WO2008138865A1

WO2008138865A1 - A process for the partial oxidation of alcohols in water by direct alcohol fuel cells

Info

Publication number: WO2008138865A1
Application number: PCT/EP2008/055706
Authority: WO
Inventors: Paolo Bert; Claudio Bianchini; Giuliano Giambastiani; Andrea Marchionni; Alessandro Tampucci; Francesco Vizza
Original assignee: Acta S.P.A.
Priority date: 2007-05-09
Filing date: 2008-05-08
Publication date: 2008-11-20
Also published as: ITFI20070110A1

Abstract

This invention describes a process for the sustainable production of chemicals, in particular of carboxylic acids, ketones, keto-acids and hydroxy-acids through the partial oxidation of water solutions of alcohols and polyalcohols in direct alcohol fuel cells.

Description

A PROCESS FOR THE PARTIAL OXIDATION OF ALCOHOLS IN WATER BY DIRECT ALCOHOL FUEL CELLS

Field of the invention:

The present invention refers to the sustainable production of carboxylic acids, ketones, keto-acids and other oxygenates by the oxidation of alcohols and polyalcohols in electrochemical devices (fuel cells) capable of generating simultaneously electric energy.

State of the art

The sustainable oxidation of alcohols to carbonylic and/or carboxylic compounds (equations 1 and 2) is a target of primary and current importance for the Chemical

Industry. The traditional systems for the oxidation of the alcohol functional group make use of large quantities of toxic heavy metals such as chromium and manganese, thus generating enormous amounts of metal waste (Platinum Metal

Rev. 2003, 47, 27; R. A. Sheldon et al. Ace. Chem. Res. 2002, 35, 774).

Better results, in terms of environmental impact and selectivity can be obtained by aerobic oxidation in the presence of micro- or nano-structured heterogeneous catalysts based on noble metals like Ru, Pd, Pt, Ag o Au supported on either porous metal oxides or zeolites (K. Yamaguchi, N. Mizuno Angew. Chem. Int. Ed. Engl. 2002, 41, 4538; R. Lin et al. Catal. Lett. 2004, 93, 139; J. Shen et al. Chem. Commun. 2004, 2880; S. Campestrini et al. Chem Soc. Rev. 2005, 347, 825; G. J. Hutchings Science 2006, 311, 362). In many cases, the reactivity is limited to the oxidation of benzylic and allylic alcohols as generally occurs in homogeneous processes where Pd-based catalysts are prevalently employed (T. Privalov et al. Organometallics 2005, 24, 885; B. A. Steinhoff et al. J. Am. Chem. Soc. 2004, 126, 1 1268). While primary alcohols such as ethanol can be selectively oxidized to the corresponding carboxylic acid by heterogeneous catalysts based on supported metal oxides or on Au nanoparticles (C. H. Christensen et al. Angew. Chem Int. Ed. Engl. 2006, 45, 4648), the (chemo-, regio-) selectivity for the transformation of polyalcohols like 1 ,2-propanediol and glycerol, is generally low due to the many functional groups and the possibility of carbon-carbon bond cleavage. The selective catalytic systems for the oxidation of polyalcohols with oxygen are prevalently based on noble metals such as Au, Pd, Pt, often as mutual binary alloys or alloyed with other metals. Some examples of selective oxidation of glycerol and ethylene glycol are described in G. J. Hutchings et al. Chem Commun. 2002, 696; C. L. Bianchi et al. Catal. Today 2005, 102-103, 203; N. Dimitratos et al. J. MoI. Catal. A: Chemical 2006, 256, 21 ; H. Rimura et al. Appl. Catal. A: General 1993, 96, 217; J. Shen et al. Chem. Commun. 2004, 2880. The selective oxidation of alcohols and polyalcohols can be achieved also by means of electrochemical techniques described as in G. Palmisano et al. Adv. Synth. Catal. 2006, 348, 2033 where a series of primary and secondary alcohols are selectively oxidized to aldehydes and ketones, respectively, or in R. Ciriminna et al. Tetrahedron Lett. 2006, 47, 6993, where glycerol is oxidized to 1 ,3-dihydroxy acetone in the presence of a radical mediator such as TEMPO (2,2,6,6- tetramethylpiperidine-1 -yloxy). Examples of electrochemical oxidation of glycerol, ethylene glycol and 1 ,2-propanediol on electrocatalysts containing noble metals such as Pd and Pt are described in K. Matsuoka et al. Electrochim. Acta 2006, 51, 1085; L. Demarconnay et al. J. Electroanal. Chem. 2007, 601, 169; P. K. Shen et al. Electrochem. Commun. 2006, 184; P. Ocon et al. Electrochim. Acta 1987, 32, 387; M. J. Gonzalez et al. J. Phys. Chem. 1998, 102, 9881. The electrochemical oxidation of alcohols and polyalcohols can be also realized in direct alcohol fuel cells where, however, the goal is not the conversion of the alcohol into an oxidation product, but the obtainment of the maximum available electric energy which is achieved when the alcohol is completely oxidized to CO₂. A modern direct alcohol fuel cell (DAFC) consists of two electrodes made of a porous and conductive material separated by polymeric membrane permeable to ions. The membrane may exchange either cations (protons) or anions (hydroxyl groups). In Figure 1 is shown the functioning scheme of a DAFC with an anion- exchange polymeric electrolyte. Cells of the latter type are employed for the purposes of the present invention. In the DAFCs, both the anode and cathode reactions occur on catalysts (called electrocatalysts) constituted by highly dispersed metal particles of small dimensions, generally from 2 to 50 nanometers (10^"9 m) supported on porous and conductive materials, generally carbon blacks like Vulcan, Ketjen black or carbon nanotubes (Chan et al., J. Mater. Chem. 2004, 14, 505).

