Influence of nitrogen content on the acid-base properties of aluminophosphate oxynitrides

~

AA PT PA LL E IY DSS C I A: GENERAL

ELSEVIER

Applied Catalysis A: General 137 (1996) 9-23

Influence of nitrogen content on the acid-base properties of aluminophosphate oxynitrides A. Massinon a, J.A. Odriozola b, Ph. Bastians a, R. Conanec c, R. Marchand c, y. Laurent c, p. Grange a, * a Unit~ de Catalyse et Chimie des Mat~riaux Divis~s, Uniuersit~ Catholique de Louvain, Place Croix du Sud 2 / 17, 1348 Louvain-la-Neuve, Belgium b Departamento de Qufrnica lnorg6nica, Uniuersidad de Sevilla, Apdo 874, 41071 Sevilla, Spain c Laboratoire de Chimie des Mat~riaux, URA 1496, CNRS Verres et C~ramiques, Universit~ de Rennes 1, 35042 Rennes Cedex, France

Received 19 June 1995; accepted 6 October 1995

Abstract Novel basic catalysts with high specific surface areas have been synthesized by activation under ammonia of an aluminophosphate oxide precursor. The nitrogen content as well as the acid-base *properties depend on both time and temperature of nitridation. The conversion and reaction rate in Knoevenagel condensation are related to the nitrogen content. Keywords: Acid-base properties; Aluminophosphate oxynitrides; Knoevenagel condensation; Nitrogen

I. Introduction Acid and base are paired concepts; a number of chemical interactions are understood in terms of acid-base interaction. In contrast to solid acid catalysts, which have been extensively studied, solid base catalysts have been much less studied. The discovery of new solid basic compounds would help to replace liquid bases. Indeed, solid catalysts have a number of practical advantages: they are easily separated from the reaction mixture, thus, partially solving environmental problems, they are easily regenerated after reaction and are non-corrosive to the reactor system. Several oxide base catalysts have been proposed in the literature: alkaline earth oxides (MgO, CaO, SrO, BaO), rare earth oxides * Corresponding author. 0926-860X/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0 9 2 6 - 8 6 0 X ( 9 5 ) 0 0 2 5 5 - 3

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A. Massirum et al. / Applied Catalysis A: General 137 (1996) 9-23

( L a 2 0 3 , C e O 2, etc.), alkaline oxides (Li20, Na20, etc.) [1-11]. The number

and basic strength of the sites may be modified on oxides, mainly by promotion with alkali [10,12-16]. Moreover, considering the strong tendency of sodium to donate electrons, a modification with Na allows to prepare superbases [17]. Up to now, most of the reports focused on the study of oxide base catalysts. However, it is known that some non-oxide type catalysts, such as KF-alumina [10], lanthanide amines [18] and nitrides or oxynitrides, may present basic properties. Two kinds of nitrided compounds have been studied: silicon oxynitride [19-22] and molybdenum nitride [23-33]. It has recently been shown that aluminum phosphate oxynitrides contain basic sites on their surface and are able to act as basic catalysts [34-37]. This paper reports bulk and surface characterization of a series of aluminum phosphate oxynitrides (A1PONs) with variable nitrogen content and their catalytic evaluation in a Knoevenagel condensation.

2. Experimental 2.1. Materials

The sol-gel method developed by Kearby [38] was used to prepare amorphous oxide precursors of high specific surface area (A1PO4). At temperature below 273 K, 3 mol propylene oxide per mol aluminum were slowly added to a solution of A1C13 • 6H20 and H 3 P O 4. A P/A1 ratio of 1 was chosen. At the end of the propylene oxide addition, the pH of the solution increased to a value close to 3. After standing overnight at room temperature, the gel obtained was washed with isopropanol, dried and calcined at different temperatures between 923 and 1073 K. Nitridation of the oxide precursor was performed under flowing pure ammonia. Different nitrogen contents were obtained by modifying the time and the temperature of nitridation. At the end of the nitridation process, the samples were cooled down under dry nitrogen flow and stocked in a dessicator [35]. The specific surface areas of the samples were measured by the adsorption of nitrogen at liquid nitrogen temperature by single point BET method ( P / P o = 0.3), after pretreatment (1 h at 423 K), using a Micromeritics Flowsorb II 2300 equipment. 2.2. Nitrogen content o f solids

The principle of the chemical analysis of nitrogen is based on the reaction of the nitride ions N 3- with a strong base which forms ammonia that is then titrated. In the case of refractory oxynitrides, the difficulties of the alkaline attack in solution have been solved by using another procedure [39]. The oxynitrides are treated at 673 K with melted potassium hydroxide under inert atmosphere.

