Method for producing N-methyl-2-pyrrolidone using polyhydroxyalkanoate, and N-methyl-2-pyrrolidone prepared thereby

Abstract

The present invention relates to a method for producing N-methyl-2-pyrrolidone using a polyhydroxyalkanoate, and N-methyl-2-pyrrolidone produced thereby. The production method includes (1) preparing a polyhydroxyalkanoate, (2) reacting the polyhydroxyalkanoate with an amine compound at 110 to 180°C to produce an acyclic amide compound, and (3) heating the acyclic amide compound.

Description

[Technical Field]

[0001] The present disclosure relates to a method for preparing the high-value chemical methylpyrrolidone (N-methyl-2-pyrrolidone, NMP) using polyhydroxyalkanoates. [Background technology]

[0002] Biorefinery is a technology that converts biomass into biofuels (energy), electricity, heat, and high-value-added chemicals through biological or chemical conversion processes. This biorefinery technology is similar to petroleum refining technology, which produces fuels and petrochemical products from crude oil as a petroleum resource. Currently, petroleum refineries face environmental pollution issues due to unavoidable greenhouse gas emissions during the process, and are also limited by the depletion of petroleum resources. Therefore, research is being conducted into using biomass instead of petroleum resources to produce higher-value-added chemicals.

[0003] Polyhydroxyalkanoates (PHAs) are substances that accumulate within microbial cells as biomass and have attracted attention as completely degradable biodegradable materials. In recent years, technologies have been developed to produce high-value-added chemicals and intermediates by chemical depolymerization of PHAs. For example, methylpyrrolidone (N-methyl-2-pyrrolidone, NMP) is prepared using PHAs.

[0004] Methylpyrrolidone is chemically stable and has excellent heat resistance, making it a useful starting material for various organic syntheses requiring inert media or organic solvents. Furthermore, due to its high polarity and solubility, it is used as a cleaning solvent and additive in the electrical and electronics fields and the paint industry. Furthermore, methylpyrrolidone is used as a binder component in the coating of cathode materials in the secondary battery industry, which is an element of ESS industrial technology that can store produced energy. Methylpyrrolidone, which is widely used in various fields, could be prepared using biomass polyhydroxyalkanoates, contributing to the reduction of environmental pollution and potentially serving as a substitute for dwindling petroleum resources.

[0005] However, the process for preparing methylpyrrolidone using currently available polyhydroxyalkanoates is complicated, and the yield of methylpyrrolidone is not sufficient. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 2011-0058002 Summary of the Invention [Problem to be solved by the invention]

[0007] Thus, there have been limitations to the high-yield production of methylpyrrolidone in an environmentally friendly manner. Specifically, 1,4-butanediol (BDO) derived from petroleum resources is converted into a gamma-butyrolactone (GBL) intermediate in the presence of a metal catalyst, which is then reacted with an alkylamine to produce methylpyrrolidone in a conventional manner. However, this process has the drawbacks of causing the depletion of petroleum resources, causing environmental pollution, and reducing economic viability due to the use of a metal catalyst.

[0008] Therefore, in order to prevent the depletion of petroleum resources and to produce methylpyrrolidone in an environmentally friendly manner, attempts have been made to produce methylpyrrolidone using polyhydroxyalkanoates as biomass, but these attempts have had problems such as a complicated process and a reduced yield of methylpyrrolidone.

[0009] The present inventors have conducted extensive research to solve these problems, and as a result have found that methylpyrrolidone can be produced in high yield by a relatively simple process by optimizing the reactants and reaction conditions used in the depolymerization reaction of polyhydroxyalkanoate.

[0010] Therefore, an object of the present disclosure is to provide an environmentally friendly, economical method for preparing methylpyrrolidone using polyhydroxyalkanoate in high yield.

[0011] Another object of the present disclosure is to provide methylpyrrolidone prepared by the above-mentioned preparation method. [Means for solving the problem]

[0012] To achieve the above object, the method for preparing methylpyrrolidone of the present disclosure includes (1) preparing a polyhydroxyalkanoate, (2) reacting the polyhydroxyalkanoate with an amine compound at 110 to 180°C to prepare an acyclic amide compound, and (3) heating the acyclic amide compound.

[0013] According to one embodiment of the present disclosure, in the above step (1), the polyhydroxyalkanoate may contain repeating units derived from 4-hydroxybutyric acid (4HB).

