Process for preparation of acetonecketal acrylate by transesterification

Abstract

A process for the preparation of acetone ketal acrylate by transesterification of ethyl acrylate with acetone ketal, the process comprising the steps of: (i) in the presence of a catalyst comprising titanium (IV) or zirconium (IV) and a stabilizer, in the presence of ethyl acrylate forming an azeotropic mixture with ethanol as an entrainer, the invention relates to a method for producing ethyl acrylate, comprising the steps of (i) reacting ethyl acrylate with acetacetal, (ii) continuously distilling off and condensing an azeotropic mixture containing ethyl acrylate and ethanol by means of a distillation column operated under reflux conditions, in which steps (i) and (ii) are carried out simultaneously until a conversion of acetacetal of > = 95% is achieved, and (ii) continuously distilling off and condensing the azeotropic mixture containing ethyl acrylate and ethanol by means of a distillation column operated under reflux conditions, characterized in that step (ii) is carried out by diluting the condensed azeotropic mixture with additional ethyl acrylate and using the mixture as the reflux of the distillation column.

Description

[0001] The present invention relates to a process for preparing solketal acrylate by transesterification of solketal with ethyl acrylate.

[0002] Solvent acrylate ((2,2-dimethyl-1,3-dioxolan-4-yl)methyl acrylate, IPGA) is particularly useful as a reactive diluent in curable compositions such as printing inks, preferably inkjet printing inks. Solvent acrylate is an excellent monofunctional monomer acrylate with an outstanding performance profile in UV inkjet that is difficult to find for any commercially available monofunctional monomer acrylate. It combines very low viscosity as a pure substance with very high curing speed in UV inkjet ink formulations and very good adhesion on various substrates such as plastic films.

[0003] WO 2018 / 146258 describes the preparation of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl acrylate (propylene glycol acetone acetal, IPGA)

[0004]

[0005] Its preparation is as follows: in a 4L double jacket reactor with a column, a condenser, a reflux separator, an anchor stirrer and a lean air introduction, ethyl acrylate (2650 g), MeHQ (1.36 g), phenothiazine (136 mg) and acetone acetal (1250 g) are added. Tetraisopropoxytitanium (54 g) is added, lean air introduction is started, and the mixture is heated to a tank temperature of 86°C under a vacuum of 800 mbar. When the mixture begins to boil, a reflux ratio of 10:1 (reflux: distillate) is adjusted, which is adjusted during the reaction. When the vacuum is adjusted to 630 mbar, the tank temperature is increased to 104°C. After 5 h, the GC of the distillate shows an ethanol content of 0.7% (GC area %). 300 mL of water is added. After 30 min, water and ethyl acrylate are distilled off at a bath temperature of 80°C under a vacuum of 20 mbar. The product was obtained after filtration in a yield of 1670 g and 96% purity (GC area %).

[0006] CN106008447 also discloses a method for preparing acrylic acid ester of 2,2-dimethyl-1,3-dioxolane methanol (glycerol acetone acetal) by transesterification with methyl acrylate in the presence of an organic titanium or organic tin catalyst (such as tetrabutyl titanate, butyl titanate, tetraisopropyl titanate, dibutyltin dilaurate, dibutyltin dichloride, tributyltin acetate, dibutyltin oxide and tributyltin chloride).

[0007] An object of the present invention is to provide a process for preparing glycerol acetonate by transesterification of ethyl acrylate with glycerol acetonate ((2,2-dimethyl-1,3-dioxolan-4-yl)methanol), wherein the reaction time or the batch time is minimized.

[0008] This object is achieved by a method for preparing glycerol acetonide by transesterifying ethyl acrylate with glycerol acetonide, the method comprising the following steps:

[0009] (i) reacting ethyl acrylate with glycerol acetone acetal in the presence of a catalyst containing titanium (IV) or zirconium (IV) and a stabilizer and in the presence of ethyl acrylate which forms an azeotropic mixture with ethanol as an azeotropic agent,

[0010] (ii) continuously distilling off and condensing an azeotropic mixture containing ethyl acrylate and ethanol through a distillation column operated under reflux conditions,

[0011] wherein steps (i) and (ii) are carried out simultaneously until a conversion rate of glycerol acetone acetal of ≥ 95% is achieved,

[0012] Characterized in that step (ii) is carried out by diluting the condensed azeotropic mixture with additional ethyl acrylate and using the mixture as reflux of the distillation column.

