FR2835251A1 - PROCESS FOR THE PREPARATION OF AROMATIC ALDEHYDE - Google Patents

Abstract

The invention relates to a method for preparing an aromatic aldehyde by oxidizing a hydroxymethyl compound. According to the inventive method for preparing an aromatic aldehyde by oxidizing a corresponding hydromethyl compound, said hydromethyl compound is reacted with formaldehyde or a formaldehyde generator in the presence of an effective quantity of a microporous solid of type zeolite beta , containing silicon, tin, and/or titanium, and optionally aluminum. The invention particularly relates to the preparation of 3-methoxy-4-hydroxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde.

Description

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 PROCESS FOR THE PREPARATION OF AROMATIC ALDEHYDE

 The present invention relates to a process for preparing an aromatic aldehyde by oxidation of a hydroxymethyl compound.

 The invention relates more particularly to the preparation of 3-methoxy-4-hydroxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde, respectively referred to as "vanillin" and "ethylamine".

 There are numerous methods in the literature for accessing aromatic aldehydes and more particularly for their preparation by oxidation of a hydroxyalkyl compound.

 In EP-A-0 934 244, the preparation of vanillin or 3-methoxy-4-hydroxybenzaldehyde is described in particular in a process consisting in reacting formaldehyde and guaiacol in the presence of sodium hydroxide, which leads to a mixture comprising o-hydroxymethylguaiacol (OMG) and p-hydroxymethylguaiacol (PMG), then oxidizing said mixture with oxygen in the presence of a palladium catalyst and a bismuth c-catalyst and then removing in the products of oxidation containing the carboxylic group located in the ortho position, thus obtaining vanillin with a very good reaction yield.

 In the process described in EP-A-0 934244 which uses homogeneous catalysis, there is selective oxidation of the hydroxymethyl and formyl group located in the ortho position of a hydroxyl group, in a carboxylic group and oxidation of the hydroxymethyl group located in the position para, at most in formyl group.

 The Applicant proposes a new process for obtaining an aromatic aldehyde, according to a totally different process, using a different oxidizing system and a heterogeneous catalyst of a completely different nature.

 More specifically, the subject of the present invention is a process for the preparation of an aromatic aldehyde by oxidation of a corresponding hydroxymethyl compound, characterized in that the said hydroxymethyl compound is reacted with formaldehyde or a formaldehyde generator, in the presence of an effective amount of a micro-porous solid of the zeolite type ss comprising silicon and tin or titanium or aluminum or mixtures thereof.

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 It has surprisingly been found that vanillin can be obtained by reacting p-hydroxymethylguaiacol (also called vanillyl alcohol) with formaldehyde in the presence of the aforementioned microporous molecular sieve while one would have expected the formaldehyde reacts on the free position in ortho of the hydroxyl group and also leads to the hydroxymethylation of this position: the formaldehyde having in the present invention an oxidizing role.

 In the following description of the present invention, the term "aromatic aldehyde" means an aromatic compound of which a hydrogen atom directly linked to the aromatic ring is replaced by a formyl group and by "aromatic compound", the conventional concept of aromaticity as defined in the literature, in particular by Jerry MARCH, Advanced Organic Chemistry, 4th Edition, John Wiley and Sons, 1992, pp. 40 and following.

 By hydroxymethylated aromatic compound is meant an aromatic compound of which a hydrogen atom directly bonded to the aromatic ring is replaced by a hydroxymethyl group.

 The substrate involved in the process of the invention is an aromatic compound bearing at least one hydroxymethyl group, hereinafter hydroxymethylated compound.

 The aromatic ring carries at least one hydroxymethyl group but may also carry one or more other substituents.

Generally, by more than one substituent, less than four substituents are defined per aromatic ring.

 Any substituent may be present to the extent that it does not interfere with the reaction of the invention. Examples of substituents are given below but the list is in no way limiting.

composés hydroxyméthylés répondant à la formule suivante (1) :

Thus, the method of the invention is well adapted to apply to

hydroxymethyl compounds corresponding to the following formula (1):

dans ladite formule (1) : - x est un nombre entier compris entre 0 et 4, - R, identiques ou différents, représente :

in said formula (1): - x is an integer between 0 and 4, - R, identical or different, represents:

