Reboiler and preparation method and application thereof

Abstract

The present application relates to the technical field of glycolic acid solution concentration, and discloses a reboiler and a preparation method and application thereof.A reboiler comprises a reboiler base body and a silane layer, a first modified layer and a second modified layer which are coated on the outer surface of the reboiler base body from inside to outside; the first modified layer contains an amide group, and the second modified layer contains a pyrrole group, a mercapto group and / or a sulfide.The reboiler provided by the present application can effectively reduce the oligomer content in the target product after modification.

Description

Technical Field

[0001] This invention relates to the technical field of glycolic acid solution concentration, specifically to a reboiler, its preparation method, and its application. Background Technology

[0002] Glycolic acid, also known as glycolic acid, is the simplest α-amino acid. It is an important organic synthesis intermediate that can replace hydrochloric acid, citric acid, and EDTA in chemical cleaning. It can also be used to prepare anti-skin aging and whitening cosmetics, as a dyeing auxiliary in wool dyeing, and as a crosslinking coupling agent or catalyst in cellulose fabrics. Furthermore, due to the biodegradability of glycolic acid polymers, they can be used to prepare polyglycolic acid (PGA) or polylactic-co-glycolic acid (PLGA). These materials possess unique properties such as non-toxicity, biocompatibility, and in vitro and in vivo degradation, making them widely applicable in medical polymer fields such as suture reinforcement materials, bioabsorbable sutures, fracture fixation materials, drug delivery carriers, and tissue engineering.

[0003] Methods for synthesizing glycolic acid include the chloroacetic acid hydrolysis method (i.e., chloroacetic acid is hydrolyzed in the presence of sodium hydroxide to produce glycolic acid), the cyanidation method (using formaldehyde and hydrogen cyanide or sodium cyanide as initial raw materials, hydroxyacetonitrile is synthesized by adding cyanide, and then hydrolyzed under acidic conditions at a temperature of about 100-150℃ to obtain glycolic acid), the formaldehyde carbonylation method (under high temperature and high pressure conditions, using specific catalysts and reaction media, formaldehyde, carbon monoxide and water can be converted into glycolic acid through a alkylation reaction), and the dimethyl oxalate hydrogenation method (dimethyl oxalate is prepared by syngas, dimethyl oxalate is catalytically hydrogenated to prepare methyl glycolate, and then glycolate is hydrolyzed to obtain glycolic acid), etc.

[0004] When glycolic acid is used in high-end fields such as electronic cleaning agents or polymer monomers, its quality requirements are high. However, glycolic acid has the characteristics of easy polymerization when heated, easy decomposition at boiling point, and extremely low volatility, which greatly limits the separation methods. Currently available separation methods include crystallization, solvent extraction, and esterification.

[0005] Patent application CN113845415A discloses a method, apparatus, and application for the separation and purification of glycolic acid using a distillation-crystallization coupling technology. This method utilizes bio-based platform compound molecules as raw materials to synthesize glycolic acid, and then uses a vacuum distillation-crystallization coupling technology to separate and purify the obtained crude glycolic acid, yielding high-purity glycolic acid. This process is essentially a conventional separation method, and the resulting product is generally used in conventional fields such as industrial cleaning. Patent application CN112645814A discloses a method for purifying glycolic acid and glycolic acid crystals and their applications, which significantly improves the quality of glycolic acid through a molecular distillation-crystallization coupling method. This process is generally used for small-batch refining of glycolic acid, but its capacity is limited when used for large-batch degradable polymerizable monomers.

[0006] Solvent extraction of glycolic acid: The *Journal of East China University of Science and Technology (Natural Science Edition)* (1994, Vol. 2, pp. 148-153) discloses a method using trialkylphosphine oxide as the extractant and sulfonated kerosene as the diluent. Extraction is carried out at room temperature and an initial aqueous phase pH of 1-3 with an extractant composition of 50% trialkylphosphine oxide and 50% sulfonated kerosene. Then, the glycolic acid in the loaded organic phase is back-extracted with deionized water, achieving a single back-extraction rate of 73.4% at 90°C. Products prepared using this process are generally used in routine cleaning applications; introducing the extractant can lead to the introduction of new impurities into the product.

[0007] The Chemical Products Handbook - Organic Chemical Raw Materials (Volume 1) (Institute of Scientific and Technological Information, Ministry of Chemical Industry, Beijing: Chemical Industry Press, 1985) introduces the esterification and hydrolysis purification method for glycolic acid. However, the repeated process of dehydration-esterification-hydrolysis of the hydrolyzed glycolic acid product leads to a decrease in the yield of glycolic acid.

[0008] Existing glycolic acid purification technologies primarily yield products used in routine cleaning applications. However, when applied to electronic-grade chemicals, particularly as monomers for biodegradable materials, impurities such as oligomers in the glycolic acid products have been found to significantly impact the micro-cleaning effect on circuit boards or silicon wafers, as well as the molecular weight of polyglycolic acid and the physicochemical properties of the polymer. Therefore, advanced glycolic acid refining technology is one of the crucial issues that urgently needs to be addressed for glycolic acid to be used in high-end applications. Summary of the Invention

[0009] The purpose of this invention is to overcome the problem of high oligomer content in the concentration process of glycolic acid aqueous solution in the prior art, and to provide a reboiler and its preparation method and application. The reboiler is used in the evaporation, dehydration and concentration process of glycolic acid aqueous solution, effectively reducing coking and clogging of the reboiler during use, reducing the oligomer content in glycolic acid aqueous solution products, and helping to extend the operating cycle of glycolic acid production equipment.

[0010] To achieve the above objectives, a first aspect of the present invention provides a reboiler, wherein the reboiler comprises a reboiler substrate and a silane layer, a first modified layer and a second modified layer sequentially coated on the outer surface of the reboiler substrate from the inside out; the first modified layer contains amide groups and the second modified layer contains pyrrole groups, mercapto groups and / or thioethers.

[0011] A second aspect of the present invention provides a method for preparing a reboiler, wherein the method includes:

[0012] (1) The reboiler substrate is subjected to silanization treatment to obtain a reboiler substrate coated with a silane layer;

[0013] (2) The reboiler substrate coated with the silane layer is subjected to a first modification treatment using the first modification component to obtain the first modified reboiler substrate.

[0014] (3) The reboiler matrix after the first modification treatment is subjected to a second modification treatment using a second modification component to obtain a reboiler;

[0015] The first modified component contains an amide group, and the second modified component contains a pyrrole group, a mercapto group, and / or a thioether.

[0016] The third aspect of this invention provides the application of the reboiler described in the first aspect or the reboiler prepared by the preparation method described in the second aspect in the concentration of hydroxy fatty acid solutions.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] According to the inventors' research, in reboilers or general heat exchangers (especially those used for heating glycolic acid), the amount of glycolic acid oligomers at the outlet is increased relative to the inlet material. This is mainly because the temperature difference between the heating medium (such as low-pressure steam, low-low-pressure steam, etc.) and the bulk glycolic acid solution during heating in the reboiler or heat exchanger is approximately 10-80°C. The metal matrix is ​​overheated or significantly overheated relative to the bulk solution, causing the heat-sensitive glycolic acid to generate oligomers upon contact with the matrix surface. Some oligomers diffuse into the bulk solution due to turbulent flow, while others adsorb onto the matrix surface and gradually accumulate, leading to scaling and blockage in the reboiler or heat exchanger. This invention reduces oligomer formation through reboiler matrix modification.

