Method for producing glycerin acetal and / or glycerin ketal

Abstract

The objective is to provide a method for efficiently producing high-purity five-membered ring glycerin acetal (ketal) using milder distillation conditions by performing simple post-treatment on the crude reaction solution after the acetalization (ketalization) reaction. [Solution] A method for producing glycerin acetal and / or glycerin ketal, comprising a reaction step of reacting glycerin with a specific carbonyl compound to obtain a crude reaction solution containing glycerin acetal of formula (1), and a distillation step of distilling and purifying the crude reaction solution to obtain glycerin acetal and / or glycerin ketal (1). JPEG2026106440000023.jpg2952

Description

Technical Field

[0001] The present invention relates to a method for producing glycerin acetal and / or glycerin ketal (hereinafter also referred to as "glycerin acetal (ketal)"). More specifically, the present invention relates to a method for producing glycerin acetal (ketal), which includes reacting glycerin with a carbonyl compound and distilling the obtained crude reaction solution.

Background Art

[0002] Glycerin acetal (ketal) such as solketal is used not only as an additive for gasoline and diesel fuel and a plasticizer for polymers but also, because of its non-toxicity, as a raw material for pharmaceutical intermediates and a solvent for perfumes, etc., in many applications. However, in applications such as raw materials for pharmaceutical intermediates and perfume solvents, glycerin acetal (ketal) with extremely reduced impurity content, that is, high-purity glycerin acetal (ketal), is required from the viewpoint of toxicity to the human body.

[0003] As an industrial production method of glycerin acetal (ketal), a method of reacting glycerin with a carbonyl compound such as acetone in the presence of an acid catalyst to obtain glycerin acetal (ketal) is known. As acid catalysts used for reacting glycerin with a carbonyl compound to produce glycerin acetal (ketal), homogeneous catalysts such as p-toluenesulfonic acid, hydrochloric acid, and sulfuric acid, and heterogeneous catalysts such as porous silica, ion exchange resin, and zeolite are known.

[0004] As homogeneous catalysts, for example, Patent Document 1 discloses a technique using p-toluenesulfonic acid. Non-Patent Document 2 also discloses a technique in which hydrogen chloride is used as an acid catalyst, glycerin and acetone are reacted, and then neutralization treatment is performed with lead carbonate and silver carbonate, and treatment with excessive calcium chloride is performed to obtain glycerin acetal (ketal).

[0005] As an example of a heterogeneous catalyst, Patent Document 2 discloses a technique using an acidic ion exchange resin. Non-Patent Document 1 discloses a technique using a protonated H-BEA type zeolite.

[0006] Furthermore, when glycerin and acetone are reacted using an acid catalyst, it is known that two isomers of glycerin acetal (ketal) are produced as by-products: 2,2-dimethyl-1,3-dioxolane-4-methanol with a five-membered ring structure and 2,2-dimethyl-1,3-dioxan-5-ol with a six-membered ring structure. Non-patent document 4 describes a technique for obtaining 2,2-dimethyl-1,3-dioxolane-4-methanol with high selectivity by using a hierarchical zeolite.

[0007] Furthermore, regarding methods for using basic substances, Patent Document 1 and Non-Patent Document 3 disclose a technique of adding acetate to the crude reaction solution. However, the techniques disclosed in these documents all involve adding an excess amount of basic catalyst to the acid catalyst, and are aimed at improving the reaction conversion rate of glycerin. Moreover, Patent Document 3 discloses that by adding an aqueous sodium hydroxide solution to glycerin acetal that has been stored in air for several months after distillation purification, and then further distilling and purifying it, an alkoxide compound with improved color can be obtained. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2006-273750 [Patent Document 2] Japanese Patent Application Publication No. 60-87282 [Patent Document 3] Japanese Patent Publication No. 2003-231686 [Non-patent literature]

[0009] [Non-Patent Document 1] Ind.Eng.Chem.Res.,Vol.56,p479-488(2017). [Non-Patent Document 2] J.Chem.Soc.,Vol.107, p337-350(1915). [Non-Patent Document 3] Organic Syntheses Collective.,Vol.3, p502-504(1955). [Non-Patent Document 4] J.Mol.Catal.A:Chem.,Vol.426,p205-212(2017). [Overview of the project] [Problems that the invention aims to solve]

[0010] In the presence of the aforementioned acid catalyst, the acetalization (ketalization) reaction takes place, producing glycerin acetal (ketal) from glycerin and a carbonyl compound such as acetone. However, in the technologies disclosed in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2, this acetalization (ketalization) reaction produces a glycerin acetal (ketal) having a five-membered ring structure represented by the following general formula (1) (hereinafter referred to as "five-membered ring glycerin acetal (ketal)"), and also produces a small amount of glycerin acetal (ketal) having a six-membered ring structure represented by the following general formula (3) (hereinafter referred to as "six-membered ring glycerin acetal (ketal)") as a by-product. [ka] [ka] (In formulas (1) and (3), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.)

[0011] However, the above-mentioned five-membered ring glycerin acetal (ketal) and six-membered ring glycerin acetal (ketal) have very close boiling points, so it is difficult to effectively separate them using a distillation purification method, and there is a problem that it is difficult to obtain a high-purity five-membered ring glycerin acetal (ketal). Specifically, in order to increase the purity of the five-membered ring glycerin acetal (ketal), increasing the number of distillation stages and the reflux ratio increases the consumption of equipment and energy used in distillation. Due to the influence of the heat history, the decomposition of the five-membered ring glycerin acetal (ketal) progresses, and the six-membered ring glycerin acetal (ketal) is generated. As a result, there is a problem that the purity of the finally obtained five-membered ring glycerin acetal (ketal) decreases.

[0012] Also, the above-mentioned acetalization (ketalization) reaction is an equilibrium reaction. Usually, by adding the carbonyl compound in excess relative to the charged molar amount of glycerin and reacting, the conversion rate of glycerin is improved. And the unreacted carbonyl compound usually needs to be removed using a distillation purification method.

[0013] However, in the technologies disclosed in Patent Documents 1 and 2, Non-Patent Documents 1 and 2, since an acid component remains in the crude reaction solution after the acetalization reaction, when distilling off the unreacted carbonyl compound, the five-membered ring glycerin acetal (ketal) reacts with the water in the system and decomposes into the carbonyl compound and glycerin, which are the starting materials, and these decomposition products cause a decrease in the purity of the five-membered ring glycerin acetal (ketal). In the technology disclosed in Patent Document 3, it is possible to separate the coloring precursor generated during the storage of glycerin acetal (ketal) by distillation, but there is a problem that this coloring precursor causes a decrease in the purity of the five-membered ring glycerin acetal (ketal) due to heating under highly basic conditions. Also, in the technology disclosed in Non-Patent Document 1, it is necessary to separate and remove zeolite from the reaction solution after the reaction, and an increase in the production cost related to this separation and removal treatment is a problem. In addition, in the technique disclosed in Non-Patent Document 2, it is necessary to separate and remove lead carbonate from the reaction solution after the reaction, and an increase in production cost associated with this separation and removal process has been a problem.