Most anode catalysts in DAFCs of the state-of-the-art consist generally of platinum or platinum alloys with other metals, noble or non noble, for example ruthenium and tin, where the percentage of platinum remains prevalent (C. Lamy et al. J. Power Sources 2002, 105, 283-296; C. Lamy et al. J. Appl. Electrochem. 2001 , 31, 799-809; C. Lamy et al. Topics in Catal. 2006, 40, 1 1 1 ). The high cost of platinum and the facile deactivation of Pt-based catalysts by carbon monoxide (CO), which is an intermediate specie along alcohol oxidation, account for the realization of DAFC catalysts devoid of platinum or containing very small amounts of this metal. Palladium, for example, has created notable interest as it is 50 times more abundant in nature with respect to platinum and has the capacity to promote the electrochemical oxidation of methanol under both acidic (H. L. Li et al., J. Solid State Chem., 2005, 178, 1996) and alkaline conditions. Catalysts derived from palladium supported on oxides of Ce, Ni, Co and Mn, act as electrocatalysts for the oxidation of alcohols like methanol, ethanol, ethylene glycol and glycerol (P. K. Shen et al., Electrochem. Commun., 2006, 8, 184-188; P. K. Shen et al. J. Power Sources 2007, 1 64, 527; C. Coutanceau et al. J. Power Sources 2005, 156, 14). An International Patent Application (PCT/EP2008/053714) has been recently filed where it is claimed the synthesis of anode electrocatalysts based on Ni-Pd and their use in fuel cells of the alkaline DAFC type fuelled with alcohols and polyalcohols. These catalysts are obtained by the spontaneous deposition of Pd onto composite materials based on nickel, zinc and phosphorus (Ni-Zn-P).

As previously said, the design and development of new catalysts has been so far aimed at preparing catalysts capable of promoting the complete oxidation of the fuel so as to obtain the maximum available energy delivered by the cell. For this reason, the partial oxidation of the fuel has been so far undesired and consequently no research has been directed towards the development of partial oxidation catalysts.

