WO2018107450A1

WO2018107450A1 - Electrochemical process for producing a propiolactone compound

Info

Publication number: WO2018107450A1
Application number: PCT/CN2016/110261
Authority: WO
Inventors: Renate Schwiedernoch; Gérard Mignani; Mengjia WU; Armin T. Liebens
Original assignee: Rhodia Operations; Centre National De La Recherche Scientifique
Priority date: 2016-12-16
Filing date: 2016-12-16
Publication date: 2018-06-21

Abstract

This invention provides an electrochemical process for producing a propiolactone compound comprising reacting a compound having at least one ethylenically unsaturated carbon-carbon double bond with carbon dioxide in the presence of an electrolyte, a solvent and a catalyst. Indeed, present invention makes it possible to directly transfer from carbon dioxide to propiolactone compound with high selectivity by a more simple process.

Description

Electrochemical process for producing a propiolactone compound

This invention provides an electrochemical process for producing a propiolactone compound comprising reacting a compound having at least one ethylenically unsaturated carbon-carbon double bond with carbon dioxide in the presence of an electrolyte, a solvent and a catalyst.

PRIOR ART

The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.

Carbon dioxide exists in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal is to take this carbon-trapped in a waste product and reuse it to build useful chemicals.

Use of carbon dioxide as a renewable one carbon (C1) building block in organic synthesis with olefins has already been reported. Electrochimica Acta, 56 (2011) , 1529–1534 reports an efficient electrochemical method for highly regioselective synthesis of unsaturated 1, 6-dioic acids from 1, 3-dienes and CO₂. In this reaction, the propiolactone is not produced.

J. Chem. Soc., Perkin I, 1981, 270-277 teaches a method for preparing lactones via tricarbonyliron-lactone complexes. However, the desired propiolactone is produced by three steps and each step needs isolation of the intermediate before the next step, which lead to a total yield of about 16％. Furthermore, the reactants employed, such as peracid, pentacarbonyliron and cerium ammonium nitrate are all unsafe and therefore special safe handling is necessary. The cost of commercialized production by this way would be really high because of the reasons mentioned above.

WO13164172 discloses a technology related to production of chemical compounds from carbon dioxide. This invention combines two steps: carbon dioxide electrolysis and “oxidative carbonylation” reaction. According to this technology, carbon dioxide needs to be split into carbon monoxide and oxygen first and “oxidative carbonylation” reaction of carbon monoxide and oxygen together with substrate is followed. Disadvantageously, in order to well control the gas streams, the requirement for reaction equipment and difficulty in operation is increased.

Thus, there is still a need for improved process for producing propiolactone compounds.

INVENTION

It is therefore an object of the present invention to provide a one-step electrochemical process for producing propiolactone compounds with desired characteristics such as inexpensiveness, high selectivity and conversion, ease of handling and overcome the drawbacks in prior arts.

The present invention provides an electrochemical process for the production of a propiolactone compound comprising reacting:

‐ a first reactant being a compound having at least one ethylenically unsaturated carbon-carbon double bond, with

‐ a second reactant being carbon dioxide, in the presence of an electrolyte, a solvent and a catalyst, wherein the catalyst comprises metal clusters comprising at least one metal element in elemental form, wherein the metal element is chosen in the group consisting of (i) elements of group IA, IIA, IIIA, IVA, VA, VIA and VIIA of the Periodic Table, (ii) elements of groups IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB of the Periodic Table, (iii) lanthanides, (iv) actinides, and (v) any combination thereof.

Indeed, present invention makes it possible to directly transfer from carbon dioxide to propiolactone compounds with high selectivity by a more simple process.

Other characteristics, details and advantages of the invention will emerge even more fully upon reading the description which follows.

DEFINITIONS

For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one" , unless otherwise specified, and "between" should be understood as being inclusive of the limits.

The articles “a” , “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The term “and/or” includes the meanings “and” , “or” and also all the other possible combinations of the elements connected to this term.

It is specified that, in the continuation of the description, unless otherwise indicated, the values at the limits are included in the ranges of values which are given.

As used herein, “electrochemical process” is a chemical reaction that either causes or is caused by the movement of electrical current.

As used herein and unless defined otherwise, the term "hydrocarbyl" refers to a monovalent hydrocarbon group, i.e. a group consisting of carbon atoms and hydrogen atoms, which group is connected to the remainder of the compound of formula (I) via a carbon-to-carbon single bond and may be saturated or unsaturated, linear, branched or cyclic, aliphatic or aromatic. A "C_1-11 hydrocarbyl" denotes a hydrocarbyl having 1 to 11 carbon atoms.