[0019] In this invention, a silane layer, a first modified layer, and a second modified layer are sequentially coated on the outer surface of the reboiler substrate to separate the reboiler shell from easily polymerizable components. Specifically, the first modified layer is a water film layer, and the second modified layer is a selectively permeable layer. The first modified layer has good water absorption and swelling properties, while the second modified layer does not inhibit the passage of water molecules but selectively inhibits easily polymerizable components such as glycolic acid and its oligomers. This avoids direct contact between easily polymerizable components and the overheated reboiler surface, reduces the polymerization, scaling, and discoloration of easily polymerizable components on the reboiler surface, thereby reducing the content of oligomers in the product and slowing down scaling on the reboiler surface. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a reboiler, wherein the reboiler includes a reboiler substrate and a silane layer, a first modified layer and a second modified layer sequentially coated on the outer surface of the reboiler substrate from the inside to the outside; the first modified layer contains amide groups and the second modified layer contains pyrrole groups, mercapto groups and / or thioethers.

[0022] In this invention, a silane layer and a modified layer are sequentially coated on the outer surface of the reboiler. The silane layer serves as a medium between the reboiler substrate and the modified layer. The silane layer can withstand temperatures of 100-200℃, and due to its thinness, it has low heat transfer resistance. Coating the reboiler surface with a silane layer improves the reboiler's high-temperature corrosion resistance, reduces the release of metal ions from the equipment, thereby reducing the polymerization activation effect on heat-sensitive glycolic acid and lowering the metal ion content in the product, thus improving product quality. On the other hand, the various groups in the silane layer and the modified layer work together. The modified layer contains amide groups, pyrrole groups, mercapto groups, and / or sulfides, which is equivalent to forming a water film layer and a selectively permeable layer on the surface of the silane layer. The water film layer separates the reboiler shell from the easily polymerizable components. The selectively permeable layer only allows water to pass through and does not allow the easily polymerizable components to pass through, avoiding direct contact between the easily polymerizable components and the reboiler surface, reducing polymerization, scaling, and discoloration of the easily polymerizable components on the reboiler surface.

[0023] In this invention, a silane layer, a first modified layer, and a second modified layer are sequentially coated on the outer surface of the reboiler substrate. The silane layer can withstand temperatures of 100-200℃. Coating the outer surface of the reboiler substrate with the silane layer improves the high-temperature corrosion resistance of the reboiler. The amide groups contained in the first modified layer form a water film layer on the surface of the silane layer. The second modified layer contains groups that inhibit the permeation of easily polymerizable components, thereby forming a water-rich water film layer in conjunction with the first modified layer, separating the reboiler shell from the easily polymerizable components. The water in the water film layer is first partially or completely vaporized by heating and enters the liquid phase bulk. Since the bubble point temperature of the water film is lower than that of the liquid phase bulk, and significantly lower than the temperature of the heating medium, it achieves indirect vaporization from the original liquid phase at a lower temperature. The direct and uniform heating of the liquid phase by water disperses the heating points and lowers the heating temperature, which can significantly reduce the polymerization of heat-sensitive components or the formation of colored impurities at the traditional heating interface. The second modified layer is a selectively permeable layer that only allows water to pass through and is basically impermeable to easily polymerizable components. This can prevent easily polymerizable components from directly contacting the outer surface of the reboiler, reducing the polymerization, scaling, and discoloration of easily polymerizable components on the reboiler surface. At the same time, the heated water diffuses to the liquid phase through convection and the selectively permeable layer. The cold water and easily polymerizable components in the liquid phase approach the reboiler surface with the convection. Due to the barrier of the selectively permeable layer, the molecules of easily polymerizable components are trapped, while the cold water passes through the selectively permeable layer into the water film layer for heating.

[0024] In this invention, it is understood that the silane layer, the first modified layer and the second modified layer described in this invention only consider the outer surface of the reboiler substrate and do not include the interior of the reboiler substrate. During the preparation process, it is inevitable that silane and modified components will exist inside the reboiler substrate, and this invention does not make any special limitation on this.

[0025] In this invention, the amide groups, pyrrole groups, and mercapto groups and / or thioethers in the modified layer are determined by infrared spectroscopy. The specific testing conditions are KBr tableting at 400 cm⁻¹. -1 -4000cm -1 Scan within the range.

[0026] According to a preferred embodiment of the present invention, the thickness of the first modified layer is 10-18 micrometers.

[0027] According to a preferred embodiment of the present invention, the thickness of the second modified layer is 3-8 micrometers.

[0028] The first modified layer of this invention is a water film layer, which has a good water absorption and swelling effect in aqueous glycolic acid. After absorbing water and swelling, it can form a three-dimensional structure rich in water molecules, thereby forming a water film layer outside the silane layer. This water film layer serves to separate the solution bulk, silane layer and metal matrix. On the other hand, under certain process conditions, the water film layer is first partially or completely vaporized by heating and enters the liquid phase bulk. Since the boiling temperature of the water film is lower than the boiling temperature of the liquid phase bulk, and much lower than the temperature of the heating medium (such as low-pressure steam), it achieves the indirect heating effect of changing from direct heating of the liquid phase bulk by the heating wall (i.e., reboiler shell) to heating of the water-rich layer with a lower boiling point by the heating wall first, and then direct and uniform heating of the liquid phase bulk by the water-rich layer through hot and cold convection. This disperses the heating point, reduces the heating temperature, and can significantly reduce the polymerization of heat-sensitive components near the heating interface.

[0029] The second modified layer of the present invention is a selectively permeable layer, which has low selective permeability to glycolic acid molecules in glycolic acid solution and no significant inhibition of water molecule permeability. In addition to avoiding the problem of thermal polymerization of glycolic acid molecules in the bulk solution entering the water film layer and contacting the heating interface, it also significantly reduces the thermal polymerization of glycolic acid in the water-rich layer caused by the significant reduction in the concentration of glycolic acid in the water film layer relative to the concentration of glycolic acid in the bulk liquid phase. This reduces the contact between glycolic acid or its oligomers and the metal matrix, reduces reboiler corrosion, and slows down reboiler scaling.

[0030] In this invention, there is no particular limitation on the type of reboiler. The reboiler substrate is at least one of an in-tank boiling reboiler, a circulating reboiler, and a falling film reboiler.

[0031] According to a preferred embodiment of the present invention, the in-tank reboiler is a kettle-type reboiler and / or an internal reboiler, and the circulating reboiler is selected from at least one of a vertical thermosiphon reboiler, a horizontal thermosiphon reboiler, and a pump-forced circulating reboiler.

