Method for manufacturing diol

Abstract

The present invention provides a method for producing a diol having good hue and capable of reducing unsaturated aliphatic hydrocarbons. The diol production method comprises: a) supplying metaboric acid, saturated aliphatic hydrocarbons, and a reaction gas containing molecular oxygen to a reactor; in the presence of metaboric acid, liquid-phase oxidizing the saturated aliphatic hydrocarbons with the reaction gas containing molecular oxygen to obtain a reaction liquid containing an oxide; b) esterifying the oxide to obtain a reaction liquid containing a borate ester compound; c) distilling the reaction liquid containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbons and a distillation residue; d) hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer; e) saponifying the organic layer with alkali to separate it into an alkaline aqueous solution layer and a crude alcohol layer; f) subjecting the crude alcohol layer to a first distillation to remove monohydric alcohol, and subjecting the remaining residual liquid to a second distillation at a temperature below 250°C and a retention time of less than 60 minutes.

Description

Technical Field

[0001] The present invention relates to a method for producing diols. Background Art

[0002] Secondary alcohols are useful as raw materials for synthetic detergents, surfactants, plasticizers, and the like. Regarding secondary alcohols, the following technology is known: in the presence of metaboric acid and a saturated aliphatic hydrocarbon, an oxidation reaction step involving the introduction of a molecular oxygen-containing reaction gas is performed to obtain a borate ester compound, which is then subjected to a hydrolysis step and a saponification step to obtain the secondary alcohol (for example, Patent Document 1).

[0003] However, it is known that diols of secondary alcohols are also useful as additives for surfactants, and that they can be obtained by distillation from an alcohol mixture obtained in a secondary alcohol production process (Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 56-131531

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 48-34807 Summary of the Invention

[0008] However, it was found that the diol produced by the conventional technology had a poor hue or contained a large amount of unsaturated aliphatic hydrocarbons.

[0009] Therefore, an object of the present invention is to provide a method for producing a diol having good hue and capable of reducing unsaturated aliphatic hydrocarbons.

[0010] One embodiment for solving the above-mentioned problems is a method for producing a diol, which includes: a) supplying metaboric acid, a saturated aliphatic hydrocarbon and a reaction gas containing molecular oxygen to a reactor, and in the presence of metaboric acid, liquid-phase oxidizing the saturated aliphatic hydrocarbon with the reaction gas containing molecular oxygen to obtain a reaction liquid containing an oxide; b) esterifying the above-mentioned oxide to obtain a reaction liquid containing a borate ester compound; c) distilling the above-mentioned reaction liquid containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbon and a distillation residue; d) hydrolyzing the above-mentioned distillation residue to separate it into orthoboric acid and an organic layer; e) saponifying the above-mentioned organic layer with alkali to separate it into an alkaline aqueous solution layer and a crude alcohol layer; and f) performing a first distillation on the above-mentioned crude alcohol layer to remove the monohydric alcohol, and then performing a second distillation on the remaining residual liquid at a temperature below 250°C and a residence time below 60 minutes.

[0011] According to the present invention, a method for producing an unsaturated aliphatic hydrocarbon diol having good hue and capable of reducing the amount of the unsaturated aliphatic hydrocarbon diol can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram showing the step (f) of the present invention is shown. DETAILED DESCRIPTION

[0013] The present invention will be described below. It should be noted that the present invention is not limited to the following embodiments. Unless otherwise specified, operations and measurements of physical properties were performed at room temperature (20 to 25°C).

[0014] One embodiment of the present invention is a method for producing a diol, comprising: a) supplying metaboric acid, a saturated aliphatic hydrocarbon, and a molecular oxygen-containing reaction gas to a reactor; and subjecting the saturated aliphatic hydrocarbon to liquid-phase oxidation with the molecular oxygen-containing reaction gas in the presence of metaboric acid to produce a reaction liquid containing an oxide; b) esterifying the oxide to produce a reaction liquid containing a borate ester compound; c) distilling the reaction liquid containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbon and a distillation residue; d) hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer; e) saponifying the organic layer with an alkali to separate it into an alkaline aqueous solution layer and a crude alcohol layer; and f) subjecting the crude alcohol layer to a first distillation to remove monohydric alcohol, and then subjecting the remaining residual liquid to a second distillation under conditions of a temperature below 250°C and a retention time of less than 60 minutes. This embodiment provides a method for producing a diol having good hue and reducing unsaturated aliphatic hydrocarbons.