[0013] Surprisingly, it has been found that the reaction time can be significantly shortened by diluting the condensed azeotropic mixture containing ethyl acrylate and ethanol with substantially pure ethyl acrylate and using this mixture as reflux for the column as soon as the reaction mixture starts to boil and condensing and removing the distillate containing ethyl acrylate and ethanol at the top of the column. In the context of the present invention, substantially pure means that the ethyl acrylate has a purity of at least 98 wt.%.

[0014] Substantially pure ethyl acrylate may contain up to 2 wt.% ethanol.

[0015] In a preferred embodiment, diluting the condensed azeotropic mixture with ethyl acrylate is performed by pre-filling a distillate collection container with ethyl acrylate and mixing the condensed azeotropic mixture discharged from the top of the distillation column with ethyl acrylate in the container. In this way, the condensed azeotropic mixture is continuously diluted with ethyl acrylate before being returned to the top of the distillation column as reflux.

[0016] Typically, when carrying out steps (i) and (ii), the ethanol content in the reflux is in the range of 10 wt.% and 30 wt.%.

[0017] Typically, the reflux ratio of reflux:distillate in the distillation column is from 10:1 to 2:1, preferably from 10:2 to 3:1, more preferably from 4:1 to 2:1.

[0018] The reaction of ethyl acrylate with glycerol acetonate is carried out in the presence of a catalyst comprising titanium (IV) or zirconium (IV). Suitable catalysts comprising titanium (IV) or zirconium (IV) are titanium (IV) and zirconium (IV) tetraalkoxides of linear or branched C1-C6 alcohols, preferably tetraethanolates, tetraisopropoxides, tetrabutoxides and metalates of the reactant alcohol used or mixtures thereof. Metalates substituted by different alcohols or acetylacetone are also possible.

[0019] The reaction of ethyl acrylate with glycerol acetonate is additionally carried out in the presence of one or more stabilizers (polymerization inhibitors). Examples of suitable stabilizers are N-oxides (nitroxyl or N-oxyl radicals, i.e. compounds carrying at least one NO group), for example 4-hydroxy-2,2,6,6-tetramethylpiperidinyl N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidinyl N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidinyl N-oxyl, 2,2,6,6-tetramethylpiperidinyl N-oxyl, bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate, 4,4′,4″-tris(2,2,6,6-tetramethylpiperidinyl N-oxyl)phosphite or 3-oxo-2,2,5,5-tetramethylpiperidinyl N-oxyl. Methylpyrrolidine N-oxyl; mono- or polyhydric phenols which may carry one or more alkyl groups, for example alkylphenols such as o-, m- or p-cresol (methylphenol), 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 2-tert-butyl-4-methylphenol, 2,6-tert-butyl-4-methylphenol, 4-tert-butyl-2,6-dimethylphenol or 6-tert-butyl-2,4-dimethylphenol; quinones such as hydroquinone, hydroquinone monomethyl ether, 2-methylhydroquinone or 2,5-di-tert-butylhydroquinone; hydroxyphenols such as catechol (1,2-dihydroxybenzene) or benzoquinone; aminophenols , for example p-aminophenol; nitrosophenols, for example p-nitrosophenol; alkoxyphenols, for example 2-methoxyphenol (guaiacol, catechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-tert-butyl-4-methoxyphenol; tocopherols, for example α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), aromatic amines, for example N,N-diphenylamine or N-nitrosodiphenylamine; phenylenediamines, for example N,N'-dialkyl-p-phenylenediamine, wherein the alkyl radicals may be identical or different and each Each of the compounds independently consists of 1 to 4 carbon atoms and may be straight-chain or branched, for example N,N'-dimethyl-p-phenylenediamine or N,N'-diethyl-p-phenylenediamine, a hydroxylamine, for example N,N-diethylhydroxylamine, an imine, for example methylethylimine or methylene violet, a sulfonamide, for example N-methyl-4-toluenesulfonamide or N-tert-butyl-4-toluenesulfonamide, an oxime, such as an aldoxime, a ketoxime or an amideoxime, for example diethylketoxime, methylethylketoxime or salicylaldehydeoxime, a phosphorus compound, for example triphenylphosphine, triphenyl phosphite, triethyl phosphite, hypophosphorous acid or an alkyl ester of phosphorous acid; a sulfur compound, for example diphenyl sulfide or phenothiazine, or a mixture thereof.

