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WO2018112778A1 - Process for the preparation of levulinate esters - Google Patents

Process for the preparation of levulinate esters Download PDF

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Publication number
WO2018112778A1
WO2018112778A1 PCT/CN2016/111224 CN2016111224W WO2018112778A1 WO 2018112778 A1 WO2018112778 A1 WO 2018112778A1 CN 2016111224 W CN2016111224 W CN 2016111224W WO 2018112778 A1 WO2018112778 A1 WO 2018112778A1
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Prior art keywords
catalyst
process according
otf
triflate
furfuryl ether
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PCT/CN2016/111224
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French (fr)
Inventor
Alban CHAPPAZ
François JEROME
Karine De Oliveira Vigier
Eric Muller
Jonathan Lai
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Centre National de la Recherche Scientifique CNRS
Rhodia Operations SAS
Universite de Poitiers
Original Assignee
Centre National de la Recherche Scientifique CNRS
Rhodia Operations SAS
Universite de Poitiers
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Priority to PCT/CN2016/111224 priority Critical patent/WO2018112778A1/en
Publication of WO2018112778A1 publication Critical patent/WO2018112778A1/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters

Definitions

  • the present invention relates to a process for the preparation of levulinate esters starting from furfuryl ether in the presence of specific Lewis acid catalysts.
  • Levulinate esters such as alkyl levulinates
  • the acid-catalyzed ring opening of furfuryl alcohol in alcoholic media is a reaction of high interest yielding alkyl levulinates.
  • alkyl levulinates can be produced from furfuryl alcohol through an elegant 100%atom economical process.
  • the amount of furfuryl alcohol introduced in the process of said document is relatively low.
  • homogeneous or heterogeneous catalytic processes are conducted under diluted conditions (furfuryl alcohol loading of 2-3 wt%) .
  • a first object of the invention is a process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of the furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.
  • the catalyst further comprises at least one ligand selected from triflate, triflimidate, halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands, preferably selected from triflate, triflimidate and halogen, more preferably selected from triflate.
  • at least one ligand selected from triflate, triflimidate, halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands, preferably selected from triflate, triflimidate and halogen, more preferably selected from triflate.
  • the catalyst is selected from SnCl 4 , SnX 1 X 2 X 3 (OTf) . xH 2 O and MX 1 X 2 (OTf) . xH 2 O wherein:
  • M represents a metal selected from Bi, Ga and Al,
  • X 1 , X 2 , and X 3 represent independently to each other a ligand, preferably selected from triflate, halogen, alkoxy, sulfate, nitrate, carboxylate, -N (SO 2 CF 3 ) 2 , alkyl, aryl and metal ligands, more preferably from triflate and halogen ligands;
  • OTf represents a triflate
  • x ranges from 0 to 10.
  • the catalyst is selected from SnCl 4 , Bi (OTf) 3 and BiCl 2 OTf, preferably from Bi (OTf) 3 and BiCl 2 OTf.
  • the catalyst is in the form of a hydrate.
  • the reaction medium further comprises at least one solvent, preferably selected from alcohols.
  • the alcohol is selected from alcohols of formula R’ OH wherein R’ is selected from linear, branched, cyclic, saturated or unsaturated hydrocarbyl radicals.
  • R’ comprises from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 16 carbon atoms.
  • furfuryl ether is present in a quantity ranging from 5 to 50%by weight, preferably from 7 to 40%by weight, more preferably from 10 to 25%by weight, based on the total weight of the alcohols.
  • the furfuryl ether responds to the following formula:
  • R represents a hydrocarbyl radical, saturated or unsaturated, linear, branched or cyclic, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur.
  • ester levulinate (s) respond (s) to the following formulas (I) and/or (II) :
  • R is as defined in claim 10 and R’ is as defined above, and R and R’ may be identical or different.
  • the catalyst is present in an amount ranging from 0.05 to 20%mol, preferably ranging from 0.1 to 10%mol, more preferably ranging from 0.5 to 5%mol relative to the molar amount of furfuryl ether.
  • the molar ratio water/metal of the catalyst ranges from 0.1 to 20, preferably from 0.3 to 10, more preferably from 0.5 to 5.
  • the process comprises the following steps:
  • reaction mixture comprising all or part of the catalyst, all or part of the water, and optionally all or part of the solvents
  • the process further comprises a step of heating the reaction mixture obtained at the end of step a) to a temperature ranging from 80°C to 200°C, preferably from 100°C to 180°C, more preferably from 115°C to 165°C.
  • the process of the present invention allows obtaining a high yield of levulinate esters.
  • the process of the present invention allows reducing the amount of by-products that can be formed during the reaction.
  • the produced levulinate esters are stable and can be conveniently recovered from the reaction medium, for example by distillation, and the catalyst can be recycled for a further conversion reaction.
  • the present invention is directed to a process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of the furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.
  • furfuryl ether refers to an ether of the furfuryl alcohol. Furfuryl ether can be commercially available or synthetized according to well-known processes for the skilled person.
