Aluminophosphate Molecular Sieves Research Articles

Synthesis and characterization of cobalt substituted aluminophosphate molecular sieve: Co-SSZ-51 under microwave-hydrothermal conditions

Isomorphic substitution of cobalt ions in the crystalline microporous framework of aluminophosphate molecular sieve SSZ-51 has been investigated using a gel composition of 2.5SDA:(1− x)Al 2O 3:1.0P 2O 5: xCo 2O 3:0.5HF:50H 2O ( x = 0, 0.01, 0.05, 0.08, 0.1, 0.15, 0.2) under microwave-hydrothermal conditions at 453 K. The crystallization was performed by employing cobalt nitrate, pseudoboehmite, ortho-phosphoric acid as cobalt, alumina and phosphorous precursors respectively and 4-dimethyl aminopyridine (4-DMAP) as structure directing agent (SDA) at 453 K. The effect of crystallization temperature was investigated at 423, 438, and 453 K under microwave and conventional hydrothermal conditions. Likewise, the effect of crystallization time was studied at 453 K. The crystallized samples were characterized by means of powder X-ray diffraction (PXRD), UV–visible diffuse reflectance spectroscopy (UV–DRS), and nitrogen adsorption–desorption measurements at 77 K. The obtained results demonstrated that the successful crystallization of Co-SSZ-51 framework, up to a gel having Co/Al ratio of 0.1, could be achieved at 453 K with in 20 h under microwave-hydrothermal conditions. The further increase in cobalt concentration led to the crystallization of non-microporous framework.

Synthesis, characterization and catalytic properties of vanadium aluminophosphate molecular sieves VAPO-31 and VAPSO-Amr from non-aqueous media

Vanadium samples containing aluminophosphate molecular sieve (VAPO-31) and amorphous vanadium silicoaluminophosphate (VAPSO-Amr) have been synthesized using hexamethyleneimine template from non-aqueous media for the first time. XRD and SEM analyses confirm the phase purity of the synthesized samples. FT-IR analysis suggests the incorporation of V 4+ in the aluminophosphate framework. ESR, UV–vis spectroscopic, and XPS techniques and cyclicvoltametric studies confirm the incorporation of vanadium and reveal its presence in tetrahedral and square pyramidal environments in the as-synthesized samples. Cyclic voltammetry reveals the presence of two redox couples in VAPO-31. This catalyst is found to be a good oxidation catalyst. Although most of the properties of VAPO-31NA and VAPSO-Amr are similar, the latter can access more vanadium and V 4+ ions. Compared to aqueous media samples, it can incorporate more vanadium especially V 5+ ions and has been found to be better oxidation catalyst. The physicochemical properties also change with media.

Synthesis novel aluminophosphate molecular sieves at atmospheric pressure

Novel small pore aluminophosphates molecular sieves AlPO4-Atm1, AlPO4-Atm2 and AlPO 4 -Atm3 have been synthesized using hexamethyleneimine template at atmospheric pressure (373K) for the first time. Gel composition Al2O3: P2O5: 1.16HEM: 45H2O was taken as the standard one which gives AlPO 4 -Atm12. Change in water molar ratio to 67.5 gives AlPO 4 -Atm2. On changing the aluminium source from catapal B to aluminium isopropoxide in same molar gel composition gives AlPO4-Atm3. All the materials were characterized by XRD, SEM, TG/DTA, C & N analysis, FT-IR and MASNMR analysis. Elemental analysis shows that Al and P are in equal molar composition. XRD analysis shows that the synthesized samples are highly crystalline and new. SEM shows the morphology change with structure. TG/DTA analysis reveals the presence of maximum four stage elimination of templates. Carbon and nitrogen analysis gives the amount of template present in the sample. 27 Al MASNMR shows the presence of single type tetrahedrally co-ordinated aluminium atoms in AlPO 4 -Atm1. 31P MASNMR of the same sample shows the presence of two type of tetrahedrally co-ordinated phosphorous atoms.

