WO2020001840A1

WO2020001840A1 - Catalyst for base-free aerobic oxidation of glucose to glucaric acid; said process and said catalyst's preparation

Info

Publication number: WO2020001840A1
Application number: PCT/EP2019/061973
Authority: WO
Inventors: Natalia POTRZEBOWSKA; Michèle BESSON; Catherine Pinel; Noémie PERRET; Elie Derrien; Philippe Marion
Original assignee: Rhodia Operations; Le Centre National De La Recherche Scientifique; Universite Claude Bernard Lyon 1
Priority date: 2018-06-27
Filing date: 2019-05-09
Publication date: 2020-01-02

Abstract

The invention relates to a process for manufacturing a catalyst composition exhibiting high activity and selectivity in the oxidation of e.g. glucose to glucaric acid using molecular oxygen as the terminal oxidant. More specifically, the invention relates to a composition comprising multimetal-type catalysts, such as Au-Pt-type catalysts. The process of the present invention employs means such as ultrasonication and/or microwaving to improve the performance of the catalyst. The invention is also related to a catalyst composition obtainable by the process of the invention, and to a process for preparing glucaric acid from glucose employing the catalyst composition of the invention.

Description

CATALYST FOR BASE-FREE AEROBIC OXIDATION OF GLUCOSE TO

GLUCARIC ACID; SAID PROCESS AND SAID CATALYST'S PREPARATION

Cross-reference to a Related Application

[0001] This application claims priority to European application No. 18305823.9 filed on June 27, 2018. The entire content of this application is explicitly incorporated herein by this reference.

Technical Field

[0002] The present invention relates to a process for manufacturing a catalyst composition exhibiting high activity and selectivity in the oxidation of e.g. glucose to glucaric acid using molecular oxygen as the terminal oxidant. More specifically, the invention relates to a composition

comprising multimetal-type catalysts, such as Au-Pt-type catalysts. The process of the present invention employs means such as ultrasonication and/or microwaving to improve the performance of the catalyst. The invention is also related to a catalyst composition obtainable by the process of the invention, and to a process for preparing glucaric acid from glucose employing the catalyst composition of the invention.

Background Art

[0003] For many years there has been interest in using biorenewable materials as a feedstock to replace or supplement crude oil. See, for example, Klass, D.L., Biomass for Renewable Energy, Fuels, and Chemicals, Academic Press, 1998. Moreover, there have been efforts to produce carboxylic acids from renewable resources using processes involving a combination of biocatalytic and chemocatalytic processes. See, for example, Frost,

J.W., et al. , Benzene-Free Synthesis of Adipic Acid, Biotechnol.

Prog. 18(2) (2002), 201 - 211 , and U.S. Pat. Nos. 4,400,468,

and 5,487,987.

[0004] One of the major challenges for converting biorenewable resources such as carbohydrates (e.g., glucose derived from starch, sucrose or cellulose) to current commodity and specialty chemicals is the selective conversion of the primary alcohol (hydroxyl) group to a carboxyl group (COOH) in the presence of at least one secondary alcohol group.

[0005] Glucose can be obtained from various carbohydrate-containing sources including conventional biorenewable sources such as corn grain (maize), wheat, potato, cassava and rice as well as alternative sources such as energy crops, plant biomass, agricultural wastes, forestry residues, sugar processing residues and plant-derived household wastes. More generally, biorenewable sources include any renewable organic matter that includes a source of carbohydrates such as, for example, switch grass, miscanthus, trees (hardwood and softwood), vegetation, and crop residues

(e.g., bagasse and corn stover). Other sources can include, for example, waste materials (e.g., spent paper, green waste, municipal waste, etc.).

[0006] Carbohydrates such as glucose may be isolated from biorenewable

materials using methods that are known in the art. See, for example,

Centi, G. and van Santen, R.A., Catalysis for Renewables, Wiley-VCH, Weinheim 2007; Kamm, B., Gruber, P.R. and Kamm, M., Biorefineries- industriai Processes and Products: Status Quo and Future Directions, Wiley-VCH, Weinheim 2006; Yang, S.-T. (ed.), Bioprocessing for

Value-Added Products from Renewable Resources New Technologies and Applications, Elsevier, Amsterdam 2007; Wurzburg, O.B. in Furia,

T.E. (ed.),“ Starch in the Food industry”, Chapter 8 of CRC Handbook of Food Additives, 2nd Edition, Voi. 1, CRC Press, Boca Raton 1973.

See also chapters devoted to Starch, Sugar and Syrups within KirkOthmer Encyclopedia of Chemical Technology 5th Edition, John Wiley and Sons, New York 2001. Also, processes to convert starch to glucose are known in the art, see, for example, Schenck, " Glucose and Glucose-containing Syrupd' in Uiimann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim 2009. Furthermore, methods to convert cellulose to glucose are known in the art, see, for example, Centi, G. and van Santen, R.A., Catalysis for Renewables, Wiley-VCH, Weinheim 2007; Kamm, B.,

Gruber, P.R. and Kamm, M., Biorefineries-industrial Processes and Products: Status Quo and Future Directions, Wiley-VCH, Weinheim 2006; Yang, S.-T. (ed.), Bioprocessing for Value-Added Products from

Renewable Resources New Technologies and Applications, Elsevier, Amsterdam 2007.

[0007] The selective oxidation of glucose to glucaric acid has been attempted by using oxidation methods that employ platinum-based (Pt) catalysts. See, for example, U.S. Pat. No. 2,472,168, which illustrates a method for the preparation of glucaric acid from glucose using a platinum catalyst in the presence of oxygen and a base. Further examples of the preparation of glucaric acid from glucose using a platinum catalyst in the presence of oxygen and a base are illustrated in J. Catal. 67 (1981), 1 - 13,

and 14 - 20. Other oxidation methods using nitric acid or TEMPO have also been employed; see, for example, U.S. Pat. Nos. 6,049,004,

5,599,977, and 6,498,269; WO 2008/021054 and J. Chem. Technol.

