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Definitions

• hydroxylation of aromatic compounds in the presence of an oxidant, in particular hydrogen peroxide, and a catalyst leads to the formation of hydroxylated aromatic compounds, such as hydroquinone (HQ) and pyrocatechol (PC ) for the phenol, but also to the formation of secondary products including tars.
• HQ hydroquinone
• PC pyrocatechol
• the conversion of the starting aromatic compound must be limited, and is for example in the case of phenol of 5 to 30%.
• hydroquinone is relatively important, particularly in the field of polymerization inhibitors.
• One way to meet this growing demand for hydroquinone would be to direct the hydroxylation reaction of phenol to the formation of hydroquinone.
• TS-1 and TS-2 are zeolites characterized by the presence of titanium atoms replacing silicon atoms in the structure. These zeolites have respectively an MFI or MEL structure and are generally obtained by mixing a source of silicon, a source of titanium, a structuring agent and a mineralizing agent, the mixture obtained is then crystallized for 1 to 4 hours. 10 days at a temperature typically close to 175 ° C and finally calcined for 3 to 12 hours at a temperature typically close to 550 ° C. Processes for the preparation of TS-1 are in particular described in US4410501 or EP031 1983.
• TS-1 and TS-2 have interesting catalytic properties and are thus used in many reactions such as hydroxylation of phenol, rammoximation of cyclohexanone or epoxidation of alkenes.
• An object of the present invention is to provide an improved method of hydroxylation of aromatic compounds, and in particular phenol, anisole and para-t-butyl phenol.
• Another object of the present invention is to provide a method of hydroxylation of phenol for the preparation of hydroquinone and pyrocatechol with a PC / HQ molar ratio of less than 1, 4, preferably less than 1, 2, more preferred less than 1, preferably strictly less than 0.8, preferably strictly less than 0.7.
• Another object of the present invention is to provide a zeolite titano-silicalite suitable for this method of hydroxylation of aromatic compounds.
• the present invention relates to a process for the hydroxylation of a compound of formula
• n is a number from 0 to 4, preferably equal to 0, 1 or 2,
• R 1 represents a hydrogen atom, an alkyl, cycloalkyl, aryl or aralkyl group
• R 2 which may be identical or different, represent an alkyl, alkoxy, hydroxyl, a halogen or a perhaloalkyl group; by reaction of the compound of formula (I) with an oxidizing agent, in the presence of a zeolite titano-silicalite (or zeolite titano-silicalite) prepared by crystallization preceded by a curing step.
• a zeolite titano-silicalite or zeolite titano-silicalite
• alkyl means a linear or branched hydrocarbon chain C1-C15, preferably C1-C1 0 and even more preferably C1-C4.
• alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl and t-butyl.
• alkoxy is meant an alkyl-O- group in which the term alkyl has the meaning given above.
• Preferred examples of alkoxy groups are methoxy or ethoxy.
• cycloalkyl is meant a cyclic hydrocarbon group, monocyclic C 3 -C 8 , preferably a cyclopentyl or cyclohexyl or polycyclic (bicyclic or tricyclic) C 4 - C 18 , especially adamantyl or norbornyl.
• aryl is meant an aromatic mono- or polycyclic group, preferably mono- or bicyclic C 6 -C 2 O, preferably phenyl or naphthyl.
• the group is polycyclic, that is to say that it comprises more than one ring nucleus, the ring nuclei can be condensed two by two or attached in pairs by bonds ⁇ .
• groups (C 6 -C 8) aryl include phenyl, naphthyl.
• aralkyl is meant a linear or branched hydrocarbon-based group carrying a C 7 -C 12 monocyclic aromatic ring, preferably benzyl: the aliphatic chain comprising 1 or 2 carbon atoms.
• perhaloalkyl group means an alkyl group comprising from 1 to 10 carbon atoms and from 3 to 21 halogen atoms, preferably fluorine and more particularly the trifluoromethyl group.
• halogen atom is preferably fluorine, chlorine and bromine.
• the substrates to which the process of the invention applies are in particular phenol; aliphatic phenol ethers; monoalkylphenols, dialkylphenols, trialkylphenols with alkyl groups in dC 4 ; alkoxyphenols with CC 4 alkoxy groups.
