DE102006037447A1 - Catalytic oxidation of terpenes with noble metal catalysts - Google Patents

Abstract

The invention relates to the 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 the oxidant. 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. High product selectivities of carboxylic acids are achieved in the pH range of 8 to 12, reaction temperatures of 5 to 120 ° C and pressures of 1 to 10 bar in quantitative conversions.

Description

The 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 oxidizing agent into the corresponding carboxylic acids. It can Terpenes of different oxidation states serve as reactants, for example, terpene alcohols or terpene aldehydes. The use of Noble metal catalysts is for the achievement of high product selectivity is essential.

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 Oil 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 an oxide catalyst with five metals ( JP 52019619 ). This reaction is less suitable for the temperature-sensitive terpenes, also because of the by-product problem.

Saturated linear and cyclic alcohols have been converted into the corresponding aldehydes and carboxylic acids with various oxidants, including oxygen, in the presence of Au-supported liquid phase catalysts. WO 2002/016298 ). 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: gene. 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 and had to be separated from polymer membranes after the reaction ( PGN Mertens, IFJ 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 splitting of the peracid can be problematic, it could in JP 2001011009 be achieved by pyrolysis under inert gas in aliphatic hydrocarbons as a solvent.

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 (C ₁ -C ₃ acids, to 25% water) as a solvent to the corresponding acids ( DE 4 435 332 ). Aldehydes could also be converted to carboxylic acids with oxygen or air in the presence of an amine or amine N-oxide promoter ( 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, but for the reaction is a consuming to produce and not commercially available phase transfer catalyst ([CH ₃ (nC ₈ H ₁₇ ) ₃ N] HSO ₄ ) is required difficult to separate ( Sato, M. Hyodo, J. Takagi, M. Aoki, R. Noyori, Tetrahedron Lett. 41 (2000) 1439 ). The classical alkaline iodine oxidation in the presence of alkali 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 process of carboxylic acid synthesis from aldehydes described ( 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 isolated from butyraldehydes with oxygen ( CS 223255 ), even in the presence of an alkali metal salt ( JP 55013225 ) getting produced. 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 was described by 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 CCl ₄ . 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.

For hemiacetals of mono- and oligosaccharides, gold on oxidic supports is also a suitable catalyst system for the aerobic oxidation to aldonic acids (US Pat. WO 2004/099 114 A8 ; H. Berndt, A. Martin, I. Pitsch, U. Pruess, KD Vorlog, Catal. Today 91-92 (2004) 191 ). The reaction requires an alkaline medium (pH 8-12). In the strongly alkaline medium, however, side reactions may occur in the oxidation of CH-acidic aldehydes (eg 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 ° 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. 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 solvent at 200 to 250 ° C is made JP 54061115 known. Stoichiometric processes for the oxidation of terpenes (s. JL Simonsen, The Terpenes, Cambridge University Press 1947 ) have the disadvantage of accumulating salt loads. The use of organic solvents also does not lead to sustainable processes.

Other methods of making terpene carboxylic acids, such as citronellic acid, are via microbial processes ( 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.

Summarized can be stated that in the zugäugigen literature so far no catalytic process of the selective oxidation of alcohols and Aldehydes with terpene structure exists, which with very high, for technical Applications of appropriate selectivity and using environmentally friendly oxidants such as oxygen or air and ecological harmless solvents, like water, produces terpene carboxylic acids in a sustainable process.

task Thus, it is the object of the present invention to provide a method provide a long-term stable and easy to recycle Catalyst used with a very high catalyst productivity and at the same time under mild reaction conditions with reaction temperatures <100 ° C and weak basic pH gives good yields and selectivities.

Surprisingly was found in the investigation of the selective oxidation of terpene alcohols or Terpene aldehydes in the liquid phase, that Au-containing catalysts under the corresponding carboxylic acids Preserve the double bond with high sales and product selectivities.

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

Preferably According to the invention terpene alcohols or terpene aldehydes used.

When Terpene alcohols are in particular primary terpene alcohols, e.g. Geraniol, nerol, citronellol, dihydrocitronellol, lavandulol, farnesol, 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, especially Geranial, Neral, Citronellal, Myrtenal, Xanthoxin, Walburganal, Polygodial or Eleganonal are preferred. 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 demonstrated by comparison with noble metal nanoparticles embedded in organic polymers, which exhibit 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.

When Oxidant becomes an oxygen-containing gas, preferably purer Oxygen, air or mixtures of oxygen and intergas, such as e.g. Nitrogen or argon used.

Of 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 at pressures of 1 bar to 20 bar in the reaction solution initiated.

The inventive method can in the from ecological and security reasons preferable solvent Water performed become. Oxygen or air or oxygen / inert gas mixtures react already at normal pressure. One works in the method according to the invention preferably at atmospheric pressure. The application higher Pressure up to 10 bar is not excluded. To a good one oxygen availability in the aqueous Phase to reach the gas stream should be added via a gassing become. Due to the speed of the gas stream, the sales to be controlled. Preferably, at a pressure in the range of 1 bar to 5 bar worked, the oxygen-containing gas with initiated at a rate of 10 ml / min to 5000 ml / min becomes.

