An improved method for preparing squaric acid

Abstract

The invention discloses an improved method for preparing square acid, wherein perchloro-1,3-butadiene, morpholine and alkaline substances are mixed or perchloro-1,3-butadiene, morpholine and alkaline substances are mixed in an organic solvent, the temperature is raised to 85-120 DEG C for reaction for 5-60h, and the filtrate is filtered and taken after the reaction is completed to obtain the first intermediate product, wherein the amount of the alkaline substance is greater than or equal to 0; the first intermediate product is mixed with a weakly acidic catalyst mixture, water is added, and the filtrate is filtered and taken after stirring the reaction, and the obtained filtrate is decompressed and distilled out of impurities, and the filtrate is filtered and taken to obtain the second intermediate product; the second intermediate product is mixed with a strong acid catalyst mixture and water, and the reaction is stirred at reflux, cooled, and filtered to take filter residue to obtain a square acid crude product; the square acid crude product is dissolved in water, and the filtrate is taken after filtering, and the filtrate is decolorized with activated carbon and then filtered and recrystallized to obtain square acid. The invention improves square acid yield and reduces production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to an improved method for preparing squaric acid. Background Art

[0002] Squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione), also known as square acid and square acid, is an important intermediate for the synthesis of medicines, pesticides, photosensitive materials and dyes. At present, the mainstream preparation method of square acid is still stuck in many years ago. For example, perchloro-1.3-butadiene and morpholine are used as raw materials, toluene is used as solvent, and square acid is prepared in HOAc-NaOAc buffer solution and 98% sulfuric acid (catalyst) in sequence. However, this preparation process has many side reactions and the yield is difficult to improve. At present, the research on square acid is more focused on the development of square acid derivatives, while the preparation process related to square acid itself is stagnant. Therefore, it is necessary to improve the preparation method of square acid to increase the yield of square acid and reduce production costs. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide an improved method for preparing squaric acid, thereby increasing the yield and reducing the production cost.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0005] An improved method for preparing squaric acid comprises the following steps:

[0006] (1) mixing perchloro-1,3-butadiene, morpholine and an alkaline substance or mixing perchloro-1,3-butadiene, morpholine and an alkaline substance in an organic solvent, heating to 85-120° C. and reacting for 5-60 hours, filtering and washing the filtrate after the reaction to obtain a first intermediate product solution, wherein the molar ratio of perchloro-1,3-butadiene to morpholine is 1:(3-6), and the amount of the alkaline substance is greater than or equal to 0, wherein the alkalinity of the alkaline substance is stronger than that of morpholine, and the amount of the alkaline substance increases as the amount of morpholine decreases, and the alkaline substance and / or excess morpholine consume all the generated hydrogen chloride;

[0007] (2) mixing the first intermediate product solution with the weakly acidic catalyst mixture, adding water, stirring and reacting at 25 to 100° C. for 4 to 24 hours, filtering and collecting the filtrate to obtain a second intermediate product solution;

[0008] (3) distilling the second intermediate product solution under reduced pressure, mixing it with a strong acid catalyst mixture and water, reacting it under reflux at 80 to 120° C. for 10 to 24 hours, cooling it, filtering out the residue, and obtaining a crude squaric acid;

[0009] (4) Dissolve the crude squaric acid in water, filter and collect the filtrate, decolorize the filtrate with activated carbon, filter and recrystallize to obtain squaric acid.

[0010] Preferably, the alkaline substance comprises one or more of a basic inorganic salt, a basic oxide, an inorganic base or an organic Lewis base containing no active hydrogen.

[0011] More preferably, the molar ratio of perchloro-1,3-butadiene to added morpholine is 1:(3-4), the molar ratio of the alkaline substance to perchloro-1,3-butadiene is (0-4):1, and the amount of the alkaline substance used is not zero.

[0012] Preferably, in step (2), the weakly acidic catalyst mixture comprises a weakly acidic buffer solution and / or a weakly acidic solid acid. When the weakly acidic catalyst mixture is a weakly acidic solid acid, an organic solvent needs to be added to completely immerse the weakly acidic solid acid.

[0013] More preferably, the weakly acidic buffer solution includes one or more of HOAc-NaOAc buffer solution, citric acid / sodium citrate buffer solution, sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution, and citric acid / sodium dihydrogen phosphate buffer solution;

[0014] The weak solid acid includes one or more of silicate substances, silicon oxide substances, aluminum oxide, titanium dioxide, acidic cationic resins, supported solid acids, and the like.

[0015] More preferably, in step (2), when the weakly acidic catalyst mixture is a weakly acidic buffer solution, the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 0;

[0016] When the weakly acidic catalyst mixture is a mixture of a weakly acidic solid acid and an organic solution, the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 1.

[0017] Preferably, the strong acid catalyst mixture includes one or both of a strong acid solution and a strong solid acid.

[0018] More preferably, the strong acid solution includes any one of 98% sulfuric acid solution, concentrated hydrochloric acid solution, concentrated nitric acid solution and concentrated phosphoric acid solution;

[0019] The strong solid acid includes one or more of phosphotungstic acid, supported phosphotungstic acid catalyst, supported phosphomolybdic acid catalyst, acidic cationic resin, solid superacid and the like.

[0020] More preferably, in step (3), the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 3.

[0021] Preferably, the organic solvent includes one or more of aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, ether solvents, ester solvents, halogenated hydrocarbon solvents, alcohol solvents, ketone solvents or diol derivative solvents.

[0022] More preferably, the organic solvent in step (1) is the same as or different from the organic solvent in step (2); when the organic solvent in step (1) is different from the organic solvent in step (2), after the reaction in step (1) is completed, the organic solvent is first removed by distillation under reduced pressure, and then filtered, and after filtering, the filter residue is washed with the organic solvent in step (2).