  • the furfuryl ether that can be used in the present invention can be represented by the following formula:
  • R represents a hydrocarbyl radical, saturated or unsaturated, linear, branched or cyclic, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur.
  • R represents a linear, branched or cyclic alkyl radical comprising from 1 to 24 carbon atoms or a linear, branched or cyclic alkenyl radical comprising from 2 to 24 carbon atoms.
  • R comprises from 1 to 16 carbon atoms, more preferably from 1 to 12 carbon atoms, even more preferably from 2 to 8 carbon atoms.
  • hydrocarbyl radical a radical comprising carbon atoms and hydrogen atoms, and optionally heteroatoms such as oxygen, nitrogen or sulfur. According to an embodiment, the hydrocarbyl radicals consist in carbon atoms and hydrogen atoms.
  • furfuryl ethers that can be used in the process of the invention, mention may be made of methyl furfuryl ether, ethyl furfuryl ether, propyl furfuryl ether, butyl furfuryl ether, or pentyl furfuryl ether.
  • the catalyst comprises at least one metal selected from bismuth, gallium, aluminum and tin, more preferably from bismuth, gallium and tin, even more preferably from bismuth and gallium or from bismuth.
  • the catalyst further comprises at least one ligand selected from triflate (OTf) , triflimidate (NTf 2 ) , halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands; preferably the catalyst comprises at least one ligand selected from triflate (OTf) , triflimidate (NTf 2 ) and halogen, more preferably from triflate.
  • OTf triflate
  • NTf 2 triflimidate
  • halogen alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands
  • the catalyst can be in a dimeric form, including for example a Bi-Bi or Bi-Pd bound.
  • halogen ligands mention may be made of chloride, bromide, fluoride or iodide ligands, and preferably chloride ligands.
  • alkoxy ligands of formula –OR’ wherein R’ represents an alkyl radical comprising from 1 to 24 carbon atoms or an alkenyl radical comprising from 2 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic and can optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain.
  • the alkoxy ligand is selected from methoxy, ethoxy, propoxy, butoxy ligands.
  • Tf represents a triflyl group also named trifluoromethanesulfonyl (CF 3 SO 3 -) . Therefore, NTf 2 represents the triflimidate radical -N (SO 2 CF 3 ) 2 .
  • alkyl ligands mention may be made of alkyl or alkenyl radicals having from 1 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic.
  • Alkyl ligands may optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain.
  • the alkyl ligand is selected from methyl, ethyl, propyl, butyl, pentyl, cyclopentadienyl ligands.
  • aryl radicals having from 6 to 24 carbon atoms
  • said aryl radical can be substituted by one or more substituents, such as alkyl or alkenyl having from 1 to 12 carbon atoms, said aryl radical can be bicyclic.
  • the aryl radical is selected from phenyl, benzyl, naphthenyl.
  • carboxylate ligands include carboxylate of formula -OCOR” wherein R” represents an alkyl radical comprising from 1 to 24 carbon atoms or an alkenyl radical comprising from 2 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic and can optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain.
  • carboxylate ligands are selected from methanoate, acetate, propanoate, butanoate ligands.
  • the catalyst is selected from SnCl 4 and catalysts comprising at least one metal M and at least one ligand OTf wherein
  • -M is selected from bismuth, gallium, aluminum, tin and iron, preferably from and bismuth, gallium, aluminum and tin, more preferably from bismuth and tin, even more preferably from bismuth;
  • -OTf is a triflate, also named trifluoromethanesulfonate (CF 3 SO 3 -) .
  • the catalyst may further comprise at least one organic ligand of type “L” , i.e. a neutral ligand that donate two electrons to the metal, the bond between these ligands and the metal is a coordinate bond.
  • organic ligand of type L mention may be made of phosphine ligands, in particular diphosphine ligands, such as 1, 2-bis (diphenylphosphino) ethane (DPPE) or diamine ligands, in particular bipyridine.
  • DPPE 1, 2-bis (diphenylphosphino) ethane
  • the presence of this kind of organic ligand may improve the selectivity towards levulinate esters and may allow introducing a higher amount of furfuryl alcohol in the reaction medium.
  • Ligands may also improve the solubility of the catalyst, the stability of the catalyst or the kinetics of the reaction.
  • the catalyst is selected from SnCl 4 , Bi (OTf) 3 , Bi (NTf 2 ) 3 , Ga (OTf) 3 , Al (OTf) 3 , Sn (OTf) 4 , and BiCl 2 ( OTf) , more preferably from Bi (OTf) 3 and BiCl 2 ( OTf) .
  • Catalysts that can be used in the process of the invention are commercially available or may be synthesized by processes well known for the skilled person.
  • the catalyst used in the process of the invention may be unsupported (homogeneous catalysis) or supported (heterogeneous catalysis) .
  • a supported catalyst facilitates the process and the recovery of the catalyst at the end of the reaction and does not change the catalysis cycle or the role of the catalyst during the reaction.
  • the support may be any support well known by the skilled person in the art, such as silica, alumina, zeolites or titanium-based solids, or metal oxides such as bismuth oxides, gallium oxides, tin oxides, aluminum oxides or iron oxides.