The Applicant is not aware of patents or scientific publications where it is claimed the use of fuel cells as devices for the selective transformation of alcohols into products containing the ketone, aldehyde and/or carboxylic acid functional groups by means of anode catalysts appropriately selected to reduce the Faradaic efficiency.

Summary of the Invention

The present invention refers to the simultaneous production of electric energy and chemical products (aldehydes, ketones, keto-acids, carboxylic acids, hydroxy- acids) derived from the partial oxidation of alcohols and polyalcohols in direct alcohol fuel cells (DAFC) with an electrolyte consisting of either an anion- exchange polymeric membrane or a solution of an alkaline hydroxide.

Description of the figures Figure 1 - Simplified functioning scheme of a fuel cell of the DAFC type used for the partial oxidation of alcohols and the concomitant production of electric energy.

Figure 2 - Polarization and power density curves of a cell fuelled with a water solution of ethanol (10 wt%) with the characteristics described in the cell example n° 1. Figure 3 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°.

1 for 12 hours at a cell potential of 0.4 V.

Figure 4 - Polarization and power density curves of a cell fuelled with a water solution of ethylene glycol (10 wt%) with the characteristics described in the cell example n° 2.

Figure 5 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°. 2 for 12 hours at a cell potential of 0.4 V.

Figure 6 - Polarization and power density curves of a cell fuelled with a water solution of glycerol (10 wt%) with the characteristics described in the cell example n° 3. Figure 7 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°.

3 for 12 hours at a cell potential of 0.4 V.

Figure 8 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°. 3 for 24 hours at a cell potential of 0.4 V.

Figure 9 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°.

3 for 24 hours at a cell potential of 0.2 V.

Figure 10 - Polarization and power density curves of a cell fuelled with a water solution of ethanol (10 wt%) with the characteristics described in the cell example n° 4.

Figura 1 1 - ¹³C(¹HJ NMR spectrum of the anode solution after a galvanostatic experiment carried out with a cell with the characteristics described in example n°.

4 for 10 hours at a cell potential of 0.4 V. Figure 12 - Polarization and power density curves acquired at a temperature of 80 °C in a cell with a MEA comprising a HYPERMEC™ Fe50-Co50 cathode, a Tokuyama A006 membrane and a Ni-Zn-P-Pd/Vulcan anode described in the International Patent Application PCT/EP2007/057518 (published as WO2008009742) fuelled with: glycerol 10 wt%; ethylene glycol 10 wt%; ethanol 10 wt%.

Detailed description of the present invention

The present invention allows for the realization of a process where, simultaneously to the generation of electric energy, alcohols and polyalcohols are selectively converted into partial oxidation products like carboxylic acids, aldehydes, ketones, keto-acids and hydroxy-acids. Such a process occurs in a direct alcohol fuel cell (DAFC) preferably equipped with an electrolyte constituted by an anion-exchange membrane or by a solution of an alkaline hydroxide such as NaOH or KOH. The Applicant has surprisingly discovered that, unlike Pt and Pt-Pd-based catalysts of the state-of-the-art (C. Lamy et al. Topics in Catal. 2006, 40, 1 1 1 ; C. Coutanceau et al. J. Power Sources 2005, 156, 14), the Pd-Ni-Zn-P catalysts have low or even no propensity to cleave carbon-carbon bonds in alkaline environment and therefore, while providing elevated power densities, they convert primary alcohols like ethanol or 1 -propanol selectively into the corresponding carboxylic acid and polyalcohols like ethylene glycol and glycerol into hydroxy-acids, ketoacids and/or di-acids. A comparable reactivity has been observed by the Applicant, preferably in alkaline media, by means of anode electrodes based on palladium, platinum or other noble metals of the state-of-the-art, like those reported in the patent DE 1254132 and in the International Patent Application PCT/EP2007/057518 (published as WO2008009742), prepared by the spontaneous deposition of a noble metal, for example palladium or platinum, on either nickel obtained by treatment of Ni-Al alloys with alkaline hydroxides or on nanostructured catalysts based on Fe-Co-Ni alloys, described in the European patent EP 1556916 (A2) 2006 and known with the trademark HYPERMEC™. Effective catalysts for the purposes of the present invention are also catalysts obtained by the plain reduction with ethylene glycol of palladium salts adsorbed onto conductive carbons (L.-J. Chen at al. J. Colloid Interface Sci. 2006, 297, 143), or by means of microwave irradiation (H. T. Zheng et al. J. Power Sources 2006, 163, 371 ) or by treatment with NaBH₄ (C. Xu et al. J. Power Sources 2007, 164, 527).