[0023] Beneficial effects:

[0024] According to the present invention, the hydrogen chloride generated by the consumption reaction of alkaline substances can be used, thereby avoiding excessive consumption of morpholine, a high-cost raw material, and reducing the raw material cost. In addition, a weak acid catalyst mixture and a strong acid catalyst mixture are used in subsequent reactions, so that the yield of the square acid is improved, and the production cost is significantly reduced, which is beneficial to the development of square acid related industries. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below. Obviously, the following descriptions are only some embodiments of the present invention, and for those of ordinary skill in the art, other implementation methods can also be obtained based on these embodiments without creative work.

[0026] The present invention provides an improved method for preparing squaric acid, comprising the following steps:

[0027] (1) mixing perchloro-1,3-butadiene, morpholine and an alkaline substance or mixing perchloro-1,3-butadiene, morpholine and an alkaline substance in an organic solvent, heating to 85-120° C. and reacting for 5-60 hours, filtering and collecting the filtrate after the reaction to obtain a first intermediate product solution, wherein the molar ratio of perchloro-1,3-butadiene to morpholine is 1:(3-6), and the amount of the alkaline substance is greater than or equal to 0, wherein the alkalinity of the alkaline substance is stronger than that of morpholine, and the amount of the alkaline substance increases as the amount of morpholine decreases, and the alkaline substance and / or excess morpholine consume all the generated hydrogen chloride;

[0028] (2) mixing the first intermediate product solution with the weakly acidic catalyst mixture, adding water, stirring and reacting at 25-100° C. for 4-24 hours, filtering and collecting the filtrate, distilling the obtained filtrate under reduced pressure to remove impurities, and filtering and collecting the filtrate to obtain the second intermediate product;

[0029] (3) mixing the second intermediate product solution with a mixture of a strong acid catalyst and water, refluxing with stirring, reacting at 80 to 120° C. for 10 to 24 hours, cooling, filtering and collecting the residue to obtain a crude squaric acid;

[0030] (4) The crude product of squaric acid is dissolved in water, filtered, and the filtrate is collected. The filtrate is decolorized by activated carbon, filtered, and recrystallized to obtain squaric acid.

[0031] The reaction mechanism of the present invention is as follows:

[0032]

[0033] In step (1), three chlorine atoms in perchloro-1,3-butadiene (i.e., hexachloro-1,3-butadiene) are replaced by morpholine to generate a perchloro-1,3-butadiene substituted product, which is a first intermediate product solution. Meanwhile, hydrogen chloride is generated. One molecule of perchloro-1,3-butadiene generates three molecules of hydrogen chloride, which are consumed by the alkaline substance and / or excess morpholine.

[0034] In step (2), the first intermediate product solution is mixed with a weak acid catalyst mixture to undergo a cyclization reaction to obtain a second intermediate product. During this process, morpholine is regenerated and the morpholine reacts with the weak acid catalyst mixture to be removed.

[0035] In step (3), the second intermediate product solution is mixed with a strong acid catalyst mixture, and reacts to generate square acid under the catalytic action.

[0036] Specifically, in step (1), the molar ratio of perchloro-1,3-butadiene to morpholine participating in the main reaction is 1:3, and the excess morpholine consumes hydrogen chloride. Similarly, the alkaline substance also consumes hydrogen chloride. For ease of explanation, taking 1 mol of perchloro-1,3-butadiene as an example, 3 mol of morpholine participating in the main reaction (i.e., the reaction to generate the first intermediate product) is required to generate 3 mol of hydrogen chloride. When the amount of morpholine added is greater than 3 mol, the excess morpholine reacts with the hydrogen chloride generated by the main reaction to generate morpholine hydrochloride. The addition of a more alkaline alkaline substance is also for the purpose of consuming hydrogen chloride, including the following situations:

[0037] When the molar ratio of perchloro-1,3-butadiene to added morpholine is 1:6, at this time, the hydrogen chloride generated by the reaction is all consumed by the excess morpholine, and there is no need to add alkaline substances. Taking 1mol perchloro-1,3-butadiene as an example, 3mol of morpholine participates in the main reaction, and the generated 3mol of hydrogen chloride is consumed by the excess 3mol of morpholine, and all morpholine hydrochloride is generated. In step (1), the reaction system is an organic phase, which cannot dissolve morpholine hydrochloride, so the morpholine hydrochloride is separated from the first intermediate product solution by filtering.

[0038] When the molar ratio of perchloro-1,3-butadiene to added morpholine is 1:3, at this time, all the added morpholine participates in the main reaction. In order to avoid the consumption of morpholine by hydrogen chloride, the present invention adds an alkaline substance to consume hydrogen chloride. The alkalinity of the alkaline substance needs to be stronger than morpholine, otherwise morpholine hydrochloride is preferentially generated, resulting in insufficient morpholine required for the substitution reaction and incomplete reaction of perchloro-1,3-butadiene. The alkaline substance includes an alkaline inorganic salt, an alkaline oxide, an inorganic base or an organic Lewis base without active hydrogen.

[0039] For example, the alkaline inorganic salt can be a strong base and weak acid salt, such as carbonate, bicarbonate, metal sulfide, hypochlorite, etc. Preferably, the alkaline inorganic salt can be sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium sulfide, potassium sulfide, etc. The alkaline inorganic salt reacts with hydrogen chloride to produce salt and gas and / or water. The salt exists in the reaction system in a solid form, which is convenient for subsequent separation. The generated gas leaves the system, and if water is generated, it can be removed later.

[0040] The inorganic base can be potassium hydroxide, sodium hydroxide, etc. The inorganic base reacts with hydrogen chloride to generate salt and water. The salt exists in the reaction system in a solid form, which is convenient for subsequent separation. The water is removed in the subsequent reduced pressure distillation.

[0041] In the present invention, the organic Lewis base containing no active hydrogen may be triethylamine, 1,8-diazabicyclo[5.4.0]undecene-7, 1,4-diazabicyclo[2.2.2]octane, etc. Similar to other types of alkaline substances, the organic Lewis base selected in the present invention reacts with hydrogen chloride, and the organic hydrochloride generated is also present in the system in a solid form, which is convenient for subsequent filtration and separation. The excess organic Lewis base is also evaporated in the reduced pressure distillation of step (2) and removed from the reaction system.