Biotechnol. 76 (2001), 186 - 190; J. Agr. Food Chem. 1 (1953), 779 - 783; J. Carbohydrate Chem. 21 (2002), 65 - 77; Carbohydrate Res. 337 (2002), 1059 - 1063; Carbohydrate Res. 336 (2001), 75 - 78; and Carbohydrate Res. 330 (2001), 21 - 29. However, these processes suffer from economic shortcomings resulting from, among other matters, process yield limitations, low conversion rates, and limited selectivity due to

shortcomings in the performance of existing catalysts. Until recently, none of the catalysts or the processes employing them have been used industrially for the selective oxidation of glucose-containing carbohydrates to manufacture specialty or industrial carboxylic acids or derivatives thereof. [0008] Alternatively, Au-Pt and Au-Pd bimetallic catalysts have been proposed for the base-free selective aerobic catalytic oxidation of glucose to glucaric acid (US 2011/0306790 A1 ; Zhang, Z. and Huber, G.W., Chem. Soc. Rev. 57 (4) (2018), 1351 - 1390, in particular pp. 1368 - 1370; Derrien, E. et al. , Ind. Eng. Chem. Res. 56 (45) (2017), 13175 - 13189; Potrzebowska, N. et al., Journee de Printemps 2017 de la SCF Rhone Alpes, poster presented 15 June 2017). The method of preparation of the bimetallic catalysts, the support material for the Au-Pt bimetallic nanoparticles, and the metal molar ratios have a strong influence on the activity and the maximum yield of glucaric acid. The Au-Pt/Zr02 catalyst with a molar ratio of Au/Pt = 1 provides a 50% yield of glucaric acid at complete conversion of glucose and gluconic acid at 100 °C and under 4 MPa air, using a glucose/metal ratio of 80. The catalyst was stable upon sequential recycling in a batch reactor and in long-term use in a continuous reactor.

[0009] Further, ultrasonication has been employed during the synthesis of

unsupported and supported metallic nanoparticles, including Au-Pt and Au-Pd bimetallic particles (Takatani, H. et al., Rev. Adv. Mater. Sci. 5(3) (2003), 232 - 238; Bhowmik, T. et al., RSC Adv. 5(48), (2015),

38760 - 38773; Zhang, G.H. et al., Mater. Res. Innov. 11(4) (2007),

201 - 203; Mizukoshi, Y. et al., Langmuir 15(8) (1999), 2733 - 2737;

Angelucci, C.A. et al., Electrochim. Acta 52(25) (2007), 7293 - 7299;

Fujimoto, T. et al., International Conference on Solid-Solid Phase

Transformations (PTM 99), Kyoto, Japan, May 24 - 28, 1999, published in The Japan Institute of Metals Proceedings, Vol. 12 (1999) (JIMIC-3), Solid - Solid Phase Transformations, Koiwa, M. et al. (ed.), pp. 361 - 364).

[0010] There remains a need for new, industrially scalable catalysts for the

selective and commercially meaningful conversion of a primary hydroxyl group to a carboxyl group of compositions comprising a primary hydroxyl group and at least a secondary hydroxyl group. Desirably, there is the need to convert biorenewable materials such as, for example,

carbohydrates or polyols, to specialty or industrial carboxylic acids and derivatives thereof, and more particularly, e.g., to convert glucose (derived from starch, cellulose or sucrose) to important chemicals such as glucaric acid and derivatives thereof.

Invention

[0011] The present invention is directed generally to a process for forming a catalyst composition comprising the following steps:

(a) combining at least one precursor of at least one metal and a solid support in a solvent;

(b) subjecting the mixture of step (a) to ultrasonication and/or microwaving;

(c) subjecting the mixture of step (b) to a reducing agent; and

(d) isolating the catalyst composition.

[0012] The present invention is also directed generally to a process for forming a catalyst composition comprising the following steps:

(a) combining at least one precursor of at least one metal and a colloid stabilizer in a solvent;

(b) subjecting the mixture of step (a) to a reducing agent;

(c) subjecting the mixture of step (b) to ultrasonication and/or microwaving;

(d) adding a solid support to the mixture of step (c);

(e) isolating the catalyst composition.

[0013] The present invention is further directed generally to a process for forming a catalyst composition comprising the following steps:

(b) subjecting the mixture of step (a) to ultrasonication and/or microwaving;

(c) subjecting the mixture of step (b) to a reducing agent; (d) adding a solid support to the mixture of step (c);

(e) isolating the catalyst composition.

[0014] Moreover, the present invention is directed to a catalyst composition

obtainable by employing the processes of the invention.

[0015] The present invention is also directed to a catalyst composition useful for the selective conversion of a primary hydroxyl group of compositions comprising a primary hydroxyl group and at least a secondary hydroxyl group to a carboxyl group wherein the catalyst composition comprises at least two metals.

[0016] The present invention is further directed to a process for preparing glucaric acid or derivatives thereof comprising reacting glucose with a source of oxygen in the presence of a catalyst composition according to the invention.

[0017] Other objects and features will become apparent and/or will be pointed out hereinafter.

Embodiments

[0018] The catalyst compositions of the present invention are particularly useful in the selective oxidation of a primary alcohol to a carboxyl in compositions comprising the primary hydroxyl (alcohol) group and at least a secondary hydroxyl (alcohol) group. In such compositions, also aldehyde groups may be present which are also selectively oxidized to a carboxyl. High conversion and selectivity, coupled with unexpectedly high yield, results from the use of the catalysts of the present invention. Conversion of carbohydrates and, more particularly, glucose and derivatives thereof to oxidation products such as glucaric acid and derivatives thereof is especially efficacious employing the catalysts of the present invention.

[0019] The catalyst compositions of the present invention comprise at least one metal, preferably at least two metals. [0020] The metal/metals is/are preferably selected from the group consisting of Au, Pt, Pd, Cu, Fe, Ag, and Co, more preferably from the group consisting of Au, Pt, and Pd. One or more of said metals may be employed in the catalyst compositions of the invention. Most preferred catalyst

compositions comprise Au and Pt, or Au and Pd, or Au and Pt and Pd, or Au and Cu, or Au and Ag, or Pt and Cu, or Pt and Co, or Pt and Fe, or Pt and Ag, or Pd and Ag as the metals. Especially preferred catalyst compositions comprise Au and Pt, or Au and Pd, or Au and Pt and Pd as the metals.

[0021] These catalysts are heterogeneous, solid-phase catalysts.

[0022] In various embodiments, at least one metal is present at a surface of a support (i.e., at one or more surfaces, external or internal). Suitable catalyst solid supports include carbon, carbon nitride, metal oxides and mixed metal oxides. Preferred solid supports include carbon materials (such as activated carbon, surface treated carbon, carbon nanofiber, carbon nanotube, multiwall carbon nanotube, graphene), zirconias, titanias, cerias, silicas, aluminas (such as passivated aluminas or coated aluminas), magnesias, zinc oxides, hydrotalcites, zeolites,

montmorillonites, and modifications, mixtures or combinations thereof. Particularly preferred solid support materials include carbon, zirconium dioxide, titanium dioxide, and cerium dioxide. Preferred support materials may be modified using methods known in the art such as heat treatment, acid treatment, steam treatment or by the introduction of a dopant

(e.g., metal-doped titanium dioxide or metal-doped zirconias such as tungstated zirconia). The catalyst support may be treated so as to promote the preferential deposition of the metals on the outer surface of the support so as to create a shell type catalyst. The supports may be in a variety of form such as powders, pellets, spheres, extrudates.