[0015] Hereinafter, each step will be described in detail.

[0016] (Step (a))

[0017] ((a) Step: Oxidation Reaction Step)

[0018] In step (a), metaboric acid, saturated aliphatic hydrocarbons and a reaction gas containing molecular oxygen (also referred to as "oxygen" in this specification) are supplied to a reactor. In the presence of metaboric acid, the saturated aliphatic hydrocarbons are liquid-phase oxidized using the reaction gas containing molecular oxygen to obtain a reaction liquid containing oxides.

[0019] Saturated aliphatic hydrocarbons are mixtures of saturated aliphatic hydrocarbons (normal paraffins) having 8 to 30 carbon atoms. Preferably, the saturated aliphatic hydrocarbons are mixtures containing saturated aliphatic hydrocarbons having 10 to 15 carbon atoms (n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane and n-pentadecane) as the main components, and more preferably, mixtures containing saturated aliphatic hydrocarbons having 12 to 14 carbon atoms (n-dodecane, n-tridecane and n-tetradecane) as the main components. Here, “containing saturated aliphatic hydrocarbons as the main component” means that the saturated aliphatic hydrocarbons having a specified number of carbon atoms are contained in a ratio exceeding 90% by mass (preferably exceeding 95% by mass) (upper limit: 100% by mass) relative to all saturated aliphatic hydrocarbons. In addition, the average molecular weight of the saturated aliphatic hydrocarbons is greater than 114 and less than 422, preferably greater than 142 and less than 212, and more preferably greater than 170 and less than 198. The saturated aliphatic hydrocarbons may be synthetic or commercially available. Similarly, metaboric acid may also be synthetic or commercially available.

[0020] In step (a), the molecular oxygen-containing gas contains nitrogen in addition to molecular oxygen (oxygen). Preferably, the molecular oxygen-containing gas is composed of molecular oxygen (oxygen) and nitrogen. Furthermore, the molecular oxygen (oxygen) concentration in the molecular oxygen-containing gas is, but is not limited to, 1% by volume (vol%) or higher and 10% by volume (vol%) or lower, preferably 3% by volume (vol%) or higher and 5% by volume (vol%) or lower. The molecular oxygen-containing gas is supplied at a rate of, but is not limited to, 100 to 1000 liters / hour, preferably 350 to 600 liters / hour, relative to 1000 g of saturated aliphatic hydrocarbons.

[0021] In the above-mentioned step (a), the reaction mixing ratio of metaboric acid and saturated aliphatic hydrocarbon is not particularly limited. The amount of metaboric acid relative to the saturated aliphatic hydrocarbon is preferably 1% by mass or more and 5% by mass or less, more preferably 2% by mass or more and 4% by mass or less, etc., but is not limited thereto.

[0022] There is no particular limitation on the liquid phase oxidation reaction conditions, and the same conditions as before can be applied. For example, the liquid phase oxidation reaction temperature is 100 to 250°C, preferably 140 to 200°C, etc., but not limited thereto. In addition, the liquid phase oxidation reaction time is, for example, 0.5 to 5 hours, preferably 1 to 3 hours, etc., but not limited thereto. Under such conditions, saturated aliphatic hydrocarbons can be liquid-phase oxidized using a molecular oxygen-containing gas within an appropriate range (for example, the conversion rate of saturated aliphatic hydrocarbons = 5 to 30%). The above-mentioned liquid phase oxidation reaction can be carried out under atmospheric pressure (normal pressure), under pressure or under reduced pressure, usually at atmospheric pressure (normal pressure) to 30 kg / cm 2 G. In addition, the liquid phase oxidation reaction may be carried out while stirring (the reactor may be equipped with a stirrer).