[0042] Organic Lewis bases containing active hydrogen will react with perchloro-1,3-butadiene.

[0043] The price of morpholine is relatively expensive. The present invention adopts a relatively low-priced alkaline substance to avoid the consumption of morpholine, which is beneficial to significantly reduce the production cost.

[0044] Due to space limitations, the present invention lists some examples of alkaline substances. It is easy to understand that the alkaline substances of the present invention should not be limited to the above-mentioned substances. In the present invention, any alkaline substance that meets the following conditions can be applied to the present invention: the alkalinity is stronger than morpholine; it does not react with perchloro-1,3-butadiene, morpholine, and organic solvents; it does not decompose at the reaction temperature; the hydrochloride generated by the reaction with hydrogen chloride exists in the reaction system in a solid form; and the liquid alkaline substance can be removed by reduced pressure distillation in step (2).

[0045] Taking the alkaline substance as sodium carbonate as an example, in step (1), sodium carbonate reacts with hydrogen chloride to generate sodium chloride, carbon dioxide and water. Since perchloro-1,3-butadiene and morpholine are both organic substances, sodium carbonate and sodium chloride cannot be dissolved and can only exist in solid form. Carbon dioxide evaporates and leaves the reaction system, and water is miscible with the raw materials. The filtering operation of step (1) separates sodium chloride and the remaining unreacted sodium carbonate from the first intermediate product solution, and the generated water is removed by reduced pressure distillation in step (2).

[0046] Taking the alkaline substance as triethylamine as an example, in step (1), liquid triethylamine is miscible with the reaction raw material, triethylamine reacts with hydrogen chloride to generate triethylamine hydrochloride, and triethylamine hydrochloride exists in the system in a solid form. The triethylamine hydrochloride can be separated from the first intermediate product solution by filtering operation, and the excess triethylamine is removed by reduced pressure distillation in step (2). The triethylamine hydrochloride generated by the present invention has a high purity and can be sold as a product, further improving the economic benefit.

[0047] It should be noted that if a liquid alkaline substance, such as triethylamine, is added in step (1), the present invention can also be carried out normally and with better effect by adopting a reaction temperature slightly higher than the boiling point of triethylamine (such as 100-120° C.) under the condition of reflux stirring reaction. Triethylamine does not decompose within the reaction temperature range of the present invention.

[0048] The input amount of the alkaline substance is related to perchloro-1,3-butadiene, and the input amount of the alkaline substance is greater than or equal to the amount of the alkaline substance required to consume hydrogen chloride. Preferably, the input amount of the alkaline substance is equal to the amount of the alkaline substance required to consume hydrogen chloride.

[0049] When the molar ratio of perchloro-1,3-butadiene to added morpholine is greater than 1:3 and less than 1:6 (for example, the molar ratio is 1:4 or 1:5), the excess morpholine cannot consume all the generated hydrogen chloride, and the added alkaline substance consumes the remaining hydrogen chloride. It is easy to understand that in this case, the more excess morpholine, the less the amount of alkaline substance added.

[0050] In step (1), based on perchloro-1,3-butadiene, the molar ratio of morpholine to perchloro-1,3-butadiene is (3-6):1. For example, when perchloro-1,3-butadiene is 1 mol, the amount of morpholine can be 3 mol, 3.1 mol, 3.2 mol, 3.3 mol, 3.4 mol, 3.5 mol, 3.6 mol, 3.7 mol, 3.8 mol, 3.9 mol, 4.0 mol, 4.1 mol, 4.2 mol, 4.3 mol, 4.4 mol, 4.5mol, 4.6mol, 4.7mol, 4.8mol, 4.9mol, 5.0mol, 5.1mol, 5.2mol, 5.3mol, 5.4mol, 5.5mol, 5.6mol, 5.7mol, 5.8mol, 5.9mol, 6.0mol, more preferably, the molar ratio of morpholine to perchloro-1,3-butadiene is (3-4):1, and morpholine is slightly excessive to ensure that perchloro-1,3-butadiene reacts completely and hydrogen chloride is consumed by sufficient alkaline substance.

[0051] Preferably, based on perchloro-1,3-butadiene, the molar ratio of the alkaline substance to perchloro-1,3-butadiene is (0-4):1. It is easy to understand that when the amount of alkaline substance added is 0, it means that the hydrogen chloride is completely consumed by the excess morpholine. When the amount of alkaline substance added reaches the maximum value, the hydrogen chloride is completely consumed by the alkaline substance, and the alkaline substance is slightly excessive.

[0052] For example, 1 mol of perchloro-1,3-butadiene generates 3 mol of hydrogen chloride. When 1 mol of alkaline substance can completely react with 1 mol of hydrogen chloride, the molar ratio of alkaline substance to perchloro-1,3-butadiene is (3-4):1 based on perchloro-1,3-butadiene, and the alkaline substance is slightly excessive to ensure that the hydrogen chloride is completely consumed; when 1 mol of alkaline substance can completely react with 2 mol of hydrogen chloride, the molar ratio of alkaline substance to perchloro-1,3-butadiene is (1.5-2):1 based on perchloro-1,3-butadiene; when 1 mol of alkaline substance can completely react with 3 mol of hydrogen chloride, the molar ratio of alkaline substance to perchloro-1,3-butadiene is (1-1.5):1 based on perchloro-1,3-butadiene.

[0053] In step (1), the reaction temperature and the reaction time are in a negatively correlated relationship, that is, when the reaction temperature is higher, the reaction time is generally shorter to avoid more side reactions. For example, when the final reaction temperature is 85°C, the reaction time is close to 60h. It is easy to understand that the choice of reaction temperature is also related to the properties of the alkaline substance, and the decomposition of the alkaline substance should be avoided under the conditions of the reaction temperature.

