Method for Depolymerising Oxygenated Polymer Materials

Abstract

The present invention concerns a method for depolymerizing oxygenated polymer materials and the use of said method in the recycling of plastic materials and the preparation of aromatic compounds that can be used as fuel, synthesis intermediates and raw materials in the construction sectors and in the petrochemical, electrical, electronic, textile, aeronautical, pharmaceutical, cosmetics and agrochemical industries. The present invention also concerns the use of aromatic compounds obtained by the method for depolymerizing oxygenated polymer materials according to the invention, in the production of fuels, electronic components, plastic polymers, rubber, drugs, vitamins, cosmetic products, perfumes, food products, synthetic threads and fibres, synthetic leathers, glues, pesticides and fertilizers.

Claims

1. A process for depolymerizing oxygenated polymer materials by selective cleavage of the oxygen-carbonyl bonds of the ester functions and of the carbonate functions, characterized in that it comprises a step of placing said oxygenated polymer materials in contact with a silane compound of formula (I) ##STR00034## in which R.sup.1, R.sup.2 and R.sup.3 represent, independently of each other, a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, a silyl group, a siloxy group, an aryl group, an amino group, said alkyl, alkenyl, alkynyl, alkoxy, silyl, siloxy, aryl and amino groups being optionally substituted, or R.sup.1 is as defined above and R.sup.2 and R.sup.3, taken together with the silicon atom to which they are linked, form an optionally substituted silyl heterocycle; in the presence of a catalyst which is: an organic catalyst chosen from the carbocations of formula (X.sup.1).sub.3C.sup.+ with X.sup.1 representing a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a silyl group, a siloxy group and a halogen atom; oxoniums chosen from (CH.sub.3).sub.3O.sup.+BF.sub.4.sup.− and (CH.sub.3CH.sub.2).sub.3O.sup.+BF.sub.4.sup.−; a silylium ion (R.sup.5).sub.3Si.sup.+ with R.sup.5 representing, independently of each other, a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocycle, a silyl group, a siloxy group; disilyl cations; with the anionic counterion of said silylium ion, of said carbocations and of said disilyl cations being a halide chosen from F.sup.−, Cl.sup.−, Br.sup.− and I.sup.−; or an anion chosen from BF.sub.4.sup.−, SbF.sub.6.sup.−, B(C.sub.6F.sub.5).sub.4.sup.−, B(C.sub.6H.sub.5).sub.4.sup.−, CF.sub.3SO.sub.3.sup.−, PF.sub.6.sup.−; or an organometallic catalyst.

2. The process as claimed in claim 1, characterized in that the oxygenated polymers are chosen from saturated or unsaturated polyesters chosen from polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (P3HB), polyhydroxyvalerate (PHV), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polycarbonates chosen from PC-BPA, polypropylene carbonate (PPC), polyethylene carbonate (PEC), poly(hexamethylene carbonate), allyl diglycol carbonate (ADC) or CR-39, hydrolyzable tannins, especially gallotannins and ellagitannins, and suberin.

3. The process as claimed in claim 1, characterized in that the oxygenated polymers are chosen from PET and PLA; PC-BPA; gallotannins and ellagitannins, and suberin.

4. The process as claimed in claim 1, characterized in that the catalyst is an organic catalyst chosen from: carbocations chosen from the trityl cation ((C.sub.6H.sub.5).sub.3C.sup.+), tropilium (C.sub.7H.sub.7).sup.+, the benzilic cation (C.sub.6H.sub.5CH.sub.2.sup.+), the allylic cation (CH.sub.3—CH.sup.+—CH═CH.sub.2), methylium (CH.sub.3.sup.+), cyclopropylium (C.sub.3H.sub.5.sup.+), the cyclopropyl carbocation chosen from the dimethylcyclopropyl carbocation and the dicyclopropyl carbocation, the triazabicyclodecene (TBD) cation, acylium (R.sup.1—C═O).sup.+ with R.sup.1 as defined above and chosen from methyl, propyl and benzyl, benzenium (C.sub.6H.sub.5).sup.+, and the norbornyl cation (C.sub.7H.sub.11).sup.+; oxoniums chosen from (CH.sub.3).sub.3O.sup.+BF.sub.4.sup.− and (CH.sub.3CH.sub.2).sub.3O.sup.+BF.sub.4.sup.−; a silylium ion chosen from Et.sub.3Si.sup.+ and Me.sub.3Si.sup.+; disilyl cations bearing a bridging hydride chosen from the formulae indicated below ##STR00035## with the anionic counterion of said silylium ion, of said carbocations and of said disilyl cations being a halide chosen from F.sup.−, Cl.sup.−, Br.sup.− and I.sup.−; or an anion chosen from BF.sub.4.sup.−, SbF.sub.6.sup.−, B(C.sub.6F.sub.5).sub.4.sup.−, B(C.sub.6H.sub.5).sub.4.sup.−, CF.sub.3SO.sub.3.sup.−, PF.sub.6.sup.−.

