HETEROGENEOUS BIMETALLIC CATALYST, METHOD FOR PREPARING SAME AND USE THEREOF IN THE SYNTHESIS OF ETHYLENE GLYCOL FROM CARBON MONOXIDE

Abstract

A supported bimetallic catalyst according to the formula Pd-M/Support, which includes palladium and a metal M on a support, wherein M represents Cu or Ag, for use in a method for preparing ethylene glycol from an alcohol. The method includes two reaction steps catalyzed by the bimetallic catalyst of formula Pd-M/Support.

Claims

1.-15. (canceled)

16. A method of preparation of ethylene glycol comprising: a first reaction step A of oxidative carbonylation of an alcohol, in the presence of a supported bimetallic catalyst of formula Pd-M/Support, comprising palladium and a metal M on a support, in which M represents Cu or Ag, to obtain an oxalate compound as reaction intermediate, and a second reaction step B of hydrogenation of said oxalate compound, optionally purified, produced in reaction step A, to ethylene glycol, in the presence of a catalyst of formula Pd-M/Support.

17. The method of preparation of ethylene glycol according to claim 16, wherein said method comprising two reaction steps catalysed by the same bimetallic catalyst, in which the first catalysed reaction step A is an oxidative carbonylation, from an alcohol, carbon monoxide and an oxidant, in particular molecular oxygen, optionally in the presence of a promoter, to form an oxalate compound as reaction intermediate, and in which the second catalysed reaction step B is a hydrogenation reaction of the said oxalate compound with hydrogen to obtain ethylene glycol.

18. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, an oxidant, in particular oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, optionally a promoter, in particular an iodine compound, notably selected from tetramethylammonium iodide, potassium iodide or sodium iodide, preferably tetramethylammonium iodide, optionally a base, in particular triethylamine, optionally a solvent, in particular selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile; to obtain a reaction medium 1 which may be pressurised from 0.1 to 15 MPa, optionally heating said reaction medium 1 to a temperature from 25 to 200 C., preferably about 90 C., in particular during from 2 to 24 hours, preferably 16 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, optionally a solvent, in particular ethanol, methanol and dioxane, preferably ethanol or methanol, to obtain a reaction medium 2 which may be pressurised from 0.1 to 15 MPa, in particular 5 MPa, optionally heating said reaction medium 2 to a temperature from 100 to 250 C., in particular 200 or 220 C., preferably during from 5 to 24 hours, more preferably for 8 or 16 hours, to obtain ethylene glycol.

19. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, an oxidant, in particular oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter, in particular an iodine compound, notably selected from tetramethylammonium iodide, potassium iodide or sodium iodide, preferably tetramethylammonium iodide, a base, in particular triethylamine, a solvent, in particular selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile; to obtain a reaction medium 1 which may be pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent, in particular ethanol, methanol and dioxane, preferably ethanol or methanol, to obtain a reaction medium 2 which may be pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., preferably during from 5 to 24 hours, to obtain ethylene glycol.

20. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, an oxidant, in particular oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter, in particular an iodine compound, notably selected from tetramethylammonium iodide, potassium iodide or sodium iodide, preferably tetramethylammonium iodide, a base, in particular triethylamine, a solvent, in particular selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile; to obtain a reaction medium 1 pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent, in particular ethanol, methanol and dioxane, preferably ethanol or methanol, to obtain a reaction medium 2 pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., during from 5 to 24 hours, to obtain ethylene glycol.

21. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter selected from tetramethylammonium iodide, potassium iodide or sodium iodide, preferably tetramethylammonium iodide, to obtain a reaction medium 1 pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent, in particular ethanol, methanol and dioxane, preferably ethanol or methanol, to obtain a reaction medium 2 pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., during from 5 to 24 hours, to obtain ethylene glycol.

22. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter, a base, in particular triethylamine, a solvent selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile; to obtain a reaction medium 1 pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent selected from ethanol, methanol and dioxane, to obtain a reaction medium 2 pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., during from 5 to 24 hours, to obtain ethylene glycol.

23. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter, a base, in particular triethylamine, to obtain a reaction medium 1 pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent selected from ethanol, methanol and dioxane, to obtain a reaction medium 2 pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., during from 5 to 24 hours, to obtain ethylene glycol.

24. The method of preparation of ethylene glycol according to claim 16, wherein: reaction step A comprises bringing into contact: an alcohol, in particular selected from methanol and ethanol, carbon monoxide, oxygen O.sub.2, a catalyst of formula Pd-M/Support in which M represents Cu or Ag, a promoter, a base selected from triethylamine (Et.sub.3N), 2,6-lutidine, caesium carbonate (Cs.sub.2CO.sub.3), or 1-methylimidazole, in particular triethylamine, a solvent selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile; to obtain a reaction medium 1 pressurised from 0.1 to 15 MPa, heating said reaction medium 1 to a temperature from 25 to 200 C., during from 2 to 24 hours, to obtain the oxalate compound; reaction step B comprises bringing into contact: said oxalate compound, dihydrogen, said catalyst of formula Pd-M/Support in which M represents Cu or Ag, a solvent selected from ethanol, methanol and dioxane, to obtain a reaction medium 2 pressurised from 0.1 to 15 MPa, in particular 5 MPa, heating said reaction medium 2 to a temperature from 100 to 250 C., during from 5 to 24 hours, to obtain ethylene glycol.

25. The method of preparation of ethylene glycol according to claim 16, wherein reaction step A comprises bringing into contact an alcohol of Formula 1 to prepare an oxalate compound of Formula 2: ##STR00006## in which R.sub.a represents: a C.sub.1 to C.sub.20 linear or branched alkyl group, a C.sub.3 to C.sub.10 cycloalkyl group, a C.sub.5 to C.sub.20 alkyl-aryl or alkyl-heteroaryl group.

26. The method of preparation of ethylene glycol according to claim 16, wherein the alcohol of reaction step A is selected from methanol, ethanol and isopropanol.

27. The method of preparation of ethylene glycol according to claim 16, in which the catalyst support is an oxide selected from zirconium dioxide ZrO.sub.2, alumina Al.sub.2O.sub.3, silica SiO.sub.2, cerium dioxide CeO.sub.2, titanium dioxide TiO.sub.2, magnesium oxide MgO, indium oxide In.sub.2O.sub.3, or a mixture of these oxides, preferably zirconium dioxide ZrO.sub.2.

28. The method of preparation of ethylene glycol according to claim 16, in which the catalyst has a palladium content from 0.1 to 10%, in particular 2%, and a content of metal M from 0.1 to 40%, in particular 10% or 15%, by weight relative to the total weight of the catalyst.

29. The method of preparation of ethylene glycol according to claim 16, wherein said supported bimetallic catalyst is a PdCu/ZrO.sub.2 catalyst comprising palladium and copper on a zirconium dioxide support.