• substrates of formula (I) which may be used in the process of the invention, mention may be made, without limitation, of phenol; aliphatic phenol ethers such as anisole, phenetole; alkylphenols such as ⁇ -cresol, p-cresol, m-cresol, 4-tert-butylphenol (or para-tert-butylphenol); alkoxyphenols such as 2-methoxyphenol (guaiacol), 4-methoxyphenol, 2-ethoxyphenol (guetol).
• phenol aliphatic phenol ethers such as anisole, phenetole
• alkylphenols such as ⁇ -cresol, p-cresol, m-cresol, 4-tert-butylphenol (or para-tert-butylphenol)
• alkoxyphenols such as 2-methoxyphenol (guaiacol), 4-methoxyphenol, 2-ethoxyphenol (guetol).
• R 1 represents H
• R 2 represents tert-butyl
• n 1, preferably R 2 is in the para position.
• the hydroxylation process according to the invention makes it possible, in particular, from the phenol, the preparation of hydroquinone and of pyrocatechol with a molar ratio PC / HQ of less than 1, 4, preferably less than 1.2, more preferably less than 1, preferably strictly less than 0.8, and even more preferably less than 0.7.
• the molar ratio PC / HQ is at least equal to 0.05.
• the oxidizing agent is hydrogen peroxide (H 2 O 2 ).
• the oxidizing agent is used in a molar ratio relative to the compound of formula (I) of from 0.005 to 0.60, preferably from 0.05 to 0.50 and even more preferably from 0.15 to 0.35.
• the hydrogen peroxide titer is typically 10 to 70%, and most often 20 to 30%.
• the hydroxylation reaction is carried out in the presence of a solvent, especially chosen from protic solvents, aprotic solvents or a mixture of these solvents.
• the process may especially be carried out in water, in a protic solvent, in an aprotic solvent or in a mixture of water / protic solvent or water / aprotic solvent.
• the protic solvent may be chosen from water, alcohols, especially methanol, ethanol, propanol, isopropanol or tert-butanol and acids, in particular acetic acid.
• the hydroxylation reaction is carried out in water.
• the aprotic solvent may be acetone and any other ketone, nitriles such as acetonitrile, esters such as methyl acetate, ethyl acetate, propyl acetate or butyl acetate.
• the solvent is used in a molar proportion of from 0.05 to 50 relative to the compound (I), preferably from 0.2 to 20.
• the water may be mixed with other solvents in water / solvent molar proportions of 1 / 0.01 to 1/20, preferably of 1 / 0.1 to 1/2 .
• the process according to the invention is a method of hydroxylation of phenol leading to the formation of pyrocatechol and hydroquinone.
• the process of the invention makes it possible to obtain hydroquinone and pyrocatechol in a molar ratio PC / HQ of less than 1.4, of preferably less than 1, 2, more preferably less than 1, even more preferably strictly less than 0.8, and still more preferably less than 0.7.
• the process according to the invention is a process for the hydroxylation of anisole.
• the process according to the invention is a process for the hydroxylation of para-tert-butylphenol.
• the process of the invention may in particular be carried out at a temperature of 50 ° C to 120 ° C, preferably 70 ° C to 100 ° C.
• the method of the invention may in particular be implemented in a period of 5 minutes to several days, for example from 5 minutes to 100 hours.
• the process according to the invention is advantageously implemented in a reactor operating in batch, semi-batch or continuous mode. Different types of reactor can be used for carrying out the process according to the invention.
• the process according to the invention is carried out in a stirred reactor or a cascade of stirred reactors or in a plug flow reactor, for example a tubular reactor arranged horizontally, vertically or inclined. .
• the process according to the invention is preferably carried out with a mass proportion of zeolite relative to the compound of formula (I) of 0.001 to 0.30, preferably of 0.01 to 0.10, and even more preferably from 0.01 to 0.06.
• the matured titano-silicalite zeolite used for carrying out the hydroxylation process according to the invention is a TS-1 or TS-2 zeolite, respectively of the MFI family or of the MEL family.
• zeolites are described in the state of the art but are modified according to the invention by the introduction of a curing step before crystallization to be used in the implementation of the hydroxylation process according to the invention.
• the present invention thus relates to a matured titano-silicalite zeolite, preferably TS-1 or TS-2 matured, preferably TS-1, characterized by an average particle size of 10 to 300 nm, preferably 20 to 150 nm more preferably from 35 to 75 nm.
• the structural study of the different materials is carried out using a X PERT Pro diffractometer.
