Aluminophosphate Research Articles

Control of Morphology and Acidity of SAPO-5 for the Methanol-To- Olefins (MTO) Reaction

Silicoaluminophosphate (SAPO) zeotype materials, a family of zeolites with micropores, have moderate acid strengths compared with conventional aluminosilicate zeolites; furthermore, their acid amounts can be tuned by the incorporation of Si species into the aluminophosphate (AlPO) framework. The conversion of methanol to light olefins including ethene, propene, and butenes (isobutene, 1-butene, and 2-butenes), methanol-to-olefins (MTO) reaction, is carried out over zeolites as an acid catalyst. In the MTO reaction, the enhancement of the diffusivity of reactants and products and the tuning of the acidity of zeolites are crucial keys to the improvement of the catalyst life due to the suppression of the coke deposition in the pores. In the present study, we have focused on the improvement of the catalytic performance of SAPO-5 materials with the AFI structure with large micropores of 0.73 nm apertures in the MTO reaction. Highly crystalline SAPO-5 with different morphologies and acidities were readily synthesized by merely varying the concentration of the starting gel. The employment of a highly concentrated starting gel with a H2O/Al ratio of 5 led to the formation of smaller-sized SAPO-5 crystallites with a larger amount of mild acid sites compared with SAPO-5 synthesized with the conventional compositions with the H2O/Al ratio of 50. The catalytic performance of the synthesized SAPO-5 materials as an acid catalyst was evaluated in the MTO reaction. The crystallite morphology as well as the acid amount scarcely affected the initial activity and product distribution, while the catalyst life was considerably affected. The decrease in the crystallite size of SAPO-5 led to improving the catalyst life due to the improvement of the resistance to the coke deposition.

An NMR crystallographic approach to monitoring cation substitution in the aluminophosphate STA-2

The substitution of the divalent cations Mg2+ and Zn2+ into the aluminophosphate (AlPO) framework of STA-2 has been studied using an “NMR crystallographic” approach, combining multinuclear solid-state NMR spectroscopy, X-ray diffraction and first-principles calculations. Although the AlPO framework itself is inherently neutral, the positive charge of the organocation template in an as-made material is usually balanced either by the coordination to the framework of anions from the synthesis solution, such as OH− or F−, and/or by the substitution of aliovalent cations. However, the exact position and distribution of the substituted cations can be difficult to determine, but can have a significant impact upon the catalytic properties a material exhibits once calcined.For as-made Mg substituted STA-2, the positive charge of the organocation template is balanced by the substitution of Mg2+ for Al3+ and, where required, by hydroxide anions coordinated to the framework [27] Al MAS NMR spectra show that Al is present in both tetrahedral and five-fold coordination, with the latter dependent on the amount of substituted cations, and confirms the bridging nature of the hydroxyl groups, while high-resolution MQMAS spectra are able to show that Mg appears to preferentially substitute on the Al1 site. This conclusion is also supported by first-principles calculations. The calculations also show that 31P chemical shifts depend not only on the topologically-distinct site in the SAT framework, but also on the number of next-nearest-neighbour Mg species, and the exact nature of the coordinated hydroxyls (whether the P atom forms part of a six-membered ring, P(OAl)2OH, where OH bridges between two Al atoms). The calculations demonstrate a strong correlation between the 31P isotropic chemical shift and the average 〈P–O–M〉 bond angle. In contrast, for Zn substituted STA-2, both X-ray diffraction and NMR spectroscopy show less preference for substitution onto Al1 or Al2, with both appearing to be present, although that into Al1 appears slightly more favoured.

Investigating Relationships between the Crystal Structure and 31P Isotropic Chemical Shifts in Calcined Aluminophosphates

Solid-state NMR spectra have historically been assigned using simple relationships between NMR parameters, e.g., the isotropic chemical shift, and aspects of the local structure of the material in question, e.g., bond angles or lengths. Density functional theory (DFT) calculations have effectively superseded these relationships in many cases, owing to the accuracy of the NMR parameters typically able to be calculated. However, the computational time required for DFT calculations may still be prohibitive, particularly for very large systems, where structure-spectrum relationships must still be used to interpret the NMR spectra. Here we show that, for calcined aluminophosphates (AlPOs), structure-spectrum relationships relying on either the mean P–O–Al angle or the mean P–O distance, both suggested in previous literature, provide a poor prediction of the 31P isotropic shielding, σiso, calculated by DFT. However, a relationship dependent on both parameters yields predicted σiso in excellent agreement with DF...

