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Zr(IV) basic carbonate complexes as precursors for new materials: synthesis of the zirconium-surfactant mesophase
Materials Research Bulletin 37 (2002) 1933±1940
Zr(IV) basic carbonate complexes as precursors for new materials: synthesis of the zirconium-surfactant mesophase P. Afanasiev* Institut de Recherches sur la Catalyse, 2 Avenue A. Einstein, 69626 Villeurbanne, CeÂdex, France (Refereed) Received 1 February 2002; accepted 19 July 2002
Abstract Soluble anionic carbonate complexes of Zr(IV) are produced by addition of Zr(IV) salts to the excess of an alkali metal or ammonium carbonate. The solutions are metastable at pH 7±10 and can be used as the precursors for the synthesis of new materials, as illustrated by the example of the surfactant containing mesophase with a wormhole-like structure, prepared by means of reaction with cetyltrimethylammonium bromide. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Oxides; B. Chemical synthesis; D. Nanostructures
1. Introduction Zirconium-based materials are eminently important for different ®elds of advanced technology such as alloys, ceramics, solid-state ionics, inert bioceramics (Al2O3, ZrO2) for medical application, and others. Zirconium oxide, ZrO2, is widely studied as a catalyst and/or catalytic support [1]. Earlier, much work has been done in order to control the morphology and surface properties of this oxide [2±4]. The inorganic precursors used for the preparations of ZrO2-based materials are often the salts where Zr is present in the cationic form (e.g. [Zr4(OH)8(H2O)16]8), such as hydrated oxychloride, ZrOCl28H2O, oxynitrate, ZrO(NO3)2, sulfate Zr(SO4)2, or sometimes acetate [5]. The possibilities of the preparations using these precursors *
Tel.: 33-4-72-44-53-39; fax: 33-4-72-44-53-99. E-mail address: [email protected] (P. Afanasiev).
0025-5408/02/$ ± see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 5 - 5 4 0 8 ( 0 2 ) 0 0 8 8 6 - 3
1934
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
are obviously limited by the chemistry of the corresponding cationic species. To extend the synthetic possibilities, other precursors have been studied, such as carboxylates [6] or alkoxides [7]. Basic Zr(IV) salts have been known for a long time. The solubility of hydrated Zr(IV) hydroxide in a solution of ammonium carbonate was stated by Bertzelius [8], however, the chemical identity of the species in solute was not established. Later, Zaitsev and coworkers [9,10] characterized several carbonate complexes of Zr which are all basic salts with various Zr to carbonate ratios. For some of them, the crystalline structures have been resolved [11,12]. Recently, the structure of [ZrOH(CO3)3]26 guanidinium salt has been determined [13]. However, utilization of the anionic carbonate precursors for the materials preparation has not been reported in the literature. We believe that in using soluble Zr(IV) carbonates, they may be useful alternative precursors for materials synthesis. In this communication, we describe the example of a simple preparation of the new zirconium-surfactant mesophase from the zirconium basic carbonate precursor. 2. Experimental The solution of 0.01 mol of ZrOCl2 or ZrO(NO3)3 in 100 ml of distilled water was added to an excess of 0.1 M solution of Na2CO3 or (NH4)2CO3 at room temperature. The change of pH was monitored with a digital pH-meter. The obtained solution of basic Zr carbonate was immediately used for the synthesis of surfactant containing hybrid solids. To precipitate the surfactant containing mesophases, 0.02 mol of a tetraalkylammonium salt (trimethylcetylpyridinium chloride or cetyltrimethylammonium bromide (CTMAB)) dissolved in 100 ml of water was rapidly added to the solution of basic Zr carbonate. The solids were characterized using powder X-ray diffraction (XRD), FT-IR spectroscopy, and textural measurements. The IR spectra were obtained in air in KBr disks, pressed without grinding. Scanning electron microscopy (SEM) images were obtained on a Hitachi S800 device, at the center of electronic microscopy of Claude Bernard University (Lyon). High resolution transmission electron microscopy (HREM) was done on a JEOL 2010 device, using a 200 kV accelerating voltage. Thermogravimetric analysis with mass spectrometry of evolved gases was applied to study evolution of solids during their linear (5 K min 1) heating in inert atmosphere or in air. The gaseous products evolved upon heating of the samples were studied using a mass-spectrometer Gas Trace A (Fison Instruments) equipped with a quadrupole analyzer (VG analyzer) working in a Faraday mode. The ionization was done by electron impact with an electron energy of 65 eV. 3. Results and discussion It was noticed that the possibility of obtaining of the soluble carbonate complexes in the reaction of ZrOCl2 solution and alkali metal or ammonium carbonate depends
