Synthesis of zincosilicate mordenite using citric acid as complexing agent

The zincosilicate analog of zeolite mordenite was hydrothermally synthesize d in the presence of citric acid and characterized with several spectroscop ic techniques. The zeolite thus prepared had a higher crystallinity and Zn concentration in the framework compared with the one obtained in the absenc e of citric acid. XRD and FTIR provided evidence for the incorporation of Z n in the framework. Results of XAFS indicated a tetrahedral structure of Zn in the lattice framework with a Zn-O distance of 0.1938 nm. It is speculat ed that the citric acid might decrease the concentration of Zn2+ in the syn thesis mixture, thereby preventing the unfavorable formation of oxide or hy droxide species. (C) 2001 Elsevier Science B.V. All rights reserved.