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ELSEVIER Microporous Materials 10 (1997) 283-286MICROPORODSMATERIALS

A 28-year-old synthesis ofmicelle-templated mesoporous silicaFrancesco Di Renzo *, Helene Cambon, Roger Dutartre

Laboratoire de Materiaux Catalytiques et Catalyse en Chimie Organique. UMR 5618 CNRS, ENSCM,8 rue de i'Ecole Normale, 34296 Montpellier, Cedex 5. France

Received 11 March 1997; accepted 17 March 1997

AbstractA procedure for the preparation of low-density silica described in a patent filed in 1969 [V. Chiola, J .E. Ritsko,

CD. Vanderpool, US Patent 3556725, 1971] leads to the formation of solids having all the properties of MCM-41,the ordered mesoporous silica disclosed in 1991 [J.S. Beck, CT.-W. Chu, I.D. Johnson, CT. Kresge, M.E. Leonowicz.W.J. Roth. J.W. Vartuli, WO Patent 91/11390, 1 9 9 1 ] . ~ ' 1997 Elsevier Science B.V.Keywords: Cetyltrimethylammonium; MCM-41; Mesopores; Silica; Synthesis

M41 mesoporous silicas present pores of uniform size obtained by the self-assembly of a solublesilicate and surfactant micelles. The disclosure oftheir propert ies by the scientists of Mobil [3,4]fullfilled a long-term expectation of researchers incatalysis and adsorption, and extended to themesopore range the applications of molecular sieving, formerly limited to microporous zeolites [5].The importance of this breakthrough is evidencedby the wave of research activities on the selfassembly of inorganic materials and micelles whichit initiated [6-10].Recent literature reports indicate that MCM-4Lthe hexagonal member of the micelle-templatedmesoporous silica group, can be synthesized in awide range of experimental conditions. Interactions between silica and cationic surfactants havebeen studied intensively in recent decades [II],and we wondered why no MCM-41 forerunner Corresponding author.0927-6513/97/$17.00 1997 Elsevier Science BY All rights reserved.PI I S0927-6513(97)00028-X

had been formed in early experiments. In severalearly studies, the strong adsorption of surfactantmicelles on the surface of silica particles wasapplied to control of the flocculation of colloidalsilica [12]. If the surfactant is added to a solublesilicate instead of being adsorbed on the surfaceof pre-formed grains, MCM-41 is the more likelycondensation product. We looked for a descriptionof such a process in the early literature, and foundthat lIer, in his classical book on silica [13], reportson a patent of 1971 of V. Chiola et al. [I ] assignedto Sylvania Electric Products Inc., in which tetraethylorthosilicate is hydrolyzed and condensed inthe presence of a cationic surfactant to form "Iowbulk density silica". The paten t does not reporton the characterization of the precipitation productbeyond its bulk density, and we prepared a solidaccording to the specifications of the patent inorder to evaluate its properties.In a reproduction of example I of the patent ofChiola et al., 8.3 g of cetyltrimethylammonium

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284 F. Di Ren::o et al. ! Microporous Materials 10 ( 1997) 283-286

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Relative pressure, P/PoFig. 1. Powder X-ray diffraction (a), transmission electron microscopy (b), and nitrogen adsorption isotherm (c) of the micelletemplated mesoporous silica prepared according to the patent of Chiola et a1. [I].

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F Di Ren::o et at. / Microporous Materials 10 ( 1997) 283-286 285bromide (Aldrich) was dissolved in 42 g of ammonia solution (28%). After addition of 9 g of tetraethylorthosilicate (Aldrich), the mixture wasstirred at room temperature for 90 min beforebeing heated at 70"C. The solid product wascharacterized by powder X-ray diffraction andN2 adsorption at 77 K after calcination, and bytransmission electron microscopy (TEM). TheX-ray powder diffraction pattern of the solid. aftercalcination at 550C in an air flow, is reported inFig. 1(a). The solid features a main peak at 39.3 Aand two weaker signals which can be indexed ona hexagonal cell with a=45.3 A. The presence ofseveral well-defined peaks is considered as a testfor long-range ordering of the pores in theMCM-41 material. This result is supported by theTEM observation of the precipitation product(Fig. 1(b )), which reveals a neat honeycombpattern. The N 2 adsorption isotherm at 77 K onthe calcined solid is reported in Fig. 1(c). Thereversible type-IV isotherm features a sharp stepat PIpO = 0.32, indicating a narrow distribution ofmesopores centered around a diameter of 32 A.The measured mesopore volume is 0.61 cm3 g-l,and the t-plot reveals no micropore volume. Allthese data indicate that the material preparedaccording to the recipe of Chiola et al. [1] featuresthe characteristic properties of well-orderedMCM-41 hexagonal mesoporous silica [2].The low-density material of Chiola et al. is notonly a forerunner of MCM-41 silica, but also ofsurfactant-templated materials of different composition [14]. The 1971 patent relates the application of the synthesis method to the manufacture