[0032] According to a preferred embodiment of the present invention, the reboiler substrate is made of metal, preferably at least one of 304, 304L, 316 and 316L.

[0033] According to a preferred embodiment of the present invention, in the silane layer, the molar ratio of the group (-Si-O-Si-) to the group (-Si-OM) is 1.3-4.3; wherein M is a metal derived from the reboiler substrate.

[0034] In this invention, the groups (-Si-O-Si-) and (-Si-OM) are determined by infrared spectroscopy. Specific test conditions include: KBr pellet compression at 400 cm⁻¹. -1 -4000cm -1 Scan within the range.

[0035] According to a preferred embodiment of the present invention, the thickness of the silane layer is 2-6.3 micrometers.

[0036] According to a preferred embodiment of the present invention, the silane layer is provided by at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate and 3-(isobutenoyloxy)propyltrimethoxysilane.

[0037] According to a preferred embodiment of the present invention, in the first modified layer, the content of amide groups is 6-21.2 mmol / m² based on the outer surface area of ​​the dry-based reboiler substrate. 2 The preferred value is 13-21.2 mmol / m². 2 .

[0038] According to a preferred embodiment of the present invention, the second modified layer contains 45-63 mmol / m² of pyrrole groups based on the outer surface area of ​​the dry-based reboiler substrate. 2 The content of thiol groups and / or thioethers is 5-40 mmol / m 2 More preferably, in the second modified layer, the content of pyrrole groups is 54-63 mmol / m² based on the dry-basis reboiler outer surface area. 2 The content of thiol groups and / or thioethers is 12-40 mmol / m 2 .

[0039] According to a preferred embodiment of the present invention, in the second modified layer, the content of thiol groups is 5-20 mmol / m² based on the outer surface area of ​​the dry-based reboiler substrate. 2 The sulfide content is 5-20 mmol / m³. 2 More preferably, in the second modified layer, the content of thiol groups is 12-20 mmol / m² based on the dry-basis reboiler outer surface area. 2 The sulfide content is 12-20 mmol / m³. 2 .

[0040] A second aspect of the present invention provides a method for preparing a reboiler, wherein the method includes:

[0041] (1) The reboiler substrate is subjected to silanization treatment to obtain a reboiler substrate coated with a silane layer;

[0042] (2) The reboiler substrate coated with the silane layer is subjected to a first modification treatment using the first modification component to obtain the first modified reboiler substrate.

[0043] (3) The reboiler matrix after the first modification treatment is subjected to a second modification treatment using a second modification component to obtain a reboiler;

[0044] The first modified component contains an amide group, and the second modified component contains a pyrrole group, a mercapto group, and / or a thioether.

[0045] In this invention, the type and material of the reboiler substrate in step (1) have been described in the first aspect and will not be repeated here.

[0046] In this invention, the reboiler substrate is pretreated before silanization. Specifically, the reboiler substrate is first ultrasonically polished with a suspension polishing slurry (preferably silicon carbide) (the ultrasonic frequency is preferably 20-40 kHz), then ultrasonically cleaned (preferably sequentially using demineralized water ultrasonic cleaning (cleaning ultrasonic frequency 30-70 kHz, temperature 60-80°C, cleaning time 30-40 minutes), acetone ultrasonic cleaning (cleaning ultrasonic frequency 40-80 kHz, cleaning temperature 20-40°C, cleaning time 20-30 minutes), and alkaline ultrasonic cleaning (wherein the alkaline solution composition, by mass content, is 8-12% sodium hydroxide and 0.6-1.2% sodium phosphate, ultrasonic frequency 50-90 kHz, alkaline washing temperature 60-90°C, alkaline washing time 20-30 minutes)), then rinsed with water (preferably demineralized water) (preferably 4-6 times), and finally dried with nitrogen gas (preferably at a temperature of 20-40°C).

[0047] According to a preferred embodiment of the present invention, in step (1), the thickness of the silane layer is 2-6.3 micrometers.

[0048] According to a preferred embodiment of the present invention, the silanization treatment includes: contacting a silane reagent solution with the reboiler substrate, followed by drying and curing. In this invention, the method of silanization treatment is not particularly limited; for example, it can be dip coating.

[0049] According to a preferred embodiment of the present invention, in step (1), the conditions for the silanization treatment include: immersion coating time of 1-4 minutes, drying and curing temperature of 110-130°C, and drying and curing time of 30-50 minutes.

[0050] According to a preferred embodiment of the present invention, in step (1), the drying and curing is carried out under a protective atmosphere, which is nitrogen and / or an inert gas.

[0051] According to a preferred embodiment of the present invention, in step (1), the silane reagent solution is obtained by mixing a silane reagent, water and anhydrous low alcohol, and then performing pre-hydrolysis.

[0052] In this invention, preferably, the pre-hydrolysis time is 10-25 hours.

[0053] According to a preferred embodiment of the present invention, the volume ratio of silane reagent: water: anhydrous low alcohol is (2.8-5.3):(4-7.2):(90-96).

[0054] According to a preferred embodiment of the present invention, the pH value of the silane-containing reagent solution is 7.5-8.5.

[0055] According to a preferred embodiment of the present invention, the anhydrous low alcohol is anhydrous ethanol and / or anhydrous methanol.

[0056] According to a preferred embodiment of the present invention, the silane reagent is selected from at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate, and 3-(isobutenoyloxy)propyltrimethoxysilane.

[0057] Preferably, in step (1), the amount of silane reagent solution used is such that the molar ratio of group (-Si-O-Si-) to group (-Si-OM) in the prepared reboiler coated with silane layer is 1.3-4.3, wherein M is a metal from the reboiler substrate.

[0058] According to a preferred embodiment of the present invention, in step (2), the first modification treatment and the second organic modification treatment cause the outer surface of the reboiler coated with the silane layer to be sequentially coated with a first modified layer and a second modified layer, wherein the first modified layer contains amide groups and the second modified layer contains pyrrole groups, mercapto groups and / or thioethers.

[0059] In this invention, the types and contents of each group in the first modified layer and the second modified layer, as well as their preferred ranges, have been described in the first aspect and will not be repeated here.

[0060] According to a preferred embodiment of the invention, the amide group is provided by an amide derivative, preferably by at least one of N,N'-[ethylenedi(oxymethylene)]bis(acrylamide), N,N'-(1,2-dihydroxyethylene)disacrylamide and hexamethylenebisacrylamide.

[0061] In this invention, the modification process is carried out in two steps to obtain the desired modified layer. Preferably, the first modification process includes: contacting a solution containing a first modifying component with a reboiler coated with a silane layer; the first modifying component contains amide groups.

[0062] According to a preferred embodiment of the present invention, in step (2), the mass ratio of the first modified component: the first initiator: the first solvent in the solution containing the first modified component is (4-7.2):(0.4-1.4):(230-273).

[0063] According to a preferred embodiment of the present invention, the first solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene.