[0023] In the above step (a), the liquid-phase oxidation reaction may be carried out in a single reactor or may be carried out continuously in two or more reactors. The reactor may be, for example, a stirred tank type or a bubble column type.

[0024] ((b) Step: Esterification Step)

[0025] In step (b), the oxide (oxidation reaction product) is esterified to obtain a reaction solution containing a borate ester compound.

[0026] In step (b), a borate ester compound is produced, but unreacted aliphatic hydrocarbons, free alcohol, and metaboric acid are also present. The boiling point of the free alcohol is close to that of the unreacted saturated aliphatic hydrocarbons, making separation of the two difficult. Therefore, in the esterification step (b), the alcohol is orthoborated to form a borate ester compound.

[0027] That is, in the above-mentioned step (b), the free alcohol contained in the oxidation reaction product obtained in the above-mentioned step (a) is esterified (orthoborated) to obtain a borate compound. In this step, the free alcohol present in the oxidation reaction product obtained in the step (a) is reacted with metaboric acid to be converted into a borate compound. Usually, there is residual metaboric acid in the oxidation reaction product, so there is no need to add new metaboric acid here, but sometimes new metaboric acid is added. The method for converting to a borate compound is not particularly limited. It is preferred to subject the reaction solution containing the oxide obtained in the step (a) to a decompression treatment. Thus, a borate compound can be obtained by esterification using free alcohol and excess added metaboric acid (or newly added metaboric acid). The conditions for the esterification are not particularly limited. In one embodiment of the present invention, the pressure in the step (b) is, for example, 50 to 200 hPa, preferably 90 to 170 hPa, etc. It should be noted that, in this specification, the pressure in the esterification step refers to the value of the pressure measured by a pressure gauge provided on the upper part of the reactor to measure the pressure of the gas phase. In this specification, the same definitions apply to all. In one embodiment of the present invention, the temperature in the process (b) is, for example, 100 to 220°C, preferably 160 to 180°C, etc. It should be noted that, in this specification, the temperature in the esterification process refers to the value of the temperature measured by a thermometer inserted into the liquid in the reactor. In this specification, the same definitions apply to all. In one embodiment of the present invention, the treatment time in the process (b) is, for example, 5 to 80 minutes, preferably 20 to 60 minutes, etc. In this specification, the treatment time in the reaction refers to the residence time in the reactor. Here, the residence time generally refers to the time that a substance flowing into a limited space stays in the space. If the volume of the space is set to V (m 3 ), the volume flow rate of the inflowing material is set to θ(m 3 / hr), the residence time (τ) is expressed by the following formula.

[0028]

Mathematical formula 1

[0029] τ(hr)=V / θ

[0030] It should be noted that the above-mentioned steps (a) to (b) include the following reactions.

[0031]

Chemical Formula 1

[0032]

[0033] (Step (c): Recovery of Unreacted Saturated Aliphatic Hydrocarbons)

[0034] In step (c), the reaction liquid containing the borate ester compound obtained in step (b) is distilled to separate unreacted saturated aliphatic hydrocarbons (distillate) and a distillation residue (bottoms), and the unreacted saturated aliphatic hydrocarbons are recovered (unreacted saturated aliphatic hydrocarbon recovery step). Since the boiling point difference between the distillate and the bottoms is large, separation by distillation is easy.

[0035] In this step, the borate ester compound can be distilled by a known method such as simple distillation (eg, flash distillation) or molecular distillation, but is not particularly limited thereto. The distillation may be performed in one stage or in two or more stages.

[0036] In one embodiment of the present invention, the pressure in the step (c) is, for example, 1 to 50 hPa or 3 to 25 hPa. In this specification, the pressure of distillation refers to the value of the pressure measured by the pressure gauge installed at the top of the tower in order to measure the pressure of the gas phase. In this specification, the same definition applies throughout. In one embodiment of the present invention, the temperature in the step (c) is, for example, 130 to 250°C or 150 to 205°C. In this specification, the temperature of distillation refers to the value of the temperature measured by the thermometer inserted into the liquid at the bottom of the tower. In one embodiment of the present invention, the residence time in the step (c) is, for example, 1 to 205 minutes or 25 to 120 minutes. Here, in this specification, the residence time of distillation refers to the liquid holding amount (liquid volume) (m 3 ) divided by the amount of liquid extracted from the bottom of the distillation tower (m 3 In this specification, the same definitions apply to all.

