Preparation method of 3, 4-dimethyl-1, 2-cyclopentanedione

Abstract

The invention relates to the technical field of preparation of chemical raw materials, in particular to a preparation method of 3, 4-dimethyl-1, 2-cyclopentanedione.3, 4-dimethylcyclohexanol is used as a raw material, and 3, 4-dimethyl-1, 2-cyclopentanedione is generated through oxidation, esterification, cyclization, oximidation and recrystallization; in the oxidation reaction stage, whether the oxidation process meets the standard or not is determined based on the content of 3, 4-dimethylcyclohexanol, parameter adjustment is performed in a targeted manner for the oxidation process which does not meet the standard, and whether the generation process of adipic acid meets the standard or not is determined based on kettle residues in the next production cycle based on the oxidation process which meets the standard. And the generation process which does not meet the standard is adjusted, so that the oxidation yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of chemical raw materials, and in particular to a method for preparing 3,4-dimethyl-1,2-cyclopentanedione. Background Art

[0002] 3,4-Dimethyl-1,2-cyclopentanedione is an important organic compound with a wide range of applications in food, flavors and chemicals. Its unique chemical structure and properties make it a key ingredient in the preparation of spice flavors such as licorice. It is also used in baked goods, frozen dairy products and nuts to enhance the taste and aroma of food.

[0003] The process of preparing 3,4-dimethyl-1,2-cyclopentanedione mainly involves the selection of raw materials, optimization of reaction conditions and purification of products. Traditional preparation methods usually rely on complex chemical reaction steps, such as alkylation, hydrolysis and decarboxylation, which are not only cumbersome to operate, but also easy to introduce impurities, affecting the purity and yield of the product.

[0004] In order to improve the preparation efficiency and product quality, researchers are constantly exploring new preparation methods and optimization strategies. Among them, an effective method is to make the reaction more efficient and controllable by improving the reaction conditions and the selection of catalysts. In addition, by optimizing the purification process, impurities in the product can be further removed and the purity of the product can be improved.

[0005] In recent years, as the concepts of green chemistry and sustainable development have gradually gained popularity, the methods for preparing 3,4-dimethyl-1,2-cyclopentanedione have also paid more attention to environmental protection and energy conservation. For example, more environmentally friendly solvents and catalysts are used to reduce the emission of harmful substances, while improving the selectivity and yield of the reaction to maximize the utilization of resources.

[0006] Chinese Patent Publication No.: CN103483308A discloses a method for preparing 4,5-dimethyl-1,3-dioxol-2-one using carbon dioxide, which isomerizes 3-hydroxy-2-butanone to an enol structure, and then synthesizes a cyclic carbonate compound in one step with non-toxic, non-corrosive, and inexpensive carbon dioxide under alkaline esterification catalytic conditions, and obtains a crude 4,5-dimethyl-1,3-dioxol-2-one through washing, crystallization, filtration or centrifugation steps. The crude product is further recrystallized and purified to obtain the 4,5-dimethyl-1,3-dioxol-2-one product of the present invention. The method conforms to the atomic economic reaction, greatly reduces the generation and emission of by-products such as hydrochloric acid, and is a green, environmentally friendly and safe production process.

[0007] It can be seen that the method for preparing 4,5-dimethyl-1,3-dioxole-2-one using carbon dioxide has the following problems: the method uses non-toxic, non-corrosive and inexpensive carbon dioxide as a raw material to prepare 4,5-dimethyl-1,3-dioxole-2-one, but the method lacks monitoring of the synthesis process and cannot determine the reliability of the yield. Summary of the invention

[0008] To this end, the present invention provides a method for preparing 3,4-dimethyl-1,2-cyclopentanedione, which is used to overcome the problem of low oxidation yield due to incomplete conversion of 3,4-dimethylcyclohexanol in the preparation process of 3,4-dimethyl-1,2-cyclopentanedione in the prior art.