30. A bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula PdCu/ZrO.sub.2, comprising: a palladium content from 0.1 to 10%, in particular 2%, and a copper content from 0.1 to 40%, in particular 10%, by weight relative to the total weight of the catalyst and, a surface area, measured by BET, from 1 to 50 m.sup.2/g, in particular from 1 to 10 m.sup.2/g, preferably from 5 to 7 m.sup.2/g.

31. The bimetallic catalyst according to claim 30, further comprising: a crystalline phase of zirconium dioxide, analysed by X-ray diffraction, crystallised in monoclinic baddeleyite comprising a crystallite size from 20 to 100 nm, preferably from 20 to 50 nm, and optionally comprising hafnium atoms as an impurity.

32. The bimetallic catalyst according to claim 30, said catalyst being in the form of two populations of particles: a first population of particles with a polyhedral morphology and a second population of particles smaller in size than the first population and having a rounded and entangled morphology, with sizes from 10 nm to 1 micrometre, said particles forming clusters from 1 to 100 micrometres.

33. The bimetallic catalyst according to claim 30, further comprising: copper atoms in oxidation state (I) and (II), and palladium atoms in oxidation state (II), in particular the molar quantity of copper atoms in an oxidation state (I) is greater than that of copper atoms in an oxidation state (II).

34. A method of preparation of a PdCu/ZrO.sub.2 catalyst, comprising: a step C of impregnating a palladium salt and a copper salt, in particular palladium nitrate and copper nitrate, dissolved in an aqueous solution, in particular in a volume of water from 5 to 10 mL, on a zirconium dioxide support, in particular in powder form, with a ratio of solution mass/support mass from 0.6 and 1.0; to obtain PdCu/ZrO.sub.2 catalyst in the form of a homogeneous material, in particular said step C comprises: the use of a palladium salt concentration calculated to obtain a palladium content from 0.1 to 10% by weight relative to the total weight of the catalyst, the use of a copper salt concentration calculated to obtain a copper content from 0.1 to 40% by weight relative to the total weight of the catalyst, a step D of drying said homogeneous material, in particular at a temperature from 60 to 100 C., in particular 80 C., preferably for a period from 10 to 24 hours, in particular 16 hours, to obtain the PdCu/ZrO.sub.2 catalyst in the form of an anhydrous homogeneous material, an activation step E, in particular comprising calcination of said anhydrous homogeneous material at a temperature from 200 to 1000 C., in particular 600 C., preferably for a period from 1 to 15 hours, in particular 2 hours, in order to obtain said catalyst.

35. A bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula PdCu/ZrO.sub.2, obtainable by a method according to claim 34.

Description

[0422] FIG. 1 shows the X-ray photoelectron spectrometry spectrum of a PdCu/ZrO.sub.2 catalyst with a composition of 2% Pd and 10% Cu by weight relative to the total weight of the catalyst, prepared using a zirconium dioxide support with a specific surface area from 5 to 7 m.sup.2/g.

[0423] FIG. 2 shows two scanning electron microscopy images of a PdCu/ZrO.sub.2 catalyst with a composition of 2% Pd and 10% Cu by weight relative to the total weight of the catalyst, prepared with a zirconium dioxide support with a specific surface area from 5 to 7 m.sup.2/g.

[0424] FIG. 3 shows the diffraction pattern of a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst prepared with a zirconium dioxide support with a specific surface area from 5 to 7 m.sup.2/g.

[0425] FIG. 4 shows the diffraction patterns of two catalysts, Pd(2%)Cu(10%)/ZrO.sub.2 and Pd(1%)Cu(3%)/ZrO.sub.2, prepared using zirconium dioxide with a specific surface area greater than 85 m.sup.2/g.

[0426] FIG. 5 shows SEM images of a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst prepared using zirconium dioxide with a specific surface area from 5 to 7 m.sup.2/g.

[0427] FIG. 6 shows SEM images of a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst prepared using zirconium dioxide with a specific surface area greater than 85 m.sup.2/g.

[0428] FIG. 7 shows SEM images of a Pd(2%)Cu(10%)/-Al.sub.2O.sub.3 catalyst

[0429] FIG. 8 shows SEM images of a Pd(2%)Ag(15%)/-Al.sub.2O.sub.3 catalyst

[0430] FIG. 9 shows the XPS spectra of a Pd(2%)/ZrO.sub.2 catalyst.

[0431] FIG. 10 shows the XPS spectra of a Pd(2%)Cu(10%)/-Al.sub.2O.sub.3 catalyst.

[0432] FIG. 11 shows the XPS spectra of a Pd(2%)Ag(15%)/-Al.sub.2O.sub.3 catalyst.

EXAMPLES

Example 1Materials and Methods

[0433] The ZrO.sub.2 support, with a specific surface area of 5 to 7 m.sup.2/g, is supplied by Sterm Chemicals (15 Rue de l'Atome, 67800 Bischheim) (product number 93-4013. Without further clarification, hereafter the support named ZrO.sub.2 is that supplied by Sterm Chemicals.

[0434] The ZrO.sub.2 support (monoclinic phase), with a specific surface area greater than 85 m.sup.2/g is supplied by Alfa Aesar (Thermo Fisher Scientific) with product number AA4381522.

[0435] The -Al.sub.2O.sub.3 support is supplied by Sterm Chemicals (15 Rue de lAtome, 67800 Bischheim) with reference number 13-2525.

[0436] The SiO.sub.2 support (40-63 m) was supplied by VWR chemicals, reference number 151125P. Palladium nitrate (Pd(NO.sub.3).sub.2.Math.xH.sub.2O) and other metal salts such as Cu(NO.sub.3).sub.2.Math.3H.sub.2O, AgNO.sub.3 were supplied by Fischer.

[0437] The 450 mL and 1 L autoclaves are supplied by Parr Instrument Company.

Example 2General Procedure for the Preparation of Heterogeneous Pd/ZrO.SUB.2 .Catalysts

[0438] Pd(NO.sub.3).sub.2.Math.xH.sub.2O was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO.sub.2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

Example 3General Procedure for the Preparation of Heterogeneous Cu/ZrO.SUB.2 .Catalysts

[0439] Cu(NO.sub.3).sub.2.Math.3H.sub.2O was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO.sub.2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

Example 4General Procedure for the Preparation of Heterogeneous PdCu/ZrO.SUB.2 .Catalysts

[0440] Pd(NO.sub.3).sub.2.Math.xH.sub.2O and Cu(NO.sub.3).sub.2.Math.3H.sub.2O were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO.sub.2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

Example 5Preparation of Heterogeneous Mono- and Bimetallic Pd/ZrO.SUB.2., Cu/ZrO.SUB.2., PdCu/ZrO.SUB.2 .Catalysts

[0441] Table 1 below reports the preparation conditions for the Pd/ZrO.sub.2, Cu/ZrO.sub.2 and PdCu/ZrO.sub.2 catalysts prepared according to examples 2, 3 and 4.

