Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
  • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
  • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
  • C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
  • C07C45/39—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a secondary hydroxyl group
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C47/00—Compounds having —CHO groups
  • C07C47/52—Compounds having —CHO groups bound to carbon atoms of six—membered aromatic rings
  • C07C47/575—Compounds having —CHO groups bound to carbon atoms of six—membered aromatic rings containing ether groups, groups, groups, or groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C47/00—Compounds having —CHO groups
  • C07C47/52—Compounds having —CHO groups bound to carbon atoms of six—membered aromatic rings
  • C07C47/575—Compounds having —CHO groups bound to carbon atoms of six—membered aromatic rings containing ether groups, groups, groups, or groups
  • C07C47/58—Vanillin
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
  • C07C51/367—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by introduction of functional groups containing oxygen only in singly bound form
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

• the present invention relates to the field of the preparation of mandelic aromatic compounds and aromatic aldehyde compounds obtained from said mandelic aromatic compounds. More particularly, the present invention relates to the preparation of aromatic hydroxymandelic compounds and the preparation of hydroxyaromatic aldehyde compounds.
• the mandelic group refers to the group - CHOH-COOH, which is present as a substituent on the aromatic ring of said mandelic aromatic compounds.
• the present invention relates more particularly to the preparation of p-hydroxymandelic acid, 4-hydroxy-3-methoxymandelic acid and 3-ethoxy-4-hydroxymandelic acid, as well as the preparation of vanillin and / or ethyl vanillin.
• Vanillin is obtained from natural sources such as lignin, ferulic acid but a significant part of vanillin and its derivatives is produced chemically. Numerous and varied methods of preparation are described in the literature (KIRK-OTHMER - Encyclopedia of Chemical Technology 24, pp 812-825, 4th edition (1997)).
• a conventional route to vanillin and its derivatives involves a glyoxylic acid condensation reaction on guaiacol in aqueous basic medium, to obtain 4-hydroxy-3-methoxymandelic acid. This product is then oxidized in basic medium to lead to vanillin.
• This conventional method is for example implemented in US Patent 2,640,083, which describes the condensation of guaiacol and sodium glyoxylate obtained by reaction of glyoxylic acid with sodium hydroxide.
• This conventional method operated in a basic medium leads to an adverse reaction consisting of the disproportionation of glyoxylic acid according to the known reaction of Canizzaro (production of glycolic acid and oxalic acid).
• This parallel reaction substantially affects the yield and selectivity of the condensation reaction.
• the implementation in the basic medium of the condensation and oxidation reactions suffers from the need to carry out neutralization steps by the use of a strong acid, usually sulfuric acid, both after of the condensation reaction after the condensation reaction.
• said neutralization steps generate a considerable amount of salts, generally sulphate salts, especially in the form of sodium sulphate salts Na 2 SO 4 , which should be treat later.
• the implementation of the condensation reaction in a very dilute aqueous medium also does not promote the treatment of salified aqueous effluents, generally sulphated, at the outlet of the condensation and oxidation reactors.
• the present invention relates to a process for preparing aromatic compound (s) mandelic (s) and compound (s) aldehyde (s) aromatic (s) to overcome the disadvantages encountered in the prior process.
• the process proposed by the Applicant does not operate, or only partially, in an alkaline medium and thus avoids the need to carry out at least one of the subsequent neutralization steps to the condensation and oxidation reactions.
• the method according to the present invention therefore has the major advantage of generating a significantly reduced amount of salt or even generate no salt at any stage of the process.
• the process of the invention generates no sulfate salt when neither the condensation reaction nor the oxidation reaction is carried out in a basic medium.
• the condensation reaction is also advantageously carried out in the absence of a solvent, in particular in the absence of water, which thus avoids the treatment of aqueous effluents in large quantities downstream of the process and an economy at the level of the installation of the process and equipment invested.
• the process according to the invention carried out under mild conditions, in the absence of an alkaline agent (at least for one or other of the condensation or oxidation reactions, preferably for the two reactions) and preferably The absence of water, at least with regard to the condensation reaction, is therefore more environmentally friendly.