A. Massinon et al./Applied Catalysis A: General 137 (1996) 9-23

11

2.3. Temperature programmed desorption analysis We used the temperature programmed desorption of ammonia to evaluate the acid properties of the samples using a 'dynamic flow fixed bed' type reactor. A 0.2 g sample was evacuated up to 973 K under flowing helium and then cooled down to room temperature. The ammonia adsorption occurs after 15 min at 373 K. The excess of probe molecules is flown out by helium. The temperature programmed desorption experiments are then performed at a heating rate of 10 K / m i n up to 973 K and the desorption of gases is continuously recorded using a thermal conductivity detector (Intersmat IGC 120 ML). The ammonia content was determined by titration with sulfuric acid.

2.4. X-Ray photoelectron spectroscopy analysis The X-ray Photoelectron Spectroscopy analysis of the catalyst samples were performed on a Surface Science Instruments spectrometer (SSX100) with a resolution (fwhm Au 4f7/2) of 1.0 eV. The residual pressure during the analysis remained between 1 and 5 10 - 9 Torr. The X-ray beam was monochromatized AI K a radiation (1486.6 eV). It was focused and lighted on an elliptical surface on which charging effects were avoided through the use of a charge neutralizer (flood gun) adjusted at an energy of 6 eV. As the C ls spectra of these compounds was very complex, the reference of this peak was not accurate and, therefore, the binding energies were referenced to the binding energy of O 1s, considered experimentally to be at 531.8 eV. This value is an average of the O ls binding energy determined by referring to the C ls spectra (284.6 eV) and ranged from 531.7 to 531.9 eV. Quantitative intensity results were obtained using O Is, A1 2p, P 2p and N ls peaks. The intensities were estimated by calculating the integral of each peak after 'S-shaped' background subtraction. Atomic concentration ratios were calculated by correcting the intensity ratios with the theoretical sensitivity factors based on Scoffield cross sections. The catalyst was pressed in a 4 mm diameter stainless steel holder and outgassed at 393 K.

2.5. Catalytic evaluation To test the possibility of basic catalysis, the Knoevenagel condensation was investigated. Four mmol of the two reactants (ethylcyanoacetate or malononitrile and benzaldehyde) were introduced in a stirred reactor at 323 K with toluene as solvent (30 ml), then 0.05 g of catalyst was added. Small liquid samples were regularly withdrawn with a filtering syringe and analyzed by gas chromatography (Intersmat Delsi DI 200) using a capillary column (CPSi18CB-25 m). Care was taken to avoid mass or heat transfer limitations. There is no specific catalyst

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A. Massinon et a l . / Applied Catalysis A: General 137 (1996) 9-23

Table I Composition, global formula and surface area of the samples N content (%)

Surface area (m 2)

Global composition ( m 2 / g )

0 3 8 13 20

250 220 195 205 210

AIPO 4 AIPOa.saN0.28 AIPO3.01 No.66 AIPOz 44N t.02 A1POI.72 Nt.52

pretreatment before the reaction neither for the A1PON series nor for the MgO commercial sample. 3. Results and discussion

3.1. Catalyst characteristics The nitrogen content, as well as the bulk composition and the specific surface area of the solid, are reported in Table 1. The O by N exchange depends on both temperature and time of activation. It must also be stressed that the specific surface of the solids is not strongly influenced by the nitridation of the precursor

[35]. 3.2. Temperature programmed desorption The temperature programmed desorption of ammonia gives a first evaluation of the acid properties of the compounds. This method indicates that the nitrogen content increase is correlated to a total acidity decrease and that the A1PON with the highest nitrogen content presents very few acid centers (Fig. 1). The sample containing 12% atomic nitrogen seems more acid than expected. The maximum

• o n

2 9 % atomic N 19% atomic N 12% atomic N

•

5 % atomic N

2OO

Z 100

0 J00

200

300

400

500

600

700

Temperature (C ° ) Fig. 1. Temperature programmed desorption of NH 3 for the series of catalysts containing different nitrogen contents.

