Synthesis And Water Sorption Properties Of Aluminophosphate (AlPO4) And Silicoaluminophosphate (Sapo) Molecular Sieves (original) (raw)
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Surface & Coatings Technology, 2018
In this manuscript, we present the synthesis of hierarchical AlPO 4-5 and SAPO-5 structures. We describe in detail the effect of the structural directing agent (SDA) triethylamine (TEA) on the crystal structure of AlPO 4-5 emergence of mesopores. We also investigate the impact of this mesoporosity on AlPO 4-5 adsorptive properties. Furthermore, we present a synthesis methodology for a hierarchical silico-aluminum phosphate SAPO-5 possessing interlinked microporosity and mesoporosity. The hierarchical SAPO-5 possesses substantially improved water adsorption properties rendering it useful in dehumidification applications. The study of water adsorptive properties of hierarchical AlPO 4-5 and SAPO-5 is novel.
Computational Study for Water Sorption in AlPO 4 -5 and AlPO 4 -11 Molecular Sieves
Langmuir, 2010
The unusual water adsorption behavior in aluminophosphate molecular sieves AlPO 4 -5 and AlPO 4 -11 was studied using canonical Monte Carlo and periodic density functional theory (DFT) calculation. The number of adsorbed water molecules per cavity ranging from 1 to 12 were located inside the molecular sieves by canonical Monte Carlo simulation methods using a "compass" forcefield. The DFT calculations were done for optimizing each structure with and without adsorbed water molecules employing generalized gradient approximation with the Perdew-Burke-Ernzerhof exchange-correction functional. Both classical and quantum mechanical calculations have exhibited hydrogen bonding between adsorbed water molecules inside the main 12-membered ring. The Al-O-P angles were observed to decrease after adsorbing water molecules in geometry optimized AlPO 4 -5 and AlPO 4 -11 molecular sieves. DFT calculations illustrate that the initial loading of water in the large cavity is due to the mild acidity in the framework but the isobaric increase in loading is due to the abundant hydrogen bonding between adsorbed water at higher water loading.
Synthesis and Characterization of Nanocrystalline Alumino-phosphate AlPO 4-11 Molecular Sieves
2017
Aluminophosphates molecular sieves (AlPO4-11) were synthesized by hydrothermal reaction method. The syntheses were carried out using sealed stainless autoclave. Investigations of the effect of crystallization temperature, ratio of template to phosphoric pentoxide (R/P2O5), pH adjustment of gel solution and other parameters were studied. Characterization of products were carried out using powder X-ray diffraction (XRD), atomic force spectroscopy (AFM), Fourier transform infrared (FTIR), N2 adsorption-desorption BET surface, thermogravemetry (TGA) and scanning electron spectroscopy (SEM). The XRD patterns revealed that the AEL structure is obtained with high crystallinity for AlPO4-11 at crystallization temperature 190 o C. Type of template (R) and ratio of (R/P2O5) showed a great influence on XRD patterns and nano-level of particle size and optimum ratio of 1.1 was established for (R/P2O5) for AlPO4-11. AFM results showed that a nano-level has been got of 95 nm. Mapo-11 synthesized w...
Synthesis novel aluminophosphate molecular sieves at atmospheric pressure
Current World Environment, 2006
Novel small pore aluminophosphates molecular sieves AlPO 4-Atm1, AlPO 4-Atm2 and AlPO 4-Atm3 have been synthesized using hexamethyleneimine template at atmospheric pressure (373K) for the first time. Gel composition Al 2 O 3 : P 2 O 5 : 1.16HEM: 45H 2 O 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 AlPO 4-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 coordinated aluminium atoms in AlPO 4-Atm1. 31 P MASNMR of the same sample shows the presence of two type of tetrahedrally coordinated phosphorous atoms.
Microporous and Mesoporous Materials, 1998
Several aluminophosphate molecular sieves (AlPO 4 -5, AlPO 4 -22, AlPO 4 -16 and SAPO-35) are formed via a common lamellar aluminophosphate material (AlPO 4 -L) during hydrothermal synthesis from a gel containing Al 2 O 3 , P 2 O 5 , SiO 2 and hexamethyleneimine (HEM ) in aqueous (H 2 O), or non-aqueous (ethyleneglycol, EG) media. Depending on the concentration of the template HEM, AlPO 4 -L transforms into AlPO 4 -5, AlPO 4 -16 and AlPO 4 -22, while SAPO-L transforms into SAPO-35. AlPO 4 -L was isolated in a pure form from H 2 O as well as EG media and characterized by PXRD, SEM, TG/DTA, TG/MS and FTIR spectroscopic techniques. It is a lamellar aluminophosphate, intercalating HEM and H 2 O, and is thermally stable up to 250°C. AlPO 4 -L is believed to form by the rearrangement of macroanionic [3HEMH ]3+Al 3 P 4 O3− 16 sheets formed in the reaction medium.
2001
Mesoporous aluminophosphate (AIPO) and silicon substituted aluminophosphate molecular sieves (SAPO) have been synthesized using ordered array of cetyltrimethylammonium bromide as structure-directing agent at room temperature. The characteristics of these new materials are ascertained by low angle XRD, TGA, Ff-IR, SEM and DRlFf spectra. Vapour phase ethylation of toluene has been attempted over these molecular sieves as a probe reaction. The principal product is pethyltoluene in this reaction. This study also indicates more free uncondensed -OH groups in pure AI PO.
Sorption of water in aluminophosphate molecular sieve AlPO4-5
Microporous and Mesoporous Materials, 1998
The water sorption isotherm over AIPOj-5. in which a low sorption capacity in the initial region followed by ;I steep rise in sorption is observed, is different f'rom those obtained for polar molecules. namelq acrtonitrile, ammonia and methanol. An attempt has been made to explain the water sorption behaviour on the basis of' a condensation phcnomcnon using the structural characteristics of' AlPO,-5. 8' 1998 Elsevier Science B.V.
2002
AlPO 4-5 and AlPO 4-11 were synthesized by dry-gel conversion (DGC) method. Steam-assisted conversion (SAC) and vapor-phase transport (VPT) techniques were applied for this purpose. The synthesis was successful in presence of a certain minimum amount of external bulk water, without which the crystallization failed. Crystallization by VPT method was slower than corresponding SAC and HTS method. SAPO analogs of the samples, SAPO-5 and SAPO-11 were also synthesized by DGC method. Samples made by DGC methods had higher yield than the conventional hydrothermal synthesis (HTS); otherwise the samples showed similar characteristics as that made by HTS. XRD, SEM and N 2-adsorption results showed high crystallinity and purity of the samples made by DGC, and 27 Al MAS NMR spectra indicated the tetrahedral framework nature of Al. SAPO-5 and SAPO-11 were tested for their catalytic activity in isopropylation of biphenyl, and in terms of conversion and selectivity, SAPO-5 was found to be suitable for this application.
Gels
The formation of silicoaluminophosphate gels using boehmite, Al isopropoxide, and di-n-propylamine as a template of silicoaluminophosphate gels as well as their subsequent crystallization into SAPO-11 molecular sieves was studied in detail using X-ray fluorescence spectroscopy (XRF), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption methods. The effect of the chemical and phase composition of silicoaluminophosphate gels on the physicochemical properties of SAPO-11 molecular sieves was shown. The secondary structural units that the AEL lattice is composed of were found to be formed at the initial stage of preparation involving aluminum isopropoxide. Several approaches to control their morphology and secondary porous structure are also proposed.