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 havi ng a uniform size and stable catalytic activity, factors having influence o n the crystallization at gel preparation were investigated. The results sho wed that the mixing order of starting materials influences on the crystalli zation rate. The concentration of the template was related to the morpholog y of crystals and the crystallinity, while the particle size obtained was c ontrolled by the silica source and the amount of nickel. Moreover, it was e lucidated that the mixing orders of starting materials influences on the cr ystal growth rate. Seed crystal addition (SAPO-34; 0.8 mu m) and ultrasonic -wave treatment after the gel formation were effective in decreasing smalle r particle size and in narrowing the size distribution. (C) 1999 Elsevier S cience B.V. All rights reserved.