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1935
on the order of addition of reactants and the intensity of stirring. If sodium or ammonium carbonate is added slowly to the excess of ZrOCl2 solution, at its own pH 2, then the pH increases and formation of a white precipitate occurs at ca. pH 4; no redissolution is noticed upon further adding of excess carbonate up to pH 11. By contrast, if Zr salt is added to an excess of carbonate upon vigorous stirring, then soluble species are formed. At the moment of Zr salt addition, transient formation of a white precipitate is observed, but its redissolution occurs instantly, suggesting that the cationic species of the Zr initial salt are ®rst transformed by the reaction with carbonate to the neutral form (precipitation), then to the anionic form (redissolution) which probably correspond to basic zirconium carbonates. Gradual addition of small portions of Zr salt to the excess of Na2CO3 allows the preparation of transparent solutions in the pH range from 7 to 11. The lowest pH limit corresponds to the molar ratio ZrOCl2:Na2CO3 equal to 0.5. Then, addition of more Zr salt leads to the formation of a white precipitate. Similar results have been obtained using ZrOCl2 or ZrO(NO3)2 as starting Zr salts, as well as Na2CO3 or (NH4)2CO3 as carbonate sources. In the pH range from 7 to 11, the solutions of obtained complexes are stable for a rather short time and should, therefore, be used as precursors just after their preparation. Indeed, transparent gels are formed after several days of standing of the solutions at ambient conditions in closed vessels. During this time, ®rst the viscosity of the solutions drastically increases without formation of any gas, then turbidity appears. At the same time, the pH of the solution slowly increases. Probably, polycondensation of zirconium carbonate species occurs, with formation of hydroxide bridges due to the hydrolysis of aqueous carbonate complexes, as represented schematically by the Eq. (1). Zr OH2 Zr OH ! Zr OH Zr H2 O
Fig. 1. IR spectra of hydrated Zr carbonate (a) and (CTA)ZrOOHCO3 sample (b).
(1)
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P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
Slight heating increases the rate of condensation. After 1 h of re¯ux at 373 K, a white amorphous precipitate is formed, which according to the chemical analysis has Zr to CO32 ratio of 1.6, and low amounts of the impurities issued from the reaction mixture (0.6 wt.% of nitrogen and less than 0.1 wt.% of chlorine). This solid shows in the IR spectrum (Fig. 1, spectrum a), two strong and broad lines at 1380 and 1560 cm 1 typical for bidentate carbonate species [14]. Unfortunately, the broad line region between 1600 and 1700 cm 1 is obscured by the strong absorption of water, so more reliable interpretation of IR spectrum is not possible. This solid seems to be a nonstoichiometric zirconium oxohydroxocarbonate. To understand the details of the structure of zirconium species in the basic carbonate solutions and/or in the amorphous precipitates, further study is necessary using EXAFS spectroscopy. The basic carbonate solution obtained as described earlier, might be further used for the synthesis of materials. The new solids syntheses using these precursors might be of several types, but the simplest possibility is evidently to make these complexes to react with some cations in order to precipitate the corresponding salts. For the metal cations, the syntheses of mixed oxides can be envisaged, whereas for the organic cations hybrid organic±inorganic materials might be obtained. Adding freshly prepared basic zirconium carbonate solution at pH 8 to the two-fold molar excess of tetraalkylammonium halides lead to the instant precipitation of white powders. Trimethylcetylpyridinium chloride and CTMAB give precipitates of composition (NR4)0.88ZrO(OH)(CO3)0.91 and (NR4)0.81ZrO(OH)(CO3)0.85, respectively, which suggest that reactive species have the stoichiometry close to [ZrO(OH)CO3] , though their nuclearity is not established. The solids also contain the impurities issued from the reactants (0.8 wt.% of Br and 0.2 wt.% of Cl for CTMAB salt).
Fig. 2. Small angle diffraction of the (CTA)ZrOOHCO3 solid.
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1937
Fig. 3. SEM image of the (CTA)ZrOOHCO3 solid.