[0037] The unreacted saturated aliphatic hydrocarbons recovered in this step can be reused (circulated) in the oxidation reaction step (a). In this case, for example, after removing the saturated aliphatic hydrocarbons from the distillate, the hydrocarbons can be directly reused in the oxidation reaction step (a); after hydrogenating the carbonyl compounds and olefins contained in the saturated aliphatic hydrocarbons recovered in this step, the hydrocarbons can be reused in the oxidation reaction step (a); or, as described in Japanese Patent Application Laid-Open No. 56-131531, the saturated aliphatic hydrocarbons recovered in this step can be contacted with an alkaline aqueous solution to separate into an organic layer containing fatty acids and fatty acid esters and an aqueous layer, and the organic layer can be washed with hot water as needed (alkali treatment step), the unreacted saturated aliphatic hydrocarbons contained in the organic layer can be hydrogenated (hydrogenation step), and the alcohol components contained in the unreacted saturated aliphatic hydrocarbons can be orthoborated (esterification step) before being reused in the oxidation reaction step (a). However, the present invention is not limited to the above.

[0038] (Step (d): Hydrolysis Step)

[0039] In step (d), the distillation residue separated in step (c) is hydrolyzed to separate into orthoboric acid and an organic layer.

[0040] Specifically, hot water is added to the distillation residue to hydrolyze it and separate it into an aqueous layer containing orthoboric acid and an organic layer. Here, the temperature (liquid temperature) of the hot water is 70 to 150°C, preferably 90 to 100°C, etc., but not limited to this. In addition, the amount of hot water added is 1 to 20 times the mass of the distillation residue, preferably 2 to 10 times the mass of the distillation residue, etc., but not limited to this. The hydrolysis time is 5 to 60 minutes, preferably 20 to 30 minutes, etc., but not limited to this. Under such conditions, the distillation residue can be fully hydrolyzed, and the aqueous layer containing orthoboric acid and the organic layer can be separated more efficiently.

[0041] (Step (e): Saponification Step)

[0042] In step (e), the organic layer separated in step (d) is saponified with alkali to separate into an alkaline aqueous solution layer and a crude alcohol layer (saponification step). This can remove organic acids and organic acid esters.

[0043] Here, as the alkali, for example, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, etc. can be used, but it is not limited thereto. In addition, after the saponification treatment using the above-mentioned alkali, water washing can be performed if necessary. The saponification conditions are not particularly limited, and the same conditions as before can be applied. For example, the saponification temperature is 120 to 160°C, preferably 135 to 145°C, etc., but it is not limited thereto. The saponification time is 30 to 120 minutes, preferably 50 to 90 minutes, etc., but it is not limited thereto. If it is such conditions, the saponification treatment can be carried out more efficiently. After the saponification treatment, the organic layer can be washed with water to remove the organic acid and organic acid ester.

[0044] (Step (f): Alcohol Purification Step)

[0045] In step (f), the crude alcohol layer is subjected to a first distillation to remove the monohydric alcohol, and the remaining residue is subjected to a second distillation at a temperature below 250°C and a retention time of less than 60 minutes. This can produce secondary alcohols and diols with good hue and reduced unsaturated aliphatic hydrocarbons.

[0046] Figure 1 Schematic diagram showing the process (f) of the present invention. Figure 1 As shown, in the above step (e), the crude alcohol layer (organic layer) 2 remaining after the alkaline aqueous solution layer is removed is introduced into the first distiller 11. Then, the first distillation is performed. In one embodiment of the present invention, the pressure of the first distillation is, for example, 1 to 45 hPa, for example, 2 to 30 hPa, or for example, 4 to 12 hPa.

