Method for recovering methyl and vinyl substituted pyridines

Abstract

The invention relates to a method for recovering a methyl and vinyl substituted pyridine from a mixture (M1) comprising the methyl and vinyl substituted pyridine and a methyl and ethyl substituted pyridine.

Description

[0001] METHOD FOR RECOVERING METHYL AND VINYL SUBSTITUTED PYRIDINES

[0002] Technical Field

[0003] The invention relates to a method for recovering a methyl and vinyl substituted pyridine such as 2- methyl-5-vinyl pyridine (MVP) from a mixture (M1) comprising the methyl and vinyl substituted pyridine such as MVP and a methyl and ethyl substituted pyridine such as 2-methyl-5-ethyl pyridine (MEP).

[0004] Technological Background

[0005] Methyl and vinyl substituted pyridines such as 2-methyl-5-vinyl pyridine (MVP) can be produced by dehydrogenation of the respective methyl and ethyl substituted pyridines such as 2-methyl-5-ethyl pyridine (MEP). Said process is usually producing an MVP crude product having an MVP concentration of about 20-30%, the rest being starting material MEP, water, and impurities.

[0006] Methyl and vinyl substituted pyridines (e.g. MVP) serve as starting materials for several reactions such as polymerization reactions (providing polymerized MVP, also referred to as poly MVP) and other total synthesis and must therefore have a certain purity. MVP may also be used as an oil additive, ore flotation agent, and dye acceptor. Polymerization reactions can be performed under acidic conditions such as in the presence of HCI or H2SO4. Thus, the use of methyl and vinyl substituted pyridine such as MVP as an intermediate for other target products usually makes a purification step necessary to remove or reduce water, methyl and ethyl substituted pyridines such as MEP, and impurities. In particular, methyl and vinyl substituted pyridine (such as MVP) concentrations of higher than 90 wt.-% are often desirable.

[0007] A purification of e.g. MVP crude by means of crystallization is described in US2786058. However, this is not a preferred industrial method to be followed, because temperatures at around -26 °C are applied, the crystallization is time consuming, and additional solid handling is necessary. Furthermore, a pre-concentration step up to at least 60% MVP is still needed. Distillation of the methyl and vinyl substituted pyridine may be pursued. In this connection, it should be noted that e.g. a mixture comprising MVP and MEP can be separated into MVP and MEP via distillation. However, the two compounds have almost similar boiling points, at atmospheric pressure. MEP boils at about 176 °C and MVP at about 179 °C. Industrial distillation at such temperature levels is infeasible, since MVP tends to polymerize at these temperatures, also in the presence of polymerization inhibitors. Therefore, the distillation has to be carried out at reduced pressure. Anyway, an impractical high number of separation stages are needed to separate MVP from MEP to get to a concentration of MVP more than 90 wt.-%, without losing too much MVP in the MEP fractions.

[0008] The addition of acids during the extraction or distillation of MVP is described in US2716120, US2879272, US4868309, or GB852129. The relative volatility or solubility of MEP and MVP can be influenced, the two molecules having a slightly different pKa. However, the acids have to be neutralized to isolate the protonated MEP, which generates a lot of salts. Thus, such a process is waste intensive.

[0009] GB1184288 discloses a method of recovering MVP in the presence of a substituted pyridine. However, the MVP obtained via this method comprises undesired discoloration. In addition, the feed stock comprises MVP in an amount of at least 36 wt.-%. Thus, a pre-concentration is necessary after the dehydrogenation.

[0010] Against this background there is an ongoing need of a simple separation method of substituted pyridines having similar boiling points (such as MVP and MEP), preferably comprising reduced distillation steps and / or reduced manufacturing costs.

[0011] Summary of the invention

[0012] It is an object of the present invention to provide a method of recovering methyl and vinyl substituted pyridine (e.g. MVP) from a mixture (M1) comprising the methyl and vinyl substituted pyridine (e.g. MVP) and a methyl and ethyl substituted pyridine (e.g. MEP). Further, it is an object of the present invention to provide a respective separation method having reduced manufacturing costs and / or reduced distillation step. Further, it is an object of the present invention to provide a respective separation method with a reduced loss of methyl and vinyl substituted pyridine (e.g. MVP) in other distillation fractions. In addition, it is an object of the present invention to provide an economic (e.g. less time consuming) and environmentally friendly method, wherein e.g. ingredients can be recycled. Finally, it is an object of the present invention to provide particularly pure methyl and vinyl substituted pyridine, in particular MVP.

[0013] At least one of the above object can be achieved by the method of the present invention.

[0014] In a first aspect, the invention relates to a method for recovering a methyl and vinyl substituted pyridine from a mixture (M1) comprising the methyl and vinyl substituted pyridine and a methyl and ethyl substituted pyridine, the method comprising the steps of a) distilling the methyl and ethyl substituted pyridine from said mixture (M1) in the presence of an organic entrainer at a sump temperature of about 30 to about 100 °C and a pressure of about 5 to about 50 mbar providing a mixture (M2) comprising the methyl and vinyl substituted pyridine as high boiling fraction; and b) distilling the methyl and vinyl substituted pyridine from said mixture (M2) providing the methyl and vinyl substituted pyridine as light boiling fraction.

[0015] In a second aspect, the invention relates to a methyl and vinyl substituted pyridine obtained by a method according to the first aspect (including all preferred embodiments), preferably wherein the methyl and vinyl substituted pyridine is 2-methyl-5-vinyl pyridine (MVP).

[0016] In a third aspect, the invention relates to a methyl and ethyl substituted pyridine and / or an organic entrainer obtained by the method according to the first aspect, wherein the method further comprises the step of recovering the organic entrainer and / or the methyl and ethyl substituted pyridine via distillation.