With the method according to the invention can Terpene carboxylic acids e.g. in the aqueous Medium in the pH range from pH 8 to pH 12, especially in the range from pH 8 to pH 9, and at temperatures between 5 ° C and 120 ° C, in particular from 50 ° C up to 90 ° C getting produced. The reaction is also more alkaline pH range, however, side reactions, such as the aldol and favors the Cannizzaro reaction, which manifests itself in a poorer product selectivity.

When solvent for the inventive method can for example, aliphatic alcohols having 1-5 carbon atoms, halogenated hydrocarbons having 1-10 carbon atoms or aromatic hydrocarbons having 6-10 carbon atoms used become. Preferably, water is used as the solvent.

The inventive method is characterized in that high catalyst productivities of 7350 MOl _reactant / MOI _{catalyst can be achieved} for a batch experiment in the case of the oxidation of citronellal and the catalyst productivity can be significantly increased by recycling the catalyst.

The The invention will be explained in more detail by examples which are not as Limitation of Invention can be seen.

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 to pH 9 with KOH and brought to a temperature of 80 ° C. To the dispersion is added 1 g of catalyst (1% Au to Al ₂ O ₃ ). With vigorous stirring, oxygen at a rate of 200 ml / min initiated. 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

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

Example 3

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

Example 4

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

Example 5

It The procedure is as in Example 2, except that worked at pH 8 becomes.

Example 6

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

Example 7

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

Example 8

It The procedure is as in Example 2, except that oxygen with a Speed of 50 ml / min passed through the reaction solution becomes.

Example 9

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

Example 10

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

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: Sales achieved, yields and selectivities example 1 2 3 4 5 6 7 8th 9 10 11 X _terpene [%] 36 100 99.5 1 50 10 55.7 80 79 10 41 Y _acid [%] 6 85 10.1 0 12.6 7 32.5 40.8 36 4 20 S [%] 17 85 10 - 25 70 58 51 46 40 49

Example 12

Catalyst Screening: 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 experiments example 1 2 3 4 5 6 7 X _terpene [%] 100 100 95 90 87 81 77 Y _acid [%] 88 87 77 63.2 56.4 51.3 46.8 S [%] 88 87 81 70 65 63 61

Claims (16)

Process for the oxidation of terpenes in the liquid phase in the presence of a supported gold-containing catalyst by an oxygen-containing Gas to the corresponding terpene carboxylic acids. Method according to claim 1, characterized in that that as a terpene a primary Terpene alcohol or a terpene aldehyde is used. Method according to claim 2, characterized in that that as 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, particularly preferably geraniol, nerol or citronellol becomes. Method according to claim 2, characterized in that that as terpene aldehyde geranial, neral, citronellal, myrtenal, xanthoxin, Walburganal, Polygodial or Eleganonal, more preferably Geranial, Neral or citronellal, is used. Method according to at least one of the preceding Claims, characterized in that the gold-containing catalyst is a material containing 0.1 to 10% by weight of Au mainly in the oxidation state 0 and 0.1 to 10 wt .-% of one or more precious metals from the Group: Rh, Ru, Ir, Pd, Pt and / or Ag mainly in the oxidation state 0 is used. 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 O ₃ , Zeolites and / or mesoporous materials. Method according to at least one of the preceding Claims, characterized in that the terpene of formula (1) in concentrations from 0.01 mol / l to 10 mol / l is used. Method according to at least one of the preceding Claims, characterized in that as the oxygen-containing gas molecular Oxygen, air, mixtures of oxygen and an inert gas can be used. Method according to at least one of the preceding Claims, characterized in that the oxygen content of the oxygen-containing Gas between 5% and 99%. Method according to at least one of the preceding claims characterized in that the oxygen-containing gas at pressures of 1 bar to 10 bar is introduced into the reaction solution. Method according to claim 10, characterized in that that the oxygen-containing gas at a pressure of 1 bar to 5 bar at a rate of 10 ml / min to 5000 ml / min introduced into the reaction vessel becomes. Method according to at least one of the preceding Claims, characterized in that the reaction at a pH of 8-12 performed becomes. Method according to at least one of the preceding claims characterized in that the reaction is carried out at temperatures of 5 ° C to 120 ° C. Method according to at least one of the preceding Claims, characterized in that as the solvent water, aliphatic Alcohols with 1-5 carbon atoms, halogenated hydrocarbons with 1-10 carbon atoms or aromatic hydrocarbons with 6-10 carbon atoms are used. Method according to claim 14, characterized in that that as a solvent Water is used. Catalyst containing 0.1 to 10 wt .-% Au mainly in the oxidation state 0 and 0.1 to 10 wt .-% of one or more Precious metals from the group: Rh, Ru, Ir, Pd, Pt and / or Ag also mainly in the oxidation state 0 applied on an oxidic support material for oxidation reactions.