A method for producing 1,2-propanediol and its use

Abstract

This invention provides a method for preparing 1,2-propanediol and its application. The method includes: step (1): in the presence of an acidic catalyst and water, ring-opening of a first portion of propylene oxide to obtain an acid-catalyzed reaction solution containing 1,2-propanediol; step (2): in the presence of an alkaline catalyst and water, ring-opening of a second portion of propylene oxide to obtain an alkaline-catalyzed reaction solution containing 1,2-propanediol; step (3): mixing the obtained acid-catalyzed reaction solution and the alkaline-catalyzed reaction solution for a neutralization reaction to obtain a mixture containing 1,2-propanediol; wherein, the molar ratio of the first portion of propylene oxide to water in step (1) and the molar ratio of the second portion of propylene oxide to water in step (1) are each independently 1:1-5; using the method of this invention to prepare 1,2-propanediol requires only a lower water ratio to obtain a higher propylene oxide conversion rate and 1,2-propanediol content, and the wastewater volume is lower and the color is colorless after the reaction.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, and in particular to a method for preparing 1,2-propanediol and its application. Background Technology

[0002] 1,2-Propanediol is a very important chemical raw material and intermediate. Thanks to the ether oxygen bond and terminal hydroxyl group in its structure, 1,2-propanediol exhibits good amphiphilicity and is widely used in the food, pharmaceutical, and cosmetic industries. It is a high-performance, low-toxicity solvent.

[0003] The production processes of 1,2-propanediol can be divided into two types. One is the direct hydration process of propylene oxide, but this process has several problems: 1. High separation energy consumption and large wastewater volume. The hydration unit uses an increased water feed rate to improve the selectivity of 1,2-propanediol. The water-to-propylene oxide molar ratio (water ratio) is usually 20-25. This process generates a large amount of wastewater, requires a multi-effect distillation unit for separation, consumes a large amount of steam, and is extremely energy-intensive. The other method is the catalytic hydration of propylene oxide, which reduces the water ratio by adding a catalyst. Catalytic hydration is currently the most researched method, and the more mature processes mainly include liquid acid or alkali metal oxide catalysis. CN86107894A discloses a method for catalyzing the ring-opening of epoxides using a carboxylic acid-carboxylate composite catalyst. This method can effectively improve the reaction activity, but it produces a large amount of acidic wastewater. The literature (Organic Process Research & Development, 2001, 6(5):600-664) discloses a method for preparing propylene glycol by catalyzing the hydration of propylene oxide using sodium bicarbonate. Under the conditions of sodium bicarbonate concentration of 0.25 mol / L, reaction temperature of 94℃, and water ratio of 10, the reaction conversion rate is >99%, and the selectivity of propylene glycol can reach over 94%. However, this method also has the problem of a large amount of alkaline wastewater, and the propylene glycol is yellow in color. Therefore, developing a green propylene glycol production process to reduce wastewater discharge during production is of great practical significance for developing energy-saving and consumption-reducing propylene glycol production technology. Summary of the Invention

[0004] To address the problems in existing technologies where increasing the water ratio improves the conversion rate of propylene oxide and the selectivity of 1,2-propanediol, but generates a large amount of wastewater, and where using a catalyst to reduce the water ratio results in more acidic or alkaline wastewater and quality issues, this invention provides a method for preparing 1,2-propanediol. This method achieves high propylene oxide conversion and 1,2-propanediol selectivity with a low water ratio, while effectively reducing wastewater generation. Furthermore, the 1,2-propanediol prepared using this method is colorless and has excellent appearance quality.

[0005] The objective of this invention is mainly achieved through the following technical solutions.

[0006] In a first aspect, the present invention provides a method for preparing 1,2-propanediol, the method comprising:

[0007] Step (1): In the presence of an acidic catalyst and water, the first part of propylene oxide undergoes a ring-opening reaction to obtain an acid-catalyzed reaction solution containing 1,2-propanediol.

[0008] Step (2): In the presence of an alkaline catalyst and water, the second part of propylene oxide undergoes a ring-opening reaction to obtain an alkaline catalytic reaction solution containing 1,2-propanediol.

[0009] Step (3): Mix the acid-catalyzed reaction solution and the base-catalyzed reaction solution to obtain a mixture containing 1,2-propanediol.

[0010] In step (1), the molar ratio of propylene oxide to water in the first part and the molar ratio of propylene oxide to water in the second part of step (2) are each 1:1-5.

[0011] Preferably, in step (1), the molar ratio of the first part of propylene oxide to water is 1:1-3, more preferably 1:1-1.5.

[0012] Preferably, in step (2), the molar ratio of propylene oxide to water in the second part is 1:1-3, more preferably 1:1-1.5.

[0013] Preferably, in step (1), the molar ratio of the first part of propylene oxide to the acid catalyst is 1:0.0001-0.001, more preferably 1:0.0001-0.0006, more preferably 1:0.0001-0.0005, and even more preferably 1:0.0001-0.00015.

[0014] Preferably, in step (2), the molar ratio of the second part of propylene oxide to the alkaline catalyst is 1:0.0001-0.0005, more preferably 1:0.0003-0.0005, and even more preferably 1:0.00035-0.00045.

[0015] Preferably, the reaction conditions for the ring-opening reaction in step (1) include: a reaction temperature of 25-200℃, preferably 80-160℃, more preferably 130-160℃; a reaction pressure of 0.1-2.5 MPa, preferably 0.15-2 MPa, more preferably 1.8-2 MPa; and a reaction time of 1-6 h, preferably 2-4 h, more preferably 2-3 h.

[0016] Preferably, the ring-opening reaction in step (1) is carried out in an inert atmosphere.

[0017] Preferably, the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

[0018] Preferably, the reaction conditions for the ring-opening reaction in step (2) include: a reaction temperature of 25-180℃, preferably 60-120℃, more preferably 80-100℃; a reaction pressure of 0.1-2 MPa, preferably 0.1-1 MPa, more preferably 0.8-1 MPa; and a reaction time of 1-6 h, preferably 1-4 h, more preferably 3-4 h.

[0019] Preferably, the ring-opening reaction in step (2) is carried out in an inert atmosphere.

[0020] Preferably, the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

[0021] Preferably, the acidic catalyst is selected from inorganic acids or organic acids.