[0014] According to another embodiment of the present disclosure, in the step (2), the amine compound may include a compound selected from the group consisting of monomethylamine, an aqueous monomethylamine solution, dimethylamine, ammonia, and ammonium water.

[0015] According to another embodiment of the present disclosure, in the step (2), the polyhydroxyalkanoate and the amine compound may be reacted at an equivalent ratio of 1:1.01 to 2.5.

[0016] According to another embodiment of the present disclosure, in the step (2), the reaction time between the polyhydroxyalkanoate and the amine compound may be 10 hours or less.

[0017] According to another embodiment of the present disclosure, in step (2), the acyclic amide compound may include a compound selected from the group consisting of 4-hydroxy-N-methylbutanamide, 4-hydroxybutanamide, and 4-hydroxy-N-(2-hydroxyethyl)butanamide.

[0018] According to another embodiment of the present disclosure, in the step (3), the non-cyclic amide compound may be heated to a temperature of 200° C. or higher.

[0019] According to another embodiment of the present disclosure, in the step (3), the initial pressure for heating the non-cyclic amide compound may be 1 to 80 bar.

[0020] According to another embodiment of the present disclosure, in the step (3), the difference (P2-P1) between the initial pressure (P1) for heating the acyclic amide compound and the equilibrium pressure (P2) after one hour of heating may be 15 bar or more.

[0021] According to another embodiment of the present disclosure, in the step (3), the non-cyclic amide compound may be heated for 1 to 8 hours.

[0022] According to another embodiment of the present disclosure, in the step (2), the conversion rate of the polyhydroxyalkanoate may be 80% or more, and the selectivity for the acyclic amide compound may be 90% or more.

[0023] According to another embodiment of the present disclosure, in the step (3), the conversion rate of the non-cyclic amide compound may be 90% or more.

[0024] According to another embodiment of the present disclosure, the yield of the methylpyrrolidone when prepared by the above preparation method is 90% or more.

[0025] On the other hand, in order to achieve the above object, the present disclosure provides methylpyrrolidone prepared by the above preparation method. [Effects of the Invention]

[0026] According to the present disclosure, methylpyrrolidone is produced using polyhydroxyalkanoate, which is a biomass, as a starting material instead of petroleum resources, thereby enabling environmentally friendly production while suppressing the depletion of petroleum resources. Furthermore, the present disclosure enables methylpyrrolidone to be produced economically and with a high yield by optimizing the depolymerization reaction of polyhydroxyalkanoate. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a flow chart illustrating a method for preparing methylpyrrolidone according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present disclosure is described in detail below. The present disclosure is not limited to the disclosure described below, and can be modified in various forms without departing from the gist of the present disclosure.

[0029] As used herein, the term "comprises" is used to explicitly identify certain features, regions, steps, treatments, elements, and / or components, and does not exclude the presence or addition of other features, regions, steps, treatments, elements, and / or components, unless specifically stated to the contrary.

[0030] Numerical values ​​and expressions relating to amounts of components, reaction conditions, etc. used herein can be understood even if modified by the word "approximately," unless otherwise specified.

[0031] The present disclosure provides a method for preparing methylpyrrolidone using polyhydroxyalkanoate as biomass, and methylpyrrolidone prepared by the method. The present disclosure is characterized by the fact that methylpyrrolidone can be prepared in an environmentally friendly and economical manner with a high yield by optimizing the reactants and reaction conditions used in the depolymerization process of polyhydroxyalkanoate. The details are described below.

[0032] Method for preparing methylpyrrolidone The method for producing methylpyrrolidone according to the present disclosure includes (1) preparing a polyhydroxyalkanoate, (2) reacting the polyhydroxyalkanoate with an amine compound at 110 to 180°C to prepare an acyclic amide compound, and (3) heating the acyclic amide compound.

[0033] Each step will be described below with reference to FIG.

[0034] Step (1): Preparation of polyhydroxyalkanoate According to the present disclosure, step (1) is to prepare polyhydroxyalkanoate, which is biomass.

[0035] Polyhydroxyalkanoates are naturally occurring thermoplastic polyester polymers that accumulate within microbial cells. They have similar physical properties to petroleum-derived synthetic biodegradable polymers such as PBAT (polybutylene adipate terephthalate), PBS (polybutylene succinate), PBST (polybutylene succinate terephthalate), and PBSA (polybutylene succinate adipate), and are highly biodegradable and biocompatible.

