Facile synthesis of SAPO-34 with excellent methanol-to-olefin activity in a short time via conventional hydrothermal method
To save time and economic cost in synthesis of SAPO-34 zeolites, the effects of hydrothermal time on structure and catalytic methanol-to-olefin (MTO) of SAPO-34 zeolites were investigated in detail. A series of SAPO-34 zeolites (SAPO-34-xh, x=3, 4, 8, 12, 24 and 48) were obtained by changing the synthesis time at 210 oC using the traditional hydrothermal method. 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-34-4h with higher Si/(Si+Al+P) ratio shows 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-34-4h sample can still maintain good MTO performance even under either long time storage without complicated processing or using several cycles after regeneration. This facile synthesis procedure may be beneficial to large scale industrial catalyst production because of its short synthesis time.