5. The process as claimed in claim 4, characterized in that the organic catalyst is chosen from triphenylcarbenium tetrakis(perfluorophenyl)borate [(Ph).sub.3C.sup.+B(C.sub.6F.sub.5).sub.4].sup.−.

6. The process as claimed in claim 1, characterized in that the catalyst is an organometallic catalyst chosen from: the iridium complexes of formula (II): ##STR00036## in which R.sup.6 represents an alkyl or aryl group; R.sup.7 represents a hydrogen atom or an alkyl group; X.sup.2 represents a —CH.sub.2— group or an oxygen atom; Y.sup.− represents a counterion chosen from B(C.sub.6F.sub.5).sub.4.sup.− and B(C.sub.6H.sub.5).sub.4; and S represents a solvent molecule, coordinated to the complex, chosen from dimethyl sulfoxide (DMSO), acetonitrile (CH.sub.3CN) and acetone (CH.sub.3COCH.sub.3); and the ruthenium complexes of formula (III): ##STR00037## in which R.sup.8 represents a hydrogen atom or an alkyl group; R.sup.9 represents an aryl or an alkyl group, said aryl and alkyl groups being optionally substituted; Z represents a —CH.sub.2— group, an oxygen atom or a sulfur atom; and A.sup.− represents a counterion chosen from B(C.sub.6F.sub.5).sub.4.sup.− and [CHB.sub.11H.sub.5Cl.sub.6].sup.−.

7. The process as claimed in claim 6, characterized in that the organometallic catalyst is chosen from: the iridium complex [(POCOP)Ir(H)(acetone)].sup.+B(C.sub.6F.sub.5).sub.4.sup.− with (POCOP) representing 2,6-bis(di-tert-butylphosphinito)phenyl; and the ruthenium complex of formula (III) in which R.sup.8 represents a methyl group; R.sup.9 represents p-FC.sub.6H.sub.4; Z represents a sulfur atom; and A.sup.− represents B(C.sub.6F.sub.5).sub.4.sup.−.

8. The process as claimed in claim 1, characterized in that the catalyst is a catalyst of Lewis acid type chosen from: the boron compound chosen from BF.sub.3, BF.sub.3(Et.sub.2O), BCl.sub.3, BBr.sub.3, triphenylhydroborane, tricyclohexylhydroborane, B(C.sub.6F.sub.5).sub.3, B-methoxy-9-borabicyclo[3.3.1]nonane (B-methoxy-9-BBN), B-benzyl-9-borabicyclo[3.3.1]nonane (B-benzyl-9-BBN); the borenium compound Me-TBD-BBN.sup.+, the borenium ferrocene derivatives corresponding to the formula ##STR00038## in which R.sup.10=phenyl and R.sup.11=3,5-dimethylpyridyl; aluminum compounds chosen from AlCl.sub.3, AlBr.sub.3, aluminum isopropoxide (Al(O-i-Pr).sub.3), aluminum ethoxide (Al(C.sub.2H.sub.3O.sub.2)), Krossing's salt [Ag(CH.sub.2Cl.sub.2)]{Al[OC(CF.sub.3).sub.3].sub.4}, the Li{Al[OC(CF.sub.3).sub.3].sub.4}, Et.sub.2Al.sup.+; indium compounds chosen from InCl.sub.3, In(OTf).sub.3; iron compounds chosen from FeCl.sub.3, Fe(OTf).sub.3; tin compounds chosen from SnCl.sub.4, Sn(OTf).sub.2; phosphorus compounds chosen from PCl.sub.3, PCl.sub.5, POCl.sub.3; trifluoromethanesulfonate or triflate compounds (CF.sub.3SO.sub.3.sup.−) of transition metals and of lanthanides chosen from scandium triflate, ytterbium triflate, yttrium triflate, cerium triflate, samarium triflate and neodymium triflate.

9. The process as claimed in claim 8, characterized in that the catalyst of Lewis acid type is chosen from BF.sub.3; InCl.sub.3; the borenium ferrocene derivative in which R.sup.10=phenyl and R.sup.11=3,5-dimethylpyridyl.