[0014] An object of the present invention is to solve the above problems. That is, the present invention solves the problems of the above-mentioned conventional technology, and by performing a simple post-treatment on the crude reaction solution after the acetalization (ketalization) reaction, a high-purity 5-membered cyclic glycerin acetal (ketal) can be obtained using milder distillation conditions. It is an object of the present invention to provide a method for producing a 5-membered cyclic glycerin acetal (ketal) that enables efficient production.

Means for Solving the Problems

[0015] As a result of intensive studies to solve the above problems, the present inventor has found that in the bottom residue obtained in the distillation step, the molar ratio of the 6-membered cyclic glycerin acetal (ketal) to the 5-membered cyclic glycerin acetal (ketal) is within a predetermined numerical range. By adjusting the pH of the crude reaction solution after the acetal reaction within a predetermined numerical range and performing distillation purification, it has been found that the amount of 6-membered cyclic glycerin acetal (ketal) generated due to the decomposition of the 5-membered cyclic glycerin acetal (ketal) during distillation can be suppressed. Alternatively, the present inventor has found that in the distillation step, by subjecting the crude reaction solution after the acetal reaction to distillation purification in the presence of an acid and a basic substance, the amount of 6-membered cyclic glycerin acetal (ketal) generated due to the decomposition of the 5-membered cyclic glycerin acetal (ketal) during distillation can be suppressed. As a result, it has been found that distillation conditions with less heat history can be used, and high-purity 5-membered cyclic glycerin acetal (ketal) can be efficiently produced, leading to the present invention.

[0016] The present invention has been achieved based on such findings, and the gist is as follows. [1] A method for producing glycerin acetal and / or glycerin ketal, comprising: a reaction step of reacting glycerin with a carbonyl compound represented by the following general formula (2) to obtain a crude reaction solution containing glycerin acetal and / or glycerin ketal (1) represented by the following general formula (1); and a distillation step of distilling and purifying the crude reaction solution to obtain glycerin acetal and / or glycerin ketal (1), wherein the pH of the crude reaction solution in the reaction step is controlled to be within a predetermined range so that the molar ratio of compound (3) represented by the following general formula (3) to glycerin acetal and / or glycerin ketal (1) in the kettle residue obtained in the distillation step is within a predetermined range. [ka] [In formula (2), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.] [ka] [In equation (1), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.] [ka] [In equation (3), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.] [2] The method for producing glycerin acetal and / or glycerin ketal according to [1], comprising distilling and purifying the crude reaction solution in the distillation step to distill off unreacted carbonyl compounds and obtain a boiler residue containing glycerin acetal and / or glycerin ketal (1). [3] A method for producing glycerin acetal and / or glycerin ketal according to [1] or [2], comprising controlling the pH of the crude reaction solution in the reaction step to be within a predetermined range such that the molar ratio of the compound represented by general formula (3) to the glycerin acetal and / or glycerin ketal (1) in the still residue obtained in the distillation step is within a range of 0 to 0.03. [4] The method for producing glycerin acetal and / or glycerin ketal according to [3], wherein the reaction step includes adding a basic substance to the crude reaction solution to control the pH of the crude reaction solution within a predetermined range. [5] A method for producing glycerin acetal and / or glycerin ketal according to [4], wherein the basic substance comprises an anion exchange resin. [6] A method for producing glycerin acetal and / or glycerin ketal according to [1] to [5], comprising controlling the pH of the crude reaction solution subjected to the distillation step to within the range of 7.00 to 10.00. [7] A method for producing glycerin acetal and / or glycerin ketal according to [1] to [6], comprising controlling the pH of the crude reaction solution subjected to the distillation step to within the range of 7.60 to 9.00. [8] A method for producing glycerin acetal and / or glycerin ketal according to [1] to [7], wherein the reaction step involves carrying out the reaction of glycerin with a carbonyl compound in the presence of an acid. [9] A reaction step in which glycerin is reacted with a carbonyl compound represented by the following general formula (2) in the presence of an acid to obtain a crude reaction solution containing glycerin acetal and / or glycerin ketal (1) represented by the following general formula (1), A method for producing glycerin acetal and / or glycerin ketal, comprising a distillation step of distilling the crude reaction solution in the presence of an acid and a basic substance to obtain glycerin acetal and / or glycerin ketal (1). [ka] [In formula (2), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.] [ka] [In equation (1), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.]

[10] The method for producing glycerin acetal and / or glycerin ketal according to [9], wherein the pH of the crude reaction solution in the reaction step is in the range of 7.00 to 10.00. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a method for producing a five-membered ring glycerin acetal (ketal) that allows for simple post-treatment of the crude reaction solution after the acetalization (ketalization) reaction, does not require complicated operations such as separation and removal of zeolite and lead carbonate as in conventional methods, and furthermore, enables the efficient production of high-purity five-membered ring glycerin acetal (ketal). Therefore, the manufacturing method of the present invention is superior to conventional methods in terms of manufacturing costs related to the post-treatment of the crude reaction solution after the acetalization (ketalization) reaction, as well as in terms of safety and workability during operation, and is therefore suitable for industrialization. Furthermore, the five-membered ring glycerin acetal (ketal) obtained by the manufacturing method of the present invention has a low content of six-membered ring glycerin acetal (ketal) produced as a by-product. Therefore, it can be suitably used as a raw material for pharmaceutical intermediates and as a solvent for perfumes. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram illustrating an example of the process for producing glycerin acetal (ketal) from glycerin and a carbonyl compound such as acetone, according to the present invention. [Figure 2]The graphs in Experimental Examples 1-4 show the relationship between the pH of the crude reaction solution supplied to the distillation column and the molar ratio of compound (3) to glycerol acetal (ketal) (1) in the still after distillation. [Modes for carrying out the invention]

[0019] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the following description and can be modified and implemented as appropriate without departing from the spirit of the invention.

[0020] Unless otherwise specified, numerical ranges expressed using "~" in this specification mean a range that includes the numbers before and after "~" as the lower and upper limits, respectively. "A~B" means A or greater and B or less.

[0021] In this specification, "including A or B" means "including A," "including B," and "including A and B," unless otherwise specified.

[0022] In this specification, "mass%" indicates the percentage of a given component contained in 100% of the total amount. Furthermore, "mass%" and "weight%" are synonymous. In this specification, “optional” or “optionally” means that the circumstances described below may or may not occur, and therefore the description includes both the cases in which the circumstances occur and the cases in which they do not occur.

