CATALYTIC METHOD FOR THE PRODUCTION OF HYDROCARBONS AND AROMATIC COMPOUNDS FROM OXYGENATED COMPOUNDS CONTAINED IN AQUEOUS MIXTURES

Abstract

The present invention relates to a method for producing mixtures of hydrocarbons and aromatic compounds, for use as fuel components (preferably in the range C5-C16), by means of catalytic conversion of the oxygenated organic compounds contained in aqueous fractions derived from biomass treatments, wherein said method can comprise at least the following steps: (i) bringing the aqueous mixture containing the oxygenated organic compounds derived from biomass in contact with a catalyst comprising at least Sn and Nb, Sn and Ti, and combinations of Sn, Ti and Nb; (ii) reacting the mixture with the catalyst in a catalytic reactor at temperatures between 100 and 350° C. and under pressures from 1 to 80 bar in the absence of hydrogen; and (iii) recovering the products obtained by means of the liquid/liquid separation of the aqueous and organic phases.

Claims

1. A method for producing mixtures of hydrocarbons and aromatic compounds, characterised in that it comprises, at least, the following steps: (a) bringing an aqueous mixture containing oxygenated organic compounds derived from primary treatments of biomass in contact with a catalyst, comprising at least one mixed metal oxide of Sn and Nb, Sn and Ti, and combinations of Sn, Ti and Nb and which, in the calcined form thereof, is made up of at least 65% by weight of the rutile crystalline phase of SnO.sub.2. (b) reacting the mixture with the catalyst in a catalytic reactor at temperatures between 50 and 450° C. and under pressures from 1 to 120 bar in the absence of hydrogen; (c) recovering the products obtained in step (b) by means of the liquid/liquid separation of the aqueous and organic phases.

2. The method according to claim 1, characterised in that the catalyst has the empirical formula:
Sn.sub.aNb.sub.bTi.sub.cM.sub.dO.sub.e wherein: M is a chemical element from the group of transition metals, rare earth elements or lanthanides, a is comprised between 0.05 and 10.0 b and c are comprised between 0 and 10.0, with c+b other than zero (c+b≠0) d is comprised between 0 and 4.0 and e has a value which depends on the oxidation state of the elements Sn, Nb, Ti and the element M.

3. The method according to claim 2, characterised in that d is zero and the catalyst has the empirical formula:
Sn.sub.aNb.sub.bTi.sub.cO.sub.e wherein: a is comprised between 0.05 and 10.0 b and c are comprised between 0.05 and 10.0, and e has a value which depends on the oxidation state of the elements Sn, Nb and Ti.

4. The method according to claim 2, characterised in that c is zero and the catalyst has the empirical formula:
Sn.sub.aNb.sub.bM.sub.dO.sub.e wherein: M is a chemical element from the group of transition metals, rare earth elements or lanthanides, a and b are comprised between 0.05 and 10, d is comprised between 0 and 4.0 and e has a value which depends on the oxidation state of the elements Sn, Nb and M.

5. The method according to claim 2, characterised in that b is zero and the catalyst has the empirical formula:
Sn.sub.aTi.sub.dM.sub.dO.sub.e wherein: M is a chemical element from the group of transition metals, rare earth elements or lanthanides, a and c are comprised between 0.05 and 10, d is comprised between 0 and 4.0 and e has a value which depends on the oxidation state of the elements Sn, Ti and M.

6. The method according to any of claims 1, 2, 4 and 5, characterised in that the element M is selected from the group of transition metals, rare earth elements, or lanthanides.

7. The method according to claim 6, characterised in that the element M is a transition metal, lanthanide or rare earth element selected from among V, Cr, Fe, Co, Ni, Cu, Zn, Mo, Ta, Ti, Re, La and combinations thereof.

8. The method according to any of the preceding claims, characterised in that the aqueous mixture derived from the biomass contains oxygenated organic compounds that have between 1 and 12 carbon atoms, and furthermore, they have between 1 and 9 oxygen atoms.

9. The method according to any of the preceding claims, characterised in that the total concentration of the oxygenated organic compounds present in the aqueous mixture derived from the biomass is in a range comprised between 0.5 and 99.5% by weight.

10. The method according to claim 9, characterised in that the total concentration of the oxygenated organic compounds present in the aqueous mixture derived from the biomass is in a range comprised between 1.0 and 70.0% by weight.

11. The method according to any of the preceding claims, characterised in that the contact between the aqueous mixture and the catalyst is performed in a reactor selected from among a batch reactor, a continuous stirred-tank reactor, a continuous fixed-bed reactor and a continuous fluidised-bed reactor.

12. The method according to claim 11, characterised in that the reactor is a batch reactor and the reaction is carried out in the liquid phase.

13. The method according to claim 12, characterised in that the process is carried out at a pressure between 1 to 80 bar.

14. The method according to any of claim 12 or 13, characterised in that the process is performed at a temperature comprised between 100° C. and 350° C.

15. The method according to any of claims 12 to 14, characterised in that the contact between the aqueous mixture containing the oxygenated organic compounds derived from the biomass and the catalyst is performed in a time ranging from 2 minutes to 200 hours.

16. The method according to any of claims 12 to 15, characterised in that the weight ratio between the aqueous mixture containing the oxygenated organic compounds derived from the biomass and the catalyst is between 1 and 200.

17. The method according to claim 11, characterised in that the reactor is a fixed-bed reactor or a fluidised-bed reactor.

18. The method according to claim 17, characterised in that the reaction temperature is comprised between 100° C. and 350° C.; the contact time is comprised between 0.001 and 200 s; and the working pressure between 1 and 100 bar.

19. The method according to any of the preceding claims, characterised in that the contact between the aqueous fraction containing the oxygenated organic compounds and the catalyst is performed under an atmosphere made of nitrogen, argon, an atmosphere made of air, nitrogen-enriched air, argon-enriched air, or combinations thereof.

20. The method according to claim 19, characterised in that it is carried out in an atmosphere made of nitrogen.

Description

BRIEF DESCRIPTION OF THE GRAPHS

[0198] FIG. 1 shows X-ray diffractograms of catalysts based on commercial oxides of Sn [SnO.sub.2], Nb [Nb.sub.2O.sub.5] and Ti [TiO.sub.2-Anatase] and [TiO.sub.2-Rutile].

