PROCESS FOR HYDROXYLATION OF AROMATIC COMPOUNDS, HYDROXYLATION CATALYST AND PROCESS FOR PREPARING SAME

Abstract

The present invention relates to a process for hydroxylation of a compound of formula (I) by reacting the compound of formula (I) with an oxidizing agent, in the presence of a titanium silicalite zeolite prepared by crystallization preceded by a maturing step. The present invention also relates to a titanium silicalite zeolite and to the process for preparing same.

Claims

1.-11. (canceled)

12. A matured TS-1 or TS-2 titano-silicalite zeolite having: an apparent mean particle size of from 35 to 75 nm, an outer surface area of from 60 m.sup.2/g to 150 m.sup.2/g, and an inter-grain distance of from 10 to 30 nm.

13.-14. (canceled)

15. The matured TS-1 or TS-2 titano-silicalite zeolite according to claim 12 further having a specific surface area of between 350 and 600 m.sup.2/g.

16. The matured TS-1 or TS-2 titano-silicalite zeolite according to claim 12 further having a specific surface area of between 400 and 500 m.sup.2/g.

17. The matured TS-1 or TS-2 titano-silicalite zeolite according to claim 12 further having micropores of between 0.40 and 0.50 nm.

18. The matured TS-1 or TS-2 titano-silicalite zeolite according to claim 12 further having micropores of between 0.44 and 0.46 nm.

19. The matured TS-1 or TS-2 titano-silicalite zeolite according to claim 12 further having a mole ratio Ti/(Ti+Si) of from 0.0001 to 0.10.

20. A process for preparing a TS-1 or TS-2 titano-silicalite zeolite, comprising the following steps: a) preparation of a zeolite precursor from at least one source of silicon, at least one source of titanium, at least one mineralizing agent and at least one structuring agent; b) maturation of the zeolite precursor for obtaining a matured precursor; c) crystallization of the matured precursor for obtaining a matured crystalline precursor, and optionally d) calcination of the matured crystalline precursor, wherein said maturation step consists in a step of thermal heating of said zeolite precursor, before crystallization, at a temperature of from 70 to 100 C.

21. The process according to claim 20, wherein said maturation step consists in a step of thermal heating of said zeolite precursor, before crystallization, at a temperature of 80 C. or 90 C.

22. The process according to claim 20, wherein the maturation step is performed for a time of from 30 minutes to 9 months.

23. The process according to claim 20, wherein the maturation step is performed for a time of from 1 hour and 15 days.

24. The process according to claim 20, wherein the source of titanium is a titanium alkoxide.

25. The process according to claim 20, wherein the source of silicon is a silicon alkoxide.

26. A TS-1 or TS-2 titano-silicalite zeolite that may be obtained by the process according to claim 20.

27. A method for hydroxylating an aromatic compound, wherein said aromatic compound is reacted with an oxidizing agent in the presence of a catalyst, said catalyst being a TS-1 or TS-2 titano-silicalite zeolite according to claim 12.

28. A method for hydroxylating an aromatic compound, wherein said aromatic compound is reacted with an oxidizing agent in the presence of a catalyst, said catalyst being a TS-1 or TS-2 titano-silicalite zeolite according to claim 15.

Description

[0093] FIG. 1 shows the X-ray diffractogram of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 14 hours, and which has then been crystallized for 5 days at 175 C. In FIG. 1, I represents the scattered intensity and represents half of the angle between the incident beam and the scattered beam.

[0094] FIG. 2 is an SEM image of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 14 hours, and which has then been crystallized for 5 days at 175 C.

[0095] FIG. 3 is a TEM image of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 23 hours, and which has then been crystallized for 5 days at 175 C.

[0096] FIG. 4 shows the population (percentage of the number of particles) as a function of the diameter D of the particles of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 23 hours, and which has then been crystallized for 5 days at 175 C.

[0097] FIG. 5 shows the IR spectrum of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 14 hours, and which has then been crystallized for 5 days at 175 C. In FIG. 5, R represents the reflectance and represents the wavenumber.

[0098] FIG. 6 shows the UV spectrum of a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 14 hours, and which has then been crystallized for 5 days at 175 C. In FIG. 6, F(R) represents the Kubelka-Munk function for an infinite thickness of powder and A represents the wavelength.