[0047] Under these conditions, the oil can be appropriately separated according to boiling point range (for example, into a fraction with a boiling point range of 95°C or higher and lower than 120°C and a fraction with a boiling point range of 120-150°C), which are then distilled from the top of the column 3. In this case, the first fraction (the fraction with a boiling point range of 95°C or higher and lower than 120°C) is a mixture of small amounts of saturated aliphatic hydrocarbons, carbonyl compounds, and monohydric primary alcohols (monohydric alcohols). Meanwhile, the second fraction (the fraction with a boiling point range of 120-150°C) is a mixture of trace amounts of carbonyl compounds and secondary alcohols (monohydric alcohols).

[0048] Next, the liquid in the bottom 4 of the column, where the residual components are removed by rectification of the monohydric alcohol in the first distillation, is introduced into the second still 12. This liquid serves as the raw material for the second distillation. It should be noted that in one embodiment of the present invention, the raw material contains 70-98 mass%, 80-97 mass%, or 85-95 mass% of crude diol. In another embodiment of the present invention, the raw material contains 0.1-10 mass%, 0.5-7 mass%, or 1-5 mass% of an alkali component. As in this embodiment, even if a certain amount of alkali is present, it does not adversely affect the quality of the diol and is therefore not a problem. In other words, a water washing step before distillation is not required, and the presence of alkali is permitted. Therefore, in one embodiment of the present invention, a water washing step to reduce or remove alkali is not included between the first and second distillations. This embodiment can be expected to improve productivity. In one embodiment of the present invention, the raw material contains 1-20 mass%, 2-18 mass%, 2.5-13 mass%, or 4-10 mass% of heavy components. In one embodiment of the present invention, the total of the crude diol, the alkali component, and the heavy component is 100% by mass. Examples of the heavy component include triols, tetraols, and organic acid salts.

[0049] In one embodiment of the present invention, the temperature of the second distillation is 240° C. or less, 230° C. or less, 220° C. or less, lower than 220° C., 210° C. or less, 205° C. or less, lower than 205° C., 200° C. or less, 190° C. or less, 180° C. or less, 175° C. or less, 170° C. or less, or 165° C. or less. In one embodiment of the present invention, the temperature of the second distillation is 150° C. or more, 160° C. or more, 170° C. or more, 180° C. or more, 190° C. or more, 200° C. or more, or 210° C. or more.

[0050] In one embodiment of the present invention, the residence time of the second distillation (e.g., distillation using a simple still) is 50 minutes or less, 45 minutes or less, less than 45 minutes, 40 minutes or less, 35 minutes or less, 30 minutes or less, less than 30 minutes, 25 minutes or less, or 20 minutes or less. In one embodiment of the present invention, the residence time of the second distillation (e.g., distillation using a simple still) is 10 minutes or more, 20 minutes or more, 25 minutes or more, 30 minutes or more, or 45 minutes or more.

[0051] In one embodiment of the invention, the residence time of the second distillation (e.g., using a molecular still) is less than 50 minutes, less than 45 minutes, less than 45 minutes, less than 40 minutes, less than 35 minutes, less than 30 minutes, less than 30 minutes, less than 25 minutes, less than 20 minutes, less than 15 minutes, less than 15 minutes, less than 10 minutes, less than 8 minutes, less than 6 minutes or less than 4 minutes. In one embodiment of the invention, the residence time of the second distillation (e.g., using a molecular still) is more than 0.5 minutes, more than 1 minute, more than 2 minutes, more than 5 minutes, more than 10 minutes, more than 20 minutes, more than 25 minutes, more than 30 minutes or more than 45 minutes.

[0052] In one embodiment of the present invention, the pressure of the second distillation is 4-20 hPa, 5-18 hPa, 5-14 hPa, 5-12 hPa, 5-10 hPa or 6-8 hPa.

[0053] In one embodiment of the present invention, the second distillation is performed by simple distillation, the temperature is lower than 200° C., and the residence time is lower than 45 minutes.

[0054] In one embodiment of the present invention, the second distillation is performed by molecular distillation, the temperature is less than 220°C, and the residence time is less than 45 minutes. In this embodiment, the temperature is less than 205°C. In this embodiment, the residence time is less than 30 minutes. In this embodiment, the residence time is less than 15 minutes.