[0009] To achieve the above object, the present invention provides a method for preparing 3,4-dimethyl-1,2-cyclopentanedione, comprising: Step S1, extracting each catalyst into a first reactor at a preset ratio and heating it to a first preset temperature, heating 3,4-dimethylcyclohexanol to a second preset temperature, maintaining the second preset temperature and dripping it into the first reactor at a preset speed, if the temperature in the first reactor is higher than the second preset temperature during the reaction, opening the refrigerant valve to cool the first reactor, and maintaining the second preset temperature for a preset time after the dripping is completed to generate an oxidation product, adipic acid, wherein each catalyst includes potassium permanganate, copper nitrate and ammonium metavanadate; Step S2, determining the content of the 3,4-dimethylcyclohexanol in the first reactor, determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content of the 3,4-dimethylcyclohexanol, and determining the reason why the oxidation process does not meet the standard based on the content difference, adjusting the corresponding parameters according to the determined reason, and determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard again based on the content of the 3,4-dimethylcyclohexanol in the next production cycle after the adjustment, and determining whether the generation process of the adipic acid meets the standard based on the oxidation process that meets the standard and the reactor residue of the first reactor; Step S3, adding methanol and adipic acid into the second reactor, stirring evenly, introducing concentrated sulfuric acid, stirring again and heating to a third preset temperature, refluxing at the third preset temperature for several hours and then cooling to below room temperature, introducing toluene into the second reactor, stirring for a preset number of times and then standing until the second reactor is separated into an aqueous layer and an organic layer, and introducing the organic layer solution into a metering tank after treatment, wherein the organic layer solution includes an esterification product; Step S4, adding toluene into the third reaction kettle in a vacuum state, adding the organic layer solution under stirring conditions, and maintaining the fourth preset temperature for several hours to generate a cyclization product; Step S5, extracting the cyclization product and water together into a fourth reaction kettle, dropping a sodium hydroxide solution after cooling, adding a sodium nitrite aqueous solution after the dropping is complete, heating, and keeping the temperature for several hours before extracting and concentrating. The solid obtained after concentration is the crude product 3,4-dimethyl-1,2-cyclopentanedione; Step S6, adding a crystallization solvent to the crude product for recrystallization to obtain the product 3,4-dimethyl-1,2-cyclopentanedione.

[0010] Further, in the step S2, the process of determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content of the 3,4-dimethylcyclohexanol includes: comparing the content with a preset content; Based on the comparison result that the content is greater than the preset content, it is determined that the oxidation process of the 3,4-dimethylcyclohexanol does not meet the standard.

[0011] Further, in step S2, the process of determining the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard based on the content difference includes: Determining, based on the comparison result that the content difference is less than the first preset difference, that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset speed does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the first preset difference and less than the second preset difference, determining that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the flow rate of the refrigerant does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the second preset difference, it is determined that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset time length does not meet the standard.

[0012] Furthermore, in step S2, based on the condition that the preset speed does not meet the standard, several adjustment methods are set for the preset speed according to the generation rate of the adipic acid, and the adjustment range of the preset speed by a single adjustment method is negatively correlated with the generation rate of the adipic acid.

[0013] Furthermore, in step S2, based on the condition that the flow rate of the refrigerant does not meet the standard, the temperature in the first reactor is periodically detected, and several adjustment methods are set for the flow rate based on the temperature, and the adjustment range of the flow rate in each adjustment method is positively correlated with the temperature.

[0014] Further, in step S2, based on the condition that the preset time length does not meet the standard, several adjustment methods are set for the preset time length according to the content difference percentage, and the adjustment range of each adjustment method for the preset time length is positively correlated with the content difference percentage.

[0015] Furthermore, in the step S2, for the production process of adipic acid that meets the standards in the next production cycle after adjustment, the process of determining whether the production process of adipic acid meets the standards according to the residue in the first reactor includes: comparing the kettle residue with a preset kettle residue; Based on the comparison result that the still residue is greater than the preset still residue, it is determined that the adipic acid production process does not meet the standard.

[0016] Further, in the step S2, under the condition that the adipic acid production process does not meet the standard, the kettle residual value is compared with a preset kettle residual value; Determining that the addition ratio of the copper nitrate does not meet the standard based on a comparison result that the kettle residual value is less than or equal to the preset kettle residual value; Based on the comparison result that the kettle residual value is greater than the preset kettle residual value, it is determined that the addition ratio of ammonium metavanadate does not meet the standard.

[0017] Furthermore, in the step S2, based on the condition that the addition ratio of the copper nitrate does not meet the standard, several adjustment methods are set for the addition ratio of the copper nitrate, and the adjustment range of the addition ratio of the copper nitrate in a single adjustment method is different.

[0018] Furthermore, in the step S2, based on the condition that the addition ratio of the ammonium metavanadate does not meet the standard, several adjustment methods are set for the addition ratio of the ammonium metavanadate, and each adjustment method has a different adjustment range for the addition ratio of the ammonium metavanadate.