[0017] Brief description of the drawings

[0018] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which:

[0019] Figure 1 is a schematic view of a distillation pathway comprising a water distillation via a distillation column, a methyl and ethyl substituted pyridine distillation via a distillation column, and a methyl and vinyl substituted pyridine distillation setup. Optionally, the third distillation setup can include a wiped film evaporator being attached to a distillation column. All three distillation steps can be run batchwise, semi-batchwise or continuously. Detailed description of preferred embodiments

[0020] In the following, the invention will be explained in more detail.

[0021] The terms “about” in the context of the present invention denotes an interval of accuracy that a person skilled in the art will understand to still ensure the technical effect of the feature in question. The term typically indicates a deviation from the indicated numerical value of ±5%, preferably ±3%, more preferably ±2%, and in particular ±1%.

[0022] As used herein, the articles “a” and “an” preceding an element or component are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore, “a” or “an” is to be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

[0023] According to the present invention, the term “organic entrainer” refers to any organic solvent that is mixable with, preferably dissolves, the fluids to be separated. It is to be understood that the organic entrainer is different to the fluids to be separated.

[0024] According to the present invention, the term “distillate flow rate” refers to the mass flow rate of the distillate stream leaving the system (mass / time such as g / h or kg / h).

[0025] The organic moieties mentioned in the above definitions of the variables are - like the term halogen - collective terms for individual listings of the individual group members. The prefix Cn-Cm indicates in each case the possible number of carbon atoms in the group.

[0026] According to the present invention, the term “alkyl” refers to a straight-chained or branched saturated hydrocarbon group having 1 to 6 carbon atoms, such as 1 , 2, 3, 4, 5, or 6 carbon atoms. Likewise, the term “C1-C4-alkly” refers to a straight-chained or branched saturated hydrocarbon group having 1 to 4 carbon atoms (i.e. 1 , 2, 3, or 4 carbon atoms) including ethyl, propyl, 1 -methylethyl, butyl, 1 -methylpropyl, 2-methylpropyl, and 1,1-dimethylethyl.

[0027] According to the present invention, the term “haloalkly” refers to a linear (i.e. straight-chain) or branched saturated hydrocarbon group having usually from 1 to 6 carbon atoms, frequently from 1 to 4, or 1 to 3, or 1 to 2 carbon atoms, wherein the hydrogen atoms of this group are partially or totally replaced with halogen atoms. Preferred haloalkyl moieties are selected from C1-C4-haloalkyl, more preferably from C1-C3-haloalkyl or C1-C2-haloalkyl, in particular from C1-C2-fluoroalkyl such as fluoromethyl, difluoromethyl, trifluoromethyl, 1 -fluoroethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2- trifluoroethyl, pentafluoroethyl, and the like. According to the present invention, the term “halogen” refers to fluorine, chlorine, bromine and iodine.

[0028] According to the present invention, the term “aromatic” refers to a ring system fulfilling the Huckel rule - having (4n+n2) electrons, with n being 0 or an integer of preferably 1 to 3.

[0029] According to the present incretion, the term “non-aromatic” refers to ring systems not fulfilling the Huckel rule, i.e. saturated, partially or fully unsaturated ring systems, preferably to 3- to 9-menbered such as 4- to 8-membered, and in particular 5- or 6-membered monocyclic ring systems. Saturated means that only single bond are present and partially or fully unsaturated means that one or more double bonds may be present in suitable positions, while the Huckel rule for aromaticity is not fulfilled. The term “non-aromatic heterocyclic compound” refers to a non-aromatic ring comprising one or more, same or different heteroatoms selected from N, O or S, preferably N and O, and wherein each substitutable carbon or heteroatom in the heterocyclic ring is independently unsubstituted or substituted with one or more, same or different substituents RF, wherein RFis halogen, -OH, or optionally substituted Ci-Cio-alkyl, preferably Ci-C4-alkyl, and in particular methyl.

[0030] Combinations of substituents / moieties envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds. The term “stable”, as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein.

[0031] It needs to be understood that the term “comprising” is not limiting. For the purposes of the present invention, the term “consisting of’ is considered to be a preferred embodiment of the term “comprising of’. If hereinafter a group is defined to comprise at least a certain number of embodiments, this is also meant to encompass a group which preferably consists of these embodiments only.

[0032] As outlined above, subject of the present invention is in a first aspect a method for recovering a methyl and vinyl substituted pyridine from a mixture (M1) comprising the methyl and vinyl substituted pyridine and a methyl and ethyl substituted pyridine, the method comprising the steps of a) distilling the methyl and ethyl substituted pyridine from said mixture (M1) in the presence of an organic entrainer at a sump temperature of about 30 to about 100 °C and a pressure of about 5 to about 50 mbar providing a mixture (M2) comprising the methyl and vinyl substituted pyridine as high boiling fraction; and b) distilling the methyl and vinyl substituted pyridine from said mixture (M2) providing the methyl and vinyl substituted pyridine as light boiling fraction.

[0033] The inventive method provides an excellent route for separating methyl and vinyl substituted pyridine from methyl and ethyl substituted pyridine having similar boiling points via distillation. Particularly, it has been surprisingly found that the inventive method provides methyl and vinyl substituted pyridine (e.g. MVP) in high purity without having remarkable yield loss of the methyl and vinyl substituted pyridine (e.g. MVP) in the light boiling fraction of step a). In addition, the inventive method provides the possibility to reuse the methyl and ethyl substituted pyridine (e.g. MEP) as starting material and / or the applied organic entrainer. The invention method is particularly suitable to perform directly after dehydrogenation of methyl and ethyl substituted pyridines. Further, the inventive method reduces the tendency to form rubber-like residues (which are not soluble in most solvents and are thus difficult to remove) in the evaporator or the column.