[0199] FIG. 2 shows X-ray diffractograms of catalysts based on oxides of Sn (a) [SnO.sub.2], Nb (b) [Nb.sub.2O.sub.5] and Ti (c) [TiO.sub.2] prepared by co-precipitation described in examples 1, 2 and 3, respectively.

[0200] FIG. 3 shows X-ray diffractograms of catalysts based on oxides of tin and niobium [Sn—Nb—O] described in examples 4 to 7.

[0201] FIG. 4 shows X-ray diffractograms of catalysts based on oxides of tin and titanium [Sn—Ti—O] described in examples 8 to 11.

[0202] FIG. 5 shows X-ray diffractograms of catalysts based on oxides of tin, titanium and niobium [Sn—Nb—Ti—O] described in examples 12 to 15.

[0203] FIG. 6 shows the X-ray diffractogram of a catalyst based on Ce—Zr—O (Example 16).

[0204] FIG. 7 shows X-ray diffractograms of catalysts based on Nb and Ti supported by impregnation on tin oxide [Nb/SnO.sub.2 and Ti/SnO.sub.2] described in examples 17 and 18, respectively.

[0205] FIG. 8 shows a diagram with the chemical structures of reactants and main reaction products, together with the reactions that take place during the process.

[0206] FIG. 9 shows a comparison of the stability and maintenance of the catalytic activity with the reuses of the catalysts Sn—Nb—O (Example 5), Sn—Ti—O (Example 10) and Ce—Zr—O (Example 16).

EXAMPLES

[0207] Next, the inventors will illustrate the invention by means of different tests that demonstrate the preparation of the catalysts and the application thereof in the process of the invention.

Example 1. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin Oxide [SnO.SUB.2]

[0208] 14.72 g of tin (IV) chloride pentahydrate are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 2a.

Example 2. Preparation of a Catalyst by Co-Precipitation Method, Based on Niobium Oxide [Nb.SUB.2.O.SUB.5]

[0209] In 200.0 ml of water, 12.73 g of niobium oxalate are added, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 2b.

Example 3. Preparation of a Catalyst by Co-Precipitation Method, Based on Titanium Oxide [TiO.SUB.2]

[0210] 8.48 ml of an aqueous solution of titanium oxychloride with hydrochloric acid are added to 200.0 ml of water, which are kept under stirring until the complete homogenisation thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 2c.

Example 4. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Nb=0.77 [Sn—Nb—O (0.77)]

[0211] 9.82 g of tin (IV) chloride pentahydrate and 4.24 g of niobium oxalate are added to 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 3a.

Example 5. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Nb=0.58 [Sn—Nb—O (0.58)]

[0212] 7.01 g of tin (IV) chloride pentahydrate and 6.06 g of niobium oxalate are added to 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 3b.

Example 6. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Nb=0.43 [Sn—Nb—O (0.43)]

[0213] 4.91 g of tin (IV) chloride pentahydrate and 8.48 g of niobium oxalate are added to 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 3c.

Example 7. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Nb=0.29 [Sn—Nb—O (0.29)]

[0214] 3.51 g of tin (IV) chloride pentahydrate and 12.12 g of niobium oxalate are added to 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 3d.

Example 8. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Ti=0.74 [Sn—Ti—O (0.74)]

[0215] 14.02 g of tin (IV) chloride pentahydrate and 2.02 ml of an aqueous solution of titanium oxychloride with hydrochloric acid are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 4a.

Example 9. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Ti=0.64 [Sn—Ti—O (0.64)]

[0216] 9.82 g of tin (IV) chloride pentahydrate and 2.84 ml of an aqueous solution of titanium oxychloride with hydrochloric acid are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 4b.

Example 10. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Ti=0.33 [Sn—Ti—O (0.33)]

[0217] 4.91 g of tin (IV) chloride pentahydrate and 5.68 ml of an aqueous solution of titanium oxychloride with hydrochloric acid are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 4c.

Example 11. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin and Niobium Oxides with a Molar Ratio Sn/Ti=0.18 [Sn—Ti—O (0.18)]

[0218] 3.51 g of tin (IV) chloride pentahydrate and 8.08 ml of an aqueous solution of titanium oxychloride with hydrochloric acid are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 4d.

Example 12. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin, Niobium and Titanium Oxides with a Molar Ratio Sn/(Ti+Nb)=0.60 [Sn—Nb—Ti—O (0.60)]

[0219] 9.35 g of tin (IV) chloride pentahydrate and 1.33 ml of an aqueous solution of titanium oxychloride with hydrochloric acid and 5.05 g of niobium oxalate are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 5a.

Example 13. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin, Niobium and Titanium Oxides with a Molar Ratio Sn/(Ti+Nb)=0.35 [Sn—Nb—Ti—O (0.35)]

[0220] 5.84 g of tin (IV) chloride pentahydrate and 3.37 ml of an aqueous solution of titanium oxychloride with hydrochloric acid and 5.05 g of niobium oxalate are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 5b.

Example 14. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin, Niobium and Titanium Oxides with a Molar Ratio Sn/(Ti+Nb)=0.29 [Sn—Nb—Ti—O (0.29)]

[0221] 4.67 g of tin (IV) chloride pentahydrate and 2.70 ml of an aqueous solution of titanium oxychloride with hydrochloric acid and 8.08 g of niobium oxalate are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 5c.

Example 15. Preparation of a Catalyst by Co-Precipitation Method, Based on Tin, Niobium and Titanium Oxides with a Molar Ratio Sn/(Ti+Nb)=0.16 [Sn—Nb—Ti—O (0.16)]

[0222] 2.34 g of tin (IV) chloride pentahydrate and 5.40 ml of an aqueous solution of titanium oxychloride with hydrochloric acid and 5.05 g of niobium oxalate are added in 200.0 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=9. The resulting gel is transferred to a container where it is left to age for 24 h at room temperature. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 5d.