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propyle, isopropyle, butyle, isobutyle, sec-butyle, tert-butyle, . un groupe alkoxy linéaire ou ramifié ayant de 1 à 6 atomes de carbone, de préférence de 1 à 4 atomes de carbone tel que les groupes méthoxy, éthoxy, propoxy, isopropoxy, butoxy ou un groupe phénoxy, . un groupe de formule :

dans lesdites formules, R1 représente un lien valentiel ou un groupe hydrocarboné divalent, linéaire ou ramifié, saturé ou insaturé, ayant de 1 à
6 atomes de carbone tel que, par exemple, méthylène, éthylène, propylène, isopropylène, isopropylidène ; les groupes R2 identiques ou différents représentent un atome d'hydrogène ou un groupe alkyle linéaire ou ramifié ayant de 1 à 6 atomes de carbone ; X symbolise un atome d'halogène, de préférence un atome de chlore, de brome ou de fluor. . a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl, ethyl,

propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, a linear or branched alkoxy group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy or a phenoxy group, a group of formula:

in said formulas, R1 represents a valency bond or a linear or branched divalent hydrocarbon group, saturated or unsaturated, having from 1 to
6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene; the groups R 2 which are identical or different represent a hydrogen atom or a linear or branched alkyl group having from 1 to 6 carbon atoms; X symbolizes a halogen atom, preferably a chlorine, bromine or fluorine atom.

 - two groups R placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a benzene ring, - two groups R placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a ring having from 5 to 7 atoms, comprising a heteroatom.

 When x is greater than or equal to 2, two R groups and the two successive atoms of the aromatic ring may be bonded together by an alkylene, alkenylene or alkenylidene group having 2 to 4 carbon atoms to form a saturated, unsaturated or aromatic heterocycle having from 5 to 7 carbon atoms. One or more carbon atoms may be replaced by another heteroatom, preferably oxygen. Thus, the R groups may represent a methylenedioxy or ethylenedioxy group.

 In formula (1), R preferably represents one of the following groups or functions: a hydrogen atom,

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 . a hydroxyl group, a linear or branched alkyl group having from 1 to 4 carbon atoms, a linear or branched alkoxy group having from 1 to 4 carbon atoms, a methylenedioxy or ethylenedioxy group.

 Even more preferentially, the hydroxymethylated aromatic compounds of formula (1) in which the R groups, which are identical or different, are chosen are a hydrogen atom, a hydroxyl group, a methyl or ethyl group, a methoxy or ethoxy group.

 In formula (1), x is preferably 1 or 2.

dans lesdites formules, R représente un groupe alkyle ou alkoxy ayant de 1 à 4 atomes de carbone, de préférence un groupe méthyle ou éthyle. The present invention is particularly applicable to compounds used alone or as a mixture, corresponding to the following formulas:

in said formulas, R represents an alkyl or alkoxy group having 1 to 4 carbon atoms, preferably a methyl or ethyl group.

 As preferred examples of substrates that may be used in the process of the invention, mention may be made of, inter alia: o-hydroxymethylphenol, p-hydroxymethylphenol, o-hydroxymethylguaiacol, p-hydroxymethylphenol, hydroxymethylguaiacol; o-hydroxymethylguetol; p-hydroxymethylguetol.

It is possible to use formaldehyde or any formaldehyde generator such as, for example, trioxane or paraformaldehyde used in the form of linear polyformaldehydes of indifferent degree of polymerization, preferably having a number of units (CH 2 O) of between 8 and 100. reasons
Formaldehyde can be used in the form of an aqueous solution whose concentration is not critical. It can vary between 15 and 50% by weight: commercial solutions with a concentration of about 20 to 40% by weight are preferably used.

 The amount of formaldehyde expressed in moles of formaldehyde per mole of hydroxymethyl compound can vary within wide limits. The formaldehyde / hydroxymethyl compound molar ratio may vary between 5 and 90% and preferably between 15 and 75%.

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 A characteristic of the process of the invention is to use a catalyst which is a micro-porous molecular sieve of zeolite type ss in which part of the silicon atoms are substituted with tin and / or titanium and / or aluminum.

dans ladite formule (11) : - w est un nombre compris entre 0 et 0,2, de préférence entre 0 et 0,1, - y est un nombre compris entre 0 et 0, 1, - z est un nombre compris entre 0 et 0,1, - y et z ne peuvent être simultanément égaux à 0. The catalyst involved in the process of the invention has an empirical formula after calcination which is as follows:

in said formula (11): - w is a number between 0 and 0.2, preferably between 0 and 0.1, - y is a number between 0 and 0, 1, - z is a number between 0 and 0,1, - y and z can not simultaneously be 0.

 The zeolitic catalysts are prepared according to a hydrothermal crystallization process of a reaction medium comprising a source of tin and / or titanium, a source of silicon, a structuring agent, optionally a metal M, an OH-or F-mobilizing agent. possibly hydrogen peroxide and water.