• the diffractograms are recorded over an angular range of from 5 ° to 90 ° to 200 seconds in steps of 0.02 °.
• the size of the crystallites was also determined by an Ultra 55 Zeiss field-effect scanning electron microscope (SEM) equipped with an InLens detector (FIG. 2) and a JEOL 2010F transmission electron microscope equipped with a field emission gun operating at 200 kV ( Figure 3).
• the crystallite size distribution also was determined by dynamic light scattering (DLS). The measurements were carried out at 20 ° C. using a Vasco DL135 granulometer from Cordouan Technologies.
• the crystallite size distribution was calculated from the autocorrelation function using the Padé-Laplace algorithm (FIG. 4).
• Measurements were applied to synthetic solutions (i.e., solutions obtained after curing, after crystallization and before calcining materials) diluted 10-400 fold in demineralized water and / or sonicated for 1 to 10 minutes but also to solutions obtained, after dispersion of 50 to 100 mg of calcined catalyst in 10 g of demineralized water, and sonicated for 15 minutes.
• this zeolite is also characterized by an infrared absorption band at 550 cm -1 and an infrared absorption band at 960 cm -1 (FIG. 5).
• the ratio between the area of the strip at 960 cm -1 (A 960 ) and the area of the strip at 550 cm -1 (A 550 ) varies between 0 and 1 and preferably between 0.4 and 0.7. .
• the analyzes were carried out with a Jasco 4200 Fourier transform infrared (FT / IR) spectrometer, in attenuated total reflection (ATR), between 400 and 4000 cm -1 .
• FT / IR Fourier transform infrared
• this zeolite is also characterized by a UV absorption band of between 210 and 240 nm (FIG. 6).
• the presence of titanium oxide (UV absorption band at around 330-360 nm) can also be demonstrated by this characterization technique.
• the analyzes were carried out with a Perkin Elmer Lambda 950 spectrophotometer, for wavelengths between 190 and 500 nm.
• the zeolite matured according to the invention and used in the hydroxylation process according to the invention can be advantageously obtained by a manufacturing process comprising a ripening step.
• the specific surface area of this zeolite is between 350 and 600 m 2 / g, preferably between 400 and 500 m 2 / g.
• the measurement of the amount of nitrogen capable of adsorbing on the surface of a porous solid, as a function of the relative pressure P / P 0 makes it possible to determine the specific surface area, the volume and the pore diameter.
• Nitrogen adsorption and desorption are performed in liquid nitrogen (at -196 ° C) using a Belsorp Max. The sample is pretreated under secondary vacuum at 250 ° C. for 16 hours. The sample mass analyzed is about 50-100 mg.
• Nitrogen adsorption and desorption isotherms of a TS-1 are reported as an example in FIG. 7. Nitrogen adsorption is first done in the micropores. Therefore, the analysis of the first part of the curve (P / P 0 ⁇ 0.02) makes it possible to determine the volume and the size of the micropores (BET method and HK method). Then, once the micropores are filled, the adsorption takes place outside the particles. The exploitation of the second part of the curve (0.02 ⁇ P / P 0 ⁇ 0.85) gives access to the external surface of the material (measured from the so-called t-plot method).
• the zeolite has a Ti / (Ti + Si) molar ratio of from 0.0001 to 0.10, preferably from 0.0001 to 0.05, for example from 0.005 to 0.04.
• the present invention also relates to a process for preparing a zeolite titano-silicalite comprising the following steps:
• Step a) of preparing the precursor can be carried out by any method known to those skilled in the art.
• step a) is carried out according to A.J.H.P. Van Der Pol et al. (Appl., Catalan A General 1992 92 93-1 1 1), it includes the following steps:
• the mixture according to step (i) is stirred for 30 minutes to 2 hours, preferably for 1 hour, at a temperature of 20 to 50 ° C, preferably 25 to 40 ° C.
• step (ii) is carried out under an inert atmosphere, for example under argon.
• step a) is performed according to A. Thangaraj et al. (J. Catal. 1991 130 1-8), it comprises in particular the following steps:
• step 2) adding the solution of step 2) into the solution of step 1) at low temperature, preferably 0 ° C;
• the mixture according to step 1) is carried out at ambient temperature (20-25 ° C) for 0.5 to 5 hours, preferably for 2 to 4 hours before step 3).
• the temperature of step 4) is 60 to 100 ° C, for example 80 ° C.