[0099] FIG. 7 shows the nitrogen adsorption and desorption isotherms for a titano-silicalite zeolite of TS-1 type which has undergone a step of maturation at 80 C. for 14 hours, and which has then been crystallized for 5 days at 175 C. In FIG. 7, V represents the specific adsorbed volume in gas equivalent under standard temperature and pressure conditions (STP) and P/P.sub.0 represents the relative pressure of gas relative to atmospheric pressure.

[0100] FIG. 8 shows the UV spectra of various titano-silicalite zeolites of TS-1 type matured at 80 C. for 14 hours, and then crystallized at 175 C., for 6 hours, 24 hours or 5 days. In FIG. 8, F(R) represents the Kubelka-Munk function for an infinite thickness of powder and A represents the wavelength.

EXAMPLES

[0101] Process A for Preparing a titano-silicalite Zeolite According to the Invention

Preparation of the Precursor 377 mmol of Si(OEt)4 (TEOS) (Sigma Aldrich 99.0%) and 8 mmol of Ti(OEt).sub.4 (TEOT) (Alfa Aesar 99+%) are added to a polypropylene flask flushed with a stream of argon. This first solution is then stirred for 1 hour at 35 C. Next, a second solution containing 132 mmol of (C.sub.3h.sub.7).sub.4NOH (TPAOH) at 20% by weight in water is prepared by dilution with demineralized water of the 25% commercial solution (Acros). The addition of the TPAOH solution takes place at 0 C., dropwise. The reaction mixture is then heated at 80 C. for about 3 hours. Finally, 37 g of demineralized water are added so that the volume of the precursor solution is equal to of the volume of the autoclave in which the titano-silicalite zeolite is then crystallized. The molar composition of the resulting clear solution is: SiO.sub.2/TiO.sub.2/TPAOH/H.sub.2O=1/0.02/0.35/21.

Maturation of the Precursor

[0102] The precursor obtained is placed in a 250 mL autoclave and is then heated without stirring at a given temperature of 80 C. or 90 C., under the autogenous pressure, for a given time of from 4.5 to 48 hours.

Crystallization

[0103] The matured precursor is crystallized, without stirring, at 175 C., under the autogenous pressure, for 6 hours to 5 days.

Washing, Drying, Calcination

[0104] The material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm, and is then washed, i.e. dispersed in about 150 to 200 mL of demineralized water and left stirring for about 1 hour. The washing operation is repeated a sufficient number of times (in general three times) such that the pH of the final washing water is less than 9. Between each wash, the solid is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm. Next, the product is dried at 80 C. for about 16 hours and is then calcined at 550 C. in air for 3 hours.

[0105] This process A describes the preparation of a titano-silicalite-1 (TS-1) zeolite. The production of a titano-silicalite-2 (TS-2) zeolite is possible by replacing, during the preparation of the precursor, the TPAOH with TBAOH or any other structuring agent allowing the synthesis of TS-2.

[0106] Process B for Preparing a titano-silicalite Zeolite

Preparation of the Precursor

[0107] 377 mmol of TEOS and 132 mmol of TPAOH at 20% by weight in water are added to a polypropylene flask flushed with a stream of argon. This first solution is then stirred for 3 hours at room temperature. A second solution is then prepared by diluting 8 mmol of Ti(OC.sub.4H.sub.9).sub.4 (TROT) (Acros 99%) in 218 mmol of isopropanol (Acros 99.5%). The addition of this second solution takes place dropwise at 0 C., with continued flushing with argon. The various alcohols present are then removed by heating the reaction mixture at 80 C. for about 3 hours. Finally, 37 g of demineralized water are added so that the volume of the precursor solution is equal to of the volume of the autoclave in which the titano-silicalite zeolite is then crystallized. The molar composition of the resulting clear solution is: SiO.sub.2/TiO.sub.2/TPAOH/H.sub.2O=1/0.02/0.35/21.

Maturation of the Precursor

[0108] The precursor obtained is placed in a 250 mL autoclave and is then heated at 80 C. without stirring, under the autogenous pressure, for a given time of 14 hours.

Crystallization

[0109] The matured precursor is crystallized, without stirring, at 175 C., under the autogenous pressure, for 5 days.

Washing, Drying, Calcination

[0110] The material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm, and is then washed, i.e. dispersed in about 150 to 200 mL of demineralized water and left stirring for about 1 hour. The washing operation is repeated a sufficient number of times (in general three times) such that the pH of the final washing water is less than 9. Between each wash, the solid is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm. Next, the product is dried at 80 C. for about 16 hours and is then calcined at 550 C. in air for 3 hours.

