SMALL-PORE ALUMINUM PHOSPHATE MOLECULAR-SIEVES WITH CHABAZITE STRUCTURE - INCORPORATION OF MAGNESIUM IN STRUCTURES -34 AND -44

MgAPO and MgSAPO with -34 and -44 framework structures have been synth esized with various amounts of magnesium. Magic-angle spinning (MAS) N MR results showed the presence of three phosphorus environments: P(4Al , 0Mg), P(3Al, 1Mg) and P(2Al, 2Mg) in MgAPO-44 and MgSAPO-44. In MgAP O-34, some of the NMR peaks are split, possibly owing to the presence of non-equivalent T sites. It was indicated from Si-29 MAS NMR results that in MgSAPOs, the magnesium content of the samples affects the sil icon environment: with increased magnesium content, more silica-rich r egions were formed. Structural acidity, determined from temperature-pr ogrammed desorption of ammonia, supported the results on the formation of silica-rich regions in the structure.