Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/23—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of oxygen-containing groups to carboxyl groups
  • C07C51/235—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of oxygen-containing groups to carboxyl groups of —CHO groups or primary alcohol groups

Definitions

• 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.
• 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.).
• Carrier catalysts in the liquid phase in the corresponding aldehydes and carboxylic acids transferred (WO 2002/016 298).
• 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.
• 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).
• 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.
• terpene carboxylic acids such as citronellic acid
• microbial methods S. Oda, T. Sugai, H. Ohta, Bull. Chem. Soc., Japan, 73 (2000) 2819.
• space-time yields are not sufficient for an industrial process.
• 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.
• 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.
• terpene alcohols or terpene aldehydes are used according to the invention.
• 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.
• 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.
• 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%.
• 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.
• 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.
• 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.
• 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.
• 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.
• water is used as the solvent.
• the inventive method is characterized in that high catalyst productivities of 7350 mol Rea ⁇ ⁇ tand / Mol ⁇ ataiysator for a batch
• citronellol 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).
• HPLC YMC Hydrosphere C18, 60:40 vol .-
• 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 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
• Example 2 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 2 The procedure is as in Example 2, except that 0.5% Au-0, 5% Pt on activated carbon is used as the catalyst.
• Example 2 The procedure is as in Example 2, except that 0.05 mol of citral are used as the substrate.
• 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.

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Citations (2)

• 2006
  • 2006-08-10 DE DE200610037447 patent/DE102006037447A1/de not_active Withdrawn
• 2007
  • 2007-06-14 WO PCT/EP2007/005231 patent/WO2008017342A1/de active Application Filing

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