[0022] Preferably, the inorganic acid is selected from at least one of hydrochloric acid, hypochlorous acid, chlorite, chloric acid, perchloric acid, sulfuric acid, sulfurous acid, sulfurous acid, persulfate, thiosulfate, dithionic acid, pyrosulfuric acid, metasulfuric acid, phosphoric acid, phosphorous acid, hypophosphoric acid, metaphosphoric acid, orthophosphoric acid, diphosphoric acid, triphosphoric acid, peroxydiphosphoric acid, hydrofluoric acid, hypofluoride, hydrobromic acid, bromic acid, hypobromic acid, bromic acid, perbromic acid, iodic acid, hypoiodic acid, iodic acid, nitric acid, nitrous acid, fuming nitric acid, manganese acid, molybdic acid, tungstic acid, selenic acid, silicic acid, stannic acid, titanic acid, telluric acid, rhenium acid, arsenic acid, and boric acid.

[0023] Preferably, the organic acid is selected from formic acid, acetic acid, propionic acid, n-butyric acid, n-valeric acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, dodecylbenzenesulfonic acid, tetradecanoic acid, pentadecanoic acid, nonadecanoic acid, lauric acid, tartaric acid, isobutyric acid, isovaleric acid, isohexanoic acid, isoheptanoic acid, isononanoic acid, 2-ethylhexanoic acid, isodecanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, tetradecanoic acid, fumaric acid, maleic acid, terephthalic acid, 1,4-phenylenediacetic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 9 At least one of the following: 10-anthracite, 4,4'-biphenyldicarboxylic acid, methanesulfonic acid, ethylsulfonic acid, propylsulfonic acid, 1-butanesulfonic acid, 1-pentanesulfonic acid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, 1-octanesulfonic acid, 1-nonanesulfonic acid, 1-decanesulfonic acid, dodecylbenzenesulfonic acid, vinylsulfonic acid, aminosulfonic acid, taurine, hydroxyethylsulfonic acid, (±)-camphor-10-sulfonic acid, benzenesulfonic acid, chlorosulfonic acid, p-toluenesulfonic acid, 3-pyridinesulfonic acid, 2-naphthalenesulfonic acid, quinoline-8-sulfonic acid, methanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, 4,4'-biphenyldisulfonic acid, and 1,5-naphthalenedisulfonic acid.

[0024] Preferably, the alkaline catalyst is selected from inorganic bases or organic bases.

[0025] Preferably, the inorganic base is selected from at least one of ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, aluminum hydroxide, magnesium hydroxide, zirconium oxide, cerium hydroxide, strontium hydroxide, zinc hydroxide, cobalt hydroxide, palladium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, rubidium carbonate, strontium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, rubidium bicarbonate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

[0026] Preferably, the organic base is selected from methylamine, ethylamine, furfurylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, dodecylamine, tetradecylamine, hexadecylamine, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, diethylamine, triethylamine, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine, heptamethamine, octyldiamine, nonanediamine, decanediamine, o-phenylenediamine, p-phenylenediamine, isopropylamine, isobutylamine, and isopentylamine. At least one of the following: 2-ethylhexylamine, diisopropylamine, N,N-diisopropylethylamine, pyridine, 4-dimethylaminopyridine, morpholine, imidazole, oxazole, thiazole, pyrazine, pyrimidine, indole, indoleaniline, quinoline, diphenylamine, 1-naphthylamine, naphthalene-2,6-diamine, 1-anthramine, anthracene-2,6-diamine, [2,2'-bipyridine]-5,5'-diamine, N-tert-butylisopropylamine, dibenzylamine, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0027] Preferably, in step (3), before mixing the acid catalytic reaction solution and the base catalytic reaction solution, the acid catalytic reaction solution and the base catalytic reaction solution are cooled to 25-80°C, preferably 25-60°C, respectively.

[0028] Preferably, in step (3), the method of mixing the acid catalytic reaction solution and the base catalytic reaction solution includes: adding the base catalytic reaction solution to the acid catalytic reaction solution.

[0029] Preferably, the addition rate of the base catalytic reaction solution is 50-100 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution, more preferably 80-100 parts by weight / min.

[0030] Preferably, the method further includes step (4): the mixture containing 1,2-propanediol obtained in step (3) is subjected to dehydration, solid-liquid separation and fractionation treatment in sequence to obtain 1,2-propanediol.

[0031] Preferably, the dehydration conditions include: a dehydration pressure of 4-7 kPa, preferably 5-7 kPa; and a dehydration temperature of 50-90°C, preferably 60-90°C.

[0032] Preferably, the solid-liquid separation is performed by filtration.

[0033] Preferably, the pore size of the filter membrane used for filtration is 20-200 μm, and more preferably 100-150 μm.

[0034] Secondly, the present invention provides applications of the method described in the first aspect in the fields of basic chemicals, pharmaceuticals, cosmetics, and photocuring.

[0035] This invention relates to a method for preparing 1,2-propanediol and its application. The method of this invention can effectively reduce the amount of wastewater in the post-treatment process, significantly reduce the difficulty and cost of post-treatment, and at the same time, only a low water ratio is required to obtain a high propylene oxide conversion rate and 1,2-propanediol selectivity. The propylenediol is transparent and free of impurities. Detailed Implementation

[0036] The inventors of this invention discovered through research that when propylene oxide and water undergo a hydration reaction alone in the presence of an acidic or alkaline catalyst to obtain a reaction solution, subsequent processes require the addition of an alkali or acid to neutralize the reaction solution. However, the addition of an alkali or acid necessitates the preparation of an alkaline or acidic solution beforehand, which introduces additional water into the reaction solution, increasing the amount of wastewater. Furthermore, if an extremely concentrated alkaline or acidic solution is prepared, or if only an alkali or acid is added, uneven mixing or clumping may occur. Additionally, the solid salt produced after neutralization exhibits poor crystallization and small particle size, increasing the difficulty of filtration. Moreover, in industrial production, the hydration reaction of propylene oxide is carried out in a closed reaction vessel under high pressure and temperature. For safety reasons, acid or alkali is not directly added to the high-temperature, high-pressure closed reaction vessel for neutralization. Therefore, the reaction vessel must first be depressurized and cooled before additional heating is applied to accelerate the reaction. Dissolving 1,2-propanediol in alkali or acid is time-consuming, labor-intensive, and increases energy consumption. Furthermore, heating the reaction solution raises the temperature, potentially leading to product volatilization and ultimately affecting the quality (e.g., yellowing) and yield of 1,2-propanediol. Further research by the inventors revealed that propylene oxide and water are hydrated in specific molar ratios in the presence of acidic and alkaline catalysts, respectively. Since the acidic and alkaline catalysts are already dissolved in water before the reaction, the resulting acid-catalyzed and alkaline-catalyzed reaction solutions contain uniformly dispersed catalysts, with only a small amount of water present. Mixing the two reaction solutions achieves acid-base neutralization without introducing additional water. Moreover, the resulting solid salt particles are large, exhibit good crystallization, and are easier to filter and separate, ensuring the high quality of the obtained 1,2-propanediol, improving yield, and reducing wastewater volume.