• the subject of the present invention is a process for the preparation of aromatic compound (s) carrying at least one mandelic group -CHOH-COOH comprising a condensation reaction of at least one aromatic compound with glyoxylic acid or its derivatives, said condensation reaction being carried out substantially in the absence of any acid or base added to the reaction medium.
• the subject of the present invention is a process for the preparation of aromatic compound (s) carrying at least one mandelic group -CHOH-COOH comprising a condensation reaction of at least one aromatic compound with glyoxylic acid or its derivatives, said condensation reaction being carried out in the absence of a solvent and the glyoxylic acid being glyoxylic acid monohydrate.
• the present invention also relates to a process for the preparation of aromatic compound (s) carrying at least one mandelic group -CHOH-COOH comprising a condensation reaction of at least one aromatic compound with glyoxylic acid or its derivatives said condensation reaction being carried out in the presence of at least one catalyst selected from transition metal complexes having oxygenated ligands.
• said aromatic compound employed as a reagent in the condensation reaction is advantageously chosen from substituted benzenes, phenol and substituted phenols, heterocyclic aromatic compounds and polycyclic aromatic compounds.
• heterocyclic aromatic compounds 1,3-benzodioxole, 1-methylindole and benzofuran are preferred.
• naphthol is preferred.
• the substituted benzenes are preferably benzenes substituted with one or more groups selected from an alkyl, alkenyl, alkoxy, hydroxyalkyl, alkoxyalkyl, cycloalkyl, aryl, arylalkyl, hydroxyl group, nitro group, halogen atom, halogen group, and the like. or perhaloalkyl, a formyl group, an acyl group having 2 to 6 carbon atoms, a carboxylic group, an amino or amido group optionally substituted with one or two alkyl or phenyl groups. It should be noted that the carboxylic group can be esterified for example by an alkyl or phenyl group.
• the substituted benzenes are benzenes substituted with one or more alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy.
• the substituted benzenes are benzenes substituted with one, two or three methoxy groups. These are methoxybenzene (anisole), 1,2-dimethoxybenzene (veratrole) and 1,2,3-trimethoxybenzene, respectively.
• the aromatic compound is preferably chosen from substituted phenols.
• said substituted phenols have at least one para- position of the unsubstituted hydroxyl group.
• Substituted phenols are molecules in which the aromatic ring carries at least one hydroxyl group and also carries one or more other substituents. Generally, more than one substituent is defined as 2 to 4 substituents per aromatic ring. Any substituent may be present to the extent that it does not interfere with the condensation reaction.
• R represents one or more substituents, identical or different
• x number of substituents on one cycle, is an integer between 1 and 4,
• two R groups placed on two vicinal carbon atoms may form together with the carbon atoms which carry them a saturated, unsaturated or aromatic ring having from 5 to 7 atoms and optionally comprising one or more heteroatoms.
• the para position of the hydroxyl group is preferably free, that is to say free of a substituent.
• the groups R which are identical or different, represent an alkyl, alkenyl, alkoxy, hydroxyalkyl, alkoxyalkyl, cycloalkyl, aryl, arylalkyl, hydroxyl group, a nitro group, a halogen atom, a group halo or perhaloalkyl, a formyl group, an acyl group having 2 to 6 carbon atoms, a carboxylic group, an amino or amido group optionally substituted with one or two alkyl or phenyl groups.
• the carboxylic group can be esterified for example by an alkyl or phenyl group.
• alkylene when x is greater than 1, two R groups placed on two vicinal carbon atoms may be linked together by an alkylene, alkenylene or alkenylidene group having 3 to 5 carbon atoms to form a ring. saturated, unsaturated or aromatic having from 5 to 7 atoms: one or more (preferably 2 or 3) carbon atoms may be replaced by a heteroatom, preferably oxygen.
• alkyl is intended to mean a linear or branched hydrocarbon-based chain containing from 1 to 15 carbon atoms and preferably from 1 to 2 to 10 carbon atoms.