 Many sources of the +4 oxidation state silicon element can be used. By way of example, mention may be made of silicas in the form of hydrogels, aerogels, xerogels, colloidal suspensions, silicas resulting from precipitation from solutions of soluble silicates or hydrolysis of silicic esters. as Si (OCH3) 4, Si (OC2H5) 4. It is also possible to use hydrolyzable tetravalent silicon compounds such as silicon halides or the like.

 The silicon source is preferably selected from alkylsilicates, with tetraethylsilicate being the most preferred.

préférence l'o-titanate de tétraéthyle ou l'o-titanate de tétrabutyle, les sels solubles de titane tels TiOS04, TiOCL, (NH4) TiOO) . Among the sources of titanium, mention may be made, for example, of crystallized or amorphous titanium oxides and hydroxides, tetravalent titanium compounds that can be hydrolysed, such as halides (TiCL), organic titanium derivatives, such as for example, o-titanates of alkyl,

preferably tetraethyl o-titanate or tetrabutyl o-titanate, soluble titanium salts such as TiOSO4, TiOCL, (NH4) TiOO).

 Among the sources of tin, mention may in particular be made of tin halides, preferably SnC 4, tin alkoxides, tin metal, alkali or alkaline earth metal stannates, alkyltin compounds.

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 As structuring agents, mention may be made of tetraalkylammonium ions such as tetraethylammonium ions; dialkylbenzylammonium ions such as dimethylbenzylammonium ion; bis-piperidunium ions such as the 4,4'-trimethylene-bis (N-benzyl-N-methylpiperidinium) ion. These ions can be provided in the form of compounds of hydroxide or halide type, preferably chloride or bromide. Mention may also be made of aza-polycyclic compounds such as 1,4-diazabicyclo-2,2,2-octane.

 A first preferred variant of the process of the invention consists in using a micro-porous molecular sieve of zeolite type with tin.

 Another variant of the process of the invention is to use a micro-porous molecular sieve of zeolite type with Ti or Ti + Al.

dans ladite formule (IIA), y est compris entre 0,001 et 0,1, de préférence entre 0,001 et 0,05. A particularly preferred catalyst for carrying out the process of the invention is a micro-porous zeolite-type molecular sieve with an empirical formula, after calcination which is as follows:

in said formula (IIA), y is between 0.001 and 0.1, preferably between 0.001 and 0.05.

 Said catalyst is known and is described in particular in EP-A 1 010 667.

 It is obtained by a process which consists in a hydrothermal process which involves the formation of a reaction mixture by mixing the desired sources of tin, silicon, optionally titanium, optionally aluminum, an organic structuring agent , water, optionally hydrogen peroxide and a fluoride source, in any order to give the desired mixture. It is also necessary that the pH of the mixture be in the range of about 7.5 to 9.5. If necessary, the pH of the mixture can be adjusted by addition of HF and / or NH4F. Hydrogen peroxide can be added to form a complex with titanium and keep it in solution.

 The reaction mixture is heated at a temperature of about 90 ° C to about 200 ° C, and preferably about 120 ° C to about 180 ° C, for a period of about 2 days to 50 days, and preferably about 10 days to about 25 days, in a sealed reactor under autogenous pressure. After the allotted time, the mixture is filtered to isolate the solid product which is washed with deionized water and air dried.

 In order to promote crystallization, it is preferred to add zeolite crystals as seeds in the reaction mixture. These crystals may be added in the form of a dry solid, a suspension in a suitable liquid, for example water, an alcohol or a pre-organized gel, that is to say a gel containing

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 germs. A preferred zeolite seed germ is a seed prepared according to the teachings of Spanish Patent Application No. P9501552.

 The isolated molecular sieve is characterized by having an X-ray diffraction pattern of a zeolite p.

 In order to activate the zeolite, that is active for adsorption or for catalytic reactions, it is necessary to remove the structuring agent and the fluoride. This is generally accomplished by calcining the molecular sieve at a temperature of about 300 ° C to about 1000 ° C for a time sufficient to essentially remove all the structuring agent and fluoride, which takes from about 1 to about 10 hours. After calcination, the solid retains its crystallinity.

 The zeolite involved in the process of the invention is a microporous solid. The size of its pores generally varies between 5 and 7 Å, and preferably between 5.6 and 6.6 Å.

dans ladite formule (IIB), z est compris entre 0,001 et 0,1. Another type of catalyst that is suitable for the invention is a microporous molecular sieve of zeolite type with titanium having an empirical formula, after calcination which is as follows:

in said formula (IIB), z is between 0.001 and 0.1.