[0037] Based on the above research, in a first aspect, the present invention provides a method for preparing 1,2-propanediol, the method comprising:

[0038] Step (1): In the presence of an acidic catalyst and water, the first part of propylene oxide undergoes a ring-opening reaction to obtain an acid-catalyzed reaction solution containing 1,2-propanediol.

[0039] Step (2): In the presence of an alkaline catalyst and water, the second part of propylene oxide undergoes a ring-opening reaction to obtain an alkaline catalytic reaction solution containing 1,2-propanediol.

[0040] Step (3): Mix the acid-catalyzed reaction solution and the base-catalyzed reaction solution to obtain a mixture containing 1,2-propanediol;

[0041] In step (1), the molar ratio of propylene oxide to water in the first part and the molar ratio of propylene oxide to water in the second part of step (2) are each 1:1-5.

[0042] In a preferred embodiment of the present invention, the molar ratio of the first part of propylene oxide to water in step (1) is 1:1-3, preferably 1:1-1.5.

[0043] In a preferred embodiment of the present invention, the molar ratio of propylene oxide to water in step (2) is 1:1-3, preferably 1:1-1.5.

[0044] In a preferred embodiment of the present invention, the molar ratio of the first part of propylene oxide to the acidic catalyst in step (1) is 1:0.0001-0.001, preferably 1:0.0001-0.0006, more preferably 1:0.0001-0.0005, and even more preferably 1:0.0001-0.00015. Using this preferred amount of acidic catalyst is beneficial to further improve the conversion rate of propylene oxide and the selectivity of 1,2-propanediol, and further reduce the amount of wastewater in the mixture.

[0045] In a preferred embodiment of the present invention, the molar ratio of the second part of propylene oxide to the alkaline catalyst in step (2) is 1:0.0001-0.0005, preferably 1:0.0003-0.0005, and more preferably 1:0.00035-0.00045. Using this preferred amount of acidic catalyst is beneficial to further improve the conversion rate of propylene oxide and the selectivity of 1,2-propanediol, and further reduce the amount of wastewater in the mixture.

[0046] In a preferred embodiment of the present invention, the pH value of the mixture containing 1,2-propanediol obtained in step (3) is 2-12, preferably 4-10.5, and more preferably 6-8. By using this preferred pH range, a high propylene oxide conversion rate and 1,2-propanediol selectivity are ensured, along with low wastewater volume and post-treatment difficulty, while also resulting in 1,2-propanediol of good quality.

[0047] In a preferred embodiment of the present invention, the reaction conditions for the ring-opening reaction in step (1) include: a reaction temperature of 25-200℃, preferably 80-160℃, more preferably 130-160℃; a reaction pressure of 0.1-2.5 MPa, preferably 0.15-2 MPa, more preferably 1.8-2 MPa; and a reaction time of 1-6 h, preferably 2-4 h, more preferably 2-3 h. Using these preferred reaction conditions can further improve the conversion rate of propylene oxide and the selectivity of 1,2-propanediol, and reduce the amount of wastewater in the mixture.

[0048] In a preferred embodiment of the present invention, the ring-opening reaction in step (1) is carried out in an inert atmosphere; the use of this preferred inert atmosphere can effectively reduce the generation of small molecule compounds such as peroxides, aldehydes and ketones during the reaction, and can effectively improve product quality.

[0049] In a more preferred embodiment of the present invention, the inert atmosphere is selected from at least one of nitrogen, helium, and argon, and more preferably nitrogen.

[0050] In a preferred embodiment of the present invention, the reaction conditions for the ring-opening reaction in step (2) include: a reaction temperature of 25-180℃, preferably 60-120℃, more preferably 80-100℃; a reaction pressure of 0.1-2 MPa, preferably 0.1-1 MPa, more preferably 0.8-1 MPa; and a reaction time of 1-6 h, preferably 1-4 h, more preferably 3-4 h. Using these preferred reaction conditions can further improve the conversion rate of propylene oxide and the selectivity of 1,2-propanediol, thereby reducing the amount of wastewater in the mixture.

[0051] In a preferred embodiment of the present invention, the ring-opening reaction in step (2) is carried out in an inert atmosphere; the use of this preferred inert atmosphere can effectively reduce the generation of small molecule compounds such as peroxides, aldehydes and ketones during the reaction, and can effectively improve product quality.

[0052] In a more preferred embodiment of the present invention, the inert atmosphere is selected from at least one of nitrogen, helium, and argon, and more preferably nitrogen.

[0053] In a preferred embodiment of the present invention, the acidic catalyst is selected from inorganic acids or organic acids.

