SYNTHESIS OF ZSM-5 IN FLUORIDE MEDIA AND CHARACTERISATION S. HARI HARAN, DR. M. PALANICHAMY & DR. V. MURUGESAN *, Department of Chemistry, Anna University, Chennai Introduction Synthesis of ZSM-5 in fluoride media has several advantages: Large surface area, High crystallinity, Large crystal size Incorporation of weak and medium acid sites Fluoride ion is the mineralizer of silica for the construction of zeolite framework. Ion exchange of as-synthesized zeolite is not necessary, as it involves sodium free synthesis. The problem of aluminium transport from gel to the framework is eliminated using phosphate co-complexant. The competition of phosphate for aluminium complexation to fluoride was verified by potentiometric method. In the present study ZSM-5 (Si/Al = 50,100 and 150) was synthesized in aqueous – alcoholic fluoride media between pH 4 and 6 in the presence of phosphate co- complexant. The catalysts were characterized by XRD, FTIR and TGA. Their catalytic activity was examined for disproportionation of toluene between 200 and 450 ̊ C. The products were analyzed by GC-MS. Experimental Synthesized ZSM 5 (Si/Al= 50, 100,150) in Fluoride media was carried out using the following gel composition. 1.1 EtOH: 0.07 C 12 H 28 NBr :1.0 SiO 2 : 0.2 Al 2 O 3 : 0.02 P 2 O 5 : 1.3 NH 4 F: 80 H 2 O. Potentio metric titration of phosphate Vs sodium hydroxide in the presence and in the absence of aluminium was carried out at 30 ̊ C. The XRD analysis of the as-synthesized and calcined catalysts was carried out on PANalytical X’pert PRO diffractometer equipped with a Cu Kα (1.54 Ǻ) radiation source and a liquid cooled germanium solid state detector. The TGA of the as-synthesized and calcined catalysts was carried out on Waters Symultanious Differential and Thermo gram Q 600. The FTIR analysis of the as-synthesized and calcined catalysts was carried out on FT-IR spectrum (Perkin-Elmer Spectrum) The GC-MS analysis of the products obtained for disproportionation of toluene was carried out on Shimadzu 2010 GC with GC MS qp Graphical Characterization Result and discussion XRD patterns The XRD patterns are more intense than a commercial catalyst. The intensity of the patterns decreased with the increase in the Si/Al ratio of the catalysts. High silica zeolites require longer crystallization time than the low silica zeolites. FT-IR Spectra Broad band at 3447 Cm-1 stretching vibration of Si-O-Si groups cm -1 internal-OH 2 bending of water molecule. Broad band at 1108 Cm -1 is due to asymmetry stretch of Si-O-Si groups. 803 Cm -1 due to asymmetry stretch. The bending mode is close to 496 Cm -1. The as-synthesized samples show the characteristic patterns of the template at 2986 and 2920 Cm -1 due to -CH2- stretching vibrations. In the spectrum of the calcined samples the peaks due to the template are absent. The band clears below 468 Cm -1 is repeat five member ring. TGA Analysis Thermal decomposition between and ̊ C is due to dergradation and desorption of the template. The initial weight loss blow 100 ̊ C is due to desorption of water. Potentiometric Titration Three pK as 2.12, 7.21 & for Phosphoric acid Vs NaOH (black curve) Phosphoric acid and Aluminium Vs NaOH. The equilibrium pH is lowered compared to that of phosphoric acid Vs NaOH. It proves complexation between phosphoric acid and aluminium. An additional pKa occurs at 9.5 pH is due to ionization of AlOH group. GC- MS sample analysis The catalytic activity of the catalyst was tested for the disproportionation of toluene between 200 and 450 C. At 300 C para xylene starts to form and at 400 C a maximum conversion of 56 % with 100 % selectivity to para xylene is obtained. The following reaction scheme is suggested for disproportionation of toluene. The external acid sites must be rapidly blocked by coke and the pore size might be partly reduced by coke deposition in order to have 100% selectivity to para xylene. Summary and conclusion Synthesis of ZSM-5 in fluoride media with phosphate cocomplexant was successfully carried out. The zeolites were much crystalline. Disproportionation of toluene showed 100% selectivity to the most desired product para-xylene. ZSM-5(50) is more active than others. Hence for disproportionation ZSM-5 zeolites with low Si/Al ratios are better than the high silica zeolites. ZSM-5 synthesized in fluoride media is better than the one synthesized in alkaline media, as it gives 100% para xylene selectivity in the disproportionation of toluene even in the absence of surface modification. It is a remarkable achievement. Reference B. Louis, L Kiwi Minsker Micropor & mesopor Mater 74 (2004) T. Loiseau, G. Ferey, journ of fluor chem 128 ( 2007) R. Aiello, F.Crea, E. Nigro, F.Testa,R.Mostowicz, A. Fonseca, J. B. Nagy, Micropor & Mesopor Mater 28 (1998)