[0064] According to a preferred embodiment of the present invention, the first initiator is selected from at least one of azo initiators, organic peroxide initiators, inorganic peroxide initiators, and redox initiators, more preferably at least one of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and hydrogen peroxide, and even more preferably benzoyl peroxide.

[0065] According to a preferred embodiment of the invention, the amide group is provided by an amide derivative, preferably by at least one of N,N'-[ethylenedi(oxymethylene)]bis(acrylamide), N,N'-(1,2-dihydroxyethylene)disacrylamide and hexamethylenebisacrylamide.

[0066] According to a preferred embodiment of the present invention, in step (2), the first modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the first modified component to the reboiler coated with the silane layer in step (1) is 2-5, the soaking temperature is 50-70°C, and the time is 1.5-3h.

[0067] According to a preferred embodiment of the present invention, in step (3), the second modification treatment includes: contacting a solution containing a second modified component with a first modified product; the second modified component contains pyrrole, mercapto, and / or thioether.

[0068] According to a preferred embodiment of the present invention, in step (2), the mass ratio of the second modified component: the second initiator: the second solvent in the solution containing the second modified component is (12-23): (1-3): (150-300).

[0069] In this invention, the range of types of the second solvent can be the same as that of the first solvent, and will not be elaborated further here.

[0070] In this invention, the range of types of the second initiator can be the same as that of the first initiator, and will not be elaborated further here.

[0071] According to a preferred embodiment of the invention, the pyrrole group is provided by a pyrrole derivative, preferably by at least one selected from methyl 4-vinyl-1H-pyrrole-3-carboxylate, methyl 5-vinyl-1H-pyrrole-2-carboxylate, 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, 5-allyl-4-methoxy-1,5-dihydro-2H-pyrrole-2-one, 1-allyl-2-cyclopentyl-1H-pyrrole, 1-(1-phenylvinyl)pyrrole, 3-isopropenyl-1-methyl-pyrrole, and 1-allyl-2-isopropenyl-1H-pyrrole.

[0072] According to a preferred embodiment of the invention, the thiol group and / or thioether are provided by thiol derivatives and / or thioether derivatives, preferably by bis(4-methacryloylthiophenyl) thioether and / or allyl 2-mercaptopropionate.

[0073] According to a preferred embodiment of the present invention, in the second modified component, the molar ratio of pyrrole: mercapto and / or thioether is (3-8):1.

[0074] According to a preferred embodiment of the present invention, in step (2), the second modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the second modified component to the product obtained from the first modification treatment is 2-5, the soaking temperature is 55-75°C, and the soaking time is 1-3h.

[0075] According to a preferred embodiment of the invention, the method may also optionally include immersing the first modification treatment and the second modification treatment separately in a post-treatment agent.

[0076] In this invention, there is no particular limitation on the type of post-treatment agent. Preferably, the post-treatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol, and anhydrous acetone, with anhydrous ethanol being the most preferred.

[0077] According to a preferred embodiment of the present invention, the conditions for the post-soaking treatment include: a soaking time of 30-300 min.

[0078] According to a preferred embodiment of the present invention, after the soaking post-treatment, the soaking post-treatment product is dried in a protective atmosphere (preferably nitrogen). The drying conditions are not particularly limited in the present invention. In a preferred case, the drying temperature is 120-150°C and the time is 10-30 minutes.

[0079] The third aspect of the present invention provides the application of the reboiler described in the first aspect or the reboiler prepared by the preparation method described in the second aspect in the concentration of hydroxy fatty acid solution, preferably in the heating and concentration of aqueous glycolic acid solution, and more preferably the aqueous glycolic acid solution is contacted with the reboiler to obtain concentrated glycolic acid solution.

[0080] In this invention, the source of the aqueous glycolic acid solution is not particularly limited. Preferably, the aqueous glycolic acid solution is derived from at least one of the following methods: hydrolysis of chloroacetic acid, cyanation, carbonylation of formaldehyde, electrolytic reduction of oxalic acid, coupling of formaldehyde and methyl formate, hydrogenation of dimethyl oxalate, and microbial catalysis.

[0081] According to a preferred embodiment of the present invention, the aqueous solution of glycolic acid contains the following components: by mass percentage, water content is 30-90%, glycolic acid content is 5-65%, and oligomer content is 0-5%.

[0082] According to a preferred embodiment of the present invention, the oligomer includes at least one selected from dimers, trimers, tetramers, pentamers, and hexamers of glycolic acid.

[0083] According to a preferred embodiment of the present invention, the contact conditions include: a contact temperature of 50-100°C and a pressure of 5-100 kPa measured by an absolute pressure gauge.

[0084] According to a preferred embodiment of the present invention, after the aqueous solution of glycolic acid comes into contact with the reboiler, it enters the distillation column for distillation separation.

[0085] According to a preferred embodiment of the present invention, the distillation column has 3-10 theoretical plates and a reflux ratio of 0.5-3.

[0086] According to a preferred embodiment of the present invention, the distillation column is a reactive distillation column and / or a dehydration column.

[0087] According to a preferred embodiment of the present invention, the oligomer content in the reaction product after contact is not higher than 5%, preferably not higher than 2%, and more preferably not higher than 0.5%.

[0088] The present invention will now be described in detail through examples and comparative examples.

[0089] In this invention, the content of each group in the reboiler is determined by the test method described above.

[0090] In this invention, component analysis employed a 20A high-performance liquid chromatography (HPLC) system (Shimadzu Corporation, Japan, equipped with an autosampler, 10AT and 10AD pumps, and a 20A multi-wavelength UV detector); and an ACQUITY UPLC / Xevo G2 QTOF ultra-high performance liquid chromatography-high resolution tandem mass spectrometry (Waters Corporation, USA, equipped with an autosampler and a diode array UV detector). HPLC conditions were as follows: column: Zorbax Eclipse Plus C18 (4.6 mm × 150 mm, 5 μm); mobile phase: water (containing 0.06% v phosphoric acid): acetonitrile = 95:5; flow rate: 1.0 mL / min; detection wavelength: 210 nm; column temperature: 35 °C; injection volume: 1 μL. Ultra-high performance liquid chromatography (UHPLC) conditions: Column: HSS T3 (2.1 mm × 100 mm, 1.7 μm); Mobile phase: water, methanol; Gradient elution (positive ion mode): 0 min V(water):V(methanol) = 85:15, after 2.5 min V(water):V(methanol) = 55:35, after 4 min V(water):V(methanol) = 10:90, flow rate: 0.45 mL / min; Gradient elution (negative ion mode): 0 min V(water):V(methanol) = 70:30, after 2.5 min V(water):V(methanol) = 55:35, after 3.5 min V(water):V(methanol) = 10:90; flow rate: 0.45 mL / min; Column temperature: 30 ℃; Injection volume: 3 μL. Mass spectrometry conditions: electrospray ionization source (ESI), positive or negative ion scanning mode, capillary voltage 2kV, cone voltage 30eV, ion source temperature: 120℃, desolventizing temperature 450℃, cone gas flow rate 50L / h, desolventizing gas (N2) flow rate 900L / h.