  • polystyrene resins acid oxides, such as niobium oxides, zeolites or sulfonated charcoals.
  • the catalyst may also be immobilized in a liquid phase.
  • one or more other catalysts different from the (Lewis acid) catalysts defined above may be also present in the reaction medium.
  • said other catalysts are selected from Bronsted acids, in particular strong Bronsted acids, such as triflic acid, perfluorosulfonic acid or Nafion is well known by the skilled person and can be defined as a sulfonated tetrafluoroethylene based fluoropolymer-copolymer.
  • the catalyst (s) is (are) present in an amount ranging from 0.05 to 5%mol, preferably ranging from 0.1 to 3%mol, more preferably ranging from 0.5 to 2%mol based on the molar amount of furfuryl ether.
  • the reaction takes place in the presence of a catalytic amount of water.
  • the reaction takes place with a molar ratio water/metal M (metal of the catalyst) ranging from 0.1 to 20, preferably from 0.3 to 10, more preferably from 0.5 to 5.
  • Water may for example be introduced into the reaction medium by an addition of (external) water or through the use of a catalyst in the form of a hydrate.
  • a SnCl 4 catalyst may be in the form of SnCl 4 .5H 2 O or a AlCl 3 catalyst may be in the form of AlCl 3 .6H 2 O.
  • the catalyst can also be in an anhydrous form.
  • the catalyst comprises triflate ligands
  • the catalyst will be preferably in an anhydrous form.
  • reaction medium By “reaction medium” , it is to be understood the medium wherein the reaction takes place.
  • the reaction medium comprises the furfuryl ether, the catalyst (s) , water, and optionally at least one solvent (different from furfuryl ether) .
  • the reaction medium is substantially free, or even totally free, of organic solvents different from alcohol solvents and the catalyst of the conversion reaction.
  • the main levulinate ester obtained may be:
  • the furfuryl ether may be purified before introduction into the reaction medium, by purification methods well known for the skilled person.
  • the furfuryl ether is present in a quantity of at least 5%by weight, preferably in an amount ranging from 5 to 50%by weight, more preferably from 7 to 40%by weight, even more preferably from 10 to 25%by weight, based on the total weight of the reaction medium.
  • the alcohol which can be used in the reaction medium for the conversion of furfuryl ether may be selected from aliphatic alcohols or aromatic alcohols, preferably from aliphatic alcohols.
  • An aliphatic alcohol is a non-aromatic alcohol.
  • An aromatic alcohol comprises a OH function directly linked to an aryl ring.
  • An example of an aromatic alcohol is a phenol.
  • the alcohol may be a monol or a polyol comprising for example from 2 to 5 OH functions or from 2 to 4 OH functions or from 2 to 3 OH functions, preferably the alcohol is a monol, i.e. an alcohol comprising only one OH function.
  • the alcohol is introduced through an alcoholic solution that may comprise one or several different alcohols, preferably the alcoholic solution comprises only one alcohol.
  • the alcoholic solution comprises a mixture of different alcohols
  • the levulinate esters obtained at the end of the reaction may be a mixture of different levulinate esters.
  • the alcohol is selected from primary alcohols, i.e. compounds comprising at least the following radical: -CH 2 -OH.
  • the alcohol is of formula R’ OH wherein R’ is selected from linear, branched, cyclic, saturated or unsaturated hydrocarbyl radicals.
  • the alcohol comprises from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 16 carbon atoms.
  • the alcohol is selected from methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, decanol, dodecanol.
  • the reaction is performed at a temperature ranging from 80°C to 200°C, preferably from 100°C to 180°C, more preferably from 115°C to 165°C.
  • the reaction is generally performed at a pressure such that the reactants remain in a liquid state.
  • the reaction is performed at a pressure ranging from 0.5 to 5 bars, preferably from 1 to 3 bars, more preferably at atmospheric pressure.
  • the process of the invention comprises the following steps:
  • reaction mixture comprising all or part of the catalyst, all or part of the water, and optionally all or part of the solvent
  • the reaction mixture obtained in step a) comprises all of the catalyst used in the reaction and/or all the water used in the reaction.
  • the reaction mixture, before step b) is heating to a temperature ranging from 80°C to 200°C, preferably from 100°C to 180°C, more preferably from 115°C to 165°C. This heating step may help for the preparation of the catalyst.
  • water is added into the reaction mixture before step b) and before the heating of said reaction mixture if any.
  • all the furfuryl ether is introduced during step b) .
  • furfuryl ether is mixed with the remaining part of the solvents before its introduction into the reaction mixture obtained in step a) .
  • the process of the reaction may be a batch process or a continuous process.
  • furfuryl ether may be sequentially or continuously introduced into the reaction mixture obtained at step a) .
  • the sequentially or continuously addition allows improving the selectivity towards levulinate esters and allows loading a higher amount of furfuryl ether into the reaction medium.
  • levulinate esters and other products can be recovered and isolated, for example by distillation.