The cetyltrimethylammonium-derived solid, (C19H39)0.81ZrO(OH)(CO3)0.85 (designated further as (CTA)ZrOOHCO3), was studied in more detail. In the XRD pattern of this compound, the only intense line is a small angle re¯ection corresponding to the distance of 4.1 nm (Fig. 2). No peaks were observed in the higher angle region. The IR spectrum of (CTA)ZrOOHCO3 registered in air (Fig. 1, spectrum b) consisted of a group of narrow lines at 3002, 2920, 2851, and 1480 cm 1, as well as several small narrow peaks at lower frequencies, all the same as in the spectrum of the initial CTABr (not shown). Two broad bands at 1320 and 1580 cm 1 and a weak line at 1030 cm 1 suggest the presence of bidentate carbonate species. SEM images of (CTA)ZrOOHCO3 solid show the rag-type morphology (Fig. 3) consistent with its poor crystallinity. HREM shows that the sample has a so called wormhole-like structure (Fig. 4), similar to that observed by Blin et al. [15]. The solid consists of fairly monodisperse globular objects with the characteristic size of about 4 nm in agreement with the position of the small angle XRD peak. Thermal decomposition of (CTA)ZrOOHCO3 was studied (Fig. 5). Dehydration occurs at ca. 373 K with a narrow endothermal peak in the TGA curve. The most important part of the weight loss of ca. 40 wt.% is related to an endothermal peak at 520 K which is due to release of organics, since it coincides with peaks of CH3 and CH2 species in the mass spectra. After heating at 773 K in air, the sample loses all carbonate. It still remains XRD amorphous at higher angles but loses mesoscopic ordering as follows from the small angle XRD. It has a BET surface area 178 m2 g 1 and pore volume of 0.4 cm3 g 1 with narrow pore size distribution having a maximum at 2.5 nm (Fig. 5). A nitrogen adsorption±desorption hysteresis loop of the H2 type is observed for the sample calcined at 773 K for 2 h. The H2-type hysteresis loop with a steep desorption and smoothly sloping adsorption curve suggest that near to uniform
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P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
Fig. 4. TEM image of the wormhole-like structure of the (CTA)ZrOOHCO3 solid.
size entrances are present, typical for MCM-like and wormhole mesoporous materials (Fig. 6). It was not our goal in this short paper to optimize the preparation of yet another mesoporous zirconia, but just to illustrate the possibility of application of basic carbonate precursor to the new materials synthesis. Earlier, many studies have been devoted to preparation of mesoporous zirconia. In the previous works, various combinations of precursors and surfactants have been tried. Coprecipitation of
Fig. 5. Mass spectra of gases evolved during heating of (CTA)ZrOHCO3 under a nitrogen ¯ow.
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1939
Fig. 6. Nitrogen adsorption isotherm of the sample obtained after heating (CTA)ZrOHCO3 in air at 773 K for 2 h.
trialkylammonium halide and zirconium oxychloride [16] or isopropoxide [17] mixtures have been used. In the syntheses applying cationic surfactants, often no templating (as in silica mesoporous materials) but just scaffolding by the incorporated surfactant was observed. Using amphoteric [18] or anionic [19] surfactants and oxychloride or propoxide Zr precursors, hexagonal and cubic mesoporous zirconia were obtained. Hydrolysis of zirconium propoxide in the presence of the anionic surfactant was applied to obtain hexagonal mesophases [20]. Here, using a carbonate anionic Zr precursor and a cationic surfactant, we obtain by direct precipitation a new zirconium-surfactant hybrid mesophase. 4. Conclusion We believe that the anionic carbonate complexes of Zr(IV) are the promising alternative precursors for the materials synthesis, which are very simple to prepare, might be applied in the pH range from 7 to 11 and beside zirconium, oxygen, and water, contain only the carbonate moieties easily removable by heating. In this paper, we present an example of this approach, giving an alternative way to the mesoporous zirconia. Work is in progress on the application of these precursors to other preparations such as mixed oxides of Zr(IV). References [1] P.J Moles (Ed.), Zirconium in Catalysis (special issue edition), Catal. Today 20 (2) 1994. [2] G.K. Chuah, S. Jaenicke, S.A. Ceong, K.S. Chan, Appl. Catal. A 145 (1996) 267.