A. Massinon et al./ Applied Catalysis A: General 137 (1996) 9-23

13

1200

1000 E 8oo

40{]

0

t

i

10

20

N content

(atomic

30 %)

Fig. 2. Bulk nitrogen content variation (determined by reaction with a strong base) with the acidity (determined by temperature programmed desorption of NH3).

temperature at which the ammonia desorption occurs is low, meaning that AIPONs contain weak acidic sites. This maximum temperature does not change with the increase in the nitrogen content, which could mean a decrease of the global ionic character of A1PONs. The amount of ammonia desorbed changes as a function of the nitrogen content, but it seems that there are two different trends below and above 15% atomic nitrogen (Fig. 2). The decrease of the acidity is sharper when the bulk atomic nitrogen percentage goes beyond 15%. The temperature programmed desorption of carbon dioxide does not seem suitable for the evaluation of the basicity of aluminophosphate oxynitrides. Indeed, no evolvement of carbon dioxide molecules is detected with the temperature increase. The nature of the aluminophosphate oxynitride basic sites is not yet exactly known, but work in progress in particular through IR spectroscopy is aimed at identifying the sites responsible for the basic behavior of the aluminophosphate oxynitrides. Beside both classical kinds of sites (hydroxyl groups and oxygen ions on the surface), the oxynitrides were presumed to have some basic sites such as N 3-, - N H R or - N H 2 [40]. These sites are created by the nitridation, i.e., the substitution by nitrogen of 0 2- and O - H forms in the acidic aluminophosphate oxide precursor. There is no reason for the different oxygens, which do not adsorb carbon dioxide in the precursor, to change their nature and adsorb this probe molecule in the oxynitride. In our case, hydroxyl groups and oxygen ions on the surface do not have a basic character and only the different species created by nitridation present basic properties. No method used can detect carbonate species which are formed by the reaction between the carbon dioxide and the basic centers. A thermogravimetric analysis was performed on AIPONs to check their thermal stability [39]. At low temperatures, the loss of mass is caused by a loss of adsorbed water. Under inert atmosphere, A1PONs are stable up to a tempera-

14

A. Massinon et a l . / Applied Catalysis A: General 137 (1996) 9-23

2

-2

-4 "<

-6 -8

_~.t.~----~

-IC 0

,

A

L

,

200

400

600

800

1000

(°C)

Temperature

Fig. 3. Thermogravimetric analysis under inert atmosphere up to 1273 K.

ture close to 1273 K (Fig. 3). The weak increase of weight around 1023 K is due to a deviation because of the high temperature.

3.3. X-Ray photoelectron spectroscopy Table 2 presents the binding energies and the full width at medium height (fwhm) values and Table 3 shows the atomic composition and the ratio of the Table 2 Binding energy and fwhm values (eV) N content (wt.-% bulk)

N content (atom.-% bulk)

0

0

3

4.3

8

11.6

13

18.9

20

29.1

AI 2p (eV)

P 2p (eV)

O ls (eV)

N ls (eV)

74.8 (2. I) 74.8 (2.1) 74.9 (2.0) 74.7 (2.0) 74.6 (1.9)

134.1 (2.3) 134.0 (2.3) 134.0 (2.3) 133.9 (2.3) 133.7 (2.2)

531.8 (2.3) 531.8 (2.4) 531.8 (2.3) 531.8 (2.4) 531.8 (2.4)

(-) 399.1 (2.8) 398.9 (2.8) 398.6 (2.9) 398.4 (2.9)

Peaks are referred to the O Is binding energy.

Table 3 Atomic compositions derived from XPS N content (atom.-% bulk)

AI (atom.-%)

P (atom.-%)

O (atom.-%)

N (atom.-% surf.)

0 4.3 11.6 18.9 29.1

13.0 12.8 12.9 13.8 14.1

15.0 14.7 15.1 15.4 15.5

72.0 68.2 59.8 54.2 47.9

4.41 12.2 16.6 22.5

P/AI 1.15 1.15 1.17 1.12 1.1

A. Massinon et al./Applied Catalysis A: General 137 (1996) 9-23

15

2O000

NIs j

/./j~"~ \. ,, \ \ .J)

7

..--.

,.