 A process for the preparation of such a catalyst is described by T. Blasco et al [J. Phys. Chem. B, 102, 75, 1998].

dans ladite formule (IIC) : - west un nombre supérieur à 0, compris entre 0 et 0,2, de préférence entre 0,001 et 0,1, - z est un nombre compris entre 0,001 et 0,1. It is also possible to use a titanium catalyst comprising silicon, aluminum which can be represented by the empirical formula, after calcination which is the following:

in said formula (IIC): a number greater than 0, between 0 and 0.2, preferably between 0.001 and 0.1, z is a number between 0.001 and 0.1.

 For the preparation of said catalyst, reference may be made to the work of T.

Blasco et al., J. Am. Chem. Soc., 115, (1993), p. 11806-11813.

 According to the process of the invention, during the oxidation reaction, a zeolite type catalyst as described above is used.

 The amount of this catalyst to be used, expressed by weight of catalyst relative to the hydroxymethyl compound can vary between 10 and 75%, preferably between 20 and 50%.

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 A variant of the process of the invention consists in conducting the oxidation reaction in an organic solvent.

 The organic solvent is chosen so that it is inert under the reaction conditions.

l'éthylèneglycol (ou glyme), le diméthyléther du diéthylèneglycol (ou diglyme) ; l'oxyde de phényle ; le dioxane, le tétrahydrofurane (THF) ; des esters tels que le benzoate de méthyle, le téréphtalate de méthyle, l'adipate de méthyle, le phtalate de dibutyl ; des nitriles aliphatiques ou aromatiques comme l'acétonitrile, le propionitril, le benzonitrile ; les carboxamides linéaires ou cycliques comme le N, N-diméthylacétamide (DMAC), le diméthylformamide (DMF), le diéthylformamide ou la 1-méthyl-2-pyrrolidinone (NMP). Thus, it is possible to use aliphatic, cycloaliphatic or aromatic ether-oxides and, more particularly, dipropyl oxide, diisopropyl oxide, dibutyl ether, methyl tert-butyl ether, dimethyl ether and the like.

ethylene glycol (or glyme), dimethyl ether diethylene glycol (or diglyme); phenyl ether; dioxane, tetrahydrofuran (THF); esters such as methyl benzoate, methyl terephthalate, methyl adipate, dibutyl phthalate; aliphatic or aromatic nitriles such as acetonitrile, propionitril, benzonitrile; linear or cyclic carboxamides such as N, N-dimethylacetamide (DMAC), dimethylformamide (DMF), diethylformamide or 1-methyl-2-pyrrolidinone (NMP).

 The amount of organic solvent is determined such that the weight concentration of the hydroxymethyl compound in the liquid phase is usually between 2% and 40%, preferably between 5% and 20%.

 According to the invention, the hydroxymethyl compound and the formaldehyde are reacted hot in the presence of the microporous molecular sieve.

 The oxidation temperature is preferably chosen, in a temperature range from 40.degree. C. to 120.degree. C., preferably between 600.degree. C. and 100.degree.

 It is usually done at atmospheric pressure, but one can work at slightly lower or higher pressures.

 According to a preferred variant of the process of the invention, the process of the invention is carried out under a controlled atmosphere of inert gases. It is possible to establish an atmosphere of rare gases, preferably argon, but it is more economical to use nitrogen.

 From a practical point of view, the method according to the invention is simple to implement.

 The formaldehyde and the hydroxymethyl compound are charged and the zeolite catalyst is added and heated.

 When working batchwise, the reaction time is generally between 0.5 and 15 hours.

 According to another embodiment, the hydroxymethyl compound can be dissolved in a suitable solvent, for example acetonitrile, and then introduced continuously during the course of the reaction.

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 It is also possible to carry out the process of the invention in a continuous mode in a tubular reactor comprising the solid catalyst arranged in a fixed bed.

 The reagents can be introduced separately or in a mixture into the reactor. They can also be introduced in a solvent as mentioned above.

 The residence time of the flow of material on the catalyst bed varies, for example, between 15 minutes and 10 hours, and preferably between 30 minutes and 5 hours.

 The aromatic aldehyde obtained is recovered in a conventional manner. If necessary, the organic solvent is removed and then the aldehyde is removed by extraction with a suitable solvent, for example methyl isobutyl ketone.

 The following examples illustrate the invention without limiting it.

 In the examples, the conversion ratio (TT) corresponds to the ratio between the number of moles of substrate transformed and the number of moles of substrate involved.

