FR2693457A1 - Phenolic cpds. hydroxylation for phenol(s) and phenolic ether(s) hydroxylation - by hydrogen peroxide with mineral acidic catalyst and in ketone cpd., for esp. phenol to form hydroquinone and pyrocatechol, for improved yields of di:phenol(s) and easy sepn. of acid catalyst - Google Patents

Abstract

A new hydroxylation of phenolic cpds. of the formula (I); R and Ro = H, 1-4C alkyl-cyclohexyl or phenyl - by H2O2 in an acid catalyst comprises effecting the reaction in a ketonic cpd. and a suitable amt. of a solid mineral catalyst with acidic properties. The mineral acid catalyst is pref. of SiO2-Al2O3, SiO2-Ga2O3, SiO2-B2O3; acid or bridged-clays; natural or synthetic zeolites; phosphates of B-Al and Ga; lamellar phosphates of tetravalent metals, i.e. alpha-M(HPO4)2pH2O (M = Ti, Ge, Zr or Sn; p less than Z) lamellar phosphonates (Zr) and acidic oxides (sulphated oxides of Ti, Zr or Fe). The natural clays, from which acidic clays are derived, are pref. based on the T.O.T. structure (smectites, vermiculite and micas): the smectites include montmorillonites Si4(Al2-yMgy)O10(OH)2M+y; beidellites (Si4-xAlx)Al2O10)CH)2M+x; hectorites Si4(Mg3-yLiy)O10(OH)2M+y; stevensites Si4(Mg3-y(O10(OH)2M+2y; saponites (Si4-xAlx)Mg3O10(OH)2M+x. The commercial clays (acidic or not) are treated with an aq. acid soln. Bridged clays are pref. from a smectite (a synthetic beidellite or a montmorillonite. This comprises treatment with a hydroxide of Al, Ni, Co, V, Mo, Rh, Fe, Cu, Ru, Cr, La, Ce, Ti, Ba, Ga, Zr, Nb, Ta or Si (Al(CH)3 is used). The natural zeolite may be a chabazite, clinofitilite, erionite, mordenite, philipsite or offretite. Synthetic zeolites are pref. of ZSM-5, zeolite Y, ferrierite, zeolite X (faujasite), zeolite L, mordenite, zeolite ZSM-11, mazzite and offretite. The zeolite used is esp. acidified zeolite US-Y or a ZSM-5. The cpds. corresp. to the formula Ra-CO-X-Rb (II). Ra and Rb = 1-30C hydrocarbyl, or together form a divalent radical (opt. substd. by halogen atom(s) or gp(s). stable in the reaction conditions). More pref., Ra and Rb = 1-8C alkyl, (Ra = 1-6C alkyl and Rb = phenyl). X = a single bond, -CO-, -CHOH- or -(R)n- (1-4C alkylene and n = 1-16). The ketonic cpd. is pref. a pentanone, acetophenone, or n-valero phenone. The cpd. (I) is pref. phenol, anisole, ortho, para or meta cresol, 4-tertbutyl, 2-methoxy and 4-methoxy phenol: specifically (I) is phenol. The amt. of catalyst w.r.t. phenolic cpd. (I) is 0.1-20% (0.5-10%). The amt. of ketonic cpd. (II) is at least 1 x 10 power (-3) per mole of H2O2, (1 x 10 power (-3) - 10) esp. 0.05-1.0 mole. USE/ADVANTAGE - More esp. the hydroxylation is used to hydroxylate phenols and phenolic ethers, esp. phenol to form hydroquinone and pyrocatechol. The hydroxylation gives improved yields of diphenols and enables easy sepn. of the acid catalyst from the reaction medium at the end of the reaction.

Description

HYDROXYLATION PROCESS OF PHENOLIC COMPOUNDS
The subject of the present invention is a process for the hydroxylation of phenolic compounds and more particularly a process for the hydroxylation of phenols and phenol ethers by hydrogen peroxide.

 At present, one is looking for a method of hydroxylation of phenol in hydroquinone and pyrocatechine which does not have the disadvantages of a homogeneous catalysis while leading to satisfactory diphenol yields.

 One of the major industrial processes for the hydroxylation of phenols and phenol ethers is described in patent FR-A 2 071 464. It uses acid homogeneous catalysis.

 The method comprises performing hydroxylation with hydrogen peroxide in the presence of a strong acid. Among these strong acids, sulfuric acid, para-toluenesulfonic acid, perchloric acid are the most used.

 The hydroxylation of the phenol carried out under the conditions described leads to a mixture of hydroquinone and pyrocatechol, with predominance of it since the hydroquinone / pyrocatechol ratio most often varies between 0.3 and 0.7.

 Although this method is very interesting, it has the disadvantage of using a homogeneous catalysis. It follows a problem to get rid of the acid catalyst at the end of the reaction. To eliminate the acid, one can [lnd. Eng.

Chem. Prod. Res. Dev. 15, ne3 (1976) l separate the acid by aqueous washing and then treat the reaction medium with a mixture of water and isopropyl ether. The acid remains in the aqueous phase and the phenol and diphenols formed are extracted in isopropyl ether. It is then necessary to distil off the isopropyl ether and then to carry out the distillation of phenol and diphenols.

 As regards the hydroxylation using a heterogeneous acid catalyst, its major disadvantage is that it often leads to yields of diphenols which are not satisfactory.