TABLE-US-00001 TABLE 1 Prepared Pd/ZrO.sub.2, Cu/ZrO.sub.2 and PdCu/ZrO.sub.2 catalysts. Support ZrO.sub.2 Pd(NO.sub.3).sub.2xH.sub.2O Cu(NO.sub.3).sub.23H.sub.2O Catalyst (g) (mg) (mg) Pd(2%)/ZrO.sub.2 (10 g) 504 mg Cu(10%)/ZrO.sub.2 (10 g) 3802 Pd (2%)Cu(10%)/ZrO.sub.2 (10 g) 504 mg 3802

Example 6General Procedure for the Preparation of Heterogeneous PdCu/-Al.SUB.2.O.SUB.3 .Catalysts

[0442] Pd(NO.sub.3).sub.2.Math.xH.sub.2O and Cu(NO.sub.3).sub.2.Math.3H.sub.2O were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of -Al.sub.2O.sub.3 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

Example 7Preparation of Heterogeneous Bimetallic PdCu/-Al.SUB.2.O.SUB.3 .Catalysts

[0443] Table 2 below reports the conditions for preparing a PdCu/-Al.sub.2O.sub.3 catalyst prepared according to example 6.

TABLE-US-00002 TABLE 2 Prepared PdCu/-Al.sub.2O.sub.3 catalyst. Support ZrO.sub.2 Pd(NO.sub.3).sub.2xH.sub.2O Cu(NO.sub.3).sub.23H.sub.2O Catalyst (g) (mg) (mg) Pd (2%)Cu(10%)/ZrO.sub.2 (10 g) 504 mg 3802

Example 8General Procedure for the Preparation of Heterogeneous Ag/-Al.SUB.2.O.SUB.3 .Catalysts

[0444] AgNO.sub.3 was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, to form a solution. This solution containing the metal precursors was added to the appropriate amount of -Al.sub.2O.sub.3 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

Example 9General Procedure for the Preparation of Heterogeneous PdAg/-Al.SUB.2.O.SUB.3 .Catalysts

[0445] Pd(NO.sub.3).sub.2.Math.xH.sub.2O and AgNO.sub.3 were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of support -Al.sub.2O.sub.3 and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

[0446] Table 3 below reports the preparation conditions for the Ag/-Al.sub.2O.sub.3 and PdAg/-Al.sub.2O.sub.3 catalysts prepared according to examples 8 and 9.

TABLE-US-00003 TABLE 3 Prepared Ag/-Al.sub.2O.sub.3 and PdAg/-Al.sub.2O.sub.3 catalysts. Support -Al.sub.2O.sub.3 Pd(NO.sub.3).sub.2xH.sub.2O AgNO.sub.3 Catalyst (g) (mg) (mg) Ag(15%)/-Al.sub.2O.sub.3 (10 g) 2362 Pd (2%)Ag(10%) / -Al.sub.2O.sub.3 (10 g) 504 mg 1575

Example 10General Procedure for the Preparation of Heterogeneous PdAg/SiO.SUB.2 .Catalysts

[0447] Pd(NO.sub.3).sub.2.Math.xH.sub.2O and AgNO.sub.3 were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of SiO.sub.2 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80 C. for 16 hours and calcined at 600 C. for 2 hours to obtain the catalyst.

[0448] Table 4 below reports the conditions for preparing a PdAg/SiO.sub.2 catalyst prepared according to example 10.

TABLE-US-00004 TABLE 4 Prepared PdAg/SiO.sub.2 catalyst. Support ZrO.sub.2 Pd(NO.sub.3).sub.2xH.sub.2O AgNO.sub.3 Catalyst (g) (mg) (mg) Pd (2%)Ag(10%) / SiO.sub.2 (10 g) 504 mg 1575

Example 11General Heterogeneous Catalysis Procedure for the Oxidative Carbonylation of Methanol to Oxalates

[0449] A heterogeneous palladium catalyst (0.24 mmol Pd), tetrabutylammonium iodide TBAI (554 mg, 1.5 mmol) as promoter, tri-ethylamine Et.sub.3N (0.14 mL, 1.0 mmol), acetonitrile (50 mL) and methanol (25 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with oxygen (5 bar).

[0450] The autoclave was then pressurised with 15 bars of oxygen and a further 65 bars of carbon monoxide (total pressure of 80 bars). The reaction medium was then stirred at 90 C. for 16 h.

[0451] Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).

[0452] The final mixture obtained was then filtered and transferred to a 250 mL flask.

[0453] The reaction solvent and excess alcohol were separated by evaporation on a rotary evaporator.

[0454] The diethyloxalate was recovered after purification by recrystallisation in di-ethyl ether and the isolated yields were calculated.

[0455] For reactions in which the alcohol is used as a substrate in the presence of a solvent and also for reactions carried out in the absence of a solvent in which the alcohol plays the role of both substrate and solvent, the results are described in NCC in order to assess the catalytic efficiency, particularly due to the use in excess of alcohol as a substrate.

[0456] The NCC is calculated as follows:

[0457] NCC=number of moles of product formed/number of moles of Pd

Example 12General Heterogeneous Catalysis Procedure for the Oxidative Carbonylation of Ethanol to Oxalates

[0458] A heterogeneous palladium catalyst (0.24 mmol Pd), tetrabutylammonium iodide TBAI (1.5 to 3.6 mmol), tri-ethylamine Et.sub.3N (1.0 to 4.75 mmol), optionally acetonitrile MeCN (0 to 50 mL) as solvent and ethanol (25 to 75 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with oxygen (5 bar).

[0459] The autoclave was then pressurised with 15 bars of oxygen and a further 65 bars of carbon monoxide (total pressure of 80 bars). The reaction medium was then stirred at 90 C. for 16 h.

[0460] Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).

[0461] The final mixture obtained was then filtered and transferred to a 250 mL flask.

[0462] The reaction solvent and the excess alcohol were separated by evaporation on a rotary evaporator.

[0463] The diethyloxalate was recovered after purification by vacuum distillation at 120 C./50-20 mbar and the isolated yields were calculated.

Example 13General Heterogeneous Catalysis Procedure for the Hydrogenation of Dialkyl Oxalates

[0464] A heterogeneous copper or silver catalyst (4 mmol Cu or Ag), dialkyloxalate (20 mmol) and ethanol (50 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer.

[0465] The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with hydrogen (5 bar).

[0466] The autoclave was then pressurised with 50 bars of hydrogen. The reaction medium was then stirred at 200 C. for 16 h or 220 C. for 8 h.

[0467] Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).

[0468] The final mixture obtained was diluted in ethanol or methanol and then an internal standard was added (mesitylene) to calculate the yield by using GC-MS.

Example 14Tests Carried Out with Pd/ZrO.SUB.2 .Catalyst

[0469] Tables 5 and 6 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Pd/ZrO.sub.2 catalyst.

