WO2008017342A1 - Catalytic oxidation of terpenes using noble metal catalysts - Google Patents

Abstract

The invention relates to the catalytic oxidation of oxygen-containing terpenes in the liquid phase, using noble metal catalysts and oxygen, mixtures of oxygen and inert gases or air as oxidants. Terpenes in different oxidation states may be used as reactants, examples being terpene alcohols or terpene aldehydes. The use of supported noble metal catalysts is essential for the attainment of high product selectivities. High carboxylic acid product selectivities are achieved in the pH range from 8 to 12, with reaction temperatures of 5 to 120°C and pressures of 1 to 10 bar, with quantitative conversions.

Description

 description

Catalytic oxidation of terpenes with noble metal catalysts

The invention relates to the heterogeneous-catalytic oxidation of oxygen-containing terpenes in the liquid phase using noble metal-containing catalysts and oxygen, mixtures of oxygen and inert gases or air as an oxidant in the corresponding carboxylic acids. In this case, terpenes of different oxidation states can serve as reactants, for example terpene alcohols or terpene aldehydes. The use of supported noble metal catalysts is essential for achieving high product selectivities.

The catalysts used in the process according to the invention consist of noble metals and oxidic support materials. The catalyst contains gold alone or gold in combination with one or more metal compounds from the group consisting of Rh, Ir, Pd, Pt and Ag. The precious metals or precious metal combinations are present in the oxidation state 0. The oxidic support materials include Al ₂ O ₃ , TiO ₂ , SiO ₂ , aluminosilicates, ZrO ₂ , CeO ₂ , Y ₂ O ₃ , Nb ₂ O ₃ , zeolites and mesoporous materials such as MCM-41 (Mobil OiI Corp.), SBA- 15 (SBA Materials, Inc.).

The catalytic oxidation of aliphatic and aromatic alcohols and aldehydes with oxygen to their carboxylic acids has been described using various metal catalysts. Often other functional groups, such as double bonds, proved to be disturbing. The product selectivity was often insufficient for such substrates or the catalysts did not show sufficient stability under industrial conditions for industrial use. Thus, the vapor or gas phase oxidation of unsaturated aldehydes with oxygen with Mo or V-containing catalysts (JP 2005296810, JP 2002282696) or P, Mo, V, Cu, Ag and Sb-containing catalysts (JP 61076436) or a five-metal oxide catalyst (JP 52019619). This reaction is for the temperature-sensitive terpenes, also because of the byproduct problem, less suitable.

Saturated linear and cyclic alcohols were treated with various oxidants, including oxygen, in the presence of Au.

Carrier catalysts in the liquid phase in the corresponding aldehydes and carboxylic acids transferred (WO 2002/016 298). Also for activated alcohols, such as diols, (H. Berndt, I. Pitsch, S. Evert, K. Struve, M.-M. Pohl, J. Radnik, A. Martin, Appl. Catal. A: Gen. 244 ( 2003) 169;) or triols, eg Glycerol, gold has been described as a suitable selective catalyst for the aerobic oxidation to carboxylic acids.

Polymer-stabilized colloidal gold nanoclusters served as catalysts for long-chain diols, they must be separated after the reaction on polymer membranes (PGN Mertens, I. FJ Vankelecom, PA Jacobs, DE De Vos, Gold Bulletin 38 (2005) 157-162) and are not particularly leaching-stable. Aldehydes can react in a radical process with oxygen to form peracids in addition to a catalytic oxidation without catalyst in a radical process, they can oxidize another molecule of aldehyde to acid and even react to a molecule of acid, the best solvents are halogenated hydrocarbons. The cleavage of the peracid can be problematic, it could be achieved in JP 2001011009 by pyrolysis under inert gas in aliphatic hydrocarbons as a solvent.

erforderlich, der schwer abtrennbar ist (K. Sato, M. Hyodo, J. Takagi, M. Aoki, R. Noyori, Tetrahedron Lett. 41 (2000) 1439). Die klassische alkalische lodoxidation in Gegenwart von Alkalihydroxid aus der Zuckerchemie wurde auf aromatische und steroidale Aldehyde übertragen (S. Yamada, D. Morizono, K. Yamamoto, Tetrahedron Lett. 33 (1992) 4329).Saturated aliphatic and aromatic aldehydes or their acetals having 4 to 22 carbon atoms were oxidized with oxygen in a carboxylic acid or a carboxylic acid / water mixture (CiC ₃ acids, to 25% water) as solvent to the corresponding acids (DE 4 435 332). , Aldehydes could also be reacted with oxygen or air in the presence of an amine or amine N-oxide promoter to carboxylic acids (EP 0 855 996). Alpha-branched carboxylic acids were obtained from the aldehydes with O ₂ in the presence of an alkaline earth metal formate (JP 53105412, JP 53105411). For the oxidation of aldehydes to carboxylic acids and other oxidizing agents can be used, but these are usually not desirable for environmental reasons. Although the oxidation of aldehydes to carboxylic acids with 30% hydrogen peroxide is also considered to be environmentally friendly, however, is for the reaction is a complicated to produce and not commercially available phase transfer catalyst

