Structure Of Aluminophosphate Research Articles

Use of biobased crude glycerol, obtained biocatalytically, to obtain biofuel additives by catalytic acetalization of furfural using SAPO catalysts

High-pure crude glycerol, obtained from the transesterification of coconut oil with ethanol using lipase enzyme-type as biocatalyst, has been used for the acetalization of furfural with several SAPO 5 and SAPO 34 catalysts. SAPOs were prepared using microwaves and conventional heating for comparison, and were characterized by X-ray diffraction, nitrogen physisorption, elemental analysis, thermogravimetry of adsorbed cyclohexylamine and scanning electron microscopy techniques. The use of microwaves allowed us the incorporation of slightly higher amounts of silicon into the aluminophosphate structure, and the preparation of the materials in much shorter preparation times, with the subsequent energy saving. Additionally, the SAPOs prepared with microwaves showed lower crystallinity but higher surface area than those prepared by conventional heating. Comparable catalytic results were obtained when these catalysts were tested for the acetalization of furfural with commercial or with the crude glycerol obtained by biocatalytic transesterification of coconut oil, leading to very high selectivity values to the desired mixture dioxane + dioxolane (93–100 %), which can be used as biofuel additives, for conversion values between 60 and 73 %, as determined by gas chromatography. This confirmed the high purity of the glycerol obtained by the biocatalytical process, as previously observed by 1H NMR. SAPO 34 catalysts showed higher conversion than SAPO 5 catalysts due to their higher amount of more accessible Brønsted acid sites, related to their structure. Interestingly, catalysts prepared with microwaves resulted in slightly higher conversion values than those prepared by conventional heating. This can be explained by the incorporation of higher amounts of silicon in the framework, probably due to the higher homogeneity of the microwaves heating, which results in a higher amount of protons, as confirmed by TGA of adsorbed cyclohexylamine, responsible for the catalysis.

Insight in the Crystallization Kinetics of AlPO4-11 Molecular Sieve Using Di-Isopropylamine as Template

The hydrothermal synthesis of aluminophosphate molecular sieve type AlPO4-11 was processed from chemicals containing psueudobohemite, 85% phosphoric acid, water, and di-isopropylamine as templating agent. The crystallization of the samples was studied by taking samples in times from 2 to 74 h. The obtained white powder products were characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and differential scanning calorimetry (DTG) data and pH measurement of the mother liquor. The pore volume, as determined from TG and DTG curves, was ca. 0.17 cm3g−1. The percent relative crystallinity was determined by XRD and FT-IR methods. The crystallization kinetics evidenced that the hydrothermal synthesis of AlPO4-11 exhibited in its initial phase a behavior of first order reaction with a specific velocity constant of ca. 0.25 h−1, as determined from XRD and FT-IR data. The results obtained by both X-ray diffraction and infrared spectroscopy are comparable, and FT-IR is found to be a rapid method for estimating crystallinity and structure of aluminophosphate.

Characteristic studies on Ag2O-Al2O3-P2O5 glasses and glass ceramics

Glass structure comprising (0–20) mol% Al2O3–(20–40) mol % Ag2O-and 60 mol % P2O5 was examined using a 27Al, 31P MAS- NMR and FTIR spectroscopy. The structural changes within the complicated ternary phosphate glasses were correlated with that of a simple binary silver phosphate. Results show that aluminum acts primarily as intermediate ions, while silver acts as a potent modifier. The number of non-bridging oxygen atoms (NBO) on average in the structure of silver aluminophosphate (SAP) glasses decreases with increasing Al2O3 content. The aluminum ions in the SAP glass system occur in the coordinations of both Al (6) and Al (4). The Al (6) fraction rises with rising concentration of Al2O3. Al (6) is more than Al (4) in the glass containing more Al2O3 than that of 20 mol of Al2O3. The glass was transformed into a glass-ceramics by the effect of thermal heat treatment at 600 °C for 4 h.

Database of open-framework aluminophosphate structures

Open-framework aluminophosphates are an important class of inorganic crystalline compounds because of their rich structural chemistry and diverse properties. We have collected 312 open-framework aluminophosphate crystal structures from published literature and established a database for these structures. For each aluminophosphate structure, we have assigned a unique index code and extracted its key chemical and crystallographic information from the original literature and the associated CIF file, such as the name, chemical formula, extra-framework species, Al/P ratio, space group, and unit cell parameters of the compound. More importantly, we have calculated the topological features for each aluminophosphate framework, including local connectivity, framework dimension, coordination sequences, vertex symbols, topology density, and the largest ring. To help experimental chemists identify their products, we have also calculated theoretical XRD peaks for all aluminophosphate structures. This database will provide important insight into understanding the structural chemistry of open-framework aluminophosphate compounds.