[0023] In the most preferred catalyst compositions, the gold : platinum or the gold : palladium molar ratio may vary, for example, from 100 : 1 to 1 : 10, from 50 : 1 to 1 : 8, from 10 : 1 to 1 : 5, or more preferably from 5 : 1 to 1 : 5. More preferably still, the gold : platinum or the gold : palladium molar ratio may vary, for example, from 3 : 1 to 1 : 2. Even more

preferably, the molar ratio of gold : platinum or gold : palladium is in the range of 1.5 : 1 to 1 : 2.

[0024] Catalyst performance in general is in significant part dependent upon the degree of uniformity of dispersion of the metals on the support. The catalyst compositions of the present invention may be produced by deposition procedures that are principally known in the art including, but not limited to, wet impregnation (Wl), ion-exchange, colloidal

method (CM), incipient wetness impregnation (I Wl) and deposition- precipitation employing urea (DPU) (for the Wl method see e.g.: Derrien, E., Mounguengui-Diallo, M., Perret, N., Marion, P., Pinel, C., Besson, M., Ind. Eng. Chem. Res. 56 (45) (2017), 13175 - 13189; for the CM method see e.g.: Villa, A., Wang, D., ShengSu, D., Prati, L, Chem. Cat.

Chem. 1 (2009), 510 - 514; for the DPU method see e.g.: Hugon, A., Delannoy, L., Krafft, J., Louis, C., J. Phys. Chem. C 114 (2010),

10823 - 10835).

[0025] In various embodiments, a uniform dispersion can be effected by forming a heterogeneous slurry of the support in combination with one or more solubilized metal constituents (herein also referred to as metal precursors). In certain embodiments, the supports may be initially dispersed in a liquid such as water. Thereafter, in such embodiments, the one or more solubilized metal precursors may be added to the slurry containing the support. The heterogeneous mixture of solid and liquids can then be stirred, mixed and/or shaken to enhance the uniformity of dispersion of the catalyst, which, in turn, enables the more uniform deposition of metals on the surface of the support upon removal of the liquids and additional treatments as may be needed and more fully described hereinafter.

[0026] In further embodiments, a uniform dispersion can be effected by first

forming a homogeneous solution of one or more solubilized metal precursors in combination with at least one colloid stabilizer. Thereafter, in such embodiments, the one or more solubilized metal precursors may be converted to the respective metals, followed by adding the support to the obtained slurry of metal particles which are stabilized by the colloid stabilizer. The heterogeneous mixture of solid and liquids can then be stirred, mixed and/or shaken to enhance the uniformity of dispersion of the catalyst, which, in turn, enables the more uniform deposition of metals on the surface of the support upon removal of the liquids and additional treatments as may be needed and more fully described hereinafter.

[0027] Embodiment 1 = Wl method

[0028] In one embodiment, the metal component of the catalyst compositions of the present invention is typically added to the solid support (that is suspended in a solvent) as one or more solubilized metal precursors to enable the formation of a uniform suspension.

[0029] Ultrasonication and/or microwaving is (are) then applied to the suspension.

Ultrasonication and microwaving positively affect the structure of the catalyst active phase. Employing such catalyst in the oxidation of glucose using molecular oxygen as the oxidant brings about enhanced yield of glucaric acid. Microwaving also improves (enhances) the loading of the metal precursor(s) to the support. A reducing agent is then added to the suspension in order to create metal nanoparticles which are uniformly deposited onto the support. The obtained catalyst composition is isolated, followed by washing and drying.

[0030] Typically, the solvent is selected from at least one of the group consisting of water, alcohols, and carboxylic acids, such as acetic acid.

[0031] The solvent is generally incapable of acting as reducing agent. Therefore, the solvent and the reducing agent differ generally from each other.

[0032] Besides, the solvent is generally incapable of acting as colloid stabilizer.

More broadly, in Wl method of present concern, no colloid stabilizer is involved in general.

[0033] In various embodiments, the concentration of the support in the

suspension can be in the range of about 1 to about 100 g of solid/liter of suspension, and in other embodiments the concentration can be in the range of about 2 to about 20 g of solid/liter of suspension.

[0034] In various embodiments, the concentration of metal precursor in the

suspension can be in the range of about 0.1 to about 100 g of metal precursor/liter of suspension, and in other embodiments the concentration can be in the range of about 2 to about 20 g of metal precursor/liter of suspension.

[0035] For example, in various embodiments, the metal precursor is provided to the suspension of the solid support as a halogenometallic acid or salts thereof, as a metal chloride, as a metal nitrate, or a metal acetate.

Preferably, precursors are selected from the group consisting of, for example, tetrachloroauric acid (HAuCU), hexachloroplatinic acid (FhPtCle), palladium chloride (PdC ) and hexachloropalladic acid potassium salt (K₂PdCI₆).

[0036] Upon creation of a well dispersed, heterogeneous mixture of metal

precursor and support in the solvent, a reducing agent is added to the suspension to form metal nanoparticles which then deposit on the surface of the support.

[0037] In certain embodiments, if two or more metals are employed in the catalyst compositions of the present invention, alloys of said metals may form at the reduction step.

[0038] Ultrasonication frequency employed in the process of the invention is in a range of from 16 to 500 kHz, preferably of from 17 to 200 kHz, and ultrasonication energy is in a range of from 0.1 to 1 ,000 W/cm², preferably from 5 to 150 W/cm².

[0039] Microwave frequency employed in the process of the invention is in a

range of from 0.5 to 10 GHz, preferably of from 0.8 to 3 GHz, and microwave energy in a range of from 0.5 to 100 W/cm³, preferably from 0.5 to 10 W/cm³.

[0040] Ultrasonication of the suspension is conducted at temperatures in a range of from 0 °C to 90 °C, preferably 20 °C to 70 °C. Microwaving of the suspension is conducted at temperatures in a range of from 0 °C

to 200 °C, preferably 30 °C to 150 °C, and pressures of from 0.1 to 3 MPa.