• step a) is carried out according to Serrano et al. (Micro.Mat., 1995, 273-282), it comprises in particular the following steps:
• step F) impregnation of the material obtained in step E) with an aqueous solution of structuring agent and mineralizing agent drip and homogenization.
• step D the material becomes en masse.
• Step E) is carried out at a temperature of 60 to 130 ° C, for example at 100 ° C; for 6 hours to 5 days, for example for 3 days.
• the source of titanium and the source of silicon may be any compound known to those skilled in the art which can be used for the preparation of zeolite titano-silicalite (for example those described by Perego et al., Applied Catalysis A: General, 2001 , 221, 63-72)).
• the sources of titanium and silicon are chosen from titanium or silicon oxides, titanium or silicon alkoxides and titanium or silicon halides.
• the titanium source is a titanium alkoxide, for example tetraethoxytitanium (TEOT) or tetrabutoxytitanium (TBOT).
• the silicon source is a silicon alkoxide, for example tetraethylorthosilicate (TEOS).
• the term "structuring agent” means a structural directing agent which will allow the formation of the zeolite.
• the term “mineralizing agent” is intended to mean any chemical species whose function is to catalyze the hydrolysis and polycondensation of the sources of titanium and silicon. The same entity can play the role of the structuring agent and the mineralizing agent.
• the different structuring agents that can be used, alone or in combination, to prepare TS-1 are chosen from tetrapropylammonium (TPA + ), tetraethylammonium (TEA + ), tetrapropylphosphonium (TPP + ), tetraethylphosphonium (PET + ), l hexapropyl-1,6-hexanediammonium (di-TPA + ), the mineralizing agent can then be the counter-ion selected from HO " , F " and amine.
• TS-2 tetrabutylammonium (TBA + ) and 3,5-dimethyl-N, N-diethylpiperidinium (DMDEP + ), the mineralizing agent being able to then be the counter-ion selected from HO " , F " and amine.
• TAA + tetrabutylammonium
• DDEP + 3,5-dimethyl-N, N-diethylpiperidinium
• the tetrapropylammonium hydroxide acts as the structuring agent and the mineralizing agent (TPA + structuring agent and HO " mineralizing agent).
• structuring agent is typically an aqueous solution between 20 and 40% by weight of structuring agent.
• the molar ratios structuring agent / Si and mineralizing agent / Si are from 0.09 to 0.55, preferably from 0.17 to 0.45.
• the molar ratio H 2 O / Si is between 4 and 80 and preferably between 10 and 30.
• step b) of maturation of the zeolite titano-silicalite corresponds to a thermal heating step, before crystallization, with or without stirring, at a temperature of 20 to 120 ° C., preferably at a temperature of 70 to 100 ° C, more preferably 80 ° C or 90 ° C.
• the b) maturing step is carried out between 30 minutes and 9 months, preferably between 1 hour and 15 days.
• the maturing step b) corresponds to a thermal heating step, before crystallization, at a temperature of 20 to 120 ° C., preferably of 20 to 110 ° C., for 30 minutes at 9 ° C. month.
• the ripening step is conducted between 70 and 100 ° C between 1 hour and 15 days and preferably at 80 ° C between 10 and 35 hours or at 90 ° C between 2 and 20 hours.
• the ripening time will preferably be shorter for a higher temperature.
• the zeolite titanosilicalite ripening step corresponds to a microwave heating step, before crystallization, with or without stirring, at a temperature of 40 to 120 ° C., for 1 to 180 hours. minutes.
• the microwave heating will shorten the curing time.
• microwave heating will reduce the temperature of ripening.
• the crystallization step c) can be carried out, with or without stirring, under autogenous system pressure or under inert gas pressure, for example nitrogen, for example at a pressure of 10 to 120 bar, preferably 20 to 120 bars.
• the crystallization step c) can be carried out with or without stirring, by microwave heating at a temperature of 140 to 200 ° C, for example 175 ° C, for a time below 8 hours, particularly preferably less than 3 hours, for example from 1 to 60 minutes.
• the process for preparing the zeolite titano-silicalite may further comprise a step of washing the crystallized material of step c).
• This step can be carried out by any method known to those skilled in the art and in particular by washing with deionized water.
• This step may in particular be carried out by dispersing the material obtained in step c) in deionized water, this washing step may be repeated several times and preferably until the pH of the solution after washing is less than to 9.