[0054] In step (1), perchloro-1,3-butadiene, morpholine and alkaline substances can be directly mixed for reaction, or reacted in an organic solvent. Specifically, when the raw materials are not reacted in an organic solvent, the temperature can be first raised to 40-60° C. for reaction, and then raised to 85-120° C. for reaction to reduce side reactions. Alternatively, when the raw materials are reacted in an organic solvent, the temperature can be directly raised to 85-120° C. for reaction. It is easy to understand that when the raw materials are mixed with an organic solvent for reaction, the temperature can also be first raised to 40-60° C., and then raised to 85-120° C. for reaction.

[0055] In step (1), when an organic solvent is used to mix the raw materials, after the reaction is completed, the organic solvent is mixed with the first intermediate product and other substances. The organic solvent can be evaporated before filtering, and then the filtering operation is performed. The same or different organic solvent is then used to wash the filter residue. The organic solvent used to wash the filter residue will enter step (2) and be removed by a subsequent reduced pressure distillation operation.

[0056] It is easy to understand that in step (1), if the organic solvent used in the reaction is the same as the organic solvent used to wash the filter residue after filtration, the operation of distilling out the organic solvent in step (1) can be omitted. If they are different, the former organic solvent must be distilled out before the latter organic solvent can be used.

[0057] In the present invention, the organic solvent cannot dissolve morpholine hydrochloride, and the organic solvent includes aromatic hydrocarbon solvents (such as benzene, toluene, xylene, etc.), aliphatic hydrocarbon solvents (pentane, hexane, octane, etc.), alicyclic hydrocarbon solvents (cyclohexane, cyclohexanone, toluene cyclohexanone, etc.), ether solvents (ethyl ether, propylene oxide, etc.), ester solvents (methyl acetate, ethyl acetate, propyl acetate, etc.), glycol derivative solvents (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, etc.), halogenated hydrocarbon solvents (chlorobenzene, dichlorobenzene, dichloromethane, etc.), alcohol solvents (methanol, ethanol, isopropanol, etc.), ketone solvents (acetone, methyl butyl ketone, methyl isobutyl ketone, etc.) or other solvents (acetonitrile, pyridine, phenol, etc.).

[0058] Preferably, when the raw materials are mixed with an organic solvent in step (1), the organic solvent is an aromatic hydrocarbon solvent, an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an ether solvent, an ester solvent or a diol derivative solvent.

[0059] More preferably, the organic solvent of the present invention is an aromatic hydrocarbon solvent or an ester solvent, such as toluene, ethyl acetate, propyl acetate, butyl acetate, etc. It is easy to understand that when the organic solvent is an ester solvent, such as butyl acetate, under alkaline conditions, the ester organic matter may be partially hydrolyzed, but in the present invention, no water is added as a raw material in step (1), and water is generated by the reaction of alkaline substances with hydrogen chloride, and the alkaline substances have been consumed, so the effect on the ester solvent is small and can be ignored.

[0060] In step (2), the weak acid catalyst mixture not only plays a role in catalyzing the cyclization, but also plays a role in eliminating the generated morpholine, thereby increasing the yield of the second intermediate product. It is easy to understand that the amount of the weak acid catalyst mixture used is greater than the amount of morpholine produced by the weak acid catalyst mixture in step (2).

[0061] In the present invention, the weak acid catalyst mixture can be a weak acid buffer solution or a weak acid solid acid.

[0062] Weakly acidic buffer solutions include HOAc-NaOAc buffer solution, citric acid / sodium citrate buffer solution, sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution or citric acid / sodium dihydrogen phosphate buffer solution.

[0063] When the weak acid catalyst mixture is a weak acidic buffer solution, taking HOAc-NaOAc buffer solution as an example, in step (2), a sufficient amount of 1 mol / L HOAc-NaOAc buffer solution is added to mix with the first intermediate product, and the mixture is stirred at 60° C. for 16 h, and impurities such as water and organic solvent are distilled off under reduced pressure to obtain a second intermediate product solution.

[0064] The higher the concentration of the buffer solution, the stronger the buffering capacity. Preferably, the concentration of the buffer solution is greater than or equal to 1 mol / L, such as 1 to 3 mol / L. More preferably, based on 1 mol of perchloro-1,3-butadiene, the amount of solute in the buffer solution is greater than or equal to 2 mol, and the pH value of the buffer solution is between 3 and 6.

[0065] After the water is distilled off in step (2), the morpholine acetate generated by the reaction of morpholine with the buffer solution is insoluble in organic matter and precipitates out of the system. The morpholine acetate is separated from the second intermediate product by filtration.

[0066] When the weak acid catalyst mixture is a weak acid solid acid, the weak acid solid acid is insoluble in organic matter or water, which is convenient for subsequent separation and reuse, reduces processing costs, and greatly reduces the generation of waste liquid and waste acid. It should be noted that the salt generated by the reaction of the weak acid solid acid and morpholine can be soaked in hydrochloric acid to regenerate the weak acid solid acid after being recovered from the system, or it can be roasted to regenerate the weak acid solid acid.

[0067] In step (2), as long as the weak acid solid acid meets the following conditions, it is applicable to the present invention: the weak acid solid acid is a weak acid solid acid catalyst, which has a catalytic effect on the reaction of converting the first intermediate product into the second intermediate product; it does not dissolve in the reaction system and remains in a solid state; and it can react with morpholine to remove morpholine.

[0068] Preferably, the weakly acidic solid acid comprises one or more of silicate materials, silicon oxide materials, alumina, titanium dioxide, acidic cationic resins, supported solid acids, etc., wherein silicate materials include zeolite, silica-alumina molecular sieve, ZSM-5, KL molecular sieve, diatomaceous earth, kaolin, activated clay, attapulgite, bentonite, montmorillonite, hydroxyapatite, etc.; silicon oxide materials include multi-level porous silica, silica gel, pure silicon molecular sieve, SBA-15, ZSM-5, MCM-41, etc.; supported solid acids include weakly acidic supported phosphotungstic acid catalysts, HF / Al2O3, HCl / silica gel, H2SO4 / silica gel, H2SO4 / diatomaceous earth, etc. It should be noted that HF / Al2O3, HCl / silica gel, H2SO4 / silica gel, H2SO4 / diatomaceous earth are formed by mixing acid with a carrier.