[0055] According to one embodiment of the present invention, a method for producing a diol is provided, comprising the following steps: a) supplying metaboric acid, a saturated aliphatic hydrocarbon, and a molecular oxygen-containing reaction gas to a reactor; and, in the presence of metaboric acid, subjecting the saturated aliphatic hydrocarbon to liquid-phase oxidation with the molecular oxygen-containing reaction gas to obtain a reaction liquid containing an oxide; b) esterifying the oxide to obtain a reaction liquid containing a borate ester compound; c) distilling the reaction liquid containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbon and a distillation residue; d) hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer; e) saponifying the organic layer with an alkali to separate it into an alkaline aqueous solution layer and a crude alcohol layer; f) subjecting the crude alcohol layer to a first distillation to remove the monohydric alcohol, and then subjecting the remaining residue to a second distillation under conditions below a predetermined heat load parameter. The predetermined heat load parameter can be calculated as the product of the distillation temperature (°C) and the residence time (minutes).

[0056] In one embodiment of the present invention, when a simple still is used for the second distillation, the heat load parameter is 9000 or less, 8000 or less, 7000 or less, 6000 or less, 5000 or less, or 4000 or less. In one embodiment of the present invention, when a simple still is used for the second distillation, the heat load parameter is 1000 or more, 2000 or more, 2500 or more, or 3000 or more.

[0057] In one embodiment of the present invention, when a molecular still is used for the second distillation, the heat load parameter is 9000 or less, 8000 or less, 7000 or less, 6000 or less, 5000 or less, 4000 or less, 3000 or less, 2000 or less, 1000 or less, 900 or less, 800 or less, or 700 or less. In one embodiment of the present invention, when a molecular still is used for the second distillation, the heat load parameter is 100 or more, 200 or more, 300 or more, 400 or more, 500 or more, 600 or more, 800 or more, 2000 or more, 2500 or more, or 3000 or more.

[0058] In one embodiment of the present invention, in step (f), as the first distillation and the second distillation, known methods such as simple distillation (eg, flash distillation) and molecular distillation can be used independently, but are not particularly limited thereto.

[0059] In one embodiment of the present invention, the simple distillation apparatus is composed of an evaporation tank, a condenser, a distillate receiver, a liquid feeding pump, and the like.

[0060] In one embodiment of the present invention, in step (f), the first distillation is performed by simple distillation (e.g., flash distillation), and the second distillation is also performed by simple distillation (e.g., flash distillation). This embodiment can efficiently achieve the desired effects of the present invention.

[0061] In one embodiment of the present invention, in step (f), the first distillation is performed by simple distillation (e.g., flash distillation), and the second distillation is performed by molecular distillation. This embodiment can further efficiently achieve the desired effects of the present invention.

[0062] In one embodiment of the present invention, the hue of the target diol (diol of a secondary alcohol) is preferably less than 100, 90 or less, 80 or less, 70 or less, or 60 or less. In one embodiment of the present invention, the hue of the target diol (diol of a secondary alcohol) is, for example, 40 or greater or 45 or greater. In this specification, hue values are compared with those of an APHA standard solution, specifically calculated using a method in accordance with JIS K 0071:2017. This method is also used for calculations in the Examples.

[0063] In one embodiment of the present invention, the iodine value of the diol (diol of secondary alcohol) as the target is preferably less than 17, less than 16, less than 15, less than 13 or less than 12. In one embodiment of the present invention, the iodine value of the diol (diol of secondary alcohol) as the target is, for example, 8 or more or 10 or more. Here, the iodine value is measured by the Wijers method (JIS K 0070 1992). This method is also used for measurement in the examples. If the iodine value is high, it can be determined that there are many unsaturated aliphatic hydrocarbons. Unsaturated aliphatic hydrocarbons are considered to be impurities and also have an adverse effect on color, thereby leading to a reduction in quality.

[0064] It should be noted that between the above-mentioned step (e) and the step (f), at least one step selected from a heavy matter separation step, an alkali treatment step (particularly a potassium hydroxide treatment step) and a light matter separation step may be performed according to a conventionally known method.

