Thorough study of the effect of metal-incorporated SAPO-34 molecular sieves on catalytic performances in MTO process

• We synthesized SAPO-34 and its modified samples with different five metal ions.
• Metal incorporation gave rise to the different micropore area and acidity.
• All the SAPO-34 and MeAPSO-34 samples are active and selective in MTO process.
• Metal incorporation improved the catalyst lifetime and favored light olefin yield.
• The order of increasing in lifetime increased as Ce- > La- > Co- > Ni- > Fe- > SAPO-34.

SAPO-34 and MeAPSO-34s (Me = Fe, Co, Ni, La and Ce) molecular sieves were synthesized and used as catalysts for conversion of methanol to light olefins. X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption inductively coupled plasma mass spectrometry, Fourier transform infrared spectroscopy and temperature programmed desorption techniques were used to characterize the synthesized catalysts. Thermogravimetric analysis was used to investigate the amount of coke deposited on the spent catalysts during the reaction. The synthesized MeAPSO-34s had the same chabazite topology structure, while metal incorporation gave rise to the different micropore area and acidity. All the SAPO-34 and MeAPSO-34 molecular sieves were very active and selective catalyst for light olefins production. Metal incorporation improved the catalyst lifetime and favored the ethylene and propylene product. Concerning the yield of light olefins at 425 °C and 1 bar, NiAPSO-34 favored ethylene production and CeAPSO-34 and LaAPSO-34 were helpful for propylene production. Light olefins yield decreased with time on stream for all the samples; although, this decrease rate is lower for MeAPSO-34 than for the parent SAPO-34. The catalyst lifetime increased in an order as follows: Ce- > La- > Co- > Ni- > Fe- > SAPO-34. The rare earth modified catalysts exhibited lower methanation than parent SAPO-34 and transition metal modified catalysts.

Figure optionsDownload as PowerPoint slide