As used herein and unless defined otherwise, the term "alkyl" refers to a monovalent saturated aliphatic (i.e. non-aromatic) acyclic hydrocarbon group which may be linear or branched and does not comprise any carbon-to-carbon double bond or any carbon-to-carbon triple bond.

As used herein and unless defined otherwise, the term "alkenyl" refers to a monovalent unsaturated aliphatic acyclic hydrocarbon group which may be linear or branched and comprises at least one carbon-to-carbon double bond while it does not comprise any carbon-to-carbon triple bond.

As used herein and unless defined otherwise, the term "alkynyl" refers to a monovalent unsaturated aliphatic acyclic hydrocarbon group which may be linear or branched and comprises at least one carbon-to-carbon triple bond and optionally one or more carbon-to-carbon double bonds.

As used herein and unless defined otherwise, the term "cycloalkyl" refers to a monovalent cyclic saturated aliphatic hydrocarbon group which does not comprise any carbon-to-carbon double bond or any carbon-to-carbon triple bond. Non-limiting examples of cycloalkyl groups are cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

As used herein and unless defined otherwise, the term "cycloalkenyl" refers to a monovalent cyclic unsaturated aliphatic hydrocarbon group which comprises at least one carbon-to-carbon double bond and does not comprise any carbon-to-carbon triple bond. Non-limiting examples of cycloalkyl groups are cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl or cyclohexadienyl.

As used herein and unless defined otherwise, the term "aryl" refers to a monovalent aromatic hydrocarbon group, including bridged ring and/or fused ring systems, containing at least one aromatic ring. "Aryl" may, for example, refer to phenyl, naphthyl or anthracenyl.

As used herein, metals of group IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB are often referred to as transition metals. This group comprises the elements with atomic number 21 to 30 (Sc to Zn) , 39 to 48 (Y to Cd) , 72 to 80 (Hf to Hg) and 104 to 112 (Rf to Cn) .

As used herein, the term “Lanthanides” refer to metals with atomic number 57 to 71.

As used herein, the term “Actinides” refer to the metals with the atomic number 89 to 103.

As used herein, an “anode” is an electrode through which conventional current flows into a polarized electrical device.

As used herein, a “cathode” is the electrode from which a conventional current leaves a polarized electrical device.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of present application to the extent that it may render a term unclear, the present description shall take precedence.

DETAILS OF THE INVENTION

Propiolactone compound of present invention refers to a β-propiolactone compound, which is an organic compound with a four-membered ring.

With respect to first reactant of the process according to the invention, a compound having at least one ethylenically unsaturated carbon-carbon double bond, in particular, refers to a compound of formula (I) :

wherein R¹, R², R³ and R⁴ are each independently selected from hydrogen or C_1-11 hydrocarbyl.

Said hydrocarbyl is preferably selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, or aryl, more preferably selected from alkyl, alkenyl, alkynyl, or aryl, and even more preferably selected from alkyl, alkenyl, or aryl.

Said alkyl preferably comprises 1 to 11 carbon atoms, more preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 (i.e. 1, 2, 3 or 4) carbon atoms. Said alkenyl preferably comprises 2 to 11 carbon atoms, more preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 (i.e. 2, 3 or 4) carbon atoms. Said alkynyl preferably comprises 2 to 11 carbon atoms, more preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 (i.e. 2, 3 or 4) carbon atoms. Said cycloalkyl preferably comprises 3 to 11 carbon atoms, more preferably 3 to 8 carbon atoms, and even more preferably 3 to 6 (i.e. 3, 4, 5 or 6) carbon atoms. Said aryl is preferably selected from phenyl or naphthyl, and is more preferably phenyl.

Accordingly, said C_1-11 hydrocarbyl is preferably selected from C_1-11 alkyl (in particular, C_1-6 alkyl or C_1-4 alkyl) , C_2-11 alkenyl (in particular, C_2-6 alkenyl or C_2-4 alkenyl) , C_2-11 alkynyl (in particular, C_2-6 alkynyl or C_2-4 alkynyl) , C_3-11 cycloalkyl (in particular, C_3-6 cycloalkyl) , C_3-11 cycloalkenyl (in particular, C_3-6 cycloalkenyl) , phenyl or naphthyl. More preferably, said C_1-11 hydrocarbyl is selected from C_1-11 alkyl (in particular, C_1-6 alkyl or C_1-4 alkyl) , C_2-11 alkenyl (in particular, C_2-6 alkenyl or C_2-4 alkenyl) or phenyl.

