Rapid synthesis of small crystal FeZSM-5 by a two-stage varying-temperature technique

Small crystal FeZSM-5 was synthesized by a two-stage varying-temperature te chnique, in which the reaction mixture was first kept at a relatively low t emperature for a period, and then abruptly raised to the required crystalli zation temperatures. The effects of sol concentration, alkalinity, temperat ure as well as templates on crystal size were investigated. The results sho wed that the crystal size of the ultimate product could be tailored through controlling the nucleation period and rate in the first stage via changing alkalinity, templates, and water content in hydrogel. Typically, a product with uniform crystal size of about 300 nm was obtained from a reaction mix ture with molar ratio 1SiO(2) : 0.02Fe(2)O(3) : 0.6R : 0.3Na(2)O : 50H(2)O (R = n-butylamine) under suitable crystallization conditions for 50 h.