Prediction of the formation of microporous aluminophosphates containing (6, 8)-rings using support vector machines

A support vector machine (SVM) method has been used on the database of aluminophosphate (AlPO) synthesis with ca. 1700 reaction data to predict the formation of AlPOs with (6, 8)-rings based on 20 synthetic parameters associated with the gel composition, solvent and templates. Furthermore, four zeotype structures with different channel systems, such as AEN, AWO, ERI and CHA have been computational classified in the family of (6, 8)-ring-containing AlPOs. Analysis results reveal that several synthetic parameters, particular the molar ratio of solvent/Al2O3 (F3), and the Van der Waals (VDW) volume (F14), the greatest length (F11), and the number of free rotated single bond (F20) of templates have significant effects in directing the formation of target structure. Using single or combinations of several parameters, a better classifier can be trained to distinguish the (6, 8)-ring-containing AlPOs with desired zeotype structure or not, and the classification accuracy is about 85%. This work demonstrates that the computational method together with database of AlPO synthesis provides a possibility to establish the relationship between the synthetic factors and the resulting structures, which is important in guiding the rational synthesis of microporous aluminophosphate materials.

Synthesis of orderly nanoporous aluminophosphate and zirconium phosphate materials and their catalytic applications.

Amorphous alumino phosphate (AP) and zirconium phosphate (ZP) materials possessing an ordered nanoporosity have been successfully synthesized by a hydrothermal method using a P123 block co-polymer as the structure directing agent. The materials exhibited excellent catalytic activity towards selective alkylation of phenol with cyclohexanol, where AP showed as high as 100% selectivity to produce the industrially important O-alkylation product, while the corresponding ZP selectively produced a C-alkylation product (93% selectivity).

AlPOs Synthetic Factor Analysis Based on Maximum Weight and Minimum Redundancy Feature Selection

The relationship between synthetic factors and the resulting structures is critical for rational synthesis of zeolites and related microporous materials. In this paper, we develop a new feature selection method for synthetic factor analysis of (6,12)-ring-containing microporous aluminophosphates (AlPOs). The proposed method is based on a maximum weight and minimum redundancy criterion. With the proposed method, we can select the feature subset in which the features are most relevant to the synthetic structure while the redundancy among these selected features is minimal. Based on the database of AlPO synthesis, we use (6,12)-ring-containing AlPOs as the target class and incorporate 21 synthetic factors including gel composition, solvent and organic template to predict the formation of (6,12)-ring-containing microporous aluminophosphates (AlPOs). From these 21 features, 12 selected features are deemed as the optimized features to distinguish (6,12)-ring-containing AlPOs from other AlPOs without such rings. The prediction model achieves a classification accuracy rate of 91.12% using the optimal feature subset. Comprehensive experiments demonstrate the effectiveness of the proposed algorithm, and deep analysis is given for the synthetic factors selected by the proposed method.

General Information to Obtain Spherical Particles with Ordered Mesoporous Structures

Conditions for the synthesis of aluminum organophosphonate (AOP) and aluminophosphate (AlPO) spheres containing periodic mesopores were optimized and demonstrated to be general morphological controls for the surfactant-assisted synthesis of mesoporous materials. High-quality AOP and AlPO spheres with uniform mesopores were obtained at low and high temperatures, respectively. The aerosol-assisted synthesis of materials with uniform mesopores was categorized by using the difference in relative density of soluble AOP and AlPO oligomers that interact with ethylene oxide (EO) units in EO(n)PO(m)EO(n) triblock copolymer (PO=propylene oxide). Then, ordered mesoporous structures are constructed with the adequate amount of species in resultant frameworks, and the number of interactive points in soluble species determines the resultant density of the frameworks after self-assembly. Consequently, temperature-dependent synthesis, which allows controlled infiltration of soluble species to match the density of resultant frameworks, is required for the formation of ordered mesoporous structures under morphological control.

Studies on lithium alumino phosphate glasses doped with selenium ions for hard electrolytes

Glass samples of the system (100 − x) (0.5 Li2O–0.2Al2O3–0.3P2O5) + xSeO2 (x is ranging from 0 to 12 mol%, labeled as LAPS x ) were prepared using the melt quenching technique. FTIR spectral studies indicate that selenium ions mostly occupy network modifying sites due to isolated selenite (SeO3 2−) groups up to 6 mol% of SeO2 (LAPS6) in the LAPS glass network. This has a tremendous effect on the electrical properties. Glass forming ability parameter (K gl) and the glass transition temperature (T g) of LAPS samples were characterized by DTA traces. Electrical measurements were carried out as a function of frequency and temperature over the frequency range of 10 Hz to 106 Hz and a temperature range of 303–423 K. The electric modulus formalism was applied to study the relaxation behavior using the impedance data for all the samples at 303 K and also for analyzing the relaxation behavior of the highest conducting sample (6 mol% of SeO2) at different temperatures. An attempt has been made to relate the measured properties to the structural modifications due to the modifying effect of isolated selenite (SeO3 2−) groups in the glass network.

