Process for the preparation of vinyl ethers

Abstract

The present invention relates to a process for the preparation of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine comprising a primary, a secondary, or a primary and a secondary amino group. It further relates to a process comprising the recovery of the amine and its optional re-use, as well as a process to obtain a product P comprising the step of converting a vinyl ether prepared according to the present invention or a chemical material originating from a vinyl ether prepared according to the present invention.

Description

Process for the preparation of vinyl ethersThe present invention relates to a process for the preparation of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine comprising a primary, a secondary, or a primary and a secondary amino group. It further relates to a process comprising the recovery of the amine and its optional re-use, as well as a process comprising the step of converting a vinyl ether prepared according to the present invention or a chemical material originating from a vinyl ether prepared according to the present invention.Vinyl ethers present an important substance class for different application fields. They are used as monomers for polymers and copolymers, which themselves find application in industrial applications like conventional or radiation-curable coatings, adhesives, and printing inks. Furthermore, vinyl ethers can be utilized as building blocks for the preparation of chemical intermediates, odorants, flavors, and pharmaceutical products.J. Cuthbertson et. al., Tetrahedron 71 (2015) 4385-4392 describes the addition of alkoxides to terminal alkynes in DMF as solvent. The process is limited to terminal aromatic alkynes and the structure of the arene moiety is decisive for the reaction outcome. The aryl alkynes are solid or liquid, consequently, the reaction is carried out at standard pressure. Yields of enol ethers lay between 0% and at maximum 72%.US2003 / 0105354 A1 discloses a continuous process for the preparation of O-, S-, and N-alkenyl compounds by reaction of the corresponding OH, SH, or NH compound with acetylene in the presence of basic alkali or alkaline earth metal compounds. In the examples, as alcohol, only cyclohexanol was converted at 2 MPa and 159 °C with a productivity rate of 0.1 to 0.11 kg vinyl cyclohexyl ether per litre of reaction volume per hour.EP 2436665 A1 discloses the vinylation of tertiary alcohols by reacting acetylene and a tertiary alcohol in the presence of a base and a cyclic urea or glyme or a mixture thereof as solvent. The reaction is carried out at around 1.8 bar and 120-180 °C. In example 6, 1-adamantanol is vinylated under atmospheric pressure, however, the reaction needed to be carried out for 62 h. Considering the substances present in the reaction mixture, which correspond to a reaction volume of 0.7 L and the resulting product amount of 285 g, this results in a space-time-yield of 6.6 g / hL During this reaction, post addition of catalyst was required.CN 102260144 A discloses the vinylation of tert-butanol with acetylene in the presence of sodium hydroxide as catalyst and lithium diisopropylamide as a co-catalyst. The reaction is performed in a two-step process using 1 ,3-dimethyl-2-imidazolidinone, i.e., a urea derivative, as solvent. The vinylation step is carried out at normal pressure at 60-65 °C.CN 101555198 A describes a method for the production of isobutyl vinyl ether from isobutanol and acetylene in the presence of an alkali metal alkoxide as catalyst and a mixture of aromatic amines and sulfones as auxiliary agent at 120-200 °C and 0.4-0.8 MPa (4-8 bar). As aromatic amines, dimethylaniline and diethylaniline, and as sulfone, dimethyl sulfoxide, is stated. It should be noted, that, at least in the English translation, dimethyl sulfoxide is stated as sulfone, whereas, chemically, dimethyl sulfoxide does not represent a sulfone. In the examples, the vinylation of isobutanol in the presence of sodium alkoxide and dimethylaniline as the sole auxiliary agent is described.US 2404700 A describes a process for the production of vinyl ethers from acetylene and alcohols in the presence of a secondary or tertiary aromatic amine as high boiling solvent containing the potassium alkoxide of the corresponding alcohol at 150-200 °C and ordinary pressure. Considering the data given in the examples 1 and 2, an average space-time-yield of around 50 g / Lh can be calculated, resulting from ca. 1.2 L reaction volume (calculated from the stated reactants), 849 g product and 13 h reaction time (example 1), or 2 L reaction volume and 94 g / h production rate (example 2), respectively.D. Steinborn et. al., J. Organomet. Chem. 1991, 414, C45-50 describes the co-catalytic effect of Lewis-bases on the sodium methoxide catalyzed formation of methyl vinyl ether. Among other donors, as amine, only the tertiary amine N,N,N’,N’-tetramethylethylenediamine (TMEDA) is used at a reaction temperature of 70 °C. The catalyst concentration is stated as 0.2 mol KOMe / mol MeOH, which corresponds to 5 mol / L. The highest conversion rate, when using TMEDA at 1 mol per 1 mol KOMe is given as ca. 35 ml acetylene per mol KOMe per hour corresponding to ca. 1.6 mmol which leads to 1.6 mmol or ca. 90 mg of methyl vinyl ether. I.e., per mol KOMe corresponding to a volume of 0.2 L and per hour, 90 mg of methyl vinyl ether are formed and thus, per liter and hour 450 mg of methyl vinyl ether are formed, corresponding to a space-time-yield of ca. 0,45 g / Lh.Beside lower commercial availability and high costs, aromatic amines, i.e., amines comprising an amino group directly bound to an aromatic carbon atom, are frequently classified as toxic and / or CMR substances. Furthermore, the stability of dimethyl sulfoxide due to deprotonation cannot be ensured under strongly basic reaction conditions over a longer period of time (D. Steinborn et. al., J. Organomet. Chem. 1991 , 414, C45-50), and the usage of dimethylsulfoxide, particularly in combination with strong bases bears safety issues, like potential explosion hazards due to autocatalytic thermal decomposition (Q. Yang et. al., Org. Process Res. Dev. 2020, 24, 916-939). Superstrong bases like lithium diisopropylamide are difficult to handle, e.g., due to violent reaction with water, and require special safety measures, e.g., handling under inert gas.In general, there is a demand to use reaction components with a less problematic toxicological profile, easier handling, higher commercial availability and more attractive costs.Due to the higher risks when working under high pressure, especially for reactions utilizing acetylene, a further general demand is it to provide processes which do not require high pressures but can be performed at low overpressure or even normal pressure. Such processes are connected with lower safety issues compared to high-pressure processes and require generally a lower invest both in reactor as well as safety infrastructure, which makes them economically more attractive.To enable industrial applicability, furthermore, space-time-yields as high as possible in combination with as high as possible ratios of the desired product in the raw product mixture, i.e. , a high raw product purity, are needed.It was an object of the present invention to find an efficient, more sustainable, cost-effective and safe process to produce vinyl ethers from alcohols and acetylene. Further components in the process should be of a toxicological concern as low as possible.The process should be performable at atmospheric pressure, thus lowering safety risk issues and costs for reactor infrastructure. Also under atmospheric pressure, the process should lead to high space-time-yields in combination with high vinyl ether contents in the raw product mixture, i.e., a high raw product purity. The high raw product purity should be maintained also under increased alcohol dosage, i.e., at higher conversion rates. The raw product quality should be in a range allowing for a reduced need for or a redundancy of further purification, thus leading to reduced costs regarding infrastructure and energy.We have surprisingly found that the above mentioned object can be achieved by a process for the preparation of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine, wherein the amine comprises a primary, a secondary, or a primary and a secondary amino group.According to the inventive process, vinyl ethers can be synthesized starting from alcohols, acetylene, a basic catalyst precursor, and an amine which comprises a primary of a secondary amino group.Vinyl ethersVinyl ethers, also referred to as alkenyl