A process for the preparation of diphenyl carbonate and the resulting diphenyl carbonate
By using molecular sieves to adsorb methanol during the synthesis of diphenyl carbonate, the problems of unfavorable reaction equilibrium and difficulty in removing byproducts were solved, achieving efficient production of diphenyl carbonate and reducing equipment costs and energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2021-04-30
- Publication Date
- 2026-06-12
AI Technical Summary
In existing methods for synthesizing diphenyl carbonate, the reaction equilibrium is unfavorable, and the byproduct methanol is difficult to remove effectively, resulting in low yield, high equipment cost, and complex process.
Molecular sieves are used to remove the generated methanol in a timely manner. By filling the space between the reactor and the condenser with molecular sieves, methanol is adsorbed by their pores, which avoids the difficulty of separating azeotropic substances and improves the conversion rate and yield of reactants.
Simplifying the process, reducing equipment requirements and costs, and increasing the yield of diphenyl carbonate and the conversion rate of phenol are in line with the concept of green chemistry.
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Figure BDA0003048216590000011
Abstract
Description
Technical Field
[0001] This invention belongs to the field of preparation of diphenyl carbonate, and particularly relates to a method for preparing diphenyl carbonate and the obtained diphenyl carbonate. Background Technology
[0002] Diphenyl carbonate is an important environmentally friendly chemical product, widely used in industry, agriculture, and medicine due to its low toxicity and non-polluting properties. There are three main methods for synthesizing diphenyl carbonate: oxidative carbonylation, phosgene synthesis, and transesterification. Compared to the former two, transesterification offers advantages such as relatively mild reaction conditions, less corrosiveness to equipment, and readily available and inexpensive raw materials, making it the most studied method currently. The transesterification of dimethyl carbonate with phenol to synthesize diphenyl carbonate is the most studied method among transesterification methods and the only one that has been industrialized.
[0003] The transesterification of dimethyl carbonate with phenol to synthesize diphenyl carbonate is a reversible reaction, and its reaction principle is as follows:
[0004]
[0005] The thermodynamic properties of this reaction were studied in the literature [Mei Fuming, Li Guangxing. The thermodynamic properties and homogenous catalysts for the synthesis of diphenylcarnonate by transesterification of dimethyl carbonate with phenol[J]. Chin.J.Synthetic Chem., 2003, 11(4): 320-326.]. At 453 K, the equilibrium constant of reaction (1) is 4.0 × 10⁻⁶. -3 The equilibrium constant of reaction (5) increases continuously with increasing temperature, so from a thermodynamic point of view, the reaction of dimethyl carbonate with phenol to form diphenyl carbonate is unfavorable. To improve the yield of diphenyl carbonate, it is necessary to find a catalyst with higher selectivity, reduce the formation of by-products, or improve the reaction process to remove the generated methanol, thereby shifting the equilibrium to the right.
[0006] Since methanol and dimethyl carbonate form an azeotrope in a 7:3 ratio under normal pressure, US patent 4252737 discloses a method to remove methanol by distilling off the azeotrope, thereby increasing the yield of diphenyl carbonate. However, this method requires the addition of excess dimethyl carbonate, and separating methanol and dimethyl carbonate from the azeotrope is also very difficult. Patent CN104086421A discloses a process for the continuous reaction synthesis of diphenyl carbonate using a fixed-bed coupled two-stage distillation column. This process achieves the goal of continuous reaction, but methanol still needs to form an azeotrope with dimethyl carbonate before it can be removed. In addition, the equipment cost is high, the process is complex, and the investment is large. Summary of the Invention
[0007] To overcome the problems existing in the prior art, the present invention provides a method for preparing diphenyl carbonate and the obtained diphenyl carbonate, wherein the use of molecular sieves can remove the generated methanol in a timely manner without consuming dimethyl carbonate, thereby improving the conversion rate of reactants and the yield of diphenyl carbonate.