In the present case, the carboxylic acids produced are isolated as carboxylates of alkaline metals, generally sodium and potassium. For realizing the present invention, one can employ all the anode catalysts for fuel cells, and more in general for electrochemical cells, including those that are used in electrolytic processes, provided they are capable to promote the selective oxidation of the primary and secondary alcoholic functionalities to ketone, aldehyde or carboxylic acid groups. It is therefore the subject of the present invention, a process wherein are employed direct alcohol fuel cells comprising catalysts containing palladium supported onto various materials such as Ni-Zn-P phases, Raney nickel, porous carbons (Vulcan, Ketjen black) or carbon nanotubes, wherein said catalysts are able to promote the partial oxidation of alcohols and polyalcohols in alkaline environment, thus generating, depending on the alcohol used, current densities varying from 25 and 90 mW cm² at ambient temperature in self-breathing (passive) systems and from 160 to 210 mW cm² in active systems (1 bar O₂) at 80 °C. These latter values are reported for ethanol, ethylene glycol and glycerol (Figure 12) in the International Patent Application PCT/EP2008/053714 in which are described anode electrocatalysts based on Ni-Pd and their use in alkaline DAFCs. These catalysts are obtained by the spontaneous deposition of Pd on composite materials based on nickel, zinc and phosphorus (Ni-Zn-P). The current density values obtained with the Pd-based catalysts described above are comparable and even superior to the values generally reported for anode catalysts based on platinum in direct methanol fuel cells (C. Lamy et al. Topics in Catal. 2006, 40, 1 1 1 ; Q. Xin et al. J. Power Sources 2004, 126, 16). The specific power density data obtained in the course of the partial oxidation of some model substrates, like ethanol, ethylene glycol and glycerol, are reported in Figures 2, 4, 6, 10, and 12 which illustrate the corresponding DAFC performance. The fact that the anode catalysts in the examples herein described contain platinum or palladium does not exclude that catalysts based on other metals, provided they are able to promote the partial oxidation of alcohols and polyalcohols in direct fuel cells, can be employed to realize the processes and the DAFCs claimed in this patent application. In particular, similar results to those obtainable with the palladium- based catalysts can be envisaged with anode catalysts based on transition metals of the Groups 8, 9, 10, 12 and 12 of the Periodic Table of the Elements, provided they are used in DAFCs of the type described in Figure 1.

Examples of the processes claimed by the present invention are reported for the following conversions: ethanol to potassium acetate (3), ethylene glycol to potassium glycolate and potassium oxalates (4) glycerol to potassium glycerate, potassium tartronate and potassium oxalate (5). CH₃CHOH ► CH₃COOK + electricity (3)

KOH

electricity (4)

electricity (5)

For alcoholic substrates which can generate several oxidation products (see reactions 4 and 5), the Applicant has discovered that the selectivity can be controlled by means of the working time of the DAFCs and of the voltage and temperature of galvanostatic experiments.