[0019] Compared with the prior art, the beneficial effect of the present invention is that the present invention uses 3,4-dimethylcyclohexanol as a raw material, undergoes oxidation reaction, esterification reaction, cyclization reaction and oximation reaction, and finally generates 3,4-dimethyl-1,2-cyclopentanedione after recrystallization; the oxidation reaction is the first reaction process in the entire preparation process, and the oxidation yield of the raw material is directly related to the yield of the subsequent reaction. A high content of the raw material after the reaction indicates that the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard, and the oxidation yield is low. The reason for the low content is determined according to the content difference, and the parameters are adjusted in a targeted manner based on the determined reason. , thereby improving the oxidation yield of 3,4-dimethylcyclohexanol; for the oxidation process that meets the standards, determine whether the conversion process of adipic acid meets the standards based on the oxidation yield of 3,4-dimethylcyclohexanol. There are side reactions in the oxidation process of 3,4-dimethylcyclohexanol. More side reactions will lead to less production of adipic acid and low oxidation yield. The addition ratio of the catalyst is adjusted based on the kettle residue. Potassium permanganate, copper nitrate and ammonium metavanadate are used as catalysts to reduce the reaction activation energy, accelerate the reaction rate, and guide the reaction along a specific path, thereby improving the conversion rate and selectivity of the reaction, thereby improving the oxidation yield.

[0020] Furthermore, after the oxidation reaction is completed, the high content of 3,4-dimethylcyclohexanol in the first reactor indicates that the oxidation process does not meet the standards. Too fast an acceleration will cause the reaction to be too violent, releasing a large amount of heat to induce side reactions, and reduce the yield of the target product adipic acid. Too slow an acceleration will lead to an increase in side reactions and low reaction efficiency. Adjusting the flow rate of the freezing liquid is essentially to adjust the temperature of the reaction. The oxidation reaction is exothermic, and the freezing liquid needs to be introduced to cool down so that the reaction can be carried out at a suitable temperature. Too high a flow rate of the freezing liquid will cause the temperature of the reaction system to decrease, thereby slowing down the reaction rate and reducing the oxidation yield. Too low a flow rate of the freezing liquid will cause the temperature to be too high, resulting in the occurrence of side reactions, reducing the purity of the target product, thereby resulting in a low oxidation yield. The preset time is the preset reaction time. Too short a reaction time causes part of the 3,4-dimethylcyclohexanol to fail to be converted into adipic acid, directly resulting in a low oxidation yield. Too long a reaction time will cause side reactions to occur, thereby reducing the purity and yield of the product. The present invention improves the oxidation yield by performing targeted parameter adjustment by comparing the content difference.

[0021] Furthermore, the present invention determines whether the production process of adipic acid meets the standards through the residual content of the first reactor. More residual content means that there are more side reactions in the production process of adipic acid and more impurities are generated, resulting in low purity of the generated target product and thus low oxidation yield. Under the condition that the oxidation process meets the standards, more residual content means that there are more side reactions in the reaction process. The amount of catalyst added is adjusted to allow the reaction to proceed along a specific path, thereby improving the reaction conversion rate and the purity of the target product, and further improving the oxidation yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to an embodiment of the present invention; Figure 2 A flow chart for determining whether the oxidation process of 3,4-dimethylcyclohexanol meets the standard in an embodiment of the present invention; Figure 3 A flow chart for determining the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standards according to an embodiment of the present invention; Figure 4 The present invention is a flowchart for determining whether the adipic acid production process meets the standards according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0025] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0026] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] See also Figure 1-4 As shown, Figure 1 This is a flow chart of the method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to an embodiment of the present invention; Figure 2 A flow chart for determining whether the oxidation process of 3,4-dimethylcyclohexanol meets the standard in an embodiment of the present invention; Figure 3A flow chart for determining the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standards according to an embodiment of the present invention; Figure 4 The present invention is a flowchart for determining whether the adipic acid production process meets the standards according to an embodiment of the present invention.