which is difficult to separate (K. Sato, M. Hyodo, J. Takagi, M. Aoki, R. Noyori, Tetrahedron Lett. 41 (2000) 1439). The classical alkaline iodine oxidation in the presence of alkali metal hydroxide from sugar chemistry has been transferred to aromatic and steroidal aldehydes (S. Yamada, D. Morizono, K. Yamamoto, Tetrahedron Lett. 33 (1992) 4329).

With oxone ^® / acetone a non-catalytic method of synthesizing carboxylic acid was prepared from aldehydes (KS Webb, SJ. Ruszkay, Tetrahedron 54 (1998) 401).

The reaction of saturated aliphatic aldehydes having 4-11 carbon atoms in the presence of salts, acetylacetonates or carbonyls of V, Cr, Mo, Fe, Co, Ni, Ru, Rh, Pd, Cu, preferably of iron and rhodium, with oxygen (1) 10 bar, preferably 8 bar) led to the corresponding carboxylic acids (WO 0166504), such as butyric acid, methyl butyric acid, heptanoic acid, isononanoic acid. Butyric acid and isobutyric acid could be prepared from butyraldehydes with oxygen (CS 223255), also in the presence of an alkali metal salt (JP 55013225). The production of low molecular weight saturated acids is less problematic because no side reactions are to be expected due to the lack of double bonds.

The oxidation of aldehydes with gold / activated carbon catalysts has been described in the group of Prati (S. Biella, L. Prati, M. Rossi, J. Mol. Catal. A: Chem. 197 (2003) 207). The reaction is also feasible at pH 7, but is only applied to saturated aliphatic and aromatic aldehydes. In

Water only water-soluble low molecular weight aliphatic aldehydes react well, otherwise good conversions can only be achieved in CCU. The oxygen pressure used was 3 bar, the aldehyde / Au ratio 1000: 1. Water-dispersible terpene aldehydes with further functional groups, such as double bonds, have not been investigated.

Also, for hemiacetals of mono- and oligosaccharides, gold on oxidic supports is a suitable catalyst system for the aerobic oxidation

Aldonic acids (WO 2004/099 114 A8, H. Berndt, A. Martin, I. Pitsch, U. Pruess, K.D. Vorlop, Catal. Today 91-92 (2004) 191). The reaction requires an alkaline medium (pH 8-12). However, in the highly alkaline environment, side reactions may occur in the oxidation of CH-acidic aldehydes (e.g., aldol reaction, Cannizzaro reaction).

Unsaturated aliphatic aldehydes can also be oxidized with copper, silver and gold supported catalysts continuously in the gas phase at 300 to 600 ⁰ C with oxygen to the unsaturated carboxylic acids (DE 000019 722 567). However, these reaction conditions are not suitable for terpene compounds.

Catalytic oxidations of terpene alcohols or terpene aldehydes to terpenecarboxylic acids have been described extremely rarely. Thus, for example, the production of citronellic acid from citronellol or citronellal in the presence of a Cu-Zn or Cu-Cr catalyst, sodium hydroxide and a liquid paraffin as a solvent at 200 to 25O ⁰ C from JP 54061115 known. Stoichiometric processes for the oxidation of terpenes (see JL Simonsen, "The Terpenes", Cambridge University Press 1947) have the drawback of saline loading and the use of organic solvents does not lead to sustainable processes.

Other preparations of terpene carboxylic acids, such as citronellic acid, are by microbial methods (S. Oda, T. Sugai, H. Ohta, Bull. Chem. Soc., Japan, 73 (2000) 2819). However, the space-time yields are not sufficient for an industrial process.

In summary, it can be stated that there is no catalytic process for the selective oxidation of alcohols and aldehydes with terpene structure in the accessible literature, which has a very high technical grade Applications of appropriate selectivity and using environmentally friendly oxidants such as oxygen or air and environmentally safe solvents, such as water, produced in a sustainable process Terpencarbonsäuren.

The object of the present invention is thus to provide a process which uses a long-term stable and easily recyclable catalyst with a very high catalyst productivity and at the same time good yields and selectivities under mild reaction conditions with reaction temperatures <100 ⁰ C and slightly basic pH supplies.

Surprisingly, in the investigation of the selective oxidation of terpene alcohols or terpene aldehydes in the liquid phase, it has been found that Au-containing catalysts yield the corresponding carboxylic acids while retaining the double bond with high conversions and product selectivities.

The inventive method fulfills the stated object and relates to a process for the oxidation of terpenes in the liquid phase in the presence of a gold-containing supported catalyst by an oxygen-containing gas to the corresponding terpene carboxylic acids.