Hierarchical AlPO4-5 and SAPO-5 microporous molecular sieves with mesoporous connectivity for water sorption applications

Herein, we report the synthesis of hierarchical AlPO4-5 and SAPO-5 molecular sieves that exhibit varying degrees of mesoporous interconnectivity by controlling the amount of triethylamine (TEA) (used as the structure directing agent) and the Si-to-Al ratio (Si/Al); the gel mixture had a composition of (1 − y) Al2O3:y SiO2:1.3 P2O5:x TEA:200 H2O. The molecular sieves were characterized by X-Ray powder Diffraction (XRD) and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDX), and their sorption properties were studied by N2 adsorption-desorption at 77 K and water adsorption at 316 K. In the synthesis gel with x = 1.6 ((1 − y) Al2O3:y SiO2:1.3 P2O5:1.6 TEA:200 H2O), SAPO-5 and AlPO4-5 exhibit high Brunauer-Emmett-Teller specific surface areas of ~380 m2 g−1 and 325 m2 g−1, respectively. SAPO-5, having a composition of Si0.46Al0.6P0.804, exhibits significant water uptake at low relative pressures (3.4 mmol/g at P/P0 = 0.03 vs. 0.2 mmol/g for pure AlPO4-5) attributed to the contribution of hydrophilic Brønsted acid sites, arising from the charge imbalance created by the isomorphic substitution of Si into the aluminophosphate structure predominantly via the SM2 mechanism. Furthermore, SAPO-5 exhibited a hierarchical pore structure having distinct pore size distributions centred on 0.7 nm and 15.8 nm, attributed to the AFI framework and the induced mesoporosity, respectively. At higher relative pressures, SAPO-5 exhibited the highest total water adsorption capacity of 14.1 mmol/g at a relative pressure of 0.38, compared to 11 mmol/g for AlPO4-5. The higher overall capacity of SAPO-5 is attributed to capillary condensation into the relatively large mesopore volume.

Effects of Extraframework Species on the Structure-Based Prediction of 31P Isotropic Chemical Shifts of Aluminophosphates

31P NMR spectroscopy is a valuable technique for the characterization of the local structure of aluminophosphates (AlPOs), capable of providing information on the number of crystallographic P sites, their relative populations, and the positions of any dopant atoms in the framework. Assigning the 31P spectra may, however, require multinuclear NMR experiments and/or density functional theory (DFT) calculations, which can be time-consuming, computationally costly, and challenging in cases involving disorder or dynamics. To address the issue of computational cost, we recently demonstrated a simple relationship between the local structure around P (primarily in terms of the mean P–O bond length and P–O–Al bond angle) and the 31P isotropic chemical shift, δiso, calculated by DFT for a series of calcined AlPOs. Here, we extend this approach to as-made AlPOs where we show that, at least to a first approximation, the presence of framework-bound anions and/or guest species within the pores of AlPOs can be translate...

FTIR and Raman spectroscopic study of sodium aluminophosphate and sodium aluminum-iron phosphate glasses containing uranium oxides

The effect of uranium oxides on the structure of sodium aluminophosphate and aluminum iron-phosphate glasses was investigated by FTIR and Raman spectroscopy. Introduction of low concentrations of UO2 and UO3 offers minor effect on the structure of both iron free and iron bearing glasses while incorporation of high content of UO3 markedly changes their structure reducing degree of connectedness of the glass network. Uranium in glasses produced with uranyl nitrate is present as U(VI) and U(V) which are responsible for the bands at ~200cm−1, ~470cm−1, ~540cm−1, 815–820cm−1, 887–895cm−1, and 944–946cm−1 due to vibrations of uranium-oxygen bonds in UO2+/2+ ions.