[0020] Preferred are hydroquinone, hydroquinone monomethyl ether, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidinyl N-oxyl, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol and 2-methyl-4-tert-butylphenol and phenothiazine.

[0021] Particularly preferred are hydroquinone monomethyl ether (MeHQ), phenothiazine (PTZ) and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl N-oxyl (HO-TEMPO).

[0022] Advantageously, oxygen can additionally serve as polymerization inhibitor.

[0023] For further stabilization, an oxygen-containing gas, preferably air or a mixture of air and nitrogen (lean air), may be present.

[0024] The transesterification reaction (steps (i) and (ii)) is generally carried out at a temperature of 60 to 120° C., preferably 70 to 110° C. During this process, an azeotropic mixture of ethyl acrylate and ethanol is continuously distilled off.

[0025] Typically, ethyl acrylate is used in a stoichiometric excess. Preferably, the excess of ethyl acrylate per solketal to be esterified is up to 300 wt.%, more preferably up to 200 wt.% and in particular from 110 to 150 wt.%.

[0026] The catalyst is used in a concentration of 0.1 to 10 mol-%, preferably 0.1 to 5 mol-%, based on the amount of solketal used.

[0027] The transesterification in steps (i) and (ii) can be carried out under atmospheric pressure, but can also be carried out under high pressure or reduced pressure. Typically, the transesterification is carried out at 100 to 1000 mbar, preferably 300-800 mbar (atmospheric pressure = 1000 mbar). The reaction time is typically 5 to 120 hours, preferably 12 to 48 hours.

[0028] Most preferably, steps (i) and (ii) are carried out at a pressure of from 400 to 600 mbar (absolute) and a temperature of from 80°C to 105°C.

[0029] The reaction can be carried out in all reactors suitable for this type of reaction. Such reactors are known to those skilled in the art. The reaction is preferably carried out in a stirred tank reactor.

[0030] Any desired means, such as stirring means, can be used to mix the batch. Mixing can also be carried out by feeding in a gas, preferably an oxygen-containing gas.

[0031] The reactor can then be supplemented with ethyl acrylate as an azeotropic agent. For this purpose, the azeotropic mixture of ethyl acrylate and ethanol that is distilled out is stirred with water in a mixing vessel and then transferred to a phase separator, wherein the ethanol is dissolved in water and the organic phase is separated as the upper layer. The organic phase can be returned to the reaction mixture. Alternatively, fresh ethyl acrylate can also be added and the ethyl acrylate / ethanol mixture can be post-processed in a separate step, or the supplement of ethyl acrylate can be completely or partially omitted.

[0032] In one embodiment, ethanol is removed from the azeotropic mixture of ethyl acrylate and ethanol distilled in step (ii) by washing with water. The ethyl acrylate may be recycled to the reaction vessel.

[0033] Steps (i) and (ii) are carried out until the solketal used has been converted into acrylic acid ester to an extent of at least 95%, preferably to an extent of at least 97%.

[0034] Preferably, the method of the present invention further comprises step (iii):

[0035] (iii) when a solacetone conversion of ≥ 95% is achieved, evaporating unreacted ethyl acrylate from the product mixture under evaporation conditions.

[0036] In particular, step (iii) is performed when a solacetone conversion of ≥ 97% is achieved.

[0037] Preferably, step (iii) is carried out at a pressure of from 10 to 500 mbar and at a temperature of from 60°C to 100°C.