[0028] The embodiment of the present invention provides a method for preparing 3,4-dimethyl-1,2-cyclopentanedione, comprising: Step S1, extracting each catalyst into a first reactor at a preset ratio and heating it to a first preset temperature, heating 3,4-dimethylcyclohexanol to a second preset temperature, maintaining the second preset temperature and dripping it into the first reactor at a preset speed, if the temperature in the first reactor is higher than the second preset temperature during the reaction, opening the refrigerant valve to cool it down, and maintaining the second preset temperature for a preset time after the dripping is completed to generate an oxidation product, adipic acid, wherein each catalyst includes potassium permanganate, copper nitrate and ammonium metavanadate; Step S2, after the preset time period ends, determining the content of the 3,4-dimethylcyclohexanol in the first reactor, determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content, determining the reason for non-compliance with the standard based on the content difference for the oxidation process that does not meet the standard, and adjusting parameters based on the determined reason, and determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard again based on the content in the next production cycle after the adjustment, and determining whether the generation process of adipic acid meets the standard based on the residue of the first reactor based on the oxidation process that meets the standard; Step S3, adding methanol and adipic acid into the second reactor, stirring evenly, introducing concentrated sulfuric acid, stirring again and heating to a third preset temperature, refluxing at the third preset temperature for several hours and then cooling to below room temperature, introducing toluene into the second reactor, stirring for a preset number of times and then standing until the second reactor is separated into an aqueous layer and an organic layer, and introducing the organic layer solution into a metering tank after treatment, wherein the organic layer solution includes an esterification product; Step S4, adding toluene into the third reaction kettle in a vacuum state, adding the organic layer solution under stirring conditions, and maintaining the fourth preset temperature for several hours to generate a cyclization product; Step S5, extracting the cyclization product and water together into a fourth reaction kettle, dropping a sodium hydroxide solution after cooling, adding a sodium nitrite aqueous solution after the dropping is complete, heating, and keeping the temperature for several hours before extracting and concentrating. The solid obtained after concentration is the crude product 3,4-dimethyl-1,2-cyclopentanedione; Step S6, adding a crystallization solvent to the crude product for recrystallization to obtain the product 3,4-dimethyl-1,2-cyclopentanedione.

[0029] Specifically, the preset ratio is a mass ratio, and the value range is set to: potassium permanganate: copper nitrate: ammonium metavanadate = [280-320:0.8-1.2:0.8-1.2]. In the embodiment of the present invention, potassium permanganate: copper nitrate: ammonium metavanadate = 300:1:1 is preferred.

[0030] Specifically, the value range of the first preset temperature is set to [30° C., 40° C.], and 35° C. is preferred in the embodiment of the present invention.

[0031] Specifically, nitrogen dioxide gas is produced during the oxidation reaction of 3,4-dimethylcyclohexanol, which can be recycled for other purposes, reducing environmental pressure.

[0032] Specifically, the value range of the second preset temperature is set to [40° C., 45° C.], and 42° C. is preferred in the embodiment of the present invention.

[0033] Specifically, the value range of the preset speed is set to [70kg / h, 80kg / h], and 75kg / h is preferred in the embodiment of the present invention.

[0034] Specifically, the value range of the preset duration is set to [4h, 6h], and 5h is preferred in the embodiment of the present invention.

[0035] Specifically, the determination of the content of 3,4-dimethylcyclohexanol includes: taking 50 ml of sample from the sampling port of the first reaction kettle, extracting and neutralizing with an equal amount of toluene, and then determining by gas chromatography internal standard method.

[0036] Specifically, the value range of the third preset temperature is set to [60° C., 75° C.], and 70° C. is preferred in the embodiment of the present invention.

[0037] Specifically, the value range of several hours in the several hours of reflux at the third preset temperature is set to [2h, 5h], and 3h is preferred in the embodiment of the present invention. The third preset temperature is maintained during the reflux process.

[0038] Specifically, the temperature range of the room temperature is generally [20°C, 25°C], and the room temperature in the embodiment of the present invention is preferably 20°C.

[0039] Specifically, the value range of the preset number of times is set to [5 times, 8 times], and 7 times is preferred in the embodiment of the present invention.

[0040] Specifically, after standing and stratifying, the water layer needs to be extracted with toluene once, and then stood and stratified again into the water layer and the organic layer. The organic layers are combined and introduced into the metering tank together; the treatment of the organic layer solution is to use a saturated sodium bicarbonate solution to wash to pH = 7 to neutralize the residual sulfuric acid in the system and reduce the kettle residue.

[0041] Specifically, the value range of the fourth preset temperature is set to [30° C., 45° C.], and 40° C. is preferred in the embodiment of the present invention; the several hours of maintaining the fourth preset temperature of 40° C. for several hours is 2 hours in the embodiment of the present invention.

[0042] Specifically, the extraction is carried out using methyl tert-butyl ether; the recrystallization process is: the crude product is dissolved in ethanol, the temperature is raised to 50°C, and the temperature is kept for 1 hour. After the solid is completely dissolved, a freezing liquid is passed for cooling and slow stirring. When the temperature drops to -10°C, no solid precipitates. After centrifugation, white crystals are obtained. After drying with a rotary drum dryer and passing the drying test, the crystals are stored in a vacuum.