Phase composition and structure of sodium aluminophosphate based glass materials depending on their synthesis conditions

The effect of the method of synthesis on the structure of aluminophosphate glasses intended for immobilization of high level waste from uranium–graphite channel reactor spent nuclear fuel reprocessing has been studied by X-ray powder diffraction and Fourier transform IR spectroscopy. Slow cooling in a furnace, both spontaneous cooling in a switched-off furnace and cooling simulating the conditions of glass cooling in their disposal canisters, or additional heat treatment (annealing) led to partial crystallization of glasses with segregation of different modifications of aluminum orthophosphate. For orthoand pyrophosphate based glasses with similar anionic motifs, their phase composition and degree of crystallization depend not so much on the chemical composition of a sample as on its heat treatment history.

Sample-expand method for predicting the specified structure of microporous aluminophosphate

Imbalanced data sets often exist in many real-world fields and this problem has got more and more attention in recent years. In this paper, a sample-expand method is proposed as data pre-processing procedure to improve the predictive performance of the zeolite synthesis on imbalance data set. First, the data pre-processing is implemented for expanding samples by exploring the marginal structure of the given data set using k-nearest neighbor algorithm (KNN). Then, the expanded data set is input to support vector machines (SVM) for classification. Finally, Q times n-fold cross-validations procedure (CVs) is adopted to assess the prediction performance. The advantage of the data pre-processing is that it can obtain stable data set for establishing the training model and abide by the classification criteria of SVM, such that the improved predictive performance is achievable. Moreover, other classical machine learning methods are also presented to accomplish the prediction task. Compared experimental results demonstrate that SVM method can reach very satisfactory predictive accuracy on the pre-processing data set. Specially, the phase diagram of gel composition is provided as a guiding role for subsequent rational synthesis experiments.

Structure of Cerium Phosphate Glasses: Molecular Dynamics Simulation

We performed molecular dynamics (MD) simulations of the structure and properties of cerium-containing phosphosilicate, aluminophosphate, and aluminophosphosilicate glasses based on recent spectroscopic data that revealed 95% of cerium ions in such glasses are Ce3+. New Ce3+- and Ce4+-O2− potentials were developed and used in the MD simulations of these cerium-containing glasses with mixed glass formers. The local environments around cerium ions and network-forming cations, the medium range structure including glass-forming network Qn distribution, clustering, and second coordination shell around cerium ions have been carefully characterized. The results showed a longer Ce–O bond length and larger coordination number for Ce3+ than Ce4+ (2.48 and 6.4 vs. 2.24Å and 5.8, respectively). Around 5% of Si4+ ions were found to be in fivefold and sixfold coordination states in cerium phosphosilicate glasses, rather than the usual fourfold in silicate glasses. At the same time, the silicon–oxygen polyhedra were highly polymerized (over 80% of Q4) due to the presence of phosphorus oxide. Aluminum ions were found to be coordinated by four-, five-, and six oxygen ions, with an average coordination number of around 4.2. In both oxidation states, cerium ions were found to be preferentially surrounded by phosphorus–oxygen tetrahedra, which form a kind of solvation shell around them. The preference of network-forming cations around cerium ions in the second coordination shell was found to decrease in the sequence phosphorus, aluminum, silicon.

Preparation of aluminophosphate/polyethylene nanocomposite membranes and their gas permeation properties

Composite membranes were prepared by the incorporation of a porous layered aluminophosphate (ALPO) into polyethylene (PE) matrix, through both in situ polymerization with metallocene catalyst and melt compounding methods. ALPO was previously swollen with protonated octadecylammine (ODA) and cetyltrimethylammonium (CTA), which generated intercalated particles with different morphologies and dimensions. ODA–ALPO particles incorporated by in situ polymerization were found to be completely exfoliated in the composite, although probably with partial damage of their microporous structure. Composites prepared by melt compounding with CTA–ALPO particles, were found to contain particles predominantly in intercalated form, and apparently with good preservation of the aluminophosphate structure. Permeability results demonstrate that the incorporation of swollen-ALPO particles significantly improves the gas permeation properties of the semicrystalline polyolefin membrane. Gas permeability increase is attributed to novel transport pathways provided by the presence of the microporous ALPO layers as well as to the reduction of PE crystal size and the disruption of polymer-chain packing. Permeability of smaller gas molecules tended to be favoured, suggesting a molecular sieve effect through the microporous ALPO structure. ALPO/PE membranes exhibited particular H 2/CO permselectivity. Highest H 2/CO selectivity values were achieved at 5 wt.% loading of swollen-ALPO, particularly for membranes prepared by melt compounding using CTA–ALPO particles (H 2/CO = 9.5–17.0 as compared to H 2/CO = 1.0–2.6 for pure PE). The better performance of CTA–ALPO/PE membranes is attributed to a better preservation of the microporous structure of CTA–ALPO particles as well as to a better dispersion degree achieved through melt mixing technique. The results of this work open the possibility of the use of polyolefin composites prepared with the porous layered ALPO as a novel membrane material. Particular H 2/CO permselectivity exhibited by these membranes makes of it promising for hydrogen purification applications.