 The object of the present invention is to solve the dual problem of providing a process for increasing the amount of diphenols formed and easily separating the acid catalyst from the reaction medium at the end of the reaction.

dans laquelle R et Row identiques ou différents représentent un atome d'hydrogène, un radical alkyle ayant de 1 à 4 atomes de carbone, un radical cyclohexyle, un radical phényle, au moyen de peroxyde d'hydrogène, en présence d'un catalyseur acide, ledit procédé étant caractérisé par le fait que la réaction est conduite en présence d'un composé cétonique et d'une quantité efficace d'un catalyseur minéral solide à propriétés acides.More specifically, the subject of the present invention is a process for the hydroxylation of phenolic compounds of general formula (I):

in which R and Row identical or different represent a hydrogen atom, an alkyl radical having 1 to 4 carbon atoms, a cyclohexyl radical, a phenyl radical, by means of hydrogen peroxide, in the presence of an acid catalyst said process being characterized in that the reaction is conducted in the presence of a ketone compound and an effective amount of a solid mineral catalyst with acidic properties.

 It has now been found that the presence of a ketone compound in a heterogeneous acidic catalyst system makes it possible to increase the yields significantly.

 A first feature of the process of the invention lies in the choice of the catalyst which is a mineral solid with acidic properties.

 In order to determine whether a mineral solid has acidic properties, it may be subjected to the test developed by the company RHONE-POULENC described in APPLIED CATALYSIS, 78, p.213-225 (1981).

 The principle of the test consists of dehydrating the 2-methyl-3-butyne-ol by contact with the solid catalyst to be tested, at a temperature of 180.degree.

 If the catalyst has acidic properties, the products of the reaction are 3-methyl-3-buten-1-yne-1 and prenal.

 If the catalyst has basic properties, the products of the reaction are acetone and acetylene.

 From a practical point of view, the reaction is carried out under a nitrogen atmosphere and the 2-methyl-3-butyne-2-ol is sent with a flow rate of 4.0 hours per 0.4 g of catalyst.

 The catalyst that is suitable for the invention must therefore, when it is subjected to this test, lead to the formation of 3-methyl-3-buten-1-yne-1 and prenal.

 As examples of catalysts with acidic properties, mention may be made, in particular, of combinations of metal and metalloid oxides such as: silica-alumina, silica-Ga 2 O 3, silica-B 2 O 3.

 Another type of acidic mineral catalysts that are quite suitable for carrying out the process of the invention are acid clays.

 To prepare the acidic clays, preference is given to natural clays having a structure called "TOT" or tetrahedron-octahedron-tetrahedron.

 The clays TOT are in the form of elementary sheets comprising two layers of tetrahedrons of oxygen atoms in which are included the silicon atoms separated by a layer of octahedra of oxygen atoms in which is included the metal M of type MO4 (OH) 2 or M is a divalent or trivalent cation.

 When all the tetrahedra are occupied by Si4 + ions, the electric neutrality of the sheet can be measured in two ways, according to the charge of the octahedral cation: - if it is divalent (Mg2 +, Fe2 +, ...), all the octahedral cavities are occupied; the leaflet is then called trioctaedric, - if it is trivalent (Al3 +, Fe3 +, ...), two octahedral cavities out of three are occupied and the leaflet is dioctahedral.

 But many substitutions are possible, both in the tetrahedral layer and in the octahedral layer. These can lead to a sheet filler deficit and the neutrality of the crystal is then achieved by inserting compensating cations between the sheets.

 Among the clays TOT, the three classes are: smectites, vermiculites and micas.

 Among the clays, the class preferably used according to the invention is that of smectites.

 Smectites are classified according to the nature of the M metal (aluminum, magnesium, iron, lithium), the nature of the compensating cation (sodium, potassium, calcium) and the nature of the tetrahedral or octahedral substitution.

One can thus quote among the class of smectites:
montmorillonites of formula Si4 (Al2-y Mgy) O10 (OH) 2> M + y
beidellites of formula (Si4-xAlx) Al2O10 (OH) 2, M + x
nontronites of formula (Si4xAlx) Fe2O10 (OH) 2, M + x
hectorites of formula S4 (M93y Liy) O1O (OH) 2, M + y
stévensites of formula Si4 (Mg3y) O10 (OH2), M + 2y
saponites of formula (Si4-xAlx) Mg3O10 (OH2), M + x
It is still particularly preferred in the context of the present invention to use montmorillonites.

Commercial clays that are already acidic may be used, such as in particular: the following clays: KSF, TONSIL OPTIMUM FF and K 10 sold by Süd
Chem ie.

 Commercial clays, which may or may not be acidic, may also be treated with an aqueous solution of an acid. The concentration of the aqueous solution in acid is variable, however it must have a pH greater than or equal to 2 so as not to destroy the clay and it must contain a quantity of H + ions expressed in milliequivalents corresponding to at least the capacity of exchange of clay. The capacity of exchange of a clay is defined as the number of monovalent cations, expressed in milliequivalents that can exchange 1 g of sample.

 This exchange capacity (or charge per half-mesh) varies for smectites between 0.2 and 0.6 and for vermiculites between 0.6 and 0.9. It is therefore preferable in the context of the present invention to use an acidic solution containing as many H + allyl as there will be cations to be exchanged in the clay, thus containing at least 0.6 and preferably at least minus 1 milliequivalent acid for 1 g of clay.

 If necessary, to improve the exchange surface of the clay, it may then be treated with an alcohol such as methanol and then dried.

 Also suitable for carrying out the process of the invention are bridged type clays.

 By bridged clay is meant clays between the leaflets from which bridges or pillars have been introduced which maintain a basic spacing.

Basal spacing (or interfoliar distance) is the sum of the thickness of a clay leaflet and the interfoliar spacing.

