Synthesis and catalytic performance on methanol conversion of NiAPSO-34 crystals - (I): effect of preparation factors on the gel formation

In order to synthesize the NiAPSO-34 crystal with a pure CHA structure having a uniform size and stable catalytic activity, factors having influence on the crystallization at gel preparation were investigated. The results showed that the mixing order of starting materials influences on the crystallization rate. The concentration of the template was related to the morphology of crystals and the crystallinity, while the particle size obtained was controlled by the silica source and the amount of nickel. Moreover, it was elucidated that the mixing orders of starting materials influences on the crystal growth rate. Seed crystal addition (SAPO-34; 0.8 mu m) and ultrasonic-wave treatment after the gel formation were effective in decreasing smaller particle size and in narrowing the size distribution. (C) 1999 Elsevier Science B.V. All rights reserved.