• alkoxy is meant an alkyl-O- group in which the term alkyl has the meaning given above.
• alkoxy groups are methoxy or ethoxy.
• alkenyl is meant a linear or branched hydrocarbon group having 2 to 15 carbon atoms, comprising one or more double bonds, preferably 1 to 2 double bonds.
• cycloalkyl is meant a cyclic hydrocarbon group comprising from 3 to 8 carbon atoms, preferably a cyclopentyl or cyclohexyl group.
• aryl is meant an aromatic mono- or polycyclic group, preferably mono- or bicyclic comprising from 6 to 12 carbon atoms, preferably phenyl or naphthyl.
• arylalkyl is meant a linear or branched hydrocarbon group bearing a monocyclic aromatic ring and comprising from 7 to 12 carbon atoms, preferably benzyl.
• two R groups placed on two vicinal carbon atoms may be linked together by an alkylene, alkenylene or alkenylidene group to form a saturated, unsaturated or aromatic ring having from 5 to 7 atoms forming so a bicycle.
• alkylene, alkenylene or alkenylidene group to form a saturated, unsaturated or aromatic ring having from 5 to 7 atoms forming so a bicycle.
• alkyl group linear or branched, having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl
• a linear or branched alkenyl group having from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms, such as vinyl, allyl,
• a linear or branched alkoxy group having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert butoxy, a phenyl group,
• halogen atom preferably a fluorine, chlorine or bromine atom.
• x is advantageously equal to 1 or 2 and more preferably equal to 1.
• the invention applies preferentially to the compounds corresponding to formula (I) in which R represents an alkyl group having from 1 to 4 carbon atoms and x is equal to 1 or an alkoxy group having from 1 to 4 carbon atoms and x is 1.
• the substituted phenols used preferentially are: ⁇ -cresol, m-cresol, 3-ethylphenol, 2-tert-butylphenol, guaiacol, and ketol.
• the compounds to which the process for preparing an aromatic compound carrying at least one mandelic group according to the invention is preferentially applied are guaiacol and guetol.
• a condensation reaction of at least one of the aromatic compounds described above is carried out with glyoxylic acid or its derivatives.
• the glyoxylic acid used in the condensation reaction can be used in all its forms, in particular in solid form or in dissolved form in aqueous solution.
• glyoxylic acid is used in monohydrate form, (CHO-CO 2 H, H 2 O).
• the derivatives of glyoxylic acid include, in particular, esters of glyoxylic acid, such as the methyl and ethyl esters of glyoxylic acid.
• alkaline salts of glyoxylic acid are not included among the glyoxylic acid derivatives according to the present invention.
• the alkali metal glyoxylates are conventionally obtained by reacting glyoxylic acid with an alkaline base in an aqueous medium.
• the process according to the invention is conducted in the absence of added base.
• the use of glyoxylic acid salt requires the steps of neutralization by the use of a strong acid, and generates a considerable amount of salts.
• the condensation reaction is carried out without a catalyst.
• the reaction is preferably carried out in the absence of a solvent.
• Glyoxylic acid monohydrate can be used as a reagent.
• the process for preparing an aromatic compound carrying at least one mandelic group -CHOH-COOH according to the invention is advantageously carried out in the presence of at least one catalyst.
• Said catalyst is added to the reaction medium in a catalytic amount.
• Said catalytic process can be carried out by homogeneous catalysis or by heterogeneous catalysis, preferably by homogeneous catalysis. It is carried out in the presence of at least one catalyst preferably chosen from the group consisting of compounds based on transition metals and rare earths, zeolites, clays, lanthanum phosphate (LaPO 4 ), oxides metals, in particular alkaline earth oxides, metal hydroxides.
• the transition metal catalysts are advantageously selected from transition metal complexes having oxygenated ligands.
• the preferred transition metals are iron and copper. Zinc can also be used.