 Examples of mineral species creating the pillars or bridges include those derived from the following elements: aluminum, nickel, cobalt, vanadium, molybdenum, rhenium, iron, copper, ruthenium, chromium, lanthanum, cerium, titanium, boron, gallium , zirconium, niobium, tantalum, silic.

 The bridged clays preferably used in the process of the invention are clays bridged by abutments of aluminum oxide, zirconium, chromium, silicon and cerium.

 Said clays are prepared according to the methods described in the literature.

Reference can be made inter alia to the preparation of aluminum bridged clays at FR-A-2,563,446 and FR-A-2,656,298; of titanium bridged clays
FR-A 2,669,016 and clay bridged with cerium at French Patent Application No. 91/04409.

 Among the bridged clays, the smectite-type clays are particularly used. Among these smectites, non-limiting examples include beidellites, in particular synthetic beidellites and montmorillonites.

Bridged clays can be obtained by a process comprising the following steps:
a) treatment of a natural or synthetic clay, in the form of a
aqueous suspension, with an aqueous solution containing at least one
hydroxide of at least one metal,
b) removing the excess of unreacted metal hydroxide on
clay; said removal and drying of the treated clay,
c) the heat treatment of the treated clay; said treatment leading to
obtaining the bridged clay.

 For the preparation of bridged clays that can be used in the context of the invention, it is also possible to implement steps a) and b).

 Bridging of argild; It can be carried out using the hydroxides of the abovementioned metals.

 Preferably, a catalyst is used in the process of the invention, a beidellite or montmorillonite bridged with aluminum hydroxide, for example according to the process described in FR-A-2,563,446.

 Examples of catalysts that are also suitable for the present invention include natural zeolites such as, for example: chabazite, clinoptilolite, erionite, mordenite, phillipsite, and offeretite.

 Synthetic zeolites such as zeolite ZSM-5, zeolite Y, ferrierite are very well suited to carrying out the invention; zeolite X of faujasite type, zeolite of type L, mordenite, zeolite ZSM-1 1; the mazzite, the offer. Whatever the zeolite, we make a treatment that makes it acidic.

Preferential use is made of synthetic zeolites and more particularly of commercial zeolites which are in the following forms:
zeolites in acid form, such as zeolites ZSM-5 or silicalite
aluminum silal ratio of 10 to 500; zeolites Y in
particular zeolites obtained after dealumination treatment (by
example hydrotreatment, washing with hydrochloric acid or treatment
SiCI4) and more particularly the US-Y zeolites of
Si / Al molar ratio greater than 3, preferably between 6 and 60; the
zeolites such as ferrierite with a SVAI molar ratio of 5 to 10,
zeolites in exchangeable sodium or potassium form, such as
zeolite X faujasite type of Si / Al molar ratio of 1 to 1.5, the zeolite of
type L of Si / Al molar ratio of 3 to 3.5, the molar ratio mordenite
If / AI from 5 to 6, zeolite ZSM-11 of Si / Al molar ratio of 5 to 30,
zeolites both in acid form or in sodium form or
exchangeable potassium such as the molar ratio mazzite Si / Al of
3.4, the SUAI molar ratio offer of 4.

 According to the process of the invention, the zeolite used in the process of the invention is an acidified zeolite.

 To acidify the zeolite if necessary, the conventional treatments are used.

 Thus, it is possible to exchange the alkaline cations by subjecting the zeolite to a treatment carried out with ammonia, thus leading to an exchange of the alkaline cation by an ammonium ion and then to calcining the zeolite exchanged in order to thermally decompose the ammonium cation and replace it with an H + ion.

 The amount of ammonia to be used is at least equal to the amount necessary to exchange all the alkaline cations to Ni4 + ions.

 At least 5.10-3 to 10-5 moles of ammonia per gram of zeolite are therefore used.

 The exchange reaction of the exchangeable cation by NH 4 + is carried out at a temperature which is between room temperature and the reflux temperature of the reaction medium. The operation lasts a few hours and can be repeated.

Zeolites can also be acidified by subjecting them to a conventional acidic treatment. This treatment can be carried out by adding an acid such as in particular hydrochloric acid, sulfuric acid, nitric acid,
Perchloric acid, phosphoric acid and trifluoromethanesulfonic acid.

 According to a preferred embodiment, the zeolite is acidified by passing a volume of acid having a normality of between 0.1 and 2 N per gram of zeolite between 10 mvg and 100mVg. This passage can be carried out in a single step or preferably in several successive steps.

It will not be departing from the scope of the present invention to use a modified acid zeolite, for example by using zeolites of the following type:
ZSM-5 and ZSM-11 in which part of the aluminum is replaced by an element such as iron, gallium, boron, indium, chromium, scandium, cobalt, nickel, beryllium, zinc, copper, antimony, arsenic, vanadium or their mixture.

 As examples of other solid catalysts with acidic properties suitable for carrying out the process of the invention, mention may be made of phosphates such as, in particular, boron, aluminum or gallium phosphates.

In particular, it is possible to use lamellar phosphates of tetravalent metals corresponding to the formula a-M (HPO 4) 2, pH 20 in which M represents a tetravalent metal chosen from titanium, germanium, zirconium or tin and p is a less than 2. These compounds are described in the literature and reference can be made inter alia to the work of ALBERTI et al - J. of
Inorg. Nucl. Chem. 40, p. 1113 (1978).

 We can also implement. lamellar phosphonates of tetravalent metals and particularly lamellar phosphonates of zirconium (US Pat. No. 4,436,899).