[0069] It should be noted that the amount of weak acid solid acid is related to the amount of morpholine produced. The weak acid solid acid consumes morpholine and plays a catalytic role. Therefore, the amount of weak acid solid acid is greater than the amount of morpholine produced in step (2). Preferably, based on 1 mol of perchloro-1,3-butadiene, the amount of weak acid solid acid used is greater than or equal to 210g.

[0070] In step (2), the role of adding an organic solvent is to submerge the weak acid solid acid, which is convenient for subsequent stirring reaction. After the reaction is completed, the filtering operation can separate the weak acid solid acid and the corresponding generated salt from the second intermediate product, and the organic solvent is evaporated in the subsequent vacuum distillation. If the organic solvent in step (1) is retained and enters step (2), and the weak acid solid acid has been completely submerged, no organic solvent needs to be added.

[0071] In step (2), the water added is a reactant, and the molar ratio of the water added to perchloro-1,3-butadiene is greater than or equal to 0. The water added is related to the type of the weakly acidic catalyst mixture. Specifically, when the weakly acidic catalyst mixture is a weakly acidic buffer solution, the water in the buffer solution can participate in the main reaction (i.e., the reaction of generating the second intermediate product), so the water added can be determined according to the amount of the buffer solution added, and even the amount of water added can be 0; when the weakly acidic catalyst mixture is a weakly acidic solid acid, there is a lack of water participating in the reaction at this time, so it is necessary to add a sufficient amount or even an excess of water, and the molar ratio of the water added to perchloro-1,3-butadiene is greater than or equal to 1, that is, based on 1 mol of perchloro-1,3-butadiene, the water added in step (2) is greater than or equal to 18g. It is easy to understand that when the weakly acidic catalyst mixture is a weakly acidic buffer solution, the excess water in the buffer solution is removed in the subsequent reduced pressure distillation.

[0072] It is easy to understand that if an excessive amount of liquid alkaline substance is added in step (1), the weakly acidic catalyst mixture will be consumed accordingly in step (2), and the input amount of the weakly acidic catalyst mixture will increase accordingly. Therefore, it is preferred that an excessive amount of alkaline substance is not added in step (1).

[0073] In step (3), the strong acid catalyst mixture mainly plays a catalytic role. The strong acid catalyst mixture can be a strong acid solution or a strong acid solid acid.

[0074] The strong acid solution includes any one of a 98% sulfuric acid solution, a concentrated hydrochloric acid solution, a concentrated nitric acid solution, and a concentrated phosphoric acid solution.

[0075] When the strong acid catalyst mixture is a strong acid solution, taking 98% sulfuric acid solution as an example, in step (3), the second intermediate product is mixed with a sufficient amount of the strong acid solution, and then water is added, refluxed with stirring, reacted at 115° C. for 24 hours, cooled, and filtered to obtain the residue to obtain a crude square acid.

[0076] The morpholine hydrochloride generated in step (3) will dissolve in water, and the morpholine hydrochloride and the strong acid solution are mixed and separated from the crude squaric acid by filtration.

[0077] In step (3), the strong acid solid acid is insoluble in water or organic matter, and mainly plays a catalytic role to improve the yield of square acid. Preferably, the strong acid solid acid is a strongly acidic solid acid catalyst. In this step, morpholine hydrochloride is produced during the conversion of the second intermediate product into square acid. The morpholine hydrochloride is soluble in water and insoluble in the organic phase of the reaction system. The morpholine hydrochloride can be removed in the subsequent filtering operation.

[0078] Preferably, the strong acid solid acid includes one or more of phosphotungstic acid, supported phosphotungstic acid catalyst, supported phosphomolybdic acid catalyst, acidic cationic resin, solid superacid, etc., wherein the supported phosphotungstic acid catalyst includes phosphotungstic acid modified SBA-15, phosphotungstic acid modified MCM-41, silicotungstic acid modified SBA-15, etc.; the solid superacid includes SO4 2- / TiO2、SO4 2- / ZrO2、SO4 2- / Fe2O3、SO4 2- / Al2O3, etc.; supported phosphomolybdic acid catalysts include phosphomolybdic acid modified MCM-41, etc. More preferably, based on 1 mol of perchloro-1,3-butadiene, the amount of the strong acid solid acid used is greater than or equal to 12.8 g.

[0079] Water also needs to be added in step (3). The purpose of adding water is different from that in step (2). In combination with the reaction mechanism, it can be seen that morpholine hydrochloride will be generated when the second intermediate product is converted into square acid. In step (3), the molar ratio of the added water to perchloro-1,3-butadiene is greater than or equal to 3. Water not only participates in the reaction, but also can be used as a solvent for removing morpholine hydrochloride. The amount of water added varies depending on the type of strong acid catalyst mixture used, as shown below:

[0080] When the strong acid catalyst mixture is a strong acid solution, the amount of water added in step (3) is as small as possible. Based on perchloro-1,3-butadiene, the molar ratio of water participating in the reaction in step (3) to perchloro-1,3-butadiene is 3. The solvent water in the strong acid solution can be used as a solvent for dissolving morpholine hydrochloride. Therefore, the molar ratio of the added water to perchloro-1,3-butadiene is greater than or equal to 3.

[0081] When the strong acid catalyst mixture is a strong acid solid acid, the water added in step (3) not only participates in the reaction, but also dissolves the generated morpholine hydrochloride, so more water needs to be added. Specifically, based on perchloro-1,3-butadiene, the molar ratio of water participating in the reaction in step (3) to perchloro-1,3-butadiene is greater than or equal to 3, that is, when there is 1 mol of perchloro-1,3-butadiene as a raw material, at least 3 mol (i.e. 54 g) of water needs to be added in step (3) as a reaction substance; and more water is needed to dissolve morpholine hydrochloride in step (3). Based on 1 mol of perchloro-1,3-butadiene, the morpholine hydrochloride generated in step (3) requires at least 125 g (about 7 mol) of water to dissolve. Therefore, in step (3), the molar ratio of water added to perchloro-1,3-butadiene is greater than or equal to 10. If based on 1 mol of perchloro-1,3-butadiene, the water added in step (3) is greater than or equal to 180 g.