ethers, are substances of the following general formula (I):R-O-CH=CH2(I).Preferably, R in formula (I) represents an organic group with 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, particularly preferably 1 to 10 carbon atoms, very particularly preferably 1 to 8 carbon atoms, and most preferably 2 to 6 carbon atoms. Preferably, R does not comprise hydroxy groups. The organic group may comprise other atoms than carbon and hydrogen atoms in form of functional groups that are not reactive with acetylene. For example, the organic group may comprise oxygen atoms in form of ether groups, including but not limited to vinyl ether groups, or nitrogen atoms in form of amino groups, thus, R can for example be substituted or unsubstituted 2-amino-alk-1-yl, 3-amino-alk-1-yl, or 4-amino-alk-1-yl. In the case, the organic group comprises one or more vinyl ether groups, the vinyl ether of formula (I) is a divinyl ether or a polyvinyl ether, respectively.More preferably, R in formula (I) represents a hydrocarbon group and does not comprise other atoms than carbon or hydrogen atoms.Particularly preferably, R in formula (I) represents a non-aromatic hydrocarbon group. Such hydrocarbon group may be an alkyl group or a cycloalkyl group optionally comprising olefinic or acetylenic units.Very particularly preferably, R in formula (I) represents a non-aromatic hydrocarbon group, which may be an alkyl group or a cycloalkyl group.Vinyl ethers of formula (I) may, for example, be methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, but-2-yl vinyl ether (sec-butyl vinyl ether), 2-methylprop-1-yl vinyl ether (isobutyl vinyl ether), tert-butyl vinyl ether, pent-1-yl vinyl ether2-methylbut-1-yl vinyl ether, 3-methylbut-1-yl vinyl ether, 2,2-dimethylprop-1-yl vinyl ether, pent-2-yl vinyl ether, 3-methylbut-2-yl vinyl ether, pent-3-yl vinyl ether, 2-methylbut-2-yl vinyl ether, hex-1-yl vinyl ether, hex-2-yl vinyl ether, hex-3-yl vinyl ether, 2-methylpent-1-yl vinyl ether,3-methylpent-1-yl vinyl ether, 4-methylpent-1-yl vinyl ether, 2-methylpent-2-yl vinyl ether, 3-methylpent-2-yl vinyl ether, 4-methylpent-2-yl vinyl ether, 2-methylpent-3-yl vinyl ether, 3-methylpent-3-yl vinyl ether, 2,2-dimethylbut-1-yl vinyl ether, 2,3-dimethylbut-1-yl vinyl ether, 3,3-dimethylbut-1-yl vinyl ether, 2,3-dimethylbut-2-yl vinyl ether, 3,3-dimethylbut-2-yl vinyl ether,2-ethylbut-1-yl vinyl ether, hept-1-yl vinyl ether, hept-2-yl vinyl ether, hept-3-yl vinyl ether,3-ethylpent-3-yl vinyl ether, oct-1-yl vinyl ether, oct-2-yl vinyl ether, 2-ethylhexyl vinyl ether, non-1-yl vinyl ether, non-2-yl vinyl ether, dec-1 -yl vinyl ether, undec-1-yl vinyl ether, lauryl vinyl ether (dodec-1-yl vinyl ether), tridecyl vinyl ether, myristyl vinyl ether (tetradec- 1-yl vinyl ether),pentadec-1-yl vinyl ether, cetyl vinyl ether (hexadec-1-yl vinyl ether), heptadec-1-yl vinyl ether, stearyl vinyl ether (octadec-1-yl vinyl ether), oleyl vinyl ether (cis-9-octadecen-1-yl vinyl ether), cis,cis-cis-9,12,15-octadecatrien-1-yl vinyl ether, eicosanyl vinyl ether, cyclopropyl vinyl ether, cyclopropylmethyl vinyl ether, cyclopropylethyl vinyl ether, cyclobutyl vinyl ether, cyclobutylmethyl vinyl ether, cyclobutylethyl vinyl ether, cyclopentyl vinyl ether, cyclopentylmethyl vinyl ether, cyclopentylethyl vinyl ether, 1-methyl-cyclopentyl vinyl ether, 2-methyl-cyclopentyl vinyl ether, 3-methyl-cyclopentyl vinylether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, cyclohexylethyl vinyl ether, 1-methyl-cyclohexyl vinyl ether,2-methyl-cyclohexyl vinyl ether, 3-methyl-cyclohexyl vinyl ether, 4-methyl-cyclohexyl vinyl ether, cycloheptyl vinyl ether, cyclooctyl vinyl ether, cyclononyl vinyl ether, cyclodecyl vinyl ether, benzyl vinyl ether, diphenylmethyl vinyl ether, 1-phenyl-ethyl vinyl ether, 2-phenyl-ethyl vinyl ether, 2,2-diphenyl-ethyl vinyl ether, 2,2,2-triphenyl-ethyl vinyl ether, alkenyl vinyl ethers, like3-methylbut-3-enyl vinyl ether, cis-2-hexen-1-yl vinyl ether, trans-2-hexen-1-yl vinyl ether, cis- 3-hexenyl vinyl ether, 1-octen-3-yl vinyl ether, 2-octen-1-yl vinyl ether, 3-octen-1-yl vinyl ether, 3,7-dimethyloct-6-en-1-yl vinyl ether, 3-methyl-3-buten-1-yl vinyl ether, 3,7-dimethxyl-7-octen-1-yl vinyl ether, 10-undecen-1-yl vinyl ether, aminoalkyl vinyl ethers, like 2-aminoeth-1-yl vinyl ether, 3-aminoprop-1-yl vinyl ether, 3-aminoprop-2-yl vinyl ether, 5-aminopent-1-yl vinyl ether,2-(2-aminoethoxy)ethyl vinyl ether, N-(2-aminoethyl)ethyl vinyl ether, N-(3-aminopropyl)ethyl vinyl ether, N-methyl-2-aminoethyl vinyl ether, N-ethyl-2-aminoethyl vinyl ether, N,N-dimethyl- 2-aminoethyl vinyl ether, N,N-diethyl-2-aminoethyl vinyl ether, N,N-dimethyl-3-aminoprop-1-yl vinyl ether, N,N-dibutyl-2-aminoethyl vinyl ether, N,N-dimethyl-3-aminopropyl vinyl ether, alkoxy alkyl vinyl ethers like 2-methoxyethyl vinyl ether, 2-ethoxyethyl vinyl ether, 2-propoxyethyl vinyl ether, 2-isopropoxyethyl vinyl ether, 2-butoxyethyl vinyl ether, 2-hexyloxyethyl vinyl ether, 2-phenoxyethyl vinyl ether, 2-(2-methoxyethoxy)ethyl vinyl ether, 2-(2-ethoxyethoxy)ethyl vinyl ether, 2-(2-butoxyethoxy)ethyl vinyl ether, 1-methoxyprop-2-yl vinyl ether, ethoxypropyl vinyl ether, 1-butoxy-prop-2-yl vinyl ether, 1-hexoxyprop-2-yl vinyl ether, methoxypropoxypropyl vinyl ether, butoxypropoxypropyl vinyl ether, hexoxypropoxypropyl vinyl ether, other vinyl ethers like menthyl vinyl ether or borneyl vinyl ether, or divinyl ethers, like 1 ,3-propanediol divinylether,1.4-butanediol divinylether, 2,3-butanediol divinylether, neopentylglycol divinylether,1.5-pentanediol divinylether, 1 ,6-hexanediol divinyl ether, 2,5-dimethyl-2,5-hexanediol divinyl ether, or poly(ethylene glycol) divinyl ether.AlcoholsSuitable alcohols for the process for the preparation of vinyl ethers are alcohols of formula (II) R-OH (II), wherein R corresponds to R in formula (I) and has the same meaning as in formula (I).Preferably, the alcohol of formula (II) comprises 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, particularly preferably 1 to 10 carbon atoms, very particularly preferably 1 to 8 carbon atoms, and most preferably 2 to 6 carbon atoms, and an OH-group bound to an aliphatic saturated carbon atom.The alcohols can also be monovinylated diols, comprising already one vinylether group and a free OH-group. If these types of alcohols are used, the inventive process leads to divinyl ethers. Also polyvinylated polyalcohols comprising a free OH-group can be used, leading to polyvinyl ethers.Alcohols of formula (II) may, for example, be methanol, ethanol, propanol, isopropanol, butanol, butan-2-ol (sec-butanol), 2-methylpropan-1-ol (isobutanol), tert-butanol, pentan-1-ol,2-methylbutan-1-ol, 3-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, pentan-2-ol,3-methylbutan-2-ol, pentan-3-ol, 2-methylbutan-2-ol, hexan-1-ol, hexan-2-ol, hexan-3-ol,2-methylpentan-1-ol, 3-methylpentan-1-ol, 4-methylpentan-1-ol, 2-methylpentan-2-ol,3-methylpentan-2-ol, 4-methylpentan-2-ol, 2-methylpentan-3-ol, 3-methylpentan-3-ol,2.2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 2,3-dimethylbutan-2-ol,3.3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, heptan-1-ol, heptan-2-ol, heptan-3-ol, 3-ethylpentan-3-ol, octan-1-ol, octan-2-ol, 2-ethylhexanol, nonan-1-ol, nonan-2-ol, decan-1-ol, undecan-1-ol, lauryl alcohol (dodecan-1-ol), tridecanol, myristyl alcohol (tetradecan- 1-ol), pentadecan-1-ol, cetyl alcohol (hexadecan-1-ol), heptadecan-1 -ol, stearyl alcohol (octadecan- 1-ol), oleyl alcohol (cis-9-octadecen-1-ol), cis,cis,cis-9,12,15-octadecatrien-1-ol, eicosan-1-ol, cyclopropanol, cyclopropylmethanol, cyclopropylethanol, cyclobutanol, cyclobutylmethanol, cyclobutylethanol, cyclopentanol, cyclopentylmethanol, cyclopentylethanol, 1-methyl-cyclopentanol, 2-methyl-cyclopentanol, 3-methyl-cyclopentanol, cyclohexanol, cyclohexylmethanol, cyclohexylethanol, 1-methyl-cyclohexanol, 2-methyl-cyclohexanol, 3-methyl-cyclohexanol, 4-methylcyclohexanol, cycloheptanol, cyclooctanol, cyclononanol, cyclodecanol, benzylalcohol, diphenylmethanol, 1 -phenylethanol, 2-phenylethanol, 2,2-diphenylethanol, 2,2,2-triphenylethanol, alkenols like 3-methylbut-3-enol, cis-2-hexen-1-ol, trans-2-hexen-1-ol, cis-3-hexenol, 1-octen-3-ol, 2-octen-1-ol, 3-octen-1-ol, 3,7-dimethyloct-6-en-1-ol (citronellol), 3-methyl-3-buten-1-ol (isoprenol), 3,7-dimethxyl-7-octen-1-ol (rhodinol), 10-undecen-1-ol, aminoalkanols, like 2-aminoethan-1-ol, 3-aminopropan-1-ol, 3-aminopropan-2-ol, 5-aminopentan-1-ol, 2-(2-aminoethoxy)ethanol, N-(2-aminoethyl)ethanol, N-(3-aminopropyl)ethanol, N-methyl-2-aminoethanol, N-ethyl-2-aminoethanol, N,N-dimethyl- 2-aminoethanol, N,N-diethyl-2-aminoethanol, N,N-dimethyl-3-aminopropan-1-ol, N,N-dibutyl- 