[0038] Preferably, the method of the present invention comprises the additional step (iv):

[0039] (iv) stripping the remaining ethyl acrylate from the product mixture with a gas stream.

[0040] The gas stream used in step (iv) may be an inert gas stream such as a nitrogen stream, or an oxygen-containing gas stream such as an air stream.

[0041] Preferably, step (iv) is carried out until the concentration of ethyl acrylate in the product mixture is ≤ 200 ppm.

[0042] The product mixture comprising acrylate acetonate and catalyst can be worked up further by subsequent steps (v) to (vii):

[0043] (v) adding water to a product mixture comprising acrylate acetonide and the catalyst,

[0044] (vi) distilling water from the product mixture,

[0045] (vii) Removal of hydrolysis products of catalysts containing titanium (IV) or zirconium (IV).

[0046] Step (vii) may also be performed before step (vi). Step (v) may also be performed before step (iii). Then, step (vi) may be performed together with step (iii). Alternatively, steps (v) and (vi) may also be performed before step (iv).

[0047] The distillation (vi) is generally carried out at a temperature of 40 to 100° C., preferably 60 to 100° C., and a variable pressure of 2 to 700 mbar. The distillative removal can be carried out, for example, under reduced pressure in a stirred tank with jacket heating coils and / or internal heating coils.

[0048] In step (vii), the sparingly soluble hydrolysate is removed, for example by filtration or centrifugation.

[0049] Filtration can be carried out, for example, with a pressure filter. In process engineering terms, for the filtration in the method of the invention, any filtering methods and devices known per se can be used, such as those described in Ullmann's Encyclopedia of Industrial Chemistry, 7th ed., 2013 Electronic Release, chapter: Filtration, 1. Fundamentals and Filtration 2. Equipment. For example, these can be cartridge filters, filter presses, plate filters, bag filters or drum filters. Preferably, cartridge filters or plate filters are used. Filtration can be carried out with or without filter aids. Suitable filter aids are filter aids based on diatomaceous earth, perlite and cellulose.

[0050] Suitable centrifuges and separators are known to the expert. In process engineering terms, for the centrifugation in the process according to the invention, any centrifugation methods and apparatuses known per se can be used, for example those described in Ullmann's Encyclopedia of Industrial Chemistry, 7th ed., 2013 Electronic Release, chapter: Centrifuges, Filtering and Centrifuges, Sedimenting.

[0051] The present invention is described more specifically by the following examples.

[0052] Examples

[0053] Simulation study

[0054] All process simulation studies were performed with CHEMADIS, a discontinuous process flowsheet simulation tool from BASF SE. This simulation tool is based on a publicly available database of physical properties and uses well-established thermodynamic models based on its own measurements to predict transient behavior over time. Reaction kinetic models were derived from laboratory experiments and also integrated into the process simulations.

[0055] Example 1

[0056] In a 14m2 reactor with a three-stage cross-arm agitator, a column with 10 theoretical stages (Koch-Glitsch IMTP25 random packing), a condenser, a reflux pump, a reflux separator, a distillate drum, a vacuum system and an air introduction system were installed on the top. 3In a semi-coil jacketed reactor of 1000 g / cm2, solketal (3322 kg), ethyl acrylate (2200 kg stabilized with 1250 ppm MEHQ and 4386 kg stabilized with 15 ppm MEHQ) and 464 kg of an internal recycle stream (50 wt.-% ethyl acrylate, the remainder ethanol) were added. Tetraisopropoxytitanium (88 kg) was added, air introduction was started and the mixture was heated to a tank temperature of 85° C. with 1.5 bar gauge steam under a vacuum of 600 mbar. The distillate drum was pre-filled with 2500 kg of ethyl acrylate stabilized with 15 ppm MEHQ and when the mixture started to boil (t=0 h), the reflux ratio (reflux:distillate) was adjusted to 4. When the tank temperature reached 97° C., the vacuum was continuously reduced to keep the tank temperature constant at 97° C. When the solketal conversion in the tank reached >98% (t=30 h), the reflux was set to 0 and the remaining ethyl acrylate was evaporated. When the vacuum reached <40 mbar (t=32 h), evaporation was stopped by stopping the steam supply and increasing the air flow rate continuously to 8.5 Nm 3 / h to strip the remaining ethyl acrylate from the storage tank. When the storage tank concentration shows an ethyl acrylate concentration of <100 ppm, the stripping is ended and the reactor is cooled with cooling water in the jacket. The crude product is obtained with a yield of 4416 kg and a purity of 97%. The unconverted excess ethyl acrylate (which is pre-filled in the distillate drum) can be used in other processes, where impurities like isopropyl alcohol are also removed.