[0036] The polyhydroxyalkanoate may be obtained by disrupting cells by a mechanical or physical method, or by disrupting cells by a non-mechanical or chemical method. Specifically, the polyhydroxyalkanoate may be obtained by disrupting microbial cells using at least one method selected from the group consisting of ultrasonic disruption, high-pressure disruption, and mill disruption.

[0037] Sonication may be performed for 10 to 60 minutes at an energy level of 20 Hz or higher, or more specifically, for 10 to 60 minutes, 15 to 55 minutes, or 20 to 50 minutes at an energy level of 60 Hz or lower, 50 Hz or lower, or 40 Hz or lower.

[0038] High-pressure disruption may be carried out at a pressure of 10 bar or more for 1 to 60 minutes. Specifically, high-pressure disruption may be carried out at a pressure of 10 bar or more, 20 bar or more, or 50 bar or more for 1 to 60 minutes, 2 to 60 minutes, or 3 to 60 minutes.

[0039] Milling may be carried out using a colloid mill, a bead mill, or a ball mill for 1 to 60 minutes, 2 to 60 minutes, or 3 to 60 minutes.

[0040] More specifically, polyhydroxyalkanoates may be obtained by enzymatically catalyzing polymerization of one or more monomers (monomer repeating units) in microbial cells, followed by disruption of the cells.

[0041] The polyhydroxyalkanoate obtained in this manner may have a purity of 90% or more, specifically 92% or more, 94% or more, 96% or more, 98% or more, 99% or more, or 99.9% or more (e.g., 90 to 100%, 95 to 100%, or 98 to 99.5%), but is not limited thereto.

[0042] Weight average molecular weight (M w) may be, but is not limited to, 10,000 to 1,200,000 g / mol, 50,000 to 1,000,000 g / mol, 100,000 to 900,000 g / mol, 150,000 to 800,000 g / mol, 200,000 to 700,000 g / mol, or 250,000 to 600,000 g / mol.

[0043] Polyhydroxyalkanoates have a glass transition temperature (T) of -45 to 80°C, -35 to 70°C, -30 to 60°C, -25 to 50°C, -20 to 30°C, -15 to 15°C, or -15 to 0°C. g ), but is not limited to these.

[0044] The crystallization temperature (T c ) may or may not be measured. Specifically, the crystallization temperature (T c ) does not need to be measured, and may be 70 to 120°C, 75 to 120°C, 75 to 115°C, 75 to 110°C, or 80 to 110°C, but is not limited to these.

[0045] The melting temperature (T m ) may or may not be measured. Specifically, the melting temperature (T m ) does not need to be measured, and may be 100 to 170°C, 110 to 150°C, 115 to 145°C, or 120 to 140°C, but is not limited to these.

[0046] The decomposition temperature (T d ) may be, but is not limited to, 140 to 310°C, 160 to 290°C, 190 to 260°C, or 220 to 230°C. For example, the decomposition temperature (T d ) may be 140 to 160°C, 190 to 220°C, 230 to 260°C, or 290 to 310°C.

[0047] The polyhydroxyalkanoate may have a polydisperse index (PDI) of, but is not limited to, 1.0 or more, 1.2 or more, 1.5 or more, 1.8 or more, 1.9 or more, or 2.0 or more, and 5.0 or less, 4.0 or less, 3.0 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, or 2.5 or less.

[0048] The polyhydroxyalkanoate may contain repeating units derived from 4-hydroxybutyric acid (4HB) (4HB repeating units). Specifically, the polyhydroxyalkanoate may be in the form of a polymer consisting solely of 4HB repeating units, or may be in the form of a copolymer containing 4HB repeating units and repeating units other than 4HB repeating units. More specifically, the polyhydroxyalkanoate may be selected from the group consisting of poly-4-hydroxybutyric acid (P4HB) and poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid) (P3HB-co-4HB), but is not limited thereto. As one of the above substances, polyhydroxyalkanoate has excellent reactivity with amine compounds and can be easily converted to acyclic amide compounds. This allows methylpyrrolidone to be prepared in an environmentally friendly manner with high yields.

[0049] On the other hand, the crystallinity of polyhydroxyalkanoates (PHAs) may be adjusted depending on the content of 4HB repeating units, and they are sometimes classified into semi-crystalline PHAs (scPHAs) and amorphous PHAs (aPHAs).