[0023] As used herein, the term "approximately" can mean a range of 20% above or below the stated value. For example, a temperature of approximately 75°C relative to 0°C encompasses the range of 60°C to 90°C. All steps described herein may be carried out in any preferred order, unless otherwise specified herein or unless the context clearly contradicts it.

[0024] The first and second embodiments of the present invention's method for producing glycerin acetal (ketal) may be collectively referred to as "the present invention's method for producing glycerin acetal (ketal)."

[0025] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is merely one example of an embodiment of the present invention and is not limited to these.

[0026] [mechanism] According to the present invention, in a method for producing five-membered ring glycerin acetals (ketals) such as sol ketals from glycerin and carbonyl compounds such as acetone, it is possible to produce high-purity glycerin acetals (ketals) in high yield with reduced generation of impurities derived from by-products of the glycerin acetal (ketal). The reason for this is not entirely clear, but it is presumed that by controlling the pH of the crude reaction solution after the acetalization (ketalization) reaction, the by-products having the aforementioned six-membered ring structure can be preferentially decomposed during distillation purification.

[0027] [Method for producing glycerin acetal (ketal)] (First embodiment) A first embodiment of the method for producing glycerin acetal (ketal) of the present invention includes reacting glycerin with a carbonyl compound represented by the following general formula (2) (hereinafter referred to as "carbonyl compound (2)") in a reaction step described later to obtain a crude reaction solution containing glycerin acetal (ketal) represented by the following general formula (1) (hereinafter referred to as "glycerin acetal (ketal) of the present invention" or "glycerin acetal (ketal) (1)"), and further purifying the crude reaction solution by distillation in a distillation step described later to obtain glycerin acetal (ketal). [ka] [In formula (2), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.] [ka] [In equation (1), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.]

[0028] Details of the glycerin acetal (ketal) (1) will be described later. Details of the carbonyl compound (2) will be described later.

[0029] In the first embodiment of the method for producing glycerin acetal (ketal) of the present invention, the pH of the crude reaction solution in the reaction step is controlled to be within a predetermined range so that the molar ratio of the compound represented by the following general formula (3) (hereinafter referred to as "compound (3)") to the glycerin acetal (ketal) (1) in the still residue obtained in the distillation step is within a predetermined range. This makes it possible to suppress the amount of 6-membered ring glycerin acetal (ketal) produced due to the decomposition of 5-membered ring glycerin acetal (ketal) during distillation. [ka] [In equation (3), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.]

[0030] The aforementioned five-membered ring glycerin acetal (ketal) corresponds to the aforementioned glycerin acetal (ketal) (1), and the aforementioned six-membered ring glycerin acetal (ketal) corresponds to compound (3). Details of the glycerin acetal (ketal) (1) and the compound (3) will be described later.

[0031] In the first embodiment of the method for producing glycerin acetal (ketal) (1) of the present invention, a method for controlling the pH of the crude reaction solution in the reaction step to be within a predetermined range of values ​​can be, for example, a method of adjusting the pH of the crude reaction solution subjected to the distillation step. In this case, the pH of the crude reaction solution in the reaction step may be the same as the pH of the crude reaction solution subjected to the distillation step.

[0032] (Second Embodiment) A second embodiment of the method for producing glycerin acetal (ketal) according to the present invention includes, in a reaction step described later, reacting glycerin with a carbonyl compound represented by the following general formula (2) in the presence of an acid to obtain a crude reaction solution containing glycerin acetal and / or glycerin ketal (1) represented by the following general formula (1), and further, in a distillation step described later, purifying the crude reaction solution by distillation in the presence of an acid and a basic substance to obtain glycerin acetal (ketal). [ka] [In formula (2), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.] [ka] [In equation (1), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.] [ka] [In equation (3), R1 and R2 are equivalent to R1 and R2 in equation (2), respectively.]

[0033] In a second embodiment of the method for producing glycerin acetal (ketal) of the present invention, the amount of 6-membered ring glycerin acetal (ketal) (compound (3) represented by the above general formula (3)) generated due to the decomposition of the 5-membered ring glycerin acetal (ketal) during distillation can be suppressed by distilling the crude reaction solution in the presence of an acid and a basic substance during the distillation step.

[0034] In the second embodiment of the method for producing glycerin acetal (ketal) of the present invention, glycerin, the carbonyl compound represented by general formula (2), the glycerin acetal and / or glycerin ketal (1) represented by general formula (1), and the compound (3) represented by general formula (3) are, respectively, the same as glycerin, the carbonyl compound represented by general formula (2), the glycerin acetal and / or glycerin ketal (1) represented by general formula (1), and the compound (3) represented by general formula (3) in the first embodiment of the method for producing glycerin acetal (ketal) of the present invention.

[0035] In a second embodiment of the method for producing glycerin acetal (ketal) of the present invention, in the distillation step, the crude reaction solution obtained in the reaction step is purified by distillation in the presence of the above-mentioned acid and the above-mentioned basic substance to obtain glycerin acetal and / or glycerin ketal (1). In this case, the "acid" is the "acid" in the reaction step described above. The "basic substance" is the "basic substance" added to the crude reaction solution in the reaction step described above.

[0036] (First and second embodiments) Hereinafter, the first and second embodiments of the method for producing glycerin acetal (ketal) of the present invention will be collectively referred to as "the method for producing glycerin acetal (ketal) of the present invention."

[0037] In the method for producing glycerin acetal (ketal) of the present invention, the distillation step may include distilling and purifying the crude reaction solution to distill off unreacted carbonyl compounds and obtaining a residue containing glycerin acetal (ketal). More specifically, in a method for producing glycerin acetal (ketal) (1), such as solketal, by an acetalization reaction of glycerin with a carbonyl compound such as acetone, when obtaining glycerin acetal (ketal) (1) by distillation purification of the crude reaction solution after the acetalization reaction, the pH of the crude reaction solution in the acetalization reaction step is controlled to be within a predetermined range so that the molar ratio of compound (3) to glycerin acetal (ketal) (1) in the residue obtained in the distillation step is within a predetermined range, thereby obtaining a residue containing glycerin acetal (ketal) (1).

[0038] The "predetermined range of values" in the aforementioned molar ratio refers to a range of values ​​in which the resulting glycerin acetal (ketal) (1) has practically acceptable characteristics or performance. For example, this range may be a value empirically determined using the manufacturing equipment used, or a value theoretically determined using simulations, etc. In the experimental examples of the present invention, the values ​​used are those empirically determined based on the results of a reasonable number of trials using the manufacturing equipment.

[0039] The "predetermined range of values" in pH refers to a range of values ​​in which the molar ratio of compound (3) to glycerin acetal (ketal) (1) falls within the aforementioned predetermined range. This range may be, for example, a value determined empirically using the manufacturing equipment used, or a value determined theoretically using simulations. In the experimental examples of the present invention, the values ​​used are those determined empirically based on the results of a reasonable number of trials using the manufacturing equipment.