[0043] Specifically, the first reactor, the second reactor and the third reactor are only used to distinguish the reactors used in the reaction process and have no specific functions.

[0044] Specifically, the process of determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content includes: comparing the content with a preset content; Determining that the oxidation process of the 3,4-dimethylcyclohexanol does not meet the standard based on the comparison result that the content is greater than the preset content; Based on the comparison result that the content is less than or equal to the preset content, it is determined that the oxidation process of the 3,4-dimethylcyclohexanol meets the standard.

[0045] Specifically, the value range of the preset content is set to [0.7%, 0.8%], and 0.75% is preferred in the embodiment of the present invention.

[0046] Specifically, the process of determining the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard based on the content difference includes: Determining, based on the comparison result that the content difference is less than the first preset difference, that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset speed does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the first preset difference and less than the second preset difference, determining that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the flow rate of the refrigerant does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the second preset difference, it is determined that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset time length does not meet the standard.

[0047] Specifically, the value range of the first preset difference is set to [0.05%, 0.15%], and 0.1% is preferably used in the embodiment of the present invention; the value range of the second preset difference is set to [0.16%, 0.2%], and 0.17% is preferably used in the embodiment of the present invention.

[0048] Specifically, based on the condition that the preset speed does not meet the standard, several adjustment methods are set for the preset speed according to the generation rate of the adipic acid, and the adjustment range of the preset speed in each adjustment method is negatively correlated with the generation rate of the adipic acid.

[0049] It can be understood that the adjustment range of each adjustment method for the preset speed is negatively correlated with the generation rate of adipic acid. The smaller the generation rate of adipic acid, the larger the adjustment range of each adjustment method for the preset speed.

[0050] Specifically, based on the condition that the flow rate of the refrigerant does not meet the standard, the temperature in the first reactor is periodically detected, and several adjustment methods are set for the flow rate based on the temperature, and the adjustment range of the flow rate in each adjustment method is positively correlated with the temperature.

[0051] Specifically, the period for periodically detecting the temperature in the first reaction kettle is 30 minutes.

[0052] It can be understood that the adjustment range of the flow rate by each adjustment method is positively correlated with the temperature. The higher the temperature, the greater the increase in the flow rate by each adjustment method.

[0053] Specifically, based on the condition that the preset time length does not meet the standard, several adjustment methods are set for the preset time length according to the content difference percentage, and the adjustment range of each adjustment method for the preset time length is positively correlated with the content difference percentage.

[0054] It can be understood that the adjustment range of each adjustment method for the preset time length is positively correlated with the content difference percentage. The larger the content difference is, the greater the increase in the preset time length by each adjustment method.

[0055] Specifically, for the production process of adipic acid that meets the standards in the next production cycle after adjustment, the process of determining whether the production process of adipic acid meets the standards according to the residue in the first reactor includes: comparing the kettle residue with a preset kettle residue; Determining that the adipic acid production process does not meet the standard based on the comparison result that the still residue is greater than the preset still residue; Based on the comparison result that the still residue is less than or equal to the preset still residue, it is determined that the adipic acid production process does not meet the standard.

[0056] Specifically, the preset range of the kettle residue is set to [2%, 3%], and 2.5% is preferred in the embodiment of the present invention.

[0057] Specifically, under the condition that the adipic acid production process does not meet the standard, the kettle residual value is compared with a preset kettle residual value; Determining that the addition ratio of the copper nitrate does not meet the standard based on a comparison result that the kettle residual value is less than or equal to the preset kettle residual value; Based on the comparison result that the kettle residual value is greater than the preset kettle residual value, it is determined that the addition ratio of ammonium metavanadate does not meet the standard.

[0058] Specifically, the preset range of the kettle residual value is set to [0.5%, 2%], and 1.5% is preferred in the embodiment of the present invention.

[0059] Specifically, based on the condition that the addition ratio of the copper nitrate does not meet the standard, several adjustment methods are set for the addition ratio of the copper nitrate, and each adjustment method has a different adjustment range for the addition ratio of the copper nitrate.

[0060] Specifically, the preset kettle residual value is subtracted from the kettle residual value to obtain a first difference percentage, and the first difference percentage is compared with the first preset difference percentage. If the first difference percentage is greater than the first preset difference percentage, the addition ratio of copper nitrate is adjusted using a first ratio adjustment coefficient; If the first difference percentage is less than or equal to the first preset difference percentage, the second proportion adjustment coefficient is used to adjust the addition proportion of copper nitrate.