[0111] Process C for Preparing a titano-silicalite Zeolite

Preparation of the Precursor

[0112] 211 mmol of TEOS are first hydrolysed with 35.2 mL of an aqueous solution of HCl at 237 mmol/L, with stirring, at room temperature for 2 hours. 4.3 mmol of TBOT pre-dissolved in 1.61 mol of isopropanol are added to this solution. The mixture obtained is then left stirring for 20 minutes. Next, 14 mmol of TPAOH at 25% by weight in water are added dropwise. A few seconds after the addition of the TPAOH, the SiO.sub.2TiO.sub.2 cogel sets to a solid. This solid is then dried at 100 C. for 3 days. 16.7 g of dry cogel are then recovered. This cogel is ground and then impregnated with 60 mmol of TPAOH at 20% by weight in water. This impregnation is performed by adding the aqueous solution of TPAOH dropwise to the cogel placed in a polypropylene beaker. The mixture is homogenized using a spatula. Finally, a relatively fluid paste is obtained, the molar composition of which is SiO.sub.2/TiO.sub.2/TPAOH/H.sub.2O=1/0.02/0.35/13.

Maturation of the Precursor

[0113] The precursor obtained is placed in a 250 mL autoclave and is then heated at 80 C. without stirring, under the autogenous pressure, for a given time of 14 hours.

Crystallization

[0114] The matured precursor is crystallized, without stirring, at 175 C., under the autogenous pressure, for 5 days.

Washing, Drying, Calcination

[0115] The material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm, and is then washed, i.e. dispersed in about 150 to 200 mL of demineralized water and left stirring for about 1 hour. The washing operation is repeated a sufficient number of times (in general three times) such that the pH of the final washing water is less than 9. Between each wash, the solid is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm. Next, the product is dried at 80 C. for about 16 hours and is then calcined at 550 C. in air for 3 hours.

[0116] Process D for Preparing a titano-silicalite Zeolite According to the Invention

Preparation of the Precursor

[0117] 377 mmol of TEOS and 132 mmol of TPAOH at 20% by weight in water are added to a polypropylene flask flushed with a stream of argon. This first solution is then stirred for 3 hours at room temperature. A second solution is then prepared by diluting 8 mmol of Ti(OC.sub.4H.sub.9).sub.4 (TBOT) (Acros 99%) in 218 mmol of isopropanol (Acros 99.5%). The addition of this second solution takes place dropwise at 0 C., with continued flushing with argon. The various alcohols present are then removed by heating the reaction mixture at 80 C. for about 3 hours. Finally, 37 g of demineralized water are added so that the volume of the precursor solution is equal to of the volume of the autoclave in which the titano-silicalite zeolite is then crystallized. The molar composition of the resulting clear solution is: SiO.sub.2/TiO.sub.2/TPAOH/H.sub.2O=1/0.02/0.35/21.

Maturation of the Precursor

[0118] The precursor obtained is placed in a 250 mL autoclave and is then heated at 80 C. and 30 bar, without stirring, for a given time of 14 hours. The pressure is adjusted by means of an inert gas such as nitrogen.

Crystallization

[0119] The matured precursor is crystallized, without stirring, at 175 C. and 60 bar, for 5 days. The pressure is adjusted by means of an inert gas such as nitrogen.

Washing, Drying, Calcination

[0120] The material obtained after the crystallization step is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm, and is then washed, i.e. dispersed in about 150 to 200 mL of demineralized water and left stirring for about 1 hour. The washing operation is repeated a sufficient number of times (in general three times) such that the pH of the final washing water is less than 9. Between each wash, the solid is recovered by centrifugation for 30 to 45 minutes, at 9 C. and 12 000 rpm. Next, the product is dried at 80 C. for about 16 hours and is then calcined at 550 C. in air for 3 hours.

Phenol Hydroxylation Reaction

[0121] The hydroxylation of phenol is performed in a one-liter semi-batch stirred reactor (500 rpm), to 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-exchange fluid heated to 85 C. to obtain a temperature of 80 C. in the reaction medium. The start of the reaction corresponds to the start of introduction of the 69.5 g of hydrogen peroxide at 26% by weight in water. This solution is added dropwise over 2 hours. After the end of addition of the aqueous hydrogen peroxide solution, two or three samples of 5 to 10 g of the reaction medium are collected. These samples make it possible both to determine the remaining amount of hydrogen peroxide by potentiometric assay, and also to quantify, by liquid-phase chromatographic analysis, the pyrocatechol (PC) and hydroquinone (HQ). Under these operating conditions, the phenol/H.sub.2O.sub.2/H.sub.2O mole ratio is 1/0.25/2.9 and the phenol/TS-1 mass ratio is 1/0.03.