The working scheme of a DAFC of the invention is shown in Figure 1. The DAFCs employed to demonstrate what is claimed in the present invention have been realized with cathode electrodes of the state-of-the-art, with commercially available anion-exchange membranes and with anode electrodes prepared according to known methods, some of which are described as follows. Method 1

Spontaneous deposition of a noble metal on micro- or nano-particles of non-noble metals To an aqueous suspension, containing a nickel salt, preferably nickel sulfate hexahydrate (NiSO₄-6H₂O), a zinc salt, preferably zinc sulfate eptahydrate (ZnSO₄-7H₂O), sodium citrate dihydrate (Na₃-citrato-2H₂0), ammonium chloride (NH₄CI), sodium hypophosphite hydrate (NaH₂PO₂-H₂O), is added a porous and conductive graphitic or amorphous carbon support, for instance Vulcan XC-72R or active carbon RDBA. The pH of the mixture is fixed to 10 by the addition of an aqueous solution of KOH and the suspension is heated to ca. 100 °C. for 2 hours, keeping constant the pH to 10 by adding aqueous KOH.

To this suspension, cooled to ambient temperature, is added a water solution containing KOH (30 g) and the temperature is increased to ca. 50 °C for 1 hour. The solid residue, called Ni-Zn-P/C, is filtered off, washed with abundant water and dried.

The solid obtained is suspended in water and a salt or a compound of a noble metal, for instance potassium tetrachloropalladate (K₂PdCI₄), hexachloroplatinic acid (H₂PtCI₆), ruthenium trichloride (RuCI₃) or iridium trichloride (IrCI₃), is slowly added to the suspension. The resulting product is filtered off, washed and stored wet.

Method 2

Spontaneous deposition of a noble metal on micro- or nano-particles of non-noble metals A water solution containing a nickel salt or a nickel compound, preferably nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O], a cobalt salt or a cobalt compound, preferably cobalt acetate tetrahydrate [Co(CH₃C0₂)₂-4H₂0] and a iron salt or a iron compound, preferably iron acetate [Fe(CH₃CO₂)₂] is added to a water suspension of a templating polymer of the state-of-the-art described in the European EP 1556916 (A2) 2006. The solid product obtained is filtered off, washed with water and dried. The dry solid is added to a suspension in acetone or in other organic solvents of a conductive and porous material based on amorphous or graphitic carbon, for example. Vulcan XC-72 or active carbon RDBA, just to mention but a few. The resulting product suspended in water is treated with a reducing agent of the state-of-the-art (NaBH₄ or NH₂NH₂), then filtered off, washed with water and dried. Alternatively, the resulting product can be reduced using a stream of hydrogen gas at a temperature between 300 and 800 °C.

The solid product obtained is suspended in water and a salt of a noble metal or a compound of a noble metal, for example palladium dichloride (PdCI₂), hexachloroplatinic acid (H₂PtCI₆) or iridium trichloride (IrCI₃), is added to the suspension under stirring. After 1 hour, the material is filtered off, washed with water, dried, then suspended in water and reduced with a reducing agent of the state-of-the-art (NaBH₄ or NH₂NH₂). The final product is filtered off, washed with water and dried. Method 3

Reduction of a salt of a noble metal adsorbed onto a conductive carbon

To a suspension of Vulcan XC-72R in ethylene glycol (EG), after sonication in a ultrasound bath for 20 minutes, is added slowly and under vigorous stirring a water solution containing a salt of a noble metal or a noble metal compound, preferably tetrachloropalladic acid (H₂PdCI₄), hexachloroplatininc acid (H₂PtCI₆) or iridium trichloride (IrCI₃). The pH of the suspension is fixed to 13.5 by the addition of a NaOH solution and the temperature is maintained at 140 °C for 3 hours. The product is filtered off, washed with abundant water and dried under vacuum to constant weight. Some examples of preparations of anode catalysts are described below. Example 1 PREPARATION OF AN ANODE CATALYST BASED ON NICKEL-ZINC- PHOSPHORUS-PALLADIUM

3.5 g of nickel sulfate hexahydrate (NiSO₄-6H₂O ), 2 g of zinc sulfate heptahydrate heptaidrate (ZnSO₄-7H₂O ), 8.5 g of basic sodium citrate dihydrate (Na₃- citrate-2H₂O), 5 g of ammonium chloride (NH₄CI) and 3 g of sodium hyphosphite hydrate (NaH₂PO₂-H₂O) are dissolved in 100 mL of water. The pH of the solution is fixed to 10 by adding 30 mL of a 30% water solution of KOH. To the green-blue resulting solution are added 5 g of Vulcan XC-72R.