  • the catalyst may be recycled for performing another reaction and another process.
  • the reaction can be followed by gas chromatography or by HPLC (high performance liquid chromatography) or also by 1 H or 13 C NMR (Nuclear magnetic resonance) , according to well-known methods for the skilled person; and the reaction is preferably stopped when all the furfuryl ether has been converted in situ.
  • the process of the invention generally leads to a yield in levulinate ester of at least 40%mol, preferably at least 45%mol, more preferably at least 50%mol, based on moles of furfuryl ether in the reaction medium.
  • Samples (0.1 g) were taken from the reaction mixture after different times and quenched with 1.1 g of isopropanol. An aliquot of the sample was filtered on Nylon Acrodisc 0.2 ⁇ m and analysed by GC without any further treatments.
  • the catalyst is present in an amount of 1%mol.
  • the main levulinate ester obtained at the end of the reaction is the butyl levulinate.
  • the yield (or selectivity) in levulinate esters corresponds to the amount of levulinate esters expressed in molar percentage based on the molar amount of furfuryl ether introduced into the reaction medium.
  • the Lewis acid catalyst based on Bi allows the production of alkyl levulinates with a yield improved as compared to acid catalysts based on In or Sc and also with an improved yield as compared to triflic acid catalyst.

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Abstract

The present invention is directed to a process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.

Description

PROCESS FOR THE PREPARATION OF LEVULINATE ESTERS TECHNICAL FIELD
The present invention relates to a process for the preparation of levulinate esters starting from furfuryl ether in the presence of specific Lewis acid catalysts.
BACKGROUND ART
Levulinate esters, such as alkyl levulinates, are industrially relevant solvents or intermediates for the manufacture of pesticides, plasticizers, polymers or fuel additives. The acid-catalyzed ring opening of furfuryl alcohol in alcoholic media is a reaction of high interest yielding alkyl levulinates.
In contrast to the classical route involving 5-hydroxymethylfurfural (HMF) as a starting reagent or intermediate, alkyl levulinates can be produced from furfuryl alcohol through an elegant 100％atom economical process.
The selectivity of this reaction is rather low due to the dominant acid-catalyzed side polymerization of furfuryl alcohol leading to an important formation of tar.
J.R. Kean and A.E. Graham, Catalysis Communications 59 (2015) 175-179, discloses a method for synthesizing alkyl levulinates from furfuryl alcohols using Indium (III) triflate catalysts. The amount of furfuryl alcohol introduced in the process of said document is relatively low. To inhibit side polymerization reactions, previously reported homogeneous or heterogeneous catalytic processes are conducted under diluted conditions (furfuryl alcohol loading of 2-3 wt％) .
It was thus an object of the present invention to develop a process for obtaining levulinate esters with a process that permits to get very high selectivities.
SUMMARY OF THE INVENTION
A first object of the invention is a process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of the furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.
According to an embodiment of the invention, the catalyst further comprises at least one ligand selected from triflate, triflimidate, halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands,  preferably selected from triflate, triflimidate and halogen, more preferably selected from triflate.
Preferably, the catalyst is selected from SnCl4, SnX1X2X3 (OTf) . xH2O and MX1X2 (OTf) . xH2O wherein:
M represents a metal selected from Bi, Ga and Al,
X1, X2, and X3 represent independently to each other a ligand, preferably selected from triflate, halogen, alkoxy, sulfate, nitrate, carboxylate, -N (SO2CF3) 2, alkyl, aryl and metal ligands, more preferably from triflate and halogen ligands；
OTf represents a triflate； and
x ranges from 0 to 10.
According to a preferred embodiment, the catalyst is selected from SnCl4, Bi (OTf) 3 and BiCl2OTf, preferably from Bi (OTf) 3 and BiCl2OTf.
According to an embodiment of the invention, the catalyst is in the form of a hydrate.
According to an embodiment of the invention, the reaction medium further comprises at least one solvent, preferably selected from alcohols. Preferably, the alcohol is selected from alcohols of formula R’ OH wherein R’ is selected from linear, branched, cyclic, saturated or unsaturated hydrocarbyl radicals. According to an embodiment, R’ comprises from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 16 carbon atoms.
According to an embodiment of the invention, furfuryl ether is present in a quantity ranging from 5 to 50％by weight, preferably from 7 to 40％by weight, more preferably from 10 to 25％by weight, based on the total weight of the alcohols.
According to an embodiment of the invention, the furfuryl ether responds to the following formula:
Figure PCTCN2016111224-appb-000001
wherein R represents a hydrocarbyl radical, saturated or unsaturated, linear, branched or cyclic, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur.
According to an embodiment of the invention, the ester levulinate (s) respond (s) to the following formulas (I) and/or (II) :
Figure PCTCN2016111224-appb-000002
wherein R is as defined in claim 10 and R’ is as defined above, and R and R’ may be identical or different.
According to an embodiment of the invention, the catalyst is present in an amount ranging from 0.05 to 20％mol, preferably ranging from 0.1 to 10％mol, more preferably ranging from 0.5 to 5％mol relative to the molar amount of furfuryl ether.