[0061] Specifically, the value range of the first preset difference percentage is set to [5%, 15%], and 10% is preferred in the embodiment of the present invention.

[0062] Specifically, the value range of the first proportional adjustment coefficient is set to [1.02, 1.039], and 1.03 is preferably selected in the embodiment of the present invention; the value range of the second proportional adjustment coefficient is set to [1.04, 1.059], and 1.05 is preferably selected in the embodiment of the present invention.

[0063] Specifically, based on the condition that the addition ratio of ammonium metavanadate does not meet the standard, several adjustment methods are set for the addition ratio of ammonium metavanadate, and each adjustment method has a different adjustment range for the addition ratio of ammonium metavanadate.

[0064] Specifically, the kettle residual value is subtracted from the preset kettle residual value to obtain a second difference percentage, and the second difference percentage is compared with the second preset difference percentage. If the second difference percentage is greater than the second preset difference percentage, the addition ratio of ammonium metavanadate is adjusted using a third ratio adjustment coefficient; If the second difference percentage is less than or equal to the second preset difference percentage, the fourth proportion adjustment coefficient is used to adjust the addition proportion of ammonium metavanadate.

[0065] Specifically, the value range of the second preset difference percentage is set to [16%, 20%], and 18% is preferred in the embodiment of the present invention.

[0066] Specifically, the value range of the third proportional adjustment coefficient is set to [1.01, 1.019], and 1.015 is preferably used in the embodiment of the present invention; the value range of the second proportional adjustment coefficient is set to [1.02, 1.029], and 1.025 is preferably used in the embodiment of the present invention.

[0067] Example

[0068] 1. Oxidation reaction Start the vacuum pump, open the vacuum valve of the receiving tank, close the vent valve, pump 450Kg of potassium permanganate from the bottom of the first reactor, close the bottom valve, remove the vacuum of the reactor, start stirring, add 1.5Kg of copper nitrate and 1.5Kg of ammonium metavanadate; form a vacuum in the metering tank, pump 300Kg of 3,4-dimethylcyclohexanol into the metering tank, remove the vacuum, close the vacuum pump, open the jacket steam valve to heat the furnace, and at the same time, turn on the induced draft fan and alkali liquid circulation pump for recovering nitrogen dioxide. When the kettle temperature reaches the first preset temperature of 35℃, close the steam valve. Open the metering tank drip valve, interlock and put it into use, SIS feed cut-off valve HS-201 automatically, DCS feed regulating valve TCV-201 automatically, and set the adjustment value to 50%. Start to add 3,4-dimethylcyclohexanol dropwise, and control the dropping temperature at 42°C (this step is an exothermic reaction. When the reaction temperature rises to 42°C, open the freezing liquid valve of the oxirane jacket and cool it down). Control the dropping for about 4 hours. After the dropping is completed, keep the temperature at 42°C for reaction. Keep the reaction warm for 5 hours to generate the oxidation product adipic acid.

[0069] After the insulation reaction is completed, 50 ml of sample is taken from the sampling port, extracted and neutralized with an equal amount of toluene, and the content of 3,4-dimethylcyclohexanol is determined by gas chromatography internal standard method. When the content is less than or equal to 0.75%, it means that the oxidation process of 3,4-dimethylcyclohexanol meets the standard. When the content is greater than 0.75%, it means that the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard. The content is subtracted from 0.75% to obtain the content difference. For example, if the content is 0.85%, the content difference is 0.1%, which is equal to the first preset difference. It means that the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard because the flow rate of the refrigerant does not meet the standard. When adjusting the flow rate of the refrigerant, it is necessary to periodically detect the temperature in the first reactor. The detection cycle is 5 minutes. The temperature detection result is subtracted from the second preset temperature of 42°C to obtain the temperature difference. The larger the temperature difference, the greater the increase in the flow rate of the refrigerant. After the temperature in the first reactor drops below 42°C, the flow rate increase is immediately stopped.

[0070] 2. Esterification reaction Open the vacuum valve of the receiving tank, close the drain valve of the 2000L second reactor containing crude adipic acid, pump 990Kg of methanol from the bottom of the reactor, start stirring to dissolve it, pass water to cool it down slightly, and then pump in 175Kg of concentrated sulfuric acid; close the vacuum valve of the receiving tank, open the drain valve, start stirring, open the jacket steam valve to raise the temperature of the reactor, maintain the internal temperature at 70°C, start timing from the start of reflux, and reflux and keep warm for 3 hours; open the receiving tank, continue to heat to 100°C to recover methanol, pass cooling water to cool down, when the internal temperature reaches 20°C below room temperature, introduce 450kg of toluene into the reactor, stir 7 times, and stand for stratification; the water layer is extracted once with 270kg of toluene, stirred for 30 minutes, and stood for 30 minutes. The organic layers are combined and washed with saturated sodium bicarbonate solution until pH=7. The esterification product 2,3-dimethyladipate is present in the organic layer.