Characterization and adsorption properties of organosilyl aluminophosphate hybrids

Organosilyl aluminophosphates (AlPOs) were prepared by using organosilyl agents such as methyltriethoxysilane and ethyltriethoxysilane, and characterized by XRD, TG, ICP, CHN elemental analysis, NMR, SEM, and TEM, and gas adsorption properties of them were investigated. The organosilyl agents formed amorphous phases on the AlPO crystal surfaces. The amorphous phases play two roles; changing the size of pore and forming the new pore spaces. The change of pore size induces molecular sieving phenomenon for small molecules. The pore in the amorphous phase is more effective for i-butane than toluene molecules, although they have the similar molecular sizes each other.

A Comparison of Alumino and Calcium Phosphate Sintering Aids for Consolidation of Halide Containing Wastes

ABSTRACTA process has been developed at AWE for the immobilisation of halide containing wastes arising from the reprocessing of plutonium. Initially, the wastes are calcined with a calcium phosphate to form a number of target host phases, β-tricalcium phosphate (β-TCP) and apatite for the immobilisation of actinides, and apatite and spodiosite for halide.These mineral phases are then mixed with a glass binder, cold pressed and sintered to form a monolithic waste form. Two glass binders GTI/168, a sodium alumino phosphate glass and GTI/206, a sodium calcium phosphate glass were compared to optimise the halide retention in the waste-form. Analysis from powder X-ray Diffraction (PXRD) and scanning electron microscopy (SEM) showed that neither glass stabilises spodiosite. However, GTI/206 glass retains 10 wt.% more apatite and results in a much smaller proportion of the non-chloride bearing whitlockite phase than GTI/168.In all compositions where GTI/168 glass was used as a sintering aid, the sodium deficient and calcium enriched glass was present as an amorphous matrix phase.

SBE type cobalt-aluminophosphates (Co/Al ~ 1): synthesis aging effect, detemplation mechanism from coupled TGA/FTIR analyses, and structural stability after detemplation

Cobalt-rich SBE-type aluminophosphate (AlPO) microporous solids were prepared by employing different aging periods during the hydrothermal synthesis. According to XRD, SEM, and porosimetry tests, aging for 168 h results in a material with good long-range framework and textural features. The latter were analyzed after careful removal of the structure-directing agent (SDA) or detemplation, which produced a micropore surface area of ca. 600 m2/g, the highest ever reported for an AlPO having a multi-dimensional pore system and the highest cobalt-to-aluminum framework ratio. Coupled TGA/FTIR was employed in an attempt to elucidate the SDA decomposition mechanism in both inert and oxidative environments. Careful analysis confirmed that the latter case results in encapsulation of some of the detemplation species due to structural collapsing. Finally, the structural stability of detemplated material was evaluated in the presence of humidity and ambient air. The results indicate that the framework cobalt appear to readily oxidize upon adsorption of di-oxygen at ambient conditions, leading to an irreversible collapsing of the structure. However, the detemplated microporous solid appears to be stable in the presence of moist inert atmospheres.

Ionothermal synthesis of aluminophosphates used for ion exchange: Influence of choline chloride/urea ratio

A wide variety of industrial processes produce aqueous effluents that contain heavy metals. Considering the toxicity of metal polluted wastewaters, ion exchange appears as an easy and inexpensive option to remove metal ions from these effluents. There is currently much investigation on synthetic and natural materials to be used as cation exchangers. Among these materials, using microporous molecular sieves have been proposed due to their high surface area, porous diameter and ion exchange capacity. In this work, aluminophosphates (AlPOs) were prepared by the ionothermal method using the eutectic mixture urea/choline chloride (CCh) as solvent and template. Different CCh ratios in the eutectic mixture used in gel synthesis resulted in different structures with very distinguished ion exchange capacities. The main structures obtained were SIZ-2 and AlPO-CJ2. Varying the percentage of CCh in the gel synthesis mixture, it was observed that the AlPO-CJ2 structure is obtained using CCh percentages greater than 50%, while SIZ-2 is obtained using 25% and 33.3% CCh. The structure-directing the interrupted structure are the ammonium cations coming from the partial decomposition of urea. The SIZ-2 prepared using 25% CCh has a somewhat higher ion exchange capacity than that observed using 33.3% CCh. This result is very interesting since CCh is the most expensive component in the eutectic mixture.