• the catalysts very advantageously employed for carrying out the preparation process according to the invention are iron (II) acetate (Fe (OAc) 2 ) and iron (III) acetate (Fe (OAc) 3 ) , copper (II) acetate (Cu (OAc) 2 ), iron (II) acetylacetonate (Fe (acac) 2 ) and iron (III) acetylacetonate (Fe (acac) 3 ), copper (II) acetylacetonate (Cu (acac) 2 ) and copper (III) acetylacetonate (Cu (acac) 3 ) and mixtures thereof.
• Glyoxylate and triflates are also advantageously employed as oxygenated ligands.
• the catalyst may be a complex consisting of a transition metal, preferably iron or copper, and at least one glyoxylate ligand.
• This complex can be formed in situ, when the transition metal catalyst is contacted with the reaction medium containing glyoxylic acid. Alternatively, this complex may be prepared prior to the condensation reaction.
• the process according to the invention may comprise a step prior to the condensation reaction which consists in mixing a compound based on transition metals with glyoxylic acid. This mixture is then brought into contact with at least one aromatic compound in the condensation reaction according to the invention.
• the catalytic compound can be formed in situ during the condensation reaction.
• the term catalyst can also broadly include the precursors of these catalytic compounds.
• the condensation reaction is conducted substantially in the absence of any acid and any base other than those constituted by the reactants and the catalyst, that is to say no acid neither any base is substantially introduced to the reaction medium other than the acids and bases constituted by the reactants and the catalyst.
• the ratio base / ⁇ is less than 10 mol%, preferably less than 5 mol%.
• the ratio of acid (s) / reagents in particular the ratio of acid (s) / (aromatic compound + glyoxylic acid or its derivatives ) is less than 10 mol%, preferably less than 5 mol%.
• the condensation reaction is conducted in the absence of any acid and any base other than those constituted by the reagents and the catalyst, that is to say that no acid or base is introduced.
• the reaction medium other than the acids and bases constituted by the reactants and the catalyst.
• the reaction medium does not contain a mineral base or organic base, and preferably the reaction medium does not contain NaOH, KOH, or ammonium hydroxide.
• the condensation reaction is carried out in the liquid phase or in the liquid-solid phase. Said reaction is carried out in the presence or absence of solvent. According to one embodiment, the reaction is carried out in the absence of a solvent.
• glyoxylic acid monohydrate can be used as a reagent. The water that can be released by glyoxylic acid monohydrate can not be considered as a solvent insofar as its amount is negligible. The glyoxylic acid monohydrate is solid up to about 50 ° C.
• the temperature of the condensation reaction may advantageously be between 30 ° C and 80 ° C, preferably between 40 ° C and 60 ° C, and even more preferably between 45 ° C and 50 ° C, and the medium
• the reaction is preferably stirred for the duration of the reaction to ensure sufficient homogenization of the medium.
• the reaction is carried out in the presence of a solvent.
• a solvent is, for example, water, an alcohol, in particular ethanol, an aromatic hydrocarbon such as xylene, or a water-alcohol mixture, for example a mixture water-ethanol, or else an ionic liquid, for example an ionic liquid chosen from quaternary ammonium salts (for example tetrabutylammonium salts), phosphonium salts (for example tetrabutylphosphonium salts), sodium salts, imidazolium (e.g., 1-alkyl-2,3-dimethylimidazolium salts, 1-alkyl-3-methylimidazolium salts) and pyridinium salts (e.g., 1-alkylpyridinium salts).
• quaternary ammonium salts for example tetrabutylammonium salts
• phosphonium salts for example tetrabutylphosphonium salts
• sodium salts imi
• the condensation reaction consists in reacting the glyoxylic acid or its derivatives with at least one aromatic compound as defined above.
• the molar ratio between the aromatic compound and the glyoxylic acid or its derivatives preferably varies between 0.1 and 4.0, more preferably between 0.5 and 2 and even more preferably it is close to 1 (that is, that is to say between 0.9 and 1, 1) so that the equimolar ratio between said aromatic compound and the glyoxylic acid or its derivatives avoids the recycling of one or the other of said reagents.
• the quantity of catalyst used expressed as the ratio between the number of moles of catalyst and the number of moles of glyoxylic acid (or its derivatives) or of aromatic compound (the one introduced in a smaller quantity, ie the limiting reagent), is advantageously chosen between 0.5 and 30%, very advantageously between 0.5 and 10%, preferably between 1 and 3%.
