Structure control of metal aluminum phosphate (MeAlPO-5) molecular sieves and applications in polyethylene glycol amination

The structure and morphology of both pure AlPO-5s and nickel containing AlPO-5s were affected by the preparation conditions such as pH value, nickel incorporated method (hydrothermal method or traditional incipient wetness impregnation). The dense tridymite phase of AlPO-5 can be formed by two controlling factors. One is controlling the pH at lower value to the AlO4 and PO4 moleculars to form AlPO4 with dense phase, and the other is used the excess nickel adding to increase the crystallinity of AlPO-5 to form dense tridymite phase. The reactivity of PEG-400 amination was also affected preparation methods and conditions. At higher nickel loading, the nickel supported on AlPO-5 prepared by traditional incipient wetness impregnation forms the surface nickel species, and both the surface nickel species and nickel incorporated species form by the hydrothermal method. The amination catalysis indicates that the reactivity of PEG-400 prepared by incipient wetness impregnation method was higher than that prepared by hydrothermal method. The formation of the dense tridymite phase of AlPO-5 can be further determined by the X-ray powder diffraction (XRD). The nickel containing AlPO-5s prepared with lower pH value possesses only the tridymite phase and exhibit higher catalytic reactivity. It appears that the trydimite structure can improve the catalytic activity for PEG-400 amination due to the grain size of the formed crystal of NiAlPO-5 is smaller than the catalyst without the formation of the trydimite phase.