 The yield (RR) corresponds to the ratio between the number of moles of product formed and the number of moles of substrate engaged.

EXAMPLES: Example 1
This example illustrates the synthesis of a stannosilicate with a ss zeolite structure.

 30 g of tetraethyl orthosilicate (TEOS) and 32.99 g of tetraethylammonium hydroxide (TEAOH, 35% by weight) are added to a container.

 After 90 minutes, a solution of 0.43 g of SnCl 4, 6H 2 O (98%) in 2.75 g of water is added and the mixture is stirred until the methanol formed by the hydrolysis of TEOS evaporated.

 To the clear solution, 3.2 g of HF (48%) is added and a thick paste is obtained.

 Finally, a suspension of 0.36 g of dealuminized zeolite seeds (Si / Al ratio 1000) in 1.75 g of water is added.

The final composition of the gel is described by the following formula:
SiO2; 0.27 (TEA) 20; 0.008 SnO2; 0.54 HF; 7.5 H20
This paste is loaded into teflon jacketed stainless steel autoclaves and heated to 1400C and allowed to react for 11 days with stirring.

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 After 11 days, the product is recovered by filtration and revealed by X-ray diffraction analysis to have the structure of the ss zeolite and have a crystallinity of about 95%.

 A chemical analysis further shows that the product contains 1.6% by weight of tin.

 The product is calcined at 580 ° C. for 3 hours and it retains its crystallinity.

Example 2
This example illustrates the synthesis of a titanosilicate with a ss zeolite structure.

 40 g of TEOS and 2.54 g of titanium tetraethylate are added to a container and 45.38 g of TEAOH (35%) and 6.40 g of hydrogen peroxide (35%) are added to this solution. .

 The mixture is stirred until the ethanol formed by the hydrolysis of TEOS has evaporated.

 To this solution is added 4.50 g of HF (48%) and a thick paste is obtained.

 Finally, a suspension of 0.48 g of dealuminized zeolite seeds in 2.3 g of water is added.

The final composition of the gel is described by the following formula: SiO 2; 0.28 (TEA) 20; 0.0035 TiO2; 0.56 HF; 0.34 H 2 O 2; 7.5 H20
This paste is loaded in stainless steel autoclaves with a Teflon jacket and heated at 140 ° C. for 7 days with stirring.

 After this time, the product is recovered by filtration to give a product which contains silicon and titanium in the framework and has the X-ray diffraction pattern of zeolite p.

 The crystallinity of the product measured from its X-ray diffraction spectrum is about 100%.

 Part of this sample is analyzed and shows that it contains 3.2% by weight of titanium.

 After calcination at 580 ° C., the titanosilicate molecular sieve retains its crystallinity.

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Example 3
This example illustrates the synthesis of a stannotitanosilicate with a ss zeolite structure.

 45 g of TEOS and 0.98 g of titanium tetraethylate are added to a container and 50.47 g of TEAOH (35%) and 7.12 g of hydrogen peroxide (35%) are added to this solution. .

 Then, a solution of 0.64% SnCl 4, 5H 2 O (98%) in 2.5% water was added.

 The mixture is stirred until the ethanol formed by the hydrolysis of TEOS has evaporated.

 To this solution, 5% HF (48%) is added and a thick paste is obtained.

 Finally, a suspension of 0.94 g of dealuminized zeolite seeds in water was added.

H20
On charge cette pâte dans des autoclaves en acier inoxydable à chemise en teflon et l'on la chauffe à 1400C pendant 18 jours sous agitation. The final composition of the gel is described by the following formula:
SiO2; 0.28 (TEA) 20; 0.02 TiO2; 0.008 SnO2; 0.56 HF; 0.34 H 2 O 2; 7.5

H20
This paste is loaded in stainless steel autoclaves with Teflon liner and heated at 1400C for 18 days with stirring.

 After this time, the product is recovered by filtration to give a product which contains silicon, titanium and tin in the framework and has the X-ray diffraction pattern of the zeolite ss.

 The crystallinity of the product measured from its X-ray diffraction spectrum is about 95%.

 Part of this sample is analyzed and shows that it contains 0.6% by weight of titanium and 1.5% by weight of tin.

 After calcination at 580 ° C., the stannotitanosilicate molecular sieve retains its crystallinity.

Example 4
This example illustrates the synthesis of a stannoaluminosilicate with a ss zeolite structure.

In a vessel, 40% TEOS and 35.75% TEAOH (35%) are added.
Then, a solution of 0.55% SnC14.5H2O (98%) in 2.5% water is then added.