10. The process as claimed in claim 1, characterized in that the silane compound used is a silane compound of formula (I) in which R.sup.1, R.sup.2 and R.sup.3 represent, independently of each other, a hydrogen atom, a hydroxyl group; an alkyl group chosen from methyl, ethyl, propyl, butyl, and branched isomers thereof; an alkoxy group whose alkyl radical is chosen from methyl, ethyl, propyl, butyl and branched isomers thereof; an aryl group chosen from phenyl and benzyl; an aryloxy group whose aryl radical is chosen from phenyl and benzyl; a siloxy group (—O—Si(X).sub.3) in which each X, independently of each other, is chosen from a hydrogen atom, an alkyl group chosen from methyl, ethyl, propyl, an aryl group chosen from phenyl and benzyl, a polymeric organosilane of general formula ##STR00039## in which X is as defined above and n is an integer between 1 and 20 000, advantageously between 1 and 5000, more advantageously between 1 and 1000; said alkyl, alkoxy, aryl, aryloxy, siloxy and aryl groups being optionally substituted.

11. The process as claimed in claim 1, characterized in that the silane compound used is a silane compound of formula (I) in which R.sup.1, R.sup.2 and R.sup.3 represent, independently of each other, a hydrogen atom; an alkyl group chosen from methyl, ethyl, propyl and the branched isomer thereof; an aryl group chosen from benzyl and phenyl; a siloxy group chosen from polydimethylsiloxane (PDMS), polymethylhydroxysiloxane (PMHS) and tetramethyldisiloxane (TMDS).

12. The process as claimed in claim 1, characterized in that the depolymerization is performed at a pressure of one or a mixture of inert gases chosen from nitrogen and argon, or of gases generated by the process, especially methane and hydrogen.

13. The process as claimed in claim 12, characterized in that the pressure is between 0.2 and 50 bar, limits inclusive.

14. The process as claimed in claim 1, characterized in that the depolymerization is performed at a temperature of between 0 and 150° C., limits inclusive.

15. The process as claimed in claim 1, characterized in that the depolymerization is performed in one or a mixture of at least two solvents chosen from: silyl ethers chosen from 1,1,1,3,3,3-hexamethyldisiloxane ((Me.sub.3Si).sub.2O), 1,1,1,3,3,3-hexaethyldisiloxane ((Et.sub.3Si).sub.2O); hydrocarbons chosen from benzene, toluene, pentane and hexane; sulfoxides chosen from dimethyl sulfoxide (DMSO); alkyl halides chosen from chloroform, methylene chloride, chlorobenzene, dichlorobenzene.

16. The process as claimed in claim 1, characterized in that the mol ratio between the silane compound of formula (I) and the oxygenated polymer material is between 0.1 and 20, limits inclusive.

17. The process as claimed in claim 1, characterized in that the amount of catalyst is from 0.001 to 1 molar equivalent, limits inclusive, relative to the initial number of mols of the oxygenated polymer material.

18. A process for recycling plastic materials or mixtures of plastic materials containing at least one oxygenated polymer, characterized in that it comprises a step of depolymerizing oxygenated polymer materials as claimed in claim 1.

19. A process for preparing mono-, di- and/or tricyclic aromatic compounds in which each ring is optionally mono-, di- and/or trioxygenated, characterized in that it comprises a step of depolymerizing oxygenated polymer materials as claimed in claim 1.

Description

[0154] Other advantages and characteristics of the present invention will emerge on reading the examples below, which are given as nonlimiting illustrations, and of the attached figures, in which:

[0155] FIG. 1 represents the process for depolymerizing the oxygenated polymer materials according to the invention. A and B represent two identical or different groups chosen from one or more optionally substituted alkyl groups, one or more optionally substituted alkenyl groups, one or more optionally substituted alkynyl groups, one or more optionally substituted aryl groups, one or more optionally substituted heteroaryl groups, with the alkyl, alkenyl, alkynyl, aryl and heteroaryl groups as defined in the context of the present invention. n is an integer between 1 and 20 000.

[0156] FIG. 2 represents the process of depolymerization of the invention for a few oxygenated polymer materials.

[0157] FIG. 3 represents the structure of suberin.

[0158] FIG. 4 represents the structure of tannic acid, also known as β-1,2,2,3,6-pentagalloyl-O-D-glucose, and belonging to the category of gallotannins.

EXAMPLES

[0159] The catalytic depolymerization reactions of oxygenated polymer materials according to the invention are presented in FIGS. 1 and 2.

[0160] In the examples below, the oxygenated polymers tested are PEG, PET, PC-BPA and PLA. Moreover, the amount of hydrosilane of general formula (I) required to perform the depolymerization is largely dependent on the type of polymer material used and also on the desired compound. Specifically, compounds containing silyl alcohol functions (C—O—SiR.sub.1R.sub.2R.sub.3) derived from the depolymerization reaction may be deoxygenated via the same process to lead to C—H bonds.