[0041] Ultrasonication of the suspension are conducted in a period ranging from 0.05 to 10 hours, preferably 0.5 to 5 hours, most preferably 0.5 to 3 hours. Ultrasonication and/or microwaving of the suspension are conducted in a period ranging from 0.001 to 1 hour, preferably 0.005 to 0.5 hours, most preferably 0.01 to 0.1 hours. Ultrasonication and microwaving may be employed individually, successively or at the same time in the processes of the present invention.

[0042] Suitable reducing agents include any reducing agent that is suitable to reduce the metal ions of the metal precursor to the respective metal.

Preferably the reducing agent is selected from the group consisting of NaBH₄, ethylene glycol, hydrogen, hydrazine, NaBH₄ and hydrogen, urea and hydrogen. NaBH₄ or NaBH₄ and hydrogen is preferred.

[0043] Like the solvent, the reducing agent is generally incapable of acting as colloid stabilizer. As already mentioned, in Wl method of present concern, no colloid stabilizer is involved in general.

[0044] Due to the low hydrolytic stability of aqueous solutions of NaBH₄ such

solutions are preferably freshly prepared before using them in the reduction reaction.

[0045] The molar ratio reducing agent : metal is typically in the range of from

20 : 1 to 1 :1 , preferably 15 : 1 to 3 : 1.

[0046] The reduction reaction in the liquid phase is typically conducted at

temperatures in a range of from -10 °C to 30 °C, preferably 0 °C to 15 °C, and pressures of from 0.01 to 1 MPa.

[0047] The reduction reaction in the liquid phase typically is conducted during a period ranging from 0.01 to 10 hours, preferably from 0.1 to 3 hours. The reducing agent may be added to the suspension all at once in the beginning of the reduction reaction or preferably added gradually during the reduction reaction. [0048] The obtained catalyst composition in the form of metal nanoparticles deposited at the surface of the support can typically be isolated by filtration or other suitable methods, such as centrifugation, followed by repeated washing with solvent and drying.

[0049] The mean size (determined by X-ray diffraction and/or transmission

electron microscopy (TEM)) of metal nanoparticles deposited at the surface of the support ranges from 0.5 to 50 nm, preferably 1 to 10 nm.

[0050] A further embodiment encompasses further reduction of metal

nanoparticles deposited at the surface of the support by molecular hydrogen under pressure. Such reduction reaction in the gas phase is typically conducted at temperatures in a range of from 100 °C to 800 °C, preferably 250 °C to 400 °C. The reduction reaction in the gas phase typically is conducted during a period ranging from 1 to 10 hours, preferably from 3 to 6 hours.

[0051] Total metal loading of the catalyst composition is in a range of from 0.1 to 20 % by weight, preferably from 1 to 10 % by weight, based on the total weight of the catalyst composition.

[0052] In a particularly preferred embodiment, the metals are Au and Pt in a

molar ratio of Au/Pt of from 0.6 to 1.5, the solid support is Zr0₂, the reducing agent is NaBH₄, sonication energy is in a range of from 5 to 100 W/cm², and sonication time is in a range of from 0.5 to 5 hours.

[0053] Embodiment 2 = CM method

[0054] In a further preferred embodiment, the metal component of the catalyst compositions of the present invention is typically added to a colloid stabilizer (that is dissolved or dispersed in a solvent) as a solubilized constituent (also referred to as metal precursor).

[0055] In one embodiment, ultrasonication and/or microwaving is (are) applied to the solution of of metal precursor and colloid stabilizer, followed by addition of a reducing agent to the thus obtained mixture to form metal nanoparticles. After acidification of the obtained suspension, a solid support is added, onto which the formed metal nanoparticles will deposit, followed by isolation of the obtained catalyst composition, washing and drying.

[0056] In another embodiment, reducing agent is added to the solution of metal precursor and colloid stabilizer, followed by ultrasonication and/or microwaving. After acidification of the obtained suspension, a solid support is added, onto which the formed metal nanoparticles will deposit, followed by isolation of the obtained catalyst composition, washing and drying. Acidification of the suspension is conducted such to effect a pH falling below the point of zero charge (PZC) of the solid support.

[0057] Typically, the solvent is selected from at least one of the group consisting of water, alcohols, and carboxylic acids, such as acetic acid.

[0058] The solvent is generally incapable of acting as reducing agent. Therefore, the solvent and the reducing agent differ generally from each other.

[0059] Besides, the solvent is generally incapable of acting as colloid stabilizer.

Therefore, the solvent and the colloid stabilizer differ generally from each other.

[0060] For example, in various embodiments, the metal precursor is provided to the solution of the colloid stabilizer as a halogenometallic acid or salts thereof, as a metal chloride, as a metal nitrate, or a metal acetate.

Preferably, precursors are selected from the group consisting of, for example, tetrachloroauric acid (HAuCU), hexachloroplatinic acid (H2PtCl6), and hexachloropalladic acid potassium salt (K2PdCl6).

[0061] A colloid stabilizer in the context of the present invention is an additive which stabilizes the lyophobic colloid (sol) of metal nanoparticles and prevents an uncontrolled sol/gel passage or coagulation of the sol. The colloid stabilizer may be added during or after the preparation of the colloid of metal nanoparticles. The colloid stabilizer may encompass (i) lyophilic protective colloids such as gum, gelatin, or Agar - Agar or (ii) water-soluble macromolecules such as polyvinyl alcohol or

polyvinylpyrrolidone. [0062] Preferably, the colloid stabilizer is selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, ionically modified starches (such as starches modified by dry heating with an ionic gum, as notably described in Cereal Chemistry, 79(5):601-606, September 2002), water- soluble starches (such as starches that have been subjected to an alcoholic-alkaline treatment, as notably described in J. Food Sci. Technol., 51 (3): 601-605, March 2014), starch ethers, polyacrylic acid, thiols, such as alkanethiols, 2-phenylethanethiol, 4-mercaptophenol, 4- aminothiophenol, amines, such as lysine or oleylamine, sodium citrate, tetrakis(hydroxymethyl)phosphonium chloride (THPC), cellulose

derivatives (such as carboxymethyl cellulose or water-soluble cellulose), ethers (such as hydroxyethyl cellulose (HEC)), natural gums, gelatin and synthetic polymers (such as styrene acrylic acid and styrene maleic acid). Polyvinyl alcohol is the preferred colloid stabilizer.