[0054] In a more preferred embodiment of the present invention, the inorganic acid is selected from at least one of hydrochloric acid, hypochlorous acid, chlorite, chloric acid, perchloric acid, sulfuric acid, sulfurous acid, sulfurous acid, persulfate, thiosulfate, dithionite, pyrosulfuric acid, metasulfite, phosphoric acid, phosphorous acid, hypophosphoric acid, metaphosphoric acid, orthophosphoric acid, diphosphoric acid, triphosphoric acid, peroxydiphosphoric acid, hydrofluoric acid, hypofluoride, hydrobromic acid, bromic acid, hypobromic acid, bromic acid, perbromic acid, iodic acid, hypoiodic acid, iodic acid, nitric acid, nitrous acid, fuming nitric acid, manganese acid, molybdic acid, tungstic acid, selenic acid, silicic acid, stannic acid, titanic acid, telluric acid, rhenium acid, arsenic acid, and boric acid, more preferably boric acid or dithionite;

[0055] In a more preferred embodiment of the present invention, the organic acid is selected from formic acid, acetic acid, propionic acid, n-butyric acid, n-valeric acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, dodecylbenzenesulfonic acid, tetradecanoic acid, pentadecanoic acid, nonadecanoic acid, lauric acid, tartaric acid, isobutyric acid, isovaleric acid, isohexanoic acid, isoheptanoic acid, isononanoic acid, 2-ethylhexanoic acid, isodecanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, heptaic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, tetradecanoic acid, fumaric acid, maleic acid, terephthalic acid, 1,4-phenylenediacetic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 9,10 At least one of the following: anthracene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, methanesulfonic acid, ethylsulfonic acid, propylsulfonic acid, 1-butanesulfonic acid, 1-pentanesulfonic acid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, 1-octanesulfonic acid, 1-nonanesulfonic acid, 1-decanesulfonic acid, dodecylbenzenesulfonic acid, vinylsulfonic acid, aminosulfonic acid, taurine, hydroxyethylsulfonic acid, (±)-camphor-10-sulfonic acid, benzenesulfonic acid, chlorosulfonic acid, p-toluenesulfonic acid, 3-pyridinesulfonic acid, 2-naphthalenesulfonic acid, quinoline-8-sulfonic acid, methanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, 4,4'-biphenyldisulfonic acid, and 1,5-naphthalenedisulfonic acid, more preferably dodecylbenzenesulfonic acid or benzenesulfonic acid.

[0056] In a preferred embodiment of the present invention, the alkaline catalyst is selected from inorganic bases or organic bases.

[0057] In a more preferred embodiment of the present invention, the inorganic base is selected from at least one of ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, aluminum hydroxide, magnesium hydroxide, zirconium oxide, cerium hydroxide, strontium hydroxide, zinc hydroxide, cobalt hydroxide, palladium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, rubidium carbonate, strontium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, rubidium bicarbonate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate, more preferably cesium carbonate or dipotassium hydrogen phosphate.

[0058] In a more preferred embodiment of the present invention, the organic base is selected from methylamine, ethylamine, furfurylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, dodecylamine, tetradecylamine, hexadecylamine, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, diethylamine, triethylamine, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexamethylenediamine, heptanediamine, octylenediamine, nonanediamine, decanediamine, o-phenylenediamine, p-phenylenediamine, isopropylamine, isobutylamine, and isopentylamine. At least one of the following: 2-ethylhexylamine, diisopropylamine, N,N-diisopropylethylamine, pyridine, 4-dimethylaminopyridine, morpholine, imidazole, oxazole, thiazole, pyrazine, pyrimidine, indole, indoleaniline, quinoline, diphenylamine, 1-naphthylamine, naphthalene-2,6-diamine, 1-anthramine, anthracene-2,6-diamine, [2,2'-bipyridine]-5,5'-diamine, N-tert-butylisopropylamine, dibenzylamine, tetramethylammonium hydroxide, and tetraethylammonium hydroxide, more preferably sodium methoxide or aniline.

[0059] In a preferred embodiment of the present invention, in step (3), before mixing the acid catalytic reaction solution and the alkali catalytic reaction solution, the acid catalytic reaction solution and the alkali catalytic reaction solution are cooled independently to 25-80°C, preferably 25-60°C. If the temperature of the reaction solution is too high before mixing, it will lead to an increase in by-products. If the temperature of the reaction solution is too low, it will lead to uneven mixing and local acidity or alkalinity. The present invention performs this preferred cooling treatment before mixing, which can improve the neutralization rate and at the same time allow the mixture to be completely mixed without introducing wastewater, thus avoiding local acidity or alkalinity of the mixture after mixing.

[0060] In a preferred embodiment of the present invention, step (3) involves mixing the acid catalytic reaction solution and the base catalytic reaction solution by adding the base catalytic reaction solution to the acid catalytic reaction solution. Using this preferred mixing method, the 1,2-propanediol obtained by subsequent separation of the mixture has a lighter odor and a lower color value, i.e., the color is colorless and transparent or nearly colorless and transparent. Conversely, the 1,2-propanediol obtained by separation is yellowish and has a stronger odor.

[0061] In a more preferred embodiment of the present invention, the addition rate of the base catalytic reaction solution to the acid catalytic reaction solution is 50-100 parts by weight / min, more preferably 80-100 parts by weight / min, relative to 100 parts by weight of the acid catalytic reaction solution. Using this preferred addition rate results in larger solid salt particles and better crystallization, simplifying filtration and separation, and significantly improving production efficiency. Furthermore, this preferred addition rate avoids excessively high local reaction temperatures due to excessively rapid addition, which could lead to side reactions and affect product purity. It also avoids low production efficiency due to excessively slow addition rates.

[0062] To obtain a pure 1,2-propanediol product, the present invention requires further processing of the mixture. In a preferred embodiment, the method further includes step (4): the mixture containing 1,2-propanediol obtained in step (3) is subjected to dehydration, solid-liquid separation, and fractional distillation sequentially to obtain 1,2-propanediol. In step (4), a solution containing 1,2-propanediol is obtained through solid-liquid separation, and subsequent fractional distillation can be performed to separate the 1,2-propanediol as needed.

[0063] In this invention, step (4) also separates and obtains oligopropylene glycol, which includes at least one of dipropylene glycol, tripropylene glycol, tetrapropylene glycol and oligopolyol.

[0064] In a preferred embodiment of the present invention, the dehydration conditions include: a dehydration pressure of 4-7 kPa, preferably 5-7 kPa; and a dehydration temperature of 50-90°C, preferably 60-90°C. Using these preferred dehydration conditions, excess water in the mixture can be quickly removed, thereby improving production efficiency.

[0065] In this invention, the method of solid-liquid separation is not particularly limited, and the method of solid-liquid separation is selected from filtration separation or centrifugation separation, preferably filtration separation.

[0066] In a preferred embodiment of the present invention, the filter membrane used for filtration has a pore size of 20-200 μm, preferably 100-150 μm.

[0067] In this invention, the conditions for fractionation are not particularly limited, as long as 1,2-propanediol can be separated by fractionation. The fractionation step can be carried out using existing technology.