Microporous alumino-phosphate (AlPO 4-5) molecular sieve-loaded novel sodium alginate composite membranes for pervaporation dehydration of aqueous–organic mixtures near their azeotropic compositions

Microporous materials are known to exhibit pronounced molecular sieving effect and selective adsorption capacity, the incorporation of which into a selected natural polymer, can be used to tailor the material intrinsic properties such as mechanical strength and separation performance. In this research, microporous alumino-phosphate (AlPO 4-5) has been employed to prepare novel sodium alginate (NaAlg)-based composite membranes by solution casting technique and crosslinking with glutaraldehyde. These membranes have been tested for the pervaporation (PV) dehydration of isopropanol (12.6 wt.% water), 1,4-dioxane (18.1 wt.% water), THF (6.7 wt.% water) and ethanol (4 wt.% water) from their aqueous mixtures at 30, 40, 50, 60 and 70 °C. However, PV dehydration studies at feed composition from 5 to 20 wt.% were done for pristine NaAlg and 20 wt.% AlPO 4-5-loaded composite membranes at 30 °C. The activation parameter values involved in the permeation process were evaluated. Pervaporation results have shown the simultaneous enhancement of flux and selectivity near the azeotropic compositions of the feed mixtures as a result of adding varying amounts (5, 10, 15 and 20 wt.%) of AlPO 4-5 into NaAlg-based matrix. Flux and selectivity increased simultaneously for all the feed mixtures with increased loadings of AlPO 4-5 at 30 °C. Selectivity to water was higher for water–isopropanol azeotrope, but flux was more in case of water–1,4-dioxane and water–THF azeotropes. Selectivity to water was smaller for water–THF and water–ethanol azeotropes as compared to water–isopropanol and water–1,4-dioxane azeotropes. Pervaporation results have been discussed in terms of sorption–diffusion principles. Molecular sieving effect due to uniform distribution of microporous molecular sieve particles, and hydrophilic characteristics of the alumino-phosphate molecular sieve in addition to its interaction with the hydrophilic NaAlg matrix are responsible for such an appreciable increase in membrane performance over that of pristine cross-linked NaAlg membrane. Composite membranes of this study have shown better mechanical strength properties than the pristine cross-linked NaAlg. The present membranes could withstand the repetitive cyclic PV processes when tested on a laboratory scale module.

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Schnell und sicher: Die Kombination von Mikrowellen mit ionischen Flüssigkeiten bietet eine neue Möglichkeit, Alumophosphat-Molekularsiebe herzustellen (siehe Bild). Diese Methode ermöglicht eine Synthese bei Normaldruck und zeichnet sich durch eine rasche Kristallisation und eine hohe Strukturselektivität aus. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2006/z600054_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Microwave‐Enhanced Ionothermal Synthesis of Aluminophosphate Molecular Sieves

Structure-Directing Role of Amines in the Ionothermal Synthesis

The structure-directing effect of amine has been observed in the ionothermal synthesis of aluminophosphate molecular sieves in 1-butyl-3-methylimidazolium bromide ionic liquid. The seven different amines we tested have an influence on the crystallization dynamics and the final product, leading to the formation of pure AFI and ATV structures.

Aluminophosphate-based, microporous materials for blood clotting

Water absorption and mouse blood clotting experiments show that aluminophosphate molecular sieve VPI-5 containing Ca 2+ ions can clot blood like the zeolite-containing QuikClot, but with 50% less heat release. These data suggest that Ca 2+ containing microporous aluminophosphates may be useful as inexpensive human blood clotting agents.