 Oxides made acidic by a treatment are also suitable for the invention. Sulphated, chlorinated or fluorinated oxides may be mentioned. Those which are used preferentially are sulfated oxides of titanium, zirconium or iron. These oxides are described in the literature and reference can be made, inter alia, to EP-A 0 397 553.

 Another characteristic of the process of the invention is to use a ketone compound and more particularly those corresponding to formula (II): R a COXRb (II) in said formula (II): R a and R b are identical or different, represent hydrocarbon radicals having from 1 to 30 carbon atoms or together form a divalent radical, optionally substituted with one or more halogen atoms or functional groups that are stable under the conditions of the reaction, -X represents a valency bond, a -CO- group, -CHOH group or - (R) - group, representing an alkylene group preferably having 1 to 4 carbon atoms and n is an integer selected from 1 to 16.

 In formula (II), Ra and Rb are more particularly: linear or branched alkyl radicals, linear or branched alkenyl radicals, cycloalkyl or cycloalkenyl radicals containing from 4 to 6 carbon atoms, mono aryl radicals, - or polycyclic; in the latter case, the rings forming between them an ortho- or ortho- and peri-condensed system or being linked to one another by a valency bond, - arylaryl or arylacenyl radicals, - Ra and Rb may together form an alkylene or alkenylene radical comprising 3 to 5 carbon atoms, optionally substituted by a lower carbon alkyl radical or a cycloalkyl or cycloalkenyl radical having 4 to 6 carbon atoms; 2 to 4 carbon atoms of the alkylene or alkenylene radicals may be part of one or two benzene rings optionally substituted with 1 to 4 hydroxyl groups and / or alkyl and / or alkoxy low carbon condensation.

 In the following description of the invention, the term "low carbon condensation alkyl group" means a linear or branched alkyl group generally having 1 to 4 carbon atoms.

 The aforementioned hydrocarbon radicals may be substituted with 1 or more, preferably 1 to 4, alkyl groups of low carbon condensation or functional groups such as hydroxyl groups, low carbon alkoxy condensation. hydroxycarbonyl, alkyloxycarbonyl having 1 to 4 carbon atoms cyans alkyl group, a nitrile group, -SO3H, nitro or with one or more halogen atoms, including chlorine and bromine.

 Preferably, Ra and Rb are more particularly: linear or branched alkyl radicals having from 1 to 10 carbon atoms, linear or branched alkenyl radicals having from 2 to 10 carbon atoms, cycloalkyl or cycloalkenyl radicals containing 4 to 6 carbon atoms, phenyl radicals optionally substituted with 1 to 4 alkyl and / or hydroxyl and / or alkoxy groups, phenylalkyl or phenylacenyl radicals containing 1 (or 2) to 10 carbon atoms in the aliphatic part, and even more particularly from 1 (or 2) to 5 carbon atoms in the aliphatic portion, - R a and R b may together form an alkylene or alkenylene radical having from 3 to 5 carbon atoms, optionally substituted with 1 to 4 alkyl radicals with low carbon condensation.

As specific examples of ketones which can be used in the process of the invention, mention may be made, more particularly: acetone, butanone-2-methylisopropylketone-pivalone-pentanone-2-pentanone-3 4-methylpentanone-2-dimethyl-3,3-butanone-2-hexanone-2-hexanone-3-heptanone-2-heptanone-4-octanone-2-I octanone-3-nonanone-2-nonanone-5 pentadecanone-8-methyl-2 hexanone-3-methyl-5-hexanone-2-methyl-5-hexanone-3-dimethyl-2,4-pentanone 3-methyl-5-heptanone-3-methyl-vinyl ketone-mesityl oxide-penten-1-one-3-penten-3-one-2-hexen-5-one-2-methyl-5-hexene 3 one-2-methyl-6-heptene-5-one-2-diacetyl-diacetone-alcohol-acetoin-2,3-butanedione-2,4-pentanedione-2,5-hexanedione dicyclohexylketone - methylcyclohexylketone - acetophenone - n-propiophenone - n-butyrophenone - I ' isobutyrophenone - n-valerophenone - 2-methylacetophenone - 2,4-dimethylacetophenone - phenylvinylketone - benzophenone - 2-methylbenzophenone - 2,4-dimethylbenzophenone - 4,4'-dimethylbenzophenone 2,2'-dimethylbenzophenone - 4,4'-dimethoxybenzophenone - 4-hydroxybenzophenone - 4,4'-dihydroxybenzophenone - 4-benzoylbiphenylbenzoin - 4,4'-dihydroxy benzoin - 2,4-dimethylbenzoin - 4,4'-dimethylbenzoin - 4,4'-dimethoxybenzoin - 4,4'-difluorobenzoin - o'-methoxybenzoin - where ethoxy benzoin - deoxybenzoin - 4-hydroxy-deoxybenzoin - 4-methyl-deoxybenzoin - 4-methoxy-deoxybenzoin - 4,4-dimethoxy-deoxybenzoin - 4,4-difluoro-deoxybenzoin - ss-phenylpropiophenone - dibenzylketone - Sphenylvalerophenone - diphenyl-1, 1 propanone-2 - 1,3-diphenylpropanone - benzalacetone - benzalacetophenone - benzyl cyclopentanone, 2-methylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3,3,5,5-tetramethylcyclohexanone, cyclopenten-2-one, cyclohexen-2-one, and ocisophorone, ss-isophorone - cyclohexenyl-cyclohexanone - o'-indanone - 5-indanone - α-tetralone - fluorenone
Thus, the dialkyl ketone ketone compounds of formula (II) in which Ra and Rb represent a linear or branched alkyl radical having from 1 to 8 carbon atoms and alkylphenones, that is to say, are particularly used. that is Ra represents a linear or branched alkyl radical having from 1 to 6 carbon atoms and Rb represents a phenyl radical.