According to an embodiment of the invention, the molar ratio water/metal of the catalyst ranges from 0.1 to 20, preferably from 0.3 to 10, more preferably from 0.5 to 5.
According to an embodiment of the invention, the process comprises the following steps:
a) providing a reaction mixture comprising all or part of the catalyst, all or part of the water, and optionally all or part of the solvents,
b) introducing all or part of the furfuryl ether and optionally the remaining part of the solvents into the reaction mixture in order to synthesize the levulinate esters,
c) recovering the levulinate esters.
Preferably, the process further comprises a step of heating the reaction mixture obtained at the end of step a) to a temperature ranging from 80℃ to 200℃, preferably from 100℃ to 180℃, more preferably from 115℃ to 165℃.
The process of the present invention allows obtaining a high yield of levulinate esters.
The process of the present invention allows reducing the amount of by-products that can be formed during the reaction.
The produced levulinate esters are stable and can be conveniently recovered from the reaction medium, for example by distillation, and the catalyst can be recycled for a further conversion reaction.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of the furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.
Within the meaning of the present invention, the term “furfuryl ether” refers to an ether of the furfuryl alcohol. Furfuryl ether can be commercially available or synthetized according to well-known processes for the skilled person.
The furfuryl ether that can be used in the present invention can be represented by the following formula:
Figure PCTCN2016111224-appb-000003
wherein R represents a hydrocarbyl radical, saturated or unsaturated, linear, branched or cyclic, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur. Preferably, R represents a linear, branched or cyclic alkyl radical comprising from 1 to 24 carbon atoms or a linear, branched or cyclic alkenyl radical comprising from 2 to 24 carbon atoms.
According to an embodiment, R comprises from 1 to 16 carbon atoms, more preferably from 1 to 12 carbon atoms, even more preferably from 2 to 8 carbon atoms.
By “hydrocarbyl radical” , it is to be understood a radical comprising carbon atoms and hydrogen atoms, and optionally heteroatoms such as oxygen, nitrogen or sulfur. According to an embodiment, the hydrocarbyl radicals consist in carbon atoms and hydrogen atoms.
Among furfuryl ethers that can be used in the process of the invention, mention may be made of methyl furfuryl ether, ethyl furfuryl ether, propyl furfuryl ether, butyl furfuryl ether, or pentyl furfuryl ether.
Preferably, the catalyst comprises at least one metal selected from bismuth, gallium, aluminum and tin, more preferably from bismuth, gallium and tin, even more preferably from bismuth and gallium or from bismuth.
According to an embodiment of the invention, the catalyst further comprises at least one ligand selected from triflate (OTf) , triflimidate (NTf2) , halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands； preferably the catalyst comprises at least one ligand selected from triflate (OTf) , triflimidate (NTf2) and halogen, more preferably from triflate.
Among metal ligands, mention may be made of Re, Pd, Fe, Ga, Sm, Co, Bi. Indeed, the catalyst can be in a dimeric form, including for example a Bi-Bi or Bi-Pd bound.
Among halogen ligands, mention may be made of chloride, bromide, fluoride or iodide ligands, and preferably chloride ligands.
Among alkoxy ligands, mention may be made of alkoxy ligands of formula –OR’ wherein R’ represents an alkyl radical comprising from 1 to 24 carbon atoms or an alkenyl radical comprising from 2 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic and can optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain. According to a specific embodiment, the alkoxy ligand is selected from methoxy, ethoxy, propoxy, butoxy ligands.
As is well known for the skilled person, “Tf” represents a triflyl group also named trifluoromethanesulfonyl (CF3SO3-) . Therefore, NTf2 represents the triflimidate radical -N (SO2CF3) 2.
Among alkyl ligands, mention may be made of alkyl or alkenyl radicals having from 1 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic. Alkyl ligands may optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain. According to a specific embodiment, the alkyl ligand is selected from methyl, ethyl, propyl, butyl, pentyl, cyclopentadienyl ligands.
Among aryl ligands, mention may be made of aryl radicals having from 6 to 24 carbon atoms, said aryl radical can be substituted by one or more substituents, such as alkyl or alkenyl having from 1 to 12 carbon atoms, said aryl radical can be bicyclic.  According to a specific embodiment, the aryl radical is selected from phenyl, benzyl, naphthenyl.
Among carboxylate ligands, mention may be made of carboxylate of formula -OCOR” wherein R” represents an alkyl radical comprising from 1 to 24 carbon atoms or an alkenyl radical comprising from 2 to 24 carbon atoms, said alkyl and alkenyl radicals can be linear, branched or cyclic and can optionally comprise one or more heteroatoms, such as oxygen, sulfur or nitrogen, for example in a side chain. According to a specific embodiment, carboxylate ligands are selected from methanoate, acetate, propanoate, butanoate ligands.