• the amount of catalyst used is advantageously chosen between 0.5 and 10%, preferably between 1 and 3% weight
• the temperature of the condensation reaction is preferably chosen between 0 ° C and 100 ° C, and preferably between 15 ° C and 80 ° C.
• the duration of the condensation reaction is between 1 minute and 24 hours.
• the reaction medium is preferably stirred for the duration of the reaction.
• the condensation reaction is conducted under pressure or at atmospheric pressure, under air or under a controlled atmosphere of inert gases, preferably nitrogen or possibly rare gases, in particular argon. We preferentially choose the air.
• inert gases preferably nitrogen or possibly rare gases, in particular argon. We preferentially choose the air.
• the process for the preparation of an aromatic compound carrying at least one mandelic group according to the invention may be carried out batchwise, semi-continuously or continuously.
• the condensation reaction can be carried out in different types of reactors, for example in a tubular reactor (plug flow reactor) or in a cascade of perfectly stirred reactors.
• a preferred embodiment of the process for preparing an aromatic compound carrying at least one mandelic group consists of carrying out the condensation reaction of glyoxylic acid with guaiacol or the condensation reaction of glyoxylic acid with guetol or the reaction. condensation of glyoxylic acid with guaiacol and guetol. In the first two cases, the condensation reaction leads to the production of a hydroxyl-substituted ortho-hydroxymandelic acid of the hydroxyl group respectively by a methoxy group (condensation of glyoxylic acid with guaiacol) and by an ethoxy group (condensation glyoxylic acid with guetol).
• the condensation reaction of glyoxylic acid with guaiacol and guetol leads to the co-production of a hydroxyl-substituted ortho-hydroxymandelic acid of the hydroxyl group by a methoxy group and a p-hydroxy acid.
• hydroxymandelic hydroxyl-substituted hydroxyl group with an ethoxy group
• One embodiment of the preparation process according to the invention advantageously consists in introducing the glyoxylic acid and the catalyst to said aromatic compound (s).
• the reaction medium is stirred for a time and at a temperature chosen in the abovementioned intervals.
• the reaction medium obtained at the end of the condensation reaction contains the mandelic aromatic compound (s) in acid form or in the form of a mandelic ester when an ester of glyoxylic acid is used as a reagent.
• Said reaction medium is substantially free of salt, preferably entirely free of salt.
• a separation of the products obtained at the end of the condensation is carried out.
• the mandelic aromatic compound (s) obtained (s) are separated from the reaction mixture according to standard separation techniques, in particular by crystallization. or by extraction with a suitable organic solvent.
• the (s) hydroxymandelic compound (s) substituted (s) obtained (s) at the end of said condensation reaction may be represented by the following formula (II):
• Another object of the invention is therefore a process for the preparation of aromatic aldehyde (s) comprising the condensation reaction as described above in the present description leading to the preparation of mandelic compound (s). followed by an oxidation reaction of the said mandelic compound (s). More preferably, when said aromatic compound used in said condensation reaction is a substituted phenol of formula (I) whose para position is free, the invention more particularly relates to a process for preparing 4-hydroxyaromatic aldehyde . More specifically, the subject of the invention is a process for the preparation of vanillin (VA or 4-hydroxy-3-methoxybenzaldehyde) and / or ethyl vanillin (EVA or 3-ethoxy-4-hydroxybenzaldehyde).
• VA vanillin
• EVA 3-ethoxy-4-hydroxybenzaldehyde
• oxidation herein refers to a decarboxylative oxidation as it includes the departure of a carboxylate group, forming carbon dioxide.
• the oxidation reaction used for carrying out the aromatic aldehyde preparation process according to the invention is advantageously carried out in the presence of oxygen or air.
• Said oxidation reaction is conducted at atmospheric pressure or under pressure. It is implemented either with addition of alkaline agent or without addition of alkaline agent. Preferably, it is carried out without addition of alkaline agent, that is to say that no base is introduced into the reaction medium subjected to the oxidation reaction.