In a preferred embodiment, R¹, R², R³ and R⁴ are each independently selected from hydrogen, C_1-11 alkyl, C_2-11 alkenyl, C_2-11 alkynyl, C_3-11 cycloalkyl, C_3-11 cycloalkenyl, phenyl or naphthyl, and are more preferably each independently selected from hydrogen, C_1-6 alkyl, C_2-6 alkenyl or phenyl, and are even more preferably each independently selected from hydrogen or linear C_1-4 alkyl.

In a specific preferred embodiment, at least one of R¹, R², R³ and R⁴ of formula (I) is hydrocarbyl and preferably alkyl and more preferably linear C_1-4 alkyl.

In general, it is preferred that the compound of formula (I) comprises a total of 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms and even more preferably 2 to 12 carbon atoms.

With respect to the product of the process according to the invention, the propiolactone compound according to the present invention may notably be a compound of formula (II) or formula (III) when compound of formula (I) is employed as starting reactant:

In one particular embodiment, compound of formula (I) may be a compound having conjugated double bonds of formula (IV) :

R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ have the same meanings and preferred meanings as described and defined herein above for R¹, R², R³ and R⁴.

It is preferred that the compound of formula (IV) comprises a total of 4 to 30 carbon atoms, more preferably 6 to 20 carbon atoms and even more preferably 6 to 12 carbon atoms.

In a specific preferred embodiment, at least one of R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ of formula (IV) is hydrocarbyl and preferably alkyl and more preferably linear C_1-4 alkyl.

It is to be understood that all stereoisomers of the compound of formula (I) or formula (IV) can be used in the method according to the invention, either in admixture or in pure or substantially pure form. Furthermore, the compound of formula (I) or formula (IV) encompasses both cis-isomers and trans-isomers.

With respect to the product of the process according to the invention, the propiolactone compound according to the present invention may notably be a compound of formula (V) or formula (VI) when compound of formula (IV) is employed as starting reactant:

Preferred examples of first reactant may be chosen in the group consisting of 1, 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, isoprene, myrcene, styrene, alpha-methylstyrene and 1-pheny-l, 3-butadiene.

Preferred examples of propiolactone compound may be chosen in the group consisting of 3-methyl-3- (prop-1-en-2-yl) oxetan-2-one, 3- (4-methylpent-3-1-yl) -3-vinyloxetan-2-one, 3- (6-methylhepta-1, 5-dien-2-yl) oxetan-2-one, 3, 3-dimethyl-4- (3-methylenepent-4-en-1-yl) oxetan-2-one, 3-vinyloxetan-2-one, 3-methyl-3-vinyloxetan-2-one, 3- (prop-1-en-2-yl) oxetan-2-one, 3-methyl-3-phenyloxetan-2-one, 3-styryloxetan-2-one and 4-phenyl-3-vinyloxetan-2-one.

Preferred reactions of the present invention are the following:

‐ Reaction of 1, 3-butadiene and carbon dioxide to produce 3-vinyloxetan-2-one.

‐ Reaction of 2, 3-dimethyl-1, 3-butadiene and carbon dioxide to produce 3-methyl-3- (prop-1-en-2-yl) oxetan-2-one.

As previously expressed, the catalyst comprises metal clusters comprising at least one metal element in elemental form, wherein the metal element is chosen in the group consisting of (i) elements of group IA, IIA, IIIA, IVA, VA, VIA and VIIA of the Periodic Table, (ii) elements of groups IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB of the Periodic Table, (iii) lanthanides, (iv) actinides, and (v) any combination thereof.

In present invention, hydrogen is not included in metal element chosen in Group IA of the Periodic Table. Carbon is not included in metal element chosen in Group IVA of the Periodic Table. Nitrogen and phosphorus are not included in metal element chosen in Group VA of the Periodic Table. Oxygen, sulfur and selenium are not included in metal element chosen in Group VIA of the Periodic Table.

In one embodiment, the catalyst of present invention may comprise at least one metal element in elemental form chosen in the group consisting of elements of groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, VIIIB and any combination thereof. Preferably, the metal element could be chosen in the group consisting of nickel, cobalt, tin, iron, aluminum, chromium, platinum, palladium, rhodium, ruthenium, iridium, silver, gold, cerium, bismuth, manganese, rhenium and copper and more preferably chosen in the group consisting of nickel, cobalt, copper, iron and chromium.

In another embodiment, the catalyst of present invention may comprise a metal alloy comprising at least two metal elements in elemental form, which is chosen in the group consisting of elements of groups IB, IIB, VIIIB. The metal alloy may be notably chosen in the group consisting of Au-Fe, Au-Ni, Cu-Ni, Cu-Fe and Ni-Fe.