 After 60 minutes, a solution of 0.21 g of metallic aluminum in 10 g of TEAOH is added and the mixture is stirred until the ethanol formed by the hydrolysis of the TEOS has evaporated.

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 To this solution is added 4.53 g of HF (48%) and a thick paste is obtained.

 Finally, a suspension of 0.47 g of dealuminized zeolite seeds in 2.5 g of water is added.

The final composition of the gel is described by the following formula:
SiO2; 0.28 (TEA) 20; 0.008 SnO2; 0.02 Al 2 O 3; 0.57 HF; 7.5 H20
This paste is loaded in stainless steel autoclaves with Teflon liner and heated at 140 ° C. for 10 days with stirring.

 After this time, the product is recovered by filtration and has the X-ray diffraction pattern of the ss zeolite and a crystallinity of about 100%.

 A chemical analysis of the material shows that the product contains 1.9 wt.% Tin and has an Si / Al ratio of 27.

 The product is calcined at 5800C for 3 hours and its crystallinity is about 90%.

Example 5
This example illustrates the synthesis of a titanoaluminosilicate with a zeolite structure.

 30 g of TEOS and 0.82 g of titanium tetraethylate are added to a container and 28.15 g of TEAOH (35%) and 4.73 g of hydrogen peroxide (35%) are added to this solution. .

 After 60 minutes, a solution of 0.039 g of metallic aluminum in 6 g of water is added and the mixture is stirred until the ethanol formed by the hydrolysis of the TEOS has evaporated.

Si02 ; 0, 28 (TEA) 20 ; 0, 025 Ti02 ; 0, 005 A1203 ; 0, 34 H202 ; 6, 5 H20
On charge le gel dans des autoclaves en acier inoxydable à chemise en teflon et l'on la chauffe à 1400C pendant 4 jours sous agitation. The final composition of the gel is described by the following formula:

SiO2; 0, 28 (TEA) 20; 0.025 TiO 2; 0, 005 A1203; 0.34 H2O2; 6, 5 H20
The gel is loaded in stainless steel autoclaves with Teflon liner and heated at 1400C for 4 days with stirring.

 After this time, the product is recovered by centrifugation to give a product which contains silicon, titanium and aluminum in the framework and has the X-ray diffraction pattern of the zeolite ss.

 The crystallinity of the product measured from its X-ray diffraction spectrum is about 90%.

 Part of this sample is analyzed and shows that it contains 2.4% by weight of titanium and has an Si / Al ratio of 70.

 After calcination at 580 ° C., the titanoaluminosilicate molecular sieve retains its structure.

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Example 6
In this example, the catalytic activities of the samples prepared in Examples 1,2, 3,4 and 5 are compared with the selective oxidation of vanillic alcohol to vanillin using aqueous formaldehyde as the oxidizing agent.

 Thus, 50 mg of vanillic alcohol and 2 g of aqueous formaldehyde (24.9% by weight solution) are homogenized with stirring, and the mixture is heated at temperatures of between 80 and 100 ° C., and take a small aliquot part (time zero).

 Then, the reaction mixture is added all at once in a 2 ml glass microreactor (fully closed) equipped with a magnetic stirrer and immersed in a thermostatic bath which contains only the catalyst (15 to 20 mg).

 After 6 hours, the micro-reactor is removed from the thermostated bath (final time).

 The sample is filtered and 20 mg of the final mixture is placed in 0.85 g of acetonitrile.

 The solution obtained is analyzed by high performance liquid chromatography, high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) and the reaction products are identified by gas chromatography (GC) coupled with mass spectrometry. and HPLC-MS, and they are compared with available standard compounds.

 The TT and RR of several catalysts after six hours of reaction are shown in Table (1):

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Table (1)

