Synthesis And Characterization Of Thermally Stable Mesoporous Aluminophosphate

Metal phosphates have wide range of applications in many fields including ion exchange, high temperature ion conductivity, and catalysis. High specific surface area and uniform larger pore structures are the major requirements for further utilization of metal phosphates. The discovery of mesoporous silica materials has given the enormous stimulates to the synthesis of mesoporous metal phosphates materials, not only because mesoporous materials possess the high surface area and pore structure, but also because they are proper materials for supporting catalytically active sites with large organic functionalities, and for selecting organic transformations. As one of the most important part of metal phosphates materials, aluminophosphates can be used in many fields. Since 1982, various structure aluminophosphate-based molecular sieves have been brought to light and used in various catalysis processes. In recent years, mesoporous aluminophosphates (AlPOs) have attracted much attention, and the advance in the fabrication of mesoporous AlPOs is of practical use for overcoming the difficulty in the general synthesis of other mesoporous metal phosphates. Liquid-crystal templating route is so far the most popular way to synthesize lamellar or hexagonal mesoporous AlPOs. However, most of the obtained materials are thermally unstable and easily collapse upon removal of the surfactant by calcinations. These progresses, though limited, clearly demonstrated that the thermal stability and the long-range order of the mesoporous AlPOs materials could be further improved by pursuing new synthesis approaches. Here, we report a novel route for the synthesis of ordered mesoporous AlPOs with high thermal stability from a preformed precursor of microporous alumnophosphate using n-octadecylamine as template. This approach is based on a successful strategy used for the synthesis of steam-stable mesoporous aluminosilicate materials assembled from nanoclustered zeolite precursors. Mesoporous aluminophosphate (AlPOs) with high thermal stability have been synthesized from a preformed precursor of microporous aluminophosphate in the presence of n-octadecylamine surfactant by two-step procedure. The products were characterized by XRD, TEM, BET, MAS-NMR, ICP and FT-IR techniques. Powder XRD patterns of various samples suggest that the synthesized AlPOs materials are pure mesoporous phase, and possess very high thermal stability. The mesoporous characteristic of the materials can be further confirmed by the TEM image. The results of N2 adsorption/desorption isotherms and the pore size distributions present type IV isotherms, which is characteristic of...