A metal alloy can be viewed as a solid metal-solid metal mixture wherein a primary metal acts as solvent while other metal (s) act (s) as solute； in a metal alloy and wherein the concentration of the metal solute does not exceed the limit of solubility of the metal solvent.

The term clusters, as used herein, refers to small, multiatom particles. Normally, any particle of somewhere between 2 and 3×10⁷ atoms is considered a cluster. Preferably, number of metal atoms which form clusters of present invention could comprise 2 to 50000 atoms and preferably 3 to 3000 atoms.

Preferably, the average particle diameter of metal clusters may be comprised from 1nm to 10nm and more preferably from 1.5nm to 3nm.

The average particle diameter of metal clusters may be up to 10nm as reported by Endeavour (1990) , 14, pp. 172-178 and J. Mol. Catal. A: Chem. (1999) , 145, pp. 1-44. Preferably, it may be comprised from 1nm to 10nm and more preferably from 1.5nm to 3nm as observed by transmission eletron microscopy (TEM) . Specifically, the sample of metal clusters could be obtained by the way described by J. Am. Chem. Soc, 116, 7401-7402. It is reported that the metal clusters could first be stabilized by an ionic liquid electrolyte in a solvent that has essentially no solubility to material obtained. Metal clusters of different particle size are then precipitated when they are controlled by variation of the current density.

The metal clusters, may have any shape, i.e. they may e.g. be particulate or fibrous. The term “particulate” in this respect is to be understood as referring to particles having a more or less isometric structure like spherical, substantially spherical, ovoidal or substantially ovoidal particles. Such particulate particles usually differ from acicular particles, platy particles as well as fibrous particles in the aspect ratio.

Platy particles are well known by the persons skilled in the art. Typically, platy particles consist essentially of, or even consist of, particles having the shape of, or resembling to a plate, i.e. the particles are flat or substantially flat and their thickness is small in comparison with the other two dimensions.

Acicular particles are also well known by the skilled in the art. Typically, acicular particles have the shape of, or resembling a needle.

In one specific embodiment, the metal clusters having the shape of cuboctahedron.

Method for preparing the metal clusters is not particularly limited. For example, people having ordinary skill in the art could obtain metal clusters by some well-known methods, such as the ways disclosed by M.T. Reetz, W. Helbig, "Size-Selective Synthesis of Nanostructured Transition Metal Clusters" , J. Am. Chem. Soc. (1994) , 116, pp. 7401-7402； M.L. Rodriguez-Sanchez, M.J. Rodriguez, M.C. Blanco, J. Rivas, M.A. Lopez-Quintela, "Kinetics and mechanism of the formation of Ag nanoparticles by electrochemical techniques: a plasmon and cluster time-resolved spectroscopic study" , The journal of physical chemistry. B (2005) , 109, pp. 1183-1191； J.D. Aiken, R.G. Finke, "A review of modern transition-metal nanoclusters: their synthesis, characterization, and applications in catalysis" , J. Mol. Catal. A: Chem. (1999) , 145, pp. 1-44； S. Huseyinova, J. Blanco, F.G. Requejo, J.M. Ramallo-López, M.C. Blanco, D. Buceta, M.A. López-Quintela, "Synthesis of Highly Stable Surfactant-free Cu5Clusters in Water" , J. Phys. Chem. C (2016) , 120 (29) pp. 15902-15908； US2009035852A1and so on.

In one preferred embodiment, metal salt may be reduced to metal clusters in situ while the reactants of invented process are present. In this regard, the concentration of metal salt in the solvent may be preferably comprised from 0.00001 to 1mol/L and more preferably from 0.0001 to 0.01mol/L.

In another preferred embodiment, metal clusters could also be produced in situ by an electrode directly. For example, the active catalyst was produced by oxidizing electrode comprises metal element at a positive potential in order to produce metal ions in the solution. Then the metal ions were reduced to metal clusters at a negative potential.

The molar ratio of first reactant to catalyst of present invention may be comprised from 0.001 to 10 and preferably from 0.01 to 1.

The solvent of present invention is used to dissolve electrolyte and at least partially dissolve the first reactant. Any suitable solvent, such as water and organic solvent could be used.

Examples of organic solvent, such as methanol, ethanol, propanol, acetone, acetonitrile, acetic acid, THF (tetrahydrofuran) , DMF (N, N-dimethylformamide) , DMSO (dimethylsulfoxide) , NMP (N-Methyl-2-pyrrolidone) , DMC (dimethyl carbonate) , NM (nitromethane) , PC (propylene carbonate) , EC (ethylene carbonate) and ionic liquids. Said ionic liquid may be alkylammonium salt such as tetraalkylammonium halides, tetraalkylammonium perchlorates, tetraalkylammonium tetrafluoroborates.