2-aminoethanol, N,N-dimethyl-3-aminopropanol, alkoxy alkanols like 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, 2-hexyloxyethanol, 2-phenoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol, 1-methoxypropan-2-ol, ethoxypropanol, 1-butoxy-propan-2-ol,1-hexoxypropan-2-ol, methoxypropoxypropanol, butoxypropoxypropanol, hexoxypropoxypropanol, other alcohols like menthol or borneol, or mono-vinylated diols (diol mono vinyl ethers), like 1 ,3-propanediol monovinylether, 1 ,4-butanediol monovinylether, 2,3-butanediol monovinylether, neopentylglycol monovinylether, 1 ,5-pentanediol monovinylether, 1 ,6-hexanediol monovinyl ether, 2,5-dimethyl-2,5-hexanediol monovinyl ether, or poly(ethylene glycol) monovinyl ether.AcetyleneAcetylene, also referred to as ethyne, has the chemical formula C2H2. Acetylene may comprise propyne and propadiene (allene) as impurity, in summary preferably < 15000vol. -ppm, more preferably < 5000vol. -ppm, particularly preferably < 1000vol. -ppm, and most preferably < 500vol. -ppm.Alkali metal salt of the alcoholThe alkali metal salt of the alcohol of formula (II) is the respective alkali metal alkoxide. Preferably, the alkali metal in this salt is sodium or potassium, more preferably potassium. Also mixed salts comprising different alkali metal ions, for example sodium and potassium, can be present.The alkali metal salt of the reacting alcohol of formula (II) can be formed by the reaction of the respective alcohol of formula II with a catalyst precursor.Preferably, the alkali metal salt of the alcohol is formed by the reaction of the alcohol with a catalyst precursor comprising an alkali metal alkoxide or an alkali metal hydroxide or a mixture of both.Catalyst precursorsSuitable catalyst precursors are any chemical species which react with the respective alcohol under formation of the corresponding alkali metal alkoxide.Catalyst precursors can be any alkali metal base which is able to deprotonate the hydroxy group of the corresponding alcohol, either quantitatively or within an equilibrium reaction. Suitable alkali metal bases are, for example, alkali metal hydroxides, alkali metal alkoxides based on alcohols being less acidic than the alcohol of formula (II), for example, alkali metal tert.-butoxides, alkali metal amides of the formula MNR1R2(M representing the alkali metal, R1and R2being independently hydrogen or an alkyl residue, optionally comprising further atoms like, for example, silicium) like, for example, lithium amide, lithium diisopropylamide, lithium hexamethyldisilazide, lithium tetramethylpiperidide, sodium amide, sodiumhexamethyldisilazide, potassium amide, potassium hexamethyldisilazide, alkali metal carbonates, or alkali metal phosphates. Also mixtures of different alkali metal bases can be used.Furthermore, such chemical species can also be alkali metals in metallic form, preferably lithium, sodium, potassium, more preferably sodium and potassium, most preferably potassium. Preferably, alkali metal bases are used as catalyst precursor.More preferably, alkali metal hydroxides or alkali metal alkoxides are used as catalyst precursor.Particularly preferably, potassium hydroxide or potassium metal alkoxides are used as catalyst precursor.Very particularly preferably, potassium hydroxide or potassium tert.-butoxide is used as catalyst precursor.Most preferably, potassium tert.-butoxide is used as catalyst precursor.The formation of the alkali metal salt of the alcohol of formula (II) can be performed either in-situ or in a separate reaction. In case of the in-situ formation of the alkali metal salt, the respective catalyst precursor is provided in the reaction mixture and the alkali metal salt of the alcohol of formula (II) is formed upon addition of the respective alcohol. In case of the formation of the alkali metal salt in a separate reaction, the respective catalyst precursor is reacted with the alcohol of formula (II) and the resulting mixture comprising the alkali metal salt of the alcohol of formula (II) is provided to the reaction mixture.The complete amount of the catalyst precursor or the separately formed mixture comprising the alkali metal salt of the alcohol of formula (II) can be provided to the reaction mixture before the start of the reaction resulting in the vinyl ether; alternatively, only a part of the amount is provided to the reaction mixture at the beginning of the reaction and the residue is post-added during the reaction in which the vinyl ether is formed.Preferably, the complete amount of the catalyst precursor or the separately formed mixture comprising the alkali metal salt of the alcohol of formula (II) is provided to the reaction mixture before the start of the reaction resulting in the vinyl ether.Aliphatic aminesSuitable aliphatic amines are amines comprising a primary, a secondary, or a primary and a secondary amino group.The aliphatic amines can be aliphatic monoamines comprising one primary or one secondary aliphatic amino group, or polyamines.Preferably, the aliphatic amines comprise 1 to 50, more preferably 1 to 20, particularly preferably 1 to 10, very particularly preferably 1 to 6, and most preferably 2 to 4 amino groups selected from the class of primary or secondary amino groups.Optionally, the aliphatic amines can additionally comprise tertiary amino groups. All amino groups are connected to aliphatic carbon atoms, however, the aliphatic amines can optionally comprise aromatic units, as for example, in 3-(2’-phenyl-ethylamino)propylamine. Optionally, single or more amino groups present in the aliphatic amines or polyamines can be part of a cycle, as for example in 4-aminopiperidine.In contrast to aliphatic amines, aromatic amines comprise amino groups directly bound to aromatic carbon atoms.The aliphatic amines can preferably be polyamines comprising at least two amino groups, at least one of which is a primary or a secondary aliphatic amino group.Preferably, the polyamines comprise in each case between two amino groups a unit comprising at least three consecutive carbon atoms, wherein one of these amino groups is bound to a first of these carbon atoms and the other amino group is bound to a second of these carbon atoms and at least one further carbon atom is located between the first and the second of these carbon atoms.Suitable aliphatic monoamines are for example, alkylmonoamines, alkoxyalkylamines, (arylalkyl)monoamines, N,N-dialkylmonoamines, N,N-dicycloalkylmonoamines, N-alkyl- N-cycloalkylmonoamines, wherein the alkyl residues comprise saturated or unsaturated linear or branched or cyclic hydrocarbon units or any combination thereof. The alkyl residues can optionally furthermore comprise aromatic units.N,N-Dialkylmonoamines may, for example, be dibutylamine, dihexylamine, bis(2-ethylhexyl)amine, or ditridecylamine.As aliphatic monoamines preferably hexylamine, cyclohexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, undecylamine, dodecylamine which can be a mixture of different isomers, tridecylamine which can be a mixture of different isomers, tetradecylamine which can be a mixture of different isomers, hexadecylamine which can be a mixture of different isomers, octadecylamine which can be a mixture of different isomers, N,N-dicyclohexylamine, (2-phenylethyl)amine, (2-phenyl-1-metyhlethyl)amine, piperidine, or benzylamine is used.Suitable aliphatic polyamines are for example, alkylenediamines, amino-aza-cycloalkanes, aminoalkyl-aza-cycloalkanes, N-(aminoalkyl)-N-alkylamines, N-(aminoalkyl)-N,N-dialkylamines,N-(aminoalkyl)-N-cycloalkylamines, diaminocycolalkanes, (N-alkylamino)-aminocycloalkanes, (phenylethylamino)alkylamines, dialkylenetriamines, N-substituted dialkylenetriamines comprising further alkyl substituents on one or more or all amino groups provided that at least one primary or secondary aliphatic amino group is present, trialkylenetetramines, N-substituted trialkylenetetramines comprising further alkyl substituents on one or more or all amino groups provided that at least one primary or secondary aliphatic amino group is present, poly(propyleneimines), N-substituted poly(propyleneimines) comprising further alkyl substituents on one or more or all amino groups provided that at least one primary or secondary amino group is present, wherein the alkyl or alkylene units or both comprise saturated or unsaturated linear or branched or cyclic hydrocarbon units or any combination thereof. The alkyl or alkylene units or both can optionally furthermore comprise aromatic units.Alkylenediamines may, for example be, 1 ,3-propanediamine, neopentanediamine, hexamethylenediamine, or octamethylenediamine.Preferably, as aliphatic polyamine, isophorone