According to an embodiment of the invention, the catalyst is selected from SnCl4 and catalysts comprising at least one metal M and at least one ligand OTf wherein
-M is selected from bismuth, gallium, aluminum, tin and iron, preferably from and bismuth, gallium, aluminum and tin, more preferably from bismuth and tin, even more preferably from bismuth；
-OTf is a triflate, also named trifluoromethanesulfonate (CF3SO3-) .
According to an embodiment of the invention, the catalyst may further comprise at least one organic ligand of type “L” , i.e. a neutral ligand that donate two electrons to the metal, the bond between these ligands and the metal is a coordinate bond. As an example of organic ligand of type L, mention may be made of phosphine ligands, in particular diphosphine ligands, such as 1, 2-bis (diphenylphosphino) ethane (DPPE) or diamine ligands, in particular bipyridine. The presence of this kind of organic ligand may improve the selectivity towards levulinate esters and may allow introducing a higher amount of furfuryl alcohol in the reaction medium. Ligands may also improve the solubility of the catalyst, the stability of the catalyst or the kinetics of the reaction.
According to an embodiment, the catalyst is selected from SnCl4, Bi (OTf) 3, Bi (NTf2) 3, Ga (OTf) 3, Al (OTf) 3, Sn (OTf) 4, and BiCl2 (OTf) , more preferably from Bi (OTf) 3 and BiCl2 (OTf) .
Catalysts that can be used in the process of the invention are commercially available or may be synthesized by processes well known for the skilled person.
The catalyst used in the process of the invention may be unsupported (homogeneous catalysis) or supported (heterogeneous catalysis) . A supported catalyst facilitates the process and the recovery of the catalyst at the end of the reaction and does  not change the catalysis cycle or the role of the catalyst during the reaction. The support may be any support well known by the skilled person in the art, such as silica, alumina, zeolites or titanium-based solids, or metal oxides such as bismuth oxides, gallium oxides, tin oxides, aluminum oxides or iron oxides. Among supports, mention may also be made of polystyrene resins, acid oxides, such as niobium oxides, zeolites or sulfonated charcoals.
The catalyst may also be immobilized in a liquid phase.
According to an embodiment, one or more other catalysts, different from the (Lewis acid) catalysts defined above may be also present in the reaction medium. Preferably, said other catalysts are selected from Bronsted acids, in particular strong Bronsted acids, such as triflic acid, perfluorosulfonic acid 
Figure PCTCN2016111224-appb-000004
 or 
Figure PCTCN2016111224-appb-000005
 Nafion is well known by the skilled person and can be defined as a sulfonated tetrafluoroethylene based fluoropolymer-copolymer.
The combination of said Bronsted acid with the Lewis acid catalyst defined above and used in the process of the invention provides a synergistic effect for improving the selectivity towards the levulinate esters.
According to an embodiment, the catalyst (s) is (are) present in an amount ranging from 0.05 to 5％mol, preferably ranging from 0.1 to 3％mol, more preferably ranging from 0.5 to 2％mol based on the molar amount of furfuryl ether.
The reaction takes place in the presence of a catalytic amount of water. According to an embodiment, the reaction takes place with a molar ratio water/metal M (metal of the catalyst) ranging from 0.1 to 20, preferably from 0.3 to 10, more preferably from 0.5 to 5.
Water may for example be introduced into the reaction medium by an addition of (external) water or through the use of a catalyst in the form of a hydrate. For example, a SnCl4 catalyst may be in the form of SnCl4.5H2O or a AlCl3 catalyst may be in the form of AlCl3.6H2O.
The catalyst can also be in an anhydrous form. When the catalyst comprises triflate ligands, the catalyst will be preferably in an anhydrous form.
The conversion takes place in a reaction medium. By “reaction medium” , it is to be understood the medium wherein the reaction takes place. The reaction medium  comprises the furfuryl ether, the catalyst (s) , water, and optionally at least one solvent (different from furfuryl ether) .
Among solvents that can be present in the reaction medium during the conversion reaction, mention may be made of alcohols, such as methanol, ethanol or butanol, aromatic solvents, such as toluene or xylene.
According to an embodiment, the reaction medium is substantially free, or even totally free, of organic solvents different from alcohol solvents and the catalyst of the conversion reaction.
The conversion reaction of furfuryl ether to levulinate ester may be represented by the following equation:
Figure PCTCN2016111224-appb-000006
If an alcohol solvent (of formula R’ OH) is present in the reaction medium during the reaction, the conversion reaction of furfuryl ether to levulinate ester may lead to a mixture of different levulinate esters, for example according to the following equation:
Figure PCTCN2016111224-appb-000007
If the alcohol R’ OH is present in a large excess, the main levulinate ester obtained may be:
Figure PCTCN2016111224-appb-000008
According to an embodiment, the furfuryl ether may be purified before introduction into the reaction medium, by purification methods well known for the skilled person.
The furfuryl ether is present in a quantity of at least 5％by weight, preferably in an amount ranging from 5 to 50％by weight, more preferably from 7 to 40％by weight, even more preferably from 10 to 25％by weight, based on the total weight of the reaction medium.
The alcohol which can be used in the reaction medium for the conversion of furfuryl ether may be selected from aliphatic alcohols or aromatic alcohols, preferably from aliphatic alcohols.