[0063] In various embodiments, the concentration of colloid stabilizer in the

solution can be in the range of about 0.1 to about 20 g of colloid

stabilizer/liter of solution, and in other embodiments the concentration can be in the range of about 1 to about 5 g of solid/liter of solution.

[0064] In various embodiments, the concentration of metal precursor in the

solution can be in the range of about 0.1 to about 100 g of metal precursor /liter of solution, and in other embodiments the concentration can be in the range of about 0.5 to about 5 g of solid/liter of solution.

[0065] The weight ratio colloid stabilizer : metal is typically in the range of from 3 : 1 to 0.5 : 1 , preferably, 2 : 1 to 1 : 1.

[0066] Suitable reducing agents include any reducing agent that is suitable to reduce the metal ions of the metal precursor to the respective metal.

Preferably the reducing agent is selected from the group consisting of NaBH₄, ethylene glycol, hydrogen, hydrazine, NaBFU and hydrogen, urea and hydrogen. NaBH₄ or NaBH₄ and hydrogen is preferred.

[0067] The reducing agent is generally incapable of acting as colloid stabilizer, and vice-versa, i.e. the above described colloid stabilizer is generally incapable of acting as reducing agent. Therefore, the reducing agent and the colloid stabilizer differ generally from each other.

[0068] The molar ratio reducing agent : metal is typically in the range of from 20 : 1 to 1 :1 , preferably 15 : 1 to 3 : 1.

[0069] The reduction reaction in the liquid phase is typically conducted at

temperatures in a range of from -10 °C to 30 °C, preferably 0 °C to 15 °C, and pressures of from 0.01 to 1 MPa during a period ranging from 0.01 to 10 hours, preferably from 0.1 to 3 hours. The reduction reaction in the gas phase is typically conducted at temperatures in a range of from 100 °C to 800 °C, preferably 250 °C to 400 °C during a period ranging from 1 to 10 hours, preferably from 3 to 6 hours.

[0070] Upon creation of a homogeneous mixture of metal precursor and colloid stabilizer in the solvent, either a reducing agent is added to the solution to form metal nanoparticles which, for activation, are subjected to sonication and/or microwaving, or the said homogeneous mixture is immediately subjected to sonication and/or microwaving, followed by addition of the reducing agent.

[0071] Ultrasonication frequency employed in the process of the invention is in a range of from 1 to 500 kHz, preferably of from 5 to 50 kHz, and

ultrasonication energy is in a range of from 0.1 to 1 ,000 W/cm², preferably from 5 to 150 W/cm².

[0072] Microwave frequency employed in the process of the invention is in a range of from 1 to 10 GHz, preferably of from 2 to 5 GHz, and microwave energy in a range of from 0.1 to 100 mW/cm², preferably from 1 to 10 mW/cm³.

[0073] Ultrasonication of the suspension is conducted at temperatures in a range of from 0 °C to 90 °C, preferably 20 °C to 70 °C, and pressures of from 0.01 to 1 MPa. Microwaving of the suspension is conducted at

temperatures in a range of from 0 °C to 200 °C, preferably 30 °C to 150 °C, and pressures of from 0.1 to 3 MPa. [0074] Ultrasonication and/or microwaving of the suspension are conducted in a period ranging from 0.01 to 10 hours, preferably 0.5 to 5 hours, most preferably 1 to 3 hours. Ultrasonication and microwaving may be

employed individually, successively or at the same time in the processes of the present invention.

[0075] The suspension of metal nanoparticles obtained by either embodiment is acidified to a pH of less than 3, preferably less than 2. A solid support is then added. The metal nanoparticles deposit on the surface of the support.

[0076] In various embodiments, the concentration of the support in the

suspension can be in the range of about 1 to about 100 g of solid/liter of suspension, and in other embodiments the concentration can be in the range of about 5 to about 25 g of solid/liter of suspension.

[0077] The obtained catalyst composition in the form of metal nanoparticles

deposited at the surface of the support can typically be isolated by filtration or other suitable methods, such as centrifugation, followed by repeated washing with solvent and drying.

[0078] The mean size (determined by X-ray diffraction and/or transmission

[0079] Total metal loading of the catalyst composition is in a range of from 0.1 to 20 % by weight, preferably from 1 to 5 % by weight, based on the total weight of the catalyst composition.

[0080] In a particularly preferred embodiment, the metals are Au and Pt in a

molar ratio of Au/Pt of from 0.6 to 1.5, the colloid stabilizer is polyvinyl alcohol, the solid support is Zr0₂, the reducing agent is NaBH₄, sonication energy is in a range of from 5 to 100 W/cm², and sonication time is in a range of from 0.5 to 5 hours.

[0081] Glucaric acid from glucose

[0082] Glucose is effectively converted to glucaric acid in high yield by reacting glucose with oxygen (as used herein, oxygen can be supplied to the reaction as air, oxygen-enriched air, oxygen alone, or oxygen with other constituents substantially inert to the reaction) in the presence of the catalyst compositions of the present invention and in the absence of added base according to the following reaction:

[0083]

glucaric acid

[0084] Intermediates on the path from glucose to glucaric acid include gluconic acid and guluronic acid.

[0085] Conducting the oxidation reaction in the absence of added base and in the presence of the catalyst compositions of the present invention does not lead to significant catalyst poisoning effects and oxidation catalyst selectivity is maintained. In fact, catalytic selectivity can be maintained to attain glucaric acid yield in excess of 60 %, even 65% and, in some embodiments, attain yields in excess of 70% or higher. The absence of added base advantageously facilitates separation and isolation of the glucaric acid and its lactones, thereby providing a process that is more amenable to industrial application, and improves overall process economics by eliminating a reaction constituent. The "absence of added base" as used herein means that base, if present (for example, as a constituent of a feedstock), is present in a concentration which has essentially no effect on the efficacy of the reaction (i.e., the oxidation reaction is being conducted essentially free of added base).

[0086] The initial pH of the reaction mixture is no greater than about 8. The initial pH of the reaction mixture is the pH of the reaction mixture prior to contact with oxygen in the presence of an oxidation catalyst. It is expected that the pH of the reaction mixture after oxygen contact will vary as the reaction proceeds. It is believed that as the concentration of the glucaric acid increases (as the reaction proceeds) the pH will decrease from the initial pH.