• the process for preparing the zeolite may further comprise a step of recovering the washed material.
• This step can be carried out by any method known to those skilled in the art and in particular by centrifugation, in particular by centrifugation at low temperature.
• the material thus obtained is then dried by any method known to those skilled in the art, in particular by atomization or simple drying at a temperature of 70 to 110 ° C., for 10 to 48 hours.
• the process for preparing the zeolite may further comprise a final calcination step.
• This step can be carried out by any method known to those skilled in the art, in particular by heating at a temperature of 350 to 750 ° C, for example at 550 ° C for 2 to 24 hours.
• the ripening step b) makes it possible to reduce the duration of the crystallization step c) by thermal heating, which must usually be greater than 1 day at 175 ° C., without modifying the catalytic performances of the zeolite.
• the crystallization step is carried out, with or without stirring, from 140 to 200 ° C., for example at 175 ° C. for a time of less than 1 day, preferably less than 12 hours, particularly preferably less than 8 hours, for example from 3 to 6 hours.
• the invention also relates to a zeolite titano-silicalite obtainable by its preparation process.
• the particle sizes obtained after maturing, after crystallization and before calcination are equivalent or identical to those obtained after maturing, after crystallization and after calcination.
• FIG. 1 represents the X-ray diffractogram of a TS-1 type titanosilicalite zeolite which has undergone a maturing stage at 80 ° C. for 14 hours and then crystallized for 5 days at 175 ° C.
• I represents the diffracted intensity
• ⁇ represents half the angle between the incident beam and the diffracted beam.
• FIG. 2 represents a SEM image of a TS-1 type titano-silicalite zeolite which has undergone a maturing stage at 80 ° C. for 14 hours and then has been crystallized for 5 days at 175 ° C.
• FIG. 3 represents a TEM shot of a TS-1 type titanosilicalite zeolite which has undergone a maturation stage at 80 ° C. for 23 hours and then has been crystallized for 5 days at 175 ° C.
• FIG. 4 represents the population (percentage of the number of particles) as a function of the diameter D of the particles of a TS-1 type titanosilicalite zeolite which has undergone a maturation stage at 80 ° C., for 23 hours, and then has been crystallized for 5 days at 175 ° C.
• FIG. 5 represents the IR spectrum of a TS-1 type titanosilicalite zeolite which has undergone a maturation stage at 80 ° C. for 14 hours and then has been crystallized for 5 days at 175 ° C.
• R represents the reflectance and ⁇ represents the wave number.
• FIG. 6 represents the UV spectrum of a TS-1 type titanosilicalite zeolite which has undergone a maturing stage at 80 ° C. for 14 hours and then crystallized for 5 days at 175 ° C.
• F (R ⁇ ) represents the Kubeika Munk function for an infinite thickness of powder and ⁇ represents the wavelength.
• FIG. 7 represents the nitrogen adsorption and desorption isotherms of a TS-1 type titanosilicalite zeolite which has undergone a maturing stage at 80 ° C. for 14 hours and then crystallized 5 days at 175 ° C. ° C.
• V represents the volume Specifically adsorbed gaseous equivalent under standard conditions of temperature and pressure (STP) and P / P 0 represents the relative pressure of gas with respect to atmospheric pressure.
• FIG. 8 represents the UV spectra of different TS-1 titano-silicalite zeolites matured at 80 ° C. for 14 hours and then crystallized at 175 ° C. for 6 hours, 24 hours or 5 days.
• F (R ⁇ ) represents the Kubelka Munk function for an infinite thickness of powder and ⁇ represents the wavelength
• the precursor obtained is placed in a 250 mL autoclave and is then heated without stirring at a determined temperature of 80 ° C or 90 ° C, autogenous pressure, for a specified period of 4.5 to 48 hours.
• the cured precursor is crystallized, without stirring, at 175 ° C, autogenous pressure for 6 hours to 5 days.
• the material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes at 9 ° C. and 12000 rpm and is then washed, that is to say dispersed in about 150 to 200 ml of demineralised water and left stirring for about 1 hour.
• the washing operation is repeated enough times (usually 3 times) so that the pH of the water of the last wash evening is less than 9.
• the solid is recovered by centrifugation for 30 to 45 minutes. at 9 ° C and 12000 rpm.
• the product is dried at 80 ° C for about 16 hours and then calcined at 550 ° C under air for 3 hours.
• This process A describes the preparation of a zeolite titano-silicalite-1 (TS-1).