[0057] Example 2

[0058] In a 14m2 reactor with a three-stage cross-arm agitator, a column with 10 theoretical stages (Koch-Glitsch IMTP25 random packing), a condenser, a reflux pump, a reflux separator, a distillate drum, a vacuum system and an air introduction system were installed on the top. 3In a semi-coil jacketed reactor of 1000 g / cm2, solketal (3322 kg), ethyl acrylate (2200 kg stabilized with 1250 ppm MEHQ and 4386 kg stabilized with 15 ppm MEHQ) and 464 kg of an internal recycle stream (50 wt.-% ethyl acrylate, the remainder ethanol) were added. Tetraisopropoxytitanium (88 kg) was added, air introduction was started and the mixture was heated to a tank temperature of 85° C. with 1.5 bar gauge steam under a vacuum of 600 mbar. The distillate drum was not prefilled and when the mixture began to boil (t=0 h), the reflux ratio (reflux:distillate) was adjusted to 4. When the tank temperature reached 97° C., the vacuum was continuously reduced to keep the tank temperature constant at 97° C. When the solketal conversion in the tank reached >98% (t=35 h), the reflux was set to 0 and the remaining ethyl acrylate was evaporated. When the vacuum reached <40 mbar (t=37 h), evaporation was stopped by stopping the steam supply and increasing the air flow rate continuously to 8.5 Nm 3 / h to strip the remaining ethyl acrylate from the storage tank. When the storage tank concentration showed an ethyl acrylate concentration of <100 ppm, the stripping was completed and the reactor was cooled with cooling water in the jacket. The same amount of crude product was obtained with a purity of 97% in 5 hours more than in the preferred example 1.

[0059] Example 3

[0060] In a 14m2 reactor with a three-stage cross-arm agitator, a column with 10 theoretical stages (Koch-Glitsch IMTP25 random packing), a condenser, a reflux pump, a reflux separator, a distillate drum, a vacuum system and an air introduction system were installed on the top. 3 In a semi-coil jacketed reactor of 1000 g / cm2, solketal (3322 kg), ethyl acrylate (2200 kg stabilized with 1250 ppm MEHQ and 4386 kg stabilized with 15 ppm MEHQ) and 464 kg of an internal recycle stream (50 wt.-% ethyl acrylate, the remainder ethanol) were added. Tetraisopropoxytitanium (88 kg) was added, air introduction was started and the mixture was heated to a tank temperature of 85° C. with 1.5 bar gauge steam under a vacuum of 600 mbar. The distillate drum was not prefilled and when the mixture began to boil (t=0 h), the reflux ratio (reflux:distillate) was adjusted to 4. When the tank temperature reached 97° C., the vacuum was continuously reduced to keep the tank temperature constant at 97° C. When the solketal conversion in the tank reached >98% (t=35 h), the reflux ratio was kept constant at 4 and the remaining ethyl acrylate was removed in distillation mode. When the vacuum reached <40 mbar (t=48 h), the reflux was set to 0, the steam supply was stopped, and the air flow was continuously increased to 8.5 Nm 3 / h to strip the remaining ethyl acrylate from the storage tank. When the storage tank concentration showed an ethyl acrylate concentration of <100 ppm, the stripping was ended and the reactor was cooled with cooling water in the jacket. The crude product was obtained in 11 hours more than in Example 2 with a yield of 4520 kg and a purity of 98%. Although the yield was about 100 kg / batch higher due to the distillation mode, the annual output was much lower due to the significantly higher batch time.