On the thermal degradation of 3-methylaminopropylamine captured inside the aluminum phosphate analog of ULM-3

An open-framework aluminophosphate analog of the fluorogallophosphate structure-type ULM-3 was obtained by hydrothermal crystallization of an aqueous aluminum phosphate suspension in the presence of 3-methylpropylamine (MAPA) and hydrofluoric acid. The open-framework fluorinated aluminophosphate structure was confirmed by Rietveld analysis and the 27Al, 31P, and 19F MAS NMR spectroscopy. The MAPA, located in the ten-membered ring channels, is doubly protonated to balance the negative charge of the Al3P3O12F22– framework. Thermogravimetric analysis data have been used to study kinetics of the thermal decomposition of MAPA. The decomposition was found to be a complex process, its activation energy varied from 177 to 259 kJ mol−1. The relatively high E values are explained by the fact that the MAPA cations are bound to the anionic framework both by electrostatic forces as well as strong N-H…O hydrogen bonds. The strength of the interactions is indirectly confirmed by the in situ high temperature X-ray diffraction analysis which shows that the MAPA decomposition leads to a phase transformation of the open-framework structure to the dense trydimite phase.

The structure of aluminophosphate glasses revisited: Application of modern solid state NMR strategies to determine structural motifs on intermediate length scales

In this paper we report a reinvestigation of the network organization in aluminophosphate glasses. Samples were prepared along the 50K2O–xAl2O3–(50−x)P2O5 composition line with 0<x<20%. The evolution of the glass structure upon alumina incorporation into the phosphate network is monitored employing a combination of advanced solid state NMR strategies including 31P{27Al}-CP-HETCOR NMR, 31P{27Al}-REAPDOR NMR, 27Al{31P}-REDOR NMR and 2D 31P-J-RESolved NMR spectroscopy. Details of the employed NMR protocol are given elsewhere. The network organization on intermediate length scales as a function of the alumina content is then described employing a modified Q notation, Qm,AlOxn, where n denotes the number of connected tetrahedral phosphate, m gives the number of aluminate species connected to a central phosphate unit and x specifies the nature of the bonded aluminate species (i.e., AlO4-, AlO5- or AlO6-species).

Organically Modified Aluminophosphates: Transformation of Boehmite into Nanoparticles and Fibers Containing Aluminodiethylphosphate Tectons

The reaction of boehmite with diethyl phosphoric acid generated in situ in a boiling water solution of triethyl phosphate has been studied in detail. Two kinds of solid products have been isolated and characterized by elemental and XPS analysis, in addition to XRD, TGA, FT-IR, SEM, and MAS NMR techniques. One of them precipitates from the reaction mixture in the form of fibers containing needlelike hexagonal crystals with the unit-cell parameters a = 21.105(4) A and c = 9.112(2) A (V = 3515(1) A3). The crystalline structure comprises hexagonally packed catena Al[OP(O)(OC2H5)2]3 chains. The other ones form a colloidal dispersion of spherical nanoparticles that consist of a boehmite core covered by aluminodiethylphosphate chains. The NMR studies of the reaction mixture indicate that water soluble aluminophosphate species are also formed in the systems studied. These species are suggested to act as nutrients for the growth of aluminophosphate structures. Colloidal particles and fibers have been included into...

Unique Organic−Inorganic Interactions Leading to a Structure-Directed Microporous Aluminophosphate Crystallization as Observed with in situ Raman Spectroscopy

We report on the direct observation of key organic template-framework interactions leading to the formation of specific aluminophosphate structures. In particular, we show how MeAPO-34 formation was governed by an interaction between the divalent framework substituted metal ion and the template conformation, while for AlPO-5 the structure formation was determined by the template conformation alone. Understanding such interactions therefore appears to be important for the rationalization of microporous material formation.