[0065] [Example]

[0066] The present invention will be described in more detail below with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples and Comparative Examples, and examples obtained by appropriately combining the technical means disclosed in the Examples are also within the scope of the present invention.

[0067] (Examples 1 to 9, Comparative Example 1)

[0068] 1000 g of a mixture of saturated aliphatic hydrocarbons having 12 to 14 carbon atoms and 25 g of metaboric acid were added to a 3 L cylindrical reactor, and a mixed gas having an oxygen concentration of 3.5 vol% and a nitrogen concentration of 96.5 vol% was blown into the reactor at a rate of 430 L per hour. The mixture was oxidized at 170° C. under normal pressure for 2 hours to obtain an oxidation reaction mixture (oxide) (oxidation reaction step). It should be noted that the average molecular weight of the mixture of saturated aliphatic hydrocarbons was 184, and the mixture contained saturated aliphatic hydrocarbons having 12 to 14 carbon atoms (n-dodecane, n-tridecane, and n-tetradecane) at a rate exceeding 95% by mass relative to the total mass of the mixture.

[0069] After the oxidation reaction, the reaction solution containing the oxide is decompressed and esterified with alcohol and excess boric acid to obtain a borate ester compound. This esterification is carried out at 105 hPa, 165° C., and 60 minutes (esterification step).

[0070] Next, the borate compound (borate mixture) was flashed at 200° C. and 7 hPa to remove unreacted saturated aliphatic hydrocarbons (unreacted saturated aliphatic hydrocarbon recovery step).

[0071] Next, the residual liquid was hydrolyzed with a large amount (twice the amount by mass of the residual liquid) of hot water at 95° C. for 25 minutes to separate into an aqueous layer containing orthoboric acid and an organic layer (hydrolysis step).

[0072] The obtained organic layer was saponified using sodium hydroxide at 140° C. for 80 minutes and then washed with water to remove the organic acid and the organic acid ester (alkaline aqueous solution layer) (saponification step).

[0073] like Figure 1 As shown, the crude alcohol layer (organic layer) 2 remaining after the alkaline aqueous solution layer is removed in the saponification step is introduced into a first still (simple still) 11 and fractionally distilled at 7 hPa. From the top 3, a first fraction having a boiling point range of 95°C to below 120°C and a second fraction having a boiling point range of 120-150°C are obtained. The first fraction (the fraction having a boiling point range of 95°C to below 120°C) is a mixture of small amounts of saturated aliphatic hydrocarbons, carbonyl compounds, and monohydric primary alcohols (monohydric alcohols). The second fraction (the fraction having a boiling point range of 120-150°C) is a mixture of small amounts of carbonyl compounds and secondary alcohols (monohydric alcohols), with the majority of the secondary alcohols being monohydric secondary alcohols. This is how the first distillation is performed.

[0074] Next, the liquid at the bottom 4 of the column, from which the residual components were removed by rectification of the monohydric alcohol in the first distillation, was introduced into a second still (simple still) 12, and this was used as the raw material liquid, and a second distillation was performed at the temperature, pressure, and residence time described in Table 1. The raw material liquid consisted of 90% by mass of crude diol, 2% by mass of an alkali component, and 8% by mass of heavy components (triol, tetraol, and organic acid salt).

[0075]

Table 1

[0076] Second still (simple distillation column)

[0077]

[0078] (Examples 10 to 15, Comparative Example 2)

[0079] The same operation as in Example 1 was carried out except that the second distiller (simple distiller) was replaced with a second distiller (molecular distiller) and the second distillation was carried out at the temperature, pressure, and residence time described in Table 2 below.

[0080]

Table 2

[0081] Second distiller (molecular distillation tower)

[0082]

[0083] As shown in Tables 1 and 2, it is suggested that the method of the Example is a method for producing diols having good hue and capable of reducing unsaturated aliphatic hydrocarbons. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] 1: Distiller,

[0086] 11: First distiller,

[0087] 12: Second still,

[0088] 2: (e) The crude alcohol layer (organic layer) remaining after removing the alkaline aqueous solution layer,

[0089] 3: The top of the first distiller,

[0090] 4: The bottom of the first distiller,

[0091] 5: The top of the second distiller,

[0092] 6: The bottom of the second still.