Thermally stable trivalent iron-substituted hexagonal mesoporous aluminophosphate (FeHMA) molecular sieves: Synthesis, characterization, and catalytic properties

Thermally stable trivalent iron-substituted hexagonal mesoporous aluminophosphate (FeHMA) molecular sieves were synthesized and systematically characterized using analytical and spectroscopic techniques, including XRD, TEM, ICP–AES, TGA–DTA, N 2 sorption, DRUV–vis, EPR, and Mössbauer spectroscopy. The characterization studies showed that framework substitution of trivalent iron in tetrahedral framework position of the mesoporous aluminophosphate has taken place. Mössbauer revealed the presence of a small amount of divalent iron. This material has high thermal stability with regard to the dislodgement of trivalent iron from the framework structure on calcination and showed excellent activity in the liquid-phase oxidation of cycloalkanes such as cyclohexane, cyclooctane, and cyclododecane in presence of molecular oxygen or air under mild reaction conditions. FeHMA behave as a heterogeneous catalyst; the catalytic activity was practically unaffected by recycling experiments. Furthermore, the oxidation was successful for the bulkier cycloalkane molecules. A comparative study with selected iron-containing molecular sieve-based catalysts indicated that FeHMA is a promising heterogeneous catalyst with respect to its microporous analogue (FeAPO-5) as well as the silicate analogues, microporous FeS-1 and mesoporous FeMCM-41.

High field ENDOR as a characterization tool for functional sites in microporous materials

The determination of the details of the spatial and electronic structure of functional sites (centers) in any system, be it in materials chemistry or in biology, is the first step towards understanding their function. When such sites happen to be paramagnetic in any point of their activity cycle, the tool box offered by a variety of high resolution electron paramagnetic resonance (EPR) spectroscopic techniques becomes very attractive for their characterization. This tool box has been considerably expanded by the developments in high field (HF) EPR in general, and HF electron nuclear double resonance (ENDOR), in particular. These have led to numerous new applications in the fields of biology, physics, chemistry and materials sciences. This overview focuses specifically on recent applications of pulsed HF ENDOR spectroscopy to microporous materials, such as zeotype materials, presenting the new opportunities it offers. First, a brief description of the theoretical basis required for the analysis of the HF ENDOR spectrum is given, followed by a description of the pulsed techniques used to record spectra and assign the signals, along with a brief presentation of the required instrumentation. Next, specific applications are given, including transition metal ions and complexes exchanged into zeolite cages, transition metal substitution into frameworks of zeolites, aluminophosphate molecular sieves, and silicious mesoporous materials, the interaction of NO with Lewis sites in zeolite cages and trapped S. We end with a discussion of the advantages and the shortcomings of the method and conclude with a future outlook.

Synthesis and characterization of AIPO4-5RT molecular sieve at room temperature

Aluminophosphate molecular sieve AlPO 4 -5RT (AlPO 4 -5, prepared at room temperature) have been synthesized using hexamethyleneimine template at room temperature for the first time. Gel composition Al 2 O 3 : P 2 O 5 : 1.16HEM; 45H20 aging for 12 h at room temperature, and in 24 h, 473 K are the standard reaction conditions for synthesis of AlPO 4 .5. Studies on above gel composition at room temperature shows the presence of AlPO 4 -5 crystals. Both the aluminophosphates have been characterized by elemental analysis, XRD, SEM, FT-IR, TG/DTA, and 13 C, 27 Al and 31 P MASNMR techniques. XRD analysis of AlPO 4 -5RT shows that the presence of low intensed pseudobuehmite sample. SEM shows the morphology nanosized crystals along with platelets. TG/DTA analysis reveals the presence of maximum five stages elimination of templates. Carbon and nitrogen analysis shows that the presence of four template molecules per uniteell. 13 C MASNMR analysis shows the Interaction of template with structure of the framework. 27 Al MASNMR shows the presence of small amount of octahedral co-ordination besides the rest are in tetrahedral co-ordination. 31 P MASNMR shows the presence of two environmentally different tetrahedrally co-ordinated phosphorous atoms.

Location of Vanadium(IV) in VAPO-5 as Studied by Hyperfine Sublevel Correlation Spectroscopy

Abstract Vanadium(IV) framework substitution in aluminophosphate molecular sieves has been explored by electron spin resonance (ESR) and hyperfine sublevel correlation (HYSCORE) spectroscopy. In both as-synthesized and hydrated materials V(IV) exists as VO2+ species that coordinates to two framework oxygen atoms and presumably three water molecules in a distorted octahedral geometry.