[0050] Specifically, the semi-crystalline PHA (scPHA) may have a 4HB repeat unit content of 0.1 to 30 wt%, 1 to 28 wt%, 3 to 26 wt%, 5 to 25 wt%, 8 to 23 wt%, 10 to 20 wt%, or 10 to 15 wt%, based on the total weight of the polyhydroxyalkanoate (PHA). The amorphous PHA (aPHA) may have a 4HB repeat unit content of 15 to 60 wt%, 20 to 58 wt%, 25 to 55 wt%, 30 to 53 wt%, 35 to 50 wt%, 40 to 49 wt%, or 45 to 48 wt%, based on the total weight of the polyhydroxyalkanoate (PHA).

[0051] The polyhydroxyalkanoate (PHA) may be composed solely of semicrystalline PHA (scPHA), may be composed solely of amorphous PHA (aPHA), or may be composed of a mixture thereof. Specifically, it may be amorphous PHA (aPHA). For example, when the polyhydroxyalkanoate (PHA) is poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB-co-4HB), it may be amorphous P3HB-co-4HB having a 4HB repeat unit content of 15 to 60 wt%.

[0052] Step (2): Preparation of acyclic amide compounds According to the present disclosure, step (2) is to prepare a non-cyclic amide compound in high yield by reacting a polyhydroxyalkanoate with an amine compound at a specific temperature.

[0053] The reaction temperature between the polyhydroxyalkanoate and the amine compound may be 110 to 180° C. Specifically, the reaction temperature may be 110 to 175° C., 113 to 170° C., 113 to 165° C., 115 to 160° C., 115 to 155° C., 118 to 150° C., 118 to 145° C., or 120 to 140° C., but is not limited to these.

[0054] The reaction time between the polyhydroxyalkanoate and the amine compound may be 10 hours or less. Specifically, the reaction time may be 9 hours or less, 8 hours or less, 7 hours or less, or 6 hours or less (for example, 1 to 10 hours, 2 to 10 hours, 3 to 10 hours, or 6 to 10 hours), but is not limited to these.

[0055] The reaction ratio of the polyhydroxyalkanoate to the amine compound may be 1:1.01 to 2.5 in terms of equivalent ratio. Specifically, the reaction ratio may be, but is not limited to, 1:1.05 to 2.4 equivalent ratio, 1:1.08 to 2.3 equivalent ratio, 1:1.1 to 2.25 equivalent ratio, or 1:1.1 to 2.2 equivalent ratio.

[0056] By ensuring that the reaction temperature, reaction time, and reaction ratio are within the above ranges, polyhydroxyalkanoate can be easily converted into a non-cyclic amide compound, thereby producing methylpyrrolidone in a high yield.

[0057] The amine compound is not particularly limited as long as it is a compound that can depolymerize polyhydroxyalkanoate. Specifically, the amine compound may contain a compound selected from the group consisting of monomethylamine, an aqueous monomethylamine solution, dimethylamine, ammonia, and aqueous ammonium. When the amine compound contains the above compound, the selectivity and yield of the conversion of the non-cyclic amide compound to methylpyrrolidone can be increased.

[0058] The amine compound may be in a gaseous state or in the form of an aqueous solution (concentration: 25 to 40% by weight).

[0059] The amine compound may have a vapor density of 0.52 to 1.65, specifically 0.58 to 1.61, a boiling point of −40 to −2° C., specifically −33 to −6° C., and a pH of 10.8 to 11.8, specifically 11.2 to 11.5, but is not limited to these.

[0060] On the other hand, the acyclic amide compound obtained by the reaction of polyhydroxyalkanoate with an amine compound may include, but is not limited to, a compound selected from the group consisting of 4-hydroxy-N-methylbutanamide, 4-hydroxybutanamide, and 4-hydroxy-N-(2-hydroxyethyl)butanamide.

[0061] The non-cyclic amide compound may have a boiling point of 100 to 110°C or 150 to 160°C at 0.2 Torr and a boiling point of 230 to 250°C at normal pressure, but is not limited thereto.

[0062] By carrying out step (2), the method of the present disclosure has a high conversion rate of polyhydroxyalkanoate (the rate at which polyhydroxyalkanoate is converted to a non-cyclic amide compound) and high selectivity for the non-cyclic amide compound, thereby enabling the production of methylpyrrolidone in a high yield.