The resulting suspension is heated to 100 °C. After some minutes, an intense effervescence is observed as a consequence of gas evolution and the suspension is maintained at 90 °C for 2 h at pH 10 by adding a 30% water solution of KOH. To this suspension, cooled to ambient temperature, are added 20 g of KOH. The temperature is maintained at 50 °C for 1 hour. The solid residue is filtered off and washed with water to pH 7, then it is filtered off, washed with water to neutrality and dried under vacuum at 40 °C to constant weight. Yield 6 g (Ni-Zn-P/C). Ni content = 10.2 wt%, Zn content = 0.51 wt%, P content = 0.27 wt% (ICP-AES and EDS analysis).

The solid obtained as described above is suspended in 500 mL of water and finely dispersed by means of a ultrasound probe for 30 minutes. To this suspension, under vigorous stirring, is slowly added (3 hours) at ambient temperature a solution containing 0.5 g of potassium tetrachloropalladate K₂PdCI₄ dissolved in 250 mL of water. At the end of this addition, the suspension is vigorously stirred for further 2 hours and the solid residue is filtered off, washed with water (4 x 100 mL) and stored wet.

Ni content = 8.71 wt%, Zn content = 0.51 wt%, P content = 0.27 wt%, Pd content = 2.79 wt% (ICP-AES and EDS analysis). Example 2 PREPARATION OF AN ANODE CATALYST BASED ON NICKEL-ZINC- PHOSPHORUS-PLATINUM

6 g of Ni-Zn-P/C (obtained following the procedure described in example 1 ) are suspended in 500 mL of water and finely dispersed by means of an ultrasound probe for 30 minutes. To this suspension, vigorously stirred, is slowly added (3 hours) at room temperature a solution containing 1.04 g of potassium hexachloroplatinate (K₂PtCI₆) dissolved in 200 mL of water. Once the addition is finished, the suspension is vigorously stirred for further 3 hours and the solid residue is filtered off, washed with water (4 x 100 mL) and stored wet. Ni content = 5.77 wt%, Zn content = 0.5 wt%, P content= 0.28 wt%, Pt content = 5.86 wt% (ICP-AES, EDS analysis). Example 3

PREPARATION OF AN ANODE CATALYST BASED ON IRON, COBALT, NICKEL AND PALLADIUM To a suspension containing 7 g of a known polymer (described in the European patent EP 1556916 (A2) 2006) in 440 mL of water and 87.5 mL of NaOH 1 M, finely dispersed with an ultrasound probe for 30 minutes, are added 3.18 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O], 3.18 g of cobalt acetate tetrahydrate [Co(CH₃CO₂MH₂O] and 2.54 g of iron acetate [Fe(CH₃CO₂)₂] dissolved in 200 mL of water and the resulting mixture is vigorously stirred at room temperature overnight. Then, the pH of the mixture is fixed to pH 7.5 by adding HCI 1 M and the red-brick precipitate formed is filtered off, washed with water (4 X 50 mL) and dried under vacuum at 70 °C up to constant weight. Yield = 8 g. Ni content = 6.22 wt.%, Co content = 6.44 wt.%, Fe content = 5.99 wt.% (ICP-AES analysis). To a suspension of 1.2 g of the product obtained above in 500 mL of acetone, finely dispersed with an ultrasound probe for 30 minutes, are added 7 g of Vulcan XC-72R. The suspension is sonicated for 1 hour, then the solvent is eliminated under reduced pressure. The resulting solid mixture, containing the material P O LYM E R- Fe, Ni, Co/Vulcan, is introduced into a quartz reactor and heated under a flow of hydrogen at 365 °C for 2 hours. The solid residue obtained is finely ground and then added to a solution of palladium chloride (PdCI₂) prepared by dissolving 0.12 g of PdCI₂ in 500 ml_ of water acidified with 0.5 ml_ of concentrated HCI and gently heated to 40 °C. The suspension is vigorously stirred at room temperature and after 1 hour the solid residue is filtered off and washed with water (300 ml_). The collected solid is suspended in 500 ml_ of water and, under stirring at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) are added. The suspension is stirred at room temperature under a flow of nitrogen and after 2 hours the solid residue is filtered off, washed with water (500 ml_) and dried under vacuum up to constant weight. Ni content = 1.03 wt%, Co content =1.04 wt%, Fe content = 0.99 wt%, Pd content =1.06 wt% (ICP-AES analysis). Example 4 PREPARATION OF AN ANODE CATALYST BASED PALLADIUM