Assay of the Aqueous Hydrogen Peroxide Solution and of the Phenol Conversion Products

[0122] The aqueous hydrogen peroxide solution is assayed by oxidation of iodide ions and back-assay of the formed iodine with sodium thiosulfate. The potentiometric titration station used for this analysis is a Titrelab 865 from the company Radiometer Analytical.

[0123] Pyrocatechol and hydroquinone are analyzed by liquid-phase chromatography (Agilent 1200 series).

[0124] In the examples that follow, the following abbreviations have the meanings as follows:

[0125] The degree of conversion (DC(H.sub.2O.sub.2)) of hydrogen peroxide corresponds to the ratio between the number of moles of hydrogen peroxide converted and the number of moles of hydrogen peroxide introduced.

[0126] The diphenol reaction yield (RY(HQ+PC)/H.sub.2O.sub.2) corresponds to the ratio between the number of moles of diphenols formed (pyrocatechol+hydroquinone) and the number of moles of hydrogen peroxide introduced.

[0127] The pyrocatechol reaction yield (RY(PC)/H.sub.2O.sub.2) corresponds to the ratio between the number of moles of pyrocatechol formed and the number of moles of hydrogen peroxide introduced.

[0128] The hydroquinone reaction yield (RY(HQ)/H.sub.2O.sub.2) corresponds to the ratio between the number of moles of hydroquinone formed and the number of moles of hydrogen peroxide introduced.

[0129] The diphenol selectivity (CY(HQ+PC)/H.sub.2O.sub.2) corresponds to the ratio between the number of moles of diphenols formed (pyrocatechol+hydroquinone) and the number of moles of hydrogen peroxide converted.

Example 1

Effect of the Maturation Step on the Catalytic Performance of TS-1 in the Phenol Hydroxylation Reaction

[0130] The phenol hydroxylation reaction described above was performed with zeolites obtained according to process C (examples 1.1 and 1.2), according to process A (example 1.3), according to process D (example 1.4) and according to process B (example 1.5) in which the maturation step is performed at 80 C. for 14 hours, the crystallization step at 175 C. for 5 days, and the calcination step at 550 C. for 3 hours. Samples were collected from the reaction medium 15 and 60 minutes after the end of the addition of H.sub.2O.sub.2. The results are presented in table 1.

[0131] Comparative reactions were performed with zeolites obtained according to process C (example 1.6), process A (example 1.7) and process D (example 1.8), but which did not undergo the maturation step. These zeolites only underwent the step of crystallization at 175 C. for 5 days and the step of calcination at 550 C. for 3 hours. Samples were collected from the reaction medium 15 and 60 minutes after the end of the addition of H.sub.2O.sub.2. The results are presented in table 2.

TABLE-US-00001 TABLE 1 Sample collection Examples according to the invention (T.sub.0 = 2 h = 1.1 1.2 1.3 1.4 1.5 addition T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + time of H.sub.2O.sub.2) 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min DC(H.sub.2O.sub.2) (%) 89 99 93 99 84 98 93 99 85 98 RY(HQ)/H.sub.2O.sub.2 49 53 46 46 43 46 49 49 40 49 (%) RY(PC)/H.sub.2O.sub.2 30 32 29 28 27 29 29 31 29 30 (%) RY(HQ + PC)/ 79 85 75 74 70 75 78 80 70 78 H.sub.2O.sub.2 (%) CY(HQ + PC)/ 89 86 81 75 83 76 83 80 82 79 H.sub.2O.sub.2 (%) PC/HQ 0.62 0.61 0.63 0.62 0.64 0.63 0.59 0.63 0.73 0.61 mole ratio

TABLE-US-00002 TABLE 2 Sample collection Comparative examples (T.sub.0 = 2 h = 1.6 1.7 1.8 addition time T.sub.0 + 15 T.sub.0 + 60 T.sub.0 + 15 T.sub.0 + 60 T.sub.0 + 15 T.sub.0 + 60 of H.sub.2O.sub.2) min min min min min min DC(H.sub.2O.sub.2) (%) 67 81 65 80 74 89 RY(HQ)/H.sub.2O.sub.2 (%) 26 31 24 28 32 37 RY(PC)/H.sub.2O.sub.2 (%) 20 24 21 23 23 26 RY(HQ + PC)/ 46 54 45 52 55 63 H.sub.2O.sub.2 (%) CY(HQ + PC)/ 69 67 69 65 74 71 H.sub.2O.sub.2 (%) PC/HQ mole ratio 0.78 0.77 0.89 0.83 0.71 0.70

