions on the crystallization of aluminophosphate, transition metal-substituted aluminophosphate (transition metal - Mn(II), Cr(III) and Co(II)) and zincophosphate was also investigated. MPA exhibited a templating role and in all the as-synthesized crystalline products, it is entrapped in an inorganic lattice interacting with the framework via hydrogen or/and electrostatic interactions. According to detailed thermal analysis, the type of inter-actions seems to be crucial for the thermal behavior of MPA and for the thermal stability of the organic-inorganic crystal system. Structural analysis suggested that the formed crystalline structures had no mutual structural analogy. This indicates that the precise role of the organic (guest) component in nucleation process for the open-framework phosphates (host) is very complex as is the nucleation process itself. .3-(Metlamino)propilamin (MPA) izučavan je kao strukturni agens (templat) u sintezi poroznih materijala na bazi fosfata. Uticaj temperature, molskog odnosa reaktanata, vremena i prisustva fluorid-jona na kristalizaciju alumofosfata, alumofosfata koji u rešetki sadrže jone prelaznih elemenata (prelazni element - Mn(II), Cr(III) i Co(II)) takođe su izučavani. MPA ispoljava svojstva templata i u svim sintetisanim kristalnim proizvodima zarobljen je u neorganskoj rešetki sa kojom ostvaruje vodonične i/ili elektrostatičke interakcije. Prema detaljnoj termičkoj analizi vrsta interakcija je od presudnog značaja za termička svojstva MPA kao i termičku stabilnost čitavog organsko-neorganskog kristalnog sistema. Strukturna analiza je ukazala da među nastalim kristalnim strukturama nema sličnosti. Ovo ukazuje da je uloga organske ('gostujuće') komponente u procesu nukleacije poroznih fosfata složena kao i sam proces nukleacije.

On the possibility of the preparation open framework manganese phosphate

Manganese(ll)/phosphate/organic template hydrothermal reactions were investigated with the aim of preparing novel crystalline porous materials. Ethylenediamine, isopropylamine, and piperidine were explored as organics that would be able to organize oxide moieties of Mn(II) and P(V) into a porous MnPO, crystalline lattice. The synthesis in the presence of ethylenediamine yields a product with the double protonated organic entrapped in the void space of the crystal. However, the products obtained in the presence of isopropylamine and piperidine do not contain any organics. It seems that the only role of isopropylamine and piperidine in the crystallization of MnPO material is that of a base. Total removal of the occluded species occurs at around 3OO”C, after which the manganese phosphate products become X-ray amorphous