[0071] 3. Cyclization reaction The third reactor was vacuumed and 1200L toluene was pumped into it. The vacuum was removed, and the manhole cover of the reactor was opened. Under vacuum conditions, 100Kg of sodium hydroxide was added while stirring. The vacuum was removed, and the manhole cover was opened. The metering tank was vacuumed and 338Kg of dimethyl 2,3-dimethyladipate was pumped into it. The vacuum was removed, and under stirring, dimethyl adipate was quickly added. The reaction was slightly exothermic. The reaction vacuum was adjusted to -0.08MPa, and methanol was distilled out. The reaction temperature was gradually increased to continuously distill out methanol and toluene solutions. The distillation rate was controlled at 50-60L / 1h. The reactor temperature was maintained at 40°C, and the distillation reaction was maintained for 2 hours. About 300L of toluene and methanol were distilled out.

[0072] 4. Oximation reaction Start the vacuum pump, open the vacuum valve of the receiving tank, close the drain valve, pump 113Kg of the cyclization product and 200Kg of water into the reactor, close the vacuum valve, and drain the reactor. Make the metering tank vacuum, and draw 350Kg of water + 30Kg of sodium hydroxide solution in several times. Close the vacuum valve and open the drain. Pass the freezing liquid to cool down, and start dripping the sodium hydroxide solution when the temperature drops below 15℃. Control the temperature between 10-15℃ and drip it in about 50 minutes. After dripping, quickly add 46Kg of sodium nitrite and 180Kg of aqueous solution. Remove the freezing liquid in the jacket of the reactor, then open the steam valve and gradually heat it to 28-32℃, and keep it warm for 18 hours. After the reaction is completed, add 350L of hydrochloric acid at 0℃, drip it for 1.5h, react for 1h, add methyl tert-butyl ether to extract, concentrate, and obtain the crude product, which is 3,4-dimethyl-1,2-cyclopentanedione.

[0073] 5. Crystallization The crude product was dissolved in ethanol, heated to 50°C, and kept warm for 1 hour. After the crude 3,4-dimethyl-1,2-cyclopentanedione was completely dissolved, a freezing liquid was passed in for cooling, and the mixture was stirred slowly. When the temperature dropped to -10°C, no solid was precipitated. After centrifugation, white crystals were obtained. The product was dried with a drum dryer and stored in a vacuum.

[0074] The oxidation yield of 3,4-dimethyl-1,2-cyclopentanedione prepared through the above steps is stable at [91%, 92%]. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione using a traditional process is to use nitric acid as a catalyst, and the oxidation process is not monitored. The maximum oxidation yield is only 86%, and nitric acid will react during the reaction to produce nitrogen dioxide as a by-product. Compared with the traditional process, the method provided in the embodiment of the present invention not only has no side reaction products but also has a significantly improved oxidation yield.