[0068] In this invention, there are no particular restrictions on the reaction equipment used for the contact reaction in steps (1) and (2). In a preferred embodiment, the reaction equipment includes at least one of a batch reactor, a tubular reactor, a fixed-bed reactor, and a tower reactor.

[0069] In this invention, there is no particular limitation on the material of the reaction device; any material conventionally used in the art can be used.

[0070] In this invention, there is no particular limitation on the order of steps (1) and (2). Step (1) can be performed first and then step (2), or step (2) can be performed first and then step (1), or steps (1) and (2) can be performed simultaneously.

[0071] Secondly, the present invention provides applications of the method described in the first aspect in the fields of basic chemicals, pharmaceuticals, cosmetics, and photocuring.

[0072] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0073] propylene oxide (PO) conversion rate = amount of propylene oxide participating in the reaction ÷ amount of propylene oxide in the raw material × 100%;

[0074] Product distribution was analyzed using the area normalization method in gas chromatography, and the chromatographic column used was an HP-FFAP polar capillary column.

[0075] Example 1

[0076] Step (1): Add 307 parts by weight of propylene oxide, 93 parts by weight of deionized water and 0.037 parts by weight of boric acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize to 0.2 MPa. Then turn on the stirrer and stir the reaction at 150°C for 2 hours to obtain the acid catalytic reaction solution. Cool the acid catalytic reaction solution to 25°C for later use.

[0077] Step (2): Add 493 parts by weight of propylene oxide, 307 parts by weight of deionized water and 0.067 parts by weight of cesium carbonate to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.4 MPa. Then turn on the stirrer and stir the reaction at 120°C for 4 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0078] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization to obtain a mixture containing 1,2-propanediol. The addition rate of the alkali catalytic reaction solution is 60 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.8. The product distribution is analyzed by gas chromatography.

[0079] Step (4): Remove the remaining water from the obtained mixture at 4 kPa and 55 °C. After the salt is precipitated, filter it with a filter membrane with a pore size of 200 μm to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. Separate the filtrate by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol).

[0080] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0081] Example 2

[0082] Step (1): Add 323 parts by weight of propylene oxide, 277 parts by weight of deionized water and 0.138 parts by weight of dithionic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.5 MPa. Then turn on the stirrer and stir the reaction at 80°C for 2 hours to obtain an acid catalytic reaction solution. Cool the acid catalytic reaction solution to 25°C for later use.

[0083] Step (2): Add 453 parts by weight of propylene oxide, 147 parts by weight of deionized water and 0.158 parts by weight of potassium dihydrogen phosphate to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.5 MPa. Then turn on the stirrer and stir the reaction at 130°C for 4 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0084] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization. The addition rate of the alkali catalytic reaction solution is 60 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.9. The product distribution is analyzed by gas chromatography.

[0085] Step (4): The obtained mixture was subjected to a process of removing excess water at 7 kPa and 75 °C. After salt precipitation, the mixture was filtered through a 200 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0086] Example 3

[0087] Step (1): Add 614 parts by weight of propylene oxide, 186 parts by weight of deionized water and 0.335 parts by weight of dodecylbenzenesulfonic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.5 MPa. Then turn on the stirrer and stir the reaction at 120°C for 2 hours to obtain the acid catalytic reaction solution. Cool the acid catalytic reaction solution to 25°C for later use.

[0088] Step (2): Add 302 parts by weight of propylene oxide, 98 parts by weight of deionized water and 0.091 parts by weight of sodium methoxide to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize to 0.7 MPa. Then turn on the stirrer and stir the reaction at 100°C for 3 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0089] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization. The addition rate of the alkali catalytic reaction solution is 60 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.9. The product distribution is analyzed by gas chromatography.

[0090] Step (4): The obtained mixture was subjected to a process of removing excess water at 7 kPa and 75 °C. After salt precipitation, the mixture was filtered through a 200 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0091] Example 4

[0092] Step (1): Add 121 parts by weight of propylene oxide, 79 parts by weight of deionized water and 0.068 parts by weight of benzenesulfonic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.5 MPa. Then turn on the stirrer and stir the reaction at 120°C for 2 hours. After the reaction is completed, the acid catalytic reaction solution is obtained. Cool the acid catalytic reaction solution to 25°C for later use.

[0093] Step (2): Add 103 parts by weight of propylene oxide, 97 parts by weight of deionized water and 0.052 parts by weight of aniline to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.7 MPa. Then turn on the stirrer and stir the reaction at 100°C for 3 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0094] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization. The addition rate of the alkali catalytic reaction solution is 80 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.9. The product distribution is analyzed by gas chromatography.

[0095] Step (4): The obtained mixture was subjected to a process of removing excess water at 7 kPa and 75 °C. After salt precipitation, the mixture was filtered through a 200 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0096] Example 5

[0097] Step (1): Add 203 parts by weight of propylene oxide, 65 parts by weight of deionized water and 0.055 parts by weight of benzenesulfonic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 1.8 MPa. Then turn on the stirrer and stir the reaction at 130°C for 3 hours. After the reaction is completed, the acid catalytic reaction solution is obtained. Cool the acid catalytic reaction solution to 25°C for later use.

[0098] Step (2): Add 191 parts by weight of propylene oxide, 66 parts by weight of deionized water and 0.064 parts by weight of sodium methoxide to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize to 1 MPa. Then turn on the stirrer and stir the reaction at 100°C for 3 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0099] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization. The addition rate of the alkali catalytic reaction solution is 90 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.9. The product distribution is analyzed by gas chromatography.

[0100] Step (4): The obtained mixture was subjected to a process of removing excess water at 7 kPa and 75 °C. After salt precipitation, the mixture was filtered through a 200 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0101] Example 6

[0102] Step (1): Add 311 parts by weight of propylene oxide, 99 parts by weight of deionized water and 0.081 parts by weight of benzenesulfonic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize to 2 MPa. Then turn on the stirrer and stir the reaction at 160°C for 2 hours. After the reaction is completed, the acid catalytic reaction solution is obtained. Cool the acid catalytic reaction solution to 25°C for later use.