Example 16. Preparation of a Catalyst Based on Mixed Oxides of Ce and Zr [Ce—Zr—O] by the Co-Precipitation Method

[0223] This catalyst was synthesised in order to illustrate catalysts of mixed Ce—Zr oxides commonly used in literature for these types of condensation reactions [A. Gangadharan et al., Appl. Catal. A: Gral., 385 (2010) 80]. Several catalysts with different Ce—Zr ratios were synthesised, and the catalyst that provided the best results, in terms of yield of organics and conversion was selected to be compared with the catalysts of the present invention.

[0224] The catalyst was prepared by the method of synthesis by co-precipitation of the mixed Ce—Zr oxide adapting the method published by Serrano-Ruiz et al. [J. Catal., 241 (2006) 45-55]. In order to synthesise the catalyst Ce.sub.0.5Zr.sub.0.5O.sub.2, an aqueous solution of the salts of both metals in equimolar proportion is prepared. 11.76 g of Ce(NO.sub.3).sub.3.6H.sub.2O and 6.70 g of ZrO(NO.sub.3).sub.2.H.sub.2O are added in 150 ml of water, which are kept under stirring until the complete dissolution thereof. Next, a 28% NH.sub.4OH solution is added dropwise until reaching pH=10. Subsequently, the solution is transferred to a flask where it is left to age under stirring and at room temperature for 65 h. After a washing and filtering step, the solid is dried at 100° C. overnight. Lastly, the solid obtained is heated at 450° C. for 2 h in a stream of air in order to obtain the catalyst. The amounts of Ce and Zr measured by ICP coincide with the formula Ce.sub.0.5Zr.sub.0.5O.sub.2, and the X-ray diffractogram obtained for this sample indicates the presence of mixed oxides of Ce and Zr (FIG. 6)

Example 17. Preparation of a Catalyst Based on Mixed Oxides of Tin and Niobium [Nb—SnO.SUB.2 .Impreg.] Using an Impregnation Method

[0225] A mixed oxide catalyst was synthesised with an Sn—Nb ratio similar to the one used for the catalyst of example 4, in order to be able to be compared in terms of catalytic activity with the catalysts of the present invention.

[0226] The catalyst was prepared by the pore volume impregnation synthesis method. In order to synthesise the Nb—SnO.sub.2 catalyst, an aqueous solution is prepared containing 1.86 g of niobium oxalate in a volume of water previously calculated to impregnate about 1.5 g of commercial SnO.sub.2. The solution is added dropwise on said support until a homogeneous gel is obtained. After a drying step at a temperature of 100° C., the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 7a.

Example 18. Preparation of a Catalyst Based on Mixed Oxides of Sn and Ti [Ti—SnO.SUB.2 .Impreg.] Using an Impregnation Method

[0227] A mixed oxide catalyst was synthesised with an Sn—Ti ratio similar to the one used for the catalyst of example 8, in order to be able to be compared in terms of catalytic activity with the catalysts of the present invention.

[0228] The catalyst was prepared by the pore volume impregnation synthesis method. In order to synthesise the Ti—SnO.sub.2 catalyst, an aqueous solution is prepared containing 0.7 ml of an aqueous solution of titanium oxychloride with hydrochloric acid in a volume of water previously calculated to impregnate about 1.5 g of commercial SnO.sub.2. The solution is added dropwise on said support until a homogeneous gel is obtained. After a drying step at a temperature of 100° C., the solid obtained is heated at 600° C. for 2 h in a stream of air in order to obtain the catalyst. This catalyst presents a characteristic X-ray diffractogram like the one shown in FIG. 7b.

Example 19. Comparative Catalytic Activity of the Sn—Nb Series Catalysts of Examples 1, 2, 4, 5, 6 and 7

[0229] The catalytic activity experiments were carried out in the liquid phase using 12 ml stainless steel autoclave reactors with a reinforced interior coated with PEEK (polyether-ethyl-ketone) and equipped with a magnetic stirrer, pressure gauge and inlet/outlet valve for gases and liquid samples. The reactors are located on an individual steel jacket support with closed-loop temperature control.

[0230] The initial feed consists of a model aqueous mixture containing oxygenated compounds simulating the residual aqueous streams that are obtained after a phase separation process, after the pyrolysis of the biomass. The composition of the model aqueous mixture is detailed below (Table 1):

TABLE-US-00001 TABLE 1 Composition of the model aqueous mixture used as initial feed in the autoclave reactor. Component Content (% by weight) Water 30 Propionaldehyde 25 Hydroxyacetone 5 Acetic acid 30 Ethanol 10

[0231] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 1, 2, 4-7 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0232] The quantification of the products is carried out from the response factors calculated using the internal standard (solution of 2% by weight of chlorobenzene in methanol) and the organic compounds obtained with more than 5 carbon atoms are classified and quantified in ranges or intervals of compounds, the response factors of which have been calculated from representative molecules thereof. In addition to the main primary condensation reaction products, such as acetone, ethyl acetate, 3-pentanone and 2-methyl-2-pentenal, groups of molecules with 5, 6, 7, 8, 9, 10 or more than 10 carbon atoms are distinguished, produced by consecutive condensation reactions of reactants and primary products. To simplify the quantification of these reaction products, these molecules are grouped into two large groups of compounds, namely: C5-C8 Products and C9-C10+ Products. The chemical structures of the reactants and the main reaction products, together with the most significant reactions that take place during the process, are detailed in FIG. 8.

[0233] In the examples of catalytic activity illustrated, the following parameters are used to analyse the results obtained:

[0234] The conversion (in molar percentage) for each one of the oxygenated compounds present in the model aqueous mixture was calculated from the following formula:

Conversion (%)=(initial moles of oxygenated comp.−final moles of oxygenated comp./Initial moles of oxygenated comp.)*100

[0235] The final yield (in percentage by weight) of each of the products obtained was calculated from the following formula:

Product yield (%)=grams of product.sub.i in the reactor/total grams in the reactor

[0236] Yield of Total Organics (in percent by weight), was calculated from the following formula:

Total Organics (%)=(Yield.sub.Acetone+Yield.sub.3-pentanone+Yield.sub.2-methyl-2-pentenal+Yield.sub.C5-C8+Yield.sub.C9-C10+)

[0237] Furthermore, taking into account the composition of the model aqueous mixture used, the maximum of total organic products that could be obtained is calculated, supposing that: [0238] 100% conversion of all the reagents is reached. [0239] Acetic acid can be converted into ethyl acetate (esterification product) and acetone (ketonisation product). [0240] The final products are C9 type compounds (there are no intermediate or longer chain products in the final mixture).

