Sains Malaysiana 41(10)(2012): 1245–1251

 

Effects of Titration Parameters on the Synthesis of Molybdenum Oxides Based Catalyst

(Kesan Parameter Penitratan terhadap Sintesis Mangkin Molibdenum Oksida)

 

D.D. Suppiah*, F.A. Hamid, M.G. Kutty & S.B. Abd. Hamid

Combinatorial Technology and Catalysis Research Centre (COMBICAT)

Level 3, Blok A, Institute of Postgraduate Studies, University Malaya

50603 Kuala Lumpur, Malaysia

 

Received: 11 August 2011 / Accepted: 4 May 2012

 

ABSTRACT

Molybdenum oxides catalysts are extensively used in various selective oxidation reactions. In this work, controlled precipitation method was used to synthesise molybdenum oxides. The effects of various titration parameters on the precipitate growth rate and structure throughout catalyst synthesis were investigated. The titration parameters varied for this study were molybdates (ammonium heptamolybdate) concentration, precipitation agent (HNO3) concentration, precipitating agent rate of addition and temperature of synthesis. X-Ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) were used to characterize the catalysts. This study highlights the significant effects of the titration parameters varied on the supersaturation of the solution therefore yielding precipitate with different morphology. It was observed that the temperature played the major role followed by molybdate concentration in the formation of the bulk catalyst. Supramolecular structure (Mo36O112) was observed at lower temperature (30ºC) and lower molybdate concentration (0.07 M, 0.10 M) while at higher temperature (50ºC) and higher molybdate concentration(0.14 M) hexagonal (h-MoO3) phase structure was formed. Fast rate of addition and high concentration of precipitating agent affected the solution equilibrium leading to unclear inflection point (supersaturation point) at the titration curve.

 

Keywords: Catalyst; molybdenum oxides; precipitation; titration

 

ABSTRAK

Mangkin molibdenum oksida digunakan secara meluas dalam pelbagai tindak balas pengoksidaan terpilih. Kaedah pemendapan yang terkawal telah digunakan dan pelbagai parameter penitratan telah digunakan seperti kepekatan molibdat (ammonia heptamolybdate), kepekatan agen pemendapan (HNO3), kadar penambahan agen pemendapan dan suhu sintesis. Kesan setiap parameter terhadap kadar pertumbuhan dan struktur zarah semasa sintesis mangkin telah dikaji. Pembelauan sinar-X (XRD) dan Mikroskop Pancaran Medan Elektron Imbasan (FESEM) digunakan untuk mengenal pasti ciri-ciri mangkin. Berdasarkan kajian yang telah dibuat, perkara utama yang perlu diberi perhatian adalah kesan setiap parameter penitratan terhadap keterlarutan yang menghasilkan pemendapan pepejal dengan morfologi berbeza. Suhu memainkan peranan paling penting diikuti kepekatan molibdat dalam pembentukan mangkin pukal. Struktur supramolekular (Mo36O112) telah diperhatikan pada suhu rendah (30ºC) dan kepekatan molibdat rendah (0.07 M, 0.10 M) sedangkan pada suhu tinggi (50ºC) dan kepekatan molibdat tinggi (0.14 M) struktur hexagonal (h-MoO3) telah dihasilkan. Kadar penambahan yang cepat dan kepekatan tinggi agen penitratan mempengaruhi keseimbangan larutan dan mengakibatkan titik keterlarutan yang tak jelas.

 

Kata kunci: Mangkin; molibdenum oksida; pemendapan; penitratan

REFERENCES

Abd Hamid, S.B., Othman, D., Abdullah, N., Timpe, O., Knobl, S., Niemeyer, D., Wagner, J., Su, D. & Schogl, R. 2003. Structurally complex molybdenum oxide model catalysts for the selective oxidation of propene. Topics in Catalysis 24(1): 87-95.

Behrens, M., Brennecke, D., Girgsdies, F., Kißner, S., Trunschke, A., Nasrudin, N., Zakaria, S., Idris, N.F., Hamid, S.B.A., Kniep, B., Fischer, R., Busser, W., Muhler, M. & Schlögl, R. 2011. Understanding the complexity of a catalyst synthesis: Co-precipitation of mixed Cu,Zn,Al hydroxycarbonate precursors for Cu/ZnO/Al2O3 catalysts investigated by titration experiments. Applied Catalysis A: General 392(1-2): 93-102.

Bohne, Y., Shevchenko, N., Prokert, F., von Borany, J., Rauschenbach, B. & Möller, W. 2005. In situ characterization of phase formation during high-energy oxygen ion implantation in molybdenum. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 240(1-2): 157-161.

Cavalleri, M., Hermann, K., Guimond, S., Romanyshyn, Y., Kuhlenbeck, H. & Freund, H.J. 2007. X-ray spectroscopic fingerprints of reactive oxygen sites at the MoO3(0 1 0) surface. Catalysis Today 124(1-2): 21-27.