diamine, 4-aminopiperidine, 2,2,6,6-tetamethyl- 4-aminopiperidine, N-(aminopropyl)-piperidine, N , N-dibutyl- 1 ,3-diaminopropane,2-(diethylamino)ethylamine, 3-(dimethylamino)propylamine, N-N-diethyl- 1 ,3-propanediamine,3-(methylamino)propylamine, 6-(butylamino)-hex-1-ylamine, N-cyclohexyl-1 ,3-diaminopropane, N-aminobutyl-N-cyclohexylamine, N-aminopropyl-N-tert-butylamine, 1 ,2-diaminocyclohexane, N-butyl-1 ,2-diaminocyclohexane, 3-(2’-phenylethylamino)propylamine, 4,4’-diaminodicyclohexylmethane, 3,3’-dimethyl-4,4’-diaminodicyclohexylmethane, N,N‘-bis(3-aminopropyl)-4,4‘-diaminodicyclohexylmethane, 2,2‘-dimethyl- 4,4‘-methylenebis(cyclohexylamine), diethylenetriamine, 3-(2‘-aminoethyl)aminopropylamine, dipropylenetriamine, N,N-dimethyldipropylenetriamine, N,N-bis(3-aminopropyl)methylamine, N,N-bis-(3-aminopropyl)butylamine, N,N‘-bis(3-aminopropyl)ethylenediamine, N1,N3-bis(3-aminopropyl)-N1,N3-dimethyl-1 ,3-propanediamine, tripropylenetetramine (N,N‘-bis(3-aminopropyl) 1,3-propanediamine), N,N‘-bis(3-aminopropyl)neopentanediamine, linear polypropylene imine) or N-methylated linear polypropylene imine) with terminal NH2- groups is used.Most preferably, isophorone diamine, N,N-dibutyl-1,3-diaminopropane, N-cyclohexyl-1.3-diaminopropane, 4,4’-diaminodicyclohexylmethane, 3,3‘-dimethyl- 4,4‘-diaminodicyclohexylmethane, N,N‘-bis(3-aminopropyl)-4,4‘-diaminodicyclohexylmethane, N , N‘-bis(3-aminopropyl)ethylenediamine, N1, N3-bis(3-aminopropyl)-N1, N3-dimethyl-1.3-propanediamine, dipropylenetriamine, N,N-dimethyldipropylenetriamine, N,N-bis(3-aminopropyl)methylamine, tripropylenetetramine (N,N‘-bis(3-aminopropyl)1,3-propanediamine) or linear polypropylene imine) is used.At a standard pressure of 101.3 kPa, the aliphatic amine preferably does not have a boiling point of < 130 °C, more preferably, of < 140 °C, particularly preferably, of < 150 °C, and very particularly preferably, of < 160 °C.The boiling point of the aliphatic amine is especially relevant if the process includes distillative steps, like for example, distillation of the formed vinyl ether and optionally remaining alcohol during or after the reaction. To avoid that the aliphatic amine contaminates the distillate containing the vinyl ether, the amine preferably needs to have a boiling point which lays above the distillation temperature. In a continuous process, where the vinyl ether and remaining alcohol are continuously distillated off the reaction mixture, the distillation temperature corresponds to the reaction temperature.Since the boiling point is pressure-dependent, if the reaction is performed at overpressure, also aliphatic amines showing boiling points below the reaction temperature at standard pressure, i.e. , < 130 °C, 140 °C, 150 °C, or 160 °C, respectively, can be suitable, provided that, at the respective reaction temperature and pressure, they are not distilled off to contaminate the distillate.Amines that do not show a boiling point at all, i.e. neither a boiling point < 130 °C, 140 °C, 150 °C, or 160 °C, respectively, and which, for example, decompose before evaporation, like, for example polypropylene imine), may also be used. Amines, that decompose before evaporation, should not decompose substantially at or below the reaction temperature.Optionally, also mixtures of different amines, different polyamines or amines and polyamines can be used.Ratios of the different componentsPer molar equivalent of alcohol groups present in the alcohol, preferably 0.5 to 20, more preferably 0.5 to 10, particularly preferably 1 to 5, and most preferably 1 to 2 molar equivalents of acetylene are used. A molar ratio of acetylene to alcohol < 1 , can be used if only a partial conversion of the alcohol is desired, and leads to a reduced amount of acetylene in the off-gas.The molar ratio of catalyst precursor equivalents to alcohol equivalents is preferably 0.001 to 0.1, more preferably 0.0025 to 0.05. Each catalyst precursor equivalent reacts with one equivalent of alcohol to the corresponding alkali metal salt.Preferably, the aliphatic amine is used in an amount corresponding to 2 to 100, more preferably to 5 to 75 molar equivalents amino groups per molar equivalent of catalyst.SolventThe process of the present invention can be performed in the presence of a solvent. The amount of solvent is typically 0-97wt.-% based on the reaction mixture.Appropriate solvents, if used, or the amine, if no solvent is used, should dissolve relatively well the substrate alcohol, preferably its alkali metal salts, and, in case of solvent usage, the amine, i.e. , clear solutions should be obtained at concentrations of at least 1 g / L of the respective compound under the reaction conditions. With respect to the alkali metal salt of the alcohol, also solvents, if used, or amines, if no solvent is used, are suitable, that are able to suspend the alkali metal salt of the alcohol at concentrations of at least 1 g / L under the reaction conditions. Optionally but not necessarily, appropriate solvents, if used, or the amine, if no solvent is used, should dissolve acetylene relatively well, however the acetylene solubility is not decisive, since the reaction might also take place at phase interface between acetylene and solvent or amine, respectively. Furthermore solvents should preferably be easily removable from the reaction system, e.g., by distillation, evaporation, or extraction.As optional solvent, any non-protic solvent can be used, which is compatible with the strongly basic amine-containing reaction milieu at an elevated temperature of above 50 °C.As optional solvent, preferably hydrocarbon solvents, including, for example, paraffine oils, i.e., hydrocarbon oils obtained from petroleum, and including hydrocarbon solvent mixtures, like for example kerosene, white spirit, or petroleum ether, alkyl-substituted aromatic solvents, alkoxysubstituted aromatic solvents, ether solvents, including diaryl ether solvents, thioether solvents, tertiary amines comprising no other than tertiary amino groups, urea derivatives not comprising free NH-groups, amides or lactams not comprising free NH-groups, sulfoxides, or phosphine oxides can be used.As optional solvent, more preferably, pentane, hexane, cyclohexane, benzene, heptane, toluene, ortho-xylene, meta-xylene, para-xylene, xylene isomer mixture, mesitylene, ethylbenzene, tetrahydronaphthalene, paraffin oils, i.e., hydrocarbon oils obtained from petroleum, for example, mineral oils, hydrocarbon solvent mixtures, like for example kerosene, white spirit, or petroleum ether, anisole, 1,2-dimethoxybenzene, 1 ,3-dimethoxybenzene, 1 ,4-dimethoxybenzene, 1 ,2,3-trimethoxybenzene, 1 ,2,4-trimethoxybenzene, 1,3,5-trimethoxybenzene, diethylether, tert-butylmethylether, dibutylether, ethylene glycoldimethylether, tri(ethylene glycol)dimethylether, tetrahydrofuran, 1,4-dioxane, diphenylether, diphenylsulfide, thioanisole, triphenylamine, N,N,N’,N’-tetramethylethylenediamine, N,N,N’,N”,N”-pentamethyldipropylenetriamine, tripropylamine, tributylamine, tris(2-ethylhexyl)amine, N-ethyldiisopropylamine, N,N,N’,N’-tetramethyl-1,3-propanediamine, N,N-diethyl-N’,N’-dimethyl-1 ,3-propanediamine, 1 ,3-dimethyl-2-imidazolidinone, N,N’-dimethylpropyleneurea, tetraalkyl ureas,N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, methyl phenyl sulfoxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide or triphenylphosphine oxide can be used.As optional solvent, most preferably, mesitylene, tetrahydronaphthaline, paraffin oils, i.e. , hydrocarbon oils obtained from petroleum, for example, mineral oils, 1 ,2-dimethoxybenzene, 1 ,3-dimethoxybenzene, 1 ,4-dimethoxybenzene, 1 ,2,3-trimethoxybenzene, 1 ,2,4-trimethoxybenzene, 1 ,3,5-trimethoxybenzene, diphenylether, diphenylsulfide, thioanisole or triphenylamine can be used.At a standard pressure of 101.3 kPa, the solvent preferably has a boiling point of > 130 °C, more preferably of > 140 °C, particularly preferably of > 150 °C, and very particularly preferably of > 160 °C.The boiling point of the solvent is especially relevant if the process includes distillative steps, like for example, distillation of the formed vinyl ether and optionally remaining alcohol during or after the reaction. To avoid that the solvent contaminates the distillate containing the vinyl ether, the solvent preferably needs to have a boiling point which lays above the distillation temperature. In a continuous process, where the vinyl ether and remaining alcohol are continuously disti Hated off the reaction mixture, the distillation temperature corresponds to the reaction temperature.Since the boiling point is pressure-dependent, if the reaction is performed at overpressure, also solvents showing boiling points below the reaction temperature at standard pressure, i.e.,< 130 °C, 140 °C, 150 °C, or 160 °C, respectively, can be suitable, provided that, at the respective reaction temperature and pressure, they are not distilled off to contaminate the distillate.Also mixtures of different solvents can be utilized.WaterGenerally, in the process, preferably < 2wt.