• TS-2 titano-silicalite-2 zeolite
• the precursor obtained is placed in a 250 ml autoclave and then heated at 80 ° C., autogenous pressure, without stirring, for a determined period of 14 hours.
• the cured precursor is crystallized at 175 ° C., without stirring, autogenous pressure, for 5 days.
• the material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes at 9 ° C. and 12000 rpm and is then washed, that is to say dispersed in about 150 to 200 ml of demineralised water and left stirring for about 1 hour.
• the washing operation is repeated enough times (usually 3 times) so that the pH of the water of the last wash evening is less than 9.
• the solid is recovered by centrifugation for 30 to 45 minutes. at 9 ° C and 12000 rpm.
• the product is dried at 80 ° C for about 16 hours and then calcined at 550 ° C, under air for 3 hours.
• TEOS 1 mmol of TEOS are first hydrolysed with 35.2 ml of an aqueous HCl solution at 237 mmol / l, with stirring, at room temperature for 2 hours.
• aqueous HCl solution 35.2 ml of an aqueous HCl solution at 237 mmol / l, with stirring, at room temperature for 2 hours.
• To this solution are added 4.3 mmol of TBOT previously dissolved in 1.61 mol of isopropanol. The resulting mixture is then stirred for 20 minutes.
• 14 mmol of 25% wt% TPAOH in water are added dropwise. A few seconds after the addition of the TPAOH, the cogel Si0 2 -Ti0 2 becomes en masse. This is then dried at 100 ° C for 3 days. 16.7 g of dry cogel are then collected.
• the precursor obtained is placed in a 250 ml autoclave and then heated at 80 ° C., autogenous pressure, without stirring for a determined period of 14 hours.
• the cured precursor is crystallized at 175 ° C, without agitation, autogenous pressure for 5 days.
• the material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes, at 9 ° C. and 12000 rpm and is then washed, that is to say dispersed in about 150 to 200 ml of demineralized water and left stirring for about 1 hour.
• the washing operation is repeated enough times (usually 3 times) so that the pH of the water of the last wash evening is less than 9.
• the solid is recovered by centrifugation for 30 to 45 minutes. at 9 ° C and 12000 rpm.
• the product is dried at 80 ° C for about 16 hours and then calcined at 550 ° C, under air for 3 hours.
• the precursor obtained is placed in a 250 ml autoclave and then heated at 80 ° C., 30 bars, without stirring, for a determined period of 14 hours.
• the pressure is adjusted by an inert gas such as nitrogen.
• the cured precursor is crystallized at 175 ° C., 60 bar, without stirring, for 5 days.
• the pressure is adjusted by an inert gas such as nitrogen.
• the material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes at 9 ° C. and 12000 rpm and is then washed, that is to say dispersed in about 150 to 200 ml of demineralised water and left stirring for about 1 hour.
• the washing operation is repeated enough times (usually 3 times) so that the pH of the water of the last wash evening is less than 9. Between each wash, the solid is recovered by centrifugation for 30 to 45 minutes. at 9 ° C and 12000 rpm.
• the product is dried at 80 ° C for about 16 hours and then calcined at 550 ° C, under air for 3 hours.
• the hydroxylation of the phenol is carried out in a stirred reactor (500 rpm) semi-batch of one liter in which are first added 200 g of phenol, 60 g of solvent such as water, acetone or methanol and 6 g of catalyst (TS-1 or TS-2).
• the reactor is equipped with a jacket in which circulates a heat transfer fluid heated to 85 ° C to obtain a temperature of 80 ° C in the reaction medium.
• the beginning of the reaction corresponds to the beginning of the introduction of 69.5 g of oxygenated water at 26% by weight in water. This is poured drop by drop, in 2 hours. After the end of the flow of hydrogen peroxide, two or three samples of 5 to 10 g of the reaction medium are made.
• the determination of hydrogen peroxide is carried out by oxidation of iodide ions and the return of iodine formed by sodium thiosulfate.
• the potentiometric titration station used for this analysis is a TitraLab ® 865 of the company Radiometer Analytical.
• the degree of conversion (TT (H 2 0 2 )) of the hydrogen peroxide corresponds to the ratio between the number of moles of hydrogen peroxide converted and the number of moles of hydrogen peroxide introduced.