 As more specific examples of dialkylketones and alkylphenones, pentanones, acetophenone and n-valerophenone may be mentioned.

 According to the process of the invention, during the hydroxylation process, the use of the phenolic compound of formula (I) involves a mineral solid catalyst with acidic properties and a ketone compound.

 The amount of acid catalyst that is used in the process of the invention can vary within wide limits.

 When the process is carried out batchwise, the catalyst may represent, by weight relative to the phenolic compound of formula (I) employed, from 0.1 to 20%, preferably from 0.5 to 10%. However, if the process is carried out continuously, for example by reacting a mixture of phenolic compound (I) and hydrogen peroxide solution on a fixed bed of catalyst, these catalyst / phenolic compound ratios of formula (I) do not make sense and at a given moment, we can have a weight excess of catalyst relative to the phenolic compound of formula (I).

 The ketone compound of formula (II) which has previously been defined is used in a quantity defined below.

 Generally, the amount of the ketone compound of formula (II) expressed in moles per mole of hydrogen peroxide varies between 1.10-3 mole and 10. It is not necessary to exceed 1.0 mole of ketone compound per mole of peroxide hydrogen. In practice, the amount of ketone compound is most often between 0.05 and 1.0 mole per mole of hydrogen peroxide.

 The hydrogen peroxide used according to the invention may be in the form of an aqueous solution or an organic solution.

 Aqueous solutions being commercially more readily available are preferably used.

The concentration of the aqueous solution of hydrogen peroxide, although not critical in itself, is chosen so as to introduce as little water as possible into the reaction medium. An aqueous solution of hydrogen peroxide with at least 20% by weight of H 2 O 2 and preferably around 70% is generally used.
The amount of hydrogen peroxide can be up to 1 mole of H 2 O 2 per 1 mole of phenolic compound of formula (I).

 However, it is preferable to obtain an industrially acceptable yield of using a molar ratio of hydrogen peroxide / phenolic compound of formula (I) of 0.01 to 0.3 and preferably of 0.05 to 0.10.

 In order to have a sufficient reaction rate, the initial content of the water medium is limited to 20% by weight and preferably to 10% by weight.

 The weight contents indicated are expressed relative to the phenolic compound mixture of formula (I) / hydrogen peroxide / water.

 This initial water corresponds to the water introduced with the reagents and in particular with hydrogen peroxide.

 According to the process of the invention, the hydroxylation of the phenolic compound of formula (I) is carried out at a temperature which may be between 45 ° C. and 150 ° C.

 A preferred variant of the process of the invention consists in choosing the temperature between 45 ° C. and 75 ° C.

 The reaction is advantageously carried out under atmospheric pressure.

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

 In a preferred manner, the order of the following reagents is chosen: the phenolic compound of formula (I), the acidic mineral catalyst and then the ketone compound of formula (II) are introduced.

 The reaction medium is brought to the desired temperature and then the hydrogen peroxide solution is added progressively.

 At the end of the reaction, the unprocessed phenolic compound and the ketone compound of formula (II) are separated from the hydroxylation products by the usual means, in particular by distillation and are returned to the reaction zone.

Among the phenolic compounds of formula (I) which may be used in the process of the invention, mention may be made, without limitation, of phenol,
Anisole, orthocresol, paracresol, metacresol, 4-tert-butylphenol, 2-methoxyphenol, 4-methoxyphenol.

 The present process is particularly suitable for the preparation of hydroquinone and pyrocatechol from phenol.

 The following examples illustrate the invention without limiting it.

In the examples, the following abbreviations mean:
- number of moles of hydrogen peroxide transformed TT =
number of moles of hydrogen peroxide introduced
number of moles of hydroquinone formed RTHQ =
number of moles of hydrogen peroxide transformed
number of moles of pyrocatechin formed
PSTN =%
number of moles of hydrogen peroxide transformed
EXAMPLES
The following is the operative protocol which will be followed in all the examples.

In a 100 ml glass flask equipped with a central stirrer, a condenser, a dropping funnel and a thermometer, the following are charged:
47 g (0.50 mol) of phenol,
xg of a ketone compound of formula (II).

 Y g of acidic mineral catalyst is then introduced.

 The different quantities (x and y) can be determined from the indications given in the summary tables.

 The reaction mixture is brought to the selected reaction temperature 75 ° C, while stirring at 1200 rpm.

 The aqueous solution of hydrogen peroxide 70.5% by weight is introduced via the dropping funnel in 2 minutes in an amount also specified in the following tables.

 The reaction mixture is stirred at 75 ° C for the time mentioned in the following tables.

 The reaction mixture is then cooled and the reaction products are assayed: the residual hydrogen peroxide is determined by iodometry and the diphenols formed are determined by high performance liquid chromatography.

EXAMPLES 1 to 4
In this series of examples, a US-Y zeolite is used as catalyst and as a cocatalyst acetophenone (example 2), nvalerophenone (example 3) and pentanone-2 (example 4).

 Example 1 is a comparative example without a ketone compound.

 The zeolite US-Y is a zeolite marketed by the company TOSOH having a molar ratio Si / Al equal to 6.0.

 The tests are conducted according to the previously defined operating protocol.