[0161] It should be noted that, by approximation, and so as to calculate the molar yield of the depolymerization reactions, the starting material is considered to consist exclusively of the polymer studied.

[0162] The yields obtained are of the order of 30 to 99 mol % relative to the number of mols of starting oxygenated polymer. The conversions were calculated on the basis of the spectroscopic analyses (.sup.1H NMR .sup.13C NMR) using a Brüker DPX 200 MHz spectrometer and via the addition of an internal standard (mesitylene or diphenylmethane). The yields were obtained by means of gas chromatography using as standard the same compound synthesized beforehand (external calibration curve). The mass spectrometry data were acquired on a Shimadzu GCMS-QP2010 Ultra gas chromatograph mass spectrometer machine equipped with a Supelco SLB™-ms molten silica capillary column (30 m×0.25 mm×0.25 μm). The qualitative gas analyses were performed by means of gas chromatography on a Shimadzu GC-2010 machine equipped with a Carboxen™ 1006 PLOT capillary column (30 m×0.53 mm).

General Depolymerization Experimental Protocol

[0163] 1. Under an inert atmosphere of argon or nitrogen, the hydrosilane of general formula (I), the catalyst (from 1 to 0.001 molar equivalent calculated relative to the number of mols of polymer material initially added) and half the amount of solvent are stirred in a glass container of suitable volume. The concentration of silane in the reaction mixture ranges from 1.0-6.0 mol.Math.L.sup.−1 (concentration calculated on the basis of half the final volume of solvent introduced). [0164] 2. Separately, in a Schlenk tube, the oxygenated polymer material (used as received) is stirred with the remaining half of the solvent. [0165] 3. The solution containing the catalyst and the hydrosilane is added slowly (addition time of 5 minutes to 1 hour) by means of a syringe and with stirring, to the Schlenk tube. This tube is left open so as to evacuate the gases produced by the reaction. [0166] 4. After the end of addition of the solution and once the evolution of gas has stopped, the Schlenk tube is closed and left stirring. In the case where the starting material is insoluble, the dissolution takes place during the reaction time given that the final products are soluble in the solvents used. Monitoring of the reaction is performed by .sup.1H NMR and by GC-MS. [0167] 5. Once the reaction is complete (reaction time of 1 minute to 24 hours), the solvent and the volatile compounds are evaporated off by means of a vacuum ramp (10.sup.−2 mbar). The oil obtained is purified by means of chromatography on silica gel, using an elution gradient from 100:0% to 0:100% of pentane: CH.sub.2Cl.sub.2. It should be noted that the liquid products which have low boiling points, such as para-xylene, may be purified by fractional distillation with recycling of the solvent. [0168] 6. In the case of products bearing siloxy functions (—SiOR.sub.1R.sub.2R.sub.3), these products are hydrolyzed using TBAF.3H.sub.2O, to give the corresponding hydrolyzed product. The hydrolysis reaction lasts from 1 minute to 16 hours. The final product is obtained after purification on a chromatography column using an elution gradient from 100:0% to 0:100% of CH.sub.2Cl.sub.2:EtOAc.

[0169] A set of results is presented below, giving examples of depolymerization of synthetic and biosourced oxygenated polymer materials.

[0170] The catalysts tested are B(C.sub.6F.sub.5).sub.3, (Ph.sub.3)C.sup.+B(C.sub.6F.sub.5).sub.3.sup.− and also the iridium complex ([(POCOP)Ir(H)(acetone)].sup.+B(C.sub.6F.sub.5).sub.4.sup.−).

[0171] The hydrosilanes used are Et.sub.3SiH, TMDS and PMHS. The oxygenated polymer materials used are PLA, PEG, PC-BPA, PET, suberin and tannic acid. Suberin is obtained from cork stoppers used in commercial wine bottles. The tannic acid used is extracted from Chinese gall nut extracts. The PET used is a commercial PET taken from Perrier bottles.

A) Depolymerization of Oxygenated Polymers in Presence of B(C.sub.6F.sub.5).sub.3

Example 1: Depolymerization of PC-BPA with Triethylsilane (Et.SUB.3.SiH)

[0172] ##STR00013##

[0173] Commercial PC-BPA (123.2 mg, 0.5 mmol, 1 equiv.) was added to 1.5 mL of CH.sub.2Cl.sub.2. Separately, B(C.sub.6F.sub.5).sub.3 (5.1 mg, 0.01 mmol, 2 mol %) is dissolved in a mixture of triethylsilane (244.2 mg, 2.1 mmol, 4.2 equiv.) and 1.5 mL of CH.sub.2Cl.sub.2. Next, the solution containing the hydrosilane and the catalyst is added slowly to the solution containing the polymer stirred beforehand. After reaction for 3 hours at room temperature (20±5° C.), the solvent is evaporated off under vacuum. The product obtained IId is purified using the same conditions as that described in the general procedure. On conclusion of this purification, product IId is obtained in high purity in a yield of 77% relative to the starting material introduced. Finally, the hydrolysis of product IId is performed with stirring at 25° C. for 2 hours in a solution of TBAF.3H.sub.2O (2.1 equiv. relative to the number of mols of IId) in THF (3 mL). The hydrolyzed product (BPA) is obtained in quantitative yield, in the form of a white solid, after purification on a chromatography column using the conditions described in the general procedure.

