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Nitrogen sorption isotherm and pore size distribution (inset) of the calcined a AlPO-5A, b 0.02FeAlPO-5, c 0.05FeAlPO-5, d 0.08FeAlPO-5, e 0.10FeAlPO-5 molecular sieves
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With a characteristic of S-shape isotherms for water vapor adsorption, aluminophosphate molecular sieve with AFI type (AlPO-5) has been considered as an up-and-coming adsorbent for the utilization in the adsorption cooling and heating (ACH) system. In order to improve its adsorption performance, iron doped AlPO-5 (FeAPO-5) with variable Fe loading...
Citations
... The water uptake was observed to occur mainly in the 30-60 RH% range, while the capacity of FAM-Z01 is typically higher than that of non-substituted AlPO 4 -5 at 25 • C. These observations can be attributed to the following reasons: (a) the addition of iron enhances the surface area, (b) after incorporating iron, the sorption capacity is also enhanced as a consequence of structural and surface changes, which increase the interaction of polar molecules such as water with the surface [110,111]. FAM-Z05 (FAPO-34) has also been applied as a water adsorbent [108]. Although AlPO-34, SAPO-34, and FAPO-34 have the same framework structure, the SAPO-34 capacity increases more at the low relative humidity range of up to 8 RH%. ...
Freshwater resources are being heavily depleted and not replenished at the same high rate, thus, atmospheric water vapor harvesting has earned growing interest. Development of high-performing desiccant or adsorbent materials offering high sorption capacity and selectivity as well as regeneration capability in atmospheric conditions is crucial to tackle water scarcity. The required properties to generate potent water sorbents include pore accessibility, high specific surface area and porosity to enable high capture capacity and kinetics, and hydrothermal resilience to resist cyclic sorption and desorption. Further, polarity, hydrogen bonding, adhesion ability of water molecules to adsorbent surface, and hydrophilic functional groups can boost water adsorption. A highly promising class of water vapor adsorbents is the aluminophosphate molecular sieves (AlPOs), which are microporous zeotype materials. In this review, AlPO-based adsorbents are discussed for water sorption applications and a link is established between performance of materials and their chemical and morphological properties. Synthesis-properties-performance relationships are elucidated in light of synthesis techniques and adsorption behavior, and prospects to enhance AlPOs' water vapor sorption performance toward large-scale water harvesting applications are highlighted.
... Several heterogeneous catalysts have been reported to be active in vapor-phase Omethylation of catechol and methanol, including pure and doped metal oxides [6][7][8], supported tungsten compound [9] and metal phosphates [10][11][12][13][14][15][16], etc. Amorphous aluminophosphates, which possess both acid and base sites, are considered effective catalysts for vapor-phase O-methylation of catechol with methanol [12][13][14][15][16]. The physicochemical properties of aluminophosphate have been reported to depend on modifying catalyst with various metals, optimizing catalyst compositions, and improving catalyst preparation routes [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Generally, aluminophosphates with specific structure are usually synthesized with various surfactant templates. ...
... Hence, it is still important to develop a simple approach to fabricate aluminophosphates with high activity and selectivity for vaporphase O-methylation of catechol with methanol. It is commonly acknowledged that various metals, especially transition metal, introduced to aluminophosphates could alter the acid-base property of aluminophosphates [17][18][19][20][21][22][23][24][25][26]. ...
Guaiacol produced by O-methylation of catechol with methanol over solid catalysts is a green environmental synthesis route. In order to achieve high catalytic efficiency, it is quite necessary to employ low-cost catalysts with high activity and stability. Herein, series of aluminophosphate catalysts were synthesized by a simple precipitation route modified by Zr. The characterization results indicated that the prepared Al-P-Zr catalysts possessed appropriate weak acid and weak base sites, which were beneficial for the O-methylation of catechol with methanol. Different Zr amount and calcined temperature exerted a significant influence on physicochemical properties of the catalysts and catalytic performance. The Al-P-Zr catalysts containing Zr/Al molar ratio of 0.012 calcined under 400 °C showed the optimal catalytic activity and long-term stability for vapor-phase selective O-methylation of catechol with methanol.