It should be understood that the solvent mentioned above could be used independently or in the form of mixtures.

In present invention, the electrolyte may be organic or inorganic compounds. Inorganic compounds are preferably alkali metal salt or alkaline earth metal salt. Organic compounds could be ionic liquids, especially alkylammonium salt such as tetraalkylammonium halides, tetraalkylammonium perchlorates, tetraalkylammonium tetrafluoroborates.

Examples of inorganic compounds used as electrolyte notably are:

‐ Halides, such as lithium chloride, sodium chloride, potassium chloride, lithium bromide, sodium bromide and potassium bromide, magnesium chloride, magnesium bromide.

‐ Nitrates, such as lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate.

‐ Perchlorates, such as lithium perchlorate, sodium perchlorate, potassium perchlorate, magnesium perchlorate.

Examples of organic compounds used as electrolyte notably are:

‐ Tetraalkylammonium halides, such as tetrabutyl ammonium bromide, tetrabutyl ammonium chloride, tetraoctyl ammonium bromide, tetraoctyl ammonium chloride.

The concentration of electrolyte in solvent may comprise preferably from 0.01wt％to 50 wt％and more preferably from 0.1 wt％to 5 wt％.

The invented process can further employ a stabilizer to metal clusters. It is understood that the stabilization can be accomplished in two precedented ways: electrostatic stabilization and steric stabilization.

Electrostatic stabilization occurs by the adsorption of ions to the often electrophilic metal surface. This adsorption creates an electrical double layer, which results in Coulombic repulsion force between individual particles.

Steric stabilization is achieved by surrounding the metal center by layers of material that are sterically bulky, such as polymers or surfactants. These large adsorbates provide a steric barrier which prevents close contact of the metal particle centers

The stabilizer of this invention is not particularly limited. Any stabilizer which can realize two precedented ways above mentioned can be used. It could notably be solvent or electrolyte molecules as mentioned above. In a specific embodiment, first reactant could be used as stabilizer.

Preferably, the stabilizer could be chosen in the group consisting of THF (tetrahydrofuran) , DMF (N, N-dimethylformamide) , THT (tetrahydrothiophene) , alkylammonium salts such as tetraalkylammonium halides, tetraalkylammonium perchlorates, tetraalkylammonium tetrafluoroborate.

In one embodiment, the reaction may be carried out in the presence of an inert atmosphere such as N₂, Ar. Those atmospheres may be introduced to the reaction medium solely or in a form of mixture with carbon dioxide.

The gas pressure of present invention may be comprised between 10 bars and 200 bars and preferably between 20 bars and 50 bars.

The electrochemical reactor of present invention is not particularly limited. It should be understood by the people having ordinary skill in the art that conventional electrochemical reactor, which comprises at least one compartment, gas assemblies, anode-cathode assemblies could be used.

In one embodiment, the reactor may be preferably a single compartment stainless steel reactor that allows running high pressure electrochemical synthesis under inert conditions.

Anode or cathode of present invention may comprise non-metal element, such as carbon in form of graphite, glassy carbon.

Anode or cathode of present invention may notably comprise at least one metal element in elemental form and/or at least one metal compound of at least one metal element, wherein the metal element is chosen in the group consisting of (i) elements of group IA, IIA, IIIA, IVA, VA, VIA and VIIA of the Periodic Table, (ii) elements of groups IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB of the Periodic Table, (iii) Lanthanides, and (iv) any combination thereof.

In one embodiment, anode or cathode may comprise one and only one metal element in elemental form.

In another embodiment, anode or cathode may comprise a mixture comprising at least two metal elements in elemental form.

In still another embodiment, anode or cathode may comprise a metal alloy comprising at least two metal elements in elemental form.

The metal compound comprised in anode or cathode may notably be metal oxides.

Preferably, cathode may comprise at least one element chosen in the group consisting of C, Fe Ag, Ni, Ru, Ir, Os, Mn, La, Co, Ce and any combination thereof. In a specific embodiment, the cathode may comprise stainless steel.

Preferably, anode may comprise at least one element chosen in the group consisting of C, Fe Pd, Pt, Ru, Au, Rh, Ir, Bi, Sn, B and any combination thereof. In some specific embodiments, the anode may comprise graphite or glassy carbon.

Optionally, sacrificing electrode may be used in present invention, which may comprise element chosen in a group consisting of Al, Mg, Be, Zn, Fe, Ti and Pb.