To a suspension of 3,1 1 g of Vulcan XC-72R in 100 mL of ethylene glycol, after sonication for 30 minutes, is added dropwise with vigorous stirring a solution of tetrachloropalladate acid (H₂PdCI₄), obtained by dissolving at high temperature 155 mg of palladium dichloride (PdCI₂) in 6 mL of concentrated HCI, 50 mL of H₂O and 50 mL of ethylene glycol.

The pH of the suspension is fixed to 3 by adding 45 mL of a water solution of

NaOH 2.5 M and the temperature is raised to 140 °C for 3 hours under an inert atmosphere.

The product is filtered off and washed with water (3 x 100 mL) and then dried under vacuum at 40 °C up to constant weight. Yield 3 g. Pd content = 4 wt% (ICP- AES, EDS analysis). Anode manufacturing

The catalysts, supported on conductive carbons, prepared with methods 1 - 3 are suspended in a water-ethanol mixture. To this suspension is added under vigorous stirring PTFE (polytetrafluoroethylene) and the floccolous product obtained is separated and then spread on appropriate conductive supports like carbon paper, stainless steel or nickel meshes. The electrode is then heated to 350 °C under a flow of an inert gas (Ar, N₂).

For a better comprehension of the invention, some examples of fuel cells are reported below: Cell example n. ° 1 1 ) HYPERMEC™ cathode Fe50-Co50, total metal loading: 60 micrograms/cm².

2) Tokuyama A006 membrane, rinsed with a KOH 1 M solution before use.

3) Ni-Zn-P-Pd/Vulcan XC-72R anode as described in example 1. Noble metal loading: 0.37 mg/cm², total metal loading: 1.6 mg/cm² 4) Dimensions of the Membrane Electrode Assembly (MEA): 5 cm².

5) Composition and volume (10 ml) of the fuel: ethanol 10 wt%; KOH 10 wt%.

Cell example n. ° 2

In this DAFC example, the points 1 , 2 , 3 e 4 described in the cell example n. ° 1 are unchanged, whereas the fuel is constituted by a water solution of ethylene glycol 10 wt% and KOH 10 wt%.

CeIIe example n. ° 3

1 ) HYPERMEC™ cathode Fe50-Co50, total metal loading: 60 micrograms/cm².

2) Tokuyama A006 membrane, rinsed with a KOH 1 M solution before use. 3) Pd/Vulcan XC-72R anode as described in example 4. Noble metal loading: 0.40 mg/cm²

4) Dimensions of the Membrane Electrode Assembly (MEA): 5 cm².

5) Composition and volume (10 ml) of the fuel: glycerol 10 wt%; KOH 10 wt%. Cell example n. ° 4 1 ) HYPERMEC™ cathode Fe50-Co50, total metal loading: 60 micrograms/cm².

2) Tokuyama A006 membrane, rinsed with a KOH 1 M solution before use.