Preferably, terpene alcohols or terpene aldehydes are used according to the invention.

As terpene alcohols are in particular primary terpene alcohols, such. Geraniol, nerol, citronellol, dihydrocitronellol, lavandulol, famesol, myrtenol, lanceol, phytol, plaunotol, betulenol, khusol, drimenol, santalol, geranylgeraniol, all-trans-retinol or 3,4-dehydroretinol in question.

When terpene aldehydes are used as starting materials, Geranial, Neral, Citronellal, Myrtenal, Xanthoxin, Walburganal, Polygodial or Eleganonal are particularly preferably used. The starting sterene of the formula (1) is preferably used in concentrations of from 0.01 mol / l to 10 mol / l, in particular from 0.1 mol / l to 2 mol / l.

The gold-containing catalysts used in the method according to the invention preferably contain 0.1 to 10 wt .-% Au and 0.1 to 10 wt .-% of one or more noble metals from the group: Rh, Ru, Ir, Pd, Pt and / or Ag , applied to an oxidic carrier material. The precious metals or precious metal combinations are mainly present in the oxidation state 0. The oxidic support materials include Al ₂ O ₃ , TiO ₂ , SiO ₂ , aluminosilicates, ZrO ₂ , CeO ₂ , Y ₂ O ₃ , Nb ₂ O ₃ , zeolites and mesoporous materials such as MCM-41, SBA-15. The support of the gold particles on oxidic support materials improves the properties of the catalysts used compared with carbonaceous support materials, such as activated carbon, carbon black and organic carriers. They can be recycled several times, they are easily separable from the products and long-term stability against oxidation and leaching. This advantage is evident when compared to noble metal nanoparticles embedded in organic polymers which show strong leaching or lack of stability under reaction conditions in liquid-phase oxidations with molecular oxygen (A. Biffis, L. Minati, J. Catal., 236 (2005) 405). The gold catalyst used increases the yield and the selectivity of the oxidation to the terpene carboxylic acids.

As the oxidizing agent, an oxygen-containing gas, preferably pure oxygen, air or mixtures of oxygen and intergass, e.g. Nitrogen or argon used.

The oxygen content of the oxygen-containing gas is preferably between 5% and 99%, in particular in the range of 20% to 99%. In a preferred embodiment, the oxygen-containing gas is introduced at pressures of from 1 bar to 20 bar into the reaction solution.

The process according to the invention can be carried out in the solvent which is preferable for ecological and safety reasons. Oxygen or air or oxygen / l nertgas mixtures already react at Normal pressure. The process according to the invention is preferably carried out at atmospheric pressure. However, the use of higher pressure up to 10 bar is not excluded. In order to achieve good oxygen availability in the aqueous phase, the gas stream should be added via a gassing stirrer. By the speed of the gas stream, the turnover can be controlled. Preference is given to operating at a pressure in the range from 1 bar to 5 bar, wherein the oxygen-containing gas is introduced at a rate of 10 ml / min to 5000 ml / min.

With the inventive method terpene carboxylic acids, for example, in an aqueous medium in the pH range of pH 8 to pH 12, in particular in the range of pH 8 to pH 9, and at temperatures between 5 ° C and 120 ⁰ C, in particular from 50 ⁰ C to 9O ⁰ C are prepared. The reaction also proceeds in the more alkaline pH range, but side reactions such as the Aldol and Cannizzaro reactions are favored, resulting in poorer product selectivity.

As solvents for the process according to the invention, for example, aliphatic alcohols having 1 to 5 carbon atoms, halogenated hydrocarbons having 1 to 10 carbon atoms or aromatic

Hydrocarbons having 6 to 10 carbon atoms are used. Preferably, water is used as the solvent.

The inventive method is characterized in that high catalyst productivities of 7350 mol _Rea ι _<tand / Molκataiysator for a batch

An attempt can be made in the case of the oxidation of citronellal and the catalyst productivity can be significantly increased by recycling the catalyst.

The invention will be explained in more detail by examples, which should not be seen as limiting the invention. example 1

In a 1 l glass reactor equipped with a gassing stirrer, a heater and an automatic pH control, 0.05 mol of citronellol are dispersed in 400 ml of water. The mixture is adjusted with KOH to a pH of 9 and brought to a temperature of 80 ⁰ C. 1 g of catalyst (1% Au on Al ₂ O ₃ ) is added to the dispersion. With vigorous stirring, oxygen is introduced at a rate of 200 ml / min. The pH is kept constant over the entire reaction time of 5 h. Upon completion, cool to room temperature. The reaction solution is adjusted to pH 3 with dilute hydrochloric acid and extracted three times with 100 ml of dichloromethane each time. The organic solution is dried over Na ₂ SO ₄ and analyzed by HPLC (YMC Hydrosphere C18, 60:40 vol .-% acetonitrile / 0.1% aqueous trifluoroacetic acid).

