Production system and method for generating carboxylic acid methyl ester through reaction of carboxylic acid and methanol

Abstract

The invention discloses a production system and method for generating carboxylic acid methyl ester through reaction of carboxylic acid and methanol. The system comprises a catalyst; the catalyst is a mixture of benzenesulfonic acid, tetrabutyl titanate and trimethyl phosphate in any mass ratio; in the system, the molar ratio of the methanol to the carboxylic acid is (5: 1)-(100: 1). Through two stages of esterification reactors connected in series, the reaction process can be effectively controlled, the conversion per pass can be improved, the content of intermediate products such as monoester can be reduced, and the reaction products can be separated more easily. The compound catalytic system applied in the invention not only can reduce the corrosion to equipment, but also enables the industrial implementation to have better operability; the investment can be reduced, the operation cost can be reduced, and the economic benefit can be maximized. Under the set process conditions, the yield of the carboxylic acid methyl ester is not lower than 95%.

Description

Technical Field

[0001] The invention relates to a production system and method for generating methyl carboxylate by reacting carboxylic acid with methanol. Background Art

[0002] Carboxylic acid esters are a very important class of chemical products, such as dimethyl naphthalate (NDC), which is a key monomer for the production of polyethylene naphthalate (PEN). The end product PEN is widely used in many fields such as membrane materials, flexible printed circuit boards (FPC), fuel cell seals, electrical heat-resistant insulation, speaker membranes, food-grade pharmaceutical packaging, and aerospace materials. Dimethyl terephthalate (DMT) can be hydrogenated to produce 1,4-cyclohexanedimethanol (CHDM), which is an important monomer for the synthesis of a variety of high-performance polyester materials, such as polyethylene terephthalate (PCT), polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG), and copolyester PCTA. At present, concentrated sulfuric acid and dibutyltin oxide are generally used as catalysts in the industrial production of carboxylic acid esters. The desired carboxylic acid esters are obtained by esterification reaction between carboxylic acid and alcohol through the action of the catalyst. Summary of the invention

[0003] In order to increase the options for the process routes for producing carboxylic acid esters, the embodiments of the present invention provide a system and method for producing methyl carboxylate using a synergistic catalyst and a stepwise esterification technology, thereby obtaining a process route for producing carboxylic acid esters with better overall economic benefits.

[0004] As one aspect of the present invention, it relates to a production system for generating methyl carboxylate by reacting carboxylic acid with methanol, wherein the system comprises a catalyst, and the catalyst is a mixture of benzenesulfonic acid, tetrabutyl titanate and trimethyl phosphate in any mass ratio;

[0005] In the system, the molar ratio of the methanol to the carboxylic acid is 5:1 to 100:1.

[0006] In one or some possible embodiments, the catalyst is a mixture of tetrabutyl titanate and trimethyl phosphate in any mass ratio.

[0007] In one or some possible embodiments, the catalyst is selected from a mixture of tetrabutyl titanate and trimethyl phosphate in a mass ratio of 10:1 to 3:1.

[0008] In one or some possible embodiments, the amount of the catalyst used is 1‰ to 8% of the amount of the carboxylic acid used.

[0009] In one or some possible embodiments, in the system, the molar ratio of the methanol to the carboxylic acid is 5:1 to 100:1, the catalyst is selected from a mixture of tetrabutyl titanate and trimethyl phosphate in a mass ratio of 10:1 to 3:1, and the amount of the catalyst is 2 to 3% of the amount of the carboxylic acid.

[0010] As another aspect of the present invention, it relates to a production method for generating carboxylic acid methyl ester by reacting carboxylic acid with methanol. The method uses the above production system and comprises two-stage esterification.

[0011] In one or some possible embodiments, the two-stage esterification uses one or two esterification reactors connected in series.

[0012] In one or some possible embodiments, the first stage esterification reaction temperature is 170-280° C., and the reaction time is 1-4 hours; the second stage esterification reaction temperature is 150-210° C., and the reaction time is 1-4 hours.

[0013] In one or some possible embodiments, the first stage esterification reaction temperature is 180-210° C., and the reaction time is 2 to 3 hours; the second stage esterification reaction temperature is 195 to 205° C., and the reaction time is 2 to 3 hours.

