Molecular Sieves: Aluminophosphates

Abstract

Aluminophosphate molecular sieves exhibit structural and compositional diversity. Their frameworks can be modified by other elements, thus providing novel SAPO, MAPO, and MAPSO materials. They possess the characteristics of both zeolites and aluminophosphates all of which result in unique catalytic, ion‐exchange, and adsorbent properties. Aluminophosphate molecular sieves have been prepared hydrothermally in nonaqueous reaction media. The crystallization process depends on a number of variables including temperature, time, molar ratio of the reactants, and pH. The most commonly investigated metal ions incorporated into aluminophosphate frameworks are transition metal ions of first transition series. Different characterization techniques are used for studying their oxidation number, location, and coordination environment within aluminophosphate frameworks. These parameters, together with structural characteristics of the framework such as pore size, pore shape, and geometry, significantly affect the catalytic performance of aluminophosphate materials. Methanol to olefin conversion and oxidation reactions are instances of industrially important reaction systems where aluminophosphate molecular sieves demonstrate an important catalytic performance.

The Influence of Thermal Treatment on the Formation Mechanism of the Cu, Fe-Containing Nanocomposite Material Synthesized by the Sol–Gel Method

“…The native sample to be subjected to thermal treatment at various temperatures was synthesized by the sol-gel method, starting from the iron and copper cation salts [43,[66][67][68]. The self-catalyzed sol-gel synthesis implied the next procedure: two catalyst solutions, containing Fe 3+ and Cu 2+ , were prepared in separated beakers by the dissolution of salts in 10 mL of water cations (Fe(NO 3 ) 3 • 9H 2 O and Cu(NO 3 ) 2 • 3H 2 O were mixed at the molar ratio 0.01 : 0.01).…”

Open‐Framework Aluminophosphates: Synthesis, Characterization and Transition Metal Modifications

“…Isomorphous substitution, i.e., the replacement of Al 3+ and/or P 5+ by a tetrahedrally coordinated metal ion has been reported for more than 17 elements. 45,46 Different characterization techniques are used in order to gain an insight into the location of the transition metal ions in an aluminophosphate framework. Generally, data on the location of the cations are collected with difficulty since the metal concentration is usually low.…”

Morphology, Activation, and Metal Substitution Effects of AlPO4-5 for CO2 Pressure Swing Adsorption

“…The crystal lattice of AlPO 4 -5 possesses a hexagonal symmetry and a monodirectional channel morphology extending along the c -axis. The main channels are created by 12-member rings of alternating tetrahedra of [AlO 4 ] − and [PO 4 ] + having a diameter of 7.2 Å (Rajic and Kaucic, 2002 ; Guo et al, 2005 ; Karanikolos et al, 2008 ). Here, we assess the impact of various factors on CO 2 sorption, namely, (a) the effect of various heteroatoms used in isomorphic substitution in the AlPO 4 -5 framework at varying concentrations, (b) the pore activation method and in particular the affinity of remnant carbon species present into the inner pore surface after structure-directing agent (SDA) removal by two different thermal treatment methods, i.e., partial oxidation and pyrolysis, and (c) the impact of AlPO 4 -5 crystal morphology and hydrothermal synthesis mixture composition and in particular the water content in the mixture.…”