Reaction Step ACarbonylation

TABLE-US-00005 TABLE 5 Test conditions of oxidative carbonylation with a Pd/ZrO.sub.2 catalyst and the obtained results Pressure Solvent CO/O.sub.2 T Time Obtained Reaction Catalyst additives Substrate (ml) (bar) ( C.) (h) weight A1-1 Pd(2%)ZrO.sub.2 Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 4.73 g (0.24 mmol) (1 mmol) EtOH 50 mL (CO/O.sub.2) TBAI (1.5 mmol) A1-2 Pd(2%)ZrO.sub.2 Et.sub.3N 75 mL 65/15 90 16 3.6 g (0.24 mmol) (1 mmol) EtOH (CO/O.sub.2) TBAI (1.5 mmol)

Reaction Step BHydrogenation

TABLE-US-00006 TABLE 6 Test conditions of hydrogenation with a Pd/ZrO.sub.2 catalyst and the obtained results. Solvent Pressure T Time Yield Reaction Catalyst Substrate (ml) H.sub.2 (bar) ( C.) (h) (%)* B1-1 Pd(2%)ZrO.sub.2 20 mmol EtOH 50 (H.sub.2) 200 16 0 (0.47 mmol~2.3 mol %) DEO 50 mL *Hydrogenation yield is calculated using GC-MS, mesitylene is used as internal standard

Example 15Tests Carried Out with Cu/ZrO.SUB.2 .Catalyst

[0470] Tables 7 and 8 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Cu/ZrO.sub.2 catalyst.

Reaction Step ACarbonylation

TABLE-US-00007 TABLE 7 Test conditions of oxidative carbonylation with a Cu/ZrO.sub.2 catalyst and the obtained results. Pressure Solvent CO/O.sub.2 T Time Reaction Catalyst additives Substrate (ml) (bar) ( C.) (h) NCC A2 Cu(10%)ZrO.sub.2 Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 0 (4 mmol) (1 mmol) EtOH 50 mL (CO/O.sub.2) TBAI (1.5 mmol)

Reaction Step BHydrogenation

TABLE-US-00008 TABLE 8 Test conditions of hydrogenation with a Cu/ZrO.sub.2 catalyst and the obtained results. Solvent Pressure T Temps Reaction Catalyst Substrate (ml) H.sub.2 (bar) ( C.) (h) Yield (%)* B2 Cu(10%)ZrO.sub.2 20 mmol EtOH 50 (H.sub.2) 200 16 13 (12% (4 mmol = DEO 50 mL selectivity) 20 mol %) *Hydrogenation yield is calculated using GC-MS, mesitylene is used as internal standard

Example 16Tests Carried Out with Ag/-Al.SUB.2.O.SUB.3 .Catalyst

[0471] Tables 9 and 10 below respectively report the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Ag/-Al.sub.2O.sub.3 catalyst.

Reaction Step ACarbonylation

TABLE-US-00009 TABLE 9 Test conditions of oxidative carbonylation with a Ag/-Al.sub.2O.sub.3 and the obtained results. Pressure Solvent CO/O.sub.2 T Temps Catalyst additive Substrate (ml) (bar) ( C.) (h) NCC A3 Ag(15%)/-Al.sub.2O.sub.3 Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 0 (4 mmol) (1 mmol) MeOH 50 mL (CO/O.sub.2) TBAI (1.5 mmol)

Reaction Step BHydrogenation

TABLE-US-00010 TABLE 10 Test conditions of hydrogenation with a Ag/-Al.sub.2O.sub.3 catalyst and the obtained results. Solvent Pressure T Time Catalyst Substrate (ml) H.sub.2 (bar) ( C.) (h) Yield (%)* B3 Ag(15 wt %)%)/-Al.sub.2O.sub.3 20 mmol MeOH 50 (H.sub.2) 200 16 47 (76% (4 mmol = 20 mol %) DMO 50 mL selectivity) *Hydrogenation yield is calculated using GC-MS, mesitylene is used as internal standard

Example 17Tests Carried Out with the PdCu/Oxide Catalyst

[0472] Tables 11 and 12 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with PdCu catalysts on ZrO.sub.2 and on -Al.sub.2O.sub.3 supports.

Reaction Step ACarbonylation

TABLE-US-00011 TABLE 11 Test conditions of oxidative carbonylation with PdCu catalysts on ZrO.sub.2 and on -Al.sub.2O.sub.3 supports and the obtained results. Pressure Solvent CO/O.sub.2 T Time Obtained Catalyst additives Substrate (ml) (bar) ( C.) (h) weight A4-1 Pd(2%)Cu(10%)- Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 2.2 g -Al.sub.2O.sub.3 (1 mmol) MeOH 50 mL (CO/O.sub.2) (0.24 mmol) TBAI (1.5 mmol) A4-2 Pd(2%)Cu(10%)- Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 1.4 g -Al.sub.2O.sub.3 (1 mmol) EtOH 50 mL (CO/O.sub.2) (0.24 mmol) TBAI (1.5 mmol) A4-3 Pd(2%)Cu(10%)- Et.sub.3N 75 mL 65/15 90 16 3.71 g -Al.sub.2O.sub.3 (1 mmol) EtOH (CO/O.sub.2) (0.24 mmol) TBAI (1.5 mmol) A4-5 Pd(2%)Cu(10%)- Et.sub.3N 25 mL CH.sub.3CN 65/15 90 16 3.8 g ZrO.sub.2 (0.24 mmol) (1 mmol) EtOH 50 mL (CO/O.sub.2) TBAI (1.5 mmol) A4-6 Pd(2%)Cu(10%)- Et.sub.3N 75 mL 65/15 90 16 5.7 g ZrO.sub.2 (0.24 mmol) (1 mmol) EtOH (CO/O.sub.2) TBAI (1.5 mmol)

Reaction Step BHydrogenation

TABLE-US-00012 TABLE 12 Test conditions of hydrogenation with PdCu catalysts on ZrO.sub.2 and on -Al.sub.2O.sub.3 supports and the obtained results. Pressure H.sub.2 Time Catalyst Substrate Solvent (ml) (bar) T ( C.) (h) Yield (%) B4-1 Pd(2%)Cu(10%)- 20 mmol MeOH 50 (H.sub.2) 200 16 57 (76% -Al.sub.2O.sub.3 (4 mmol) DMO 50 mL selectivity) B4-2 Pd(2%)Cu(10%)- 20 mmol EtOH 50 (H.sub.2) 200 16 75% (80% -Al.sub.2O.sub.3 (4 mmol) DEO 50 mL selectivity) B4-3 Pd(2%)Cu(10%)- 20 mmol EtOH 50 (H.sub.2) 200 16 70 (90% ZrO.sub.2 (4 mmol) DEO 50 mL selectivity) B4-4 Pd(2%)Cu(10%)- 20 mmol EtOH 50 (H.sub.2) 200 16 82 (90% ZrO.sub.2 (5 mmol) DEO 50 mL selectivity) B4-5 Pd(2%)Cu(10%)- 20 mmol EtOH 50 (H.sub.2) 200 16 90 (90% ZrO.sub.2 (6 mmol) DEO 50 mL selectivity) B4-6 Pd(2%)Cu(10%)- 20 mmol EtOH 40 (H.sub.2) 220 8 92 (94% ZrO.sub.2 (4 mmol) DEO 50 mL selectivity)

Example 18Tests Carried Out with PdAg/-Al.SUB.2.O.SUB.3 .or SiO.SUB.2 .Catalyst

[0473] Tables 13 and 14 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with PdAg/-Al.sub.2O.sub.3 or SiO.sub.2 catalyst.