All the operating conditions and results obtained are recorded in the following table (I): TABLE I
Hydroxylation of phenol with H2O2 / zeolite US-Y / Ketone compound of formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQPC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 1 <SEP> without <SEP> US-Y <SEP> 5,15.10-2 <SEP> 2 <SEP> H <SEP> 30 <SEP> 56 <SEP> 15.5 <SEP> 31.5 <SEP> 0.49
<tb> (1,0)
<tb> 2 <SEP> acetophenone <SEP> US-Y <SEP> 5.05.10-2 <SEP> OH <SEP> 20 <SEP> 94 <SEP> 35.0 <SEP> 37.5 <SEP> 0 93
<tb> (0.96) <SEP> (1.0)
<tb> 3 <SEP> n-valerophenone <SEP> US-Y <SEP> 5.0.10-2 <SEP> 2 <SEP> H <SEP> 30 <SEP> 90 <SEP> 27.0 <SEP> 42 , 0 <SEP> 0.64
<tb> (1.0) <SEP> (1.0)
<tb> 4 <SEP> Pentanone-2 <SEP> US-Y <SEP> 5.0.10-2 <SEP> 2 <SEP> H <SEP> 30 <SEP> 99.5 <SEP> 30.5 <SEP > 43.5 <SEP> 0.07
<tb> (0.99) <SEP> (1.0)
<Tb>
EXAMPLES 5 to 8
In this series of examples, ZSM-5 zeolite is used as a catalyst and acetophenone (examples 6 and 7) and pentanone-2 (example 8) as cocatalyst.

 Example 5 is a comparative example without a ketone compound.

Zeolite ZSM-5 is a zeolite marketed by the Company
CONTEKA having an SiO2 / AI203 ratio of 30.

 The tests are conducted according to the previously defined operating protocol.

All the operating conditions and results obtained are recorded in the following table (II): Table II
Hydroxylation of phenol with H2O2 / zeolite ZSM-5 of SiO2 / Al2O3 ratio = 30 / Ketone compound of formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQ / PC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 5 <SEP> without <SEP> ZSM-5 <SEP> 5.0.10-2 <SEP> 5 <SEP> H <SEP> 30 <SEP> 94.5 <SEP> 12.5 <SEP> 18 , 5 <SEP> 0.68
<tb> (1,0)
<tb> 6 <SEP> Acetophenone <SEP> ZSM-5 <SEP> 5.2.10-2 <SEP> 6 <SEP> H <SEP> 30 <SEP> 96 <SEP> 20 <SEP> 29 <SEP> 0 69
<tb> (2.0) <SEP> (1.0)
<tb> 7 <SEP> Acetophenone <SEP> ZSM-5 <SEP> 5.35.10-2 <SEP> 5 <SEP> H <SEP> 30 <SEP> 86 <SEP> 28 <SEP> 37.5 <SEP > 0.75
<tb> (2.0) <SEP> (0.2)
<tb> 8 <SEP> Pentanone-2 <SEP> ZSM-5 <SEP> 5.2.10-2 <SEP> 4 <SEP> H <SEP> 00 <SEP> 91 <SEP> 16.5 <SEP> 27 <SEP> 0.61
<tb> (2.0) <SEP> (1.0)
<Tb>
EXAMPLES 9 to 1 1
In this series of examples, zeolite ZSM-5 is used as a catalyst and acetophenone is used as a cocatalyst (Examples 10 and 11).

 Example 9 is a comparative example without ketone compound.

Zeolite ZSM-5 is a zeolite marketed by the Company
CONTEKA having an SiO2 / Al2O3 ratio of 52.

 The tests are conducted according to the previously defined operating protocol.

All the operating conditions and results obtained are recorded in the following table (III): Table III
Hydroxylation of phenol with H 2 O 2 / zeolite ZSM-5 of SiO 2 / Al 2 O 3 ratio = 52 / Ketone compound of formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQ / PC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 9 <SEP> without <SEP> ZSM-5 <SEP> 5.0.10-2 <SEP> 3 <SEP> H <SEP> 40 <SEP> 96 <SEP> 12.5 <SE> 18 <SEP > 0.69
<tb> (1,0)
<tb> 10 <SEP> Acetophenone <SEP> ZSM-5 <SEP> 5.4.10-2 <SEP> 3 <SEP> H <SEP> 00 <SEP> 98.5 <SEP> 25.5 <SEP> 30 , 5 <SEP> 0.84
<tb> (2.0) <SEP> (1.0)
<tb> 11 <SEP> Acetophenone <SEP> ZSM-5 <SEP> 5.2.10-2 <SEP> 6 <SEP> H <SEP> 00 <SEP> 97 <SEP> 27 <SEP> 35.5 <SEP > 0.76
<tb> (2.0) <SEP> (0.2)
<Tb>
EXAMPLES 12 and 13
In Example 13, the acidified VolClay clay is used as catalyst and acetophenone is used as cocatalyst.

 Example 12 is a comparative example without ketone compound.

 The catalyst is a Volclay-type clay which has been acidified using a 10% by weight aqueous solution of hydrochloric acid. The amount of acid used in 100 ml of clay suspension (10 g) is such that a pH of 2.0 is obtained.

 The tests are conducted according to the previously defined operating protocol.

- All the operating conditions and results obtained are recorded in the following table (IV): Table IV
Hydroxylation of phenol with H2O2 / Acidified Voclay Clay / Ketone Compound of Formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQ / PC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 12 <SEP> without <SEP> clay <SEP> acidified <SEP> 5.05.10-2 <SEP> 5 <SEP> H <SEP> 00 <SEP> 77 <SEP> 20.5 <SEP> 35 , 5 <SEP> 0.58
<tb> (0.3)
<tb> 13 <SEP> Acetophenone <SEP> Acidified Clay <SEP><SEP> 4.9.10-2 <SEP> 5 <SEP> H <SEP> 93 <SEP> 29.5 <SEP> 39.5 <SEP > 0.75
<tb> (1,0) <SEP> (0,3) <SEP> 00
<Tb>
EXAMPLES 14 and 15
In Example 15, acetophenone is used as the catalyst for aluminum-cleaved clay and as a co-catalyst.