of doped zinc orthosilicate phosphors.The history of micelle-templated mesoporoussilica follows a pattern which is not rare in thehistory of discoveries. Columbus cannot be disavowed as the discoverer of America, although LeifEricsson preceded him by several centuries. Thelatter had a priority on the discovery, but he failedto realize, and surely did not claim in widespreadreports, the nature and the implications of hisfinding. As a consequence, the independentresearch of the second discoverer was needed tospread the knowledge of a new world properly. Asimilar pattern has often been observed in materials science [15], a recent example being represented

by the history of the VPI-5 aluminophosphatemolecular sieve [16]. The presence of forerunners,unknown outside a restricted field of application,by no means decreases the value of the characterization and modelling which make the resultsavailable to a wider community and fertile forfurther research. Nevertheless, such a situation canseriously affect a research community characterized by solid connections between fundamentaland applied science. Do we have to rejoice at theprospect of t reasures hidden in old literature, orcomplain about the risk that claims for prioritycan be impaired?

AcknowledgmentThe authors thank D. Plee for useful discussions,

and F. Fajula for his constant support .

References[I ] V. Chiola, J.E. Ritsko, e.D. Vanderpool , US Patent

3556725, 1971.[2] J.S. Beck, e.T.-W. Chu. I.D. Johnson, e.T. Kresge. M.E.Leonowicz, W.J. Roth, J.W. Vartuli, WO Patent91/11390,1991.[3] e.T. Kresge, M.E. Leonowicz, W.J. Roth. J.e. Vartuli,J.S. Beck, Nature 359 (1992) 710.[4] J.S. Beck. J.e. Vartuli, W.J. Roth. M.E. Leonowiz, e.T.Kresge, K.D. Schmit t, e.T.-W. Chu. D.H. Olson. E.W.Sheppard. S.B. McCullen. J.B. Higgins, J.L. Schlenker,J. Am. Chern. Soc. 114 (1992) 10834.[5] D.E.W. Vaughan, in: P.A. Jacobs, R.A. van Santen (Eds.l.Zeolites: Facts. Figures, Future. Studies in Surface Scienceand Catalysis. vol. 49, par t A. Elsevier, Amsterdam,

1989, p. 95.[6] S. Inagaki, Y. Fukushima, K. Kuroda, J. Chern. Soc.,Chern. Commun. (1993) 680.[7] e.-Y. Chen, S.L. Burkett, H.-X. Li, M.E. Davis.Microporous Mater. 2 (1993) 27.[8] e.A. Fyfe, G. Fu. J. Am. Chern. Soc. 117 (\995\ 9709.[9] A. Firouzi. D. Kumar, L.M. Bull. T. Besier. P. Sieger. Q.Huo, S.A. Walker, JA . Zasadzinski, e. Glinka. J. Nicol,D. Margolese, G.D. Stucky, B.F. Chmelka, Science 267

(\ 995) 1138.[10] G.D. Stucky. Q. Huo, A. Firouzi, B.F. Chmelka, S.Schacht. I.G. Voigt-Martin, F. Schuth. in: H . Chon, S.-K.Ihm. V.S. Uh (Eds.), Progress in Zeolite and MicroporousMaterials, Studies in Surface Science and Catalysis.vol. lOS, part A. Elsevier. Amsterdam, 1997. p. 3.[II] B.H. Bijsterbosch. J. Colloid Interface Sci. 51 (1975) 212.

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286 F Di Renzo et al. ! Microporous Materials 10 ( 1997) 283-286[12] R.K. Iter, US Patent 2663650, 1953.[13] R.K. IIer, The Chemistry of Silica, Wiley. New York

1971, p. 562.[14] Q. Huo, D.1. Margolese, U. Ciesla, P. Feng, T.E. Gier. P.

Sieger, R. Leon. P.M. Petroff, F. Schuth, G.D. Stucky,Nature 368 (1994) 317.

[15] A.I. Ihde, The Development of Modern Chemistry, Dover,New York, 1964.

[16] I.-P. Gilson, in: E.G. Derouane, F. Lemos, C. Naccache,F.R. Ribeiro, (Eds.), Zeolite Microporous Solids:Synthesis. Structure, and Reactivity, Kluwer, Dordrecht,1992. p. 19.