Reaction Step ACarbonylation

TABLE-US-00013 TABLE 13 Test conditions of oxidative carbonylation tests with PdAg/-Al.sub.2O.sub.3 or SiO.sub.2 catalyst SiO.sub.2 supports and the obtained results. Pressure Solvent CO/O.sub.2 T Time Obtained Catalyst Additive Substrate (ml) (bar) ( C.) (h) weight A5-1 Pd(2%)Ag(10%)- Et.sub.3N 50 mL CH.sub.3CN 65/15 90 16 3.5 g -Al.sub.2O.sub.3 (1 mmol) MeOH 100 mL (CO/O.sub.2) (0.24 mmol) TBAI (1.5 mmol) A5-2 Pd(2%)Ag(10%)- Et.sub.3N 50 mL CH.sub.3CN 65/15 90 16 3.1 g SiO.sub.2 (0.24 mmol) (1 mmol) MeOH 100 mL (CO/O.sub.2) TBAI (1.5 mmol)

Reaction Step BHydrogenation

TABLE-US-00014 TABLE 14 Test conditions of hydrogenation with PdAg catalysts on -Al.sub.2O.sub.3 or SiO.sub.2 supports and the obtained results. Pressure H.sub.2 Time Catalyst Substrate Solvent (ml) (bar) T ( C.) (h) Yield (%) B5-1 Pd(2%)Ag(10%)- 20 mmol MeOH 50 (H.sub.2) 200 16 30 (37% -Al.sub.2O.sub.3 (4 mmol) DMO 50 mL selectivity) B5-2 Pd(2%)Ag(10%)- 20 mmol MeOH 50 (H.sub.2) 200 16 7 (12% SiO.sub.2 (4 mmol) DMO 50 mL selectivity)

Example 19General Catalyst Recycling Procedure after the Hydrogenation of Dialkyl Oxalates

[0474] After one hydrogenation reaction of dialkyl oxalates, the catalyst (Cu or Ag) is separated from the liquid reaction medium by filtration. The catalyst was then washed with 325 mL ethanol. The material was then dried at 80 C. for 4 h before being used again in a hydrogenation reaction of dialkyl oxalate.

Example 20Catalyst Recycling Tests after the Hydrogenation of Dialkyl Oxalates

[0475] Tables 15 and 16 below report respectively the test conditions of hydrogenation (reaction step B) and the recycling results according to example 19.

TABLE-US-00015 TABLE 15 Test conditions of hydrogenation with a PdCu/ZrO.sub.2 catalyst and the obtained results. Pressure H.sub.2 Catalyst Substrate Solvent (ml) (bar) T ( C.) Time (h) Yield (%) B6-1 Pd(2%)Cu(10%)- 20 mmol MeOH 50 (H.sub.2) 200 16 82% (90% ZrO.sub.2 (5 mmol) DMO 50 mL selectivity)

TABLE-US-00016 TABLE 16 Recycling results of hydrogenation tests using a PdCu/ZrO.sub.2 catalyst. Cycles Yield 1 90% (90% selectivity) 2 90% (90% selectivity) 3 78% (77% selectivity)

Example 21: Optimisation of the Carbonylation Reaction with PdCu/ZrO.SUB.2

[0476] Table 17 below reports the results of oxidative carbonylation tests (reaction step A) with variations in the conditions (nature of the base, additive, O/CO.sub.2 pressure, reaction time, quantity of catalyst and substrate) compared with the general procedure according to example 12 with a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst prepared according to example 5.

[0477] The carbonylation yield was calculated using GC-MS, with chlorobenzene used as an internal standard.

TABLE-US-00017 TABLE 17 Test conditions of the oxidative carbonylation with a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst and the obtained results. Base Additive O.sub.2/CO T, Time, Reaction Cat (mmol) (mmol) (bar) ( C.) (h) Scale Results A4-6 Pd(2%)-Cu(10%)- Et.sub.3N (1) TBAI 15/65 90 16 75 mL 5.7 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 162 A6-1 Pd(2%)-Cu(10%)- Et.sub.3N (2) TBAI 15/65 90 8 50 mL 3.05 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 87 A6-2 Pd(2%)-Cu(10%)- 2,6-lutidine TBAI 15/65 90 8 50 mL 2.5 g ZrO.sub.2 (0.24 mmol) (2) (1.5) EtOH NCC = 71 A6-3 Pd(2%)-Cu(10%)- Cs.sub.2 CO.sub.3 TBAI 15/65 90 8 50 mL 1.23 g ZrO.sub.2 (0.24 mmol) (2) (1.5) EtOH NCC = 35 A6-4 Pd(2%)-Cu(10%)- 1-Methyl- TBAI 15/65 90 8 50 ml 1.3 g ZrO.sub.2 (0.24 mmol) imidazol (1.5) EtOH NCC = 37 (2) A6-5 Pd(2%)-Cu(10%)- Et.sub.3N (2) TBAI 15/65 90 8 50 mL 1.7 g ZrO.sub.2 (0.24 mmol) (0.5) EtOH NCC = 48 A6-6 Pd(2%)-Cu(10%)- Et.sub.3N (2) CuCl.sub.2 15/65 90 8 50 mL 0.61 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 17 A6-7 Pd(2%)-Cu(10%)- Et.sub.3N (2) FeCl.sub.3 15/65 90 8 50 mL 1.4 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 40 A6-8 Pd(2%)-Cu(10%)- Et.sub.3N (2) NaI 15/65 90 8 50 mL 3.8 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 108 A6-9 Pd(2%)-Cu(10%)- Et.sub.3N (2) KI 15/65 90 8 50 mL 3.23 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 92 A6-10 Pd(2%)-Cu(10%)- Et.sub.3N (2) CaI.sub.2 15/65 90 8 50 mL 3.3 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 94 A6-11 Pd(2%)-Cu(10%)- Et.sub.3N (2) NaI 15/65 90 8 50 mL 2.34 g ZrO.sub.2 (0.12 mmol) (1.5) EtOH NCC = 67 A6-12 Pd(2%)-Cu(10%)- Et.sub.3N (2) NaI 10/65 90 8 50 mL 3.4 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 97 A6-13 Pd(2%)-Cu(10%)- Et.sub.3N (2) NaI 5/65 90 8 50 ml 3.1 g ZrO.sub.2 (0.24 mmol) (1.5) EtOH NCC = 88

Example 22: Volume Optimisation

[0478] Tests were carried out in a one-litre reactor.