[0082] It should be noted that, in the present invention, if a buffer solution is used in step (2), the reaction is not greatly affected, but more waste liquid is generated. If a weak acid solid acid is used in step (2), the waste liquid treatment cost can be greatly reduced, and the weak acid solid acid can be recycled, which is conducive to reducing production costs. Similarly, if a strong acid solution is used in step (3), the recycling of the waste acid will increase the processing cost. If a strong acid solid acid is used in step (3), the processing cost can be reduced, and the strong acid solid acid can be recycled.

[0083] The solubility of square acid at room temperature is very low, and the solubility is only 20g / L under 30°C. In step (3), the square acid generated mainly exists in the form of solid. When the strong acid catalyst mixture is a strong acid solid acid, after filtering in step (3), the filter residue is a mixture of strong acid solid acid and square acid. When the strong acid catalyst mixture is a strong acid solution, after filtering in step (3), the filter residue is mainly square acid. It is easy to understand that since the amount of square acid dissolved in water at room temperature is very small, and the filtrate of step (3) also contains morpholine hydrochloride, it will be time-consuming and labor-intensive to recover the square acid in the aqueous solution. Therefore, the present invention mainly purifies square acid from the filter residue of step (3). In step (4), the square acid crude product is redissolved in a large amount of water. Since the strong acid solid acid is insoluble in water, while the square acid is soluble in water, the square acid is purified, and the strong acid solid acid is recovered and can be reused. The square acid solution is decolorized with activated carbon and then refined by recrystallization to obtain square acid.

[0084] The technical solution of the present invention is described in detail below with specific embodiments.

[0085] Example 1

[0086] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0087] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 10 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0088] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0089] The mixture was redissolved in water and filtered to obtain a filtrate. The filtrate was decolorized with activated carbon and then filtered. After recrystallization, 90 g of white granular square acid was obtained with a yield of 78.95%.

[0090] Example 2

[0091] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of propyl acetate, the temperature was raised to 100° C., and the reaction was performed for 20 hours. After the reaction was completed, the mixture was filtered, and the filtrate was a solution of the first intermediate product;

[0092] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and solvent propyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture including propyl acetate was distilled off under reduced pressure to obtain a second intermediate product;

[0093] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0094] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 91g square acid, and the yield was 79.82%.

[0095] Example 3

[0096] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3.2 mol of triethylamine were mixed in 400 ml of ethylene glycol monobutyl ether, heated to 120° C., reacted for 5 hours, filtered after the reaction was completed, and the filtrate was a solution of the first intermediate product;

[0097] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of ethylene glycol monobutyl ether was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of ethylene glycol monobutyl ether and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0098] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0099] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 85g square acid, with a yield of 74.56%.

[0100] Example 4

[0101] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of xylene, the temperature was raised to 120° C., the reaction was performed for 5 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0102] The solution of the first intermediate product was mixed with 420 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of xylene was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of xylene and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0103] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, the mixture was refluxed and stirred, reacted at 110° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0104] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 84g square acid, with a yield of 73.68%.

[0105] Example 5

[0106] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of pyridine, heated to 110° C., reacted for 7 hours, filtered after the reaction was completed, and the filtrate was a solution of the first intermediate product;

[0107] The solution of the first intermediate product was mixed with 210 g of weak acid solid acid (multi-level porous silica), 20 mL of water was added, and solvent pyridine was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture including pyridine was distilled off under reduced pressure to obtain a second intermediate product;

[0108] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, the mixture was refluxed and stirred, reacted at 110° C. for 10 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0109] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 90g square acid, with a yield of 78.95%.

[0110] Example 6

[0111] 1 mol of perchloro-1,3-butadiene, 3.5 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of 1,4-dioxane, the temperature was raised to 100° C., and the reaction was performed for 20 hours. After the reaction was completed, the mixture was filtered, and the filtrate was a solution of the first intermediate product;

[0112] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent 1,4-dioxane was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of 1,4-dioxane and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0113] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, the mixture was refluxed and stirred, reacted at 90° C. for 20 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0114] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 91g square acid, and the yield was 79.82%.

[0115] Example 7

[0116] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of 1.8-diazabicyclo[5.4.0]undecene-7 were mixed in 400 ml of butyl acetate, heated to 110° C., reacted for 7 hours, filtered after the reaction, and the filtrate was a solution of the first intermediate product;

[0117] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0118] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0119] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 88g square acid, with a yield of 77.19%.

[0120] Example 8

[0121] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of 1,4-diazabicyclo[2.2.2]octane were mixed in 400 ml of butyl acetate, heated to 110° C., reacted for 7 hours, filtered after the reaction was completed, and the filtrate was a solution of the first intermediate product;

[0122] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0123] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0124] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 86g square acid, with a yield of 75.44%.

[0125] Example 9

[0126] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of sodium carbonate (which can be converted into sodium bicarbonate) are mixed in 400 ml of butyl acetate, heated to 110° C., reacted for 7 hours, filtered after the reaction, and the filtrate is a solution of the first intermediate product;

[0127] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0128] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0129] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 78g square acid, and the yield was 68.42%.

[0130] Example 10

[0131] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of potassium hydroxide were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the mixture was filtered, and the filtrate was a solution of the first intermediate product;

[0132] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0133] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0134] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 69g square acid, and the yield was 60.53%.

[0135] Embodiment 11

[0136] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 120° C., and the reaction was performed for 5 hours. After the reaction was completed, the mixture was filtered, and the filtrate was a solution of the first intermediate product;

[0137] The solution of the first intermediate product was mixed with 420 g of weak acid solid acid (silica gel), 20 mL of water was added, and solvent butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture including butyl acetate was distilled off under reduced pressure to obtain a second intermediate product;

[0138] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0139] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 84g square acid, with a yield of 73.68%.