[0132] The results show that the catalytic performance of the materials crystallized after the maturation step are markedly better than those of the materials crystallized without maturation. Specifically, from a kinetic point of view, 15 minutes after the end of addition of the aqueous hydrogen peroxide solution (T.sub.0+15 min), an H.sub.2O.sub.2 conversion of 84% for a matured TS-1 prepared according to protocol A (example 1.3) is observed, whereas it is only 65% for the material synthesized according to the same protocol but without the maturation step (example 1.7). Furthermore, for an equivalent conversion of hydrogen peroxide (about 80%), this same material has a selectivity toward PC+HQ relative to hydrogen peroxide of 83% (example 1.3), whereas it is only 69% for its non-matured homolog (example 1.7). The same observations may be made with all of the TS-1 products synthesized according to the other protocols. Furthermore, it is observed, independently of the synthetic protocol, that a PC/HQ mole ratio close to 0.60 is obtained for the TS-1 products matured for 14 hours at 80 C.

Example 2

Effect of the Maturation Step on the Structure of the TS-1

[0133] Zeolites were prepared according to process A (example 2.1), process D (example 2.2), process C (example 2.3) and process B (example 2.4) with a maturation step at 80 C. for 4.5 to 48 hours or without a maturation step. All the zeolites prepared underwent a step of crystallization at 175 C. for 5 days and a step of calcination at 550 C. for 3 hours.

[0134] The size of the crystallites was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) after the maturation, crystallization and calcination steps. The size of the crystallites was also determined by dynamic light scattering (DLS) using synthetic aqueous solutions (i.e. solutions obtained after maturation, after crystallization and before calcination of the materials) diluted from 10 to 400 times in demineralized water and/or treated with ultrasound for 1 to 10 minutes, but also using solutions obtained after dispersion of 50 to 100 mg of matured, crystallized and calcined catalyst in 10 g of demineralized water, and treated with ultrasound for 15 minutes. The outer surface area and the inter-grain distance were determined by adsorption/desorption of nitrogen. The results are presented in table 3.

TABLE-US-00003 TABLE 3 DLS XRD Size after Size after Apparent maturation maturation, Nitrogen mean size and crystal- adsorption/ of the crystallization lization Population desorption crystallites and before and (% of the TEM S.sub.outer D.sub.inter-grain Exam- Matu- (line 101) calcination calcination number of Crystallite (m.sup.2/g) (nm) ples ration (nm) (nm) (nm) crystallites) size (nm) [tplot] [BJH] 2.1 None 80 90-160 39 50 20 4.5 h/ 67 71 71 94 50-110 63 22 7 80 C. 14 h/ 55 59 97 30-90 79 19 5 80 C. 23 h/ 56 56 54 97 30-90 83 16 6 80 C. 48 h/ 55 51 51 98 40-90 82 21 7 80 C. 2.2 None 95 33 40 15 14 h/ 50 72 19 5 80 C. 2.3 None 110 22 60 20 14 h/ 68 60 30 10 80 C. 2.4 14 h/ 55 79 19 6 80 C.

[0135] The main characteristic of the materials matured at 80 C. is that the apparent mean size of the particles is about 1.5 to 2 times smaller than that of the non-matured materials (size determined after OLS analysis, observation by TEM and calculated after XRD analysis from the mid-height width of the line (101)). Furthermore, irrespective of the synthetic protocol, it is observed that TS-1 particles of 50 to 70 nm are obtained if the zeolite has undergone a maturation step, irrespective of the maturation time at 80 C. Since the particles are smaller after maturation, the space between the grains (D.sub.inter-grain determined via the BJH method) is consequently smaller. Furthermore, the zeolites matured for 4.5 to 48 hours at 80 C. have an outer surface area about twice as large as that of the non-matured materials. From the DLS, irrespective of the synthetic protocol and the maturation time at 80 C., the size of the crystallites obtained after the maturation and crystallization steps and before the calcination step is similar, or even identical, to the size of the crystallites obtained after the maturation, crystallization and calcination steps.