An aliphatic alcohol is a non-aromatic alcohol. An aromatic alcohol comprises a OH function directly linked to an aryl ring. An example of an aromatic alcohol is a phenol.
The alcohol may be a monol or a polyol comprising for example from 2 to 5 OH functions or from 2 to 4 OH functions or from 2 to 3 OH functions, preferably the alcohol is a monol, i.e. an alcohol comprising only one OH function.
According to an embodiment, the alcohol is introduced through an alcoholic solution that may comprise one or several different alcohols, preferably the alcoholic solution comprises only one alcohol. In the case wherein the alcoholic solution comprises a mixture of different alcohols, the levulinate esters obtained at the end of the reaction may be a mixture of different levulinate esters.
According to an embodiment, the alcohol is selected from primary alcohols, i.e. compounds comprising at least the following radical: -CH2-OH.
According to an embodiment, the alcohol is of formula R’ OH wherein R’ is selected from linear, branched, cyclic, saturated or unsaturated hydrocarbyl radicals.
According to an embodiment, the alcohol comprises from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 16 carbon atoms.
According to an embodiment, the alcohol is selected from methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, decanol, dodecanol.
According to an embodiment, the reaction is performed at a temperature ranging from 80℃ to 200℃, preferably from 100℃ to 180℃, more preferably from 115℃ to 165℃.
The reaction is generally performed at a pressure such that the reactants remain in a liquid state. Preferably, the reaction is performed at a pressure ranging from 0.5 to 5 bars, preferably from 1 to 3 bars, more preferably at atmospheric pressure.
According to an embodiment, the process of the invention comprises the following steps:
a) providing a reaction mixture comprising all or part of the catalyst, all or part of the water, and optionally all or part of the solvent,
b) introducing all or part of the furfuryl ether and optionally the remaining part of the other solvent into the reaction mixture in order to synthesize the levulinate esters,
c) recovering the levulinate esters.
According to an embodiment of the invention, the reaction mixture obtained in step a) comprises all of the catalyst used in the reaction and/or all the water used in the reaction.
According to an embodiment of the invention, the reaction mixture, before step b) , is heating to a temperature ranging from 80℃ to 200℃, preferably from 100℃ to 180℃, more preferably from 115℃ to 165℃. This heating step may help for the preparation of the catalyst.
According to an embodiment of the invention, water is added into the reaction mixture before step b) and before the heating of said reaction mixture if any.
According to an embodiment of the invention, all the furfuryl ether is introduced during step b) .
According to an embodiment, furfuryl ether is mixed with the remaining part of the solvents before its introduction into the reaction mixture obtained in step a) .
The process of the reaction may be a batch process or a continuous process. Indeed, furfuryl ether may be sequentially or continuously introduced into the reaction mixture obtained at step a) . The sequentially or continuously addition allows improving the selectivity towards levulinate esters and allows loading a higher amount of furfuryl ether into the reaction medium.
At the end of the reaction, levulinate esters and other products can be recovered and isolated, for example by distillation.
The catalyst may be recycled for performing another reaction and another process.
The reaction can be followed by gas chromatography or by HPLC (high performance liquid chromatography) or also by 1H or 13C NMR (Nuclear magnetic resonance) , according to well-known methods for the skilled person； and the reaction is preferably stopped when all the furfuryl ether has been converted in situ.
The process of the invention generally leads to a yield in levulinate ester of at least 40％mol, preferably at least 45％mol, more preferably at least 50％mol, based on moles of furfuryl ether in the reaction medium.
The following examples show the effectiveness of the process and further explain the process of the present invention.
EXAMPLES
Example 1: Comparison of different catalysts
The following experiment has been performed with several catalysts:
In a typical experiment, in a reactor, 4.5g of butanol (5.5 mL) , the catalyst (0.05 mmol, i.e. 0.01 eq. as compared to the ethyl furfuryl ether) and 0.185 g of water (10 mmol, i.e. 2 eq. as compared to the ethyl furfuryl ether) were stirred and heated to reflux (117℃) , in order to obtain an homogeneous liquid. Then 0.620 g of ethyl furfuryl ether (5 mmol) was introduced in the reactor.
Samples (0.1 g) were taken from the reaction mixture after different times and quenched with 1.1 g of isopropanol. An aliquot of the sample was filtered on Nylon Acrodisc 0.2 μm and analysed by GC without any further treatments.
For each experiment, the catalyst is present in an amount of 1％mol.
In the present case, since butanol is present in excess, the main levulinate ester obtained at the end of the reaction is the butyl levulinate.
The yield (or selectivity) in levulinate esters corresponds to the amount of levulinate esters expressed in molar percentage based on the molar amount of furfuryl ether introduced into the reaction medium.
Table 1: Characteristics of the process for different catalysts
Figure PCTCN2016111224-appb-000009
*to be compared to the release of 3 molecules of HOTf acid from M (OTf) 3. Productivity is calculated considering (3HOTf) ＝ 0.05mmol
As illustrated in table 1, the Lewis acid catalyst based on Bi allows the production of alkyl levulinates with a yield improved as compared to acid catalysts based on In or Sc and also with an improved yield as compared to triflic acid catalyst.