-% more preferably < 1wt.-%, particularly preferably< 0.5wt.-%, and most preferably < 0.1wt.-% water is present.Inert gasOptionally, inert gases, like nitrogen or noble gases, like helium, neon, or argon, can be present in the inventive process.Reaction conditionsThe reaction is preferably performed at an absolute pressure of 0.01 to 2.5 MPa, more preferably 0.1 to 2.5 MPa, particularly preferably 0.1 to 1.0 MPa, and most preferably of 0.1 to 0.3 MPa.The overall pressure in the process can be controlled by the applied acetylene pressure or by the applied combined partial pressures of acetylene and of an optional inert gas, such as, for example, nitrogen, helium, neon, or argon. The partial acetylene pressure in such a gas mixture is preferably 0.01 to 2.5 MPa, more preferably 0.1 to 2.5 MPa, particularly preferably 0.1 to 1.0 MPa, and most preferably of 0.1 to 0.3 MPa.Preferably, the pressure in the process is controlled by the applied acetylene pressure without the usage of an additional inert gas.The reaction is preferably performed at a temperature of 50 to 250 °C, preferably 100 to 200 °C, particularly preferably 130 to 180 °C and most preferably 150 to 170 °C.Usually, higher reaction pressures in the inventive process allow for lower reaction temperatures, whereas, lower reaction pressures typically require higher reaction temperatures. In one embodiment, the reaction is carried out at reaction pressures of 1.0 to 2.5 MPa and reaction temperatures of 50 to 130 °C.In another embodiment, the reaction is carried out at reaction pressures of 0.1 to 0.3 MPa and reaction temperatures of 130 to 250 °C.ReactorsUseful reactors for the vinylation according to the process of the invention include in principle any apparatus described in the technical literature for gas-liquid reactions. To obtain a high space-time yield, an efficient introduction of acetylene into the liquid phase and intensive mixing of the reaction mixture are important. The reaction of the process of the invention can be carried out in a single reactor or in plural successive reactors, for example a reactor battery. Suitable reactors include stirred-tank reactors, batteries of stirred tanks, flow tubes (preferably with internals), bubble columns, trickled fixed-bed columns, and loop reactors. To ensure its efficient introduction, the acetylene is preferably introduced through the stirrer (in case of a stirred tank or a stirred tank battery) and / or through nozzles.Conduction of the reactionThe inventive process can be performed in any way known to a person skilled in the art, as for example in a batch, semi-batch, or continuous mode.Preferably, the inventive process is performed as a semi-batch or as a continuous process.In both cases, the aliphatic amine, the catalyst precursor, and optionally a solvent are present in the reactor at the beginning of the reaction. From the beginning until the end of the reaction, acetylene and the alcohol of formula (I) are fed continuously to the reactor, whereby the dosingrate is adjusted corresponding to the consumption of alcohol and acetylene, i.e., the product formation.In the semi-batch or batch process, the reaction product, i.e., the formed vinyl ether, remains in the reaction mixture until the end of the reaction, and is isolated therefrom by usual methods known by a person skilled in the art, i.e., for example, distillation or fractional distillation, extraction, crystallization or fractional crystallization, chromatography, etc. For example, distillation or fractional distillation can be performed at reduced, standard, or over pressure. Chromatographical methods can be, for example standard liquid chromatography or high performance liquid chromatography (HPLC). Chromatographical methods, furthermore including gas chromatography, can also be used for analytical purposes to determine the composition of the reaction or product mixture. Also a combination of purification methods can be applied. In one embodiment, the reaction is carried out as a semi-batch process and the formed vinyl ether is isolated from the reaction mixture by distillation.In the continuous process, the reaction product and non-converted alcohol of formula (I) are continuously removed from the reaction mixture. This removal can be performed, for example, by continuous distillation or by continuously or stepwise exchanging the liquid phase, for example, using an overflow or a connected pumping device. Continuously or stepwise exchanging means, that while a part of the liquid phase is continuously or stepwise removed from the reactor, a respective amount of liquid, i.e., substrate alcohol of formula (II), catalyst, catalyst precursor, amine, and / or optionally solvent, is continuously or stepwise added to the reactor. The usability of the different removal methods depends on the reaction pressure. At lower pressures, as for example at 0.01 to 0.3 MPa, distillation is more appropriate, whereas at higher pressures, as for example 0.3 to 2.5 MPa, exchange of the liquid phase is more appropriate. However, in principle, distillation can also be applied at higher pressures and exchange of liquid phase can also be applied at lower pressures. The constant removal of nonconverted alcohol from the reaction mixture ensures that a certain upper concentration level of non-converted alcohol in the reaction mixture is not exceeded. Exceeding certain concentration levels of non-converted alcohols in the reaction mixture may affect catalyst activity and thus conversion and yield.More preferably, the process is performed as a continuous process, wherein in the steady state of this continuous process, the molar ratio of alcohol to catalyst in the reaction mixture is < 10, more preferably < 7, particularly preferably < 5, very particularly preferably < 3, and most preferably < 2.Particularly preferably, the process is performed as a continuous process, wherein the formed vinyl ether and non-converted alcohol of formula (II) are removed continuously from the reaction mixture. Preferably, the formed vinyl ether and non-converted alcohol of formula (II) areremoved continuously from the reaction mixture by distillation or by exchange of the liquid phase, more preferably by distillation.To be removable via distillation, both the formed vinyl ether of formula (I) as well as the alcohol of formula (II) have to show a minimum volatility depending on the reaction temperature and pressure, i.e. a dew point of the higher boiling component selected from alcohol and vinyl ether, which is preferably at least 10 K below the reaction temperature. The dew point is the temperature at which a liquid contained in a gas mixture condenses.In a preferred embodiment, the reaction is carried out in a continuous process, wherein acetylene and alcohol of formula (II) are added continuously to the reaction mixture, and the formed vinyl ether of formula (I) is removed continuously from the reaction mixture by distillation. Dosing rate of alcohol and distillation of vinyl ether ensure that the molar ratio of alcohol to catalyst in the reaction mixture does preferably not exceed 10.Space-time-yield and ratio of the vinyl ether in the raw productThe space-time-yield (STY) with respect to the vinyl ether is given asSTY = (distillate [g / h] x weight-ratio of vinyl ether in distillate) I reaction volume [L],The space-time-yield is one parameter for the activity of a reaction medium of a certain volume, comprising for example a catalyst and further components, like for example, amines, concerning the formation of a desired product, i.e., here, the vinyl ether. A higher space-time-yield corresponds to a higher activity of the reaction medium or catalyst, respectively, to form the desired reaction product.The space-time-yield is dependent on the structure of the alcohol, or the formed vinyl ether, respectively.The space-time-yield alone does not essentially specify the quality of a chemical process. For the activity of a reaction medium, also the ratio of the desired reaction product, i.e., the vinyl ether, in the raw product has to be considered. The raw product can be, for example, the raw vinyl ether of formula (I) after work-up via evaporation, if the process is performed in a semibatch or batch mode, or the mixture of vinyl ether of formula (I) and non-converted alcohol of formula (II) in the distillate, if the process is performed in a continuous mode.The ratio of the desired reaction product in the raw product is dependent on the structure of the alcohol, or the formed vinyl ether, respectively.Overall, the activity of a reaction medium with respect to the formation of a specific vinyl ether is determined by the combination of space-time-yield and ratio of the vinyl ether in the raw product.Generally a combination of a high space-time-yield and a high ratio of the vinyl ether of formula (I) in the raw product of the reaction is desired.The raw product from the process performed in a semi-batch or batch mode, i.e., the raw vinyl ether of formula (I), or in a continuous mode, i.e. the mixture of vinyl ether of formula (I) and non-converted alcohol of formula (II), can be further purified by means known to a person skilled in the art, i.e., for example, by distillation or fractional distillation or evaporation under standard or reduced pressure, extraction, crystallization or fractional crystallization, recrystallization, precipitation, filtration, chromatography, etc. Also a combination of purification methods can be applied. The selection of the methods depend on the volatility of the vinyl ether, its boiling point, solubility, molecular weight, and the required degree of purity. Where appropriate, a prepurification can be performed, e.g., by rotary evaporation or extraction. Re-isolated alcohol of formula (I) can be re-used in the process.Recovery and re-use of the amineWe have furthermore found a process for the recycling and optional re-use of the amine comprising the following steps: a) Synthesis of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine, characterized in that the aliphatic amine comprises a primary, a secondary, or a primary and a secondary amino group, b) Recovery of the amine from the reaction mixture, and c) Optional re-use of the recovered amine in a process for the synthesis of vinyl ethers as described in step a).Step a)Step a) corresponds to the inventive process for the synthesis of vinyl ethers as described above.Step b)After the reaction of step a), the amine can be isolated from the remaining reaction mixture by conventional means known by a person skilled in the art.For example, amines that can be evaporated without decomposition, can be isolated by means of distillative methods, like fractionated distillation under standard or reduced pressure (vacuum distillation). Where an additional solvent is present, amine and solvent can be distilled one after another, starting with the component with the lower boiling point. In this case, also the combination of distillation under standard pressure and vacuum distillation is possible, including also different degrees of vacuum for the isolation of the different components. Where appropriate, a pre-separation can be performed, e.g., by rotary evaporation under standard or reduced pressure.Amines can furthermore be isolated from the reaction mixture, particularly if a further solvent is present by liquid extraction methods with an appropriate solvent. Particularly, extraction with diluted water-based acids, as, for example, diluted aqueous sodium hydrogen sulfate solution,is suitable for the extraction of amines. Extraction is particularly suitable if amines are present which can not be evaporated without decomposition. From the extract containing the amine, the latter can be isolated, for example, by precipitation induced by addition of a base, i.e., pH- increase, and filtration or by evaporation or distillation or a combination thereof. The other way round, also water soluble components in the reaction mixture, like certain alcohols or the catalyst, can be selectively dissolved or extracted without dissolving the amine, if diluted waterbased bases, as for example, sodium hydrogen carbonate are used. If water-based extraction is applied to recover the aliphatic amine, the vinyl ether and optionally, remaining alcohol, is preferably isolated from the reaction mixture beforehand, e.g., by distillation during or after the termination of the vinylation reaction.Also preparative chromatographical methods can be applied to isolate and purify the amine from other components present in the final reaction mixture. Beside partition chromatography, in case where polymeric amines are used, also size exclusion chromatography techniques, e.g., gel permeation chromatography (GPC) can be applied.For the recovery of the amine from the reaction mixture, also a combination of different techniques can be applied. The selection of the methods depends on the ability of the amines to be evaporated without decomposition, their boiling point, solubility, molecular weight, and the required degree of purity of the re-isolated amine.If desired, the recovered amine can be further purified.The recovered amine can be used in any chemical process which requires its presence, including the re-use in the inventive process described in step a).In one embodiment, the process of step a) is carried out without solvent and after termination of the reaction the amine is isolated from the remaining reaction mixture by fractionated vacuum distillation.In another embodiment, the process of step a) is carried out in a continuous mode, i.e., under continuous distillation of vinyl ether and alcohol from the reaction mixture, without solvent and after termination of the reaction, the amine is isolated from the remaining reaction mixture by extraction with a diluted water-based acid, like for example sodium hydrogen sulfate. From the extract the amine is isolated by adding a diluted water-based base, like for example sodium carbonate, until the amine separates or precipitates from the aqueous phase, and subsequent phase separation or filtration. Optionally further steps, like drying or further purification of the amine, can be performed.In another embodiment, the process of step a) is carried out with an solvent having a lower boiling point than the amine but a higher boiling point than the vinyl ether and the alcohol. In this embodiment, the process of step a) is carried out in a continuous mode, i.e., under continuous distillation of vinyl ether and alcohol from the reaction mixture. After termination of the reaction, the solvent is removed by evaporation and the amine is isolated from the remaining mixture by fractionated vacuum distillation.Step c)Optionally, the amine recovered in step b) can be re-used in the inventive process described in step a).In a preferred embodiment, the amine recovered in step b) is re-used in the process described in step a).We have further found a process for the production of product P comprising: i) the preparation of a vinyl ether by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine, characterized in that the aliphatic amine comprises a primary, a secondary, or a primary and a secondary amino group, and ii) converting the vinyl ether in at least one step to obtain product P.Converting the vinyl ether to obtain product P (ii) comprises one or more step(s) as described below and can be performed by conventional methods well known to a person skilled in the art. Converting the vinyl ether to obtain product P (ii) preferably comprises one or more step(s) selected from: dissolving, diluting, dispersing, emulsifying, gasifying, solidifying, liquifying, recycling, depolymerizing, pyrolyzing, and / or steam cracking; and / or purifying, crystallizing, (solvent) extracting, distilling, evaporating, hydrotreating, absorbing, adsorbing and / or subjecting to ion exchanger; and / or assembling, preferably foaming, synthesizing, chemically converting, chemically transforming, preferably polymerizing and / or compounding; and / or forming, foaming, extruding and / or molding; and / or finishing, preferably coating and / or smoothing.The product P can be any product resulting from a conversion of a vinyl ether prepared by the process of the present invention. The conversion can comprise one or several steps. I.e., the product P can also result from a chemical material, which itself or any of its precursors result from a conversion of a vinyl ether prepared by the process of the present invention.A chemical material is a chemical compound or a mixture of chemical compounds in any physical state. The physical state can be, for example, solid, liquid, gaseous or combinations thereof. A mixture includes but is not limited to solutions, emulsions, dispersions etc.A precursor is a chemical material which can be transformed via one or more converting steps to another chemical material.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