[0040] In the still residue obtained in the distillation process, there is no particular upper limit to the molar ratio of compound (3) to glycerin acetal (ketal) (1), but from the viewpoint of economics, such as the manufacturing costs required to purify glycerin acetal (ketal) (1), it is preferable to have a molar ratio of 0.03 or less. The molar ratio is more preferably 0.025 or less, even more preferably 0.020 or less, and particularly preferably 0.015 or less. On the other hand, the lower limit of the molar ratio of compound (3) to glycerin acetal (ketal) (1) is not particularly limited. Compound (3) may not be included (molar ratio = 0), or, from the viewpoint of economics such as the manufacturing costs required for the separation and removal of compound (3), 0.0001 or higher is preferred. The molar ratio is more preferably 0.0003 or higher, even more preferably 0.001 or higher, and particularly preferably 0.003 or higher. The preferred upper and lower limits of the above molar ratios can be combined in any way. For example, the molar ratio of compound (3) to glycerin acetal (ketal) (1) is not particularly limited, and compound (3) may not be included (molar ratio = 0), or it may be preferably 0.0001 to 0.03, more preferably 0.0003 to 0.025, even more preferably 0.001 to 0.020, and particularly preferably 0.003 to 0.015.

[0041] In this specification, the details of the method for measuring the molar ratio of compound (3) to glycerin acetal (ketal) (1) (hereinafter sometimes simply referred to as "molar ratio") will be described later.

[0042] In the method for producing glycerin acetal (ketal) according to the present invention, a specific method for controlling the molar ratio to a desired range, for example, to a range of 0.0 to 0.03, is to control the pH of the crude reaction solution in the reaction step to a predetermined range.

[0043] In the method for producing glycerin acetal (ketal) according to the present invention, the method for controlling the pH of the crude reaction solution in the reaction step to be within a predetermined range is not particularly limited. However, from the viewpoint of suppressing the reverse reaction of glycerin acetal (ketal), it is preferable to add a basic substance, as described later, to the crude reaction solution to control the pH of the crude reaction solution to be within a predetermined range. The method for adding the basic substance described later to the crude reaction solution is not particularly limited, and those skilled in the art can appropriately optimize and use well-known techniques. For example, one method is to add an alkaline solution prepared by dissolving a basic compound in water or an organic solvent. A method using a solid base such as a basic ion exchange resin is preferred because it allows for easy removal of the added solvent or basic compound.

[0044] In the method for producing glycerin acetal (ketal) (1) of the present invention, the upper limit of the pH of the crude reaction solution subjected to the distillation step is not particularly limited, but it is preferably 10.00 or less, more preferably 9.00 or less, even more preferably 8.95 or less, still preferably 8.90 or less, particularly preferably 8.85 or less, and most preferably 8.80 or less. On the other hand, the lower limit of the pH of the crude reaction solution subjected to the distillation step is not particularly limited, but since heating in an acidic region to remove the carbonyl compound causes the reverse reaction of general formula (1) to proceed and the yield decreases, a pH of 7.00 or higher is preferred. A pH of 7.60 or higher is more preferred, 7.65 or higher is even more preferred, 7.70 or higher is even more preferred, 7.75 or higher is particularly preferred, and 7.80 or higher is most preferred. The preferred upper and lower limits of pH mentioned above can be combined in any way. For example, the pH of the crude reaction solution subjected to the distillation step is not particularly limited, but is preferably 7.00 to 10.00, more preferably 7.60 to 9.00, even more preferably 7.65 to 8.95, still more preferably 7.70 to 8.90, particularly preferably 7.75 to 8.85, and most preferably 7.80 to 8.80.

[0045] The method of adding the basic substance described later to the crude reaction solution is not particularly limited, and for example, an alkaline solution prepared by dissolving a basic compound in water or an organic solvent can be added. A method using a solid base from a basic ion exchange resin is preferred because the added solvent or basic compound can be easily removed. Details of the aforementioned basic substance will be described later.

[0046] <Reaction Process> The present invention provides a method for producing glycerin acetal (ketal), which includes a reaction step of reacting glycerin with a carbonyl compound represented by the following general formula (2) to obtain a crude reaction solution containing glycerin acetal (ketal) represented by the following general formula (1).

[0047] The specific embodiments of the reaction in the present invention, in which glycerin is reacted with a carbonyl compound represented by the following general formula (2) to obtain a crude reaction solution containing a glycerin acetal (ketal) represented by general formula (1), are not particularly limited, and known reaction methods can be used. Specifically, methods using the batch reaction format described in Japanese Patent Application Publication No. 2006-273750 or methods using the flow reaction format described in Japanese Patent Application Publication No. 60-87282 can be used. Among these, the method using the flow reaction format is preferred from the viewpoint of superior productivity.

[0048] A specific method for obtaining a crude reaction solution containing the glycerin acetal (ketal) is to fill a reaction tube with a strongly acidic cation exchange resin and react glycerin with a carbonyl compound represented by the following general formula (2).

[0049] Furthermore, in the reaction step of the present invention, the reaction between glycerin and the carbonyl compound can be carried out in the presence of an acid. The type of acid is not particularly limited, and examples include p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and ionic form H +Examples include strongly acidic cation exchange resins. Among these acids, those with an ionic form of H are selected from those that allow for easy separation of the catalyst from the resulting crude reaction solution. + A strongly acidic cation exchange resin is preferred.

[0050] <Distillation Process> The present invention provides a method for producing glycerin acetal (ketal), which includes a distillation step to obtain glycerin acetal (ketal) by distilling and purifying the crude reaction solution obtained in the reaction step.

[0051] The specific embodiments of the distillation process in the present invention are not particularly limited, and known distillation methods can be used. Specifically, examples include atmospheric pressure distillation, reduced pressure distillation, and the use of an evaporator. Among these, atmospheric pressure distillation is preferred.

[0052] As a more specific embodiment of the distillation process, for example, the crude reaction solution obtained in the reaction process is distilled off using atmospheric pressure distillation to remove unreacted carbonyl compounds and by-product water, thereby obtaining a stockpot residue containing glycerin acetal (ketal). Then, the glycerin acetal (ketal) in the stockpot residue is distilled off using reduced pressure distillation to obtain a distillation residue containing high-boiling point by-products and unreacted glycerin, thereby separating and recovering the glycerin acetal (ketal).

[0053] In the method for producing glycerin acetal (ketal) of the present invention, the distillation step may be carried out in a single distillation operation, or it may be carried out in combination of multiple distillation operations. When multiple distillation operations are carried out in combination, a method of carrying out multiple distillation operations under the same conditions, or a method of carrying out multiple distillation operations under different conditions, can be employed.