• Said oxidation reaction is generally carried out in the presence of a solvent, which may be organic or aqueous. Water is advantageously used as a solvent.
• an ionic liquid as a solvent.
• Preferred ionic liquids are those already mentioned above for carrying out the condensation reaction. However, the presence of a solvent is not necessary. It is conducted at a temperature preferably between 10 and 200 ° C. At the end of said oxidation reaction, an aqueous reaction medium containing the said aromatic aldehyde (s) is generally recovered.
• Said oxidation reaction is conducted in the presence of a catalyst advantageously chosen from the derivatives of chromium, cobalt, copper, vanadium, manganese, iron, nickel and osmium.
• a catalyst advantageously chosen from the derivatives of chromium, cobalt, copper, vanadium, manganese, iron, nickel and osmium.
• the vanadium and copper derivatives are chosen and, preferably, the catalyst used for carrying out the said oxidation reaction is ammonium metavanadate (NH 4 VO 3 ) or vanadium oxide V 2 0 5 .
• the oxidation reaction may be carried out batchwise, semi-continuously or continuously. It can be conducted in different types of reactors, for example in a tubular reactor (plug flow reactor) or in a cascade of perfectly stirred reactors.
• a preferred embodiment of the process for preparing aromatic aldehyde according to the present invention consists in introducing water into the reaction medium resulting from said condensation reaction, said reaction medium having or not previously been separated, heating the aqueous medium. resulting in a temperature between 10 and 200 ° C, to introduce the oxidation catalyst and to bubble oxygen or air in said medium at atmospheric pressure or under pressure.
• Another preferred embodiment of the process for producing aromatic aldehyde according to the present invention consists in carrying out "one pot", that is to say in the same reactor, the condensation and oxidation reactions.
• a first "one pot” embodiment consists in carrying out said condensation reaction and then adding the an oxidation catalyst in the reaction medium once said condensation reaction has been carried out.
• a second “one pot” embodiment consists in placing the aromatic compound (s) with the glyoxylic acid or its derivatives in contact in a reaction medium comprising at least one catalytic catalyst.
• condensation and oxidation reactions for example a condensation catalyst and an oxidation catalyst, said condensation and oxidation catalysts being advantageously chosen from those detailed above in the present description.
• Said second mode can also be implemented in the presence of a single catalyst which ensures both the catalysis of the condensation reaction and that of the oxidation reaction.
• the aromatic aldehyde (s) is (are) obtained in an aqueous medium with various impurities.
• extraction of the said aromatic aldehyde (s) is preferably carried out. using an organic solvent.
• Said organic solvent solubilises said aromatic aldehyde (s) present in the aqueous medium. It is advantageous to use an organic solvent which is inert with respect to (ux) aldehyde (s) aromatic (s).
• a separation by recrystallization can be carried out but preferably a distillation of said mixture is carried out making it possible to obtain, for example at the top of the distillation, the solvent of extraction (if it is the most volatile compound of the mixture), and for example at the bottom of distillation, the said aromatic aldehyde (s), namely a mixture comprising essentially the (s) said aromatic aldehyde (s), associated with heavy impurities and small amounts of light impurities.
• the organic solvent used is advantageously recycled.
• the aromatic aldehyde (s) can be treated to form it in solid form.
• the purified aromatic aldehyde (s) preferably by distillation, followed by crystallization (using one or more solvents or by flaking technique), for example according to following steps :
• crystallization variants can be envisaged: for example discontinuous crystallization (batch) for example by cooling, or continuous crystallization, for example under vacuum.
• Another subject of the present invention is a process for the preparation of aromatic aldehyde (s) by oxidation of the corresponding mandelic derivative (s) ( s), said oxidation reaction being carried out in the presence of at least one oxidizing agent and at least one catalyst and substantially in the absence of any acid or base added to the reaction medium subjected to said reaction reaction. 'oxidation.
• mandelic derivative means an aromatic compound of which at least one hydrogen atom directly bonded to the aromatic ring is substituted by a group glycolic formula -CHOH-COOH.