[0061] Example 4

[0062] Ethyl acrylate (2000 g), ethyl acrylate ethanol azeotrope (190 g), MeHQ (1.27 g) and acetone acetal (1000 g) were added to a 4 L double jacket reactor equipped with a column (Montz A3-750 packing) on ​​top, a cooler, a reflux separator, a three-stage cross-arm agitator and lean air introduction. The mixture was heated to a tank temperature of 85° C. at 600 mbar with lean air introduction and titanium tetraisopropoxide (11.1 g) was added while stirring during heating.

[0063] After the start of boiling, the azeotropic mixture of ethyl acrylate and ethanol was continuously distilled off at a reflux ratio of 10: 1, which was adjusted during the reaction. During the reaction, the storage tank temperature was increased to 100° C., wherein the vacuum was adjusted down to 500 mbar. Distillate and storage tank samples were taken regularly to monitor the reaction process. In order to accelerate the reaction, catalyst (a total of 15.5 g) was gradually added during the reaction. After 11.5 h of distillation, the yield was >98%.

[0064] 250 ml of water were added to the reaction mixture, stirred at a bath temperature of 75° C. for 1 h, and then water and ethyl acrylate were distilled off. During the distillation, the pressure was reduced to 12 mbar.

[0065] 44 g of filter aid Harbolite 900 was added to the reaction mixture and filtered through a filter press.

[0066] After filtration, the product was obtained in a yield of 1161 g with a purity of 96.3 GC area %.

[0067] Example 5

[0068] Ethyl acrylate (2502 g), MeHQ (1.38 g) and acetone glycerol (1035 g) were added to a 4L double-jacketed reactor equipped with a tower (Montz A3-750 packing), a cooler, a reflux separator, a three-stage cross-arm agitator and air introduction at the top. At 300 mbar, the mixture was heated to a tank temperature of 70°C with air introduction, and 443 g of ethyl acrylate was distilled out. At 600 mbar, the tank temperature was raised to 90°C, and titanium tetraethoxide (9.8 g) was added during heating. Subsequently, an azeotropic mixture of ethyl acrylate and ethanol was distilled out, starting with a reflux ratio of 10:3. The reflux ratio was adjusted during the reaction. During the reaction, the tank temperature was raised to 95°C, where the vacuum was adjusted to 500 mbar. Distillate and tank samples were taken regularly to monitor the reaction process. In order to accelerate the reaction, a catalyst (13.1 g in total) was gradually added during the reaction. After distillation for 9.5 h, the yield was >98%. 260 ml of water were added to the reaction mixture, stirred at a temperature of 80° C. for 1 h, and then water and ethyl acrylate were distilled off. During the distillation, the pressure was reduced to 15 mbar. 46 g of filter aid Harbolite 900 were added to the reaction mixture,

[0069] And filtered through a filter press.

[0070] After filtration, the product was obtained in a yield of 1247 g with a purity of 95.8 GC area %.

[0071] Example 6

[0072] Ethyl acrylate (2000 g), ethyl acrylate ethanol azeotropic mixture (190 g) from previous experiments, MeHQ (1.27 g) and acetone acetal (1000 g) were added to a 4L double-jacketed reactor equipped with a tower (Montz A3-750 packing), a cooler, a reflux separator, a three-stage cross-arm agitator and air introduction at the top. The mixture was heated to a tank temperature of 86° C. at 600 mbar with air introduction, and titanium tetraethoxide (10.4 g) was added while stirring during heating. After the start of boiling, the azeotropic mixture of ethyl acrylate and ethanol was continuously distilled out at a reflux ratio of 10:2, which was adjusted during the reaction. During the reaction, the tank temperature was raised to 94° C., where the vacuum was adjusted to 500 mbar. Distillate and tank samples were taken regularly to monitor the reaction process. In order to accelerate the reaction, catalyst (11.7 g in total) was gradually added during the reaction. After distillation for 10 h, the yield was >98%. At a temperature of 80° C.-100° C., the pressure is slowly reduced to 40 mbar and ethyl acrylate is distilled off. The temperature is then maintained at 80° C. for a further 5 h while introducing 2-8 L / h of air until the concentration of ethyl acrylate in the solution is <0.01% (controlled by gas chromatography). 250 ml of water are added to the reaction mixture, stirred at a temperature of 75° C. for 1 h, and then the water is distilled off. During the distillation, the pressure is reduced to 12 mbar. 44 g of filter aid Harbolite 900 are added to the reaction mixture and filtered through a filter press.