[0063] Specifically, according to the present disclosure, the conversion rate of polyhydroxyalkanoate can be, but is not limited to, 80% or more, 82% or more, 84% or more, 86% or more, 88% or more, or 90% or more (e.g., 80 to 100%, 83 to 100%, 85 to 100%, or 90 to 99.9%).

[0064] Furthermore, according to the present disclosure, the selectivity of the acyclic amide compound may be, for example, 90% or more, 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more (e.g., 90 to 100%, 92 to 100%, 94 to 99.9%, or 97 to 99.9%), but is not limited thereto.

[0065] According to the present disclosure, the yield of the acyclic amide compound may be, but is not limited to, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, or 90% or more (e.g., 50 to 100%, 70 to 100%, 85 to 99.9%, or 90 to 99.9%).

[0066] Step (3): Heating the acyclic amide compound According to the present disclosure, step (3) involves heating the acyclic amide compound under relatively high temperature and pressure conditions. Specifically, the acyclic amide compound is heated under high temperature and pressure conditions to cause a cyclocondensation reaction to produce methylpyrrolidone.

[0067] The heating temperature of the non-cyclic amide compound may be 200°C or higher, specifically 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, or 250°C or higher (e.g., 200 to 300°C, 210 to 290°C, 220 to 280°C, 230 to 275°C, 235 to 270°C, 240 to 260°C, or 245 to 255°C), but is not limited to these.

[0068] Furthermore, the initial pressure (set pressure) when heating the acyclic amide compound may be 1 to 80 bar, specifically, 1 to 75 bar, 1 to 70 bar, 1 to 65 bar, 3 to 60 bar, 5 to 60 bar, or 10 to 60 bar, but is not limited to these.

[0069] Furthermore, the difference (P2-P1) between the initial pressure (P1) for heating the acyclic amide compound and the equilibrium pressure (P2) after one hour of heating may be 15 bar or more. Specifically, the pressure difference (P2-P1) may be 16 bar or more, 17 bar or more, 18 bar or more, 20 bar or more, 23 bar or more, or 25 bar or more, and 100 bar or less, 90 bar or less, 80 bar or less, or 70 bar or less (for example, 15 to 100 bar, 17 to 95 bar, 19 to 90 bar, 20 to 85 bar, 25 to 80 bar, or 27 to 75 bar), but is not limited thereto.

[0070] The heating time of the non-cyclic amide compound may be 1 to 8 hours, specifically 1 to 7 hours, 2 to 6 hours, 2 to 5 hours, or 3 to 4 hours, but is not limited to these.

[0071] When the heating temperature, initial pressure, pressure difference (P2-P1), and heating time are each within the above ranges, the reaction stability of the acyclic amide compound is ensured, and the acyclic amide compound is easily converted into methylpyrrolidone, thereby enabling the production of methylpyrrolidone in high yield.

[0072] When methylpyrrolidone is produced as in step (3), specifically when step (3) is a step of producing methylpyrrolidone by heating an acyclic amide compound, the method of the present disclosure has a high conversion rate of the acyclic amide compound (the rate at which the acyclic amide compound is converted to methylpyrrolidone) and high selectivity for methylpyrrolidone, thereby enabling the production of methylpyrrolidone in a high yield.

[0073] Specifically, according to the present disclosure, the conversion rate of the acyclic amide compound can be, but is not limited to, 90% or more, 92% or more, 95% or more, 97% or more, 99% or more, or 99.9% or more (e.g., 90 to 100%, 92 to 100%, 95 to 100%, 98 to 100%, or 99.9 to 100%).

[0074] Furthermore, according to the present disclosure, the selectivity of methylpyrrolidone may be, but is not limited to, 85% or more, 88% or more, 90% or more, 92% or more, 95% or more, 97% or more, 99% or more, or 99.9% or more (e.g., 85-100%, 88-100%, 90-100%, 95-99.9%, or 99-99.9%).

[0075] Furthermore, according to the present disclosure, the yield of methylpyrrolidone may be, but is not limited to, 90% or more, 91% or more, 92% or more, 94% or more, 96% or more, 98% or more, 99% or more, or 99.9% or more (e.g., 90-100%, 91-100%, 92-100%, 95-99.9%, or 99-99.9%).

