Synthesis and Characterization of High-silica SAPO-5 from Metakolin

High-silica silicoaluminophosphate(SAPO-5) molecular sieves were hydrothermally synthesized using metakaoline with a certain activity as the silicon and aluminum sources,phosphoric acid as the phosphorus source and triethanolamine combined with cetyltrimethylammonium bromide(CTMABr) as the template agents.The sample was characterized by means of X-ray diffraction spectroscope(XRD),Infrared spectrum(IR),scanning electron microscope(SEM) and 29Si,27Al MAS-NMR and X-ray photoelectron spectroscope(XPS),temperature-programmed desorption of adsorbed NH3.The results show that the crystallization of the SAPO-5 can be promoted by the addition of CTMABr.The synthesized SAPO-5 reveals pillar-like morphology with dimension of 20μm×5μm×5μm.The local environment of Si and Al changs greatly after reaction and many four-coordinated structures such as Al(OP)4 and Si(AlO)4 are produced with the Si/Al ratio of 0.56.The acidity amount of the product is 0.578mmol/g and the ratio of the strong acid sites to the weak acid sites is 0.684.