[0054] In the method for producing glycerin acetal (ketal) according to the present invention, the crude reaction solution obtained in the reaction step may be supplied to the distillation step, or, if necessary, the crude reaction solution obtained in the reaction step may be subjected to other treatments as needed before being supplied to the distillation step. Other treatments mentioned above are not limited to those described above and may include, for example, adding additives, adjusting the pH, or performing purification treatment using other purification methods other than distillation, such as ion exchange resins or crystallization.

[0055] <Carbonyl compound (2) represented by general formula (2)> The carbonyl compound (2) represented by the following general formula (2) is a compound that serves as a starting material when synthesizing glycerin acetal (ketal) in the method for producing glycerin acetal (ketal) of the present invention. [ka] [In formula (2), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.]

[0056] Examples of the carbonyl compound include aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, 3-pentanone, diethyl ketone, cyclopentanone, and cyclohexanone. Acetone is preferred because it is easy to remove unreacted carbonyl compound (2) when distillation is performed after the reaction.

[0057] <Glycerin acetal (ketal) represented by general formula (1) (1)> According to the method for producing glycerin acetal (ketal) of the present invention, glycerin acetal (ketal) (1) represented by the following general formula (1) can be produced. [ka] [In formula (1), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, R 1 and R 2 They may be joined together to form a ring.

[0058] In equation (1), R1 and R2 can be treated as equivalent to R1 and R2 in equation (2), respectively.

[0059] Specifically, the glycerin acetal (ketal) (1) is: If the carbonyl compound (2) is acetone, then 2,2-dimethyl-1,3-dioxolane-4-methanol is an example. If carbonyl compound (2) is a methyl ethyl ketone, an example is 2-ethyl-2-methyl-1,3-dioxolane-4-methanol; if carbonyl compound (2) is a methyl butyl ketone, an example is 2-butyl-2-methyl-1,3-dioxolane-4-methanol. When the carbonyl compound (2) is a methyl isobutyl ketone, examples include 2-isobutyl-2-methyl-1,3-dioxolane-4-methanol.

[0060] <Compound (3) represented by general formula (3)> The present invention provides a method for producing glycerin acetal (ketal), which focuses on compound (3) represented by the following general formula (3), and includes controlling the molar ratio of compound (3) to glycerin acetal (ketal) (1) in the still residue obtained in the distillation step so that it falls within a predetermined range. [ka] [In formula (3), R1 and R2 may be the same or different, and represent a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R1 and R2 may be bonded together to form a ring.]

[0061] In equation (3), R1 and R2 can be treated as equivalent to R1 and R2 in equation (2), respectively.

[0062] When the glycerin acetal (ketal) of the present invention is used as a solvent for pharmaceuticals or perfumes, compound (3) contained as an impurity in the glycerin acetal (ketal) degrades the quality of the final glycerin acetal (ketal). Therefore, by controlling the pH of the crude reaction solution in the reaction step to be within a predetermined range so that the molar ratio of compound (3) to glycerin acetal (ketal) (1) is within a predetermined range, the content of compound (3) can be reduced to a desired value.

[0063] One specific embodiment of compound (3) is 1,3-dioxan-5-ol. For example, if the carbonyl compound (2) is acetone, the corresponding compound (3) is 2,2-dimethyl-1,3-dioxan-5-ol. According to the inventors' investigations, it is presumed that when acetone and glycerin react in the presence of an acid, a certain amount of compound (3), which is a structural isomer of compound (1), is produced in addition to compound (1).

[0064] <Basic substances> The basic substance in this invention is not particularly limited and includes, for example, anion exchange resins; and alkali metal salts such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and sodium acetate. Among the basic substances mentioned above, anion exchange resins are preferred because they have the effect of reducing the molar ratio of compound (3) to glycerol acetal (ketal) (1). The anion exchange resin in the present invention is not particularly limited, and examples include secondary amine type ion exchange resins and tertiary amine type ion exchange resins. Tertiary amine type ion exchange resins are preferred. Commercially available anion exchange resins include Mitsubishi Chemical's DION series such as WA10, WA20, and WA30 (product names), Organo Corporation's Amberlight series such as IRA400JCl and IRA402BLCl (product names), and Sumika Chemtex Corporation's Duolite. TM A113LF and Duolight TM The A116 (product name) Duolite series and similar products can be used.

[0065] The method for producing glycerin acetal (ketal) according to the present invention will be described in detail for each step, with reference to Figure 1. Figure 1 is a schematic diagram showing an example of a manufacturing process in which, according to the present invention, glycerin is reacted with acetone as the carbonyl compound in the present invention to obtain a crude reaction solution containing glycerin acetal (ketal), and then the crude reaction solution is purified by distillation to separate and recover the glycerin acetal (ketal).

[0066] The raw materials, acetone and glycerin, are introduced into reactor 1. A cation exchange resin is introduced into reactor 1, and a reaction solution containing glycerin acetal (ketal) is obtained by the condensation reaction of acetone and glycerin. Water is produced as a reaction byproduct at this time.

[0067] In filter 2, the cation exchange resin is filtered and separated from the reaction solution obtained in reactor 1.

[0068] In the pH adjustment reactor 3, the reaction solution filtered and separated in the filter 2 is brought into contact with an anion exchange resin to adjust the pH to a predetermined range.

[0069] In filter 4, the anion exchange resin is separated from the reaction solution after its pH has been adjusted in pH adjustment reactor 3.

[0070] In the first distillation column 5, unreacted acetone and water, a reaction by-product, are separated and removed from the top of the column by distillation from the reaction solution, which has been adjusted to a pH within a predetermined range by the filter 4, to obtain a bottom liquid (remainder residue) containing glycerin and glycerin acetal (ketal). The acetone recovered in the distillation column 5 may be used again as a reaction raw material by supplying it to the reactor 1 after removing the water.

[0071] In the second distillation column 6, the bottom liquid (pot residue) containing glycerin and glycerin acetal (ketal) obtained in the first distillation column 5 is separated by distillation, and the desired glycerin acetal (ketal) is obtained from the distillate. [Examples]

[0072] The present invention will be described more specifically below with reference to alternative and comparative experimental examples, but the present invention is not limited to the following experimental examples unless it exceeds the essence of the invention.

[0073] In this experimental example and comparative experimental example, 2,2-dimethyl-1,3-dioxolane-4-methanol corresponds to glycerin acetal (ketal) (1) in the present invention, and 2,2-dimethyl-1,3-dioxan-5-ol corresponds to compound (3) in the present invention.

