Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 3(9), 83-85, September (2013) Res. J. Chem. Sci. International Science Congress Association 83 Short Communication Simple Synthesis of Large pore Mesoporous Iron Substituted Aluminophosphate Molecular SievesDevi M.R. and Kannan C.Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli-627012, Tamilnadu, INDIAAvailable online at: www.isca.in Received 9th August 2013, revised 24th August 2013, accepted 16th September 2013Abstract Iron containing mesoporous aluminophosphate (FeAlPO) synthesized by simple synthesis using anionic sodium dodecyl sulphate (SDS) as structure directing agent leads to an active, selective and recyclable catalyst for the esterification reaction. This material was characterized by FT-IR, N adsorption desorption, temperature programmed desorption (TPD) and thermal analysis (TG/DTA). The influence of this synthesis procedure makes the material more stable, reusable and it exhibits uniform large pore diameter (27 nm) with the surface area of 116m/g. This material exhibits highly acidic nature and hence the activity of the catalyst FeAlPO was analyzed for esterification of acetic acid and n-butanol in liquid phase and the experimental conditions were determined. The same reaction has been done again to find out the reusability of the catalyst and it is found active with high yield of ester.Keywords: Mesoporous FeAlPO, anionic surfactant, thermal stability, large pore diameter, esterificationIntroductionThe phosphate and alumina based materials have vast catalytic applications1-4. Mesoporous aluminophosphates are a class of materials which possess flexibility in its framework and make the heteroatoms to easily substitute in its structure. This amendments leads to the production of acidic and redox sites. The metal substituted mesoporous materials have shown excellent properties as catalysts. Particularly iron containing mesoporous AlPO have shown excellent catalytic activities6-8. Hence, in this study, a new approach has been made to synthesize the iron substituted AlPO by using anionic surfactant as organic templating agent. This new synthesis method makes the material more thermally stable and it creates extremely large pores. These pores provide enough space to carry out the reactions in a right way. Moreover, the metal iron in its 2 and 3 oxidation states in the AlPO framework makes the material more acidic. The esterifica the efficiency of this catalyst was analyzed by esterification of acetic acid and n-butanol.Material and Methods Experimental: Mesoporous iron substituted aluminophosphate was prepared by using anionic surfactant SDS as template by simple synthesis method with the following gel composition 0.8Al:1P:0.2FeO:0.5SDS:300HO. Aluminium hydroxide (Merck, GR), Phosphoric acid (Nice chemicals, GR) and Iron (III) chloride (Merck, GR) were chosen as the sources for aluminium, phosphorous and iron respectively. In an aqueous solution of SDS, aluminium hydroxide was added and stirred vigorously. To the above mixture, aqueous solution of phosphoric acid and iron (III) chloride was added and stirred continuously for 2 h to achieve homogeneous mixture. The resulting gel was heated and dried at 150C in open air. The resulting solid was thoroughly washed with deionised water. The solid was then ltered, dried and calcined at 600C for 6 h to remove the organic template.The mesoporous FeAlPO was characterized by using FT-IR, Nitrogen adsorption desorption measurements, Thermal analysis (TG/DTA) measurements and temperature programmed ammonia desorption analysis.Esterification reaction was performed in a batch reactor equipped with a reflux condenser and a thermometer. The required amount of n-butanol, acetic acid and 0.5g of calcined FeAlPO catalyst was taken in the reactor and stirred for 2 h. The temperature of the reaction mixture was slowly raised up to 200C and continues refluxing for 6h. The change in mole ratio of alcohol: acid was also studied to attain high percentage of conversion and selectivity. The reaction products were separated from solid FeAlPO catalyst by filteration and the product was analyzed by gas chromatography (Chemito 1000)Results and Discussion The FT-IR spectrum of calcined mesoporous FeAlPO confirms the complete removal of the surfactant from the material and stability of the material after calcination. The strong band at 3,464 cm 1 is assigned to the hydroxyl group (O–H) vibration of O molecules and C-H stretching bands at 2900 - 2800 cm-1 in addition to C-H deformation bands around 1460 cm-1 are absent after calcination. The strong band at 1142 cm 1 and bending Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 3(9), 83-85, September (2013) Res. J. Chem. Sci. International Science Congress Association 84 mode near 465cm-1 are attributed to the symmetric stretching and bending mode of PO3-. Thus, it is confirmed from the spectra that there is no collapse in the tetrahedral framework of FeAlPO after calcination.Nitrogen adsorption desorption measurements of FeAlPO4 are shown in figure-1. The BET surface area and pore diameter of the FeAlPO is found to be as 106m/g and 27 nm. The enhancement in the pore diameter of the material was achieved by the new synthesis method and isomorphous substitution of Fe into the framework of AlPO. This is attributed to the Fe2+and Fe3+ cations which has larger ionic radii than Al3+. Figure-1 (a) N adsorption – desorption isotherm of calcined FeAlPO(b) Pore size distribution of mesoporous FeAlPO4 The thermogravimetric analysis curves of as-synthesized FeAlPO sample shows mainly three weight loss regions. The initial weight loss between 90 - 150C owing to the loss of water physisorbed on the surface of the material. The corresponding second weight loss around 300 C may be ascribed to the entire decomposition of the anionic template inside the framework. The gradual weight loss between 500 and 600C is related to loss of water molecules due to the condensation of Fe-OH, P-OH, Al-OH groups in the framework10. There are no weight losses with the further increase of temperature and the material remains stable up to 1000C.The acidity of FeAlPO4 sample was investigated by temperature-programmed ammonia desorption experiment (NH-TPD) (figure-2). The information on the acid strength distribution in FeAlPO system can be obtained from TPD spectra. In the TPD curve of mesoporous FeAlPO, the desorption of ammonia distributes at two different types of temperature. The desorption at 150C to 170C reveals the presence of medium acid sites (Lewis acid sites Al3+, Fe3+) and another desorption around 250-300C proved the presence of strong bronsted acid sites because of the substitution of Fe2+ in the framework of AlPO system11. Figure-2 Temperature programmed desorption (NH-TPD) of calcined FeAlPOThe efficiency of the catalyst was investigated by esterification of acetic acid with n-butanol. Table-1 shows the n-butyl acetate conversion and selectivity percentage of the reaction. The activity of the catalyst (FeAlPO) almost remains the same after regeneration. It is shown in table-1(entry 4) Table-1 Effect on esterification of n-butanol and acetic acid S.No Esterification of n-butanol and acetic acid using FeAlPO 4 Mole ratio (acid:alcohol) Conversion of n-butyl alcohol (%) Product selectivity of n-butyl acetate (%) 1 1:1 57 97.5 2 2:1 79 99.3 3 3:1 92 99.5 4 3:1 91.2 99.2 Temperature=200C, Time=3h, Catalysts dosage=0.5g ConclusionIn conclusion, mesoporous FeAlPO with high thermal stability and large pore diameter was synthesized successfully by simple method. The surface acidity and uniform large pore size distribution of the material enhances the esterification reaction of alcohol and acid. The reusability of the catalyst makes an additional advantage in the reaction side. Acknowledgement The authors are thankful to IIT – Madras and IIT-Bombay for BET surface area analysis, TPD analysis and TG/DTA analysis. 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