/'//i- \ \ ..z././'/ ,.,,:./'-'~ \

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~--"

403.3

y/v-

\'. '\ 2O~N ",.. \....

~

401.3

\,

"N

399.3

""

-

397.3

395.3

Binding Energy (eV) 2000 \. =.\

.-/

\\

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e,"

_.._.....''/)/S. i~-~

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./

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j,,,~.~,.-~./"~ r j 78.2

~\

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./"13% N ~.

ll<~

l,l

\.~.,,,

~.~"

76.2 74.2 Binding Energy (eV)

.,--,,,_..,.,-.,~.,,3~, 72.2

70.2

Fig. 4. XPS spectra of N 1s and A1 2p.

four elements present in AIPON solids. In Fig. 4, AI 2p, P 2p, O l s and N ls XPS spectra are shown. The variation of binding energies with the increase in nitrogen content allows to point out that the aluminum phosphate oxynitrides, with nitrogen content closer to 12% atoms, have a behavior distinctive from the other samples. We take these weak variations ( < 0.5 eV) into account, because the same behaviors are found with two different equipments (the other one is a vacuum generator instrument Escalab 210) [41]. In Fig. 5a, the AI 2p binding energy presents a

16

A. Massinon et al. / Applied Catalysis A: General 137 (1996) 9-23

74,9 74,8 e~ ,< ad

74,7 i

74,6

i

134,2~

k~

b

IF

\

399,2[ ~ 399,0[ ~o

~

398,8I 398,6[

0

i

i

10

20

N content

30

(% Atomic)

Fig. 5. Variation o f the binding energies with the nitrogen percentage. binding energy and (c) N l s binding energy.

(a) A1 2p binding

energy,

(b) P 2p

maximum around 12% atoms. A very weak disturbance was detected in the P 2p (Fig. 5b) and the N 1s binding energies variation curve (Fig. 5c), indicating two different behaviors below and above 15% atoms, as in Fig. 2. The progressive and general decreasing trend of the binding energies with the atomic nitrogen percentage was explained by the better nucleophilic character of nitrogen compared to oxygen, which reduced the positive charge around the aluminum and phosphorus atoms. There is a good correlation between both the bulk nitrogen content detection method and the X-ray photoelectron spectroscopy quantification method, as shown in Fig. 6. However, the surface nitrogen percentage seems lower than the bulk nitrogen percentage, which can be explained by the adsorption of a surface layer of water-molecules and the re-oxidation of the surface nitrogen atoms.

A. Massinon et al./ Applied Catalysis A: General 137 (1996) 9-23

17

30

.~

20

E z

o' 0

1o

20

30

N content (atomic %)

Fig. 6. Variation of the nitrogen percentage determined by XPS with the bulk nitrogen percentage determined by reaction with a strong base.

Fig. 7 presents the different ratios in function of the nitrogen percentage. The ratios were calculated in two ways: the bulk ratio is the ratio between the bulk nitrogen content determined from the reaction with melted potassium hydroxide, with an accuracy of 1%, and the other element content calculated from the AIPOxNy formula; the surface ratio is the ratio determined between the surface atomic nitrogen content and the surface atomic content of the other elements, both determined from XPS analysis. Fig. 7a shows the evolution of the N / O ratio; the surface composition evolution is not correlated with the bulk one. Nitridation of the samples allowed a larger bulk than surface N / O increase. Again, two different behaviors can be observed: below 12% nitrogen atoms the bulk ratios are the same as the surface ratios; above 15% nitrogen atoms the values diverge. This divergence can be explained by a better diffusion of nitrogen into the bulk when the nitrogen percentage increases and could be correlated to a change of the structure in these conditions. The evolution of the N / P ratio is studied in Fig. 7b. There is no divergence between the bulk and the surface ratios except for the 12% nitrogen atoms, where a weak deviation can be detected. Fig. 7c presents the evolution of the N / A I ratio. The divergence around 12% nitrogen atoms (and also around 19% nitrogen atoms) is more pronounced than in Fig. 7b. In Fig. 5, also, only the A1 2p variation shows a different behavior with a maximum for the 12 nitrogen atom.-% sample.