[0075] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing 3,4-dimethyl-1,2-cyclopentanedione, characterized in that: include: Step S1, extracting each catalyst into a first reactor at a preset ratio and heating it to a first preset temperature, heating 3,4-dimethylcyclohexanol to a second preset temperature, maintaining the second preset temperature and dripping it into the first reactor at a preset speed, if the temperature in the first reactor is higher than the second preset temperature during the reaction, opening the refrigerant valve to cool the first reactor, and maintaining the second preset temperature for a preset time after the dripping is completed to generate an oxidation product, adipic acid, wherein each catalyst includes potassium permanganate, copper nitrate and ammonium metavanadate; Step S2, determining the content of the 3,4-dimethylcyclohexanol in the first reactor, determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content of the 3,4-dimethylcyclohexanol, and determining the reason why the oxidation process does not meet the standard based on the content difference, adjusting the corresponding parameters according to the determined reason, and determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard again based on the content of the 3,4-dimethylcyclohexanol in the next production cycle after the adjustment, and determining whether the generation process of the adipic acid meets the standard based on the oxidation process that meets the standard and the reactor residue of the first reactor; Step S3, adding methanol and adipic acid into the second reactor, stirring evenly, introducing concentrated sulfuric acid, stirring again and heating to a third preset temperature, refluxing at the third preset temperature for several hours and then cooling to below room temperature, introducing toluene into the second reactor, stirring for a preset number of times and then standing until the second reactor is separated into an aqueous layer and an organic layer, and introducing the organic layer solution into a metering tank after treatment, wherein the organic layer solution includes an esterification product; Step S4, adding toluene into a third reaction kettle in a vacuum state, adding the organic layer solution under stirring conditions, and maintaining the fourth preset temperature for several hours to generate a cyclization product; Step S5, extracting the cyclization product and water together into a fourth reaction kettle, dropping a sodium hydroxide solution after cooling, adding a sodium nitrite aqueous solution after the dropping is complete, heating, and keeping the temperature for several hours before extracting and concentrating. The solid obtained after concentration is the crude product 3,4-dimethyl-1,2-cyclopentanedione; Step S6, adding a crystallization solvent to the crude product for recrystallization to obtain the product 3,4-dimethyl-1,2-cyclopentanedione; Wherein, the preset ratio is a mass ratio, which is: potassium permanganate: copper nitrate: ammonium metavanadate = 280-320: 0.8-1.2: 0.8-1.2; The value range of the first preset temperature is [30°C, 40°C], the value range of the second preset temperature is [40°C, 45°C], the value range of the preset speed is [70kg / h, 80kg / h], and the value range of the preset time is [4h, 6h].

2. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 1, characterized in that: In step S2, the process of determining whether the oxidation process of the 3,4-dimethylcyclohexanol meets the standard based on the content of the 3,4-dimethylcyclohexanol includes: comparing the content with a preset content; Determining that the oxidation process of the 3,4-dimethylcyclohexanol does not meet the standard based on the comparison result that the content is greater than the preset content; Among them, the value range of the preset content is [0.7%, 0.8%].

3. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 2, characterized in that: In step S2, the process of determining the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard based on the content difference includes: Determining, based on the comparison result that the content difference is less than the first preset difference, that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset speed does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the first preset difference and less than the second preset difference, determining that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the flow rate of the refrigerant does not meet the standard; Based on the comparison result that the content difference is greater than or equal to the second preset difference, it is determined that the reason why the oxidation process of 3,4-dimethylcyclohexanol does not meet the standard is that the preset time length does not meet the standard.

4. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 3, characterized in that: In step S2, based on the condition that the preset speed does not meet the standard, several adjustment methods are set for the preset speed according to the generation rate of adipic acid, and the adjustment range of the preset speed by a single adjustment method is negatively correlated with the generation rate of adipic acid.

5. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 3, characterized in that: In step S2, based on the condition that the flow rate of the refrigerant does not meet the standard, the temperature in the first reactor is periodically detected, and several adjustment methods are set for the flow rate based on the temperature, and the adjustment range of the flow rate in each adjustment method is positively correlated with the temperature.

6. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 3, characterized in that: In step S2, based on the condition that the preset time length does not meet the standard, several adjustment methods are set for the preset time length according to the content difference percentage, and the adjustment range of each adjustment method for the preset time length is positively correlated with the content difference percentage.

7. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 6, characterized in that: In step S2, for the production process of adipic acid in the next production cycle after adjustment, the process of determining whether the production process of adipic acid meets the standard according to the residue in the first reactor comprises: comparing the kettle residue with a preset kettle residue; Based on the comparison result that the still residue is greater than the preset still residue, it is determined that the adipic acid production process does not meet the standard.

8. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 7, characterized in that: In the step S2, under the condition that the adipic acid production process does not meet the standard, the kettle residual value is compared with a preset kettle residual value; Determining that the addition ratio of the copper nitrate does not meet the standard based on a comparison result that the kettle residual value is less than or equal to the preset kettle residual value; Based on the comparison result that the kettle residual value is greater than the preset kettle residual value, it is determined that the addition ratio of ammonium metavanadate does not meet the standard.

9. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 8, characterized in that: In the step S2, based on the condition that the addition ratio of the copper nitrate does not meet the standard, several adjustment methods are set for the addition ratio of the copper nitrate, and the adjustment range of the addition ratio of the copper nitrate in a single adjustment method is different.

10. The method for preparing 3,4-dimethyl-1,2-cyclopentanedione according to claim 8, characterized in that: In the step S2, based on the condition that the addition ratio of the ammonium metavanadate does not meet the standard, several adjustment methods are set for the addition ratio of the ammonium metavanadate, and each adjustment method has a different adjustment range for the addition ratio of the ammonium metavanadate.

Images