[0014] As another aspect of the present invention, it relates to an application of the above production system and method in the production of dimethyl 2,6-naphthalene dicarboxylate and dimethyl terephthalate.

[0015] The beneficial effects of the above technical solution provided by the embodiment of the present application include at least:

[0016] (1) The present invention uses two-stage esterification reactors in series to effectively control the reaction process, improve the single-pass conversion rate, reduce the content of intermediate products such as monoesters, and make the reaction products easier to separate.

[0017] (2) The composite catalytic system used in the present invention not only reduces the corrosion to the equipment, making industrial implementation more operable, but also reduces investment and operating costs, thereby maximizing economic benefits.

[0018] (3) Under the process conditions set by the present invention, the yield of methyl carboxylate is not less than 95%.

[0019] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 The process flow chart of producing methyl carboxylate of the present invention is as follows:

[0022] In the figure, 101 is a first esterification reactor; 102 is a second esterification reactor; a is a carboxylic acid; b is a catalyst; c is methanol; d is a first esterification slurry; and e is a second esterification slurry. DETAILED DESCRIPTION

[0023] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0024] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] In the description of the present invention, it should be noted that the terms "include", "including", "have", "contain" and the like are open terms, meaning including but not limited to.

[0027] The present invention is further described below in conjunction with specific examples, and the protection scope of the present invention is not limited by the following examples. The sources of materials mainly involved in the examples are all conventional commercial products.

[0028] In the prior art, when dibutyltin oxide is used as a catalyst, dibutyltin oxide is easily converted into tributyltin oxide, a highly toxic substance, during the production of carboxylic acid esters; in addition, the esterification temperature of high-temperature production usually reaches 280°C and the pressure reaches 10MPaG, and the production conditions are harsh.

[0029] U.S. Patent US005262560A invented a method for producing dimethyl naphthalene dicarboxylate (NDC) by refluxing products and intermediates to an esterification reactor, thereby reducing the mass ratio of methanol to naphthalene dicarboxylic acid (NDA), but the method has a low single-pass esterification rate; in another method for producing dimethyl naphthalene dicarboxylate invented by U.S. Patent US005095135A, acid is used as a catalyst in the esterification process, which will cause serious corrosion of the equipment and make waste liquid treatment difficult.

[0030] In summary, given that the prior art does not meet the inventor's expectations, the inventor made the present invention through further research and development.

[0031] Combination Figure 1 The process flow chart shown in the figure specifically illustrates the process flow of producing methyl carboxylate of the present invention:

[0032] Carboxylic acid a, methanol c and catalyst b are added into the first esterification reactor 101, and under the first stage esterification conditions, a first esterification slurry d is obtained; the first esterification slurry d is sent to the second esterification reactor 102, and under the second stage esterification conditions, the esterification reaction is continued, and a second esterification slurry e is obtained from the bottom discharge port of the second esterification reactor 102, which is a crude product of methyl carboxylate.

[0033] In the embodiment of the present invention, the inventors, in order to improve the purity of the crude methyl carboxylate product, perform distillation, recrystallization, filtration, washing and drying on the crude methyl carboxylate product in the subsequent treatment process, thereby obtaining a methyl carboxylate product with higher purity. The following embodiment only explains the esterification process, and those skilled in the art may assume that after the esterification process is completed, the product will be sequentially subjected to the above-mentioned treatments such as distillation, recrystallization, filtration, washing and drying.

[0034] In order to improve the economic efficiency of the production process of methyl carboxylate, the inventors have designed a variety of catalyst systems. The following are Examples 1 to 6 of the catalyst system of the present invention.

[0035] Taking the production of dimethyl 2,6-naphthalene dicarboxylate as an example, the specific steps include:

[0036] (1) adding reactants and catalyst b to the first esterification reactor 101, and obtaining a first esterification slurry d under the first stage esterification conditions; wherein the temperature of the first esterification reactor 101 is set to 210° C., the material residence time is 3 h, and the reactants include methanol c and naphthalene dicarboxylic acid (carboxylic acid a) in a molar ratio of 10:1;

[0037] (2) The first esterification slurry d is fed into the second esterification reactor 102. Under the second stage esterification conditions, a second esterification slurry e, i.e., a crude product of dimethyl 2,6-naphthalene dicarboxylate, is obtained from the bottom discharge port of the second esterification reactor 102. The temperature in the second esterification reactor 102 is set to 200° C., and the material residence time is set to 2 h.