Claims (15)

  1. A process for synthesizing at least one levulinate ester, said process comprising a step of introducing furfuryl ether into a reaction medium and a step of conversion of the furfuryl ether into levulinate ester in the presence of water and at least one catalyst, said catalyst comprising at least one metal selected from bismuth, gallium, aluminum, tin and iron.
  2. The process according to claim 1, wherein the catalyst further comprises at least one ligand selected from triflate, triflimidate, halogen, alkoxy, sulfate, nitrate, carboxylate, alkyl, aryl, metal, hydroxide, hydride and acetylacetonate ligands, preferably selected from triflate, triflimidate and halogen, more preferably selected from triflate.
  3. The process according to claim 1 or 2, wherein the catalyst is selected from SnCl4, SnX1X2X3 (OTf) . xH2O and MX1X2 (OTf) . xH2O wherein:
    M represents a metal selected from Bi, Ga and Al,
    X1, X2, and X3 represent independently to each other a ligand, preferably selected from triflate, halogen, alkoxy, sulfate, nitrate, carboxylate, -N (SO2CF3) 2, alkyl, aryl and metal ligands, more preferably from triflate and halogen ligands；
    OTf represents a triflate； and
    x ranges from 0 to 10.
  4. The process according to any one of claims 1 to 3, wherein the catalyst is selected from SnCl4, Bi (OTf) 3 and BiCl2OTf, preferably from Bi (OTf) 3 and BiCl2OTf.
  5. The process according to any one of claims 1 to 4, wherein the catalyst is in the form of a hydrate.
  6. The process according to any one of claims 1 to 5, wherein the reaction medium further comprises at least one solvent, preferably selected from alcohols.
  7. The process according to claim 6, wherein the alcohol is selected from alcohols of formula R’ OH wherein R’ is selected from linear, branched, cyclic, saturated or unsaturated hydrocarbyl radicals.
  8. The process according to claim 7, wherein R’ comprises from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 16 carbon atoms.
  9. The process according to any one of claims 6 to 8, wherein furfuryl ether is present in a quantity ranging from 5 to 50％ by weight, preferably from 7 to 40％ by weight, more preferably from 10 to 25％ by weight, based on the total weight of the alcohols.
  10. The process according to any one of claims 1 to 9, wherein the furfuryl ether responds to the following formula:
    Figure PCTCN2016111224-appb-100001
    wherein R represents a hydrocarbyl radical, saturated or unsaturated, linear, branched or cyclic, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur.
  11. The process according to any one of claims 7 to 10, wherein the ester levulinate (s) respond (s) to the following formulas (I) and/or (II) :
    Figure PCTCN2016111224-appb-100002
    wherein R is as defined in claim 10 and R’ is as defined in one of claims 7 or 8, and R and R’ may be identical or different.
  12. The process according to any one of claims 1 to 11, wherein the catalyst is present in an amount ranging from 0.05 to 20％mol, preferably ranging from 0.1 to 10％mol, more preferably ranging from 0.5 to 5％mol relative to the molar amount of furfuryl ether.
  13. The process according to any one of claims 1 to 12, wherein the molar ratio water/metal of the catalyst ranges from 0.1 to 20, preferably from 0.3 to 10, more preferably from 0.5 to 5.
  14. The process according to any one of claims 1 to 13, comprising the following steps:
    a) providing a reaction mixture comprising all or part of the catalyst, all or part of the water, and optionally all or part of the solvents,
    b) introducing all or part of the furfuryl ether and optionally the remaining part of the solvents into the reaction mixture in order to synthesize the levulinate esters,
    c) recovering the levulinate esters.
  15. The process according to claim 14, further comprising a step of heating the reaction mixture obtained at the end of step a) to a temperature ranging from 80℃ to 200℃, preferably from 100℃ to 180℃, more preferably from 115℃ to 165℃.
PCT/CN2016/111224 2016-12-21 2016-12-21 Process for the preparation of levulinate esters Ceased WO2018112778A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236021A (en) * 1979-05-07 1980-11-25 The B. F. Goodrich Company Process for the manufacture of levulinic acid and esters
CN104959154A (en) * 2015-07-09 2015-10-07 南京林业大学 Catalyst for preparing levulinate ester and method for preparing levulinate ester by using catalyst

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236021A (en) * 1979-05-07 1980-11-25 The B. F. Goodrich Company Process for the manufacture of levulinic acid and esters
CN104959154A (en) * 2015-07-09 2015-10-07 南京林业大学 Catalyst for preparing levulinate ester and method for preparing levulinate ester by using catalyst

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HUANG, YAOBING ET AL.: "Microwave-assisted alcoholysis of furfural alcohol into alkyl levulinates catalyzed by metal salts", GREEN CHEMISTRY, vol. 18, no. 6, 22 October 2015 (2015-10-22), pages 1516 - 1523, XP055496509, ISSN: 1463-9262 *

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