[0034] In the following, particular embodiments of the present invention are described in further detail. It is to be understood that each embodiment is relevant on its own as well as in combination with other embodiments.

[0035] In one embodiment, the organic entrainer has a boiling point of about 110 to about 180 °C, preferably of about 115 to about 170 °C, more preferably of about 120 to about 140 °C, and in particular of about 125 to about 135 °C.

[0036] In one embodiment, the ratio of the organic entrainer related to the mixture (M1 ) is from about 0.02 to about 0.5 wt / wt, preferably from about 0.03 to about 0.4 wt / wt, and in particular from about 0.05 to about 0.35 wt / wt.

[0037] In one embodiment, the organic entrainer is an alkanolamine and / or a heterocyclic compound (HC).

[0038] In one embodiment, the organic entrainer is an alkanolamine selected from the group consisting of ethanolamine, 1-aminopropan-2-ol, 3-amino-1 -propanol, N-formylmorpholine, N-alkylmorpholine such as N-methylmorpholine, and mixtures thereof, preferably ethanolamine.

[0039] In one embodiment, the organic entrainer is a heterocyclic compound (HC) comprising at least one amine atom in the ring. In one embodiment, the heterocyclic compound (HC) is a saturated, partially or fully unsaturated, or aromatic heterocyclic ring, wherein said heterocyclic ring comprising one or more, same or different heteroatoms selected from N or O, wherein said N-atoms are independently oxidized or non-oxi- dized, and wherein each substitutable carbon or heteroatom in the heterocyclic ring is independently unsubstituted or substituted with one or more, same or different substituents RF, wherein RFis halogen, -OH, or optionally substituted Ci-Cio-alkyl.

[0040] In one embodiment, the heterocyclic compound (HC) is an aromatic heterocyclic ring comprising one or more, same or different heteroatoms selected from N or O, preferably N, and wherein each substitutable carbon or heteroatom in the heterocyclic ring is independently unsubstituted or substituted with one or more, same or different substituents RF, wherein RFis halogen, -OH, or optionally substituted Ci-Cio-alkyl, preferably Ci-C4-alkyl, and in particular methyl. Suitably, the heterocyclic compound (HC) is a compound selected from the group consisting of 2,3-lutidine, 2,4-lutidine, 2,5- lutldine, 2,6-lutldine, 3,4-lutldine, 3,5-lutldine, 2-picoline, 3-picoline, 4-picoline, and mixtures thereof, preferably 2,5-lutidine, 2,6-lutidine, 2-picoline, and mixtures thereof.

[0041] In one embodiment, the organic entrainer is a non-aromatic organic entrainer, preferably a non-aro- matic heterocyclic compound such as morpholine.

[0042] In one embodiment, the organic entrainer is a compound of formula (1) wherein

[0043] R1and R2are independently hydrogen, halogen, C1-C4-alkly, or C1-C4-haloalkly or wherein R1and

[0044] R2represent =0;

[0045] R3and R4are independently hydrogen, halogen, C1-C4-alkly, or C1-C4-haloalkly or wherein R3and

[0046] R4represent =0;

[0047] A1is O, NH, NRA, C=0, or CHRB;

[0048] A2is O, NH, NRA, C=0, or CHRB;

[0049] A3is O, NH, NRA, C=0, or CHRB;

[0050] A4is O, NH, NRA, C=0, or CHRB;

[0051] RAis C1-C3-alkly, or C1-C3-haloalkly; RBis hydrogen, halogen, C1-C3-alkly, or C1-C3-haloalkly; and wherein at least one of A1to A4is O, NH or NRA.

[0052] In one embodiment, R1and R2are independently hydrogen, halogen, C1-C2-alkly, or C1-C2- haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen.

[0053] In one embodiment, R3and R4are independently hydrogen, halogen, C1-C2-alkly, or C1-C2- haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen.

[0054] In one embodiment, at least one A1to A4is NH. In one embodiment, only one of A1to A4is NH.

[0055] In one embodiment, at least one A1to A4is O. In one embodiment, only one of A1to A4is O.

[0056] In one embodiment, at least two of A1to A4are independently CH2 or CH-CH3, and in particular CH2.

[0057] In one embodiment, at least one A1to A4is NH and at least one A1to A4is O. In one embodiment, only one of A1to A4is NH and only one of A1to A4is O. In a preferred embodiment, A1is O and A4is NH. In this connection, it is preferred that A2and A3are independently CH2 or CH-CH3, and in particular CH2.

[0058] In one embodiment,

[0059] R1and R2are independently hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen;

[0060] R3and R4are independently hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen;

[0061] A1is O, NH, or NRA, preferably O or NH, and in particular O;

[0062] A2is CH2 or CHRB, preferably CH2 or CH-CH3, and in particular CH2;

[0063] A3is CH2 or CHRB, preferably CH2 or CH-CH3, and in particular CH2;

[0064] A4is O, NH, or NRA, preferably NH or N-CH3, and in particular NH;

[0065] RAis C1-C2-alkly or C1-C2-haloalkly, preferably methyl or trifluoromethyl, and in particular methyl;

[0066] RBis hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly, preferably hydrogen, methyl, or trifluoromethyl, and in particular hydrogen.

[0067] In a preferred embodiment, the organic entrainer is morpholine. Without being bound by any theory it is considered that morpholine (and derivatives thereof) has an improved solubility of solid residues (including rubber-like residues) being potentially created during the distillation and that thus morpholine (and derivatives thereof) are particularly suitable as organic entrainer.