[0076] Methylpyrrolidone The methylpyrrolidone according to the present disclosure is prepared by the above-described preparation method. That is, according to the present disclosure, by preparing methylpyrrolidone using polyhydroxyalkanoate, it is possible to provide high-purity methylpyrrolidone in a high yield, in an environmentally friendly and economical manner.

[0077] Specifically, according to the present disclosure, the methylpyrrolidone may be highly pure, at least 87% or more, 90% or more, 92% or more, 95% or more, or 98% or more (e.g., 87-99.9%, 87-99%, or 87-98%).

[0078] Additionally, methylpyrrolidone may contain less than 0.1% by weight of 2-pyrrolidone as a by-product.

[0079] The methylpyrrolidone according to the present disclosure can be usefully used in various fields such as the electrical and electronic field, the energy field (e.g., secondary batteries), the chemical field (e.g., organic synthesis, organic solvents), and the paint field (e.g., detergents, additives).

[0080] Mode of Invention The present disclosure will be explained in more detail below by way of examples, but the scope of the present disclosure is not limited to these examples.

[0081] [Reagents and analytical equipment] Chloroform (>99.5%; Daejong Chemical and Metals Co.), methanol (EP grade; Daejong Chemical and Metals Co.), ethanol (GR grade; Duksun Pure Chemicals Co.), acetonitrile (HPLC grade; Burdick & Jackson Co.), and monomethylamine (40 wt% aqueous solution; Samchung Pure Chemical Co.) were used as reagents in the examples, comparative examples, and test examples.

[0082] The analytical instruments used were high performance liquid chromatography (HPLC) and gas chromatography.

[0083] Specifically, an Agilent Technologies 1260 Infinity system was used as the HPLC system, and an Osaka Soda Capcell Pak C18 MG (4.6 mm × 250 mm × 5 μm, P / N 92635) column was used. The autosampler temperature was set to 15°C, the column temperature to 35°C, and the mobile phase solvent was triple-distilled water containing 0.2% phosphoric acid and acetonitrile (ACN). Analysis was performed by gradient elution at a mobile phase flow rate of 1 ml / min.

[0084] The GC used was a GC (Agilent Technologies, 8890) equipped with a DB-WAX (60 m × 250 μm × 0.25 μm) column. The inlet temperature was 250 °C, the flow rate was 1 ml / min, and the FID (Flame Ionization Detector) temperature was 300 °C for analysis.

[0085] [Example 1] Preparation (purification) of poly-4-hydroxybutyrate (P4HB) 300 ml of bacterial culture containing poly-4-hydroxybutyrate (P4HB) was placed in a centrifuge and centrifuged at 3000 rpm for 5 minutes, and the supernatant was removed. Next, 300 ml of primary distilled water was added, and the cells were dissociated by stirring and centrifuged again. The supernatant was again removed, and 150 g of chloroform was added. The mixture was stirred at 45°C for 2 hours using a mechanical stirrer. The supernatant was then removed, and the chloroform layer was slowly added to excess ethanol (EtOH) to precipitate P4HB. The EtOH and chloroform were then removed by drying, yielding a P4HB precipitate. The resulting P4HB precipitate was a white solid, and its purity was confirmed to be 99%.

[0086] Preparation of 4-hydroxy-N-methylbutanamide (4HBA) [ka]

[0087] A 48 mL screw-cap sealed tube was charged with 0.2 g (1 equivalent) of the purified P4HB and 0.2 g (1.1 equivalents) of monomethylamine (MMA, 40 wt% aqueous solution), and the mixture was stirred at 300 rpm. The mixture was then reacted at 120°C for 6 hours to produce 4HBA.

[0088] [Examples 2 to 10 and Comparative Examples 1 to 9] 4HBA was prepared in the same manner as in Example 1, except that the reaction temperature and time of the mixture of P4HB and MMA, and the equivalent ratio of P4HB to MMA were changed as shown in Table 1 below.