[0074] [raw materials] The abbreviations for the compounds used in the following experimental and comparative experiments are as follows: Acetone (product name, manufactured by Mitsubishi Chemical Corporation) Glycerin (product name, manufactured by Sakamoto Pharmaceutical Co., Ltd.) UBK08H: Acidic cation exchange resin (product name: DIAION) TM (UBK08H, manufactured by Mitsubishi Chemical Corporation) WA30: Basic anion exchange resin (product name: DIAION) TM WA30 (manufactured by Mitsubishi Chemical Corporation) Dodecylamine (product name, manufactured by Tokyo Chemical Industry Co., Ltd.) NaOH: Sodium hydroxide (trade name, manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0075] [Evaluation method] The measurement and evaluation methods in this experimental example and comparative experimental examples are as follows.

[0076] [Measurement of pH of crude reaction solution] A pH electrode (model: 9681S-10D, HORIBA) was immersed in a solution obtained by diluting 10 g of the crude reaction solution obtained in the experimental example and comparative experimental examples with 40 g of ultrapure water, and the pH of the crude reaction solution was measured.

[0077] [Yields of glycerin acetal (ketal) (1) and compound (3)] For the crude reaction solution obtained in Synthesis Example 1, it was analyzed under the following GC measurement conditions using a gas chromatograph (GC) measurement device and the gas chromatography internal standard method. 2,2-Dimethyl-1,3-dioxolan-4-methanol as glycerin and glycerin acetal (ketal) (1), and 2,2-Dimethyl-1,3-dioxan-5-ol as compound (3) in the crude reaction solution were quantified, and the yields of glycerin acetal (ketal) (1) and compound (3) were calculated.

[0078] [GC measurement conditions] GC device: GC-2014 (high-performance general-purpose gas chromatograph, manufactured by Shimadzu Corporation) Detector: Flame ionization detector (FID) Carrier gas: Helium (column flow rate 3.71 ml / min) Column: Capillary column InterCap Pure-WAX (manufactured by GL Sciences Inc., size: length 60 m × inner diameter 0.32 mm, film thickness 0.50 μm) Column temperature: 50 °C (holding time 5 minutes) → temperature increase at 10 °C / min → 230 °C (holding time 17 minutes) Inlet temperature: 250 °C Detector temperature: 250 °C Sample volume: 0.2 μL (split ratio: 1 / 10) Quantification method: Internal standard method (internal standard: acetonitrile)

[0079] Next, the charged glycerin amount, the contents of glycerin and glycerin acetal (ketal) (1) as 2-dimethyl-1,3-dioxolan-4-methanol and compound (3) as 2,2-dimethyl-1,3-dioxan-5-ol in the crude reaction solution were used to calculate the yields of glycerin acetal (ketal) (1) and compound (3) using the following calculation formula. The evaluation results are shown in Table 1. (Calculation formula) Yield of glycerin acetal (ketal) (1) and compound (3) (%) = [Amount of glycerin acetal (ketal) (1) produced (mol) + Amount of compound (3) produced (mol)] / [Charged glycerin amount (mol)] × 100

[0080] <Molar ratio of compound (3) to glycerin acetal (ketal) (1)> Regarding the crude reaction solution supplied to the distillation apparatus or the bottom residue in the simple distillation apparatus, using a gas chromatograph measuring apparatus (GC apparatus), the concentrations (unit: mass%) of 2,2-dimethyl-1,3-dioxolan-4-methanol as glycerin acetal (ketal) (1) and 2,2-dimethyl-1,3-dioxan-5-ol as compound (3) in the crude reaction solution or the bottom residue were determined under the following GC measurement conditions, converted to the amount of substance (unit: mol), and then the molar ratio of compound (3) to glycerin acetal (ketal) (1) ("molar ratio of compound (3) / glycerin acetal (ketal) (1)") was calculated using the following formula.

[0081] Molar ratio of compound (3) / glycerin acetal (ketal) (1) = {Amount of substance of compound (3) contained in the bottom residue (unit: mol)} / {Amount of substance of glycerin acetal (ketal) (1) contained in the bottom residue (unit: mol)}

[0082] <GC measurement conditions> GC apparatus: GC-2014 (high-performance general-purpose gas chromatograph, manufactured by Shimadzu Corporation) Detector: Flame ionization detector (FID) Carrier gas: Helium (column flow rate 3.71 ml / min) Column: Capillary column InterCap Pure-WAX (manufactured by GL Sciences Inc., size: length 60 m × inner diameter 0.32 mm, film thickness 0.50 μm) Column temperature: 50°C (holding time 5 minutes) → temperature increase at 10°C / min → 230°C (holding time 17 minutes) Inlet temperature: 250°C Detector temperature: 250°C Sample amount: 0.2 μL (split ratio: 1 / 10) Quantification method: Internal standard method (internal standard: acetonitrile)

[0083] As a sample for GC measurement, the crude reaction solution or the residue in the still in the simple distillation apparatus was used as it was without pretreatment.

[0084] <Decomposition rate of glycerin acetal (ketal) (1)> For the crude reaction solution supplied to the distillation apparatus, the residue in the still after distillation, and the distillate, using a gas chromatograph measuring device (GC device), the concentration (unit: mass%) of glycerin acetal (ketal) (1) as 2,2-dimethyl-1,3-dioxolan-4-methanol was determined under the following GC measurement conditions, and after converting to the amount of substance (unit: mole), the decomposition rate of glycerin acetal (ketal) (1) was calculated using the following formula.

[0085] Decomposition rate of glycerin acetal (ketal) (1) = 100 - {amount of substance (unit: mole) of glycerin acetal (ketal) (1) contained in the residue and distillate after distillation} / {amount of substance (unit: mole) of glycerin acetal (ketal) (1) contained in the crude reaction solution supplied to the distillation apparatus} × 100

[0086] <GC measurement conditions> GC device: GC-2014 (high-performance general-purpose gas chromatograph, manufactured by Shimadzu Corporation) Detector: Flame ionization detector (FID) Carrier gas: Helium (column flow rate 3.71 ml / min) Column: Capillary column InterCap Pure-WAX (GL Sciences Co., Ltd., Size: Length 60m x Inner diameter 0.32mm, Film thickness 0.50μm) Column temperature: 50°C (holding time 5 minutes) → increase temperature at 10°C / min → 230°C (holding time 17 minutes) Inlet temperature: 250℃ Detector temperature: 250℃ Sample volume: 0.2 μL (Split ratio: 1 / 10) Quantitative method: Internal standard method (Internal standard: Acetonitrile)

[0087] For GC measurement, the residue from the simple distillation apparatus was used directly without any pretreatment.