 Example 14 is a comparative example without ketone compound.

The catalyst is a clay bridged with aluminum obtained according to the procedure given below:
Preparation of bridged clay:
Wyoming montmorillonite, also known as Volclay bentonite, is used.

. preparation of the 2 μm fraction of the clay
An aqueous suspension is prepared at 20 g / l of this clay, which is
shake violently and allow to decarrate for 24 hours.

The fraction is then taken at 2 μm from the clay
(solution a).

. preparation of the clay in sodium form
To the solution a), excess sodium chloride is added, relative to
the capacity of exchange of the clay, about 1000 milliequivalents of
sodium for 100 g of clay. The solution is stirred for 1 hour at
ambient temperature. The clay is then filtered from the solution.

We repeat the operation a second time. The clay is then washed
distilled water until the chloride ions disappear in the wash water.

 The clay is then resuspended in water to 20 g / l (solution b).

- preparation of the aluminum hydroxide solution
A 0.4 M solution of aluminum nitrate is prepared at which
added, with stirring and at ambient temperature, a 0.24M solution
dammoniac slowly and regularly. We follow the pH of the solution
until an OH / Al ratio of 1.2 is obtained. We then stop adding
ammonia. The solution is heated to 50 ° C., while stirring during
about r hour (solution c).

. bridging step
1.4 liters of solution c) are added to 0.9 liters of solution b). We shake
for 1 hour at room temperature. Solution d) is obtained.

separation of bridged clay
The solution obtained previously is dialyzed with a membrane with
dialysis in cellulose acetate, for 4 days against 10 liters of water
swapped every day. The bridged clay is then separated from the solution by
centrifugation.

It is dried at 100 ° C. for 24 hours and then calcined at 350 ° C.
during 2 hours.

The clay obtained has a basal spacing of 1.80 nm, a surface area
BET specificity of 270 cm 2 / g and a pore volume of 0.20 cm 3 / g.

 The tests using the catalyst prepared above are carried out according to the previously defined operating protocol.

All the operating conditions and results obtained are recorded in the following table (V): Table V
Hydroxylation of phenol with H2O2 / bridged clay Al2O3 / Ketone compound of formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQ / PC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 14 <SEP> without <SEP> clay <SEP> bridged <SEP> 4,7.10-2 <SEP> 3 <SEP> H <SEP> 10 <SEP> 96 <SEP> 5,0 <SEP> 20 , 0 <SEP> 0.25
<tb> (1,0)
<tb> 15 <SEP> acetophenone <SEP> clay <SEP> bridged <SEP> 5.1.10-2 <SEP> 1 <SEP> H <SEP> 15 <SEP> 96 <SEP> 16.0 <SEP> 32 , 5 <SEP> 0.49
<tb> (1.0) <SEP> (1.0)
<Tb>
EXAMPLES 16 and 17
In Example 17, a silicealumine is used as catalyst and acetophenone is used as a cocatalyst.

 Example 16 is a comparative example without a ketone compound.

The catalyst is a silica-alumina marketed by the Company
DEGUSSA having a BET surface area of 50 m2 / g and a molar ratio
Si / AI of 3.3.

 The tests are conducted according to the previously defined operating protocol.

All the operating conditions and results obtained are recorded in the following table (Vl): Table VI
Hydroxylation of phenol with H 2 O 2 / silica-alumina / Ketone compound of formula (II)

Ref. <SEP> Compound <SEP> ketone <SEP> (II) <SEP> Catalyst <SEP> Report <SEP> Duration <SEP> TT <SEP> RTHQ <SEP> PSTN <SEP> Report
<tb> [Ratio <SEP> molar <SEP> mineral <SEP> molar <SEP> HQ / PC
<tb> compound <SEP> ketone <SEP> [en <SEP> g <SEP> by <SEP> mole <SEP> of <SEP> H2O2 / phenol
<tb> (II) / H2O2] <SEP> phenol]
<tb> 16 <SEP> without <SEP> silica-alumina <SEP> 5.4.10-2 <SEP> 7 <SEP> H <SEP> 45 <SEP> 23.5 <SEP> 9.5 <SEP> 23 <SEP> 0.41
<tb> (0,5)
<tb> 17 <SEP> acetophenone <SEP> silica-alumina <SEP> 5.3.10-2 <SEP> 23 <SEP> H <SEP> 96 <SEP> 26.5 <SEP> 39 <SEP> 0.68
<tb> (1,0) <SEP> (0,5)
<Tb>

Claims (18)

