Facile synthesis of SAPO-34 with excellent methanol-to-olefin activity in a short time via a conventional hydrothermal method

Abstract

To save time and economic cost of the synthesis of SAPO-34 zeolites, the effects of hydrothermal time on the structure and methanol-to-olefin (MTO) catalytic activity of SAPO-34 zeolites were investigated in detail. A series of SAPO-34 zeolites (SAPO-34-x h, x = 3, 4, 8, 12, 24 and 48) were obtained using the traditional hydrothermal method by changing the synthesis time at 210 °C. The obtained catalysts were characterized by XRD, N₂ adsorption–desorption, SEM, TG-DTA, ICP, ²⁹Si and ²⁷Al MAS NMR and NH₃-TPD techniques. Among these samples, SAPO-34-4 h with a higher Si/(Si + Al + P) ratio shows a much longer lifetime (518 min) and higher light olefin selectivity (82.0%) in the MTO reaction, which can be attributed to the unique Si distribution and low acidity. Moreover, the SAPO-34-4 h sample can maintain good MTO performance even under long time storage without complicated processing or after several cycles of regeneration. This facile synthesis procedure may be beneficial for large scale industrial catalyst production because of its short synthesis time.