<Tb>
<tb> Catalyst <SEP> TT <SEP> RR%
<tb>%
<tb> Type <SEP> 6h <SEP> Vanillin <SEP> 5-methyl- <SEP> Bis- <SEP> Others
<tb> hydroxy-aryl
<tb> vanillin
<tb> Sn-ss <SEP> 73.5 <SEP> 71.8 <SEP> 0 <SEP> 1.7 <SEP> 0
<tb> (1, <SEP> 6 <SEP>% <SEP> Sn)
<tb> Ti-ss <SEP> 71.9 <SEP> 60.3 <SEP> 7.3 <SEP> 1.3 <SEP> 3.0
<tb> (3.2 <SEP>% <SEP> Ti)
<tb> Ti-Sn-p <SEP> 66.9 <SEP> 44.3 <SEP> 7.1 <SEP> 7.1 <SEP> 8.4
<tb> (1, <SEP> 5 <SEP>% <SEP> Sn / 0, <SEP> 6 <SEP>% <SEP> Ti)
<tb> Sn-A <SEP>! -p <SEP> 65.8 <SEP> 40.0 <SEP> 1.2 <SEP> 3.8 <SEP> 20.8
<tb> (1, <SEP> 9 <SEP>% <SEP> Sn / Si / AI <SEP> = <SEP> 27)
<tb> Ti-Al-ss <SEP> 45.6 <SEP> 25.1 <SEP> 11.5 <SEP> 3.8 <SEP> 5.2
<tb> (2,4 <SEP>% <SEP> Ti / Si / Al <SEP> = <SEP> 70)
<Tb>
Example 7
This example illustrates the catalytic activity of the Sn-ss molecular sieve prepared in Example 1 with respect to the oxidation of vanillin alcohol to vanillin using aqueous formaldehyde as an oxidizing agent and acetonitrile as the solvent. .

 Thus, 50 mg of vanillyl alcohol, 2 g of aqueous formaldehyde (24.9% by weight solution) and 1 g of acetonitrile as a solvent with stirring are homogenized and the mixture is heated to temperatures of between 80.degree. 100oC, and a small aliquot (time zero) is taken.

 Then, the reaction mixture is added all at once in a 5 ml glass microreactor (fully closed) equipped with a magnetic stirrer and immersed in a thermostatic bath which contains only the catalyst (15 to 20 mg).

 After 6 hours, the micro-reactor is removed from the thermostated bath (final time).

 The sample is filtered and 20 mg of the final mixture is placed in 0.5 g of acetonitrile.

 The resulting solution is analyzed by HPLC, HPLC-MS and the reaction products are identified by GC-MS and HPLC-MS, and compared with available standard compounds.

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The TT and RR obtained for the catalyst sample after six hours of reaction are shown in Table ()): Table (li)

<Tb>
<tb> Catalyst <SEP> TT <SEP> RR%
<tb>% <SEP> Vanillin <SEP> 5-methyl- <SEP> Bisaryles <SEP> Others
<tb> hydroxyvanillin
<tb> Sn-ss <SEP> 3, <SEP> 5 <SEP> 1.8 <SEP> 0.3 <SEP> 1.0 <SEP> 0.4
<Tb>

Exemple 8 Cet exemple illustre l'activité catalytique du tamis moléculaire Sn-ss préparé dans l'exemple 1 vis-à-vis de l'oxydation de l'alcool vanillique en vanilline en utilisant du formaldéhyde aqueux comme agent oxydant et avec une lente addition du substrat dissous dans de l'acétonitrile.

Example 8 This example illustrates the catalytic activity of the Sn-ss molecular sieve prepared in Example 1 with respect to the oxidation of vanillic alcohol to vanillin using aqueous formaldehyde as an oxidizing agent and with slow addition substrate dissolved in acetonitrile.

 Thus, 2 g of aqueous formaldehyde (24.9% by weight solution) is introduced into a 5 ml (fully closed) glass micro-reactor equipped with a magnetic stirrer and immersed in a thermostatic bath which contains only the catalyst (15 to 20 mg), and is heated to temperatures between 80 and 100oC.

 Then, a well homogenized solution of 50 mg of vanillyl alcohol in 1 g of acetonitrile in the reaction system was slowly added using a micro-syringe infusion pump (addition rate = 150 μl / hr).

 After 6 hours, the micro-reactor is removed from the thermostated bath (final time). The sample is filtered and 20 mg of the final mixture is placed in 0.5 g of acetonitrile.

 The resulting solution is analyzed by HPLC, HPLC-MS and the reaction products are identified by GC-MS and HPLC-MS, and compared with available standard compounds.

heures de réaction sont présentés dans le tableau (lit) : Tableau (lit)

The TT and RR obtained for the catalyst sample after six

reaction times are shown in the table (reads): Table (reads)

<Tb>
<tb> Catalyst <SEP> TT% <SEP> RR%
<tb> Vanillin <SEP> 5-methyl- <SEP> Bisaryles <SEP> Others
<tb> hydroxyvanillin
<tb> Sn-ss <SEP> 20.8 <SEP> 17, <SEP> 7 <SEP> 0.3 <SEP> 2.4 <SEP> 0, <SEP> 4
<Tb>

Claims (16)