[0088] [Synthesis Example 1] 50 mL of acetone-substituted acidic ion exchange resin UBK08H (Mitsubishi Chemical Corporation) was packed into a SUS316 reaction tube with a diameter of 112 / 230 mm. Acetone was passed through the reaction tube at a flow rate of 4 mL / min and glycerin at a flow rate of 1 mL / min, and the reaction tube was heated until the measured temperature reached 50°C, and a stabilization treatment was performed for 1 hour. Next, while maintaining the measured temperature in the reaction tube at 50°C, the acetalization reaction was carried out for 4 hours by passing acetone and glycerin through the tube. After that, a crude reaction solution containing glycerin acetal (ketal) (1) as 2,2-dimethyl-1,3-dioxolane-4-methanol, compound (3) as 2,2-dimethyl-1,3-dioxan-5-ol, unreacted acetone, unreacted glycerin, and water was obtained from the outlet of the reaction tube. The yield of glycerol acetal (ketal) (1) (1), calculated according to the measurement method described above, was 69% and the pH was 6.86 for the crude reaction solution obtained.

[0089] [Synthesis Example 2] In a 1L flask, 418g of acetone, 166g of glycerin, and 23g of acidic ion exchange resin UBK08H (manufactured by Mitsubishi Chemical Corporation) were added. The reaction solution in the flask was heated to 50°C and then reacted for 2 hours. Next, UBK08H was filtered off to obtain a crude reaction solution containing 2,2-dimethyl-1,3-dioxolane-4-methanol as glycerin acetal (ketal) (1), 2,2-dimethyl-1,3-dioxan-5-ol as compound (3), unreacted acetone, unreacted glycerin, and water. The yield of glycerin acetal (ketal) (1) (1), calculated according to the measurement method described above, was 56% and the pH was 6.77 for the crude reaction solution obtained.

[0090] [Experimental Example 1] To the crude reaction solution obtained in Synthesis Example 1, basic ion exchange resin WA30 was added as a basic substance to the crude reaction solution in a proportion of 0.5% by weight, and the mixture was stirred with a stirring bar for 30 minutes. After stirring, the anion exchange resin was filtered off, and the pH of the filtered crude reaction solution was measured to be 7.85. Next, 100 g of the filtered crude reaction solution was placed in a simple distillation apparatus equipped with a thermometer, electromagnetic stirrer, reflux tubing, and condenser, and set in an oil bath. The crude reaction solution in the simple distillation apparatus was then heated at atmospheric pressure until its temperature reached 120°C while distilling off acetone and water, which are light-boiling components. The molar concentrations of glycerin acetal (ketal) (1) and compound (3) were determined in the still residue in the simple distillation apparatus. The molar ratio of compound (3) to glycerin acetal (ketal) (1) before and after distillation (hereinafter referred to as "molar ratio (3) / (1)") and the decomposition rate (%) of glycerin acetal (ketal) (1) were calculated. The obtained evaluation results are shown in Table 1.

[0091] [Experimental Examples 2-4] In Experimental Example 1, the amount of basic anion exchange resin (WA30) added was changed so that its content in the crude reaction solution was as shown in Table 1. The same procedure as in Experimental Example 1 was used to obtain the still from the simple distillation apparatus. The evaluation results of the obtained still are shown in Table 1.

[0092] [Experimental Example 5] In Experimental Example 1, a 0.8 wt% aqueous sodium hydroxide solution was used as the basic substance instead of the basic anion exchange resin (WA30). The aqueous sodium hydroxide solution was added to the crude reaction solution so that the sodium hydroxide content in the crude reaction solution was 0.0001 mass%, and the solution was supplied as a distillation raw material without filtration. The same procedure as in Experimental Example 1 was followed to obtain the still residue from the simple distillation apparatus. The evaluation results of the obtained still residue are shown in Table 1.

[0093] [Comparative Experiment Example 1] In Experimental Example 1, the same procedure as in Experimental Example 1 was used to obtain the still residue from the simple distillation apparatus, except that basic substances were not used and the raw materials were supplied without filtration. The evaluation results of the obtained still residue are shown in Table 1.

[0094] [Comparative Experiment Example 2] In Experimental Example 5, the same procedure as in Experimental Example 5 was used to obtain the still residue from the simple distillation apparatus, except that the sodium hydroxide aqueous solution was added so that the sodium hydroxide content was 0.01% by mass. The pH of the crude reaction solution after adding the sodium hydroxide aqueous solution was measured to be 11.92. The evaluation results of the obtained still residue are shown in Table 1.

[0095] [Comparative Experiment Example 3] In Experimental Example 1, dodecylamine was used as the basic substance instead of a basic anion exchange resin (WA30). The dodecylamine was added to the crude reaction solution so that its content was 0.005% by mass. The solution was supplied as a distillation raw material without filtration. The same procedure as in Experimental Example 1 was followed to obtain the still residue from the simple distillation apparatus. The evaluation results of the obtained still residue are shown in Table 1. The pH of the crude reaction solution after the addition of dodecylamine was measured to be 10.76. The evaluation results of the obtained still residue are shown in Table 1.

[0096] [Experimental Example 6] To 631 g of the crude reaction solution obtained in Synthesis Example 2, 38 g of basic ion exchange resin WA30 was added as a basic substance, and the mixture was stirred for 30 minutes using a stirring bar. After stirring, the pH of the filtered crude reaction solution obtained by filtering off the anion exchange resin was measured to be 8.71. Next, the crude reaction mixture was placed in a multi-stage distillation apparatus equipped with a thermometer, electromagnetic stirrer, vacuum pump, Aldershaw distillation column with 20 theoretical stages, condenser, and distillation receiver. The mixture was heated in an oil bath, and while maintaining the temperature of the crude reaction mixture in the multi-stage distillation apparatus at 154°C, distillation was carried out at a reflux ratio of 1 until the distillation of acetone decreased, yielding the stock. Subsequently, the stock was cooled to a temperature of 100°C or lower. Then, the pressure inside the distillation apparatus was reduced to a top pressure of 8 kPa, and heating was resumed in an oil bath. While maintaining the temperature at 153°C, distillation was carried out at a reflux ratio of 1 until the distillate was gone. The distillate obtained under reduced pressure was collected and GC analysis was performed. The molar ratios (3) / (1) before and after distillation were 0.026 and 0.012, respectively, and the decomposition rate of glycerin acetal (ketal) (1) was 13.91%.

[0097] [Experimental Example 7] In Experimental Example 6, a 0.8 wt% aqueous sodium hydroxide solution was used as the basic substance instead of a basic anion exchange resin (WA30). The aqueous sodium hydroxide solution was added to the crude reaction solution so that the sodium hydroxide content was 0.0001 mass%, and the distillate was collected from the multi-stage distillation apparatus using the same procedure as in Experimental Example 6, except that the solution was supplied as a distillation raw material without filtration. The pH of the crude reaction solution before distillation was 8.82, the molar ratio (3) / (1) before and after distillation was 0.028 and 0.015, respectively, and the decomposition rate of glycerin acetal (ketal) was 7.00%.