[0038] In order to clearly and intuitively understand the effects of different catalyst systems on the catalytic production of dimethyl 2,6-naphthalenedicarboxylate, the amount of catalyst b was controlled to be 1.5% of the mass of naphthalenedicarboxylic acid. The catalyst systems used in the examples and the yields of carboxylic acid esters are recorded in the following Table 1.

[0039] Table 1 Catalyst systems used in Examples 1 to 6 and calculation results

[0040]

[0041]

[0042] Combined with the data results in Table 1, it can be seen that the catalytic effect of the composite catalyst is better than that of a single catalyst. In particular, when tetrabutyl titanate and trimethyl phosphate are composited as catalysts to catalyze the production of methyl carboxylate, the best catalytic effect can be achieved, making the yield of dimethyl 2,6-naphthalene dicarboxylate exceed 93%.

[0043] In order to further improve the economic benefits of producing dimethyl 2,6-naphthalene dicarboxylate, the inventors took Example 5 as an example and designed multiple groups of mass ratios of tetrabutyl titanate and trimethyl phosphate to obtain the following Examples 7 to 12. The relevant parameters and calculation results of Examples 7 to 12 are recorded in Table 2 below.

[0044] Table 2 Catalyst mass ratio and calculation results of Examples 7 to 12

[0045]

[0046] Combined with the calculation results in Table 2, it can be seen that when the mass ratio of tetrabutyl titanate and trimethyl phosphate is controlled at 10:1 to 3:1, the yield of dimethyl 2,6-naphthalene dicarboxylate is not less than 94.0%. Based on this, the inventor predicts that in the process of producing methyl carboxylate, when the catalyst is a composite of tetrabutyl titanate and trimethyl phosphate, and the mass ratio of tetrabutyl titanate and trimethyl phosphate is controlled at 10:1 to 3:1, the process route can achieve better economic benefits.

[0047] The inventors took Example 9 as an example, knowing the mass of the carboxylic acid, and finally determined the best process selection by adjusting the amount of catalyst b, and made the following Examples 13 to 17. The relevant parameters and calculation results of Examples 13 to 17 are recorded in Table 3 below.

[0048] Table 3 Catalyst mass ratio and calculation results of Examples 13 to 17

[0049] Catalyst dosage Yield of dimethyl 2,6-naphthalene dicarboxylate / % Embodiment 13 1wt‰ 87.3 Embodiment 14 2wt% 94.1 Embodiment 15 3wt% 95.3 Example 16 5wt% 95.5 Embodiment 17 8wt% 95.6

[0050] Combined with the calculation results in Table 3, it can be seen that when the amount of the catalyst is greater than 2% of the mass of the carboxylic acid, the yield of dimethyl 2,6-naphthalene dicarboxylate is not less than 94%; when the amount of the catalyst is greater than 3% of the mass of the carboxylic acid, the yield does not increase significantly when the amount of the catalyst is increased.

[0051] In summary, the inventors predict that in the process of producing methyl carboxylate, when catalyst b is selected from tetrabutyl titanate and trimethyl phosphate with a compound mass ratio of 10:1 to 3:1, and the amount of catalyst b is 2 to 3% of the mass of the carboxylic acid, the process route can achieve better economic benefits.

[0052] The inventor selected tetrabutyl titanate and trimethyl phosphate in a mass ratio of 5:1, and limited the amount of the catalyst to 3% of the mass of the carboxylic acid, and used the method for producing carboxylic acid esters of the present invention to produce dimethyl terephthalate, which is recorded as Example 18, and specifically includes the following steps:

[0053] (1) adding reactants and catalyst b to a first esterification reactor 101 to obtain a first esterification slurry d; wherein the temperature of the first esterification reactor 101 is set to 180° C., the material residence time is 2 h, and the reactants include methanol c and terephthalic acid (carboxylic acid a) in a molar ratio of 10:1;

[0054] (2) The first esterification slurry d is fed into the second esterification reactor 102. The temperature in the second esterification reactor 102 is set to 200°C and the material residence time is 3 hours. The second esterification slurry e, i.e., dimethyl terephthalate, is obtained from the bottom discharge port of the second esterification reactor 102.