[0241] With these assumptions, the composition of the final mixture would be:

[0242] 51.3% water, 19.1% ethyl acetate and 29.6% C9 products.

[0243] Therefore, the catalytic results (expressed as yield of total products) are calculated considering ≈30% as the maximum possible.

[0244] In this manner, the following results were obtained for the catalytic activity experiments with the catalysts based on Sn and Nb of Ex. 1, 2, 4, 5, 6 and 7:

TABLE-US-00002 TABLE 2 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and/or Nb of Examples 1, 2, 4, 5, 6 and 7. Example 1 4 5 6 7 2 Catalyst Sn—Nb—O Sn—Nb—O Sn—Nb—O Sn—Nb—O SnO.sub.2 (0.77) (0.58) (0.43) (0.29) Nb.sub.2O.sub.5 Conversion Acetic acid 12.2 14.9 4.9 6.7 13.2 11.5 (%) Propionaldehyde 81.2 90.9 96.1 92.7 85.9 67.2 Ethanol 45.7 54.2 55.6 54.5 50.3 34.4 Hydroxyacetone 100.0 100.0 100.0 100.0 100.0 100.0 Final Yield Acetone 1.0 1.2 1.0 1.6 2.2 0.7 (%) Ethyl acetate 23.1 20.4 17.3 17.3 24.6 24.2 3-pentanone 0.9 1.0 0.8 0.7 1.3 1.3 2-methyl-2-pentenal 32.9 33.2 32.6 31.9 33.5 29.0 C5-C8 14.5 13.4 12.7 11.4 10.9 11.2 C9-C10+ 8.5 17.1 18.6 18.2 16.6 9.5 Total Organics 57.8 65.9 65.7 63.8 64.5 51.7

[0245] From the comparison of the results in Table 2, it is observed that the conversion of hydroxyacetone is in all cases 100%, while the propionaldehyde conversion reaches a maximum (≈96%) for catalysts with an Sn/Nb molar ratio close to 0.6. Acetone (condensation product of the acetic acid) is present in the final mixture in amounts less than 1.5%, due to the fact that most of the acetic acid reacts with ethanol via esterification to give ethyl acetate. Furthermore, acetone is a highly reactive compound that can give rise to condensation products with a higher molecular weight.

[0246] Furthermore, it is observed how for molar ratios Sn/Nb≈0.4-0.6, the intermediate condensation products (C5-C8) gradually decrease in order to give rise to products with a higher molecular weight in subsequent condensation steps. Likewise, the increase in the conversion of the propionaldehyde causes the amount of 2-methyl-2-pentenal (the product of the first self-condensation of the propionaldehyde) to increase and successively convert into condensation products in the interval C9-C10+. Therefore, the Yield of Total Organics is maximised at those catalyst compositions.

[0247] These results show that the combination of Sn and Nb oxides in the structure of these catalysts produces higher yields of condensation products and, in general, higher yield of products in the range C9-C10+ than the identical SnO.sub.2 catalyst thereof without niobium (example 1). Moreover, the catalyst without tin Nb.sub.2O.sub.5 (example 2) shows even worse catalytic activity (both in conversion of oxygenated compounds and in yield of total organics, <52%). In contrast, even when there are small amounts of Sn present in the catalyst (See result with low concentrations of Sn, catalyst from Ex. 7), a mixed oxide with a rutile structure is formed which implies an improvement in the catalytic results. All this would indicate that there is an optimal range in the Sn/Nb ratio (between Examples 4, 5 and 6) in the structure of the catalyst in order to achieve maximum yields in the conversion of oxygenated compounds present in aqueous mixtures derived from the biomass.

Example 20. Comparative Catalytic Activity of the Sn—Ti Series Catalysts of Examples 1, 3, 8, 9, 10 and 11

[0248] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 1, 3, 8-11 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0249] In this manner, the following results were obtained for the catalytic activity experiments with the catalysts based on Sn and Ti of Ex. 1, 3, 8, 9, 10 and 11:

TABLE-US-00003 TABLE 3 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and/or Ti of Examples 1, 3, 8, 9, 10 and 11. Example 1 8 9 10 11 3 Catalyst Sn—Ti—O Sn—Ti—O Sn—Ti—O Sn—Ti—O SnO.sub.2 (0.74) (0.64) (0.33) (0.18) TiO.sub.2 Conversion Acetic acid 12.2 11.9 6.7 10.2 10.8 5.6 (%) Propionaldehyde 81.2 86.2 87.9 87.6 88.5 76.0 Ethanol 45.7 51.9 51.0 51.4 51.4 46.5 Hydroxyacetone 100.0 100.0 100.0 100.0 100.0 100.0 Final Yield Acetone 1.0 0.1 0.2 1.2 1.4 0.2 (%) Ethyl acetate 23.1 23.4 22.4 22.4 21.7 24.4 3-pentanone 0.9 1.1 1.1 1.1 1.1 0.7 2-methyl-2-pentenal 32.9 32.1 32.7 30.7 29.4 30.8 C5-C8 14.5 11.7 12.4 13.9 13.5 11.8 C9-C10+ 8.5 14.4 14.0 16.5 15.5 13.2 Total Organics 57.8 59.5 60.4 63.5 60.9 56.7

[0250] From the comparison of the results in Table 3, it is observed that the conversion of hydroxyacetone is in all cases 100%, while the propionaldehyde conversion reaches a maximum (≈88%) for all the catalysts based on mixed oxide wherein there is a rutile Sn—Ti phase, regardless of the Sn/Ti molar ratio. Acetone (condensation product of the acetic acid) is present in the final mixture in amounts less than 1.0%, due to the fact that most of the acetic acid reacts to give ethyl acetate. Furthermore, acetone is a highly reactive compound that can give rise to condensation products with a higher molecular weight.