[0103] Step (2): Add 207 parts by weight of propylene oxide, 97 parts by weight of deionized water and 0.092 parts by weight of sodium methoxide to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 0.8 MPa. Then turn on the stirrer and stir the reaction at 80°C for 4 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0104] Step (3): Add 0.1-1 times the weight of the acid catalytic reaction solution to the acid catalytic reaction solution for neutralization. The addition rate of the alkali catalytic reaction solution is 80 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution. The pH value of the mixture is 6.9. The product distribution is analyzed by gas chromatography.

[0105] Step (4): The obtained mixture was subjected to a process of removing excess water at 7 kPa and 75 °C. After salt precipitation, the mixture was filtered through a 200 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0106] Example 7

[0107] 1,2-propanediol was prepared according to the method of Example 5, except that in step (1), the amount of deionized water used was 101 parts by weight; and in step (2), the amount of deionized water used was 98 parts by weight.

[0108] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0109] Example 8

[0110] 1,2-propanediol was prepared according to the method of Example 5, except that in step (1), the amount of deionized water used was 203 parts by weight; and in step (2), the amount of deionized water used was 190 parts by weight.

[0111] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0112] Example 9

[0113] 1,2-propanediol was prepared according to the method of Example 5, except that in step (1), the amount of acidic catalyst was 0.0115 parts by weight; and in step (2), the amount of alkaline catalyst was 0.0103 parts by weight.

[0114] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0115] Example 10

[0116] 1,2-Propanediol was prepared according to the method of Example 5, except that benzenesulfonic acid was replaced with an equimolar amount of sulfuric acid.

[0117] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0118] Example 11

[0119] 1,2-Propanediol was prepared according to the method in Example 5, except that sodium methoxide was replaced with an equimolar amount of sodium hydroxide.

[0120] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0121] Example 12

[0122] 1,2-propanediol was prepared according to the method of Example 5, except that in step (3), the addition rate of the base catalytic reaction solution was 200 parts by weight / min relative to 100 parts by weight of the acid catalytic reaction solution.

[0123] The distribution of reactants (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0124] Comparative Example 1

[0125] 1,2-propanediol was prepared according to the method of Example 4, except that only step (1) was performed to obtain the acid-catalyzed reaction solution; then, a 1 mol / L potassium hydroxide solution was added to neutralize it to a pH of 6.9, and the product distribution of the neutralized reaction solution was analyzed by gas chromatography.

[0126] The neutralized reaction solution was subjected to a process at 7 kPa and 75 °C to remove excess water. After salt precipitation, the solution was filtered through a 50 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0127] Comparative Example 2

[0128] 1,2-propanediol was prepared according to the method of Example 4, except that only step (2) was performed to obtain the alkaline catalytic reaction solution; then, 1 mol / L hydrochloric acid solution was added to neutralize to a pH of 6.9, and the product distribution of the neutralized reaction solution was analyzed by gas chromatography.

[0129] The neutralized reaction solution was subjected to a process at 7 kPa and 75 °C to remove excess water. After salt precipitation, the solution was filtered through a 50 μm pore size membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0130] Comparative Example 3

[0131] 650 parts by weight of propylene oxide and 200 parts by weight of deionized water were added to a stainless steel high-pressure reactor. The air inside the reactor was completely replaced with nitrogen and the pressure was increased to 0.5 MPa. Then, stirring was started and the reaction was carried out at 120°C for 2 hours to obtain a reaction solution. The solution was then cooled to 25°C for later use.

[0132] The reaction solution was subjected to a process at 7 kPa and 75 °C to remove excess water, followed by vacuum fractionation to separate pure 1,2-propanediol and oligomeric propylene glycols (dipropylene glycol monohydrate, tripropylene glycol dihydrate, and tetrapropylene glycol trihydrate). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0133] Comparative Example 4

[0134] 1,2-propanediol was prepared according to the method of Example 5, except that:

[0135] Step (1): Add 203 parts by weight of propylene oxide, 65 parts by weight of deionized water and 0.055 parts by weight of benzenesulfonic acid to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize it to 1.8 MPa. Then turn on the stirrer and stir the reaction at 130°C for 3 hours. After the reaction is completed, the acid catalytic reaction solution is obtained. Cool the acid catalytic reaction solution to 25°C for later use.

[0136] Step (3): Add 0.044 parts by weight of potassium hydroxide solid to the acid-catalyzed reaction solution to neutralize it to a pH of 6.9. Analyze the product distribution of the neutralized reaction solution by gas chromatography.

[0137] Step (4): The neutralized reaction solution was subjected to a 7 kPa and 75 °C temperature to remove the remaining water. After the salt was precipitated, it was filtered using a 10 μm pore size filter membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0138] Comparative Example 5

[0139] 1,2-propanediol was prepared according to the method of Example 5, except that:

[0140] Step (2): Add 191 parts by weight of propylene oxide, 66 parts by weight of deionized water and 0.064 parts by weight of sodium methoxide to a stainless steel high-pressure reactor. Replace the air in the high-pressure reactor with nitrogen and pressurize to 1 MPa. Then turn on the stirrer and stir the reaction at 100°C for 3 hours to obtain the alkaline catalytic reaction solution. Cool the alkaline catalytic reaction solution to 25°C for later use.

[0141] Step (3):

[0142] 0.055 parts by weight of hydrochloric acid were added to the alkaline catalytic reaction solution to neutralize it to a pH of 6.9. The product distribution of the neutralized reaction solution was analyzed by gas chromatography.

[0143] Step (4): The neutralized reaction solution was subjected to a 7 kPa and 75 °C temperature to remove the remaining water. After the salt was precipitated, it was filtered using a 10 μm pore size filter membrane to obtain a filtrate containing 1,2-propanediol and oligopropylene glycol. The filtrate was then separated by vacuum fractionation to obtain pure 1,2-propanediol and oligopropylene glycol (dipropylene glycol, tripropylene glycol, and tetrapropylene glycol). The reactant distribution (area ratio of 1,2-propanediol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol), wastewater volume, conversion rate, and color of 1,2-propanediol are shown in Table 1.

[0144] Table 1

[0145]

[0146]

[0147] Note: The wastewater volume and PO conversion rate values ​​in the examples and comparative examples in Table 1 are rounded to single digits.