• mandelic derivative means an aromatic compound of which at least two hydrogen atoms directly attached to the aromatic ring are substituted, one by a hydroxyl group and the other by a glycolic group of formula - CHOH-COOH.
• the said mandelic derivative (s) advantageously has the formula (II) explained above in the present description. It (s) is (are) obtained by condensation of at least one aromatic compound with glyoxylic acid or its derivatives.
• Said aromatic compound is advantageously chosen from those described above in the present description. Said condensation reaction is carried out in the presence of acid or base or substantially in the absence of any acid or base added to the reaction medium. By substantially, it means the same maximum amount of acid or base specified above in the present description.
• Said oxidation reaction is conducted in the presence of a catalyst advantageously chosen from the derivatives of chromium, cobalt, copper, vanadium, manganese, iron, nickel and osmium.
• a catalyst advantageously chosen from the derivatives of chromium, cobalt, copper, vanadium, manganese, iron, nickel and osmium.
• the vanadium and copper derivatives are chosen and, preferably, the catalyst used for carrying out the said oxidation reaction is ammonium metavanadate (NH 4 VO 3 ) or vanadium oxide V 2 0 5 .
• the catalytic compound can be formed in situ during the reaction.
• the term catalyst can also broadly include the precursors of these catalytic compounds.
• Another subject of the present invention is the use of a catalyst selected from transition metal complexes comprising oxygen ligands, rare earth-based compounds, zeolites , clays, lanthanum phosphate, metal oxides and metal hydroxides in carrying out a condensation reaction in which an organic compound and a carbonyl compound are contacted substantially in the absence of any acid or any base added to the reaction medium, said condensation reaction not generating the co-production of a single molecule.
• said organic compound is an aromatic compound chosen from substituted benzenes, phenol and substituted phenols, heterocyclic aromatic compounds and polycyclic aromatic compounds.
• the carbonyl compound generally comprises either an aldehyde function or a ketone function.
• Said metal complexes are used either by being supported or by being unsupported.
• the various metal complexes mentioned above in the present description are suitable for catalyzing said condensation reaction.
• Said condensation reaction implemented for the use according to the invention is similar to an addition reaction of said organic compound on said carbonyl compound. Said reaction leads to obtaining said adduct without production of a simple molecule such as water, hydrochloric acid, acetic acid, methanol or hydrogen sulphide.
• an amount of an aromatic compound is introduced which is heated to the temperature shown in Table 1.
• an amount of glyoxylic acid monohydrate in solid form and a catalytic amount of Fe (acac) 3 that is to say a quantity representing 2.5 mol% relative to limiting reagent.
• the amount of Fe (acac) 3 is such that it represents indifferently 2.5 mol% relative to one or the other. other of said two reagents.
• the reaction mixture is kept under magnetic stirring at the desired temperature for a time varying between 1 and 22 hours (see Table 1).
• the products of the condensation reaction are analyzed by high performance liquid chromatography. The results obtained are collated in Table 1.
• the conversion of the aromatic compound corresponds to the ratio between the number of moles of aromatic compound consumed and the number of moles of aromatic compound involved.
• the yield of mandelic compound corresponds to the ratio between the number of moles of mandelic compound formed and the number of moles of one or the other of reagents.
• Vanillylmandelic acid (1 mol / L) is introduced into a magnetically stirred 8 mL open vial containing a catalyst and a solvent.
• the catalyst concentration is 1 mol%, based on the number of moles of vanillylmandelic acid.
• the reaction is conducted at 80 ° C for 15 hours.
• Vanillylmandelic acid (0.1 mol / L) is introduced into a stirred reactor under pressure of 0 2 containing a catalyst (NH4V03) and a solvent (water).
• the catalyst concentration is 2.5 mol%, based on the number of moles of vanillylmandelic acid.
• the reaction is conducted at 80 ° C under 7 bar for 180 minutes.
• the degree of conversion of vanillylmandelic acid is 100% and the yield of vanillin is 93%.

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