[0251] It is seen that by having a mixed Sn—Ti phase, the conversion of propionaldehyde increases and causes the amount of 2-methyl-2-pentenal (product of the first self-condensation of the propionaldehyde) and above all, the products from second step condensation in the interval C9-C10+, to grow.

[0252] Therefore, the Yield of Total Organics has the same behaviour. This means that the yield of Total Organics, and particularly the production of C9-C10 compounds, can be increased by synthesising the materials in suitable Sn—Ti—O compositions.

[0253] These results show that the combination of Sn and Ti oxides in the structure of these catalysts produce higher yields of condensation products and, in general, higher yield of products in the range C9-C10+ than the identical SnO.sub.2 catalyst thereof without titanium (Example 1). Furthermore, the catalyst without tin, TiO.sub.2 (Example 3) shows an acceptable catalytic activity (yield of total organics, ≈57%), although the result is not entirely comparable, since when synthesising this oxide by co-precipitation, the resulting phase is TiO.sub.2-anatase. All this would indicate that the synthesis of mixed oxides based on Sn/Ti with a rutile structure (Examples 8 to 11) in the catalyst structure represents an improvement in the conversion of oxygenated compounds present in aqueous mixtures derived from the biomass.

Example 21. Comparative Catalytic Activity of the Sn—Ti—Nb Series Catalysts of Examples 1, 2, 12, 13, 14 and 15

[0254] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 1, 2, 12-15 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0255] In this manner, the following results were obtained for the catalytic activity experiments with the catalysts based on Sn—Ti—Nb of Ex. 1, 2, 12, 13, 14 and 15:

TABLE-US-00004 TABLE 4 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and/or Ti and/or Nb of Examples 1, 2, 12, 13, 14 and 15. Example 1 12 13 14 15 2 Catalyst Sn—Ti—Nb—O Sn—Ti—Nb—O Sn—Ti—Nb—O Sn—Ti—Nb—O SnO.sub.2 (0.60) (0.35) (0.29) (0.16) Nb.sub.2O.sub.5 Conversion Acetic acid 12.2 16.0 14.4 8.0 12.1 11.5 (%) Propionaldehyde 81.2 93.2 93.8 93.0 94.2 67.2 Ethanol 45.7 48.7 49.8 44.2 41.6 34.4 Hydroxyacetone 100.0 100.0 100.0 100 100.0 100.0 Final Yield Acetone 1.0 1.3 1.0 1.5 0.8 0.7 (%) Ethyl acetate 23.1 22.6 21.4 24.3 24.8 24.2 3-pentanone 0.9 1.0 0.9 0.7 0.7 1.3 2-methyl-2-pentenal 32.9 32.6 29.5 32.1 31.3 29.0 C5-C8 14.5 13.3 16.8 13.7 13.1 11.2 C9-C10+ 8.5 17.4 17.6 16.3 18.4 9.5 Total Organics 57.8 65.6 65.7 64.3 64.3 51.7

[0256] From the comparison of the results in Table 4, it is observed that the conversion of hydroxyacetone is in all cases 100%, while the propionaldehyde conversion increases dramatically when a mixed oxide of Sn with Ti and Nb is formed in the catalysts used.

[0257] Acetone (condensation product of the acetic acid) is present in the final mixture in amounts less than 1.5%, due to the fact that most of the acetic acid reacts by esterification to produce ethyl acetate. Furthermore, acetone is a highly reactive compound that can give rise to condensation products with a higher molecular weight.

[0258] The increase in the conversion of the propionaldehyde causes the amount of 2-methyl-2-pentenal (product of the first self-condensation of the propionaldehyde) to increase and therefore, be able to continue reacting in order to give rise to condensation products in the interval C9-C10+(the result of subsequent condensation steps). Both the C9-C10+ products and the Yield of Total Organics have the same behaviour.

[0259] These results show that the combination of oxides of Sn, Ti and Nb in the structure of these catalysts produce higher yields of condensation products and, in general, higher yield of products in the range C9-C10+ than the simple oxide catalyst thereof: SnO.sub.2 (Example 1), Nb.sub.2O.sub.5 (Example 2) or TiO.sub.2 (Example 3). All this would confirm that the formation of a mixed oxide phase with rutile phase with a Sn/(Ti+Nb) ratio (between Examples 12 and 15) in the catalyst structure enables the maximum yields to be achieved in the conversion of oxygenated compounds present in aqueous mixtures derived from the biomass.

Example 22. Comparative Catalytic Activity of the Sn—Nb Series Catalysts (Examples 4 and 5) Compared to Nb—SnO.SUB.2 .Oxide Prepared by Impregnation (Example 17) and Commercial Nb.SUB.2.O.SUB.5 .(Sigma-Aldrich, CAS 1313-96-8)

[0260] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 4, 5, 17 and of commercial Nb.sub.2O.sub.5 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0261] The following results were obtained:

TABLE-US-00005 TABLE 5 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and Nb, Examples 4 and 5, compared to the results of the Nb—SnO.sub.2 catalyst prepared by impregnation (Example 17) or of the commercial Nb.sub.2O.sub.5. Example 4 5 17 Catalyst Sn—Nb—O Sn—Nb—O Commercial (0.77) (0.58) Nb—SnO.sub.2 Nb.sub.2O.sub.5 Conversion Acetic acid 14.9 4.9 16.7 15.4 (%) Propionaldehyde 90.9 96.1 67.6 70.6 Ethanol 54.2 55.6 45.9 50.7 Hydroxyacetone 100.0 100.0 100.0 100.0 Final Yield Acetone 1.2 1.0 1.5 0.2 (%) Ethyl acetate 20.4 17.3 27.2 22.3 3-pentanone 1.0 0.8 0.9 0.6 2-methyl-2-pentenal 33.2 32.6 29.2 26.7 C5-C8 13.4 12.7 12.8 5.3 C9-C10+ 17.1 18.6 11.9 16.3 Total Organics 65.9 65.7 56.3 49.0

[0262] In Table 5, the catalytic results of catalysts based on structures containing Sn—Nb—O prepared by co-precipitation and described above (Examples 4 and 5) are compared with another catalyst based on mixed oxides of both metals and prepared by the impregnation method, the preparation of which is described in Example 17. Furthermore, a commercial Nb.sub.2O.sub.5 catalyst is also used acquired from Sigma-Aldrich, which is similarly activated prior to use.