Chang, Z., Song, Z., Liu, G., Rodriguez, J.A. & Hrbek, J. 2002. Synthesis, electronic and chemical properties of MoOx clusters on Au(1 1 1). Surface Science 512(1-2): L353-L360.

Chow, G. & Kurihara, L.K. 2002. Chemical synthesis and processing of nanosructured powders and films. In: Koch, C.C. (ed). Nanostructured materials processing, properties and potential, New York: William Andrew Publishing. pp.3-50.

Cronin, L., Kögerler, P. & Müller, A. 2000. Controlling growth of novel solid-state materials via discrete molybdenum-oxide-based building blocks as synthons. Journal of Solid State Chemistry 152(1): 57-67.

Dieterle, M., Mestl, G., Jäger, J., Uchida, Y., Hibst, H. & Schlögl, R. 2001. Mixed molybdenum oxide based partial oxidation catalyst: 2. Combined X-ray diffraction, electron microscopy and Raman investigation of the phase stability of (MoVW)5O14-type oxides. Journal of Molecular Catalysis A: Chemical 174(1-2): 169-185.

Dillon, C.J., Holles, J.H., Davis, R.J., Labinger, J.A. & Davis, M.E. 2003. Asubstrate-versatile catalyst for the selective oxidation of light alkanes: II. Catalyst characterization. Journal of Catalysis 218(1): 54-66.

Duc, M., Carteret, C., Thomas, F., & Gaboriaud, F. 2008. Temperature effect on the acid-base behaviour of Na-montmorillonite. Journal of Colloid and Interface Science 327(2): 472-476.

Feng, B., Yong, A.K. & An, H. 2007. Effect of various factors on the particle size of calcium carbonate formed in a precipitation process. Materials Science and Engineering: A 445-446(0):170-179.

Haddad, N., Bordes-Richard, E. & Barama, A. 2009. MoOx-based catalysts for the oxidative dehydrogenation (ODH) of ethane to ethylene: Influence of vanadium and phosphorus on physicochemical and catalytic properties. Catalysis Today 142(3-4): 215-219.

Hu, E.L. & Shaw, D.T. 1999. Synthesis and Assembly. In: R.W. Siegel, Hu, E. and Roco, M.C. (ed). Nanostructure Science and Technology A Worldwide Study, pp. 15-34.

Mahajan, S.S., Mujawar, S.H., Shinde, P.S., Inamdar, A.I. & Patil, P.S. 2008. Concentration dependent structural, optical and electrochromic properties of MoO₃ thin films. International Journal of Electrochemical Science 3(8): 953-960

Rodríguez-Paéz, J.E., Caballero, A.C., Villegas, M., Moure, C., Durán, P. & Fernández, J.F. 2001. Controlled precipitation methods:formation mechanism of ZnO nanoparticles. Journal of the European Ceramic Society 21(7): 925-930.

Song, J., Ni, X., Gao, L. & Zheng, H. 2007. Synthesis of metastable h-MoO3 by simple chemical precipitation. Materials Chemistry and Physics 102(2-3): 245-248.

Ueda, W., Sadakane, M. & Ogihara, H. 2008. Nano-structuring of complex metal oxides for catalytic oxidation. Catalysis Today 132(1-4): 2-8.

Ungár, T. 2004. Microstructural parameters from X-ray diffraction peak broadening. Scripta Materialia 51(8): 777-781.

Wagner, J.B., Abd Hamid, S.B., Othman, D., Timpe, O., Knobl, S., Niemeyer, D., Su, D.S. & Schlögl, R. 2004. Nanostructuring of binary molybdenum oxide catalysts for propene oxidation. Journal of Catalysis 225(1): 78-85.

Wang, S., Zhang, Y., Ma, X., Wang, W., Li, X., Zhang, Z. & Qian, Y. 2005. Hydrothermal route to single crystalline α-MoO3 nanobelts and hierarchical structures. Solid State Communications 136(5): 283-287.

Yu, J., Lei, M. & Cheng, B. 2004. Facile preparation of monodispersed calcium carbonate spherical particles via a simple precipitation reaction. Materials Chemistry and Physics 88(1): 1-4.

Yu, S., Sun, C.-J. & Chow, G.-M. 2007. Chemical synthesis of nanostructured particles and films. In: C.K. Carl (ed). Nanostructured Materials (2nd ed): 3-46. Norwich, New York: William Andrew Publishing.

Zhang, R., Ma, J., Li, J., Jiang, Y. & Zheng, M. 2011. Effect of pH, temperature and solvent mole ratio on solubility of disodium 5’-guanylate in water + ethanol system. Fluid Phase Equilibria 303(1): 35-39.

 

*Corresponding author; email: d_devi10@yahoo.com