Example 2: Depolymerization of PET Using Triethylsilane (Et.SUB.3.SiH)

[0174] ##STR00014##

[0175] The same procedure using for the depolymerization of PC-BPA with Et.sub.3SiH is used for the depolymerization of PET. In this case, (96.1 mg, 0.5 mmol, 1 equiv.) of PET are used with (244.2 mg, 2.1 mmol, 4.2 equiv.) of triethylsilane and (5 mg, 0.01 mmol, 2 mol %) of B(C.sub.6F.sub.5).sub.3. After reaction for 3 hours at room temperature (20±5° C.), the conversion is total into IIa and IIc. Purification of the products is performed according to the same procedure described in example 1. Hydrolysis of these compounds under the conditions of example 1 leads to the production of ethylene glycol (colorless oil, 72% yield) and 1,4-phenylenedimethanol (white solid, 85% yield).

Example 3: Depolymerization of PET with Polymethylhydrosiloxane (PMHS)

[0176] ##STR00015##

[0177] The same procedure as that of example 2 is used for the depolymerization of PET with PMHS. However, the products obtained are ethane and paraxylene. In this case, 96.1 mg (0.5 mmol, 1 equiv.) of PET are used with 330.7 mg (5.5 mmol, 11 equiv.) of PMHS, 19.2 mg (0.04 mmol, 7.5 mol %) of B(C.sub.6F.sub.5).sub.3 and 6 mL of CH.sub.2Cl.sub.2. After reaction for 16 hours, the yield of paraxylene obtained is 75%.

Example 4: Depolymerization of PET with Tetramethyldisiloxane (TMDS)

[0178] ##STR00016##

[0179] The same procedure as that of example 3 is used for the depolymerization of PET with TMDS. The products obtained are ethane and paraxylene. 96.1 mg (0.5 mmol, 1 equiv.) of PET were used with 400.0 mg (3.0 mmol, 6 equiv.) of TMDS, 12.8 mg (0.025 mmol, 5 mol %) of B(C.sub.6F.sub.5).sub.3 and 3 mL of CH.sub.2Cl.sub.2. After reaction for 16 hours, the conversion is total and the yield of paraxylene obtained is 82%.

Example 5: Depolymerization of PLA Using Triethylsilane (Et.SUB.3.SiH)

[0180] ##STR00017##

[0181] The same procedure as that of example 2 is used for the depolymerization of PLA with Et.sub.3SiH. Product IIb is obtained. In this case, 360.3 mg (0.5 mmol, 1 equiv.) of PLA are used with 191.9 mg (1.7 mmol, 3.3 equiv.) of Et.sub.3SiH, 12.8 mg (0.025 mmol, 5 mol %) of B(C.sub.6F.sub.5).sub.3 and 3 mL of CH.sub.2Cl.sub.2. After reaction for 3 hours, the yield of product IIb is 65%.

Example 6: Depolymerization of PLA with Polymethylhydrosiloxane (PMHS)

[0182] ##STR00018##

[0183] The same procedure as that of example 5 is used for the depolymerization of PLA with PMHS. The product obtained is propane and the solvent used is benzene. In this case, 360.3 mg (0.5 mmol, 1 equiv.) of PLA are used with 120.3 mg (2.0 mmol, 4 equiv.) of PMHS, 5.1 mg (0.01 mmol, 2 mol %) of B(C.sub.6F.sub.5).sub.3 and 3 mL of benzene. After reaction for 16 hours, the conversion is 56%.

[0184] It should be noted that the use of CH.sub.2Cl.sub.2 as reaction solvent leads to the direct formation of a gel.

Example 7: Depolymerization of PLA with Tetramethyldisiloxane (TMDS)

[0185] ##STR00019##

[0186] The same procedure as that of example 6 is used for the depolymerization of PLA with TMDS. The reaction takes place in CH.sub.2Cl.sub.2. In this case, 360.3 mg (0.5 mmol, 1 equiv.) of PLA are used with 133.3 mg (1.0 mmol, 2 equiv.) of TMDS, 5.1 mg (0.01 mmol, 2 mol %) of B(C.sub.6F.sub.5).sub.3 and 3 mL of CH.sub.2Cl.sub.2. After 1 hour of reaction, the conversion is >99%.