[0263] From the results of Table 5, the total conversion of hydroxyacetone is observed in all cases, while the conversion of acetic acid is quite similar in all the cases studied (close to 15%).

[0264] The propionaldehyde conversion is the biggest difference between one type of catalyst and the others. While catalysts based on combined Sn—Nb structures have conversions >90%, the commercial niobium catalyst and the Nb—SnO.sub.2 catalyst (Example 17), have much lower conversions (67-70%). This causes the decrease in the formation of first condensation products such as 2-methyl-2-pentenal and some C5-C8 products, as well as products with a higher molecular weight created by means of second condensation reactions. In these cases, the Yield of Total Organics decreases to 49-56%, which means that the use of catalysts based on specific Sn—Nb structures such as that of Examples 4 and 5 increases by 15-25% the products obtained in the final reaction mixture of the condensation of oxygenated compounds present in aqueous mixtures derived from biomass. These products are potentially usable as additives in fractions of gasoline and of refining in general.

[0265] These results show that the catalysts of the method of the present invention show results in activity and yields to products superior to those obtained with catalysts prepared by means of conventional methods or with similar commercial materials.

Example 23. Comparative Catalytic Activity of the Catalysts of the Sn—Ti Series (Examples 10 and 11) Compared to Ti—SnO.SUB.2 .Oxide Prepared by Impregnation (Example 18) and Samples of Commercial Anatase TiO.SUB.2 .(Sigma-Aldrich, CAS 1317-70-0) and Commercial Rutile TiO.SUB.2 .(Sigma-Aldrich, CAS 1317-80-2)

[0266] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 10, 11, 18 and samples of commercial TiO.sub.2 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0267] The following results were obtained:

TABLE-US-00006 TABLE 6 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and Ti, Examples 10 and 11, compared to the results of the Ti—SnO.sub.2 catalyst prepared by impregnation (Example 18) or from samples of commercial TiO.sub.2. Example 10 11 18 Catalyst Commercial Commercial Sn—Ti—O Sn—Ti—O TiO.sub.2 TiO.sub.2 (0.33) (0.18) Ti—SnO.sub.2 (Anatase) (Rutile) Conversion Acetic acid 10.2 10.8 18.7 16.4 9.8 (%) Propionaldehyde 87.6 88.5 67.9 66.4 58.4 Ethanol 51.4 51.4 47.7 46.0 39.0 Hydroxyacetone 100.0 100.0 100.0 100.0 100.0 Final Yield Acetone 1.2 1.4 2.0 1.0 0.4 (%) Ethyl acetate 22.4 21.7 20.7 28.1 23.4 3-pentanone 1.1 1.1 1.0 0.7 0.6 2-methyl-2-pentenal 30.7 29.4 18.4 28.9 25.0 C5-C8 13.9 13.5 19.8 6.7 14.0 C9-C10+ 16.5 15.5 10.0 13.7 8.2 Total Organics 63.5 60.9 51.4 51.0 48.2

[0268] In Table 6, the catalytic results of catalysts based on structures containing Sn—Ti—O prepared by co-precipitation and described above (Examples 10 and 11) are compared with another catalyst based on mixed oxides of both metals and prepared by the impregnation method, the preparation of which is described in Example 18. Furthermore, samples of commercial TiO.sub.2 acquired from Sigma-Aldrich are also used, which is similarly activated prior to use.

[0269] From the results of Table 6, the total conversion of hydroxyacetone is observed in all cases, while the conversion of acetic acid is quite similar in all the cases studied (close to 10-15%).

[0270] The propionaldehyde conversion is the biggest difference between one type of catalyst and the others. While catalysts based on combined Sn—Ti structures have conversions >87%, the samples of commercial titanium oxide and the Ti—SnO.sub.2 catalyst (Example 18), have much lower conversions (58-68%). This causes the decrease in the formation of first condensation products such as 2-methyl-2-pentenal and some C5-C8 products, as well as products with a higher molecular weight created by means of second condensation reactions. In these cases, the Yield of Total Organics decreases to 48-51%, which means that the use of catalysts based on specific Sn—Ti structures such as that of Examples 10 and 11 increases by ≈20% the products obtained in the final reaction mixture of the condensation of oxygenated compounds present in aqueous mixtures derived from biomass. These products are potentially usable as additives in fractions of gasoline and of refining in general.

[0271] These results show that the catalysts of the method of the present invention show results in activity and yields to products superior to those obtained with catalysts prepared by means of conventional methods or with similar commercial materials.

Example 24. Comparative Catalytic Activity of the Catalysts of the Sn—Nb—O, Sn—Ti—O and Sn—Ti—Nb—O Series Prepared by Co-Precipitation Method (Examples 4, 5, 10, 11, 12 and 13)

[0272] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 4, 5, 10, 11, 12 and 13 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0273] The following results were obtained:

TABLE-US-00007 TABLE 7 Catalytic activity in the conversion of oxygenated compounds present in a model aqueous mixture of catalysts based on Sn and/or Nb and/or Ti, prepared by co-precipitation, Examples 4, 5, 10, 11, 12 and 13. Example 4 5 10 11 12 13 Catalyst Sn—Nb—O Sn—Nb—O Sn—Ti—O Sn—Ti—O Sn—Ti—Nb—O Sn—Ti—Nb—O (0.77) (0.58) (0.33) (0.18) (0.60) (0.35) Conversion Acetic acid 14.9 4.9 10.2 10.8 16.0 14.4 (%) Propionaldehyde 90.9 96.1 87.6 88.5 93.2 93.8 Ethanol 54.2 55.6 51.4 51.4 48.7 49.8 Hydroxyacetone 100.0 100.0 100.0 100.0 100.0 100.0 Final Yield Acetone 1.2 1.0 1.2 1.4 1.3 1.0 (%) Ethyl acetate 20.4 17.3 22.4 21.7 22.6 21.4 3-pentanone 1.0 0.8 1.1 1.1 1.0 0.9 2-methyl-2-pentenal 33.2 32.6 30.7 29.4 32.6 29.5 C5-C8 13.4 12.7 13.9 13.5 13.3 16.8 C9-C10+ 17.1 18.6 16.5 15.5 17.4 17.6 Total Organics 65.9 65.7 63.5 60.9 65.6 65.7