... The sample analysis result of calcinated product is consistent with the standard card of the K-Fe-Al-PO 4 phase, but the characteristic diffraction peak moves to a high diffraction angle, owing to Na + radius is less than that of K + , and the sodium isomorphically replaces potassium which causes the spacing between crystal planes to become smaller. When Al 3+ reacts with − PO 4 3 to produce AlPO 4 , Fe 3+ can participate in the reaction at the same time, so that part of Al 3+ is replaced by Fe 3+ , and the radius of Fe 3+ is larger than Al 3+ , resulting in an increase of interplanar spacing, so the characteristic absorption peak of AlPO 4 moves to the direction of low diffraction angle [32]. The detection and analysis also found that there is a small amount of metaphosphate. ...
The acidic wastewater produced by the wet production of activated clay contains valuable components such as iron and aluminum. The precipitation method was successfully introduced to separate iron and aluminum from the activated clay production wastewater step by step, which can not only recover the valuable components, but also avoid environmental pollution. In the separation process, gypsum, iron aluminum phosphate, alumina, and sodium sulfate were prepared, and the phase compositions of separation products were analyzed by XRD and IR. The main influencing factors in the separation of iron and aluminum components were studied by single factor experiment. The results show that at the optimized conditions, phosphorus/iron molar ratio 6.0, the system pH 3.0, the reaction temperature 343 K, and the reaction time 90 min, the iron( iii ) ion in the system can form a sodium-containing aluminum iron phosphate double salt, and the filtrate after separating Fe ³⁺ and part of Al ³⁺ can meet the requirements for forming high-purity Al 2 O 3 . During the phosphate precipitation process, the hypothesis should be correct that Al ³⁺ reacts with PO 4 3 − {\text{PO}}_{4}^{3-} to form an AlPO 4 skeleton, Fe ³⁺ isomorphically replaces Al ³⁺ in the [AlO 4 ] tetrahedron, and adsorption occurs simultaneously, with Na ⁺ occupying the terminal acid sites, P(Al)–OH.
FeAPO-34 with a chabazite (CHA) topology structure was successfully synthesized under ionothermal conditions using 1-ethyl-3-methylimidazoliumchloride (EMIMCl) ionic liquid in the presence of ethylenediamine (EDA). The material was characterized using powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental analyses, and solid-state NMR spectroscopy. Incorporation of iron within the covalent framework of the material was confirmed by the presence of broad signals between 1000 and 14,000 ppm in the 31P NMR spectrum, corresponding to the P(OFe)x(OAl)4-x species.
We report effects of crystallization conditions and gel composition on the hydrothermal synthesis of large zinc-doped AlPO4-15 (ZnAlPO4-15) single crystals by using melamine (MA) as structure directing agent (SDA). By optimizing the following synthesis conditions: amount of MA, molar ratio of ZnO/Al2O3, molar ratio of P2O5/Al2O3, crystallization temperature and duration, the pure phase of ZnAlPO4-15 (size up to 95 μm) with good optical transparency can be obtained at 200 °C with 40 h in the system of Al2O3:1.07MA:0.27ZnO: 1.15P2O5:667H2O. To the best of our knowledge, it is the first report of synthesizing ZnAlPO4-15 by using MA as SDA.
In this research, an in-situ microwave hydrothermal synthesis strategy for chromium-substituted aluminophosphate (CrAlPO-5) zeolite coating on aluminum foil was introduced. The influences of seed coating, molar ratio of Cr2O3/P2O5, crystallization temperature and time on the performance of adsorbent coating were investigated systematically. The crystal phase, composition and the morphology of the as-synthesized CrAlPO-5 adsorbents were characterized by X-ray diffractometer, Fourier infrared spectrometer and Scanning electron microscopy, and its adsorption and desorption performances were evaluated by water vapor adsorption and temperature programmed desorption. Results showed that CrAlPO-5 zeolite coating could be conveniently synthesized on aluminum foil by in-situ microwave hydrothermal method with the molar ratio of Cr2O3/P2O5 of 0.01–0.06, the temperature of 180–210 °C and within 15–40min. Compared with the CrAlPO-5 adsorbent prepared without seed coating, the one synthesized by seed-inducing method had a more complete crystal phase, higher relative crystallinity and larger specific surface area, and displayed a smaller and more perfect hexagonal prism crystal morphology as well as a thicker coating (100 μm). Moreover, it exhibited slightly higher saturation adsorption capacity. All results indicate that the novel synthesis technique of CrAlPO-5 zeolite coating on aluminum foil provides a guidance for the fabrication of desiccant coating on heat exchanger in ACH system.