Example 3

Effect of the Maturation Time and Temperature on the Catalytic Performance of TS-1 in the Phenol Hydroxylation Reaction

[0136] The hydroxylation reaction presented above was performed with different zeolites prepared according to protocol A which have undergone a maturation step at 80 C. for 4.5 hours (example 3.2), for 14 hours (example 3.3), for 23 hours (example 3.4) and for 48 hours (example 3.5) and at 90 C. for 14 hours (example 3.6) and for 23 hours (example 3.7).

[0137] A comparative example (example 3.1) of hydroxylation of phenol was also performed with a zeolite obtained via process A, but which was not subjected to the maturation step.

[0138] All the zeolites prepared underwent a step of crystallization at 175 C. for 5 days and a step of calcination at 550 C. for 3 hours.

[0139] Samples were collected from the reaction medium 15 and 60 minutes after the end of the addition of H.sub.2O.sub.2. The results are presented in table 4.

TABLE-US-00004 TABLE 4 Examples Sample 3.1 3.2 3.3 3.4 3.5 3.6 3.7 collection Maturation (T.sub.0 = 2 h = 4.5 h/ 14 h/ 23 h/ 48 h/ 14 h/ 23 h/ addition None 80 C. 80 C. 80 C. 80 C. 90 C. 90 C. time of T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + H.sub.2O.sub.2) 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min 15 min 60 min DC(H.sub.2O.sub.2) 65 80 80 94 84 98 93 99 65 82 78 95 83 98 (%) RY(HQ)/ 24 28 32 40 43 46 47 49 28 34 36 41 36 37 H.sub.2O.sub.2 (%) RY(PC)/ 21 23 23 28 27 29 29 30 20 24 24 27 24 24 H.sub.2O.sub.2 (%) RY(HQ + 45 52 55 68 70 75 77 78 48 58 60 68 59 61 PC)/ H.sub.2O.sub.2 (%) CY(HQ + 69 65 69 72 83 76 83 79 74 71 77 72 71 63 PC)/ H.sub.2O.sub.2 (%) PC/HQ 0.89 0.83 0.69 0.69 0.64 0.63 0.62 0.60 0.71 0.69 0.68 0.65 0.66 0.65 mole ratio

[0140] It is noted that it is possible to vary the selectivity toward hydroquinone and pyrocatechol relative to hydrogen peroxide (CY(HQ+PC)/H.sub.2O.sub.2) which ranges between 60% and 85% by modifying the maturation temperature of between 80 and 90 C. and the maturation time of between 4.5 and 48 hours. On the other hand, irrespective of the matured catalysts, the PC/HQ mole ratios are similar or even identical and strictly less than 0.70.

Example 4

Effect of the Crystallization Time on the Catalytic Performance of Matured TS-1 in the Phenol Hydroxylation Reaction

[0141] The hydroxylation reaction presented above was performed with different zeolites prepared according to protocol A which have undergone a step of maturation at 80 C. for 14 hours and a step of crystallization at 175 C. for 6 hours (example 4.1), for 24 hours (example 4.2) and for 5 days (example 4.3). All the zeolites were calcined at 550 C. for 3 hours.

[0142] Samples were collected from the reaction medium 15 and 60 minutes after the end of the addition of H.sub.2O.sub.2. The results are presented in table 5.

TABLE-US-00005 TABLE 5 Examples 4.1 4.2 4.3 Crystallization Sample collection 6 h/175 C. 24 h/175 C. 5 days/175 C. (T.sub.0 = 2 h = T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + addition time of 15 60 15 60 15 60 H.sub.2O.sub.2) min min min min min min DC(H.sub.2O.sub.2) (%) 84 98 95 99 84 98 RY(HQ)/H.sub.2O.sub.2 (%) 43 46 44 48 43 46 RY(PC)/H.sub.2O.sub.2 (%) 27 28 28 29 27 29 RY(HQ + PC)/ 70 74 72 77 70 75 H.sub.2O.sub.2 (%) CY(HQ + PC)/ 84 75 76 78 83 76 H.sub.2O.sub.2 (%) PC/HQ mole ratio 0.64 0.61 0.62 0.61 0.64 0.63

[0143] The results show that after maturation for 14 hours at 80 C., the crystallization time at 175 C. may be lowered to 6 hours without modifying the catalytic performance of the TS-1. Specifically, at virtually total conversion of the hydrogen peroxide, the CY(HQ+PC)/H.sub.2O.sub.2 values are very similar and, respectively, 75%, 78% and 76% for crystallizations times at 175 C. of 6 hours, 24 hours and 5 days. Finally, irrespective of the crystallization time at 175 C., the PC/HQ mole ratio is 0.60.