3.4. Evaluation of catalytic properties To test the possibility of basic catalysis, the Knoevenagel condensation over aluminophosphate oxynitrides was investigated. This reaction, presented in Eq. (1), is usually catalyzed by amines in which the nitrogen lone pair functions as a weak basic site [42]. C6HsCHO + CNCH2CN ~ C6HsCH=C(CN)2 + H 2 0

(1)

A. Massiru)n et aL / A p p l i e d Catalysis A: General 137 (1996) 9 - 2 3

18

Z

1

Z

0

I

2f 0

i

£o ,

o

o

o

i 0

I 0

I 20

10

30

N content (atomic % ) F i g . 7. Variation of different element ratios with the nitrogen percentage. ( a ) N / O N/AI

ratio, ( b ) N / P ratio, (c)

ratio and (d) P / A I ratio.

The catalysts function by abstraction of a proton from an acidic group (i.e., the methylene in Eq. (1)), which is followed by nucleophilic attack on the carbonyl by the resultant carbanion, re-protonation of oxygen and elimination of water. In the literature, Corma et al. used the same reaction to test the basic character of zeolites, sepiolites and hydrotalcites [43,44]. A Michael-type addition, which requires a greater basic strength, was not further observed. The following four-step reaction pathway in such a Knoevenagel condensation was proposed:

Step 1 K, C H 2 - C N + B-

group

H+ 2re acid

~

NC-~'H-CN K_ 1

+ BH

A. Massinon et al. / Applied Catalysis A: General 137 (1996) 9-23

19

Step 2 H O-

NC_ PX I / ~ k NC - ~:H- CN +

He ~ - - ~ . . ~

K-2

1L OH

"°-.= NCf c-

Step 3 OH

NC.~.~~ ~ NOf C - CH~'z~._.~

~

K3

NC~ _ CHO

K_3

NC~ C -

+ OH"

Step 4 BH+OH-

~ B-+H20

The condensations between benzaldehyde and malononitrile or ethylcyanoacetate are illustrated, in Figs. 8 and 9, respectively. On these figures, a quick increase of conversion in the first 60 min is observed, then the conversion rate decreases. The conversion results are found in Table 4. The comparison between the two condensations gave interesting results [37]. Firstly, the sample containing the highest nitrogen concentration (20%) presented 88% conversion with malononitrile and 57% conversion with ethylcyanoacetate after 300 min. These conversions were compared to commercial 100

i '°

i6o 40

2O G" 0

100

200

300

Time (mia) Fig. 8. Conversion vs. time in Knoevenagel condensation between malononitrile and benzaldehyde. ( n ) %N = 3%, (11) %N = 8%, ( © ) %N = 13% and ( 0 )

%N = 20%.

A. Massinon et a l . / Applied Catalysis A: General 137 (1996) 9-23

20

100

g

8o

60~ 40 20 G100

200 300 Time (rain)

Fig. 9. Conversion vs. time in Knoevenagel condensation between ethylcyanoacetate and benzaldehyde. ( [ ] ) %N = 3%, (11) %N = 8%, ( O ) %N = 13% and ( O ) %N = 20%.

MgO (40 m2/g, in the same condition as the A1PONs (i.e., without pretreatment)) and, in both condensations, the AIPONs conversions were always much higher [37]. Without pretreatment, MgO is not an extremely basic compound but these results show that A1PONs are more active than MgO and such a character could be useful for industrial applications. The basicity of the catalysts explains the higher conversion obtained with the malononitrile: the pK a of ethylcyanoacetate (pK a = 9) was higher than the pK~ of malononitrile ( p K a < 9), i.e., to be transformed in carbanion by the catalyst, ethylcyanoacetate requires sites with a greater basic strength than malononitrile. In general, the condensation extent depends on the nitrogen content of the catalyst. However, the sample containing 8 wt.-% nitrogen did not comply with this general trend. Indeed, the 8 wt.-% nitrogen content seemed more active than the 13 wt.-% one in the two condensations. The surface characterization of the 8 wt.-% nitrogen content by X-ray photoelectron spectroscopy also presents an anomaly and would indicate a variation of the surface nitrogen species, for this

Table 4 Conversion for the Knoevenagel condensation Time (min)