[0089] [Test Example 1] In Examples 1 to 10 and Comparative Examples 1 to 9, the P4HB remaining after the preparation of 4HBA was separated using a paper filter and then weighed to calculate the conversion rate of P4HB. The results are shown in Table 1 below. The selectivity and yield of 4HBA in the reaction solution were also analyzed using HPLC (high performance liquid chromatography) and calculated using the following formula. The results are shown in Table 1 below. [Number 1] 4HBA selectivity (%) = (moles of 4HBA produced / moles of 4HB in converted P4HB) × 100 [Number 2] 4HBA yield (%) = P4HB conversion rate × 4HBA selectivity

[0090] [Table 1]

[0091] Referring to Table 1 above, in the present disclosure, by reacting a mixture of P4HB and MMA at a temperature of 110°C or higher (Examples 1 to 10), the P4HB conversion rate and 4HBA selectivity were increased, and 4HBA could be obtained in a high yield. On the other hand, when a mixture of P4HB and MMA was reacted at a low temperature of 90°C or lower, the P4HB conversion rate and 4HBA selectivity decreased, and the yield of 4HBA decreased.

[0092] [Example 11] Preparation of NMP The 4HBA obtained in Example 4 was dried in a vacuum dryer (BF-60VO, Biofree) at 50°C for 16 hours, and 20 g was placed in a high-temperature, high-pressure reaction vessel (R-101 Model High Pressure Bomb System, Chemesis). The initial pressure (P1) was adjusted to atmospheric pressure (1 bar), and the reaction was carried out at 250°C for 3 hours. After the reaction had been carried out for 1 hour, the equilibrium pressure (P2) was measured. After the reaction was completed, the product was diluted with methanol and recovered to obtain N-methyl-2-pyrrolidone (NMP).

[0093] [Examples 12 to 15] NMP was prepared according to the same procedure as in Example 11, except that the initial pressure was adjusted by injecting nitrogen as shown in Table 2 below.

[0094] [Comparative Example 10] NMP was prepared in the same manner as in Example 11, except that 4HBA obtained in Comparative Example 6 was used.

[0095] [Test Example 2] In Examples 11 to 15 and Comparative Example 10, the 4HBA remaining after the preparation of NMP was separated using a paper filter, and then weighed to calculate the conversion rate of 4HBA. The results are shown in Table 2 below. The selectivity and yield of NMP were analyzed using gas chromatography (GC) and calculated using the following formula. The results are shown in Table 2 below. [Number 3] NMP selectivity (%) = (moles of NMP produced / moles of 4HBA converted) × 100 [Number 4] NMP yield (%) = 4HBA conversion rate × NMP selectivity

[0096] [Table 2]

[0097] Referring to Table 2 above, in the present disclosure, 4HBA was reacted under relatively high temperature and pressure conditions, resulting in high 4HBA conversion and NMP selectivity, and enabling NMP to be obtained in high yield.

Claims

1. (1) preparing a polyhydroxyalkanoate; (2) reacting the polyhydroxyalkanoate with an amine compound at 110 to 180°C to prepare a non-cyclic amide compound; and (3) heating the non-cyclic amide compound; Method for preparing methylpyrrolidone.

2. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (1), the polyhydroxyalkanoate contains repeating units derived from 4-hydroxybutyric acid (4HB).

3. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (2), the amine compound comprises a compound selected from the group consisting of monomethylamine, an aqueous monomethylamine solution, dimethylamine, ammonia, and aqueous ammonium.

4. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: In the step (2), the polyhydroxyalkanoate and the amine compound are reacted at an equivalent ratio of 1:1.01 to 1:2.

5.

5. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (2), the reaction time between the polyhydroxyalkanoate and the amine compound is 10 hours or less.

6. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (2), the non-cyclic amide compound comprises a compound selected from the group consisting of 4-hydroxy-N-methylbutanamide, 4-hydroxybutanamide, and 4-hydroxy-N-(2-hydroxyethyl)butanamide.

7. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (3), the non-cyclic amide compound is heated to a temperature of 200°C or higher.

8. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (3), the initial pressure for heating the non-cyclic amide compound is 1 to 80 bar.

9. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: In the step (3), the initial pressure (P １ ) and the equilibrium pressure after 1 hour of heating (P ２ ) and the difference (P ２ -P １ ) is 15 bar or more.

10. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (3), the non-cyclic amide compound is heated for 1 to 8 hours.

11. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (2), the conversion rate of the polyhydroxyalkanoate is 80% or more and the selectivity for the non-cyclic amide compound is 90% or more.

12. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein in the step (3), the conversion rate of the non-cyclic amide compound is 90% or more.

13. 10. A method for preparing methylpyrrolidone according to claim 1, comprising: The method, wherein the yield of methylpyrrolidone is 90% or more.

14. Methylpyrrolidone prepared by the method according to any one of claims 1 to 13.

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