[0091] Example 1

[0092] The glycolic acid solution in this embodiment is derived from the hydrogenation process of dimethyl oxalate. The solution composition, by mass percentage, is 37.42% glycolic acid, 0.08% oligomer, and 62.5% water.

[0093] The reboiler described in this embodiment is set in the bottom of the hydrolysis reaction distillation column of glycolic acid ester. The preparation method of the reboiler includes: (1) silanizing the reboiler substrate to obtain a reboiler coated with a silane layer; (2) performing a first modification treatment on the reboiler coated with a silane layer obtained in step (1); and (3) performing a second modification treatment on the reboiler obtained in step (2) to obtain a reboiler. The reboiler substrate is a batch reboiler made of 304 stainless steel.

[0094] The silanization process described in step (1) employs a conventional dip-coating method in the art. Before the silanization process, the reboiler substrate is pretreated. Specifically, the reboiler substrate is first ultrasonically polished with a suspension polishing slurry (silicon carbide) at a frequency of 30 kHz. Then, it is ultrasonically cleaned with demineralized water (at a frequency of 50 kHz, a temperature of 70 ℃, and a cleaning time of 35 minutes), ultrasonically cleaned with acetone (at a frequency of 60 kHz, a temperature of 30 ℃, and a cleaning time of 25 minutes), ultrasonically cleaned with alkaline solution (the alkaline solution composition, by mass content, is 10% sodium hydroxide and 0.9% sodium phosphate, with an ultrasonic frequency of 75 kHz, an alkaline washing temperature of 75 ℃, and an alkaline washing time of 25 minutes), rinsed with demineralized water (5 times), and dried with nitrogen (at a temperature of 30 ℃). Subsequently, the silane layer was dip-coated (immersion time 2.5 minutes) in a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate) (the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 4.0:5.5:92.5, pH value 8.0; the silane reagent solution is prepared by mixing the silane reagent, deionized water and anhydrous ethanol according to the ratio and pre-hydrolyzing for 17.5 hours). After drying and curing, a silane layer with a thickness of 4 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OM) groups of 2.7 was obtained. The drying and curing temperature was 120°C, the drying time was 40 minutes, and the drying atmosphere was nitrogen.

[0095] The solution containing the first modified component used in the first modified layer includes the first modified component (the first modified component is an amide derivative, wherein the amide derivative is selected from N,N′-(1,2-dihydroxyethylene)acrylamide), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The first modified component, benzoyl peroxide, and solvent, by mass parts, are: first modified component: benzoyl peroxide: solvent = 5.5:1.35:250. The treatment conditions for the first modification are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the first modified component to the reboiler coated with the silane layer obtained in step (1) is 3.5, the immersion temperature is 60°C, and the immersion time is 2.25 hours. The amide group content introduced into the modified matrix after the first modification treatment is 13.5 mmol / m³.2 The thickness of the first modified layer is 13.4 micrometers.

[0096] The product after the first modification treatment was subjected to a first post-modification treatment to obtain a first post-modified product. The first post-modification agent used in the first post-modification treatment was anhydrous ethanol. The first post-modification treatment was carried out by immersion, with anhydrous ethanol as the post-modification agent, and the immersion time was 60 min. After the first post-modification treatment, the product was dried in nitrogen at 135°C for 20 min.

[0097] The first modified post-treatment product obtained in step (2) is subjected to a second modification treatment in step (3) to obtain a second modified product. The solution containing the second modified component consists of the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 17.5: 2.0: 250. The pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole: mercapto = 5.5: 1. The treatment conditions for the second modification treatment are as follows: the volume ratio (liquid-solid volume ratio) of the solution containing the second modified component to the product obtained in step (2) is 3.5, the treatment temperature is 65°C, and the treatment time is 2 hours. The content of pyrrole groups introduced into the modified matrix after the second modification treatment was 54 mmol / m. 2 The thiol group concentration is 12.5 mmol / m³. 2 The thickness of the second modified layer is 5.5 micrometers.

[0098] The product after the second modification treatment in step (3) is subjected to a second post-modification treatment to obtain the product after the second post-modification treatment. The modifying agent used in the second post-modification treatment is anhydrous ethanol. The second post-modification treatment is carried out by immersion for 60 minutes. After the second post-modification treatment, it is dried in nitrogen at 130°C for 20 minutes.

[0099] The application of the reboiler prepared in Example 1 in the concentration of glycolic acid includes: contacting an aqueous glycolic acid solution with the reboiler to obtain a heat-exchanged aqueous glycolic acid solution. After contacting the concentrated reboiler, the aqueous glycolic acid solution enters the cavity of a distillation column with 7 theoretical plates and a reflux ratio of 1.7. The distillation column is a reactive distillation column. The heating and concentration conditions of the glycolic acid concentrated reboiler are as follows: contact temperature of 75°C and contact pressure (absolute pressure) of 34 kPa.

[0100] In Example 1, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column was 1.31%.

[0101] Example 2

[0102] The raw materials used in this embodiment are the same as those in Embodiment 1.

[0103] According to the method of Example 1, the reboiler in step (1) is the kettle-type reboiler described in Example 1. The silanization treatment adopts the conventional dip-coating method in the art. Before the silanization treatment, the reboiler substrate is first pretreated. Specifically, the reboiler is first ultrasonically polished with a suspension polishing slurry (silicon carbide) at a polishing ultrasonic frequency of 38 kHz. Then, it is ultrasonically cleaned with demineralized water (cleaning ultrasonic frequency of 69 kHz, temperature of 79 ℃, cleaning time of 38 minutes), ultrasonically cleaned with acetone (cleaning ultrasonic frequency of 77 kHz, cleaning temperature of 39 ℃, cleaning time of 29 minutes), ultrasonically cleaned with alkaline solution (wherein, the composition of the alkaline solution, by mass content, is 11% sodium hydroxide and 1.1% sodium phosphate, ultrasonic frequency of 87 kHz, alkaline washing temperature of 86 ℃, alkaline washing time of 29 minutes), rinsed with demineralized water (6 times), and dried with nitrogen gas (temperature of 38 ℃). Subsequently, the silane layer was dip-coated (immersion time 3.3 minutes) in a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate) (the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 5.0:6.5:94, pH value 7.6; the silane reagent solution is prepared by mixing the silane reagent, deionized water and anhydrous ethanol according to the ratio and pre-hydrolyzing for 24 hours). After drying and curing, a silane layer with a thickness of 5.8 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OM) groups of 4 was obtained. The drying and curing temperature was 113°C, the drying time was 32 minutes, and the drying atmosphere was nitrogen.

[0104] The solution containing the first modified component used in the first modified layer includes the first modified component (the first modified component is an amide derivative, wherein the amide derivative is selected from N,N′-(1,2-dihydroxyethylene)acrylamide), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The first modified component, benzoyl peroxide, and solvent, by mass parts, are: first modified component: benzoyl peroxide: solvent = 6.9:1.2:240. The treatment conditions for the first modification are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the first modified component to the reboiler coated with the silane layer obtained in step (1) is 4, the immersion temperature is 68°C, and the immersion time is 2.8 hours. The amide group content introduced into the modified matrix after the first modification treatment is 20 mmol / m³. 2 The thickness of the first modified layer is 16 micrometers.