0 30 60 120 180 240 300 1320

Malononitrile conversion (%)/ Catalysts with

Ethylcyanoacetate conversion ( % ) / Catalysts with

3%N

8%N

13%N

20%N

3%N

8%N

13%N

20%N

0 16 16 22 32 41 48

0 32 47 64 74 76 82

0 29 43 50 62 66 70

0 35 61 75 83 86 88

0 10 14 16 15 20 19 34

0 16 24 30 38 43 45 52

0 26 29 26 30 32 38 42

0 40 49 52 56 56 57 71

A. Massinon et al.// Applied Catalysis A: General 137 (1996) 9-23

21

nitrogen content. Preparation of a large number of samples with improved physicochemical characterization may elucidate this behavior [41]. The strength of the basic sites is not yet accurately evaluated, but a basicity range has been determined with different results. Firstly, when the A1PONs are used as catalyst, there is no condensation between diethyl malonate (pK a = 13) and benzaldehyde, and the higher is the pK a of the other reactants (malononitrile or ethylcyanoacetate), the lower is the conversion. Secondly, the Knoevenagel condensation using liquid base catalysts (pyridine, morpholine and pyrrolidine) showed that, in the same experimental conditions, there is no conversion with pyridine (pK a = 5.25) or morpholine (pK a = 8.33), and a comparable reaction rate is found when pyrrolidine (pK a = 11.27) and the AIPONs are used. Thirdly, the same reaction was studied on zeolites, sepiolites and hydrotalcites [43,44]. From their results, Corma et al. demonstrated that, in quite comparable conditions using basic oxide with pK a ---H_ ~< 10.7, the Knoevenagel condensation occurs. They also showed that, when using stronger bases (with pK a = 11.2), other by-products following Michael-type addition or Claisen condensation are produced. All these facts could indicate that the series of oxynitride catalysts prepared with the sol-gel method would have basic sites in the range 10.7 ~< p K a ~H_~< 11.2.

4. Conclusions The sol-gel method allows the preparation of an amorphous aluminum phosphate oxide precursor with a high specific surface area and the nitridation of this precursor allows the variation of the acid-basic properties of the oxynitride, since, the N / O ratio depends on both time and temperature of nitridation. The temperature programmed desorption of ammonia shows that the nitridation linearly decreases the total number of acid sites, but not their strength. XPS analysis pointed out the small decrease of the binding energies with the nitrogen increase, because the nitrogen, which replaces the oxygen by nitridation, is a better electron donor. The sample with 8 wt.-% nitrogen content has a specific behavior which could be related to its different structure. These oxynitrides are able to catalyse the Knoevenagel condensation between ethylcyanoacetate or malononitrile and benzaldehyde. The basic strength of the sites allows the Knoevenagel reaction, but not the Michael-type addition or Claisen condensation. The H_ of the AIPONs is, therefore, assumed to be 10.7 ~
22

A. Massinon et al. / Applied Catalysis A: General 137 (1996) 9-23

- - increase of the catalytic conversion) except for the 12% nitrogen atoms sample.

Acknowledgements We acknowledge the financial support of the R~gion Wallonne, Belgium, for this COST program (No. 2422).

References [1] [2] [3] [4]