[0093] Hereinafter, aspects of the present invention will be summarized.

[0094] 1. A method for producing diol, comprising the following steps:

[0095] a) supplying metaboric acid, a saturated aliphatic hydrocarbon, and a reaction gas containing molecular oxygen to a reactor, and subjecting the saturated aliphatic hydrocarbon to liquid-phase oxidation with the reaction gas containing molecular oxygen in the presence of metaboric acid to obtain a reaction liquid containing an oxide;

[0096] b) esterifying the oxide to obtain a reaction solution containing a borate compound;

[0097] c) distilling the reaction solution containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbons and a distillation residue;

[0098] d) hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer;

[0099] e) saponifying the organic layer with alkali and separating it into an alkaline aqueous solution layer and a crude alcohol layer; and

[0100] f) subjecting the crude alcohol layer to a first distillation to remove monohydric alcohol, and then subjecting the remaining residual liquid to a second distillation under conditions of a temperature below 250° C. and a residence time below 60 minutes.

[0101] 2. The manufacturing method according to item 1, wherein the temperature is lower than 220°C.

[0102] 3. The production method according to 1 or 2, wherein the residence time is less than 45 minutes.

[0103] 4. The production method according to any one of 1 to 3, wherein the second distillation is performed by simple distillation, the temperature is lower than 200° C., and the residence time is lower than 45 minutes.

[0104] 5. The production method according to any one of 1 to 3, wherein the second distillation is performed by molecular distillation, the temperature is lower than 220° C., and the residence time is lower than 45 minutes.

[0105] 6. The production method according to any one of 1 to 5, wherein the conditions include a pressure of 4 to 15 hPa.

[0106] 7. The production method according to any one of 1 to 6, wherein the diol has a hue of less than 90.

[0107] 8. The production method according to any one of 1 to 7, wherein the diol has an iodine value of 15 or less.

[0108] 9. A diol having a hue of less than 90 and an iodine value of less than 15.

Claims

1. A method for producing diol, comprising the following steps: a) supplying metaboric acid, a saturated aliphatic hydrocarbon, and a reaction gas containing molecular oxygen to a reactor, and in the presence of metaboric acid, subjecting the saturated aliphatic hydrocarbon to liquid-phase oxidation with the reaction gas containing molecular oxygen to obtain a reaction liquid containing an oxide; b) esterifying the oxide to obtain a reaction solution containing a borate ester compound; c) distilling the reaction solution containing the borate ester compound to separate it into unreacted saturated aliphatic hydrocarbons and a distillation residue; d) hydrolyzing the distillation residue to separate it into orthoboric acid and an organic layer; e) saponifying the organic layer with alkali and separating it into an alkaline aqueous solution layer and a crude alcohol layer; and f) subjecting the crude alcohol layer to a first distillation to remove monohydric alcohol, and then subjecting the remaining residual liquid to a second distillation under conditions of a temperature below 250° C. and a residence time below 60 minutes, wherein the second distillation is performed by simple distillation or molecular distillation, wherein a heat load parameter calculated by the product of the distillation temperature and the residence time is 5850 or less for simple distillation and 615 or less for molecular distillation, wherein the unit of temperature is° C. and the unit of residence time is minutes. The iodine value of the diol is 14 or less.

2. The manufacturing method according to claim 1, wherein The temperature is below 220°C.

3. The manufacturing method according to claim 1 or 2, wherein: The residence time is less than 45 minutes.

4. The manufacturing method according to claim 1 or 2, wherein: The second distillation is performed by simple distillation, the temperature is less than 200°C, and the residence time is less than 45 minutes.

5. The manufacturing method according to claim 1 or 2, wherein: The second distillation is performed by molecular distillation, the temperature is lower than 220° C., and the residence time is lower than 45 minutes.

6. The manufacturing method according to claim 1 or 2, wherein: The conditions include a pressure of 4 to 15 hPa.

7. The manufacturing method according to claim 1 or 2, wherein: The diol has a hue of less than 90.

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