Test A-7-2

[0479] A heterogeneous catalyst based on palladium Pd(2%)Cu(10%)/ZrO.sub.2 (0.54 mmol Pd), NaI (0.252 g, 1.68 mmol), tri-ethylamine (0.630 mL, 4.5 mmol), and ethanol (225 mL) were introduced into a 1 L Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar), and twice with oxygen (5 bar). The autoclave was then pressurised with 15 bar of oxygen and a further 65 bar of carbon monoxide (total pressure 80 bar). The reaction mixture was then stirred at 90 C. for 16 h. Once the reaction was complete, the autoclave was allowed to return to room temperature before being depressurised and purged three times with nitrogen (5 bar). The reaction mixture was then filtered and the recovered solution transferred to a 500 mL flask. The reaction solvent and the excess alcohol were separated by evaporation on a rotary evaporator. The oxalate was recovered after purification (vacuum distillation at 120 C./50-20 mbar for the diethyloxalate) and the isolated yields were calculated.

[0480] Tests A7-1 and A7-3 were carried out with variations in the concentrations of the catalyst, base, additive or substrate (ethanol) compared with the preparation conditions for test A7-2 described above.

[0481] Table 18 below reports the conditions and results of oxidative carbonylation tests (reaction step A) in a one-litre Parr autoclave, using a Pd(2%)Cu(10%)/ZrO.sub.2 catalyst prepared according to example 5.

TABLE-US-00018 TABLE 18 Conditions and results of oxidative carbonylation tests in a one-litre Parr autoclave. Base Additives O.sub.2/CO T, Time, Reaction Cat (mmol) (mmol) (bar) ( C.) (h) Scale Results A7-1 Pd(2%)- Et.sub.3N NaI 15/65 90 16 225 mL 13 g Cu(10%)-ZrO.sub.2 (9) (6.75) EtOH NCC = 82 (1.08 mmol) After distillation A7-2 Pd(2%)- Et.sub.3N NaI 15/65 90 16 225 mL 13 g Cu(10%)-ZrO.sub.2 (4.5) (1.68) EtOH NCC = 165 (0.54 mmol) After distillation A7-3 Pd(2%)- Et.sub.3N NaI 15/65 90 16 150 mL 10.5 g Cu(10%)-ZrO.sub.2 (4.5) (3.37) EtOH NCC = 133 (0.54 mmol) After distillation

Example 23: Influence of the Support and Preparation of PdCu/ZrO.SUB.2 .Catalysts

[0482] In order to determine the influence of the ZrO.sub.2 support and of the preparation of the catalysts, Cat B and Cat C catalysts were produced using another zirconium dioxide support, ZrO.sub.2, consisting of a monoclinic crystalline phase, called hereinafter ZrO.sub.2 (monoclinic phase) marketed by Alpha Aesar.

[0483] The ZrO.sub.2 support (monoclinic phase) is identical to that used by Yuqing et al (Chinese Journal of Catalysis, 36, 2015, 1552-1559).

Catalyst Cat A

[0484] The Pd(2%)Cu(10%)/ZrO.sub.2 catalyst, hereafter referred to as Cat A, prepared according to example 5 was compared with Cat B and Cat C catalysts of the same nature but using a support with different characteristics or a different preparation.

Catalyst Cat B: Influence of the Support

[0485] The Pd(2%)Cu(10%)/ZrO.sub.2 (monoclinic phase), hereinafter referred to as Cat B, was prepared according to example 5 using the ZrO.sub.2 support (monoclinic phase), supplied by Alfa Aesar (Thermo Fisher Scientific) with product number 43815, having a specific surface area greater than 85 m.sup.2/g.

Catalyst Cat C: Influence of Preparation

[0486] The Pd(1%)Cu(3%)/ZrO.sub.2 catalyst (monoclinic phase), referred to hereafter as Cat C, was prepared with the ZrO.sub.2 support (monoclinic phase), supplied by Alfa Aesar, according to that described by the article Yuqing Jia et al. (Chinese Journal of Catalysis, 36, 2015, 1552-1559), namely in two successive steps: [0487] an initial impregnation step with a palladium salt followed by calcination in air at 350 C. [0488] a second impregnation step with a copper salt followed by calcination in air at 350 C.
Unlike Yuqing Jia et al, a final reduction step was not carried out under hydrogen flow.

Example 24

[0489] Tables 19 and 20 below show respectively the conditions and yield results for the oxidative carbonylation (reaction step A) and hydrogenation (reaction step B) tests using Cat A, Cat B and Cat C catalysts.

TABLE-US-00019 TABLE 19 Conditions of oxidative carbonylation tests with Cat A, Cat B and Cat C catalysts and obtained results Base Additives O.sub.2/CO T Time Reaction Cat (mmol) (mmol) (bar) ( C.) (h) Scale Results A4-6 Cat A: Pd(2%)- EtN.sub.3 TBAI 15/65 90 16 75 mL 5.7 g Cu(10%)-ZrO.sub.2 (1) (1.5) EtOH NCC = 162 (0.24 mmol) A8-1 Cat B: Pd(2%)- EtN.sub.3 TBAI 15/65 90 16 75 mL 4.9 g Cu(10%)-ZrO.sub.2 (1) (1.5) EtOH NCC = 140 (monoclinic phase) (0.24 mmol) A8-2 Cat C: Pd(1t %)- EtN.sub.3 TBAI 15/65 90 16 75 mL 4.16 g Cu(3t %)-ZrO.sub.2 (1) (1.5) EtOH NCC = 119 (monoclinic phase) (0.24 mmol)

TABLE-US-00020 TABLE 20 Conditions of hydrogenation tests with Cat A, Cat B and Cat C catalysts and the obtained results T Time Cat Substrate Solvent (ml) Gas (bar) ( C.) (h) Yield (%) B4-6 Cat A: Pd(2%)Cu(10%)- 20 mmol EtOH 40 (H.sub.2) 220 8 92 (94% ZrO.sub.2 (4 mmol) DEO 50 mL selectivity) B8-1 Cat B: Pd(2%)Cu(10%)- 20 mmol EtOH 40 (H.sub.2) 220 8 61% (70% ZrO.sub.2 (monoclinic DEO 50 mL selectivity) phase) (4 mmol) B8-2 Cat C: Pd(1%)Cu(3%)- 20 mmol EtOH 40 (H.sub.2) 220 8 37% (35% ZrO.sub.2 (monoclinic WD 50 mL selectivity) phase) (4 mmol)

[0490] These results indicate a higher yield of the carbonylation of ethanol to diethyloxalate (step A) with a yield of 5.7 g and of the hydrogenation of oxalate to ethylene glycol (step B) with a yield of 92% and a selectivity of 94% for catalyst Cat A of the invention. 10

[0491] Cat B and Cat C catalysts, prepared with a ZrO.sub.2 support from Alfa Aesar, are less efficient for carbonylation in terms of yield, but also for the hydrogenation step, with yields of 61% and 37% and selectivities of 70% and 35% respectively. In particular, Cat C catalyst prepared according to Yuqing Jia et al. is the least efficient in terms of carbonylation yield (step A) and in particular in terms of hydrogenation yield and selectivity (step B), which are 2.5 times lower than those of Cat A.