[0068] In one embodiment, the mixture (M1) comprises up to about 75 wt.-%, preferably about 10 to about 65 wt.-%, more preferably about 15 to about 55 wt.-%, and in particular about 20 to about 45 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1). Suitably, the mixture (M1) comprises up to 45 wt.-%, preferably about 20 to about 45 wt.-%, more preferably about 25 to about 42 wt.-%, and in particular about 28 to about 40 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1). Alternatively, the mixture (M1) comprises up to 35 wt.-%, preferably about 10 to about 35 wt.-%, more preferably about 15 to about 33 wt.-%, and in particular about 20 to about 30 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1).

[0069] In one embodiment, the mixture (M1) comprises up to about 30 wt.-% such as up to about 28 wt.-%, or up to about 25 wt.-%, or up to about 22 wt.-%, of water based on the total amount of the mixture (M1). Suitably, the mixture (M1) comprises less than about 10 wt.-%, preferably less than about 5 wt.-%, or less than about 3 wt.-%, or less than about 2 wt.-%, of water based on the total amount of the mixture (M1). Alternatively, the mixture (M1) comprises up to about 28 wt.-%, preferably about 10 to about 28 wt.-%, or about 15 to about 25 wt.-%, or about 18 to about 22 wt.-%, of water based on the total amount of the mixture (M1).

[0070] In one embodiment, the mixture (M2) comprises at least about 70 wt.-%, preferably at least about 75 wt.-%, more preferably at least about 80 wt.-%, and in particular at least about 84 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M2). Typically, the mixture (M2) comprises up to about 96 wt.-%, preferably up to about 95 wt.-%, more preferably up to about 93 wt.-%, and in particular up to about 92 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M2).

[0071] In one embodiment, the methyl and vinyl substituted pyridine is selected from the group consisting of 2-methyl-3-vinyl pyridine, 2-methyl-4-vinyl pyridine, 2-methyl-5-vinyl pyridine, 2-methyl-6-vinyl pyridine, 3-methyl-2-vinyl pyridine, 3-methyl-4-vinyl pyridine, 3-methyl-5-vinyl pyridine, 3-methyl-6- vinyl pyridine, 4-methyl-2-vinyl pyridine, 4-methyl-3-vinyl pyridine, 4-methyl-5-vinyl pyridine, and 4- methyl-6-vinyl pyridine, preferably 2-methyl-5-vinyl pyridine (MVP).

[0072] In one embodiment, the methyl and vinyl substituted pyridine has a boiling point of about 150 to about 210 °C, preferably of about 160 to about 200 °C, more preferably of about 170 to about 190 °C, and in particular of about 175 to about 185 °C such as about 179 °C. In one embodiment, the methyl and ethyl substituted pyridine is selected from the group consisting of 2-methyl-3- ethyl pyridine, 2-methyl-4-ethyl pyridine, 2-methyl-5-ethyl pyridine, 2-methyl-6-ethyl pyridine, 3-methyl-2-ethyl pyridine, 3-methyl-4-ethyl pyridine, 3-methyl-5-ethyl pyridine, 3-methyl-6- ethyl pyridine, 4-methyl-2 ethyl pyridine, 4-methyl-3-ethyl pyridine, 4-methyl-5-ethyl pyridine, and 4- methyl-6-ethyl pyridine, preferably 2-methyl-5-ethyl pyridine (MEP).

[0073] In one embodiment, the methyl and ethyl substituted pyridine has a boiling point of about 145 to about 205 °C, preferably of about 155 to about 195 °C, more preferably of about 165 to about 185 °C, and in particular of about 170 to about 180 °C such as about 176 °C.

[0074] In one embodiment, the methyl and vinyl substituted pyridine and the methyl and ethyl substituted pyridine have a boiling point difference of about 1 to about 15 °C, preferably of about 2 to about 10 °C, and in particular of about 2 to about 5 °C.

[0075] In a preferred embodiment, the methyl and vinyl substituted pyridine is 2-methyl-5-vinyl pyridine (MVP) and the methyl and ethyl substituted pyridine is 2-methyl-5-ethyl pyridine (MEP).

[0076] In one embodiment, step a) is performed at a sump temperature of about 40 to about 90 °C and a pressure of about 5 to about 40 mbar, preferably at a sump temperature of about 50 to about 80 °C and a pressure of about 5 to about 30 mbar, and in particular a sump temperature of about 65 to about 75 °C and a pressure of about 10 to about 20 mbar.

[0077] In one embodiment, in step a) the top temperature is of about 20 to about 60 °C, preferably of about 25 to about 55 °C, more preferably of about 30 to about 50 °C, and in particular of about 35 to about 48 °C.

[0078] In one embodiment, the distillation column (e.g. entrainer-distillation column) in step a) has a jacket temperature (also known as mantle temperature) of about 80 to about 160 °C, preferably of about 90 to about 140 °C, more preferably of about 100 to about 120 °C. In this connection, the pressure in said distillation column is preferably of about 5 to about 40 mbar, more preferably of about 5 to about 30 mbar, and in particular of about 10 to about 20 mbar.

[0079] In one embodiment, the distillate flow rate in step a) is of about 20 to about 150 g / h, preferably of about 40 to about 130 g / h, more preferably of about 60 to about 120 g / h, and in particular of about 70 to about 100 g / h. In one embodiment, the distillate flow rate in step a) is of about 100 to about 900 g / h, such as of about 150 to about 800 g / h, or of about 200 to about 700 g / h, or of about 250 to about 600 g / h. In one embodiment, the distillate flow rate in step a) is of about 1 to about 600 kg / h, such as of about 10 to about 500 kg / h, or of about 15 to about 400 kg / h, or of about 20 to about 350 kg / h.