In one embodiment, the electrodes above mentioned could be made with porous substrate structures. The anode substrates may comprise one or more conducting materials prepared in a sheet, foam, grid, cloth or other similar conductive and porous structure. The substrate can be merely physically support the electrode materials above mentioned and transmit electrons, and/or it can be electrochemically active. Anode substrates can include, for example, stainless steel net, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, carbon fibers, and carbon cloth. Preferably, carbon materials and stainless steel are used as an anode substrate. Cathode substrates can include stainless steel, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, metal screens, carbon fibers, and carbon cloth.

In present invention, a separator or an ion-exchange membrane could be placed between anode and cathode. As used herein "separator" should be understood as a layer that provides a physical separation between the anode and the cathode and acts as an electrical insulator between the two conductive electrodes. It has pores big enough for the fuel or electrolyte solution to go through. As used herein, ion-exchange membrane should be understood as a layer transports dissolved ions across a conductive polymeric membrane.

It should be understood by the people having ordinary skill in the art a potentiostat/galvanostat device or any DC regulated power supply could be used to control and measure the parameters, such as potential and current density. Conventional reference electrode, such as saturated calomel electrode, Ag/AgCl electrode, Ag ion electrode, solid Pt electrode should be employed when potentiostat/galvanostat device is used.

The potential of present invention to produce a propiolactone compound may be comprised from -0.0001V to -10V, and preferably from -1 to -3V.

The current density of present invention to produce propiolactone compound may be comprised from -0.01mA/cm² to -10 mA/cm² and preferably from -1 mA/cm² to -5 mA/cm².

The reaction temperature of present invention may be comprised from -20℃ to 100℃ and preferably from 0℃ to 40℃ and more preferably from 10℃and 30℃.

The following examples are included to illustrate embodiments of the invention. Needless to say, the invention is not limited to the described examples.

EXPERIMENTAL PART

Example 1: preparation of Ni catalyst by reducing of NiBr₂

A single compartment high pressure stainless steel reactor was used and equipped with nickel foam cathode, aluminium anode and platinum wire as reference electrode. 66 ml DMF and 14 ml N4444Br solution (0.24 g/ml, total amount ＝ 4 wt％electrolyte solution) were added by syringe and degassed with Ar. Then 0.041 g NiBr₂ and 0.49 g 2, 3-dimethyl-1, 3-butadiene was introduced and the reactor was closed and flushed with Ar. The pressure was increased by adding CO₂ to 20 barg. Once the pressure was stable and the reactor cooled down to 30℃, the electrodes were connected to the potentiostat. Firstly the active catalyst was produced by reducing the nickel salt by electrochemistry. Therefore, a potential of -0.9V with a current density of -2.4 mA/cm² was applied for 3000 s. The so in-situ produced active nickel species were immediately used for propiolactone synthesis. (see EXAMPLE 2)

Example 2: Electrochemical Lactone formation in presence of Nickel clusters prepared from nickel salts

After the catalyst synthesis described in EXAMPLE 1 the propiolactone synthesis was followed directly by applying a potential of -2V at a current density of -2.3 mA/cm² for 95 hs. After synthesis, DMF was removed under vacuum. The residue was acidified with 2M HCl for 6 hs and the product was extracted with dimethyl ether and dried over Na₂SO₄. After isolation of the products by removing diethylether (propiolactone and hex-3-enedioic acid) , ¹H and ¹³C NMR in DMSO were performed to validate the products.

Results:

Example 3 preparation of Ni catalyst by sacrificing the electrode and followed reduction

In another experiment, the active clusters were not formed by adding a metal salt but rather by the electrode itself. The same reactor and setup was used as described in example 1. The nickel cluster formation was carried out as follows: 67 ml DMF and 13 ml N4444Br solution (0.27 g/ml, total amount ＝ 4 wt％electrolyte solution) were added by syringe and degassed with Ar. Then 0.46 g 2, 3-dimethyl-1, 3-butadiene was introduced and the reactor was closed and flushed with Ar. The pressure was increased by adding CO₂ to 18 barg. Once the pressure was stable and the reactor cooled down to 30℃, the electrodes were connected to the potentiostat. Firstly the active catalyst was produced by oxidizing the nickel electrode for about one hour at a potential range of +1V and +1.5V in order to produce Ni ions in the solution. Then the nickel ions were reduced by electrochemistry for 2000s. A potential of -1.2V with a current density of -2.4 mA/cm² was applied.