[0008] This invention provides a method for preparing diphenyl carbonate, specifically in the following aspects:
[0009] 1. A method for preparing diphenyl carbonate, said method being carried out in an apparatus including a reactor and a condenser, comprising the following steps:
[0010] (1) Fill the space between the reactor and the condenser with molecular sieves;
[0011] (2) Add phenol and catalyst into the reactor;
[0012] (3) After heating, dimethyl carbonate is added dropwise to the reactor, and diphenyl carbonate is obtained through reaction.
[0013] 2. The method according to 1 above, wherein the catalyst is selected from organotitanium catalysts and / or organotin catalysts, preferably from tetraphenyl titanate and / or tetrabutyl titanate.
[0014] 3. According to the method described in 1 above, wherein the molar ratio of the catalyst to phenol is (0.001 to 0.1):1, preferably (0.005 to 0.05):1.
[0015] 4. According to the method described in 1 above, the molar ratio of dimethyl carbonate to phenol is (0.2-3):1, preferably (0.5-2):1.
[0016] 5. The method according to 1 above, characterized in that, in step (3), the temperature is raised to 160-260°C, preferably to 180-220°C.
[0017] 6. According to the method described in 1 above, wherein the pore size of the molecular sieve is greater than 0.38 nm and less than 0.47 nm, preferably from 4A molecular sieve.
[0018] 7. According to the method described in 1 above, wherein the weight of the molecular sieve is 0.2 to 3 times the weight of phenol, preferably 0.5 to 2 times.
[0019] 8. According to the method described in 1 above, wherein the molecular sieve is a calcined molecular sieve, preferably, the calcination is carried out at 300-800°C for 1-6 hours.
[0020] 9. The method according to any one of 1 to 8 above, wherein the molecular sieve is taken out and calcined after the reaction is completed, preferably at 300 to 800°C for 1 to 6 hours.
[0021] Another aspect of the present invention is to provide diphenyl carbonate obtained using the method described in the first aspect of the present invention. Detailed Implementation
[0022] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.
[0023] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.
[0024] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.
[0025] One object of the present invention is to provide a method for preparing diphenyl carbonate, the method being carried out in an apparatus including a reactor and a condenser, comprising the following steps:
[0026] (1) Fill the space between the reactor and the condenser with molecular sieves;
[0027] (2) Add phenol and catalyst into the reactor;
[0028] (3) After heating, dimethyl carbonate is added dropwise to the reactor, and diphenyl carbonate is obtained through reaction.
[0029] The reactor can be a multi-necked flask or a reaction vessel, and the condenser can be a condenser tube, etc.
[0030] In a preferred embodiment, the catalyst is selected from organotitanium catalysts and / or organotin catalysts.
[0031] In a further preferred embodiment, the catalyst is selected from at least one of tetraphenyl titanate and / or tetrabutyl titanate.
[0032] In a further preferred embodiment, the molar ratio of the catalyst to phenol is (0.001-0.1):1, preferably (0.005-0.05):1.
[0033] For example, the molar ratio of the catalyst to phenol is 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.008:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.035:1, 0.04:1, 0.045:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, or 0.1:1.
[0034] In a preferred embodiment, the molar ratio of dimethyl carbonate to phenol is (0.2-3):1, preferably (0.5-2):1.
[0035] For example, the molar ratio of dimethyl carbonate to phenol is 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.5:1, or 3:1.
[0036] In a preferred embodiment, the temperature is raised to 160-260°C, preferably to 180-220°C in step (3).
[0037] For example, in step (3), the temperature is raised to 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, and 220°C.
[0038] At the increased temperature, the generated methanol and dimethyl carbonate will undergo azeotropic reaction, forming a gas that moves towards the condenser.
[0039] In a preferred embodiment, the molecular sieve has pores larger than 0.38 nm and smaller than 0.47 nm.
[0040] Molecular sieves are synthetically produced hydrated aluminosilicates or natural zeolites that sieve molecules. Structurally, they contain numerous uniformly sized channels and neatly arranged pores. Molecular sieves with different pore sizes separate molecules of different sizes and shapes. They are characterized by high adsorption capacity, strong selectivity, and high temperature resistance, and are widely used in organic and petrochemical industries.