Example 8: Depolymerization of Gallotannin with Triethylsilane (Et.SUB.3.SiH)

[0187] ##STR00020##

[0188] The same procedure as that of example 1 is used for the depolymerization of tannic acid with triethylsilane. In this case, 170.1 mg (0.1 mmol, 1 equiv.) of tannic acid (C.sub.76H.sub.52O.sub.46) are used with 930.2 mg (8.0 mmol, 80 equiv.) of Et.sub.3SiH, 15.4 mg (0.03 mmol, 30 mol %) of B(C.sub.6F.sub.5).sub.3 and 3 mL of CH.sub.2Cl.sub.2 (conditions not optimized). After 16 hours of reaction, the molar yield of product IIe is 132%, i.e. 0.13 mmol. Purification of the product is performed using the same conditions as that described in the general procedure.

[0189] It should be noted that the hydrolysis of the product is performed under conditions virtually similar to those described in the general procedure. Specifically, this last step must be performed under an inert atmosphere of argon or nitrogen, given that the product 5-methylbenzene-1,2,3-triol oxidizes directly to quinone in the presence of oxygen.

Example 9: Depolymerization of a PET+PS Mixture with Triethylsilane (Et.SUB.3.SiH)

[0190] ##STR00021##

[0191] The same procedure as that of example 2 is used for the depolymerization of the PET+PS mixture. In this case, 96.1 mg (0.5 mmol, 1 equiv.) of PET are used with 52.1 mg (0.5 mmol, 1 equiv.) of PS (commercial expanded polystyrene), 290.7 mg (2.5 mmol, 5.0 equiv.) of triethylsilane and 12.8 mg (0.03 mmol, 5 mol %) of B(C.sub.6F.sub.5).sub.3 in 3 mL of CH.sub.2Cl.sub.2. After reaction for 3 hours, the conversion is total into the products IIa and IIc, PS not having undergone any depolymerization under these conditions. Purification of the products is performed by following the same procedure as that described in example 2. Hydrolysis of these compounds leads to the production of ethylene glycol and 1,4-phenylenedimethanol.

Example 10: Depolymerization of a PET+PVC+PS Mixture with Triethylsilane (Et.SUB.3.SiH)

[0192] ##STR00022##

[0193] The same procedure as that of example 9 is used for the depolymerization of the PET+PS+PVC mixture. The same amounts of PET and PS are used and 31.3 mg (0.5 mmol, 1 equiv.) of PVC (derived from plumbing pipes) are used in the reaction. Only PET is selectively depolymerized, whereas PVC and PS are not depolymerized under these conditions.

Example 11: Selective Depolymerization of PET in a PET+PLA Mixture with Triethylsilane (Et.SUB.3.SiH)

[0194] ##STR00023##

[0195] The same procedure as that of example 10 is used for the depolymerization of the PET+PLA mixture. In this case, 96.1 mg (0.5 mmol, 1 equiv.) of PET are used with 360.3 mg (0.5 mmol, 1 equiv.) of PLA, 244.2 mg (2.1 mmol, 4.2 equiv.) of triethylsilane and 5.1 mg (0.01 mmol, 2 mol %) of B(C.sub.6F.sub.5).sub.3 in 3 mL of CH.sub.2Cl.sub.2. After reaction for 3 hours, products IIa and IIc are obtained. No product derived from the depolymerization of PLA is observed. Purification of the products takes place by following the same procedure as that described in example 2. Hydrolysis of these compounds leads to the production of ethylene glycol and 1,4-phenylenedimethanol.

Example 12: Depolymerization of a PET+PLA Mixture with Triethylsilane (Et.SUB.3.SiH)

[0196] ##STR00024##

[0197] The same procedure as that of example 11 is used for the depolymerization of the PET+PLA mixture. However, the amount of hydrosilane used is 418.6 mg (3.6 mmol, 7.2 equiv.) and the amount of catalyst used is 25.6 mg (0.06 mmol, 10 mol %). After reaction for 16 hours, products IIa, IIb and IIc are obtained. Hydrolysis of these compounds leads to the production of ethylene glycol, 1,2-propanediol and 1,4-phenylenedimethanol.