[0140] Example 12

[0141] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0142] The solution of the first intermediate product was mixed with 420 g of a weak acid solid acid (cation exchange resin), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0143] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0144] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 93g square acid, and the yield was 81.58%.

[0145] Embodiment 13

[0146] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0147] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 25° C. for 24 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0148] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0149] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, the white granular crystals and the white solid were refined to obtain square acid to obtain 91g square acid, and the yield was 79.82%.

[0150] Embodiment 14

[0151] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0152] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 100° C. for 4 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0153] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0154] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 85g square acid, with a yield of 74.56%.

[0155] Embodiment 15

[0156] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0157] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0158] The second intermediate product was mixed with 15 g of a strong solid acid (SBA-15 modified with silicotungstic acid), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 18 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0159] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 90g square acid, with a yield of 78.95%.

[0160] Example 16

[0161] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0162] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0163] The second intermediate product was mixed with 14 g of a strong solid acid (MCM-41 modified with phosphomolybdic acid), 282 mL of water was added, the mixture was refluxed and stirred, reacted at 100° C. for 24 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0164] The crude product of square acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate, the filtrate was decolorized with activated carbon and then filtered, and white granular crystals were obtained after recrystallization; the mother liquor was concentrated and cooled to precipitate a white solid, and the white granular crystals and the white solid were refined to obtain square acid to obtain 90g square acid, with a yield of 78.95%.

[0165] Embodiment 17

[0166] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed, the temperature was raised to 100°C, and the reaction was carried out for 16 hours. After the reaction was completed, the temperature was lowered, ethanol was added to dissolve and filtered, and the filtrate was a solution of the first intermediate product;

[0167] The solution of the first intermediate product was mixed with 210 g of weak acid solid acid (multi-level porous silica), 20 mL of water was added, and solvent ethanol was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 10 h, filtered to obtain a filtrate, and then the mixture such as ethanol was distilled off under reduced pressure to obtain a second intermediate product;

[0168] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0169] The mixture was redissolved in water and filtered to obtain a filtrate. The filtrate was decolorized with activated carbon and then filtered. After recrystallization, 95 g of white granular square acid was obtained with a yield of 83.33%.

[0170] Embodiment 18

[0171] In this embodiment, triethylamine is used as the alkaline substance in step (1), which reduces the consumption of morpholine and lowers the production cost.

[0172] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0173] The solution of the first intermediate product was added to 2 L of citric acid / sodium citrate buffer solution (1 mol / L), stirred at 60° C. for 16 h, filtered to obtain a filtrate, and then 1.5 L of water and the like were distilled off under reduced pressure to obtain a second intermediate product;

[0174] 60 mL of concentrated sulfuric acid was added to the second intermediate product, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a crude product of square acid;

[0175] The mixture was redissolved in water, decolorized with activated carbon, and then filtered. After recrystallization, 62 g of white granular square acid was obtained with a yield of 54.38%.

[0176] Embodiment 19

[0177] In this embodiment, weak solid acid and strong solid acid are used in step (2) and step (3), thereby increasing the yield and reducing the processing cost.

[0178] 1 mol of perchloro-1,3-butadiene and 6 mol of morpholine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0179] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 10 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0180] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, refluxed and stirred, reacted at 100° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0181] The mixture was redissolved in water and filtered to obtain a filtrate. The filtrate was decolorized with activated carbon and then filtered. After recrystallization, 90 g of white granular square acid was obtained with a yield of 78.95%.

[0182] Embodiment 20

[0183] In this embodiment, triethylamine is used as the alkaline substance in step (1) to reduce the consumption of morpholine, and weak solid acid is used in step (2) to improve the yield and reduce the processing cost.

[0184] 1 mol of perchloro-1,3-butadiene, 3 mol of morpholine and 3 mol of triethylamine were mixed in 400 ml of butyl acetate, the temperature was raised to 110° C., the reaction was performed for 7 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0185] The solution of the first intermediate product was mixed with 210 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of butyl acetate was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 10 h, filtered to obtain a filtrate, and then the mixture of butyl acetate and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0186] The second intermediate product was added to 282 mL of 4 mol / L sulfuric acid solution, refluxed and stirred, reacted at 100°C for 12 h, and then filtered to precipitate a crude square acid;

[0187] The crude product of squaric acid was dissolved in activated carbon and then filtered to obtain 89 g of white granular squaric acid after recrystallization with a yield of 78.07%.

[0188] Embodiment 21

[0189] In this embodiment, a strong solid acid is used in step (3) to improve the yield and reduce the processing cost.

[0190] 1 mol of perchloro-1,3-butadiene and 6 mol of morpholine were mixed in 400 ml of xylene, the temperature was raised to 120° C., the reaction was performed for 5 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0191] The solution of the first intermediate product was added to 2 L of citric acid / sodium dihydrogen phosphate buffer solution (1 mol / L), stirred at 60° C. for 16 h, filtered to obtain a filtrate, and then 1.5 L of water and the like were distilled off under reduced pressure to obtain a second intermediate product;

[0192] The second intermediate product was mixed with 12.8 g of a strong solid acid (phosphotungstic acid-modified SBA-15), 282 mL of water was added, the mixture was refluxed and stirred, reacted at 110° C. for 12 h, and then filtered to precipitate a mixture of a strong solid acid and a square acid;

[0193] The crude product of squaric acid and the crude product of the mixture of strong acid solid acid were redissolved in water and filtered to obtain a filtrate. The filtrate was decolorized with activated carbon and then filtered. White granular crystals were obtained after recrystallization. The white granular crystals were purified to obtain squaric acid to obtain 84 g of squaric acid, with a yield of 73.68%.

[0194] Embodiment 22

[0195] In this embodiment, weak solid acid is used in step (2) to reduce processing costs.