[0274] In Table 7, the catalytic results of catalysts based on structures containing Sn—Nb—O, Sn—Ti—O and Sn—Nb—Ti—O prepared by co-precipitation and then heat treated in an atmosphere made of air at 600° C. as described above (Examples 4, 5, 10, 11, 12 and 13) are compared.

[0275] From the results of Table 7, the total conversion of hydroxyacetone is observed in all cases is 100%, while the acetic acid conversion is quite similar in the catalysts shown here (Examples 4, 10, 11, 12, 13); being somewhat less in the material of example 5.

[0276] The yield of 2-methyl-2-pentenal, C9-C10 products and in general yield of Total Organic products can be increased by synthesising the materials in suitable compositions, thus achieving catalysts based on specific structures of Sn—Nb—O, Sn—Ti—O and Sn—Ti—Nb—O such as in Examples 4, 5, 10, 11, 12 and 13.

Example 25. Comparative Catalytic Activity of the Catalysts of the Sn—Nb—O, Sn—Ti—O and Sn—Ti—Nb—O Series, Prepared by Co-Precipitation (Examples 5, 10 and 13) Compared to a Conventional Ce—Zr Catalyst (Example 16)

[0277] 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 5, 10, 13 and 16 were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0278] The following results were obtained:

TABLE-US-00008 TABLE 8 Comparative catalytic activity of catalysts based on Sn, Nb and/or Ti of Examples 5, 10 and 13 in the conversion of oxygenated compounds present in a model aqueous mixture compared to a conventional Ce—Zr catalyst (Example 16). Example 5 10 13 16 Catalyst Sn—Nb—O Sn—Ti—O Sn—Ti—Nb—O Ce—Zr—O (0.58) (0.33) (0.35) (0.55) Conversion Acetic acid 4.9 10.2 14.4 17.4 (%) Propionaldehyde 96.1 87.6 93.8 93.8 Ethanol 55.6 51.4 49.8 47.8 Hydroxyacetone 100.0 100.0 100.0 100.0 Final Yield Acetone 1.0 1.2 1.0 0.7 (%) Ethyl acetate 17.3 22.4 21.4 19.4 3-pentanone 0.8 1.1 0.9 0.5 2-methyl-2-pentenal 32.6 30.7 29.5 36.8 C5-C8 12.7 13.9 16.8 5.4 C9-C10+ 18.6 16.5 17.6 25.2 Total Organics 65.7 63.5 65.7 68.5

[0279] The conversions of propionaldehyde and hydroxyacetone are very similar in the catalysts of Examples 5, 10, 13 and 16, while the Ce—Zr—O catalyst has a higher conversion of acetic acid (results in Table 7). However, both the overall conversion of reagents and the Yield of Total Organics observed are very similar in the three examples studied (64-68%). The only observable difference between catalysts based on oxides of Sn, Nb and/or Ti (Ex. 5, 10 and 13) and the mixed oxide of Ce—Zr (Ex. 16) lies in that the first three have higher production of organic compounds in the interval C5-C8, while the mixed oxide prepared in Example 16 is able to more easily catalyse second condensation reactions, increasing the amount of compounds in the interval C9-C10+.

[0280] In general, catalysts based on structures combining Sn, Nb and/or Ti have results similar to those demonstrated by a catalyst such as Ce.sub.0.5Zr.sub.0.5O.sub.2 traditionally used in the literature for reactions of this type.

[0281] Once the catalysts of Examples 5, 10, 13 and 16 are used, they are recovered after the reaction, washed with methanol and dried at 100° C. overnight. Subsequently, they are characterised by means of Elemental Analysis (EA) and Thermogravimetry (TG).

[0282] The EA study shows that the Ce—Zr catalyst of Example 16 has 3.5% by weight of charcoal (organic products deposited on the catalyst) after washing. The catalyst based on Sn—Nb of Example 5 has only 0.5% by weight of charcoal, demonstrating that there is less deposition of carbonaceous substances during the reactive process, and hence it is less sensitive to deactivation caused by coke deposition.

[0283] This characterisation data is confirmed by means of TG analyses. The Ce—Zr catalyst of Example 16 has a loss of mass of 11.5% at a temperature close to 300° C. corresponding to the desorption of the absorbed organic products. In contrast, the catalyst of Example 5 only has a loss of mass of 1.5% at said temperature. This catalyst also shows a loss of mass of 1.8% at a temperature close to 100° C. corresponding to the absorbed water. This amount of absorbed water is also observed in the TG analysis of the catalyst before being used, for which reason the presence of water in the reaction medium is not detrimental to the activity of the catalyst or the stability thereof.

Example 26. Comparative Catalytic Activity During the Reuse of the Sn—Nb—O (Ex. 5), Sn—Ti—O (Ex. 10), and Ce—Zr—O (Ex. 16) Catalysts

[0284] A series of consecutive reactions were carried out with the catalysts prepared in Examples 5, 10 and 16 in order to compare the activity thereof after several uses. To this end, the initial reaction (R0) and three subsequent reuses (R1, R2 and R3) were performed, all under the same reaction conditions. The catalysts used are recovered after each reaction, washed with methanol and dried at 100° C. overnight. Subsequently, they are characterised by means of Elemental Analysis (EA) and Thermogravimetry (TG).