3) Ni-Zn-P-Pt/Vulcan XC-72R anode as described in example 2. Noble metal loading: 0.77 mg/cm², total metal loading: 1.6 mg/cm² 4) Dimensions of the Membrane Electrode Assembly (MEA): 5 cm².

5) Composition and volume (10 ml) of the fuel: ethanol 10 wt%; KOH 10 wt%.

Claims

1. Process for the simultaneous production of electric energy and chemical compounds, having a functional group selected among aldehyde, ketone, keto- acid, carboxylic acid, hydroxy-acid and corresponding salts, comprising the partial oxidation of alcohols, polyalcohols or carbohydrates and characterized by the fact of being carried out in a in direct alcohol fuel cells (DAFC).

2. Process according to claim 1 wherein said alcohols, polyalcohols or carbohydrates are loaded into the cell in aqueous solution.

3. A process according to claim 2 where the carboxylic acids are obtained as salts of alkaline and alkaline earth metals.

4. A process according to claims 1 - 3 where said fuel cell contains as electrolyte an anion-exchange membrane.

5. A process according to claim 4 where said electrolyte is a solution o an alkaline or alkaline earth metal hydroxide.

6. A process according to claims 1 - 5 where said fuel cell contains an anode electrode made with transition metals of the Groups 8, 9, 10, 1 1 and 12 of the

Periodic Table of the Elements or their mixtures.

7. A process according to claim 6 where said anode electrocatalyst contains Ni,

Pd or Pt or their mixture.

8. A process according to claim 7 where said anode electrocatalyst contains also Sn, P, As, Sb or Bi.

9. A process according to claims 1 - 8 where said fuel cell of the DAFC type contains a cathode electrode of the state-of-the-art.

10. A process according to claims 1 - 9 where the reagent in the anode compartment is a primary alcohol and the products obtained are the corresponding carbonylic compound or carboxylates of an alkaline or alkaline earth metal in all the possible mutual percentage ratios.

11. A process according to claims 1 - 9 where the reagent in the anode compartment is a secondary alcohol and the product obtained is the corresponding ketone.

12. A process according to claims 1 - 9 where the reagent in the anode compartment is a polyalcohol and the products obtained are the corresponding carbonylic compounds or carboxylates, dicarboxylates keto/aldo-carboxylates and polyhydroxocarboxylayes of an alkaline or alkaline earth metal in all the possible mutual ratios.

13. A process according to claim 10 where the reagent is ethanol and the product obtained is the acetate of an alkaline or alkaline earth metal.

14. A process according to claim 12 where said reagent is ethylene glycol and the products obtained are the glycolate and/or oxalate of an alkaline or alkaline earth metal in all the possible percentage mutual ratios.

15. A process according to claim 12 where said reagent is glycerol and the products obtained are the glycerate, tartronate and/or oxalate of an alkaline or alkaline earth metal in all the possible mutual percentage ratios.

16. A process according to claim 12 where said reagent is 1 ,2-propandiol and the products obtained are the acetate and/or lactate of an alkaline or alkaline earth metal in all the possible mutual percentage ratios.

17. Direct alcohol fuel cells (DAFC) comprising an anion-exchange membrane, a cathode with an electrocatalyst of the state-of-the-art and an anode catalyst capable of performing the partial oxidation of alcohols, polyalcohols or carbohydrates to the corresponding aldehyde, ketone, keto-acid, carboxylic acid, hydroxy-acid and their corresponding salts.

18. DAFC according to claim 17 wherein said anode catalyst is made with transition metals of the Groups 8, 9, 10, 1 1 and 12 of the Periodic Table of the Elements or their mixtures.

19. DAFC according to claim 18 wherein said anode catalyst contains Ni, Pd or Pt or their mixture.

20. DAFC according to claim 19 wherein the anode catalyst contains a. Ni-Zn-P-A wherein A is Pd or Pt; b. Ni-Co-Fe-Pt; or c. Pd.