[0055] Likewise, dimethyl terephthalate was produced using the above catalyst system, and the above step (2) was omitted as a comparative example of the present invention.

[0056] The final yield of dimethyl terephthalate when the catalyst system of the present invention is applied to the process route of the present invention and the process route used in the comparative example is calculated, and the calculation results are recorded in the following Table 4.

[0057] Table 4 Data calculation results

[0058] Yield of dimethyl terephthalate / % Embodiment 18 >95％ Comparative Example 1 ≤90％

[0059] It can be seen from the data results in Table 4 that the two-stage esterification process route of the present invention can increase the yield of dimethyl terephthalate by at least 5 percentage points. Therefore, the inventors believe that: through two-stage esterification, the reaction process can be controlled, the single-pass conversion rate can be increased, the content of intermediate products such as monoesters can be reduced, and the reaction products can be separated more easily; in addition, the new catalytic system also reduces corrosion to equipment, and industrial implementation is more operable, reducing investment and operating costs.

[0060] In summary, the present invention can effectively control the reaction process, improve the single-pass conversion rate, reduce the content of intermediate products such as monoesters, and make the reaction products easier to separate through the two-stage esterification reaction; at the same time, compounding the catalyst system of the present invention not only reduces the corrosion of equipment, but also makes industrial implementation more operable; it can also reduce investment, reduce operating costs, and achieve maximum economic benefits.

[0061] Although the description of the present invention has been quite detailed and has been described in particular with respect to several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, so as to effectively cover the intended scope of the present invention. In addition, the present invention is described above with the embodiments foreseeable by the inventors, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that are not currently foreseen may still represent equivalent changes of the present invention.

[0062] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0063] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A production system for generating methyl carboxylate by reacting carboxylic acid with methanol, characterized in that: The system comprises a catalyst; the catalyst is a mixture of benzenesulfonic acid, tetrabutyl titanate and trimethyl phosphate in any mass ratio; In the system, the molar ratio of the methanol to the carboxylic acid is 5:1 to 100:

1.

2. The production system of a carboxylic acid and methanol to generate methyl carboxylate according to claim 1, characterized in that: The catalyst is a mixture of tetrabutyl titanate and trimethyl phosphate in any mass ratio.

3. The production system of a carboxylic acid and methanol to generate methyl carboxylate according to claim 2, characterized in that: The catalyst is selected from a mixture of tetrabutyl titanate and trimethyl phosphate in a mass ratio of 10:1 to 3:

1.

4. A production system for producing methyl carboxylate by reacting carboxylic acid with methanol according to any one of claims 1 to 3, characterized in that: The amount of the catalyst used is 1‰ to 8% of the amount of the carboxylic acid used.

5. The production system of producing methyl carboxylate by reacting carboxylic acid with methanol according to claim 4, characterized in that: In the system, the molar ratio of the methanol to the carboxylic acid is 5:1 to 100:1, the catalyst is selected from a mixture of tetrabutyl titanate and trimethyl phosphate in a mass ratio of 10:1 to 3:1, and the amount of the catalyst is 2 to 3% of the amount of the carboxylic acid.

6. A method for producing methyl carboxylate by reacting carboxylic acid with methanol, characterized in that: The method uses the production system according to any one of claims 1 to 5 to produce methyl carboxylate, and the method comprises two-stage esterification.

7. The method for producing methyl carboxylate by reacting carboxylic acid with methanol according to claim 6, characterized in that: The two-stage esterification adopts one or two esterification reactors connected in series.

8. The method for producing methyl carboxylate by reacting carboxylic acid with methanol according to claim 7, characterized in that: The first stage esterification reaction temperature is 170-280° C., and the reaction time is 1-4 hours; the second stage esterification reaction temperature is 150-210° C., and the reaction time is 1-4 hours.

9. The method for producing methyl carboxylate by reacting carboxylic acid with methanol according to claim 8, characterized in that: The first stage esterification reaction temperature is 180-210° C., and the reaction time is 2 to 3 hours; the second stage esterification reaction temperature is 195 to 205° C., and the reaction time is 2 to 3 hours.

10. Use of the production method according to any one of claims 6 to 9 in the production of dimethyl 2,6-naphthalene dicarboxylate and dimethyl terephthalate.

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