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

Abstract

Applying in situ 13C MAS NMR spectroscopy under continuous flow (CF) conditions and on-line gas chromatography, the conversion of methanol on silicoaluminophosphates 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 was observed by on-line gas chromatography. Simultaneously with the occurrence of in situ 13CC CF MAS NMR signals at 126–135 ppm indicates the formation of a mixture of aliphatic and/or cyclic olefins and alkylated aromatics with carbon numbers of C6–C12. All these support the “hydrocarbon pool” mechanism for the formation of light olefins on the SAPO-34 and SAPO-18.