[8005] ; ISSN: 2198-4786; published: February 12, 2024 will be regarded as Reference RF1 , which is incorporated herein by reference in its entirety. The product P can for example be a product as described in Reference RF1 ; paragraphs

[1000] to

[8005] ,The product P can be any reaction product resulting from a chemical reaction of a compound with a vinyl ether, or any mixture resulting from a compound with a vinyl ether.Preferably, the product P comprises, a product resulting from a reaction with an electrophile, like, for example, a Bronsted acid, i.e., an intermediate oxonium salt of the vinyl ether; or a product resulting from an inverse demand Diels-Alder reaction, i.e., a cyclohexene derivative; or a product resulting from a thiol-ene reaction, i.e., a thioether; or a product resulting from a reaction with hydrogen peroxide, i.e., the corresponding hydroperoxide; or an alphabromocarbonic acid ester and the corresponding beta-hydroxyester formed via Reformatzki- reaction; or a product resulting via Claisen-rearrangement, i.e., a gamma, delta-unsaturated carbonyl; or a product resulting from homo- or copolymerization, i.e., a poly(vinyl ether) or a poly(vinyl ether)-copolymer.More preferably, the product P comprises a homo- or a copolymer of a vinyl ether prepared by the process of the present invention, i.e., a poly(vinyl ether) or a poly(vinyl ether)-copolymer. These polymers can preferably be obtained by polymerizing at least one vinyl ether prepared by the process of the present invention via chain-growth polymerization, for example via block-, emulsion- or solution-polymerization, optionally by copolymerizing with other monomers, like, for example vinyl chloride, acrylonitrile, or (meth)acrylic acid derivatives. Preferred homopolymers are for example, poly(vinyl methyl ether), poly(vinyl ethyl ether), and poly(vinyl isobutyl ether). The product P resulting from a one- or multistep conversion of a vinyl ether prepared by the process of the present invention can be, for example, a polymer composition, like a formulation, a mixture, including but not limited to solutions, dispersions, emulsions, of polymers comprising for example a poly(vinyl ether) or a poly(vinyl ether)-copolymer as ingredient; or furthermore a formulation or a mixture, including but not limited to solutions, dispersions, emulsions, comprising a low molecular weight compound which itself is a vinyl ether prepared by the process of the current present invention or which results from a one- or multistep conversion of a vinyl ether prepared by the process of the present invention.In case of dispersions or emulsions, aqueous dispersions or aqueous emulsions are preferred.Any product P is in itself a chemical material, which itself or any of its precursors result from a conversion of the vinyl ether prepared by the process of the present invention.The product P can be used, for example, as a building block or monomer for further chemical transformation, and can further be used, for example, for physical mixing including formulating, dissolving, dispersing, emulsifying.Fields of application for the product P are, for example, chemical applications using P as building block for the synthesis of other chemical compounds including polymers, cleaning, descaling, agrochemical applications, like agrochemical ingredients, compositions, orformulations, pharmaceutical applications, like pharmaceutical ingredients, compositions, or formulations, animal and human nutrition, dietary supplements, aroma chemicals or aroma compositions, adhesives, fiber bonding, binders for coatings, cosmetic ingredients, compositions or formulations, foils, bodies, or other functional compositions.Coatings include but are not limited to architectural and construction coatings, industrial coatings, automotive coatings, paper coatings, fiber coatings, glass coatings, metal coatings, wood coatings, plastic coatings, stone coatings, fiber cement coatings, which can be subjected to different curing methods, like for example, normal or high-temperature drying, radiation curing, particularly UV-radiation curing.In a general embodiment of the inventive process to continuously prepare vinyl ethers, the catalyst precursor is mixed with an amine which comprises a primary, a secondary, or a primary and a secondary amino group and does not have a boiling point of below 130 °C. The amine is used in an amount corresponding to 2 to 100 molar equivalents amino groups per molar equivalent catalyst. The reaction mixture is heated to the desired temperature. Under stirring at atmospheric pressure, acetylene and alcohol are fed continuously to the reaction mixture. The reaction temperature and dosage rate are selected in a way, that the alcohol is added in a rate like it is consumed ensuring that the molar ratio of alcohol to catalyst in the reaction mixture does not exceed 10. The molar ratio can be detected, for example, via NMR spectroscopy considering amine, alcohol and alcoholate peaks of samples taken from the reaction mixture at different times. The molar ratio of catalyst precursor equivalents to the overall alcohol equivalents is selected from 0.001 to 0.1. During the reaction, the formed vinyl ether and nonreacted alcohol are continuously distilled off the reaction mixture. Thus, for this embodiment, the higher boiling component selected from alcohol and vinyl ether, needs to have a dew point at least 10 K below the reaction temperature. The distillate is collected and after termination of the reaction, subjected to analysis, and, if need be, to further purification.After termination of the reaction, optionally, the amine is recovered from the remaining reaction mixture. Depending on its boiling point, the amine can be recovered by means of distillation or by extraction. Volatile amines can be recovered by fractional distillation, if required under reduced pressure. Volatile and non-volatile amines can alternatively be recovered by acidic aqueous extraction, e.g., with an aqueous solution of sodium hydrogen sulfate, and subsequent separation by lowering the pH value of the extract. After optional further purification, the amine is re-used in the inventive process to prepare vinyl ethers or in any other process, where its presence is required.In a general embodiment of the inventive process to prepare vinyl ethers in a high-pressure semi-batch process, in a high-pressure-suited stirrable reaction vessel or autoclave, the catalyst precursor is mixed with a polyamine comprising at least two amino groups, at least one of whichis primary or a secondary amino group, and has not a boiling point lower than the boiling point of the formed vinyl ether. The amine is used in an amount corresponding to 2 to 100 molar equivalents amino groups per molar equivalent catalyst. The desired reaction temperature and acetylene overpressure is adjusted. The alcohol is added in a rate like it is consumed ensuring that the molar ratio of alcohol to catalyst in the reaction mixture does not exceed 10. The molar ratio can be detected, for example, via NMR spectroscopy considering amine, alcohol and alcoholate peaks of samples taken from the reaction mixture at different times. The molar ratio of catalyst precursor equivalents to the overall alcohol equivalents is selected from 0.001 to 0.1. In this embodiment, the formed vinyl ether remains in the reaction mixture until the end of the reaction. When the reaction has terminated, the reaction vessel is deflated to normal pressure, and the formed vinyl ether is isolated from the reaction mixture by fractionated distillation, which, depending on the boiling point of the vinyl ether can be performed under normal pressure or in vacuo. One resulting fraction contains the vinyl ether, another resulting fraction might contain non-reacted alcohol.After termination of the reaction, optionally, the amine is recovered from the remaining reaction mixture. Depending on its boiling point, the amine can be recovered by means of distillation or by extraction. Volatile amines can be recovered by fractional distillation, if required under reduced pressure. Volatile and non-volatile amines can alternatively be recovered by acidic aqueous extraction, e.g., with an aqueous solution of sodium hydrogen sulfate, and subsequent separation by lowering the pH value of the extract. After optional further purification, the amine is re-used in the inventive process to prepare vinyl ethers or in any other process, where its presence is required.It was found that the presence of aliphatic amines, which comprise a primary, a secondary, or a primary and a secondary amino group, in the synthesis of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol, leads to different advantages:Firstly, the vinylation reaction can be performed under atmospheric pressure thus lowering safety risk issues and costs for reactor infrastructure.Secondly, compared to amine-free reaction media, aromatic amine-containing reaction media, or reaction media containing purely tertiary aliphatic amines, i.e., aliphatic amines that do not contain a primary or a secondary aliphatic amino group, a higher catalyst activity is observed at atmospheric pressure leading to a combination of high space-time yields with significantly higher vinyl ether contents in the product mixture, i.e., a higher raw product purity. An advantage connected with the high raw product purity is a reduced need for, or a complete redundancy of further purification, which represents also a benefit regarding infrastructure, energy etc., and thus, costs.Thirdly, compared to aromatic amines, which are generally potentially harmful and some of them are classified as carcinogenic, the aliphatic amines used in the inventive process generally are of lower toxicological concern.Fourthly, compared to reaction media containing aromatic or purely tertiary aliphatic amines, i.e. , aliphatic amines that do not contain a primary or a secondary aliphatic amino group, the vinyl ether contents in the product mixture remain significantly higher, even at higher alcohol dosage rates. This shows once more the higher catalyst activity compared to reaction media containing aromatic or purely tertiary aliphatic amines. This allows for higher space-time-yields in combination with a higher vinyl ether content in the raw product mixture, i.e., a higher purity of the reaction raw product. Thus, the inventive process allows for a more cost efficient production of vinyl ethers.Sixthly, compared to amine-free reaction media, even with low reactive alcohols, like tert-butanol, significant amounts of vinylated alcohol are formed.Seventhly, the inventive process can be performed at atmospheric pressure also at lower temperatures, e.g., 120 °C.Eighthly, the inventive process can be performed with different catalyst precursors.Ninthly, the inventive process is more sustainable compared to comparable processes due to the lower energy demand resulting from lower required pressures and reduced need for purification as well as the possible recovery of the amine.ExamplesGeneral procedure for the vinylation of alcoholsIn a 300 ml double-jacked stirred glass reactor, equipped with a disc stirrer, baffles and a simple distillation bridge (no additional distillation column is needed), 11 ,2 g (0,1 mol) potassium tert-butoxide is suspended in 100 g of amine and heated to 160 °C inside temperature. While stirring at a rate of 800-1000 rpm, continuous dosing of 0.1 MPa acetylene, via a tube positioned under the stirrer, and alcohol, via a classical HPLC-pump, (exact acetylene and alcohol flows are indicated in table 1) is started and maintained for five hours. Due to exothermicity of the vinylation reaction the inside temperature may rise 2-5 °C, compared to the initially adjusted temperature. The formed volatile vinyl ether and non-reacted alcohol is continuously distilled out of the reaction mixture and collected in a cooling trap at 0 °C. Excess acetylene after the cooling trap is vented in the fume hood. Samples of the condensed liquid are taken every hour.Samples are analyzed by GC methods on an Agilent column DB-XLB 30m(length) I 0.25mm(diameter) 1 1 .m(film thickness) or DB-Wax 30m(length) 10.25mm(diameter) 10.25 .m(film thickness) [both for n-Butyl, i-Butyl and t-Butyl derivatives], Optima- Wax 20m(length) / 0.2mm(diameter) 10.3 .m(film thickness) [for Cyclohexyl derivatives] and Optima-Wax 30m(length) 10.25mm(diameter) 10.25 .m(film thickness) [for Ethyl derivatives] with flame- ionization-detector. In some cases small amounts of dissolved acetylene lead to a peak at early retention times, which has been neglected.The reaction time usually corresponds to 4-5 h. The results are summarized in table 1.The area-percent values listed in table 1 result from the corresponding peaks in the chromatogram and correspond essentially to the respective weight-percent values.In a first approximation, in the evaluation of the experiments, GC area -% were equated with GC mass-% without determining the corresponding (relative) response factors. In isolated cases, response factors were determined to be approximately 1.05-1.1. Since all experiments were evaluated equally, without taking into account the response factors, and this factor does not deviate significantly from 1 , the absolute deviation is negligible for the comparison presented here, and the results are comparable.able 1 (part 1). Vinyl ether formation according to the general procedure, Comparative Examples 1-10 (comp. = comparative)able 1 (part 2). Vinyl ether formation according to the general procedure, Examples 11-20able 1 (part 3). Vinyl ether formation according to the general procedure, Examples 21-32able 1 (part 4). Vinyl ether formation according to the general procedure, Examples 33-36The examples summarized in table 1 show that the vinylation of alcohols can be performed under atmospheric pressure.Furthermore, the examples summarized in table 1 show that for the reaction of isobutanol or n-butanol, despite space-time-yields of > 150 g / Lh, amine-free reaction media lead to moderate vinyl ether contents of 86.7-90.5area-% in the raw product mixture even at a lower alcohol dosage rate of ca. 20 mL / h (comparative examples 1 , 2, and 4). This shows that amine-free reaction media are only moderately active with respect to vinyl ether formation, when standard alcohols are used and do not lead to a combination of high space-time-yields and high ratios of the vinyl ether in the raw product. If tert-butanol is utilized, these reaction media are not active at all, and only a negligible amount of the corresponding vinyl ether is formed (comparative example 3).The examples summarized in table 1 furthermore show that for the reaction of isobutanol, despite space-time-yields of > 150 g / Lh, aromatic amine containing reaction media (comparative examples 5 to 9) lead to moderate vinyl ether contents of 86-91 area-% in the product mixture even at a lower alcohol dosage rate of 20 mL / h (comparative examples 5 and 6). Aromatic amines are generally potentially harmful and some of them are classified as carcinogenic. If the alcohol dosage rate is increased, the content of the corresponding vinyl ether declines significantly to 50-88area-%, even though the space-time-yield increases or remains on a level of > 150 g / Lh (comparative examples 7 to 9). This shows an only moderate activity of aromatic amine containing reaction media with respect to vinyl ether formation. They do not lead to a combination of high space-time-yields and high ratios of the vinyl ether in the raw product.The examples summarized in table 1 furthermore show that for a reaction medium containing purely tertiary aliphatic amines, i.e. , aliphatic amines that do not contain a primary or a secondary aliphatic amino group, the content of isobutyl vinyl ether in the product mixture is only 66area-% (comparative example 10). Thus, although the space-time-yield is 210 g / Lh, these reaction media show a low activity with respect to vinyl ether formation and do not lead to a combination of high space-time-yields and high ratios of the vinyl ether in the raw product. In contrast to the comparative examples, table 1 shows, that using isobutanol, the inventive examples utilizing an aliphatic amine which comprises a primary, a secondary, or a primary and a secondary amino group, lead to both, high space-time-yields in the range of 180 g / Lh, and very high vinyl ether contents of > 98area-% in most cases (example 16, 26-28, 30) at a lower alcohol dosage rate of 20 mL / h. Furthermore, if the dosage rate of the alcohol is increased to 30, 40, 50, or even 80 mL / h, the space-time yields increase to levels from above 250 g / Lh up to levels above 700 g / Lh, and the vinyl ether content in the product mixture remains on a very high level of > 97area-% in most cases (examples 11, 12, 15, 17, and 19-25). This shows a very high activity of the reaction system described in the inventive process, leading to a combination of both, high space-time-yields and high ratios of the vinyl ether in the raw product. This highactivity is also observed with alcohols other than isobutanol (examples 31 to 36). Particularly, the vinyl ether content of 58area-% and a space-time-yield of 86.1 g / Lh when using tert-butanol (example 33), is remarkable. Examples 13 and 14 show for isobutyl vinyl ether, that the inventive process to produce vinyl ethers also leads to high vinyl ether contents and space-time- yields > 150 g / Lh at lower temperatures or if an alternative catalyst precursor is used.In summary, the inventive examples show that the inventive process utilizing an aliphatic amine which comprises a primary, a secondary, or a primary and a secondary amino group at atmospheric pressure allows for high space-time-yields in combination with high ratios of the corresponding vinyl ethers in the raw product., i.e. , a higher purity of the reaction raw product.

