Effects of synthesis conditions on the yields and properties of HZSM‐5

In the SiO₂‐Al₂O₃‐TPAOH‐NH₄OH system through a two‐step procedure, the effects of synthesis parameters on the yields and properties of HZSM‐5 were studied. As the feeding n(SiO₂)/n(Al₂O₃) ratio increased, the yields of synthesized samples were between 11% and 14% while the crystallinity tended to decrease at the ratio > 300. At the ratio of 150, the yield was 13.7% and the ratio of actual yield to theoretical yield was 93%. The sample shaped ellipse‐like particles of 3 × 10^?6 m. At the n(NH₃)/n(SiO₂) ratio of 1.5, the yield was 13.1% and the sample showed regular ellipse‐like particles of 2 × 10^?6 m. Too high dosage of NH₄OH lowered the yield and the crystallinity. The addition of seed crystal favored the HZSM‐5 synthesis in high crystallinity. At the addition amount of 4%, the yield reached 13.9% and the sample shaped in spherical particles of 0.5 × 10^?6 m. Synthesized HZSM‐5 with a surface area of 455 m²·g^?1 and intrinsic acidity showed highly catalytic activity toward the methanol conversion to olefins reaction.