Effect of crystallization time on properties and catalytic performance of nanostructured SAPO-34 molecular sieve synthesized at high temperatures for conversion of methanol to light olefins

• Successful synthesis of SAPO-34 catalyst via high temperature hydrothermal method
• Study the effect of crystallization time on physicochemical and catalytic properties
• Producing spherical morphology with accumulation of cubic crystals of SAPO-34
• Excellent potential of synthesized catalysts in the methanol to olefins process
• Increasing catalytic lifetime from 4 to 20 h using high temperature hydrothermal method

SAPO-34 molecular sieves were synthesized via high temperature hydrothermal method. The effects of crystallization time and temperature on physicochemical properties and catalytic performance were studied toward methanol to light olefins. The samples were characterized by XRD, FESEM, PSD, EDX, BET and FTIR techniques. The XRD patterns confirmed the influence of crystallization time and temperature on the crystallinity, phase purity and crystallite size. Also, all synthesized catalysts have nanosized crystallites, obtained by Scherrer formula. The relative crystallinity was enhanced by the increasing of crystallization time and then decreased which can be correlated well with recrystallization at high temperature and long crystallization time. By synthesis at high temperature, more nuclei were produced that leads to lower particle size compared to low temperature synthesis procedure. In addition, it was concluded that the impact of crystallization temperature on particle size is much more than that of crystallization time. It was found that the hydrothermal synthesis conditions greatly affected on the morphology, particle size, purity and textural properties. The synthesized catalyst at 300 °C and 3 h has the best performance in terms of the lifetime and olefins selectivity. This catalyst showed 90% selectivity toward light olefins and 94% methanol conversion for more than 600 min. The catalysts synthesized via high temperature hydrothermal method have higher lifetime than the one produced by the conventional method, indicated more effectiveness of this method.

The aim of this study was to synthesize SAPO-34 catalyst via high temperature hydrothermal method and attempt to enhance catalytic lifetime in methanol to olefins process. The effect of crystallization time and temperature has been investigated. The SAPO-34 samples were characterized by XRD, FESEM, PSD, EDX, BET and FTIR techniques. It was found that the synthesis conditions greatly affected the catalyst morphology, particle size, purity and textural properties. The catalyst relative crystallinity enhanced by the increasing of crystallization time and reached a maximum, then decreased. By the synthesis of SAPO-34 via high temperature hydrothermal method, more nuclei have been produced that led to the formation of small particle size. The synthesized catalysts were employed in MTO process and concluded that the fabricated catalyst at 300 °C and 3 h has the best performance in terms of the lifetime and olefins selectivity.Figure optionsDownload as PowerPoint slide