Example 5

Effect of the Crystallization Time on the Characteristics of the TS-1

[0144] Different zeolites prepared according to protocol A underwent a step of maturation at 80 C. for 14 hours and a step of crystallization at 175 C. for 6 hours (example 5.1), for 24 hours (example 5.2) and for 5 days (example 5.3). All the zeolites were calcined at 550 C. for 3 hours.

[0145] The size of the crystallites was determined by XRD and DLS. The results are presented in table 6.

TABLE-US-00006 TABLE 6 XRD Apparent DLS mean size Population Ti/ of the (% of the (Ti + Si) crystallites number of molar (line 101) Size crystal- Examples Crystallization (0.001) (nm) (nm) lites) 5.1 6 h/175 C. 0.013 49 5.2 24 h/175 C. 0.016 53 54 93 5.3 5 days/175 C..sup. 0.020 55 59 97

[0146] The results show that the size of the crystallites, of about 50 nm, does not depend on the crystallization time at 175 C. for materials matured beforehand for 14 hours at 80 C. On the other hand, it is observed that the titanium content of the material increases as the crystallization time increases. The mole ratio Ti/(Ti+Si) is, respectively, 0.013, 0.016 and 0.020 for crystallization times at 175 C. of 6 hours, 24 hours and 5 days. The increase in titanium content of 0.013 to 0.016 and 0.020 corresponds to the increasingly large formation of anatase, as evidenced in FIG. 8.

Example 6

Effect of the Nature of the Solvent in the Phenol Hydroxylation Reaction in the Presence of a Catalyst of the titano-silicalite Zeolite Type

[0147] The hydroxylation reaction presented above was performed with different solvents or a mixture of solvents such as water (example 6.1), water/acetone (example 6.2) and water/methanol (example 6.3).

[0148] The zeolite used for the phenol hydroxylation reaction was prepared according to protocol A and was first subjected to a step of maturation at 80 C. for 23 hours, and then a step of crystallization at 175 C. for 5 days, and finally a step of calcination at 550 C. for 3 hours.

[0149] Samples were collected from the reaction medium 15, 60 or 120 minutes after the end of the addition of H.sub.2O.sub.2. The results are presented in the table below.

TABLE-US-00007 Examples 6.1 6.2 6.3 Sample collection Solvent (T.sub.0 = 2 h = Water Water/acetone Water/methanol addition time of T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + T.sub.0 + H.sub.2O.sub.2) 15 min 60 min 15 min 60 min 120 min 15 min 60 min 120 min DC(H.sub.2O.sub.2) (%) 93 99 67 84 97 70 90 98 RY(HQ)/H.sub.2O.sub.2 (%) 47 49 27 32 35 32 36 37 RY(PC)/H.sub.2O.sub.2 (%) 29 30 26 30 33 22 25 25 RY(HQ + PC)/ 77 78 52 62 68 54 60 62 H.sub.2O.sub.2 (%) CY(HQ + PC)/ 83 79 79 74 70 77 67 63 H.sub.2O.sub.2 (%) PC/HQ mole ratio 0.62 0.60 0.96 0.95 0.94 0.69 0.69 0.69

[0150] The results show that the best solvent for the hydroxylation of phenol is water used alone. Specifically, from a kinetic point of view, 60 minutes after the end of addition of the hydrogen peroxide (T.sub.0+60 min), a total conversion of the hydrogen peroxide is observed for the hydroxylation of phenol in water, whereas it is only 84% and 90% for the hydroxylation of phenol, respectively, in water/acetone and water/methanol. Furthermore, for an equivalent conversion of hydrogen peroxide (about 100%), the hydroxylation of phenol in water leads to a selectivity toward PC+HQ relative to the hydrogen peroxide of 79%, which is higher than that obtained for the hydroxylation of phenol in the water/acetone and water/methanol mixtures, which are, respectively, 70% and 63%. Finally, the lower PC/HQ ratio was obtained for the hydroxylation of phenol in water (PC/HQ=0.60). This is, respectively, 0.94 and 0.69 for the hydroxylation of phenol in the water/acetone and water/methanol solvent mixtures.