1 - Process for hydroxylation of phenolic compounds of general formula (I): in which R and R ,, the same or different represent a hydrogen atom, an alkyl radical having 1 to 4 carbon atoms, a cyclohexyl radical, a phenyl radical, by means of hydrogen peroxide, in the presence of an acid catalyst, said process being characterized in that the reaction is conducted in the presence of a ketone compound and an effective amount of a mineral catalyst solid with acidic properties. 2- Process according to claim 1, characterized in that the acidic mineral catalyst is chosen from: silica-alumina, silica-Ga203, silica-B203; acidic clays; bridged clays; natural or synthetic zeolites; phosphates of boron, aluminum or gallium; lamellar phosphates of tetravalent metals corresponding to the formula a-M (HPO4) 2, pH2O in which M represents a tetravalent metal selected from titanium, germanium, zirconium or tin and p is a number less than 2; lamellar phosphonates of tetravalent metals, preferably lamellar phosphonates of zirconium; oxides made acidic by a treatment, preferably sulfated oxides of titanium, zirconium or iron. 3- Method according to one of claims 1 and 2 characterized in that the acidic mineral catalyst used is selected from natural clays having a structure called "1TOT" or tetrahedron octahedron tetrahedron. 4- Method according to one of claims 1 to 3 characterized in that the acidic mineral catalyst used is selected from smectites, vermiculites and micas. 5 - Process according to one of claims 1 to 4, characterized in that the acidic mineral catalyst used is chosen from:  montmorillonites of formula Si4 (Al2 y Mg1) O10 (OH) 2, M + y  beidellites of formula (Si4-xAlx) Al2olo (OH) 2sM + x  nontronites of formula (Si4xAlx) Fe2O10 (OH) 2, M + x  hectorites of formula Si4 (Mg3-y Liy) O10 (OH) 2, M + y  stévensites of formula Si4 (Mg3y) O10 (OH) 2, M + 2y  saponites of formula (Si4-xAlx) Mg3O10 (OH) 2, M + x 6 - Process according to one of Claims 3 to 5, characterized in that the commercial clays, whether already acidic or not, are treated with a solution aueuse of an acid. 7- Method according to one of claims 1 and 2 characterized in that the bridged clay is prepared from a smectite, preferably from a beidellite, in particular a synthetic beidellite or montmorillonite. 8- A method according to claim 7 characterized in that the bridged clay is prepared by bridging the clay with one of the hydroxides of the following metals: aluminum, nickel, cobalt, vanadium, molybdenum, rhenium, iron, copper, ruthenium, chromium, lanthanum, cerium, titanium, boron, gallium, zirconium, niobium, tantalum, silicon. 9- Method according to one of claims 7 and 8 characterized in that the bridged clay is prepared by bridging the clay with aluminum hydroxide. 10- Method according to one of claims 1 and 2 characterized in that the acidic mineral catalyst is chosen from:  natural zeolites such as chabazite, clinoptilolite, erionite,  mordenite, phillipsite, offeretite,  synthetic zeolites such as zeolite ZSM-5, zeolite Y,  ferrierite; zeolite X of faujasite type, zeolite of type L, mordenite,  zeolite ZSM-1 1; the mazzite, the offer. 11 - Process according to claim 10 characterized in that the zeolite used is a zeolite US-Y or zeolite ZSM-5. 12 - Process according to one of claims 10 and 11 characterized in that the zeolite used is an acidified zeolite. 13 - Process according to one of claims 1 to 12, characterized in that the ketone compound used corresponds to formula (II): R a -CO-X-Rb (II) in said formula (II): Ra and Rb, which may be identical or different, represent hydrocarbon radicals having from 1 to 30 carbon atoms or together form a divalent radical, optionally substituted by one or more halogen atoms or functional groups that are stable under the conditions of the reaction, -X represents a valency bond, a -CO- group, a -CHOH group or a - (R) - group, representing an alkylene group preferably having 1 to 4 carbon atoms and n is an integer selected from 1 to 16. 14- Process according to claim 13, characterized in that the ketone compound used corresponds to formula (II) in which Ra and Rb represent: linear or branched alkyl radicals, linear or branched alkenyl radicals, cycloalkyl or cycloalkenyl radicals having from 4 to 6 carbon atoms, mono- or poly-aryl aryl radicals; in the latter case, the rings forming between them an ortho- or ortho- and peri-condensed system or being linked together by a valency bond, - arylalkyl or arylacenyl radicals, - Ra and Rb may together form an alkylene or alkenylene radical comprising 3 to 5 carbon atoms, optionally substituted by a lower carbon alkyl radical or a cycloalkyl or cycloalkenyl radical having 4 to 6 carbon atoms; 2 to 4 carbon atoms of the alkylene or alkenylene radicals may be part of one or two benzene rings optionally substituted with 1 to 4 hydroxyl groups and / or alkyl and / or alkoxy low carbon condensation. 15 - Process according to one of claims 1 to 14, characterized in that the ketone compound used is chosen from dialkylketone-type ketone compounds corresponding to formula (II) in which Ra and Rb represent a linear alkyl radical or branched compound having from 1 to 8 carbon atoms and alkylphenones having the formula (II) wherein Ra represents a linear or branched alkyl radical having from 1 to 6 carbon atoms and Rb represents a phenyl radical. 16- The method of claim 15 characterized in that the ketone compound is selected from pentanones, acetophenone and n-valerophenone. 17 - Method according to one of claims 1 to 16, characterized in that the amount of acidic mineral catalyst used is by weight relative to the weight of phenolic compound of formula (I) engaged from 0.1 to 20%, and preferably from 0.5 to 10%. 18- Method according to one of claims 1 to 17, characterized in that the amount of ketone compound of formula (II) is at least 1.10-3 per mole of hydrogen peroxide, preferably between 1.1 3 and 10, and even more preferably from 0.05 to 1.0 mole. 19 - Process according to one of claims 1 to 18, characterized in that the phenolic compound of formula (I) is phenol, anisole, orthocresol, paracresol, metacresol, tert-butyl-4-phenol, 2-methoxyphenol, 4-methoxyphenol. 20- Method according to one of claims 1 to 19, characterized in that the phenolic compound of formula (I) is phenol.