 Claims 1-Process for the preparation of an aromatic aldehyde by oxidation of a corresponding hydroxymethyl compound, characterized in that the said hydroxymethyl compound is reacted with formaldehyde or a formaldehyde generator, in the presence of an effective amount of a micro-porous solid of the zeolite ss type comprising silicon and tin or titanium or aluminum or mixtures thereof.  in said formulas, R1 represents a valency bond or a linear or branched, saturated or unsaturated, divalent hydrocarbon group having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene; the identical R2 groups or

 in said formula (1): - x is an integer between 0 and 4, - R, identical or different, represents:. a hydrogen atom, a linear or branched alkyl group having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, a linear or branched alkoxy group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy or a phenoxy group, a group of formula:

 2 - Process according to claim 1 characterized in that the hydroxymethyl compound has the following formula: <Desc / Clms Page number 17>  different represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms; X symbolizes a halogen atom, preferably a chlorine, bromine or fluorine atom, - two R groups placed on two vicinal carbon atoms may together form and with the carbon atoms which carry them a benzene ring, two R groups placed on two vicinal carbon atoms may form together with the carbon atoms which carry them a ring having from 5 to 7 atoms, comprising a heteroatom.

 3 - Process according to one of claims 1 and 2 characterized in that the hydroxymethyl compound corresponds to the formula (1) wherein R represents one of the following groups or functions:. a hydrogen atom, a hydroxyl group, a linear or branched alkyl group having from 1 to 4 carbon atoms, a linear or branched alkoxy group having from 1 to 4 carbon atoms, a methylenedioxy or ethylenedioxy group. 4-Process according to one of claims 1 to 3 characterized in that the hydroxymethyl compound corresponds to the formula (1) wherein the same or different R groups are a hydrogen atom, a hydroxyl group, a methyl group or ethyl, a methoxy or ethoxy group.  5 - Process according to one of claims 1 to 4 characterized in that the hydroxymethyl compound corresponds to the formula (1) wherein x is equal to 1 or 2.  in said formulas, R represents an alkyl or alkoxy group having 1 to 4 carbon atoms, preferably a methyl or ethyl group.

 6 - Process according to one of claims 1 to 5 characterized in that the hydroxymethyl compound meets one of the formulas: <Desc / Clms Page number 18>  7 - Process according to one of claims 1 to 6 characterized in that the hydroxymethyl compound is selected from: - o-hydroxyméthyiphenot, - p-hydroxymethylphenol, -o-hydroxyméthylgaïacol, - p-hydroxyméthylgaïacol, o-hydroxymethylguetol; p-hydroxymethylguetol.  8 - Process according to claim 1 characterized in that it implements formaldehyde or any formaldehyde generator preferably, trioxane or paraformaldehyde used in the form of linear polyformaldehydes of indifferent degree of polymerization, preferably having a number of units (CH20) between 8 and 100 units.  9 - Process according to claim 8 characterized in that the molar molar ratio formaldehyde / hydroxymethyl compound varies between 5 and 90% and preferably between 15 and 75%.

 10 - Process according to claim 1 characterized in that the catalyst corresponds to the empirical formula, after calcination which is the following:  in said formula (N): - w is a number between 0 and 0.2, preferably between 0 and 0.1, - y is a number between 0 and 0, 1, - z is a number between 0 and 0,1, - y and z can not simultaneously be 0.

 in said formula (IIA), y is between 0.001 and 0.1, preferably between 0.001 and 0.05.

 11 - Process according to claim 1 characterized in that the catalyst is a zeolite Sn p corresponding to the empirical formula, after calcination which is the following:  12 - Process according to claim 1 characterized in that the catalyst is a zeolite Ti ss corresponding to the empirical formula, after calcination which is the following: <Desc / Clms Page number 19>  in said formula (lib), z is between 0.001 and 0.1.

13-Process according to claim 1 characterized in that the catalyst is a zeolite Ti + AI ss corresponding to the empirical formula, after calcination which is the following:

 in said formula (IIC): a number greater than 0, between 0 and 0, 2, preferably between 0.001 and 0.1, z is a number between 0.001 and 0.1.

 14 - Method according to one of claims 1 to 14 characterized in that the amount of this catalyst to implement, expressed by weight of catalyst relative to the hydroxymethyl compound varies between 10 and 75%, preferably between 20 and 50%.  15 - Process according to one of claims 1 to 15 characterized in that the oxidation temperature is chosen in a temperature range from 400C to 120 C, preferably between 600C and 100 C.  16 - Process according to one of claims 1 to 16, characterized in that the aromatic aldehyde obtained is vanillin or ethyl vanillin.