Example 13: Depolymerization of Suberin Derived from Cork with Triethylsilane (Et.SUB.3.SiH)

[0198] ##STR00025##

[0199] In order to test the possibility of depolymerization of suberin by hydrosilylation with B(C.sub.6F.sub.5).sub.3, cork derived from wine bottle stoppers was finely ground and then dried under vacuum overnight. Next, the same procedure as that of example 1 is used for the depolymerization of suberin. In this case, 100.0 mg of cork are used with 582.4 mg (5.0 mmol, 582% by mass) of Et.sub.3SiH, 30 mg (0.59 mmol, 30% by mass) of B(C.sub.6F.sub.5).sub.3 and 3 mL of CH.sub.2Cl.sub.2 (conditions not optimized). After reaction for 16 hours at room temperature (20±5° C.), a large amount of the initially insoluble solid is dissolved. GC-MS analysis of the reaction residue shows the presence of a complex mixture of several products, among which product IIf was able to be identified and quantified at 12% by mass relative to the mass of cork initially introduced.

B) Depolymerization of Oxygenated Polymers in the Presence of (Ph.sub.3)C.sup.+B(C.sub.6F.sub.5).sub.3.sup.−

Example 14: Depolymerization of PC-BPA Using (Ph.SUB.3.)C.SUP.+.B(C.SUB.6.F.SUB.5.).SUB.3..SUP.−

[0200] ##STR00026##

[0201] The same procedure as that of example 1 is used for the depolymerization of PC-BPA using (Ph.sub.3)C.sup.+B(C.sub.6F.sub.5).sub.3.sup.−. In this case, 123.2 mg (0.5 mmol, 1 equiv.) of PC-BPA are used with 244.2 mg (2.1 mmol, 4.2 equiv.) of triethylsilane and 9.2 mg (0.01 mmol, 2 mol %) of (Ph.sub.3)C.sup.+B(C.sub.6F.sub.5).sub.3.sup.− in C.sub.6H.sub.6 (3 mL) After reaction for 16 hours, the conversion is total and IId is obtained in a yield of 47%. Purification of the products is performed following the same procedure described in example 1.

C) Depolymerization of Oxygenated Polymers in the Presence of the Iridium Catalyst ([(POCOP)Ir(H)(acetone)].sup.+B(C.sub.6F.sub.5).sub.4.sup.−)

Example 15: Depolymerization of PET Using ([(POCOP)Ir(H)(Acetone)].SUP.+.B(C.SUB.6.F.SUB.5.).SUB.4..SUP.−.)

[0202] ##STR00027##

[0203] The same procedure used for the depolymerization of PET with Et.sub.3SiH and B(C.sub.6F.sub.5).sub.3 is used for the depolymerization of PET with Et.sub.3SiH and the iridium catalyst ([(POCOP)Ir(H)(acetone)].sup.+B(C.sub.6F.sub.5).sub.4.sup.−). In this case, 96.1 mg (0.5 mmol, 1 equiv.) of PET are used with 291.1 mg (2.5 mmol, 5 equiv.) of triethylsilane, 1.5 mL of 1,2-dichlorobenzene and 13.4 mg (0.01 mmol, 2 mol %) of ([(POCOP)Ir(H)(acetone)].sup.+B(C.sub.6F.sub.5).sub.4.sup.−) After reaction for 16 hours at 60±5° C., products IIa and IIc are produced in respective yields of 32 and 53%. Purification of the products is performed by following the same procedure described in example 2.

Characterization of the Molecules Obtained

[0204] ##STR00028##

[0205] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=7.30 (4H, s, Ar—H), 4.72 (4H, s, CH.sub.2—O), 1.05-0.91 (18H, m, CH.sub.3CH.sub.2Si), 0.72-0.54 (12H, m, CH.sub.3CH.sub.2Si).

[0206] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=140.2, 126.3, 64.7, 6.9, 4.6.

[0207] MS: IE (m/z): 337 (17); 205 (20); 154 (9); 118 (11); 117 (100); 115 (30); 112 (9); 105 (12); 104 (31); 103 (12); 87 (50); 75 (12); 59 (27).

##STR00029##

[0208] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=3.81 (1H, sex, .sup.3J=6.1 Hz, Me-CH), 3.61-3.47 (1H, m, CH.sub.2—O), 3.40-3.24 (1H, m, CH.sub.2—O), 1.14 (3H, d, .sup.3J=6.1 Hz, CH-CH.sub.3), 1.04-0.88 (18H, m, CH.sub.3CH.sub.2Si), 0.70-0.51 (12H, m, CH.sub.3CH.sub.2Si).

[0209] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=69.3, 68.7, 20.9, 7.0, 6.9, 4.9, 4.5.

[0210] MS: IE (m/z): 275 (34); 217 (62); 189 (100); 161 (55); 159 (64); 133 (23); 131 (51); 115 (89); 105 (21); 95 (42); 87 (93); 81 (25); 59 (82).