[0087] The process of producing glucaric acid or derivatives thereof from

carbohydrate such as glucose can be conducted with the catalysts of the present invention in the essential absence of nitrogen as an active reaction constituent. Typically, nitrogen is employed in known processes as an oxidant such as in the form of nitrate, in many instances as nitric acid. The use of nitrogen in a form in which it is an active reaction constituent, such as nitrate or nitric acid, results in the need for NOx abatement technology and acid regeneration technology, both of which add significant cost to the production of glucaric acid from these known processes, as well as providing a corrosive environment which may deleteriously affect the equipment used to carry out the process. By contrast, for example, in the event air or oxygen enriched air is used in the oxidation reaction of the present invention as the source of oxygen, the nitrogen is essentially an inactive or inert constituent. Thus, for example, an oxidation reaction employing air or oxygen-enriched air is a reaction conducted essentially free of nitrogen in a form in which it would be an active reaction constituent.

[0088] Generally, the temperature of the oxidation reaction mixture is at least about 40 °C, more typically 80 °C, or higher. In various embodiments, the temperature of the oxidation reaction mixture is from about 40 °C to about 150 °C, from about 60 °C to about 150 °C from about 70 °C to about 150 °C, from about 70 °C to about 140 °C, or from about 80 °C to about 140 °C.

[0089] Typically, the partial pressure of oxygen is at least 100 kPa, at least

175 kPa, at least 275 kPa, or at least 400 kPa. In various embodiments, the partial pressure of oxygen is up to 7,000 kPa, or more typically in the range of from 100 kPa to 3,500 kPa.

[0090] The oxidation reaction is typically conducted in the presence of a solvent to glucose. Solvents suitable for the oxidation reaction include water and weak carboxylic acids such as acetic acid. Utilization of weak carboxylic acid as a solvent adds cost to the process which cost, as a practical matter, must be balanced against any benefits derived from the use thereof. Thus, suitable solvents for the present invention include water, mixtures of water and weak carboxylic acid, or weak carboxylic acid. The catalyst compositions of the present invention remain stable in the presence of the solvent.

[0091] Glucose concentrations employable in the oxidation process of the

invention range from 1 to 500 g/liter, preferably 40 to 250 g/liter.

[0092] The various embodiments, the molar ratio of glucose to employed metal ranges from 250 : 1 to 20 : 1 , preferably from 150 : 1 to 50 : 1.

[0093] Oxidation reaction times range from 0.5 to 48 hours, preferably from 1 to 10 hours.

[0094] In general, the oxidation reaction can be conducted in a batch, semi-batch, or continuous reactor design using fixed bed reactors, trickle bed reactors, slurry phase reactors, moving bed reactors, or any other design that allows for heterogeneous catalytic reactions. Examples of reactors can be seen in Chemical Process Equipment - Selection and Design, Couper et al. , Elsevier, Amsterdam, 1990. It should be understood that glucose, oxygen, any solvent, and the oxidation catalyst may be introduced into a suitable reactor separately or in various combinations.

[0095] The reaction product of the oxidation step will, as described above,

contain glucaric acid in considerable and heretofore unexpected fraction, but may also contain derivatives thereof, such as glucarolactones. These glucarolactones, like glucaric acid, constitute a hydrodeoxygenation substrate which is particularly amenable to the production of adipic acid. Glucarolactones which may be present in the reaction mixture resulting from the oxidation step include mono and di-lactones such as D-glucaro- 1 , 4-lactone, D-glucaro-6, 3-lactone, and D-glucaro-1 , 4:6, 3-dilactone. The term“glucaric acid yield” as used herein shall denote the molar ratio of reaction products glucaric acid and its lactones : employed glucose. [0096] Byproducts formed during the oxidation process include compounds created by“over oxidation” of glucose to glucaric acid intermediates, such as 2-ketogluconic acid, 5-ketogluconic acid, arabinaric acid, tartaric acid, formic acid, glyceric acid, tartronic acid, glycolic acid, glyoxylic acid, oxalic acid, and carbon dioxide.

[0097] Glucaric acid produced in accordance with the above may be converted to various other glucaric acid derivatives, such as salts, esters, amides, ketones, and lactones. Methods to convert carboxylic acids to such derivatives are known in the art, see, for example, L.G. Wade, Organic Chemistry, 9th ed., Pearson, London, 2016.

[0098] Having described the invention in detail, it will be apparent that

modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

[0099] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[00100] The following non-limiting examples are provided to further illustrate the present invention.

[00101] Examples

[00102] Raw materials:

HAuCL was purchased from Alfa Aesar (hydrogen tetrachloroaurate (III) hydrate 99.9%)

H2PtCl6 was purchased from Alfa Aesar (99.9%)

Zr0₂, tradename: XZO, grade: 632/18, was purchased from Mel

Chemicals, Inc.

NaBH₄ was purchased from Acros Organics

Ethylene glycol (EG) was purchased from Sigma Aldrich (99.8%)

Polyvinyl alcohol (PVA), weight average molecular mass 13.000 to 23.000, 98% hydrolyzed, was purchased from Sigma Aldrich

[00103] Catalyst characterization methods:

ICP-OES (Inducted Coupled Plasma - Optical Emission Spectroscopy) was conducted using an Activa M instrument from Horiba Scientific. Prior to the analysis, catalysts were solubilized in a mixture of H2S0₄ and HNO3 at 250 - 300 °C, and then in aqua regia at 150 - 200 °C.

XRD (X-ray diffraction) patterns were recorded on a D8 Advance A25 diffractometer (Bruker) using a Cu K-a source. The crystalline phases were identified by reference to the JCPDS files, and the average crystallite size of metallic nanoparticles was calculated from line broadening according to Scheme’s equation. The XRD diffraction patterns showed diffraction peaks of the (111) and (200) planes of the face-centered cubic (fee) gold and platinum lattices. When an alloy was formed, peaks are shifted to lower 2Q angles compared to those of Pt and to higher angles compared to those of Au, which could be correlated to an alloy formation. Using the 2Q of the (111) plane provided the lattice constant for the fcc-type Au-Pt alloy nanoparticles, which corresponds to a Au-Pt composition according to Vegard’s law.

TEM (Transmission Electron Microscopy) measurements were performed on a JEOL 2010 instrument with a LaB6 source operated at an

accelerating voltage of 200 kV. Samples were prepared by ultrasonic dispersion in ethanol. A drop of dispersed catalyst was deposited onto a carbon grid and the solvent was evaporated.

The surface chemical composition and oxidation states of Pt and Au in catalysts constituted of alloys as determined by XRD were analysed by using a hemispherical analyser with a Kratos Axis Ultra DLD spectrometer using a monochromated Al Ka source. XPS spectra in the Au 4f and Pt 4f regions were recorded, and the binding energies were referenced to the C1s line at 284.5 eV. The fitting procedure revealed the presence of Au°, Pt°, and a contribution characteristic of Pt²⁺.