[0285] In each case (R0, R1, R2 and R3), 3000 mg of the model aqueous mixture and 150 mg of one of the catalytic materials from Examples 5, 10, and 16 (fresh or already used) were introduced into the autoclave reactor described above. The reactor was hermetically sealed, was initially pressurised with 13 bar of N2, and was heated to 200° C. under continuous stirring. Liquid samples (≈50-100 μl) were taken at different time intervals up to 7 hours of reaction. The samples were filtered and diluted in a standard solution of 2% by weight of chlorobenzene in methanol, and analysed by gas chromatography in a GC-Bruker 430 equipped with an FID detector and a 60 m TRB-624 capillary column. The product identification is carried out using an Agilent 6890 N Gas Chromatography system coupled with an Agilent 5973 N (GC-MS) Mass Detector and equipped with a 30 m long HP-5 MS capillary column.

[0286] The obtained results are shown in Tables 9, 10 and 11, and in FIG. 9.

TABLE-US-00009 TABLE 9 Catalytic activity during the reuse of the Sn—Nb—O catalyst (0.58) of Example 5. RO R1 R2 R3 Conversion Acetic acid 4.9 6.3 8.7 13.7 (%) Propionaldehyde 96.1 94.4 90.2 86.2 Ethanol 55.6 52.3 50.4 44.1 Hydroxyacetone 100.0 100.0 100.0 100.0 Final Yield Acetone 1.0 2.0 1.8 1.7 (%) Ethyl Acetate 17.3 17.1 20.2 24.1 3-pentanone 0.8 0.8 0.9 0.9 2-methyl-2-pentenal 32.6 32.7 33.3 34.4 C5-C8 12.7 12.4 12.5 12.5 C9-C10+ 18.6 17.5 16.7 15.8 Total Organics 65.7 65.4 65.2 65.2

TABLE-US-00010 TABLE 10 Catalytic activity during the reuse of the Sn—Ti—O catalyst (0.33) of Example 10. RO R1 R2 R3 Conversion Acetic acid 10.2 8.9 7.9 8.6 (%) Propionaldehyde 87.6 85.3 81.5 78.2 Ethanol 51.4 51.8 53.5 46.2 Hydroxyacetone 100.0 100.0 100.0 100.0 Final Yield Acetone 1.2 1.3 1.7 1.5 (%) Ethyl Acetate 22.4 22.0 21.6 21.8 3-pentanone 1.1 0.8 0.3 1.4 2-methyl-2-pentenal 30.7 29.5 28.2 26.4 C5-C8 13.9 14.2 14.6 12.4 C9-C10+ 16.5 16.1 15.7 15.8 Total Organics 63.5 61.9 60.5 57.5

TABLE-US-00011 TABLE 11 Catalytic activity during the reuse of the Ce—Zr—O catalyst of Example 16. RO R1 R2 R3 Conversion Acetic acid 17.4 13.4 3.8 0.0 (%) Propionaldehyde 93.8 87.8 84.8 81.2 Ethanol 47.8 49.7 50.1 55.3 Hydroxyacetone 100.0 100.0 100.0 100.0 Final Yield Acetone 0.7 0.7 0.3 0.4 (%) Ethyl Acetate 19.4 20.2 20.0 20.9 3-pentanone 0.5 0.5 0.4 0.5 2-methyl-2-pentenal 36.8 34.1 31.7 27.9 C5-C8 5.4 6.3 7.0 7.1 C9-C10+ 25.2 25.0 25.2 21.7 Total Organics 68.5 66.6 64.6 57.6

[0287] In general, the same behaviour is observed for all the catalysts in the conversion of the reagents present in the initial aqueous mixture. The propionaldehyde conversion decreases with the number of reactions performed. In contrast, the acetic acid conversion decreases for the case of Ce—Zr—O, while it remains constant or even increases for materials based on Sn—Nb and Sn—Ti. Moreover, the ethanol conversion increases in the case of the catalyst based on Ce—Zr—O (Ex. 16) and decreases slightly in the rest of the catalysts containing Sn and/or Nb and/or Ti (Ex. 5 and 10). Consequently, the Yield of Total Organics slightly decreases with the number of reuses in said catalysts, but the drop is more pronounced in the case of the Ce—Zr—O catalyst of Example 16 with a percentage loss of catalytic activity with respect to the initial one of 16%, while the Sn—Nb—O catalyst prepared in Example 5 has excellent stability with a percentage drop in catalytic activity of only 1% (see FIG. 8). This means that the activity of the Sn—Nb—O catalyst prepared in Example 5 remains practically constant after at least 3 consecutive reuses. Moreover, the catalyst based on Sn—Ti—O of Example 10 shows an intermediate drop in catalytic activity (10%) between the Ce—Zr—O material (Ex. 16) and the Sn—Nb—O catalyst (Ex. 5).

[0288] It should be noted that in the case of the Ce—Zr—O catalyst of Example 16, at the end of the reuses only 80 mg of the 150 mg initially added are recovered, while 130 mg are recovered in the case of the Sn—Nb—O catalyst of Example 5. The lower amount of solid catalyst recovered may be due to a lower stability of the Ce—Zr—O catalyst and the possible formation of cerium acetate, which causes the extraction of the cerium oxide from the catalyst structure. This also explains the drastic drop in acetic acid conversion with reuses (Table 11).

[0289] At the same time, the analyses performed by means of EA and TG confirm the higher stability of the catalyst based on Sn—Nb of Example 5 and the one based on Sn—Ti of Example 10 compared to the mixed oxide of Ce—Zr prepared in Example 16. Thus, in the Sn—Nb material (Ex. 5) only 0.5% by weight of charcoal is determined by EA after the third reuse (R3); 2.8% in the case of Sn—Ti (Ex. 10), while the amount of charcoal detected in the Ce—Zr catalyst (Ex. 16) after the same number of reuses reached 4.8% by weight. Likewise, it is observed by TG analysis that the Sn—Nb catalyst (Ex. 5) suffers a loss of mass of 1.5% at temperatures close to 300-350° C. corresponding to the absorbed organic products, while the mixed oxide of Ce—Zr (Ex. 16) has a loss of mass of 9.5% at these temperatures, plus an additional 3.3% at temperatures close to 450° C., the latter corresponding to heavier reaction products absorbed in the catalyst.