[0080] In one embodiment, step a) is performed at a reflux ratio of about 10:1 to about 1:6, preferably of about 8:1 to about 1 :5, more preferably of about 6:1 to about 1 :4, even more preferably of about 4:1 to about 1 :3, and in particular of about 3:1 to about 1 :2. In this connection, it is to be understood that eh reflux ratio generally refers to L / D, wherein L the mass flow rate of the liquid reflux returned to the column from the condenser (mass / time such as g / h) and D denotes the distillate flow rate (mass / time such as g / h).

[0081] In one embodiment, in distilling step a) a polymerization inhibitor is added.

[0082] Any suitable polymerization inhibitor may be applied. In one embodiment, the polymerization inhibitor is selected from the group consisting of sulphur, methylene blue, a sulphydryl compound, phenothiazine, benzoquinone dioxime, hydroquinone, tert-butyl catechol, and mixtures thereof, preferably selected from the group consisting of phenothiazine, benzoquinone dioxime, hydroquinone, tert-bu- tylcatechol, and mixtures thereof.

[0083] In one embodiment, the polymerization inhibitor is provided as solution, preferably in a methyl and ethyl substituted pyridine, more preferably in the same methyl and ethyl substituted pyridine that is present in mixture (M1 ). In a preferred embodiment, the polymerization inhibitor is provided as solution in 2-methyl-5-ethyl pyridine (MEP).

[0084] In one embodiment, the polymerization inhibitor is added to the distillation sump or dosed at the top of a distillation column during the distillation.

[0085] In one embodiment, the polymerization inhibitor is applied in an amount of 1 to 800 mg, preferably of 5 to 700 mg, more preferably of 10 to 500 mg, and in particular of 50 to 300 mg, of the inhibitor per 100 g of the mixture (M 1 ).

[0086] In step a), the light boiling fraction typically comprises the organic entrainer and the methyl and ethyl substituted pyridine. In one embodiment, the method further comprises collecting the light boiling fraction obtained in distilling step a) comprising the organic entrainer and the methyl and ethyl substituted pyridine. In one embodiment, the organic entrainer and / or the methyl and ethyl substituted pyridine are recovered via distillation. In this connection, said distillation provides the organic entrainer (e.g. morpholine) as light boiling fraction and the methyl and ethyl substituted pyridine (e.g. MEP) as high boiling fraction.

[0087] In one embodiment, the obtained methyl and ethyl substituted pyridine has a purity of more than about 80 wt.-%, or more than about 90 wt.-%, or more than about 95 wt.-%, or more than about 98 wt.-%.

[0088] In one embodiment, the obtained organic entrainer has a purity of more than about 80 wt.-%, or more than about 90 wt.-%, or more than about 95 wt.-%, or more than about 98 wt.-%.

[0089] In this connection, the method provides the possibility to reuse the applied organic entrainer in distillation step a). In addition, the method provides the possibility to reuse the methyl and ethyl substituted pyridine as starting material in e.g. dehydrogenation reaction to methyl and vinyl substituted pyridine.

[0090] In one embodiment, methyl and vinyl substituted pyridine (e.g. MVP) obtained in distillation step b) has a purity of at least 90 wt.-%, preferably at least about 92 wt.-%, or at least about 94 wt.-%, or at least about 96 wt.-%, or at least about 98 wt.-%.

[0091] In one embodiment, step b) is performed at a sump temperature of about 40 to about 90 °C and a pressure of about 5 to about 40 mbar, preferably at a sump temperature of about 50 to about 80 °C and a pressure of about 5 to about 30 mbar, and in particular a sump temperature of about 65 to about 75 °C and a pressure of about 10 to about 20 mbar.

[0092] In one embodiment, in step b) the top temperature is of about 40 to about 90 °C, preferably of about 50 to about 85 °C, more preferably of about 60 to about 80 °C, and in particular of about 65 to about 75 °C.

[0093] In one embodiment, the distillation step b) is performed in a wiped film evaporator being attached to a distillation column. The application of a wiped film evaporator provides a particularly mild separation method.

[0094] Typically, the inventive method provides an efficient discoloration of the methyl and vinyl substituted pyridine (e.g. MVP). In this connection, a sufficient discoloration denotes that the methyl and vinyl substituted pyridine (e.g. MVP) obtained in distillation step b) has a lower Yellowness Index than the mixture (M2). In one embodiment, the distillation column in distillation step a) and / or distillation step b) comprises less than about 50 theoretical stages, preferably less than 35 theoretical stages such as less than 25 theoretical stages, or less than 20 theoretical stages, or less than 15 theoretical stages, or less than 14 theoretical stages, or less than 13 theoretical stages, or less than 11 theoretical stages, or less than 10 theoretical stages. Suitably, the distillation column in distillation step b) comprises less theoretical stages than the distillation column in distillation step a). In one embodiment, the distillation column in distillation step a) comprises 15 to 25, or 17 to 22, or 19 to 21 , theoretical stages and the distillation step b) comprises 10 to 20, or 12 to 18, or 13 to 15, theoretical stages.

[0095] In one embodiment, distillation step a) and / or distillation step b) is performed in the presence of sump dilution agents. Sump dilution agents can be added to facilitate handling of the high boiling residue. Suitable sump dilution agents are polyethylene glycols (PEG) or akolidlnes.

[0096] The process may be carried our continuously or batchwise, preferably continuously.

[0097] In one embodiment, the method comprises prior to distilling step a), a step a.I) distilling water from a mixture (M1.i) comprising the methyl and vinyl substituted pyridine, the methyl and ethyl substituted pyridine, and water, providing the mixture (M1) as high boiling fraction.

[0098] In one embodiment, step a.i) is performed at a sump temperature of about 40 to about 110 °C and a pressure of about 8 to about 60 mbar, preferably at a sump temperature of about 50 to about 100 °C and a pressure of about 10 to about 55 mbar, more preferably at a sump temperature of about 60 to about 90 °C and a pressure of about 20 to about 50 mbar, and In particular at a sump temperature of about 70 to about 85 °C and a pressure of about 25 to about 40 mbar.