[0073] After filtration, the product was obtained in a yield of 1204 g with a purity of 96.0 GC area %.

Claims

1. A method for preparing glyceryl acetonide by transesterifying ethyl acrylate with glyceryl acetonide, the method comprising the following steps: (i) reacting ethyl acrylate with glycerol acetone acetal in the presence of a catalyst containing titanium (IV) or zirconium (IV) and a stabilizer and in the presence of ethyl acrylate which forms an azeotropic mixture with ethanol as an azeotropic agent, (ii) continuously distilling off and condensing an azeotropic mixture containing ethyl acrylate and ethanol through a distillation column operated under reflux conditions, wherein steps (i) and (ii) are carried out simultaneously until a conversion rate of glycerol acetone acetal of ≥ 95% is achieved, Characterized in that step (ii) is carried out by diluting the condensed azeotropic mixture with additional ethyl acrylate and using the mixture as reflux of the distillation column.

2. The method of claim 1, wherein: When carrying out steps (i) and (ii), the ethanol content of the reflux is in the range of 10 to 30 wt.%.

3. The method according to claim 1 or 2, wherein: The reflux ratio of reflux:distillate in the distillation column is 10:1 to 2:

1.

4. The method according to any one of claims 1 to 3, wherein: Steps (i) and (ii) are carried out at a pressure of 400 to 600 mbar and a temperature of 80°C to 105°C.

5. The method according to any one of claims 1 to 4, comprising step (iii): (iii) when a solacetone conversion of ≥ 95% is achieved, evaporating unreacted ethyl acrylate from the product mixture under evaporation conditions.

6. The method of claim 5, wherein: When a solacetone conversion of ≥ 97% is reached, step (iii) is carried out.

7. The method according to claim 5 or 6, wherein: Step (iii) is carried out at a pressure of 10 to 500 mbar and a temperature of 60°C to 100°C.

8. The method according to any one of claims 1 to 7, comprising step (iv): (iv) stripping the remaining ethyl acrylate from the product mixture with a gas stream.

9. The method of claim 8, wherein: Step (iv) is carried out until the ethyl acrylate concentration of the product mixture is ≤ 200 ppm.

10. The method according to any one of claims 1 to 9, comprising steps (v) to (vii): (v) adding water to a product mixture comprising acrylate acetonide and the catalyst, (vi) distilling water from the product mixture, (vii) removing the hydrolysis product of the catalyst comprising titanium(IV) or zirconium(IV), Wherein step (vii) may also be performed before step (vi).

11. The method of any one of claims 1 to 9, comprising steps (v) to (vii): (v) adding water to a product mixture comprising acrylate acetonide and the catalyst, (vi) distilling water from the product mixture, (vii) removing the hydrolysis product of the catalyst comprising titanium(IV) or zirconium(IV), wherein step (v) is performed before step (iii).

12. The method of claim 11, wherein: Step (vi) is performed together with step (iii).

13. The method of claim 8 or 9, comprising steps (v) to (vii): (v) adding water to a product mixture comprising acrylate acetonide and the catalyst, (vi) distilling water from the product mixture, (vii) removing the hydrolysis product of the catalyst comprising titanium(IV) or zirconium(IV), wherein step (v) and step (vi) are performed before step (iv).

14. The method according to any one of claims 1 to 13, wherein: The catalyst comprises titanium(IV) tetraisopropoxide.

15. The method according to any one of claims 1 to 14, wherein: The stabilizer is selected from hydroquinone monomethyl ether and phenothiazine.

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