[0148] As shown in Table 1, the preparation of 1,2-propanediol using the technical solution of the present invention not only results in low wastewater volume but also high propylene oxide conversion rate and a high proportion of 1,2-propanediol in the product distribution, i.e., high 1,2-propanediol selectivity. In particular, Examples 5 and 6, which employ the most preferred technical solutions, achieve a PO conversion rate of 100% and wastewater volume as low as approximately 15g (total wastewater per kilogram of product). The 1,2-propanediol content in the product distribution can reach over 92%, and the obtained product has excellent quality and is easy to separate into solid and liquid phases. This technology has the potential for large-scale implementation in industrial production.

[0149] Compared to Examples 7 and 8, where the ratio of propylene oxide to deionized water is not within the preferred range, Example 5 of the present invention has a lower wastewater generation because the molar ratio of propylene oxide to deionized water is within the preferred range of 1:1-1.5.

[0150] Compared to Example 9, where the molar ratio of propylene oxide to the acidic catalyst is in the range of 1:0.0001-0.001 and the molar ratio of propylene oxide to the basic catalyst is not in the range of 1:0.0001-0.0005, Example 5 of the present invention, where both the molar ratios of propylene oxide to the acidic catalyst and the molar ratio of propylene oxide to the basic catalyst are within the preferred range, has a lower wastewater volume and a higher 1,2-propanediol selectivity (the proportion of 1,2-propanediol in the product distribution reaches more than 92%).

[0151] Compared to Example 10, which uses sulfuric acid as an acidic catalyst, Example 5 of this invention uses benzenesulfonic acid, a preferred acidic catalyst, to prepare 1,2-propanediol. This not only results in lower wastewater volume but also higher reaction selectivity, with 1,2-propanediol accounting for more than 92% of the product distribution.

[0152] Compared to Example 11, which uses sodium hydroxide as an alkaline catalyst, Example 5 of this invention uses sodium methoxide, a preferred alkaline catalyst, to prepare 1,2-propanediol. This not only results in lower wastewater volume but also higher reaction selectivity, with 1,2-propanediol accounting for more than 92% of the product distribution.

[0153] Compared to Example 12, where the alkaline catalytic reaction solution was added at a rate of 200 parts by weight / min, Example 5 of the present invention uses a preferred addition rate of 90 parts by weight / min. The resulting salt crystals after neutralization have a large particle size, making solid-liquid separation easier. At the same time, under this addition rate, the occurrence of side reactions is greatly reduced, and the purity of the product is relatively improved. In contrast, the salt crystals obtained after neutralization in Example 12 have a smaller particle size. When filtered using a 20 μm pore size filter membrane, a large amount of crystal salt cannot be retained, and smaller crystal salt particles will enter the filtrate. It is determined that the crystal salt particle size is <20 μm.

[0154] Compared to Comparative Example 1, which only underwent acid catalysis and neutralized with sodium hydroxide, and Comparative Example 2, which only underwent alkali catalysis and neutralized with hydrochloric acid, Example 4, which underwent both alkali and acid catalysis and neutralized the alkali-catalyzed reaction solution, resulted in a significant reduction in wastewater volume, a transparent and aesthetically pleasing product, and a large crystal size of the salt obtained from acid-alkali neutralization, facilitating solid-liquid separation. Furthermore, the product distribution showed that 1,2-propanediol accounted for over 90% of the total product. In contrast, the crystal size of the salt obtained after neutralization in Comparative Examples 1 and 2 was smaller. When filtered using a 200 μm pore size filter membrane, most of the crystal salt could not be retained, and smaller crystal salt particles would enter the filtrate. However, a 20 μm pore size filter membrane could essentially filter all of the crystal salt, and no crystal precipitate appeared in the filtrate, indicating that the crystal salt particle size was within the range of 20-50 μm.

[0155] In the method for preparing 1,2-propanediol in Comparative Example 3, no catalyst was used, and the final product distribution showed that 1,2-propanediol accounted for only 59.3%, and the wastewater production was as high as 200g (total wastewater accompanying each kilogram of product). In contrast, in the embodiment using the preparation method of the present invention, the wastewater production can be as low as 15g, and the proportion of 1,2-propanediol in the product distribution can be as high as 92% or more.

[0156] Compared to Comparative Example 4, which only underwent acid catalysis and neutralized with sodium hydroxide, and Comparative Example 5, which only underwent alkali catalysis and neutralized with hydrochloric acid, Example 5, which underwent both alkali and acid catalysis and neutralized the alkali-catalyzed reaction solution, resulted in a significant reduction in wastewater volume, a transparent and aesthetically pleasing product, and a large crystal size of the salt obtained from acid-alkali neutralization, facilitating solid-liquid separation. Furthermore, the product distribution showed that 1,2-propanediol accounted for over 92%. In contrast, the salt obtained after neutralization in Comparative Examples 4 and 5 had smaller crystal sizes. When filtered using a 200 μm pore size filter membrane, most of the crystal salt could not be retained, and smaller crystal salt particles would enter the filtrate. However, a 20 μm pore size filter membrane could essentially filter them all clean, and no crystal precipitate appeared in the filtrate, indicating that the crystal salt particle size was within the range of 20-50 μm.

[0157] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing 1,2-propanediol, characterized in that, The method includes: Step (1): In the presence of an acidic catalyst and water, the first part of propylene oxide undergoes a ring-opening reaction to obtain an acid-catalyzed reaction solution containing 1,2-propanediol. Step (2): In the presence of an alkaline catalyst and water, the second part of propylene oxide undergoes a ring-opening reaction to obtain an alkaline catalytic reaction solution containing 1,2-propanediol. Step (3): Mix the acid-catalyzed reaction solution and the base-catalyzed reaction solution to obtain a mixture containing 1,2-propanediol; In step (1), the molar ratio of the first part of propylene oxide to water and the molar ratio of the second part of propylene oxide to water are each 1:1-5.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of the first part of propylene oxide to water is 1:1-3, preferably 1:1-1.5; And / or, in step (2), the molar ratio of the second part of propylene oxide to water is 1:1-3, preferably 1:1-1.

5.

3. The method according to claim 1 or 2, characterized in that, In step (1), the molar ratio of the first portion of propylene oxide to the acid catalyst is 1:0.0001-0.001, preferably 1:0.0001-0.0006, more preferably 1:0.0001-0.0005, and even more preferably 1:0.0001-0.00015; And / or, in step (2), the molar ratio of the second part of propylene oxide to the alkaline catalyst is 1:0.0001-0.0005, preferably 1:0.0003-0.0005, more preferably 1:0.00035-0.00045.