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P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
[3] P. Afanasiev, A. Thiollier, M. Breysse, J.L. Dubois, Top. Catal. 8 (1999) 147. [4] K.T. Jung, A.T. Bell, J. Mol. Catal. A 163 (2000) 27. [5] F.J. Berry, S.J. Skinner, I.M. Bell, R.J.H. Clark, C.B. Ponton, J. Solid State Chem. 145 (1999) 394. [6] G. Pacheco, E. Zhao, A. Garcia, A. Sklyarov, J.J. Fripiat, J. Mater. Chem. 8 (1998) 219. [7] G. Kickelbick, U. Shubert, J. Chem. Soc. Dalton Trans. (1999) 1301. [8] J.J. Bertzelius, OEfvers Acad. FoÈrh. Stockholm (1824) 295. [9] Y.Y. Kharitonov, L.A. Pospelova, L.M. Zaitsev, Russ. J. Inorg. Chem. 12 (1967) 1390. [10] L.A. Pospelova, L.M. Zaitsev, Russ J. Inorg. Chem. 11 (1966) 995. [11] Y.E. Gorbunova, V.G. Kuznetsov, E.S. Kovaleva, Zh. Strukt. Khim. 9 (1968) 918. [12] A. Clear®eld, Inorg. Chim. Acta 4 (1970) 166. [13] S. Morris, M.J. Almond, C.J. Cardin, M.G.B. Drew, D.A. Rice, Y. Zubavichus, Polyhedron 17 (1998) 2301. [14] J. Lamotte, J.C. Lavalley, E. Druet, E. Freund, J. Chem. Soc. Faraday Trans. 79 (1983) 2219. [15] J.L. Blin, R. Flamant, B.L. Su, Int. J. Inorg. Mater. 3 (2001) 959. [16] J.A. Knowles, M.J. Hudson, Chem. Commun. (1995) 2083. [17] V.I. PaÃrvulescu, H. Bonnemann, V. PaÃrvulescu, U. Endruschat, A. Ru®nska, Ch.W. Lehmann, B. Tesche, G. Poncelet, Appl. Catal. A 214 (2001) 273. [18] A. Kim, P. Bruinsma, Y. Chen, L.Q Wang, J. Liu, Chem. Commun. (1997) 161. [19] G. Pacheco, E. Zhao, A. Garcia, A. Sklyarov, J.J Fripiat, Chem. Commun. (1997) 491. [20] D.M. Antonelli, Adv. Mater. 11 (1999) 487.
Zr(IV) basic carbonate complexes as precursors for new materials: synthesis of the zirconium-surfactant mesophase P. Afanasiev* Institut de Recherches sur la Catalyse, 2 Avenue A. Einstein, 69626 Villeurbanne, CeÂdex, France (Refereed) Received 1 February 2002; accepted 19 July 2002
Abstract Soluble anionic carbonate complexes of Zr(IV) are produced by addition of Zr(IV) salts to the excess of an alkali metal or ammonium carbonate. The solutions are metastable at pH 7±10 and can be used as the precursors for the synthesis of new materials, as illustrated by the example of the surfactant containing mesophase with a wormhole-like structure, prepared by means of reaction with cetyltrimethylammonium bromide. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Oxides; B. Chemical synthesis; D. Nanostructures
1. Introduction Zirconium-based materials are eminently important for different ®elds of advanced technology such as alloys, ceramics, solid-state ionics, inert bioceramics (Al2O3, ZrO2) for medical application, and others. Zirconium oxide, ZrO2, is widely studied as a catalyst and/or catalytic support [1]. Earlier, much work has been done in order to control the morphology and surface properties of this oxide [2±4]. The inorganic precursors used for the preparations of ZrO2-based materials are often the salts where Zr is present in the cationic form (e.g. [Zr4(OH)8(H2O)16]8), such as hydrated oxychloride, ZrOCl28H2O, oxynitrate, ZrO(NO3)2, sulfate Zr(SO4)2, or sometimes acetate [5]. The possibilities of the preparations using these precursors *
Tel.: 33-4-72-44-53-39; fax: 33-4-72-44-53-99. E-mail address: [email protected] (P. Afanasiev).