[0041] In a further preferred embodiment, the molecular sieve is 4A molecular sieve.
[0042] The kinetic diameters of dimethyl carbonate and methanol are 0.47–0.63 nm and 0.38 nm, respectively, while the pore size of the 4A molecular sieve is 0.4 nm, which is just enough to adsorb methanol while excluding dimethyl carbonate. Furthermore, the adsorbed methanol can be separated from the molecular sieve by calcination, and the calcined molecular sieve can be recycled. Currently, there are no reports on the application of molecular sieves in the preparation of diphenyl carbonate.
[0043] In this invention, a molecular sieve is placed between the reactor and the condenser. When the methanol and dimethyl carbonate azeotrope passes through the molecular sieve, the methanol enters the pores of the molecular sieve, while the dimethyl carbonate condenses and enters the flask to continue participating in the reaction, thereby improving the conversion rate of the reactants. Furthermore, this application does not require the addition of excess dimethyl carbonate, and it also avoids the problem of difficulty in separating methanol and dimethyl carbonate in the azeotrope.
[0044] If the molecular sieve is placed inside the reactor, it will not be able to separate methanol from the reaction liquid. Only when it is placed between the reactor and the condenser can it adsorb methanol from the azeotrope of distilled methanol and dimethyl carbonate, and the dimethyl carbonate will flow back into the reactor to continue to participate in the reaction, thereby improving the conversion rate of phenol.
[0045] In a preferred embodiment, the molecular sieve is used in an amount of 0.2 to 3 times the weight of phenol, preferably 0.5 to 2 times.
[0046] In a preferred embodiment, the molecular sieve is a calcined molecular sieve.
[0047] In a further preferred embodiment, the calcination is carried out at 300-800°C for 1-6 hours, more preferably at 400-600°C for 2-5 hours.
[0048] In a preferred embodiment, the molecular sieve is removed and calcined after the reaction is complete for recycling.
[0049] In a further preferred embodiment, the calcination treatment is carried out at 300–800°C for 1–6 hours, more preferably at 400–600°C for 2–5 hours.
[0050] For example, the calcination temperatures are 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃; the calcination times are 1h, 2h, 3h, 4h, 5h, and 6h.
[0051] A second objective of this invention is to provide diphenyl carbonate obtained using the method described in one objective of this invention.
[0052] The endpoints and any values of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.
[0053] Compared with the prior art, the present invention has the following beneficial effects:
[0054] (1) This invention has low equipment requirements, simple process and low investment cost;
[0055] (2) The present invention can effectively separate methanol by using molecular sieves without consuming dimethyl carbonate, thereby shifting the equilibrium to the right and improving the conversion rate of reactants and the yield of products. Specifically, the conversion rate of phenol increased from 3.89% to 42.02% after adding molecular sieves.
[0056] (3) This invention does not generate an azeotrope of dimethyl carbonate and methanol, and there is no need to separate them, thus saving energy and reducing costs;
[0057] (4) The molecular sieves used in this invention can be recycled and reused after calcination, which is in line with the current concept of green chemistry.
[0058] 【Example】
[0059] The present invention will be further described below through specific embodiments. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.
[0060] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.
[0061] The 4A molecular sieve used in the examples and comparative examples was obtained from Tianjin Guangfu Fine Chemical Research Institute, the phenol was obtained from Beijing Yili Fine Chemicals Co., Ltd., and the dimethyl carbonate was obtained from Shanghai Reagent Co., Ltd.
[0062] The 4A molecular sieve used in the example was a calcined 4A molecular sieve, and the calcination conditions were: 450℃ for 5 hours.
[0063] Tetrabutyl titanate can be purchased directly or prepared by referring to patent CN102675115A.