Thermally Stable Amorphous Mesoporous Aluminophosphates with Controllable P/Al Ratio: Synthesis, Characterization, and Catalytic Performance for Selective O-Methylation of Catechol

Amorphous mesoporous aluminophosphates (AlPO) with P/Al molar ratio in the range 0.8-1.15 are synthesized by using the citric acid (CA) route and are systematically characterized using N(2)-adsorption, XRD, SEM, solid-state CP-MAS NMR, FT-IR, TG-DTA, CO(2)-TPD, and NH(3)-TPD. The characterization studies show that the change in P/Al ratio could affect the structure, texture, thermal stability, and surface acid-base properties of AlPO. Samples with a relatively low P/Al ratio (< or =1.0) exhibit uniform amorphous mesoporous character and high thermal stability (up to 1173 K). Partial crystallization of the AlPO framework easily occurred on the sample with higher P/Al ratio (> or =1.1), thus leading to significant decrease of surface area and formation of particle pile mesopores. Both weak acid and weak base sites are observed over AlPO materials, and the amounts of acid-base sites can be effectively controlled by adjusting the P/Al ratio. The presence of suitable interaction between citric acid and AlPO framework is critical for the formation of mesoporous structures. Both CA and PO(4) units are considered to be ligands to coordinate with aluminum ions, forming relative uniform complexes (such as CA-Al-PO(4)) in the as-synthesized AlPO materials. The mesoporous structure of AlPO materials is obtained after the rapid decomposition of citric acid. Vapor phase selective O-methylation of catechol with methanol reaction is carried out to investigate the catalytic performances of AlPO materials with different P/Al ratios. Among them, AlP(1.1)O shows the highest activity (88.4% conversion of catechol) and the highest yield of guaiacol (74.3%). The presence of suitable weak acid-base pairs may play an important role on the title reaction.

Synthesis and Characterization of a New Microporous Material. Part 1. Structure of Aluminophosphate EMM‐3.

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Prediction of Open‐Framework Aluminophosphate Structures Using the Automated Assembly of Secondary Building Units Method with Lowenstein′s Constraints.

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Solid-State NMR Spectroscopy of Anionic Framework Aluminophosphates: A New Method to Determine the Al/P Ratio

A series of anionic framework aluminophosphates, with different Al/P ratios, have been investigated by various solid-state NMR techniques, including 27Al, 31P magic angle spinning (MAS), 27Al-->31P cross polarization (CP), 27Al{31P} rotational echo double resonance (REDOR), and 31P{27Al} transfer of population double resonance (TRAPDOR). Different Al coordinations (AlO4b, AlO5b, and AlO6b) and P coordinations (PO4b, PO3bOt, PO2bO2t, and PObO3t), where b represents bridging oxygens and t represents terminal oxygens, can be unambiguously determined based on the solid-state NMR spectroscopy. Furthermore, a new method to determine the Al/P ratio of open-framework aluminophosphates has been established, which is useful for the understanding of unknown aluminophosphate structures.

Structure of Metal Aluminophosphates: Al 9– x M x P 12 O 48 (TREN) 4 · yNH 4 · zH 2O [TREN = N (CH 2 CH 2 NH 3) H m, M = Mn, Co

Two large-pore metal-doped aluminophosphates, Mn4 Al5 (PO4)12 [N (C2 H4 NH3)3]3 [N(C2 H4 NH3)2 · (C2H4NH2)] (NH4)2 · 14H2O(Mn4-NJU) and Co4Al5 (PO4)12 [N(C2H4NH3)3] [N(C2H4NH3)2 (C2H4NH2)]3 · (NH4)4 · 13H2O(Co4-NJU), which have the same open framework structures, were hydrothermally synthesized. The structures of these compounds consist of TO4 tetrahedra, which are linked together by corner-sharing to form an open framework with unique intersecting twelve-membered ring channels in three dimensions. The compounds crystallize in cubic space group I (-4)3m with a = 1.6795(2) nm and V = 4.7374(9) nm3 for Mn4-NJU, and a = 1.67372(19) nm and V = 4.6887(9) nm3 for Co4-NJU, respectively. Single crystal structure analyses show that the protruding O atoms of the frameworks of the compounds are linked to protonated 4-(2-aminoethyl) diethylenetriamine (TREN, C6H18N4) ions in the windows by means of hydrogen-bonding under the hydrothermal condition. It is also found that the components inside the super cages of the compounds are changeable, and the metal ions M2+ (M = Mn, Co) and Al3+ disorderedly occupy the same crystallographic positions.