Example 24: Analysis of PdCu/ZrO.SUB.2 .CatalystsSpecific Surface Area

[0492] The specific surface area of Cat A, Cat B and Cat C catalysts was measured by BET. The results are shown in Table 21 below.

TABLE-US-00021 TABLE 21 Specific surface area of catalysts by BET Specific surface Catalyst area BET Cat A : 5.64 m.sup.2/g Pd (2%) Cu(10%)/ ZrO.sub.2 Cat B 62.85 m.sup.2/g Pd (2%) Cu(10%)/ ZrO.sub.2 (monoclinic phase) Cat C : 81.92 m.sup.2/g Pd (1%) Cu(3%)/ ZrO.sub.2 (monoclinic phase) prepared according to Jia et al.

Example 25: Structural Analysis of PdCu/ZrO.SUB.2 .Catalysts

a) StructurePhase Analysis

[0493] X-ray powder diffractograms of Cat A, Cat B and Cat C catalysts were carried out using a Rigaku MINIFLEX II diffractometer, which emits X-rays via a tube and a copper source (wavelength K 1.54 ).

[0494] FIGS. 3 and 4 represent the X-ray diffractograms obtained for Cat A, Cat B and Cat C catalysts respectively.

[0495] The results of the analysis of the various diffractograms obtained for Cat A, Cat B and Cat C catalysts are presented respectively in Tables 22, 23 and 24 below.

TABLE-US-00022 TABLE 22 Phase analysis of Cat A catalyst Crystalline phases identified Crystalline phases ICDD by the database identified sheet Cat A Baddeleyite - ZrO.sub.2 00-037-1484 Pd(2%)Cu(10%)ZrO.sub.2 Copper monoxide - CuO 01-089-2531 (Sterm) Palladium oxide - PdO 00-043-1024 Palladium, syn - Pd 01-087-0637

TABLE-US-00023 TABLE 23 Phase analysis of Cat B catalyst Crystalline phases identified Crystalline phases ICDD by the database identified sheet Cat B Baddeleyite - ZrO.sub.2 00-037-1484 Pd(2%)Cu(10%)ZrO.sub.2 (mono- Copper monoxide - CuO 01-089-2531 clinic phase) Palladium oxide - PdO 00-043-1024 Palladium, syn - Pd 01-087-0637

TABLE-US-00024 TABLE 24 Phase analysis of Cat C catalyst Crystalline phases identified Crystalline phases ICDD by the database identified sheet Cat C Baddeleyite - ZrO.sub.2 00-037-1484 Pd(1%)Cu(3%)ZrO.sub.2 (monoclinic phase) Palladium oxide - PdO 00-043-1024

[0496] The diffractograms show the presence of crystallised phases.

[0497] The XRD analyses indicate that the same crystalline baddeleyite phase (ZrO.sub.2) is present in all three catalysts with the presence of a palladium oxide phase. In the case of Cat A and Cat B catalysts, copper monoxide and palladium phases in metallic state are observed.

[0498] The diffraction peaks of Cat A and Cat B catalysts can be distinguished from the peaks of the Baddeleyite phase of the support. Cat A peaks are narrower in width than Cat B peaks.

b) StructureCrystallinity

Crystallite Size

[0499] The crystallinity of materials is characterised by the size of the crystallites.

[0500] The crystallite size was qualitatively estimated in order to compare the different ZrO.sub.2 supports of Cat A and Cat B catalysts. As a reminder, Cat B and Cat C catalysts were prepared using ZrO.sub.2 support identical to that used in Yuqing Jia et al. (Chinese Journal of Catalysis, 36, 2015, 1552-1559) marketed by Alfa Aesar.

[0501] The size of the crystallites was evaluated using the following Scherrer formula:

[00002]$t=\frac{k.Math.}{H.Math.\cos }$ [0502] t=crystallite size [0503] k=correction factor=0.89 [0504] =wavelength of the source [0505] H=width at half-height of peak (in radians) [0506] =diffraction angle

[0507] The width at half-height was estimated using ImageJ processing software (developed by the National Institutes of Health).

[0508] The crystallite size calculations from Cat A and Cat B diffractograms are shown in Table 25 below:

TABLE-US-00025 TABLE 25 Crystallite sizes Crystallite sizes Reference (nm) Cat A Pd(2%)Cu(10%) / ZrO.sub.2 of Sterm 31.4 nm Cat B Pd(2%)Cu(10%) / ZrO.sub.2 (monoclinic phase) from 9.3 Alfa Aesar

[0509] The support used in Yuqing Jia et al. is a commercial ZrO.sub.2 oxide powder from Alfa Aesar, with a pore volume of 0.27 cc/g and a specific surface area more than 85 m.sup.2/g (BET).

[0510] The low value of the sizes, in particular less than 10 nanometres, is an indicator of a low crystallinity structure. The smaller the crystallites, the wider the diffraction peaks. This effect becomes visible for crystallites less than 1 m in diameter.

[0511] The results indicate that the catalyst prepared with Sterm's ZrO.sub.2 support and the catalysts prepared with Alfa Aesar's ZrO.sub.2 support have crystallite sizes of 31 nm and 9 nm respectively. Cat A and Cat B catalysts are thus distinguished by the microstructure of ZrO.sub.2 support.

[0512] In addition to the characteristic related to the specific surface area, these results show that Cat A and Cat B catalyst supports are different in terms of their microstructure.

[0513] Thus, as shown in Examples 17, 21 and 24, catalysts prepared with a ZrO.sub.2 support having a crystallite size of about 30 nm used for steps A and B of ethylene glycol preparation are more efficient than PdCu/ZrO.sub.2 catalysts prepared with a more polycrystalline and lower crystallinity ZrO.sub.2 support having a crystallite size of about 9 nm.

Example 26: Morphology and Composition Analysis

[0514] The SEM images in FIGS. 2, 5, 6, 7 and 8 were taken using a Zeiss MEB-FEG scanning microscope with controlled pressure, making it possible to observe materials with little or no conductivity without any specific preparation.

[0515] The sample was stabilised on carbon adhesive paper to enable SEM observation. It should therefore be noted that the content of the element carbon can be associated with the use of the latter.

[0516] Quantification was carried out by EDX spectrum analysis on sample areas of the catalysts. The results are expressed as a percentage by mass.

[0517] The results of the SEM observations and EDX analysis are summarised below.

Cat A: Pd(2%)Cu(10%)/ZrO.SUB.2 .(Sterm)

[0518] SEM images are shown in FIGS. 2 and 5. Entangled elongated particles with heterogeneous thicknesses of less than a micrometre can be seen. These particles form clusters of a few micrometres to a hundred micrometres.

[0519] The EDX analysis of one zone of the sample is shown in Table 26. The particles are composed mainly of zirconium (Zr), oxygen (O) and copper (Cu) and to a lesser extent of palladium (Pd), hafnium (Hf) and carbon.