[0196] 1 mol of perchloro-1,3-butadiene and 6 mol of morpholine were mixed in 400 ml of xylene, the temperature was raised to 120° C., the reaction was performed for 5 hours, and after the reaction was completed, the filtrate was filtered, and the filtrate was a solution of the first intermediate product;

[0197] The solution of the first intermediate product was mixed with 420 g of a weak acid solid acid (multi-level porous silica), 20 mL of water was added, and a solvent of xylene was added to immerse the weak acid solid acid, and the mixture was stirred at 60° C. for 12 h, filtered to obtain a filtrate, and then the mixture of xylene and the like was distilled off under reduced pressure to obtain a second intermediate product;

[0198] The second intermediate product was added to 282 mL of 4 mol / L sulfuric acid solution, and the mixture was stirred under reflux at 110° C. for 12 h, and then filtered to obtain a crude product of square acid;

[0199] The crude product of squaric acid was redissolved in water, decolorized with activated carbon, and then filtered. White granular crystals were obtained after recrystallization. The white granular crystals were purified to obtain squaric acid. 60 g of squaric acid was obtained with a yield of 57.02%.

[0200] Comparative Example 1

[0201] This comparative example is an existing process for preparing square acid.

[0202] In a 3L three-necked flask, 178ml (1.15mol) of perchloro-1,3-butadiene, 602ml (6.90mol) of morpholine and 450ml of toluene were placed, and the mixture was refluxed with stirring for 7h to precipitate a large amount of light yellow solid.

[0203] The mixture was cooled to 80°C, 2000 ml of 1 mol / L HOAc-NaOAc buffer solution was added, and the mixture was stirred at 60°C for 16 h. About 1500 ml of a mixture of toluene, morpholine and water was distilled off under reduced pressure.

[0204] Then slowly add 750 ml of 98% sulfuric acid, reflux and stir for 24 hours, let stand overnight, pour out the upper solution to obtain the mother liquor, and filter to obtain a brown crude product.

[0205] The brown crude product was dissolved in water, decolorized by activated carbon, and recrystallized to obtain white granular crystals. The mother liquor was concentrated and cooled to precipitate some white solids, which were purified, combined and dried to obtain 69.7 g of square acid with a yield of 53.2%.

[0206] According to the comparison between Examples 1-22 and Comparative Example 1, the present invention can significantly improve the yield or reduce the production cost, and is significantly superior to the existing square acid production process in terms of cost reduction and efficiency improvement.

[0207] The embodiments provided by the present invention are described in detail above. Specific examples are used herein to describe the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. An improved method for preparing squaric acid, characterized in that: The following steps are involved: (1) mixing perchloro-1,3-butadiene, morpholine and an alkaline substance or mixing perchloro-1,3-butadiene, morpholine and an alkaline substance in an organic solvent, heating to 85-120° C. and reacting for 5-60 hours, filtering and washing the filtrate after the reaction to obtain a first intermediate product solution, wherein the molar ratio of perchloro-1,3-butadiene to morpholine is 1:(3-6), and the amount of the alkaline substance is greater than or equal to 0, wherein the alkalinity of the alkaline substance is stronger than that of morpholine, and the amount of the alkaline substance increases as the amount of morpholine decreases, and the alkaline substance and / or excess morpholine consume all the generated hydrogen chloride; (2) mixing the first intermediate product solution with the weakly acidic catalyst mixture, adding water, stirring and reacting at 25 to 100° C. for 4 to 24 hours, filtering and collecting the filtrate to obtain a second intermediate product solution; (3) distilling the second intermediate product solution under reduced pressure, mixing it with a strong acid catalyst mixture and water, reacting it under reflux at 80 to 120° C. for 10 to 24 hours, cooling it, filtering out the residue, and obtaining a crude squaric acid; (4) The crude product of squaric acid is dissolved in water, filtered, and the filtrate is collected. The filtrate is decolorized by activated carbon, filtered, and recrystallized to obtain squaric acid.

2. The improved method for preparing squaric acid according to claim 1, characterized in that: The basic substance includes one or more of a basic inorganic salt, a basic oxide, an inorganic base or an organic Lewis base containing no active hydrogen.

3. The improved method for preparing squaric acid according to claim 2, characterized in that: The molar ratio of perchloro-1,3-butadiene to added morpholine is 1:(3-4), the molar ratio of alkaline substance to perchloro-1,3-butadiene is (0-4):1, and the amount of alkaline substance used is not zero.

4. The improved method for preparing squaric acid according to claim 1, characterized in that: In step (2), the weakly acidic catalyst mixture includes a weakly acidic buffer solution and / or a weakly acidic solid acid.

5. The improved method for preparing squaric acid according to claim 4, characterized in that: The weakly acidic buffer solution includes one or more of HOAc-NaOAc buffer solution, citric acid / sodium citrate buffer solution, sodium dihydrogen phosphate / disodium hydrogen phosphate buffer solution and citric acid / sodium dihydrogen phosphate buffer solution; The weak solid acid includes one or more of silicate substances, silicon oxide substances, aluminum oxide, titanium dioxide, acidic cationic resins, supported solid acids, and the like.

6. The improved method for preparing squaric acid according to claim 4, characterized in that: In step (2), when the weakly acidic catalyst mixture is a weakly acidic buffer solution, the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 0; When the weakly acidic catalyst mixture is a mixture of a weakly acidic solid acid and an organic solution, the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 1.

7. The improved method for preparing squaric acid according to claim 1, characterized in that: The strong acid catalyst mixture includes one or both of a strong acid solution and a strong solid acid.

8. The improved method for preparing squaric acid according to claim 7, characterized in that: The strong acid solution includes any one of a 98% sulfuric acid solution, a concentrated hydrochloric acid solution, a concentrated nitric acid solution, and a concentrated phosphoric acid solution.

9. The improved method for preparing squaric acid according to claim 7, characterized in that: The strong solid acid includes one or more of phosphotungstic acid, supported phosphotungstic acid catalyst, supported phosphomolybdic acid catalyst, acidic cationic resin, solid superacid and the like.

10. The improved method for preparing squaric acid according to claim 1, characterized in that: In step (3), the molar ratio of the added water to the perchloro-1,3-butadiene is greater than or equal to 3.

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