Structural analysis and adsorption sites of xylenes in AlPO 4-5 and AlPO 4-11 using molecular simulation

Sorption of xylenes in two aluminophosphate molecular sieve structures, AlPO 4-5 and AlPO 4-11, has been studied using Monte Carlo simulations. Pure-component adsorption isotherms were predicted and compared with previously reported experimental data. Our simulated isotherms for xylenes in AlPO 4-5 showed a qualitative agreement with the experimental data available especially the ortho-selectivity. However, for AlPO 4-11, despite the qualitative agreement between the simulated and experimental isotherms, ortho-selectivity could not be precisely reproduced. A detailed structural analysis is also presented for each component in both molecular sieves. The analysis was performed using the detailed structures for the crystals and molecules, the statistics of the molecules centers of mass during the simulation, and the orientation of the normal vector to the plane of the molecules aromatic ring. Based on this analysis, the adsorption sites and molecules positioning in the crystals channels were proposed. The molecules positioning confirmed the configurations proposed from experimental data by other authors. The simulations also showed that the ortho-selectivity previously observed in experimental results could be related to the variations in the channels diameters and the corresponding interaction energy of the molecule–crystal lattice.

Structure-Directing Role of Molecules Containing Benzyl Rings in the Synthesis of a Large-Pore Aluminophosphate Molecular Sieve: An Experimental and Computational Study

We describe the synthesis of AlPO-5 and SAPO-5 materials (AFI topology) using five different tertiary amines or quaternary ammonium ions containing one or two benzyl rings as structure-directing agents (SDAs). All of the molecules successfully direct the crystallization of AlPO-5; however, only the most efficient templates are able to crystallize SAPO-5. The observed differences in template efficiency can be rationalized in terms of the interaction energy between these molecules and the AFI framework. In ranking the template molecules, we notice that a well-defined molecular shape enhances the templating ability, but molecules that are too rigid are not able to adapt to the AlPO framework, yielding an inferior templating ability. Results of atomic-level modeling show that templates with one benzyl ring self-assemble in the main AFI channel by forming dimers with the benzyl rings parallel to each other; templates with two benzyl rings assemble instead into longer chains in which the benzyl ring of one molecule faces the ring of the subsequent one. Both mono- and dibenzyl templates show a high space-filling ability in AFI. Kinetic and thermodynamic factors that might affect the structure-directing activity of the molecules are examined.

Synthesis and Characterization of a Novel Extra Large Pore Aluminophosphate Molecular Sieve, NCL‐6.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hydrothermal crystallization and characterization of R+3: AlPO4zeolites, where R = Ce, Pr and Nd

Zeolites are the most important technological materials made up of framework of aluminosilicates, aluminophosphates, vanadophosphates, silicoaluminophosphates and so on. In the recent years the interest is being extended greatly from the molecular sieves to selective catalysis, gas adsorption, nanoparticle hosts, atmospheric ecosystems, etc. These aluminophosphate molecular sieve zeolites have uni-, two-, and three-dimensional channels which are obtained hydrothermally in the presence of organic amines as structure directing agents. VPI-5 is an important aluminophosphate molecular sieve with 18 tetrahedral rings and free diameter of 12.1 A. In this paper, the authors discuss the synthesis of R+3: aluminophosphate, where R=Ce, Pr and Nd.