[0105] The product after the first modification treatment was further subjected to a first post-modification treatment to obtain a first post-modified product. The first post-modification agent used in the first post-modification treatment was anhydrous ethanol. The first post-modification treatment was carried out by immersion for 100 minutes. After the first post-modification treatment, the product was dried in nitrogen at 125°C for 12 minutes.

[0106] The product obtained in step (2) after the first modification treatment is subjected to a second modification treatment in step (3) to obtain a second modified product. The solution containing the second modified component consists of the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 22: 2.7: 210. The pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole: mercapto = 3.2: 1. The treatment conditions for the second modification treatment are as follows: the volume ratio (liquid-solid volume ratio) of the solution containing the second modified component to the product obtained in step (2) is 4, the treatment temperature is 73°C, and the treatment time is 2.7 hours. The content of pyrrole groups introduced into the modified matrix after the second modification treatment was 61.3 mmol / m. 2 The thiol group concentration is 18.4 mmol / m³. 2 The thickness of the second modified layer is 7.5 micrometers.

[0107] The product after the second modification treatment in step (3) is subjected to a second post-modification treatment to obtain the product after the second post-modification treatment. The modifying agent used in the second post-modification treatment is anhydrous ethanol. The second post-modification treatment is carried out by immersion, and the immersion time is 100 min. After the second post-modification treatment, it is dried in nitrogen at 124℃ for 13 min.

[0108] The application of the reboiler prepared in Example 1 in the concentration of glycolic acid includes: contacting an aqueous glycolic acid solution with the reboiler to obtain a heat-exchanged aqueous glycolic acid solution. After contacting the concentrated reboiler, the aqueous glycolic acid solution enters the cavity of a distillation column with 4 theoretical plates and a reflux ratio of 0.9. The distillation column is a reactive distillation column. The heating and concentration conditions of the glycolic acid concentrated reboiler are as follows: contact temperature of 60°C and contact pressure (absolute pressure) of 18 kPa.

[0109] In Example 2, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column was 0.42%.

[0110] Example 3

[0111] The raw materials used in this embodiment are the same as those in Embodiment 1.

[0112] According to the method of Example 1, the reboiler in step (1) is a kettle-type reboiler. The silanization treatment adopts the conventional dip-coating method in the art. Before the silanization treatment, the reboiler substrate is first pretreated. Specifically, the reboiler is first ultrasonically polished with a suspension polishing slurry (silicon carbide) at a polishing ultrasonic frequency of 23 kHz. Then, it is ultrasonically cleaned with demineralized water (cleaning ultrasonic frequency of 32 kHz, temperature of 61 ℃, cleaning time of 32 minutes), ultrasonically cleaned with acetone (cleaning ultrasonic frequency of 43 kHz, cleaning temperature of 22 ℃, cleaning time of 21 minutes), ultrasonically cleaned with alkaline solution (wherein, the composition of the alkaline solution, by mass content, is 8.3% sodium hydroxide and 0.7% sodium phosphate, ultrasonic frequency of 52 kHz, alkaline washing temperature of 63 ℃, alkaline washing time of 21 minutes), rinsed with demineralized water (4 times), and dried with nitrogen gas (temperature of 24 ℃). Subsequently, the silane layer was dip-coated (immersion time 2.5 minutes) in a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate) (the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 3:4.5:91, pH value 8.2; the silane reagent solution is prepared by mixing the silane reagent, deionized water and anhydrous ethanol according to the ratio and pre-hydrolyzing for 13 hours). After drying and curing, a silane layer with a thickness of 3.1 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OM) groups of 1.6 was obtained. The drying and curing temperature was 125°C, the drying time was 46 minutes, and the drying atmosphere was nitrogen.

[0113] The solution containing the first modified component used in the first modified layer includes the first modified component (the first modified component is an amide derivative, wherein the amide derivative is selected from N,N′-(1,2-dihydroxyethylene)acrylamide), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The first modified component, benzoyl peroxide, and solvent, by mass parts, are: first modified component: benzoyl peroxide: solvent = 4.3:0.6:260. The treatment conditions for the first modification are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the first modified component to the reboiler coated with the silane layer obtained in step (1) is 2.3, the immersion temperature is 52°C, and the immersion time is 1.7 hours. The amide group content introduced into the modified matrix after the first modification treatment is 8.7 mmol / m³. 2 The thickness of the first modified layer is 12.4 micrometers. The reboiler after the first modification treatment undergoes a first post-modification treatment to obtain the first post-modified product. The first post-modification agent used in the first post-modification treatment is anhydrous ethanol. The first post-modification treatment is performed by immersion for 40 minutes. After the first post-modification treatment, the product is dried in nitrogen at 146°C for 25 minutes.

[0114] The product obtained in step (2) after the first modification treatment is subjected to a second modification treatment in step (3) to obtain a second modified product. The solution containing the second modified component consists of the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 14:1.3:280. Among them, the pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole group: mercapto group = 7.5:1. The treatment conditions for the second modification treatment are as follows: the volume ratio (liquid-solid volume ratio) of the solution containing the second modified component to the product obtained in step (2) is 2.4, the treatment temperature is 57°C, and the treatment time is 1.4 hours. The content of pyrrole groups introduced into the modified matrix after the second modification treatment was 48.5 mmol / m. 2 The thiol content is 7.2 mmol / m 2 The thickness of the second modified layer is 4.4 micrometers.

[0115] The product after the second modification treatment in step (3) is subjected to a second post-modification treatment to obtain the product after the second post-modification treatment. The modifying agent used in the second post-modification treatment is anhydrous ethanol. The second post-modification treatment is carried out by immersion for 40 minutes. After the second post-modification treatment, it is dried in nitrogen at 135°C for 26 minutes.

[0116] The application of the reboiler prepared in Example 3 in the concentration of glycolic acid includes: contacting an aqueous glycolic acid solution with the reboiler to obtain a heat-exchanged aqueous glycolic acid solution. After contacting the concentrated reboiler, the aqueous glycolic acid solution enters the cavity of a distillation column with 9 theoretical plates and a reflux ratio of 2.6. The distillation column is a reactive distillation column. The heating and concentration conditions of the glycolic acid concentrated reboiler are as follows: contact temperature of 85°C and contact pressure (absolute pressure) of 52 kPa.

[0117] In Example 3, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column was 2.7%.

[0118] Example 4

[0119] The method is the same as in Example 2, except that the composition of the raw materials used is different: the glycolic acid solution, by mass percentage, comprises: 23.15% glycolic acid, 0.03% oligomer, and 76.82% water. In the reactive distillation column, the glycolic acid concentrate reboiler is heated and concentrated under the following conditions: contact temperature of 60°C and contact pressure (absolute pressure) of 19 kPa.

[0120] In Example 4, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column was 0.32%.