H. Pines and W.M. Stalick, Academic Press, New York, 1977. K. Tanabe, Stud. Surf. Sci. Catal., 20 (1985) 1. W.T. Riechle, J. Catal., 94 (1985) 547. S. Malinowski and M. Marezewski, Catalysis: A review of recent literature, Royal Chemical Society, Vol. 8, 1987, p. 107. [5] D. Barthomeuf, G. Coudurier and J.C. V6drine, Mater. Chem. Phys., 18 (1988) 553. [6] H. Hattori, Mater. Chem. Phys., 18 (1988) 533. [7] W. Hblderich, M. Hesse and F. Naiimann, Angew. Chem., Int. Ed. Engl., 27 (1988) 226. [8] K. Tanabe, M. Misono, U. Ono and H. Hattori, Stud. Surf. Sci. Catal., 51 (1989). [9] A. Corma, R.M. Martin-Aranda and F. Sanchez, J. Catal., 126 (1990) 192. [10] H. Hattori, Stud. Surf. Sci. Catal., 78 (1993) 35. [11] A. Corma, V. Fom6s, R.M. Martin-Aranda, H. Garcia and J. Primo, Appl. Catal., 59 (1990) 237. [12] Jae Chang Kim, Hong-Xin Li, Cong-Yan Chen and M.E. Davies, Microporous Mater., 2 (1994) 413. [13] H. Tsuji, F. Yagi and H. Hattori, Chem. Lett., (1991) 1881. [14] H. Tsuji, F. Yagi, H. Hattori and H. Kita, Stud. Surf. Sci. Catal., 75 (1993) 1171. [15] C.B. Dartt and M.E. Davis, Catal. Today, 19 (1994) 151. [16] P.E. Hathaway and M.E. Davis, J. Catal., 116 (1989) 263. [17] G. Suzukamo, M. Fukao and M. Minobe, Chem. Lett., (1987) 585. [18] T. Baba, S. Hikita, R. Koide, Y. Ono, T. Hanada, T. Tanaka and S. Yoshida, J. Chem. Soc., Faraday Trans., 89 (1993) 3177. [19] R.W. Lednor and R. de Ruiter, in J.E. Sheats, C.E. Carraher, C.U. Pittman, M. Zeldin and B. Currel (Editors), Inorganic and Metal-containing Polymeric Materials, Plenum, New York, 1990, p. 187. [20] R.W. Lednor and R. de Ruiter, J. Chem. Soc., Chem. Commun., (1989) 320. [21] R.W. Lednor and R. de Ruiter, J. Chem. Soc., Chem. Commun., (1991) 1625. [22] P.W. Lednor, Catal. Today, 15 (1992) 243. [23] L. Volpe and M. Boudart, J. Solid State Chem., 59 (1985) 332. [24] L. Volpe and M. Boudart, J. Phys. Chem., 90 (1986) 4878. [25] G.S. Ranhotra, A.T. Bell and J.A. Reimer, J. Catal., 108 (1987) 40. [26] J.C. Schlatter, S.T. Oyama, J.E. Metcalf and J.M. Lambert, Ind. Eng. Chem. Res., 27 (1988) 1648. [27] S.T. Oyama and D.J. Sajkowski, Prep. Am. Chem. Soc., Div. Pet. Chem., 35(2) (1990) 233. [28] E.J. Markel and J.W. van Zee, J. Catal., 126 (1990) 643. [29] H. Abe and A.T. Bell, J. Catal., 142 (1993) 430. [30] R.S. Wise and E.J. Markel, J. Catal., 145 (1994) 344. [31] R. Marehand, F. Pors and Y. Laurent, Rev. Int. Hautes Temper. Refract., 23 (1986) 11. [32] G. Choi, R.L. Curl and L.T. Thompson, J. Catal., 146 (1994) 218. [33] C.W. Coiling and L.T. Thompson, J. Catal., 146 (1994) 193. [34] R. Marchand, R. Conanec, Y. Laurent, Ph. Bastians, P. Grange, L.M. Gandia, M. Montes, J. Femandes and J.A. Odriozola, Patent application FR 9401081. [35] P. Grange, Ph. Bastians, R. Conanec, R. Marchand, Y. Laurent, L.M. Gandia, M. Montes, J. Fernandez and J.A. Odriozola, Stud. Surf. Sci. Catal., 91 (1994) 389.

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[36] R. Conanec, R. Marchand, Y. Laurent, Ph. Bastians and P. Grange, Mater. Sci. Forum Vols 1994, 152, 305, Soft Chemistry Routes to New Materials, Nantes, France. [37] P. Grange, Ph. Bastians, R. Conanec, R. Marchand and Y. Laurent, Appl. Catal. A, 114 (1994) L191. [38] K. Kearby, Proc. 2nd Int. Cong. Catal., 1961, p. 2567. [39] R. Marchand, Y. Laurent, J. Guyader, P. L'Haridon and P. Verdier, J. Eur. Ceram. Soc., 8 (1991) 197. [40] P.W. Lednor, Catal. Today, 15 (1992) 243. [41] J.A. Odriozola, A. Massinon, J.J. Benitez, M.A. Centeno, R. Conanec, R. Marchand, Y. Laurent and P. Grange, in preparation. [42] B.P. Mundy and M.G. Ellerd, Name Reactions and Reagents in Organic Synthesis, Wiley, New York, 1988. [43] A. Corma and R.M. Martin-Aranda, J. Catal., 130 (1991) 130. [44] A. Corma, V. Fornes, R.M. Martin-Aranda and F. Rey, J. Catal., 134 (1992) 58.