0025-5408/02/$ ± see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 5 - 5 4 0 8 ( 0 2 ) 0 0 8 8 6 - 3
1934
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
are obviously limited by the chemistry of the corresponding cationic species. To extend the synthetic possibilities, other precursors have been studied, such as carboxylates [6] or alkoxides [7]. Basic Zr(IV) salts have been known for a long time. The solubility of hydrated Zr(IV) hydroxide in a solution of ammonium carbonate was stated by Bertzelius [8], however, the chemical identity of the species in solute was not established. Later, Zaitsev and coworkers [9,10] characterized several carbonate complexes of Zr which are all basic salts with various Zr to carbonate ratios. For some of them, the crystalline structures have been resolved [11,12]. Recently, the structure of [ZrOH(CO3)3]26 guanidinium salt has been determined [13]. However, utilization of the anionic carbonate precursors for the materials preparation has not been reported in the literature. We believe that in using soluble Zr(IV) carbonates, they may be useful alternative precursors for materials synthesis. In this communication, we describe the example of a simple preparation of the new zirconium-surfactant mesophase from the zirconium basic carbonate precursor. 2. Experimental The solution of 0.01 mol of ZrOCl2 or ZrO(NO3)3 in 100 ml of distilled water was added to an excess of 0.1 M solution of Na2CO3 or (NH4)2CO3 at room temperature. The change of pH was monitored with a digital pH-meter. The obtained solution of basic Zr carbonate was immediately used for the synthesis of surfactant containing hybrid solids. To precipitate the surfactant containing mesophases, 0.02 mol of a tetraalkylammonium salt (trimethylcetylpyridinium chloride or cetyltrimethylammonium bromide (CTMAB)) dissolved in 100 ml of water was rapidly added to the solution of basic Zr carbonate. The solids were characterized using powder X-ray diffraction (XRD), FT-IR spectroscopy, and textural measurements. The IR spectra were obtained in air in KBr disks, pressed without grinding. Scanning electron microscopy (SEM) images were obtained on a Hitachi S800 device, at the center of electronic microscopy of Claude Bernard University (Lyon). High resolution transmission electron microscopy (HREM) was done on a JEOL 2010 device, using a 200 kV accelerating voltage. Thermogravimetric analysis with mass spectrometry of evolved gases was applied to study evolution of solids during their linear (5 K min 1) heating in inert atmosphere or in air. The gaseous products evolved upon heating of the samples were studied using a mass-spectrometer Gas Trace A (Fison Instruments) equipped with a quadrupole analyzer (VG analyzer) working in a Faraday mode. The ionization was done by electron impact with an electron energy of 65 eV. 3. Results and discussion It was noticed that the possibility of obtaining of the soluble carbonate complexes in the reaction of ZrOCl2 solution and alkali metal or ammonium carbonate depends
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1935
on the order of addition of reactants and the intensity of stirring. If sodium or ammonium carbonate is added slowly to the excess of ZrOCl2 solution, at its own pH 2, then the pH increases and formation of a white precipitate occurs at ca. pH 4; no redissolution is noticed upon further adding of excess carbonate up to pH 11. By contrast, if Zr salt is added to an excess of carbonate upon vigorous stirring, then soluble species are formed. At the moment of Zr salt addition, transient formation of a white precipitate is observed, but its redissolution occurs instantly, suggesting that the cationic species of the Zr initial salt are ®rst transformed by the reaction with carbonate to the neutral form (precipitation), then to the anionic form (redissolution) which probably correspond to basic zirconium carbonates. Gradual addition of small portions of Zr salt to the excess of Na2CO3 allows the preparation of transparent solutions in the pH range from 7 to 11. The lowest pH limit corresponds to the molar ratio ZrOCl2:Na2CO3 equal to 0.5. Then, addition of more Zr salt leads to the formation of a white precipitate. Similar results have been obtained using ZrOCl2 or ZrO(NO3)2 as starting Zr salts, as well as Na2CO3 or (NH4)2CO3 as carbonate sources. In the pH range from 7 to 11, the solutions of obtained complexes are stable for a rather short time and should, therefore, be used as precursors just after their preparation. Indeed, transparent gels are formed after several days of standing of the solutions at ambient conditions in closed vessels. During this time, ®rst the viscosity of the solutions drastically increases without formation of any gas, then turbidity appears. At the same time, the pH of the solution slowly increases. Probably, polycondensation of zirconium carbonate species occurs, with formation of hydroxide bridges due to the hydrolysis of aqueous carbonate complexes, as represented schematically by the Eq. (1). Zr OH2 Zr OH ! Zr OH Zr H2 O
Fig. 1. IR spectra of hydrated Zr carbonate (a) and (CTA)ZrOOHCO3 sample (b).