##STR00030##

[0211] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=3.67 (4H, s, O-CH.sub.2), 1.05-0.87 (18H, m, CH.sub.3CH.sub.2Si), 0.70-0.52 (12H, m, CH.sub.3CH.sub.2Si).

[0212] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=64.3, 6.9, 4.5.

[0213] MS: IE (m/z): 262 (11); 261 (44); 217 (20); 190 (13); 189 (66); 161 (28); 117 (11); 115 (65); 88 (37); 87 (100); 74 (14); 59 (56); 58 (12).

##STR00031##

[0214] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=6.95 (4H, d, .sup.3J=8.6 Hz, Ar—H), 6.62 (4H, d, .sup.3J=8.6 Hz, Ar—H), 1.51 (6H, s, CH.sub.3-Cq), 0.97-0.79 (18H, m, CH.sub.3CH.sub.2Si), 0.71-0.52 (12H, m, CH.sub.3CH.sub.2Si).

[0215] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=153.3, 143.8, 127.8, 119.2, 41.4, 31.2, 6.8, 5.1.

[0216] MS: IE (m/z): 456 (13); 443 (14); 442 (37); 441 (59); 249 (22); 221 (11); 199 (17); 143 (13); 115 (15); 96 (12); 87 (100); 82 (10); 59 (52).

##STR00032##

[0217] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=6.25 (2H, s, Ar—H), 2.16 (3H, s, Ar-CH.sub.3), 1.10-0.85 (27H, m, CH.sub.3CH.sub.2Si), 0.84-0.59 (18H, m, CH.sub.3CH.sub.2Si).

[0218] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=147.9, 136.4, 129.6, 114.2, 21.3, 7.0, 6.8, 5.4, 5.2.

[0219] MS: IE (m/z): 483 (5); 310 (7); 309 (26); 147 (5); 116 (7); 115 (66); 88 (9); 87 (100); 86 (4); 60 (5); 59 (56); 58 (5); 32 (5).

##STR00033##

[0220] .sup.1H NMR (200 MHz, CDCl.sub.3, Me.sub.4Si) δ (ppm)=6.71 (1H, d, .sup.3J=8.1 Hz, Ar—H), 6.63 (1H, s, Ar—H), 6.58 (1H, d, .sup.3J=8.1 Hz, Ar—H), 2.45 (2H, t, .sup.3J=7.8 Hz, Ar-CH.sub.2), 1.57 (2H, sex, .sup.3J=7.8 Hz, CH.sub.2—CH.sub.3), 0.98 (18H, t, .sup.3J=7.9 Hz, CH.sub.3CH.sub.2Si), 0.90 (3H, t, .sup.3J=7.8 Hz, CH.sub.3CH.sub.2Si), 0.74 (12H, q, .sup.3J=7.9 Hz, CH.sub.3CH.sub.2Si).

[0221] .sup.13C NMR (50 MHz, CDCl.sub.3, Me.sub.4Si): δ (ppm)=146.5, 144.7, 136.0, 121.3, 120.9, 120.2, 37.4, 24.7, 13.9, 6.9, 5.3, 5.2.

[0222] MS: IE (m/z): 380 (9); 351 (4); 207 (8): 117 (4): 116 (11): 115 (100): 88 (7): 87 (74): 59 (45); 58 (4).

Example 16: Process for Preparing Aromatic Compounds Comprising a Step of Depolymerization of PET Using Triethylsilane (Et.SUB.3.SiH)/Recycling of a Plastic Material

[0223] Waste commercial plastic soda bottles are collected and the bottles made of PET are sorted and isolated. They are then ground and grated manually to a powder.

[0224] The PET powder is then depolymerized under the conditions of example 2.

[0225] Finally, hydrolysis of products IIa and IIb is performed by stirring the mixture at 25° C. for 2 hours in a solution of TBAF.3H.sub.2O (2.1 equiv. relative to the number of mols of IIa and IIb, taken together) in THF (3 mL). The hydrolyzed products are then separated by distillation under reduced pressure and purification on a chromatography column. This procedure leads to the production of ethylene glycol (colorless oil, 72% yield) and 1,4-phenylenedimethanol (white solid, 85% yield).

Abbreviations Used:

[0226] BHET=bis(hydroxyethylene) terephthalate
BPA=bisphenol A
DMC=dimethyl carbonate
EG=ethylene glycol
PC-BPA=carbonate polymer of bisphenol A
PET=polyethylene terephthalate
PLA=polylactic acid

PLLA=Poly(L-lactide)

[0227] PS=polystyrene
PVC=polyvinyl chloride
TBAF=Tetra-n-butylammonium fluoride
TBD=Triazabicyclodecene or 1,5,7-triazabicyclo[4.4.0]dec-5-ene
TEG=triethylene glycol
TPA=terephthalic acid