TABLE-US-00026 TABLE 26 Chemical composition of Cat A catalyst Quantification using the EDX spectrum Element (in % by mass) C 1.32 O 24.89 Zr 62.91 Pd 1.42 Cu 7.91 Hf 1.56 Total 100.00

Catalyst: Pd(2%)/ZrO.SUB.2 .(Sterm)

[0520] SEM observations of Pd(2%)/ZrO.sub.2 catalyst prepared with Sterm's ZrO.sub.2 support reveal a morphology similar to that of Cat A catalyst, namely entangled elongated particles of heterogeneous thickness less than one micrometre forming clusters.

Cat B: Pd(2%)Cu(10%)/ZrO.SUB.2 .(Monoclinic Phase) Alfa Aesar

[0521] FIG. 6 shows SEM images of the Cat B catalyst. The SEM observations reveal the presence of a population of macroscopic particles with a polyhedral morphology of a few hundred micrometres, with smaller particles with a spherical morphology of a few tens of nanometres on the surface.

[0522] The EDX analysis of two zones of the sample is shown in Table 27.

[0523] These particles are composed mainly of copper (Cu), zirconium (Zr), palladium (Pd) and oxygen (O), with a minority of carbon (C) and traces of hafnium (Hf) and rhenium (Re).

TABLE-US-00027 TABLE 27 Chemical composition of Cat B catalyst Zone 1 - Quantification by Zone 2- Quantification EDX spectrum (in % by using the EDX spectrum Element mass) (in % by mass) C 2.82 1.42 O 16.66 17.01 Zr 26.26 37.31 Pd 13.97 7.13 Cu 38.92 34.06 Hf 0.68 2.25 Re 0.68 0.83 Total 100.00 100.00

Cat C: Pd(1%)Cu(3%)/ZrO.SUB.2 .(Monoclinic Phase) Alfa Aesar Prepared According to Jia et al.

[0524] SEM observations reveal the presence of micrometric particles with a polyhedral morphology and nanometric particles.

[0525] The EDX analysis of one zone of the sample is shown in Table 28.

[0526] These particles are composed mainly of zirconium (Zr), oxygen (O) and copper (Cu), and to a lesser extent carbon (C), hafnium (Hf) and rhenium (Re), with traces of palladium (Pd).

TABLE-US-00028 TABLE 28 Chemical composition of Cat C catalyst Quantification using the EDX spectrum Element (in % by mass) C 2.14 O 27.19 Zr 59.07 Pd 0.84 Cu 8.11 Hf 1.38 Re 1.28 Total 100.00
Catalyst Pd(2%)Cu(10%)/-Al.sub.2O.sub.3

[0527] FIG. 7 shows the SEM images of the Pd(2%)Cu(10%)/-Al.sub.2O.sub.3. SEM observations reveal the presence of a population of macroscopic particles with a generally spherical morphology, agglomerated to a size of a few tens of micrometres, with a porous, honeycomb-like morphology on the surface.

Catalyst Pd(2%)Ag(15%)/-Al.sub.2O.sub.3

[0528] FIG. 8 shows the SEM images of the Pd(2%)Ag(15%)/-Al.sub.2O.sub.3. SEM observations reveal the presence of a population of macroscopic particles with a generally spherical morphology, agglomerated to a size of a few tens of micrometres, which have a porous morphology with a honeycomb appearance on the surface. The particles have the same appearance and morphology as the Pd(2%)Cu(10%)/v-Al.sub.2O.sub.3.

Example 27: Surface Study of XPS Catalysts

[0529] Analyses are carried out using a PHI QUANTES photoemission spectrometer. This instrument is equipped with a monochromate X-ray source (aluminium K.sub. line) as well as a chromium X-ray source for Hard XPS, a charge neutralisation system for electrically insulating samples and a hemispherical electron analyser.

[0530] XPS analyses were carried out on: [0531] Cat A: Pd(2%)Cu(10%)/ZrO.sub.2 (Sterm) (see spectra in FIG. 1) [0532] Pd(2%)/ZrO.sub.2 catalyst (Sterm) (see spectrum in FIG. 9) [0533] Pd(2%)Cu(10%)/-Al.sub.2O.sub.3 (see spectrum in FIG. 10) [0534] Pd(2%)Ag(15%)/v-Al.sub.2O.sub.3 (see spectrum in FIG. 11)

Cat A

Cu2p Spectrum

[0535] Analysis of the XPS spectra over several zones reveals a variation of the satellite typical for CuO (around 940-945 eV), indicating the presence of a mixture of Cu+ and Cu2+.

[0536] The Cu+ concentration is higher because Auger signal is dominated by this component (916.8 eV). The presence of metallic Cu cannot be detected either on the Cu2p spectrum or on the Auger spectrum. If it is present, it is masked by the signals corresponding to Cu+.

Pd3d Spectrum

[0537] Pd3d is interfered by Zr3p signal. A reference ZrO.sub.2 powder was measured in order to extract the Zr3p signal, i.e. Zr3p3 at 332.9 eV and Zr3p1 at 346.61 eV.

[0538] The presence of Pd2+ is confirmed by the corresponding Pd3d5/2 signal (located at 337.5 eV) which is visible.

Pd(2%)/ZrO.SUB.2 .Catalyst (Sterm) (See FIG. 9)

Pd3d Spectrum

[0539] The Zr3d spectra overlap, at least in energy. The width is slightly greater, which may be due to differential charging. This correspondence of binding energies should be found in the case of Pd3d.

[0540] Pd3d is interfered by Zr3p signal. The presence of Pd2+ is certain, as the corresponding Pd3d5/2 signal (located at 337 eV) is visible.

Pd(2%)Cu(10%)/-Al.sub.2O.sub.3 (See Spectrum in FIG. 10 and Table 29 Below)

Cu2p Spectrum

[0541] Cu2p spectra mainly show the presence of Cu2+ in the form of oxide and hydroxide (based on the appearance of the satellite).

Pd3d Spectrum

[0542] Pd3d spectra are identical for the two zones measured.

[0543] Pd3d5/2 component is located at 337.5 eV.

TABLE-US-00029 TABLE 29 Binding energies of XPS spectrum of the Pd(2%) Cu(10%)/ -Al.sub.2O.sub.3 Peak Name (Binding energy) Cu2p3 935.08 Pd3d 337.49 Al2s 119.64
Pd(2%)Ag(15%)/-Al.sub.2O.sub.3 (See Spectrum in FIG. 11 and Table 30 Below)

Ag3d Spectrum

[0544] Ag3d spectrum was difficult to interpret and required comparison with reference spectra (metallic Ag spectrum). An analysis of the Auger signals shows that it is a mixture of Ag oxides (I and II).

Pd3d Spectrum

[0545] For Pd3d spectrum, the energy position is slightly lower at 337.2 eV, with an additional component at lower binding energy; Pd3d peaks for the sample are wider. There is therefore a difference of 0.3 eV in the position of Pd5/2 peak between the two samples.

TABLE-US-00030 TABLE 30 Binding energies of the XPS spectrum of the catalyst Peak Name (Binding energy) Ag3d5 368.67 Pd3d 337.21 Al2p 74.77