[0121] Example 5

[0122] The method is the same as in Example 2, except that the composition of the raw materials used is different: the glycolic acid solution, by mass percentage, comprises: 46.53% glycolic acid, 0.12% oligomer, and 53.35% water. In the reactive distillation column, the glycolic acid concentrate reboiler is heated and concentrated under the following conditions: contact temperature of 60°C and contact pressure (absolute pressure) of 17 kPa.

[0123] In Example 5, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column was 0.67%.

[0124] Example 6

[0125] The raw materials used in this embodiment are the same as those in Embodiment 1.

[0126] According to the method of Example 3, step (1) silanization treatment and step (2) first modification treatment are the same, except that the reboiler used is a falling film reboiler made of 304 stainless steel.

[0127] The product obtained in step (2) after the first modification treatment is subjected to a second modification treatment in step (3) to obtain a second modified product. The solution containing the second modified component consists of the second modified component (the second modified component includes pyrrole derivatives and thioether derivatives, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the thioether derivative is selected from bis(4-methacryloylthiophenyl) thioether), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 12.4: 1.3: 280. Among them, the pyrrole derivative and thioether derivative, by molar ratio, are: pyrrole group: thioether = 7.7: 1. The conditions for the second modification treatment are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the second modified component to the product obtained in step (2) is 2.4, the treatment temperature is 57℃, and the treatment time is 1.4 hours. The content of pyrrole groups introduced into the modified matrix after the second modification treatment is 48.9 mmol / m³. 2 The sulfide content is 7.4 mmol / m³. 2 The thickness of the second modified layer is 4.4 micrometers.

[0128] The product after the second modification treatment in step (3) is subjected to a second post-modification treatment to obtain the product after the second post-modification treatment. The modifying agent used in the second post-modification treatment is anhydrous ethanol. The second post-modification treatment is carried out by immersion for 40 minutes. After the second post-modification treatment, it is dried in nitrogen at 135°C for 26 minutes.

[0129] Following the reaction method described in Example 3, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column in Example 6 was 2.7%.

[0130] Example 7

[0131] The raw materials used in this embodiment are the same as those in Embodiment 1.

[0132] The method is the same as in Example 3, except that no post-immersion treatment is performed after either the first or second modification treatment.

[0133] The amide group content introduced into the modified matrix after the first modification treatment was 8.7 mmol / m. 2 The thickness of the first modified layer is 12.4 micrometers, and then it is dried directly in nitrogen at 146°C for 25 minutes.

[0134] The content of pyrrole groups introduced into the modified matrix after the second modification treatment was 48.2 mmol / m. 2 The thiol group concentration is 7.1 mmol / m³. 2 The thickness of the second modified layer is 4.3 micrometers. It is then dried in nitrogen at 135°C for 26 minutes to obtain a glycolic acid concentrate reboiler.

[0135] Following the reaction method described in Example 3, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column in Example 7 was 2.8%.

[0136] Comparative Example 1

[0137] The method is the same as in Example 3, except that a commercially available kettle reboiler is used, and the reboiler material is 316L.

[0138] The oligomer content in the glycolic acid concentrate obtained from the bottom of the distillation column in Comparative Example 1 was 20.4%.

[0139] Comparative Example 2

[0140] The method is the same as in Example 3, except that a commercially available falling film reboiler is used, and the reboiler material is 316L.

[0141] The oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column in Comparative Example 2 was 15.5%.

[0142] Comparative Example 3

[0143] The method is the same as in Example 3, except that a commercially available vertical thermosiphon reboiler is used, and the reboiler material is 316L.

[0144] The oligomer content in the glycolic acid concentrate obtained from the bottom of the distillation column in Comparative Example 3 was 17.2%.

[0145] Comparative Example 4

[0146] The raw materials used in this comparative example are the same as those in Example 1.

[0147] Following the method in Example 3, only the first modification treatment was performed, resulting in an amide group content of 8.7 mmol / m. 2 A glycolic acid concentrator and reboiler with a first modified layer thickness of 12.4 micrometers.

[0148] Following the reaction method described in Example 3, the oligomer content in the concentrated glycolic acid obtained from the bottom of the distillation column in Comparative Example 4 was 9.7%.

[0149] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A reboiler, characterized in that, The reboiler includes a reboiler substrate and a silane layer, a first modified layer, and a second modified layer coated sequentially from the inside to the outside of the outer surface of the reboiler substrate; the first modified layer contains amide groups, and the second modified layer contains pyrrole groups, as well as mercapto groups and / or thioethers. In the first modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of amide groups is 6-21.2 mmol / m². 2 ; In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate, the content of pyrrole groups is 45-63 mmol / m². 2 The content of thiol groups and / or thioethers is 5-40 mmol / m 2 .

2. The reboiler according to claim 1, wherein, The thickness of the first modified layer is 10-18 micrometers.

3. The reboiler according to claim 2, wherein, The thickness of the second modified layer is 3-8 micrometers.

4. The reboiler according to any one of claims 1-3, wherein, The reboiler base is at least one of the following: in-tank boiling reboiler, circulating reboiler, and falling film reboiler. And / or, the material of the reboiler substrate is metal.

5. The reboiler according to claim 4, wherein, The in-tank boiling reboiler is a kettle-type reboiler and / or an internal reboiler, and the circulating reboiler is selected from at least one of a vertical thermosiphon reboiler, a horizontal thermosiphon reboiler, and a pump-forced circulating reboiler.

6. The reboiler according to claim 4, wherein, In the silane layer, the molar ratio of the -Si-O-Si- group to the -Si-OM group is 1.3-4.3; wherein M is a metal derived from the reboiler substrate; And / or, the thickness of the silane layer is 2-6.3 micrometers; And / or, the silane layer is provided with at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate, and 3-(isobutenoyloxy)propyltrimethoxysilane.

7. The reboiler according to any one of claims 1-3, wherein, In the first modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of amide groups is 13-21.2 mmol / m². 2 .

8. The reboiler according to any one of claims 1-3, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate, the content of pyrrole groups is 54-63 mmol / m². 2 The content of thiol groups and / or thioethers is 12-40 mmol / m 2 .

9. The reboiler according to any one of claims 1-3, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of thiol groups is 5-20 mmol / m². 2 The sulfide content is 5-20 mmol / m³. 2 .

10. The reboiler according to claim 8, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of thiol groups is 12-20 mmol / m². 2 The sulfide content is 12-20 mmol / m³. 2 .

11. A method for preparing a reboiler, wherein, The method includes: (1) The reboiler substrate is subjected to silanization treatment to obtain a reboiler substrate coated with a silane layer; (2) The reboiler substrate coated with the silane layer is subjected to a first modification treatment using the first modification component to obtain the first modified reboiler substrate; (3) The reboiler matrix after the first modification treatment is subjected to a second modification treatment using a second modification component to obtain a reboiler; The first modified component contains an amide group, and the second modified component contains a pyrrole group, as well as a mercapto group and / or a thioether; The first modification treatment and the second modification treatment cause the outer surface of the reboiler coated with the silane layer to be sequentially coated with the first modification layer and the second modification layer, wherein the first modification layer contains amide groups and the second modification layer contains pyrrole groups, as well as mercapto groups and / or thioethers. In the first modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of amide groups is 6-21.2 mmol / m². 2 ; In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate, the content of pyrrole groups is 45-63 mmol / m². 2 The content of thiol groups and / or thioethers is 5-40 mmol / m 2 .