Cycle stability of sorption materials and composites for the use in heat pumps and cooling machines

Thermally driven adsorption chillers and heat pumps are a very promising approach toward an efficient use of energy as well as an effective climate protection through reduced CO 2 emission of conventional heating and cooling devices. With regard to current market entrance of this technology, this paper presents results on the stability of current available materials like silica gels and zeolites, recently developed materials like aluminophosphates (AlPO) and silica-aluminophosphates (SAPO) and novel materials like metal organic frameworks (MOF) under hydrothermal treatment. Seven materials as powders or granules as well as three composite have been analyzed under continuous thermal cycling in a water vapour atmosphere in order to evaluate their suitability for the use in a periodically working heat pump with water as working fluid. The stability of powders has been analyzed in-situ by thermogravimetry in a first stage short-cycle test. In case of the composite, made up of an active sorption material and a support structure, a cycling-test rig has been developed in order to realize a life-cycle stress. The need for a first stage short-cycle test is demonstrated impressively by the dramatic loss of 40% in sorption capacity of a Cu-BTC sample within the first 15 cycles.

ChemInform Abstract: The Role of Synchrotron Radiation in Examining the Self‐Assembly of Crystalline Nanoporous Framework Materials: From Zeolites and Aluminophosphates to Metal Organic Hybrids

AbstractReview: 80 refs.

Gas-phase conversion of glycerol over mixed metal oxide catalysts

A series of aluminophosphates (APO) catalysts with Ce, Cu, Cr, Fe, Mn, Mo, V, and W oxide loading at a constant ratio M: Al = 1: 10 and PO4: Al = 1: 12 were prepared and characterized by N2 physisorption, XRD and NH3-TPD. Gas-phase dehydration of glycerol to produce acrolein and acetol was investigated at 280°C in presence of water. Conversion and product distribution depended on the intrinsic acidity and the type of transition metal oxide. Best selectivity to acrolein (52–58%) was obtained for W- und Mo-APO catalysts. Cr-, Mn- and W- oxide containing catalysts enhanced the formation of phenol, acetaldehyde and COx. The catalysts containing V- and Fe-oxide promoted the formation of allyl alcohol. All catalysts showed long term stability, which can be attributed to the redox ability of the metal oxides that enhances the removal of coke deposits. The investigated catalyst a specially W-APO and Mo-APO can be recommended for further controlled trials on a pilot plant for selective conversion of water solution of glycerol to acrolein and/or acetol.

Formation of microporous material AlPO 4-18 under dry-gel conversion conditions

The formation of microporous molecular sieve AlPO 4-18 under the dry gel conversion (DGC) conditions was examined. The evolution of the dry gel was monitored by powder XRD, SEM and, in particular, solid-state NMR techniques. The results show that the aluminophosphate (AlPO) amorphous dry gel is first converted to a layered AlPO phase. The layered intermediate has some resemblances to AlPO 4-18 and is held together by very weak non-bonding interactions. Continuous heating results in the transformation of this layered phase into AlPO 4-18 via reorganizations and condensations of P and Al sites. Three non-equivalent P sites of AlPO 4-18 develop at different rates during the evolution.

Photoinduced charge separation in microporous and mesoporous materials

A review of photoinduced charge separation of organic molecules in microporous and mesoporous materials is presented. In particular, the photoionization of N-alkylphenothiazine (PCn), N,N,N′,N′-tetramethylbenzidine (TMB), and porphyrin in microporous materials, such as zeolites, aluminophosphates (AlPOs), silicoaluminophosphates (SAPOs), and mesoporous materials, such as MCM-41, MCM-48, and SBA-15, is discussed.

Amorphous mesoporous aluminophosphate as highly efficient heterogeneous catalysts for transesterification of diethyl carbonate with dimethyl carbonate

The catalytic performance of an amorphous mesoporous aluminophosphate (AlPO) was investigated for the transesterification of diethyl carbonate (DEC) with dimethyl carbonate (DMC) to synthesize ethyl methyl carbonate (EMC). Compared with other solid acid and/or base catalysts, the mesoporous AlPO showed remarkably high activity, stability and recoverability for the reaction. We proposed that the presence of suitable weak acid–base pairs on the surface of the mesoporous AlPO material should play a critical role in the activation of reactants to produce EMC.

Effect of metal ion doping on the photocatalytic activity of aluminophosphates

The metal ions (Ti+4, Mg+2, Zn+2 and Co+2) have been substituted in place of Al+3 in aluminophosphates (AlPOs). These compounds were used for the first time as possible photocatalysts for the degradation of organic dyes. Among the doped AlPOs, ZnAlPO-5, CoAlPO-5, MgAlPO-11, 18 and 36 did not show any photocatalytic activity. MgAlPO-5 showed photocatalytic activity and different loading of Mg (4, 8, 12 atom % of Mg) were investigated. The activity can be enhanced by the increasing of concentration of the doped metal ions. TiAlPO-5 (4, 8, 12 atom % of Ti) showed the highest photocatalytic activity among all the compounds and its activity was compared to that of Degussa P25 (TiO2). The activity of photocatalysts was correlated with the diffuse reflectance and photoluminescence spectra.

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.