In situ MAS NMR spectroscopic investigation of the conversion of methanol to olefins on silicoaluminophosphates SAPO-34 and SAPO-18 under continuous flow conditions

Applying in situ C-13 MAS NMR spectroscopy under continuous flow (CF) condi tions and on-line gas chromatography, the conversion of methanol on silicoa luminophosphates SAPO-34 and SAPO-18 was studied. At reaction temperatures of 573 to 673 K, a strong increase of the yield of propylene and ethylene w as observed by on-line gas chromatography. Simultaneously with the occurren ce of in situ 13C CF MAS NMR signals at 126-135 ppm indicates the formation of a mixture of aliphatic and/or cyclic olefins and alkylated aromatics wi th carbon numbers of C-6-C-12. All these support the "hydrocarbon pool" mec hanism for the formation of light olefins on the SAPO-34 and SAPO-18.