[00104] Catalyst Testing Protocol

[00105] Catalyst (between 0.8 g and 4 g depending on metal loading) and 150 ml of a 0.25 molar solution of glucose in water were weighed into a reactor, and the reactor was closed. The glucose : metal molar ratio was set to 80 : 1. The reactor was pressurized with air to 4,000 kPa at room temperature. The reactor was then heated to 100 °C and maintained at 100 °C for 24 hours with agitation. After 24 hours, agitation was stopped and reactor was cooled to 40 °C. Pressure in the reactor was then slowly released. The suspension was removed from the reactor and centrifuged. The clear solution was diluted with deionized water and analyzed by ion- chromatography (IC) with amperometry & conductivity detection. Samples for IC analysis were prepared by adding to 0.1 ml of the clear solution 30 ml of water. Product yields were determined using a 850 Professional IC ion chromatography system equipped with a Pulsed Amperometry detector (supplier: Metrohm). The products were first separated on a Dionex CarboPac PA1 column and then quantified by amperometry detection through comparison with calibration standards.

[00106] Example 1 (Wl method)

[00107] 1 -A. In a vial, 6.13 ml of an aqueous solution of

HAuCL (containing 32.6 g/L gold) and 12.16 ml of an aqueous solution of htePtCle (containing 14.4 g/L platinum) were added to a suspension of 4.625 g Zr0₂ in deionized water (250 ml) under nitrogen flow. The suspension was shaken at room temperature for 30 min and then subjected to sonication or microwaving. An Elmasonic S 100/(H) ultrasonic bath (supplier: Elma Schmidbauer GmbH), operated at 37 kHz and a bath temperature of 37 °C or 70 °C was used for sonication. A Monowave 400 microwave synthesizer (supplier: Anton Paar), operated at 850 W, autogenous pressure and a temperature of 30 °C or 150 °C was used for microwaving. The resulting suspension was placed in a reactor equipped with an agitator and externally cooled (ice/water) with stirring. 0.73 g of NaBH₄ (reducing agent) dissolved in 50 ml deionized water were added dropwise with stirring during 0.83 hours. The resulting suspension was then filtered. The solid was dried in a 60 °C oven overnight under a dry nitrogen purge.

1 -B. The same procedure as in Example 1A was used with the exception that ethylene glycol (50 ml_, dissolved in 50 ml deionized water) was used as the reducing agent.

1 -C and 1-D. Optionally, the catalyst as per Example 1A was subjected to further reduction employing molecular hydrogen at temperatures of 300 °C or 500 °C. For this purpose, catalyst was loaded in a fixed bed glass reactor with Fh flow, temperature was raised at 2°C/min to 300 or 500 °C, maintained at 300 or 500 °C for 0.5 h, followed by cooling to room temperature and flushing with argon. Before removal from the reactor, catalyst was passivated during 0.5 h using 1 % oxygen in nitrogen.

[00108] Example 2 (CM method)

[00109] 2-A. In a vial, approximately 5.92 ml of an

aqueous solution of HAuCU (containing 0.296 g/L gold) and 12.16 ml of an aqueous solution of FtePtCle (containing 14.4 g/L platinum) were added to a solution of 483 mg PVA in deionized water (50 ml). The solution was shaken at room temperature for 30 min, 0.339 g of NaBH₄ (reducing agent) dissolved in 50 ml deionized water was added, and then the mixture was subjected to sonication or microwaving. An Elmasonic S 100/(H) ultrasonic bath (supplier: Elma Schmidbauer GmbH), operated at 37 kHz and a bath temperature of 37 °C was used for sonication. A Monowave

400 microwave synthesizer (supplier: Anton Paar), operated at 850 W, autogenous pressure and a temperature of 150 °C was used for microwaving. The resulting mixture was placed in a reactor equipped with an agitator, and 0.1 molar sulfuric acid was added to adjust the pH of the mixture to one (1). Zr0₂ (2.325 g) was added and the mixture stirred for 2 hours. The resulting suspension was then centrifuged and the supernatant was decanted. After residual liquid was removed using filter paper, the solid was dried in a 60 °C oven overnight under a dry nitrogen purge.

[00110] Comparative Examples

CE-1-A, CE-1-B, CE-1-C, CE-1-D, CE-2-A1 The same procedures as in Examples 1-A, 1-B, 1-C, 1-D and 2 -A were used, with the exception that ultrasonication and microwaving were omitted.

CE-2-A2 In an autoclave equipped with an agitator, 2.96 ml of an aqueous solution of HAuCL (containing 0.296 g/L gold) and 6.08 ml of an aqueous solution of H2PtCl6 (containing 14.4 g/L platinum) were added to a solution of 210 mg PVA and 50 mL EG in deionized water (100 ml). Zr0₂ (2.325 g) was added and the mixture stirred for 2 hours at 100 °C, 1 hour at 150 °C and 1 h at 200 °C. The resulting suspension was then cooled to room temperature and filtered. After residual liquid was removed using filter paper, the solid was dried in a 60 °C oven overnight under a dry nitrogen purge.

CE-3 (DPU method)

In a vial, 5.92 ml of an aqueous solution of HAuCL (containing 0.296 g/L gold) and 12.15 ml of an aqueous solution of H2PtCl6 (containing [Pt]

14.4 g/L wt% platinum) were added to a suspension of 4.650 g Zr0_{2 i}n deionized water (200 ml). To the resulting suspension 5.17 g urea was added, dissolved in 100 ml distilled water. The suspension was stirred at 80 °C for 16 h in absence of light.

The resulting suspension was filtered and the supernatant was decanted. After residual liquid was removed using filter paper, the solid was dried in a 60 °C oven overnight under a dry nitrogen purge.

[001 1 1] Catalyst testing results are compiled in Tables 1 - 4.

[001 12] Table 1. Catalyst testing results of Example 2 (CM method)

a) Metal loading of catalyst too low to allow alloy detection by XRD. b) No alloy detected, large Au particles. [001 13] Table 2. Catalyst testing results of Example 1 (Wl method)

[00114] Table 3. Comparative catalyst testing results of Example 1 (Wl method)

a) Au nanoparticles also detected [00115] Table 4. Comparative catalyst testing results (DPU method)

Claims

Claim 1. A process for forming a catalyst composition comprising the following steps:

(b) subjecting the mixture of step (a) to ultrasonication and/or microwaving;

(c) subjecting the mixture of step (b) to a reducing agent; and

(d) isolating the catalyst composition.