[0099] In one embodiment, in step a.i) the top temperature is of about 5 to about 40 °C, preferably of about 8 to about 35 °C, more preferably of about 10 to about 30 °C, and in particular of about 15 to about 25 °C.

[0100] In one embodiment, the mixture (M1 .i) comprises about 5 to about 35 wt.-%, preferably about 10 to about 35 wt.-%, more preferably about 15 to about 33 wt.-%, and in particular about 20 to about 30 wt.-%, of the methyl and vinyl substituted pyridine (e.g. MVP) based on the total amount of the mixture (M 1 .i). In this connection, the obtained mixture (M1) suitably comprises up to 45 wt.-%, preferably about 20 to about 45 wt.-%, more preferably about 25 to about 42 wt.-%, and in particular about 28 to about 40 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1). In one embodiment, the mixture (M1.i) comprises up to about 28 wt.-%, preferably about 10 to about 28 wt.-%, or about 15 to about 25 wt.-%, or about 18 to about 22 wt.-%, of water based on the total amount of the mixture (M1 .i) and / or up to 35 wt.-%, preferably about 10 to about 35 wt.-%, more preferably about 15 to about 33 wt.-%, and in particular about 20 to about 30 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1.i). In this connection, the obtained mixture (M1) suitably comprises less than about 10 wt.-%, preferably less than about 5 wt.-%, or less than about 3 wt.-%, or less than about 2 wt.-%, of water based on the total amount of the mixture (M1).

[0101] As aforementioned, the present invention further relates in a second aspect to a methyl and vinyl substituted pyridine obtained by a method according to the first aspect.

[0102] Particular embodiments (e.g. regarding the method conditions, the organic entrainer, the methyl and vinyl substituted pyridine) are already above-outlined In the Inventive method and shall hold for the second aspect, as well. In the following, particular embodiments of the second aspect are described in further detail. It is to be understood that each embodiment is relevant on Its own as well as in combination with other embodiments.

[0103] In one embodiment, the methyl and vinyl substituted pyridine is 2-methyl-5-vinyl pyridine (MVP).

[0104] In one embodiment, the methyl and vinyl substituted pyridine such as 2-methyl-5-vinyl pyridine (MVP) has a purity of at least about 90 wt.-%, preferably at least about 92 wt.-%, or at least about 94 wt.-%, or at least about 96 wt.-%, or at least about 98 wt.-%.

[0105] In one embodiment, the methyl and vinyl substituted pyridine such as 2-methyl-5-vinyl pyridine (MVP) comprises less than 5.0%, preferably less than 3.0%, more preferably less than 2.0% such as less than 1 .0%, of residues.

[0106] In this connection, residues may encompass methyl and ethyl substituted pyridine, organic entrainer, and / or by-products.

[0107] In one embodiment, the methyl and vinyl substituted pyridine such as MVP has a lower Yellowness Index than the mixture (M2). As aforementioned, the present invention further relates in a third aspect to methyl and ethyl substituted pyridine and / or an organic entrainer obtained by the method according to the first aspect, wherein the method further comprises the step of recovering the organic entrainer and / or the methyl and ethyl substituted pyridine via distillation.

[0108] Particular embodiments (e.g. regarding the method conditions, the organic entrainer, the methyl and vinyl substituted pyridine) are already above-outlined in the inventive method and shall hold for the third aspect, as well. In the following, particular embodiments of the third aspect are described in further detail. It is to be understood that each embodiment is relevant on its own as well as in combination with other embodiments.

[0109] In one embodiment, the methyl and ethyl substituted pyridine has a purity of more than about 80 wt.-%, or more than about 90 wt.-%, or more than about 95 wt.-%, or more than about 98 wt.-%.

[0110] In one embodiment, the methyl and ethyl substituted pyridine comprises less than 5.0%, preferably less than 3.0%, more preferably less than 2.0% such as less than 1.0%, of residues.

[0111] In this connection, residues may encompass methyl and vinyl substituted pyridine, organic entrainer, and / or by-products.

[0112] In one embodiment, the organic entrainer has a purity of more than about 80 wt.-%, or more than about 90 wt.-%, or more than about 95 wt.-%, or more than about 98 wt.-%.

[0113] In one embodiment, the organic entrainer comprises less than 5.0%, preferably less than 3.0%, more preferably less than 2.0% such as less than 1.0%, of residues.

[0114] In this connection, residues may encompass methyl and ethyl substituted pyridine, methyl and vinyl substituted pyridine, and / or by-products.

[0115] In one embodiment, the methyl and ethyl substituted pyridine is MEP.

[0116] In one embodiment, the organic entrainer is morpholine.

[0117] It will be obvious for a person skilled in the art that these embodiments only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention. The present invention will be further illustrated by Figure 1.

[0118] Figure 1 is a schematic view of a distillation pathway comprising a water distillation via a distillation column, a methyl and ethyl substituted pyridine entrainer distillation via a distillation column, and a methyl and vinyl substituted pyridine distillation via a wiped film evaporator being attached to a distillation column.