Example 4: Electrochemical Lactone formation in presence of nickel clusters prepared by Ni electrode

After the in situ nickel catalyst synthesis described in EXAMPLE 3 the propiolactone synthesis was followed directly by applying a potential range of -0.9V and -1.5V at a current density of -2.15 mA/cm² for about 90 hs. The workup followed the procedure described in EXAMPLE 2

Results:

Comparative Example 1: Electrochemical CO₂ coupling with 2, 3-dimethyl-1, 3-butadiene in absence of catalyst

In another example the electrochemical reaction was carried out similar to EXAMPLE 2 but without previous metal catalyst synthesis. Here the single compartment high pressure stainless steel reactor was equipped with nickel foam cathode, aluminium anode and platinum wire as reference electrode. 67 ml DMF and 13 ml N4444Br solution (0.26 g/ml, total amount ＝ 4 wt％electrolyte solution) were added by syringe and degassed with Ar. Then 0.52 g 2, 3-dimethyl-1, 3-butadiene was introduced and the reactor was closed and flushed with Ar. The pressure was increased by adding CO₂ to 30 barg. Once the pressure is stable and the reactor cooled down to 30℃, the electrodes were connected to the potentiostat. For the coupling reaction a potential range between -0.75V and -1.6V was applied resulting in a current density range of -5 to -8 mA/cm² for 45hs. In this example no lactone but only the hex-3-enedioic acid was formed.

Results:

Comparative Example 2: First catalyst synthesis followed by stirring with absence of electrochemistry

In another example the nickel catalyst was firstly produced as described in EXAMPLE 1 followed by stirring the reaction solution for 96hs. Here the reactor was equipped with a nickel foam cathode, an aluminium anode and a platinum wire as reference electrode. 67 ml DMF and 13 ml N4444Br solution (0.26 g/ml, total amount ＝ 4 wt％electrolyte solution) were added by syringe and degassed with Ar. Then 0.077 g NiBr₂ is introduced and the reactor closed and flushed with Ar. the electrodes were connected to the potentiostat. Firstly the active catalyst was produced by reducing the nickel salt by electrochemistry. Therefore, a potential of -1.7V with a current density of -1.2 mA/cm² was applied for 3600 s. Then 0.43 g 2, 3-dimethyl-1, 3-butadiene was added and the pressure was increased by adding CO₂ to 30 barg. The reactor was stirred without electrochemistry for 66 hs. After work-up as described in EXAMPLE 2 no product was observed.

Results:

Example 5: Use of Iron as active catalyst

In this example an iron salt was used as catalyst precursor. Here the single compartment high pressure stainless steel reactor was equipped with nickel foam cathode, aluminium anode and platinum wire as reference electrode. 66 ml DMF and 14 ml N4444Br solution (0.24 g/ml, total amount ＝ 4 wt％electrolyte solution) was added by syringe and degassed with Ar. Then 0.083 g FeBr₃ and 0.43 g 2, 3-dimethyl-1, 3-butadiene were introduced and the reactor was closed and flushed with Ar. The pressure was increased by adding CO₂ to 25 barg. Once the pressure was stable and the reactor cooled down to 20℃, the electrodes were connected to the potentiostat. Firstly the active catalyst was produced by reducing the iron salt by electrochemistry. Therefore, a potential range between -1.2V and -1.45V and a current density of -2.4 mA/cm² were applied for 3000 s. The so in-situ produced active iron species were immediately used for propiolactone synthesis.

The propiolactone synthesis was followed directly by applying a potential range between -2.5V and -1.9V at a current density of -2.6 mA/cm² for 74 hs. The work-up followed as described in EXAMPLE 2. Only propiolactone was formed.

Results:

Example 6: Changing to new electrodes after cluster synthesis

In this example the active nickel catalyst was firstly produced by electrochemical reduction of NiBr₂ as described in EXAMPLE 1. Then the reactor was pened and as well as the nickel cathode as the aluminium anode exchanged with new electrodes. Then the reactor was closed and the propiolactone synthesis carried out as described in EXAMPLE 2. The reactor was filled with 66 ml DMF, 14 ml N4444Br solution (0.24 g/ml) , 0.031g NiBr₂ and 0.48 g 2, 3-dimethyl-1, 3-butadiene. After flushing with Argon the pressure was increased to 25 barg CO₂. After exchanging the electrodes, the reactor was again filled with 25barg CO₂. Only propiolactone was formed.