Claims

Claims1. Process for the preparation of vinyl ethers by reacting an alcohol with acetylene in the presence of an alkali metal salt of the alcohol and an aliphatic amine, characterized in that the aliphatic amine comprises a primary, a secondary, or a primary and a secondary amino group.

2. Process according to claim 1, wherein the alcohol comprises 1 to 20 carbon atoms and an OH-group bound to an aliphatic saturated carbon atom.

3. Process according to any of claims 1 to 2, wherein the alkali metal salt of the alcohol is formed by the reaction of the alcohol with a catalyst precursor comprising an alkali metal alkoxide or an alkali metal hydroxide or a mixture of both.

4. Process according to any of claims 1 to 3, wherein the aliphatic amine is a polyamine comprising at least two amino groups, at least one of which is a primary or a secondary amino group.

5. Process according to any of claims 1 to 4, wherein the aliphatic amine does not have a boiling point < 130 °C at a standard pressure of 101.3 kPa.

6. Process according to any of claims 1 to 5, wherein the molar ratio of catalyst precursor equivalents to alcohol equivalents is 0.001 to 0.1.

7. Process according to any of claims 1 to 6, wherein the aliphatic amine is used in an amount corresponding to 2 to 100 molar equivalents amino groups per molar equivalent catalyst precursor.

8. Process according to any of claims 1 to 7, wherein the reaction is performed in the presence of a solvent.

9. Process according to any of claims 1 to 8, wherein the reaction is performed at an absolute pressure of 0.01-2,5 MPa.

10. Process according to any of claims 1 to 9, wherein the reaction is performed at a temperature of 50-250 °C.

11. Process according to any of claims 1 to 10 performed as a continuous process, wherein in the steady state of this continuous process, the molar ratio of alcohol to catalyst in the reaction mixture is < 10.

12. Process according to claim 11 , wherein the formed vinyl ether and non-converted alcohol are removed continuously from the reaction mixture.

13. Process comprising the following steps: a) Synthesis of vinyl ethers by the process according to any of claims 1 to 12, b) Recovery of the amine from the reaction mixture, c) Optional re-use of the recovered amine in a process according to any of claims 1 to 12.

14. Process for the production of product P comprising: i) the preparation of a vinyl ether according to any of claims 1 to 13ii) converting the vinyl ether in at least one step to obtain product P.

15. Process according to claim 14, wherein product P comprises a poly(vinyl ether) or a poly(vinyl ether)-copolymer.