[0119] In particular, Figure 1 depicts schematically a separation of a methyl and vinyl substituted pyridine (such as 2-methyl-5-vinyl pyridine; MVP) and a methyl and ethyl substituted pyridine (such as 2-me- thyl-5-ethyl pyridine; MEP). The methyl and vinyl substituted pyridine (such as MVP) crude (6) comprising about 23 wt.-% methyl and vinyl substituted pyridine (such as MVP) is fed into dewatering distillation column (4) having a pressure of about 30 mbar. The sump temperature is of about 77 °C, the top temperature is of about 21 °C and water (8) is being removed from the dewatering distillation column (4) via a condenser. A mixture of methyl and vinyl substituted pyridine / a methyl and ethyl substituted pyridine (such as MVP / MEP) (13) is transferred into entrainer-distillation column (9). Polymerization inhibitor dissolved in MEP (1) is dosed at the top of entrainer-distillation column (9) and the organic entrainer, such as morpholine, (26) is fed into entrainer-distillation column (9). The entrainer-distillation column (9) has a pressure of about 15 mbar, the sump temperature is of about 69 °C, the top temperature is of about 42 °C, and a mixture of methyl and ethyl substituted pyridine (such as MEP) and entrainer, such as morpholine, (20) is being removed from the entrainer-distillation column (9) via a condenser. Methyl and vinyl substituted pyridine (such as MVP) (21) is transferred into a wiped film evaporator (10) being attached to purification distillation column (15) having a pressure of about 15 mbar. The sump temperature is of about 70 °C, the boiling temperature is of about 69 °C, and methyl and vinyl substituted pyridine (such as MVP) (31) is being removed from purification distillation column (15) via a condenser. The residue (25) comprising e.g. divinyl compounds, oligomers, inhibitors, and / or sump dilution agents is being removed as the high boiling fraction.

[0120] List of reference numerals

[0121] I Polymerization inhibitor feed

[0122] 4 Dewatering distillation column

[0123] 6 methyl and vinyl substituted pyridine (such as MVP) crude feed

[0124] 8 Water removal

[0125] 9 Entrainer-distillation column

[0126] 10 Wiped film evaporator

[0127] I I Mixing point 13 methyl and vinyl substituted pyridine / a methyl and ethyl substituted pyridine (such as MVP / MEP) transfer

[0128] 14 Dividing point

[0129] 15 Purification distillation column

[0130] 20 Mixture of methyl and ethyl substituted pyridine (such as MEP) and entrainer removal

[0131] 21 methyl and vinyl substituted pyridine (such as MVP) transfer

[0132] 24 methyl and vinyl substituted pyridine (such as MVP) transfer

[0133] 25 Residue removal

[0134] 26 Entrainer feed

[0135] 27 methyl and vinyl substituted pyridine (such as MVP) transfer

[0136] 29 Sump of purification column

[0137] 30 Sump purge

[0138] 31 methyl and vinyl substituted pyridine (such as MVP) removal

[0139] 32 Sump recycle

[0140] The present invention will be further illustrated by the following examples.

[0141] Example 1 : 2-Picoline

[0142] A) At a vacuum of 15 mbar and a jacket temperature of 110 °C (for entrainer-distillation column (9)), 306 g of a 24% MVP crude solution (said crude solution further comprising MEP and water) was dewatered over the course of 60 min and with a reflux ratio of 1 :1 . Then MEP was removed by dosing 120 g 2-picoline as an organic entrainer into the sump of the column over the course of 195 min with reflux ratio of 1 .5 to 1 . After stopping the organic entrainer dosing, remaining organic entrainer was removed by continuing the distillation for further 45 min. 103 g of solution were obtained, containing 67% of MVP and 27% of MEP.

[0143] The distillate flow rate during organic entrainer distillation was about 67 g / h.

[0144] B) The sump solution obtained in 1 A) was further distilled leading to an MVP content in the sump of 88% MVP with a yield of about 60%.

[0145] C) The sump from 1 B) was worked up in a rotary evaporator, leading to a heavy fraction of solid byproducts of 2.6% of the original MVP crude solution applied in 1A). Example 2: Morpholine

[0146] A) At a vacuum of 15 mbar and a jacket temperature of 110 °C (for entrainer-distillation column (9)), 306 g of a 24% MVP crude solution (said crude solution further comprising MEP and water) was dewatered over the course of 60 min and with a reflux ratio of 1 :1 . Then MEP was removed by dosing 120 g morpholine as an organic entrainer into the sump of the column over the course of 195 min with reflux ratio of 1 .5 to 1 . After stopping the organic entrainer dosing, remaining organic entrainer was removed by continuing the distillation for further 45 min. 57 g of solution were obtained, containing 89% of MVP and 1% of MEP.

[0147] The distillate flow rate during organic entrainer distillation was about 78 g / h.

[0148] B) The sump from in 2A) was worked up in a rotary evaporator, leading to a heavy fraction of solid by-products of 1.6% of the original MVP crude solution applied in 2A).

[0149] Comparison of Example 1 (2-Picoline) with Example 2 (morpholine):

[0150] Example 2 has a higher distillate flow rate during organic entrainer distillation of 78 g / h compared to 67 g / h of Example 1 , applying identical jacket temperature of 110 °C and 15 mbar vacuum, which allows shorter distillation times.

[0151] Example 2, provides the desired quality of low MEP contents, while for Example 1 a further distillation was required.

[0152] Example 2 led to an MVP yield of about 70%. To reach a comparable quality of MVP, further distillation was required in the case of Example 1 , leading to a lower MVP yield of about 60%.

[0153] A final distillation of the solution led to less residue formation (1 .6% of feed mixture in the case of Example 2 and 2.6% in the case of Example 1).

Claims

Claims1 . A method for recovering a methyl and vinyl substituted pyridine from a mixture (M1 ) comprising the methyl and vinyl substituted pyridine and a methyl and ethyl substituted pyridine, the method comprising the steps of a) distilling the methyl and ethyl substituted pyridine from said mixture (M1) in the presence of an organic entrainer at a sump temperature of about 30 to about 100 °C and a pressure of about 5 to about 50 mbar providing a mixture (M2) comprising the methyl and vinyl substituted pyridine as high boiling fraction; and b) distilling the methyl and vinyl substituted pyridine from said mixture (M2) providing the methyl and vinyl substituted pyridine as light boiling fraction.