In situ synthesis of aluminophosphate microporous molecular sieve 8-hydroxyquinoline–AlPO 4-5 with blue-emitting luminescence property

Utilizing 8-hydroxyquinoline as a novel organic template, microporous aluminophosphate molecular sieve 8-hydroxyquinoline–AlPO 4-5((C 9H 7NO) 3 [Al 12P 12O 48]) single crystals have been synthesized. The AFI type structure of the crystals has been identified by powder X-ray diffraction. TGA and C–H–N analysis results show there are three 8-hydroxyquinoline molecules per unit cell. The 27Al NMR indicates that quarter aluminum atoms located in the framework are distorted five-coordinated, with one-coordinated oxygen atom coming from 8-hydroxyquinoline. Two optimized configurations with the lowest energy were calculated from 12 possibilities of three aluminum atom in the framework per unit cell coordinated with three 8-hydroxyquinoline molecules. Due to the available restricted space of the micropore of AlPO 4-5, the 1:1 stoichiometry Al–Q complex has been successfully achieved, which led to the strong luminescence property at room temperature and blue shift of 20 nm compared with the PL of traditional AlQ 3.

Temperature-Induced Transformations in CoAPO-34 Molecular Sieve: A Combined In Situ X-ray Diffraction and FTIR Study

Thermally induced processes of CoAPO-34, an aluminophosphate molecular sieve with chabasite-type structure, synthesized in the presence of morpholine as a structure-directing agent and HF as a mineralizing agent, have been studied by in situ X-ray synchrotron powder diffraction augmented with Fourier transform (FT) IR analysis. A time-resolved experiment was performed using a translating imaging plate system. At room temperature, the structure refinement by full-profile Rietveld analysis showed P-1 symmetry and the presence of one Al site with sixfold coordination. At around 400 degrees C, both fluorine and morpholine are lost, and the four-connected chabazite (CHA)-type topology is restored. Notwithstanding the metrically rhombohedral values of the cell parameters, the symmetry remains triclinic P-1. Inhomogeneous dealumination of the framework begins at 725 degrees C, accompanied by a strong triclinization of the unit cell and followed by the collapse of the structure above 775 degrees C. The insertion of cobalt ions within the CHA framework was monitored by FTIR spectroscopy, which showed that bridged Co(2+)-O(H)-P hydroxyls are present after morpholine removal.

Thermal analyses of various alkylamines-templated aluminophosphate AlPO 4-21

Thermal removals of amine-templated aluminophosphate molecular sieve AlPO 4-21 have been studied by X-ray powder diffraction (XRD), TG–DTA and temperature-programmed decomposition coupled with mass spectrometer (TPD–MS) analyses (amine: ethylamine, dimethylamine and trimethylamine). It is found that the thermal removal of templates and bridging OH groups between two Al atoms is an endothermic process occurring in a single step in inert atmosphere, which accompanies the structural transformation of AlPO 4-21 to AlPO 4-25. The removal temperatures of various organic amines occluded within AlPO 4-21 are directly related to the shapes and sizes of the templates, as well as the proton affinities of guest cations. These factors also determine the removal mechanisms of templates from AlPO 4-21.

Synthesis and characterization of divalent cobalt-substituted mesoporous aluminophosphate molecular sieves and their application as novel heterogeneous catalysts for the oxidation of cycloalkanes

Thermally stable divalent cobalt-substituted hexagonal mesoporous aluminophosphate, CoHMA molecular sieves were hydrothermally synthesized and systematically characterized by several analytical and spectroscopic techniques. XRD, TEM, ED, ICP-AES, TGA-DTA, N 2 sorption, DR-UV–vis, XANES, and NH 3-TPD studies showed isomorphous substitution of divalent cobalt in a tetrahedral framework of a mesoporous aluminophosphate matrix. Furthermore, the blue color of CoHMA, before and after thermal treatment, further confirmed the tetrahedral environment of divalent cobalt in the matrix. As a result, the CoHMA catalyst showed excellent activity for the oxidation of cycloalkanes, that is, cyclohexane, cyclooctane and cyclododecane, under mild reaction conditions. Unlike the many other cobalt-based heterogeneous catalysts reported so far, CoHMA does not show any dislodgement or segregation of cobalt with calcination or any other postsynthesis treatments. In this study, the performance of CoHMA was also compared with the cobalt-containing microporous aluminophosphate, that is, CoAPO-5 with AFI topology, as well as with both microporous and mesoporous analogues of cobalt silicate molecular sieves that have MFI or MCM-41 structures.