4. The method according to any one of claims 1-3, characterized in that, The reaction conditions for the ring-opening reaction in step (1) include: a reaction temperature of 25-200℃, preferably 80-160℃, more preferably 130-160℃; a reaction pressure of 0.1-2.5 MPa, preferably 0.15-2 MPa, more preferably 1.8-2 MPa; and a reaction time of 1-6 h, preferably 2-4 h, more preferably 2-3 h. Preferably, the ring-opening reaction in step (1) is carried out in an inert atmosphere; More preferably, the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

5. The method according to any one of claims 1-4, characterized in that, The reaction conditions for the ring-opening reaction in step (2) include: a reaction temperature of 25-180℃, preferably 60-120℃, more preferably 80-100℃; a reaction pressure of 0.1-2 MPa, preferably 0.1-1 MPa, more preferably 0.8-1 MPa; and a reaction time of 1-6 h, preferably 1-4 h, more preferably 3-4 h. Preferably, the ring-opening reaction in step (2) is carried out in an inert atmosphere; More preferably, the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

6. The method according to any one of claims 1-5, characterized in that, The acidic catalyst is selected from inorganic acids or organic acids; Preferably, the inorganic acid is selected from at least one of hydrochloric acid, hypochlorous acid, chlorite, chloric acid, perchloric acid, sulfuric acid, sulfurous acid, sulfurous acid, persulfate, thiosulfate, dithionic acid, pyrosulfuric acid, metasulfuric acid, phosphoric acid, phosphorous acid, hypophosphoric acid, metaphosphoric acid, orthophosphoric acid, diphosphoric acid, triphosphoric acid, peroxydiphosphoric acid, hydrofluoric acid, hypofluoride, hydrobromic acid, bromic acid, hypobromic acid, bromic acid, perbromic acid, iodic acid, hypoiodic acid, iodic acid, nitric acid, nitrous acid, fuming nitric acid, manganese acid, molybdic acid, tungstic acid, selenic acid, silicic acid, stannic acid, titanic acid, telluric acid, rhenium acid, arsenic acid, and boric acid. And / or, the organic acid is selected from formic acid, acetic acid, propionic acid, n-butyric acid, n-valeric acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, dodecylbenzenesulfonic acid, tetradecanoic acid, pentadecanoic acid, nonadecanoic acid, lauric acid, tartaric acid, isobutyric acid, isovaleric acid, isohexanoic acid, isoheptanoic acid, isononanoic acid, 2-ethylhexanoic acid, isodecanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, tetradecanoic acid, fumaric acid, maleic acid, terephthalic acid, 1,4-phenylenediacetic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 9 At least one of the following: 10-anthracite, 4,4'-biphenyldicarboxylic acid, methanesulfonic acid, ethylsulfonic acid, propylsulfonic acid, 1-butanesulfonic acid, 1-pentanesulfonic acid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, 1-octanesulfonic acid, 1-nonanesulfonic acid, 1-decanesulfonic acid, dodecylbenzenesulfonic acid, vinylsulfonic acid, aminosulfonic acid, taurine, hydroxyethylsulfonic acid, (±)-camphor-10-sulfonic acid, benzenesulfonic acid, chlorosulfonic acid, p-toluenesulfonic acid, 3-pyridinesulfonic acid, 2-naphthalenesulfonic acid, quinoline-8-sulfonic acid, methanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, 4,4'-biphenyldisulfonic acid, and 1,5-naphthalenedisulfonic acid.

7. The method according to any one of claims 1-6, characterized in that, The alkaline catalyst is selected from inorganic or organic bases; Preferably, the inorganic base is selected from at least one of ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, aluminum hydroxide, magnesium hydroxide, zirconium oxide, cerium hydroxide, strontium hydroxide, zinc hydroxide, cobalt hydroxide, palladium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, rubidium carbonate, strontium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, rubidium bicarbonate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate. And / or, the organic base is selected from methylamine, ethylamine, furfurylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, dodecylamine, tetradecylamine, hexadecylamine, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, diethylamine, triethylamine, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine, heptamethamine, octyldiamine, nonanediamine, decanediamine, o-phenylenediamine, p-phenylenediamine, isopropylamine, isobutylamine, and isopentylamine. At least one of the following: 2-ethylhexylamine, diisopropylamine, N,N-diisopropylethylamine, pyridine, 4-dimethylaminopyridine, morpholine, imidazole, oxazole, thiazole, pyrazine, pyrimidine, indole, indoleaniline, quinoline, diphenylamine, 1-naphthylamine, naphthalene-2,6-diamine, 1-anthramine, anthracene-2,6-diamine, [2,2'-bipyridine]-5,5'-diamine, N-tert-butylisopropylamine, dibenzylamine, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

8. The method according to any one of claims 1-7, characterized in that, In step (3), before mixing the acid catalytic reaction solution and the base catalytic reaction solution, the acid catalytic reaction solution and the base catalytic reaction solution are cooled to 25-80°C, preferably 25-60°C, respectively. And / or, in step (3), the method of mixing the acid catalytic reaction solution and the base catalytic reaction solution includes: adding the base catalytic reaction solution to the acid catalytic reaction solution; Preferably, the addition rate is 50-100 parts by weight / min relative to 100 parts by weight of the acid-catalyzed reaction solution, more preferably 80-100 parts by weight / min; And / or, the method further includes step (4): the mixture containing 1,2-propanediol obtained in step (3) is subjected to dehydration, solid-liquid separation and fractionation treatment in sequence to obtain 1,2-propanediol.

9. The method according to claim 8, characterized in that, The dehydration conditions include: a dehydration pressure of 4-7 kPa, preferably 5-7 kPa; and a dehydration temperature of 50-90°C, preferably 60-90°C. And / or, the solid-liquid separation is performed by filtration; Preferably, the pore size of the filter membrane used for filtration is 20-200 μm, and more preferably 100-150 μm.

10. The application of the method according to any one of claims 1-9 in the fields of basic chemical industry, pharmaceutical industry, cosmetic industry, and photocuring industry.

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