Fluorine-free synthesis of large ZSM-39 crystals incorporated with alkaline earth metals in an environment-friendly system

Large crystals of ZSM-39 clathrate compounds containing alkaline earth metals Mg and Ca were synthesized in a fluorine-free media. The influences of alkali sources and heteroatoms on crystal growth and morphology were also investigated in the environment-friendly system. Experimental results indicated that alkali source of KOH benefited to prepare ZSM-39 zeolite with high crystallinities and the incorporation of heteroatoms altered their unit-cell parameters and crystal morphologies under the given conditions. Resultant K-Mg-ZSM-39 crystals were uniform particles and about 200 pm in diameter. Thermogravimetric curve displayed about 6.7 wt% weight loss for them in air. The black calcined sample implied that tetramethylammonium bromide as a structure-directing agent was trapped in cages of ZSM-39 crystals. (C) 2013 Elsevier B.V. All rights reserved.