(1)
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P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
Slight heating increases the rate of condensation. After 1 h of re¯ux at 373 K, a white amorphous precipitate is formed, which according to the chemical analysis has Zr to CO32 ratio of 1.6, and low amounts of the impurities issued from the reaction mixture (0.6 wt.% of nitrogen and less than 0.1 wt.% of chlorine). This solid shows in the IR spectrum (Fig. 1, spectrum a), two strong and broad lines at 1380 and 1560 cm 1 typical for bidentate carbonate species [14]. Unfortunately, the broad line region between 1600 and 1700 cm 1 is obscured by the strong absorption of water, so more reliable interpretation of IR spectrum is not possible. This solid seems to be a nonstoichiometric zirconium oxohydroxocarbonate. To understand the details of the structure of zirconium species in the basic carbonate solutions and/or in the amorphous precipitates, further study is necessary using EXAFS spectroscopy. The basic carbonate solution obtained as described earlier, might be further used for the synthesis of materials. The new solids syntheses using these precursors might be of several types, but the simplest possibility is evidently to make these complexes to react with some cations in order to precipitate the corresponding salts. For the metal cations, the syntheses of mixed oxides can be envisaged, whereas for the organic cations hybrid organic±inorganic materials might be obtained. Adding freshly prepared basic zirconium carbonate solution at pH 8 to the two-fold molar excess of tetraalkylammonium halides lead to the instant precipitation of white powders. Trimethylcetylpyridinium chloride and CTMAB give precipitates of composition (NR4)0.88ZrO(OH)(CO3)0.91 and (NR4)0.81ZrO(OH)(CO3)0.85, respectively, which suggest that reactive species have the stoichiometry close to [ZrO(OH)CO3] , though their nuclearity is not established. The solids also contain the impurities issued from the reactants (0.8 wt.% of Br and 0.2 wt.% of Cl for CTMAB salt).
Fig. 2. Small angle diffraction of the (CTA)ZrOOHCO3 solid.
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1937
Fig. 3. SEM image of the (CTA)ZrOOHCO3 solid.
The cetyltrimethylammonium-derived solid, (C19H39)0.81ZrO(OH)(CO3)0.85 (designated further as (CTA)ZrOOHCO3), was studied in more detail. In the XRD pattern of this compound, the only intense line is a small angle re¯ection corresponding to the distance of 4.1 nm (Fig. 2). No peaks were observed in the higher angle region. The IR spectrum of (CTA)ZrOOHCO3 registered in air (Fig. 1, spectrum b) consisted of a group of narrow lines at 3002, 2920, 2851, and 1480 cm 1, as well as several small narrow peaks at lower frequencies, all the same as in the spectrum of the initial CTABr (not shown). Two broad bands at 1320 and 1580 cm 1 and a weak line at 1030 cm 1 suggest the presence of bidentate carbonate species. SEM images of (CTA)ZrOOHCO3 solid show the rag-type morphology (Fig. 3) consistent with its poor crystallinity. HREM shows that the sample has a so called wormhole-like structure (Fig. 4), similar to that observed by Blin et al. [15]. The solid consists of fairly monodisperse globular objects with the characteristic size of about 4 nm in agreement with the position of the small angle XRD peak. Thermal decomposition of (CTA)ZrOOHCO3 was studied (Fig. 5). Dehydration occurs at ca. 373 K with a narrow endothermal peak in the TGA curve. The most important part of the weight loss of ca. 40 wt.% is related to an endothermal peak at 520 K which is due to release of organics, since it coincides with peaks of CH3 and CH2 species in the mass spectra. After heating at 773 K in air, the sample loses all carbonate. It still remains XRD amorphous at higher angles but loses mesoscopic ordering as follows from the small angle XRD. It has a BET surface area 178 m2 g 1 and pore volume of 0.4 cm3 g 1 with narrow pore size distribution having a maximum at 2.5 nm (Fig. 5). A nitrogen adsorption±desorption hysteresis loop of the H2 type is observed for the sample calcined at 773 K for 2 h. The H2-type hysteresis loop with a steep desorption and smoothly sloping adsorption curve suggest that near to uniform
1938
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
Fig. 4. TEM image of the wormhole-like structure of the (CTA)ZrOOHCO3 solid.
size entrances are present, typical for MCM-like and wormhole mesoporous materials (Fig. 6). It was not our goal in this short paper to optimize the preparation of yet another mesoporous zirconia, but just to illustrate the possibility of application of basic carbonate precursor to the new materials synthesis. Earlier, many studies have been devoted to preparation of mesoporous zirconia. In the previous works, various combinations of precursors and surfactants have been tried. Coprecipitation of
Fig. 5. Mass spectra of gases evolved during heating of (CTA)ZrOHCO3 under a nitrogen ¯ow.