Results:

Claims

An electrochemical process for producing a propiolactone compound comprising reacting:

‐ a first reactant being a compound having at least one ethylenically unsaturated carbon-carbon double bond, with

‐ a second reactant being carbon dioxide,

in the presence of an electrolyte, a solvent and a catalyst, wherein the catalyst comprises metal clusters comprising at least one metal element in elemental form, wherein the metal element is chosen in the group consisting of (i) elements of group IA, IIA, IIIA, IVA, VA, VIA and VIIA of the Periodic Table, (ii) elements of groups IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB of the Periodic Table, (iii) lanthanides, (iv) actinides, and (v) any combination thereof.
The process according to claim 1, wherein the first reactant is a compound of formula (I) and the propiolactone compound produced is a compound of formula (II) or formula (III) :

wherein R¹, R², R³ and R⁴ are each independently selected from hydrogen or C_1-11 hydrocarbyl.
The process according to claim 1 or 2, wherein R¹, R², R³ and R⁴ are each independently selected from hydrogen, C_1-6 alkyl, C_2-6 alkenyl or phenyl.
The process according to any one of claims 1 to 3, wherein at least one of R¹, R², R³ and R⁴ of formula (I) is linear C_1-4 alkyl.
The process according to claim 2, wherein the first reactant is a compound of formula (IV) and the propiolactone compound produced is a compound of formula (V) or formula (VI) :

wherein R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each independently selected from hydrogen or C_1-11 hydrocarbyl.
The process according to claim 5, wherein at least one of R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ of formula (IV) is linear C_1-4 alkyl.
The process according to any one of claims 1 to 6, wherein first reactant is chosen in the group consisting of 1, 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, isoprene, myrcene, styrene, alpha-methylstyrene and 1-pheny-l, 3-butadiene.
The process according to any one of claims 1 to 7, wherein propiolactone compound produced is chosen in the group consisting of 3-methyl-3- (prop-1-en-2-yl) oxetan-2-one, 3- (4-methylpent-3-1-yl) -3-vinyloxetan-2-one, 3- (6-methylhepta-1, 5-dien-2-yl) oxetan-2-one, 3, 3-dimethyl-4- (3-methylenepent-4-en-1-yl) oxetan-2-one, 3-vinyloxetan-2-one, 3-methyl-3-vinyloxetan-2-one, 3- (prop-1-en-2-yl) oxetan-2-one, 3-methyl-3-phenyloxetan-2-one, 3-styryloxetan-2- one and 4-phenyl-3-vinyloxetan-2-one.
The process according to any one of claims 1 to 8, wherein the catalyst comprises metal clusters comprising at least one metal element in elemental form, wherein the metal element is chosen in the group consisting of nickel, cobalt, tin, iron, aluminum, chromium, platinum, palladium, rhodium, ruthenium, iridium, silver, gold, cerium, bismuth, manganese, rhenium and copper.
The process according to any one of claims 1 to 9, wherein the average particle diameter of metal clusters is comprised from 1.5nm to 3nm.
The process according to any one of claims 1 to 10, wherein the solvent is chosen in the group consisting of water, methanol, ethanol, propanol, acetone, acetonitrile, acetic acid, THF (tetrahydrofuran) , DMF (N, N-dimethylformamide) , DMSO (dimethylsulfoxide) , NMP (N-Methyl-2-pyrrolidone) , DMC (dimethyl carbonate) , NM (nitromethane) , PC (propylene carbonate) , EC (ethylene carbonate) , tetraalkylammonium halides, tetraalkylammonium perchlorates and tetraalkylammonium tetrafluoroborates.
The process according to any one of claims 1 to 11, wherein the electrolyte is chosen in the group consisting of alkali metal salt, alkaline earth metal salt and alkylammonium salt.
The process according to any one of claims 1 to 12, wherein a stabilizer chosen in the group consisting of THF (tetrahydrofuran) , DMF (N, N-dimethylformamide) , THT (tetrahydrothiophene) , alkylammonium salts such as tetraalkylammonium halides, tetraalkylammonium perchlorates, tetraalkylammonium tetrafluoroborate is further employed.
The process according to any one of claims 1 to 13, wherein the cathode of electrochemical reactor comprises at least one element chosen in the group consisting of C, Fe Ag, Ni, Ru, Ir, Os, Mn, La, Co, Ce and any combination thereof.
The process according to any one of claims 1 to 14, wherein the anode of electrochemical reactor comprises at least one element chosen in the group consisting of C, Fe Pd, Pt, Ru, Au, Rh, Ir, Bi, Sn, B and any combination thereof.
The process according to any one of claims 1 to 15, wherein the potential to produce propiolactone compound is comprised from -1 to -3V.
The process according to any one of claims 1 to 16, wherein the current density to produce propiolactone compound is comprised from -1 mA/cm² to -5 mA/cm².