12. The method according to claim 11, wherein, In step (1), the reboiler substrate is at least one of an in-pool boiling reboiler, a circulating reboiler, and a falling film reboiler. And / or, the material of the reboiler substrate is metal.

13. The method according to claim 12, wherein, In step (1), the in-tank boiling reboiler is a kettle-type reboiler and / or an internal reboiler, and the circulating reboiler is selected from at least one of a vertical thermosiphon reboiler, a horizontal thermosiphon reboiler, and a pump-forced circulating reboiler.

14. The method according to any one of claims 11-13, wherein, In step (1), the thickness of the silane layer is 2-6.3 micrometers; And / or, in step (1), the silanization process includes: contacting the silane reagent solution with the reboiler substrate, and then drying and curing it.

15. The method according to claim 14, wherein, In step (1), the silane reagent solution is obtained by mixing silane reagent, water and anhydrous low alcohol, and then performing pre-hydrolysis.

16. The method according to claim 15, wherein, In step (1), the volume ratio of silane reagent: water: anhydrous low alcohol is (2.8-5.3): (4-7.2): (90-96).

17. The method according to claim 15, wherein, In step (1), the silane reagent is selected from at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate and 3-(isobutenoyloxy)propyltrimethoxysilane.

18. The method according to claim 14, wherein, In step (1), the amount of silane reagent solution used is such that the molar ratio of the group -Si-O-Si- to the group -Si-OM in the prepared reboiler coated with silane layer is 1.3-4.3, where M is a metal from the reboiler substrate.

19. The method according to any one of claims 11-13, wherein, In the first modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of amide groups is 13-21.2 mmol / m². 2 .

20. The method according to any one of claims 11-13, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate, the content of pyrrole groups is 54-63 mmol / m². 2 The content of thiol groups and / or thioethers is 12-40 mmol / m 2 .

21. The method according to any one of claims 11-13, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of thiol groups is 5-20 mmol / m². 2 The sulfide content is 5-20 mmol / m³. 2 .

22. The method according to claim 20, wherein, In the second modified layer, based on the surface area of ​​the dry-based reboiler substrate per square meter, the content of thiol groups is 12-20 mmol / m². 2 The sulfide content is 12-20 mmol / m³. 2 .

23. The method according to any one of claims 11-13, wherein, In step (2), the first modification treatment includes: contacting the solution containing the first modified component with a reboiler coated with a silane layer.

24. The method according to claim 23, wherein, In step (2), the mass ratio of the first modified component to the first initiator to the first solvent in the solution containing the first modified component is (4-7.2):(0.4-1.4):(230-273).

25. The method according to claim 24, wherein, In step (2), the first solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene.

26. The method according to any one of claims 11-13, wherein, In step (2), the amide group is provided by an amide derivative.

27. The method according to claim 26, wherein, In step (2), the amide group is provided by at least one of N,N'-[ethylenedi(oxymethylene)] bis(acrylamide), N,N'-(1,2-dihydroxyethylene) bisacrylamide and hexamethylenebisacrylamide.

28. The method according to claim 23, wherein, In step (2), the first modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the first modified component to the reboiler coated with the silane layer in step (1) is 2-5, the soaking temperature is 50-70℃, and the time is 1.5-3h.

29. The method according to any one of claims 11-13, wherein, In step (3), the second modification treatment includes contacting the solution containing the second modified component with the first modified product.

30. The method according to claim 29, wherein, In step (3), the mass ratio of the second modified component to the second initiator to the second solvent in the solution containing the second modified component is (12-23): (1-3): (150-300).

31. The method according to claim 30, wherein, In step (3), the second solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene.

32. The method according to any one of claims 11-13, wherein, In step (3), the pyrrole group is provided by a pyrrole derivative.

33. The method according to claim 32, wherein, In step (3), the pyrrole group is provided by at least one of methyl 4-vinyl-1H-pyrrole-3-carboxylate, methyl 5-vinyl-1H-pyrrole-2-carboxylate, 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, 5-allyl-4-methoxy-1,5-dihydro-2H-pyrrole-2-one, 1-allyl-2-cyclopentyl-1H-pyrrole, 1-(1-phenylvinyl)pyrrole, 3-isopropenyl-1-methyl-pyrrole, and 1-allyl-2-isopropenyl-1H-pyrrole.

34. The method according to any one of claims 11-13, wherein, In step (3), the thiol group and / or thioether are provided by thiol derivatives and / or thioether derivatives.

35. The method according to claim 34, wherein, In step (3), the mercapto group and / or thioether are provided by bis(4-methacryloylthiophenyl) thioether and / or allyl 2-mercaptopropionate.

36. The method according to any one of claims 11-13, wherein, In step (3), in the second modified component, the molar ratio of pyrrole: mercapto and / or thioether is (3-8):

1.

37. The method according to claim 29, wherein, In step (3), the second modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the second modified component to the product obtained from the first modification treatment is 2-5, the soaking temperature is 55-75℃, and the time is 1-3h.

38. The method according to any one of claims 11-13, wherein, The method further includes immersing each of the first and second modification treatments separately in a post-treatment agent for post-treatment.

39. The method according to claim 38, wherein, The post-treatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol and anhydrous acetone; And / or, the conditions for the post-soaking treatment include: soaking time of 30-300 min.

40. The method according to claim 39, wherein, The post-treatment agent is anhydrous ethanol.

41. The application of the reboiler according to any one of claims 1-10 or the reboiler prepared by the preparation method according to any one of claims 11-40 in the concentration of hydroxy fatty acid solutions.

42. The application according to claim 41, wherein, The reboiler is used in the heating and concentration of aqueous glycolic acid.

43. The application according to claim 42, wherein, An aqueous solution of glycolic acid is contacted with a reboiler to obtain a concentrated glycolic acid solution.

44. The application according to claim 43, wherein, The contact conditions include: a contact temperature of 50-100℃ and a pressure of 5-100 kPa measured by an absolute pressure gauge; And / or, after contacting the aqueous solution of glycolic acid with the reboiler, it enters the distillation column for distillation separation.

45. The application according to claim 44, wherein, The theoretical plate number of the distillation column is 3-10, and the reflux ratio is 0.5-3; And / or, the distillation column is a reactive distillation column and / or a dehydration column; And / or, the oligomer content in the reaction product after contact is not higher than 5%.

46. ​​The application according to claim 45, wherein, The mass content of oligomers in the reaction products after contact is no higher than 2%.

47. The application according to claim 46, wherein, The mass content of oligomers in the reaction products after contact is no higher than 0.5%.