[0098] In Experimental Examples 1-5 and Comparative Experimental Examples 1-3, atmospheric pressure distillation was used to recover a mixture of the target product, glycerin acetal (ketal) (1), and unreacted glycerin as a residue in the pot, and water and unreacted acetone were removed by distillation. On the other hand, in experimental examples 6-7, the target product, glycerol acetal (ketal) (1), was recovered as a distillate using vacuum distillation, while unreacted glycerol remained at the bottom of the column as distillation residue.

[0099] [Table 1]

[0100] As shown in Table 1 and Figure 2, in Experimental Examples 1-5 and Comparative Experimental Examples 2-3, the pH of the crude reaction solution was controlled to be alkaline, so the decomposition rate of glycerin acetal (ketal) (1) was suppressed compared to Comparative Experimental Example 1.

[0101] In particular, in Experimental Examples 1-5, the decomposition rate of glycerol acetal (ketal) (1) was lower compared to Comparative Experimental Examples 2-3, and the molar ratio (3) / (1) decreased before and after distillation, indicating that compound (3) decomposed during distillation.

[0102] Furthermore, in Experimental Examples 1-4, the closer the crude reaction solution subjected to distillation is to neutral (pH 7), the lower the molar ratio (3) / (1), indicating that compound (3) is more easily decomposed.

[0103] In Experimental Example 5, NaOH dissolved in the crude reaction solution was used to adjust the pH, eliminating the need for filtration before distillation and thus achieving a reduction in the number of steps.

[0104] On the other hand, in comparative experiment 1, since the pH of the crude reaction solution was not adjusted (pH=7.52), both glycerol acetal (ketal) (1) and compound (3) decomposed, and there was no selectivity in the decomposition reaction. In comparative experiments 2 and 3, the selectivity of the decomposition reaction of glycerol acetal (ketal) (1) was lost as the pH increased, indicating that the selective decomposition of glycerol acetal (ketal) (1) is a pH-dependent reaction. Furthermore, comparative experiment example 3 showed that when the type of base is different, the selectivity in the decomposition reaction of glycerol acetal (ketal) (1) disappears, indicating that the selective decomposition of glycerol acetal (ketal) (1) is high with basic substances such as WA30 and NaOH. Furthermore, a comparison of Experimental Example 6 with Experimental Examples 5 and 7 revealed that, even at similar pH levels, WA30 exhibits higher selectivity than NaOH in the decomposition reaction of glycerol acetal (ketal) (1).

[0105] Although the present invention has been described above with reference to specific embodiments, each embodiment is presented as an example and does not limit the scope of the present invention. Each embodiment described herein can be modified in various ways without departing from the spirit of the invention and can be combined with features described in other embodiments to the extent that is feasible. [Industrial applicability]

[0106] The present invention's method for producing glycerin acetal (ketal) offers significant industrial value, as it allows for the production of high-purity glycerin acetal (ketal) with a lower amount of impurities introduced into the final product compared to conventional purification techniques. [Explanation of Symbols]

[0107] 1 Reactor 2. Filter 3 pH adjustment reactor 4. Filter 5. First distillation column 6. Second distillation column 7. Acetone 8. Glycerin 9. Acetone 10 water 11. Glycerin acetal (ketal)

Claims

1. A reaction step in which glycerin is reacted with a carbonyl compound represented by the following general formula (2) to obtain a crude reaction solution containing glycerin acetal and / or glycerin ketal (1) represented by the following general formula (1), The process includes a distillation step in which the crude reaction solution is purified by distillation to obtain glycerin acetal and / or glycerin ketal (1). A method for producing glycerin acetal and / or glycerin ketal, A method for producing glycerin acetal and / or glycerin ketal, comprising controlling the pH of the crude reaction solution in the reaction step to be within a predetermined range of values, such that the molar ratio of compound (3) represented by the following general formula (3) to glycerin acetal and / or glycerin ketal (1) in the still residue obtained in the distillation step is within a predetermined range of values. 【Chemistry 1】 [In formula (2), R １ and R ２ R represents a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R may be the same or different. １ and R ２ They may be joined together to form a ring. 【Chemistry 2】 [In formula (1), R １ and R ２ These are R in equation (2), respectively. １ and R ２ This is synonymous with [the above]. 【Transformation 3】 〔In formula (3), R １ and R ２ are synonymous with R １ and R ２ in formula (2), respectively.〕

2. A method for producing glycerin acetal and / or glycerin ketal according to claim 1, comprising the step of distilling the crude reaction solution to distill off unreacted carbonyl compounds and obtaining a boiler residue containing glycerin acetal and / or glycerin ketal (1).

3. A method for producing glycerin acetal and / or glycerin ketal according to claim 1, comprising controlling the pH of the crude reaction solution in the reaction step to a predetermined range such that the molar ratio of the compound represented by the general formula (3) to the glycerin acetal and / or glycerin ketal (1) in the still residue obtained in the distillation step is within a range of 0 to 0.

03.

4. The method for producing glycerin acetal and / or glycerin ketal according to claim 3, wherein the reaction step includes adding a basic substance to the crude reaction solution to control the pH of the crude reaction solution within a predetermined range.

5. The method for producing glycerin acetal and / or glycerin ketal according to claim 4, wherein the basic substance comprises an anion exchange resin.

6. A method for producing glycerin acetal and / or glycerin ketal according to claim 1, comprising controlling the pH of the crude reaction solution subjected to the distillation step to within the range of 7.00 to 10.

00.

7. A method for producing glycerin acetal and / or glycerin ketal according to claim 1, comprising controlling the pH of the crude reaction solution subjected to the distillation step to within the range of 7.60 to 9.

00.

8. The method for producing glycerin acetal and / or glycerin ketal according to claim 1, wherein the reaction step involves carrying out the reaction between glycerin and a carbonyl compound in the presence of an acid.

9. A reaction step in which glycerin is reacted with a carbonyl compound represented by the following general formula (2) in the presence of an acid to obtain a crude reaction solution containing glycerin acetal and / or glycerin ketal (1) represented by the following general formula (1), A method for producing glycerin acetal and / or glycerin ketal, comprising a distillation step of distilling the crude reaction solution in the presence of an acid and a basic substance to obtain glycerin acetal and / or glycerin ketal (1). 【Chemistry 4】 [In formula (2), R １ and R ２ R represents a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group, and R may be the same or different. １ and R ２ They may be joined together to form a ring. 【Transformation 5】 [In formula (1), R １ and R ２ These are R in equation (2), respectively. １ and R ２ This is synonymous with [the above].

10. A method for producing glycerin acetal and / or glycerin ketal according to claim 9, wherein the pH of the crude reaction solution subjected to the distillation step is in the range of 7.00 to 10.00.

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