2. The method according to claim 1 , wherein the organic entrainer has a boiling point of about 110 to about 180 °C, preferably of about 115 to about 170 °C, more preferably of about 120 to about 140 °C, and in particular of about 125 to about 135 °C.

3. The method according to claim 1 or 2, wherein the organic entrainer is an alkanolamine and / or a heterocyclic compound (HC), preferably comprising at least one amine atom in the ring.

4. The method according to any one of claims 1 to 3, wherein the organic entrainer is a nonaromatic organic entrainer, preferably a non-aromatic heterocyclic compound.

5. The method according to any one of claims 1 to 4, wherein the organic entrainer is a compound of formula (1)whereinR1and R2are independently hydrogen, halogen, C1-C4-alkly, or C1-C4-haloalkly or wherein R1andR2represent =0;R3and R4are independently hydrogen, halogen, C1-C4-alkly, or C1-C4-haloalkly or wherein R3andR4represent =0;A1is O, NH, NRA, C=O, or CHRB;A2is O, NH, NRA, C=O, or CHRB;A3is O, NH, NRA, C=O, or CHRB;A4is O, NH, NRA, C=O, or CHRB;RAis C1-C3-alkly, or C1-C3-haloalkly;RBis hydrogen, halogen, C1-C3-alkly, or C1-C3-haloalkly; and wherein at least one of A1to A4is O, NH or NRA.

6. The method according to claim 5, whereinR1and R2are independently hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen;R3and R4are independently hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly or wherein R1and R2represent =0, preferably independently hydrogen or methyl; and in particular hydrogen;A1is O, NH, or NRA, preferably O or NH, and in particular O;A2is CH2 or CHRB, preferably CH2 or CH-CH3, and in particular CH2;A3is CH2 or CHRB, preferably CH2 or CH-CH3, and in particular CH2;A4is O, NH, or NRA, preferably NH or N-CH3, and in particular NH;RAis C1-C2-alkly or C1-C2-haloalkly, preferably methyl or trifluoromethyl, and in particular methyl; RBis hydrogen, halogen, C1-C2-alkly, or C1-C2-haloalkly, preferably hydrogen, methyl, or trifluoromethyl, and In particular hydrogen.

7. The method according to any one of claims 1 to 6, wherein the mixture (M1) comprises up to about 75 wt.-%, preferably about 10 to about 65 wt.-%, more preferably about 15 to about 55 wt.- %, and in particular about 20 to about 45 wt.-%, of the methyl and vinyl substituted pyridine based on the total amount of the mixture (M1).

8. The method according to any one of claims 1 to 7, wherein the methyl and vinyl substituted pyridine is 2-methyl-5-vinyl pyridine (MVP) and the methyl and ethyl substituted pyridine is 2-me- thyl-5-ethyl pyridine (MEP).

9. The method according to any one of claims 1 to 8, wherein step a) is performed at a sump temperature of about 40 to about 90 °C and a pressure of about 5 to about 40 mbar, preferably at a sump temperature of about 50 to about 80 °C and a pressure of about 5 to about 30 mbar, and in particular a sump temperature of about 65 to about 75 °C and a pressure of about 10 to about 20 mbar and / or step b) is performed at a sump temperature of about 40 to about 90 °C and a pressure of about 5 to about 40 mbar, preferably at a sump temperature of about 50 to about 80 °C and a pressure of about 5 to about 30 mbar, and in particular a sump temperature of about 65 to about 75 °C and a pressure of about 10 to about 20 mbar.

10. The method according to any one of claim 1 to 9, wherein the ratio of the organic entrainer related to the mixture (M1 ) is from about 0.02 to about 0.5 wt / wt, preferably from about 0.03 to about 0.4 wt / wt, and in particular from about 0.05 to about 0.35 wt / wt.11 . The method according to any one of claims 1 to 10, wherein the method comprises prior to distilling step a), a step a.i) distilling water from a mixture (M1.i) comprising the methyl and vinyl substituted pyridine, the methyl and ethyl substituted pyridine, and water, preferably at a sump temperature of about 40 to about 110 °C and a pressure of about 8 to about 60 mbar, more preferably at a sump temperature of about 50 to about 100 °C and a pressure of about 10 to about 55 mbar, still more preferably at a sump temperature of about 60 to about 90 °C and a pressure of about 20 to about 50 mbar, and in particular at a sump temperature of about 70 to about 85 °C and a pressure of about 25 to about 40 mbar, providing the mixture (M1) as high boiling fraction.

12. The method according to any one of claims 1 to 11 , wherein in distilling step a) a polymerization inhibitor is added, preferably wherein the polymerization inhibitor is selected from the group consisting of phenothiazine, benzoquinone dioxime, hydroquinone, tert-butyl catechol, and mixtures thereof and / or the polymerization inhibitor is provided as solution, preferably in 2-methyl-5-ethyl pyridine (MEP).

13. The method according to claim 12, wherein the polymerization inhibitor is added to the distillation sump or dosed at the top of a distillation column during the distillation.

14. The method according to any one of claims 1 to 13, wherein distillation step b) is performed in a wiped film evaporator being attached to a distillation column.

15. The method according to any one of claims 1 to 14, wherein the method further comprises collecting the light boiling fraction obtained in distilling step a) comprising the organic entrainer and the methyl and ethyl substituted pyridine, preferably wherein the organic entrainer and / or the methyl and ethyl substituted pyridine are recovered via distillation.

16. A methyl and vinyl substituted pyridine obtained by a method according to any one of claims 1 to 14, preferably wherein the methyl and vinyl substituted pyridine is 2-methyl-5-vinyl pyridine (MVP).

17. A methyl and ethyl substituted pyridine and / or an organic entrainer obtained by the method according to claim 15.

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