Example 2

The procedure is as in Example 1, except that 0.05 mol of citronellal is used as the substrate.

Example 3 The procedure is as in Example 2, except that 0.15 mol of citronellal be used.

Example 4

The procedure is as in Example 3, except that no catalyst is used.

Example 5

The procedure is as in Example 2 except that working at pH 8.

Example 6 The procedure is as in Example 3 except that only 0.25 g of catalyst (1% Au on Al ₂ O ₃ ) are used. Example 7

The procedure is as in Example 2, except that the reaction is carried out at 60 ⁰ C.

Example 8

The procedure is as in Example 2, except that oxygen is passed through the reaction solution at a rate of 50 ml / min.

Example 9 The procedure is as in Example 2, except that air is passed through the reaction solution at a rate of 200 ml / min.

Example 10

The procedure is as in Example 2, except that 0.5% Au-0, 5% Pt on activated carbon is used as the catalyst.

Example 11

The procedure is as in Example 2, except that 0.05 mol of citral are used as the substrate.

Table 1

Examples 1 to 11: achieved conversions, yields and selectivities

Example 12

Catalyst Recycling: The experiment is carried out as described in Example 2. After completion of the catalyst is filtered off, washed several times with water and used in a new run. The recycling of the Catalyst was repeated over 6 reaction cycles. The conversions, yields and selectivities achieved are listed in Table 2.

Table 2

Example 12: Recycling Tests

Claims

claims 1. A process for the oxidation of terpenes in the liquid phase in the presence of a gold-containing supported catalyst by an oxygen-containing gas to the corresponding terpene carboxylic acids. 2. The method according to claim 1, characterized in that is used as Terpeπ a primary terpene alcohol or a terpene aldehyde. 3. The method according to claim 2, characterized in that as the primary terpene alcohol geraniol, nerol, citronellol, dihydrocitronellol, lavandulol, farnesol, myrtenol, lanceol, phytol, plaunotol, betulenol, khusol, drimenol, santalol, geranylgeraniol, all-trans-retinol or 3,4-dehydroretinol, more preferably geraniol, nerol or citronellol. 4. The method according to claim 2, characterized in that as terpene aldehyde Geranial, Neral, Citronellal, Myrtenal, Xanthoxin, Walburganal, Polygodial or Eleganonal, more preferably Geranial, Neral or Citronellal is used. 5. The method according to at least one of the preceding claims, characterized in that as the gold-containing catalyst, a material containing 0.1 to 10 wt .-% Au mainly in the oxidation state 0 and 0.1 to 10 wt .-% of one or more noble metals from the group: Rh, Ru, Ir, Pd, Pt and / or Ag is used mainly in the oxidation state 0. 6. The method according to at least one of the preceding claims, characterized in that the oxidic support material of the catalyst comprises one or more materials from the following group: Al ₂ O ₃ , TiO ₂ , SiO ₂ , aluminosilicates, ZrO ₂ , CeO ₂ , Nb ₂ θ ₃ , zeolites and / or mesoporous materials. 7. The method according to at least one of the preceding claims, characterized in that the terpene of the formula (1) is used in concentrations of 0.01 mol / l to 10 mol / l. 8. The method according to at least one of the preceding claims, characterized in that are used as the oxygen-containing gas molecular oxygen, air, mixtures of oxygen and an inert gas. 9. The method according to at least one of the preceding claims, characterized in that the oxygen content of the oxygen-containing gas is between 5% and 99%. 10. The method according to at least one of the preceding claims, characterized in that the oxygen-containing gas is introduced at pressures of 1 bar to 10 bar in the reaction solution. 11. The method according to claim 10, characterized in that the oxygen-containing gas is introduced at a pressure of 1 bar to 5 bar at a rate of 10 ml / min to 5000 ml / min in the reaction vessel. 12. The method according to at least one of the preceding claims, characterized in that the reaction is carried out at a pH of 8 to 12. 13. The method according to at least one of the preceding claims, characterized in that the reaction at temperatures of 5 ° C to 120 ⁰ C is performed. 14. The method according to at least one of the preceding claims, characterized in that as the solvent water, aliphatic alcohols having 1 to 5 carbon atoms, halogenated hydrocarbons having 1 to 10 Carbon atoms or aromatic hydrocarbons having 6 to 10 carbon atoms are used. 15. The method according to claim 14, characterized in that water is used as the solvent. 16. Catalyst containing 0.1 to 10 wt .-% Au mainly in the oxidation state 0 and 0.1 to 10 wt .-% of one or more noble metals from the group: Rh, Ru, Ir, Pd, Pt and / or Ag also mainly applied in the oxidation state 0 on an oxidic support material for oxidation reactions.