P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
1939
Fig. 6. Nitrogen adsorption isotherm of the sample obtained after heating (CTA)ZrOHCO3 in air at 773 K for 2 h.
trialkylammonium halide and zirconium oxychloride [16] or isopropoxide [17] mixtures have been used. In the syntheses applying cationic surfactants, often no templating (as in silica mesoporous materials) but just scaffolding by the incorporated surfactant was observed. Using amphoteric [18] or anionic [19] surfactants and oxychloride or propoxide Zr precursors, hexagonal and cubic mesoporous zirconia were obtained. Hydrolysis of zirconium propoxide in the presence of the anionic surfactant was applied to obtain hexagonal mesophases [20]. Here, using a carbonate anionic Zr precursor and a cationic surfactant, we obtain by direct precipitation a new zirconium-surfactant hybrid mesophase. 4. Conclusion We believe that the anionic carbonate complexes of Zr(IV) are the promising alternative precursors for the materials synthesis, which are very simple to prepare, might be applied in the pH range from 7 to 11 and beside zirconium, oxygen, and water, contain only the carbonate moieties easily removable by heating. In this paper, we present an example of this approach, giving an alternative way to the mesoporous zirconia. Work is in progress on the application of these precursors to other preparations such as mixed oxides of Zr(IV). References [1] P.J Moles (Ed.), Zirconium in Catalysis (special issue edition), Catal. Today 20 (2) 1994. [2] G.K. Chuah, S. Jaenicke, S.A. Ceong, K.S. Chan, Appl. Catal. A 145 (1996) 267.
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P. Afanasiev / Materials Research Bulletin 37 (2002) 1933±1940
[3] P. Afanasiev, A. Thiollier, M. Breysse, J.L. Dubois, Top. Catal. 8 (1999) 147. [4] K.T. Jung, A.T. Bell, J. Mol. Catal. A 163 (2000) 27. [5] F.J. Berry, S.J. Skinner, I.M. Bell, R.J.H. Clark, C.B. Ponton, J. Solid State Chem. 145 (1999) 394. [6] G. Pacheco, E. Zhao, A. Garcia, A. Sklyarov, J.J. Fripiat, J. Mater. Chem. 8 (1998) 219. [7] G. Kickelbick, U. Shubert, J. Chem. Soc. Dalton Trans. (1999) 1301. [8] J.J. Bertzelius, OEfvers Acad. FoÈrh. Stockholm (1824) 295. [9] Y.Y. Kharitonov, L.A. Pospelova, L.M. Zaitsev, Russ. J. Inorg. Chem. 12 (1967) 1390. [10] L.A. Pospelova, L.M. Zaitsev, Russ J. Inorg. Chem. 11 (1966) 995. [11] Y.E. Gorbunova, V.G. Kuznetsov, E.S. Kovaleva, Zh. Strukt. Khim. 9 (1968) 918. [12] A. Clear®eld, Inorg. Chim. Acta 4 (1970) 166. [13] S. Morris, M.J. Almond, C.J. Cardin, M.G.B. Drew, D.A. Rice, Y. Zubavichus, Polyhedron 17 (1998) 2301. [14] J. Lamotte, J.C. Lavalley, E. Druet, E. Freund, J. Chem. Soc. Faraday Trans. 79 (1983) 2219. [15] J.L. Blin, R. Flamant, B.L. Su, Int. J. Inorg. Mater. 3 (2001) 959. [16] J.A. Knowles, M.J. Hudson, Chem. Commun. (1995) 2083. [17] V.I. PaÃrvulescu, H. Bonnemann, V. PaÃrvulescu, U. Endruschat, A. Ru®nska, Ch.W. Lehmann, B. Tesche, G. Poncelet, Appl. Catal. A 214 (2001) 273. [18] A. Kim, P. Bruinsma, Y. Chen, L.Q Wang, J. Liu, Chem. Commun. (1997) 161. [19] G. Pacheco, E. Zhao, A. Garcia, A. Sklyarov, J.J Fripiat, Chem. Commun. (1997) 491. [20] D.M. Antonelli, Adv. Mater. 11 (1999) 487.