• the yield of diphenols corresponds to the ratio between the number of moles of diphenols formed (pyrocatechol + hydroquinone) and the number of moles of hydrogen peroxide introduced.
• the yield of pyrocatechol corresponds to the ratio between the number of moles of pyrocatechol formed and the number of moles of hydrogen peroxide introduced.
• the yield of hydroquinone corresponds to the ratio between the number of moles of hydroquinone formed and the number of moles of hydrogen peroxide introduced.
• the selectivity for diphenols corresponds to the ratio between the number of moles of diphenols formed (pyrocatechol + hydroquinone) and the number of moles of hydrogen peroxide transformed.
• Zeolites were prepared according to Method A (Example 2.1), Method D (Example 2.2), Method C (Example 2.3) and Method B (Example 2.4) with a step of curing at 80 ° C for 4.5 minutes. at 48 hours or without a ripening stage. All zeolites prepared underwent a crystallization step at 175 ° C for 5 days and a calcination step at 550 ° C for 3 hours.
• the size of the crystallites was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) after the ripening, crystallization and calcination steps. Crystallite size was also determined by dynamic light scattering (DLS) from aqueous synthetic solutions (i.e., solutions obtained after curing, after crystallization and before calcining materials) diluted from 10 to 400 times in demineralized water and / or sonicated for 1 to 10 minutes but also from solutions obtained, after dispersion of 50 to 100 mg of cured catalyst, crystallized and calcined in 10 g of demineralized water, and sonicated for 15 minutes. The outer surface and the inter-grain distance were determined by nitrogen adsorption / desorption. The results are shown in Table 3.
• the main characteristic of materials matured at 80 ° C is that the apparent average size of the particles is about 1.5 to 2 times lower than that of immature materials (size determined after DLS analysis, observation at TEM and calculated after XRD analysis at from the width at mid-height of the line (101)). Moreover, whatever the synthesis protocol, it is observed that TS-1 particles of 50 to 70 nm are obtained if the zeolite has undergone a maturing step, and this regardless of the curing time at 80 ° C. . The particles being smaller after curing, the space between the grains (D in ter- rains g determined by the BJH method) is consequently lower.
• the zeolites matured for 4.5 to 48 hours at 80 ° C have an external surface area approximately twice that of immature materials.
• the size of the crystallites obtained after the ripening and crystallization steps and before the calcination step is similar, or even identical, to the size of the crystallites obtained after the ripening, crystallization and calcination steps.
• the hydroxylation reaction presented above was carried out with different zeolites prepared according to protocol A having undergone a maturation stage at 80 ° C. for 4.5 h (example 3.2), for 14 h (example 3.3), for 23 h (example 3.4) and during 48h (example 3.5) and at 90 ° C during 14h (example 3.6) and during 23h (example 3.7).
• Example 3.1 A comparative example (Example 3.1) of hydroxylation of phenol was also carried out with a zeolite obtained by Method A but not having undergone the ripening step. All zeolites prepared underwent a crystallization step at 175 ° C for 5 days and a calcination step at 550 ° C for 3 hours.
• T 0 T 0 + T 0 + T 0 + T 0 + T 0 + T 0 + T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0 T 0 + T 0
• the hydroxylation reaction presented above was carried out with different zeolites prepared according to protocol A and having undergone a maturation stage at 80 ° C. for 14 hours and a crystallization step at 175 ° C. for 6 hours (example 4.1). during 24h (example 4.2), for 5 days (example 4.3). All zeolites were calcined at 550 ° C for 3 hours.
• zeolites prepared according to protocol A underwent a ripening step at 80 ° C. for 14 hours and a crystallization step at 175 ° C. for 6 hours (example 5.1). for 24h (example 5.2) and for 5 days (example 5.3). All zeolites were calcined at 550 ° C for 3 hours.
• the size of the crystallites was determined by DRX and DLS. The results are shown in Table 6.
• the molar ratio Ti / (Ti + Si) is respectively 0.013, 0.016 and 0.020 for crystallization times at 175 ° C. for 6 hours, 24 hours and 5 days.
• the increase in titanium content from 0.013 to 0.016 and 0.020 corresponds to the increasing formation of anatase as evidenced in FIG. 8.
• the zeolite used for the hydroxylation reaction of phenol was prepared according to protocol A and first underwent a ripening step at 80 ° C. for 23 h, then a crystallization step at 175 ° C. for 5 days, and finally a calcination step at 550 ° C for 3 hours.

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