Claim 2. A process for forming a catalyst composition comprising the following steps:

(a) combining at least one precursor of at least one metal and a colloid

stabilizer in a solvent;

(b) subjecting the mixture of step (a) to a reducing agent;

(c) subjecting the mixture of step (b) to ultrasonication and/or microwaving;

(d) adding a solid support to the mixture of step (c);

(e) isolating the catalyst composition.

Claim 3. A process for forming a catalyst composition comprising the following steps:

(a) combining at least one precursor of at least one metal and a colloid

stabilizer in a solvent;

(b) subjecting the mixture of step (a) to ultrasonication and/or microwaving;

(c) subjecting the mixture of step (b) to a reducing agent;

(d) adding a solid support to the mixture of step (c);

(e) isolating the catalyst composition.

Claim 4. The process as claimed in claim 2 or 3, wherein the colloid stabilizer is selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, ionically modified starches such as starches modified by dry heating with an ionic gum, water-soluble starches such as starches that have been subjected to an alcoholic-alkaline treatment, starch ethers, polyacrylic acid, thiols, amines, sodium citrate, tetrakis(hydroxymethyl)phosphonium chloride (THPC), gelatin, natural gum, cellulose derivatives, natural gums, gelatin and synthetic polymers such as styrene acrylic acid and styrene maleic acid, and wherein the weight ratio colloid stabilizer : metal is preferably in the range of from 3 : 1 to 0.5 : 1 , more preferably from 2 : 1 to 1 : 1.

Claim 5. The process as claimed in any one of the preceding claims, wherein the metal(s) is (are) selected from the group consisting of Au, Pt, Pd, Cu, Fe, Ag, and Co, and wherein at least one of the metal(s) is preferably Au, Pt or Pd.

Claim 6. The process as claimed in any one of the preceding claims, employing precursors of at least two metals, and wherein the metals are preferably either Au and Pt, or Au and Pd, or Au and Pt and Pd, or Au and Cu, or Au and Ag, or Pt and Cu, or Pt and Co, or Pt and Fe, or Pt and Ag, or Pd and Ag.

Claim 7. The process as claimed in claim 6, wherein

- the metals are Au and Pt, and the molar ratio Au : Pt in the catalyst composition is from 10 : 1 to 1 : 5, preferably from 1.5 : 1 to 1 : 2, or

- the metals are Au and Pd, and the molar ratio Au : Pd in the catalyst composition is from 10 : 1 to 1 : 5, preferably from 1.5 : 1 to 1 : 2, or

- the metals are Au and Pt and Pd, and the molar ratio Au : (Pt+Pd) in the catalyst composition is from 10 : 1 to 1 : 5, preferably from 1.5 : 1 to 1 : 2.

Claim 8. The process as claimed in any one of the preceding claims, wherein the precursors are selected from the group consisting of halogenometallic acids and salts thereof, metal chloride, metal nitrates and metal acetates, and are preferably selected from the group consisting of tetrachloroauric acid, hexachloroplatinic acid, palladium chloride, and hexachloropalladic acid potassium salt.

Claim 9. The process as claimed in any one of the preceding claims, wherein the solid support is selected from the group consisting of carbon, carbon nitride, metal oxides and mixed metal oxides, and wherein metal oxides and mixed metal oxides are preferably selected from the group consisting of zirconias, silicas, titanias, cerias, aluminas, silicas, magnesias, zinc oxides, zeolites,

montmorillonites, hydrotalcite, and modifications, mixtures or combinations thereof.

Claim 10. The process as claimed in any one of the preceding claims, wherein the solvent is selected from the group consisting of water, alcohols, and carboxylic acids.

Claim 11. The process as claimed in any one of the preceding claims, wherein the mixture is subjected to ultrasonication at the step where it can be subjected to such a treatment.

Claim 12. The process as claimed in claim 11 , wherein ultrasonication frequency is in a range of from 1 to 500 kHz, preferably of from 5 to 50 kHz, and ultrasonication energy is in a range of from 0.1 to 1 ,000 W/cm², preferably from 5 to 150 W/cm².

Claim 13. The process as claimed in claim 11 or 12, wherein ultrasonication time is in a range of from 0.01 to 10 hours and sonication is conducted at temperatures in a range of from 0 °C to 90 °C, possibly from 0 °C to 50 °C.

Claim 14. The process as claimed in any one of the preceding claims, wherein the mixture is subjected to microwaving at the step where it can be subjected to such a treatment.

Claim 15. The process as claimed in claim 14, wherein microwave frequency is in a range of from 1 to 10 GHz and microwave energy in a range of from 0.1 to 100 mW/cm³.

Claim 16. The process as claimed in claim 14 or 15, wherein microwaving time is in a range of from 0.01 to 10 hours, and microwaving is conducted at

temperatures in a range of from 0 °C to 200 °C, possibly from 0 °C to 50 °C.

Claim 17. The process as claimed in any one of the preceding claims, wherein the reducing agent is selected from the group consisting of NaBH₄, ethylene glycol, hydrogen, hydrazine, NaBH₄ and hydrogen, urea and hydrogen,

and wherein the molar ratio reducing agent : metal is preferably in the range of from 20 : 1 to 1 :1 , more preferably from 15 : 1 to 3 :1.

Claim 18. The process as claimed in any one of the preceding claims, wherein employing precursors of at least two metals and wherein an alloy of employed metals is formed.

Claim 19. The process as claimed in any one of the preceding claims, wherein the metal loading of the catalyst composition is in a range of from 0.1 to 20 % by weight, preferably from 1 to 10 % by weight, based on the total weight of the catalyst composition.

Claim 20. The process as claimed in any one of claims 1 to 3, wherein the metals are Au and Pt in a molar ratio of Au/Pt of from 0.6 to 1.5, the solid support is Zr0₂, and the reducing agent is NaBH₄.

Claim 21. A catalyst composition obtainable by employing the process as claimed in any one of the preceding claims.

Claim 22. A process for preparing glucaric acid comprising reacting glucose with a source of oxygen in the presence of the catalyst composition as claimed in claim 21.

Claim 23. A process for preparing glucaric acid comprising reacting glucose with a source of oxygen in the presence of the catalyst composition prepared by the process according to any one of claims 1 to 20.

Claim 24. Use of glucaric acid prepared by the process according to claim 22 or 23 for the preparation of a glucaric acid derivative chosen from salts, esters, amides, ketones and lactones.