[0064] 【Example 1】
[0065] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 5 g of 4A molecular sieve was packed between the reactor and the condenser. 9.4 g of phenol and 0.31 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 42.02%, the selectivity for methyl phenyl carbonate was 42.66%, and the selectivity for diphenyl carbonate was 57.24%.
[0066] The reacted molecular sieve was calcined at 450℃ for 5 hours and then reused.
[0067] 【Example 2】
[0068] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 20 g of 4A molecular sieve was packed between the reactor and the condenser. 18.8 g of phenol and 0.84 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 42.77%, the selectivity for methyl phenyl carbonate was 27.94%, and the selectivity for diphenyl carbonate was 72.06%.
[0069] The reacted molecular sieve was calcined at 450℃ for 5 hours and then reused.
[0070] 【Example 3】
[0071] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 15 g of 4A molecular sieve was packed between the reactor and the condenser. 18.8 g of phenol and 0.84 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 13.90%, the selectivity for methyl phenyl carbonate was 14.31%, and the selectivity for diphenyl carbonate was 85.69%.
[0072] The reacted molecular sieve was calcined at 450℃ for 5 hours and then reused.
[0073] 【Example 4】
[0074] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 5 g of 4A molecular sieve was packed between the reactor and the condenser. 9.4 g of phenol and 0.42 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 18 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 44.60%, the selectivity for methyl phenyl carbonate was 40.06%, and the selectivity for diphenyl carbonate was 59.86%.
[0075] The reacted molecular sieve was calcined at 450℃ for 5 hours and then reused.
[0076] 【Example 5】
[0077] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 5 g of 4A molecular sieve was packed between the reactor and the condenser. 9.4 g of phenol and 0.64 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 27 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 46.06%, the selectivity for methyl phenyl carbonate was 40.91%, and the selectivity for diphenyl carbonate was 59.03%.
[0078] The reacted molecular sieve was calcined at 450℃ for 5 hours and then reused.
[0079] [Comparative Example]
[0080] Comparative Example 1
[0081] A 100 mL reaction vessel equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 9.4 g of phenol and 0.31 g of tetraphenyl titanate were added to the reaction vessel. After the temperature was raised to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 3.89%, the selectivity for methyl phenyl carbonate was 98.15%, and the selectivity for diphenyl carbonate was 1.45%.
[0082] Comparative Example 2
[0083] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 5 g of 3A molecular sieve (void less than 0.38 nm) was packed between the reactor and the condenser. 9.4 g of phenol and 0.31 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 5.74%, the selectivity for methyl phenyl carbonate was 90.34%, and the selectivity for diphenyl carbonate was 9.54%.
[0084] In Comparative Example 2, the selectivity of diphenyl carbonate was significantly lower than that in Example 1.
[0085] Comparative Example 3
[0086] A 100 mL reactor equipped with a stirrer, heater, and condenser was prepared. Under nitrogen protection, 5 g of 10X molecular sieve (void size greater than 0.63 nm) was packed between the reactor and the condenser. 9.4 g of phenol and 0.31 g of tetraphenyl titanate were added to the reactor. After heating to 180 °C, 9 g of dimethyl carbonate was added dropwise over 3 hours, followed by a 7-hour reaction. The conversion rate of phenol was 2.68%, the selectivity for methyl phenyl carbonate was 89.25%, and the selectivity for diphenyl carbonate was 9.84%.
[0087] In Comparative Example 3, the selectivity of diphenyl carbonate was significantly lower than that in Example 1.
[0088] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.
Claims
1. A method for preparing diphenyl carbonate, said method being carried out in an apparatus including a reactor and a condenser, comprising the following steps: (1) A molecular sieve is packed between the reactor and the condenser. The molecular sieve is selected from 4A molecular sieve and the weight of the molecular sieve is 0.2 to 3 times the weight of phenol. (2) Add phenol and catalyst into the reactor; (3) After heating to 160~260℃, dimethyl carbonate is added dropwise to the reactor. The molar ratio of dimethyl carbonate to phenol is (0.5~1):
1. Diphenyl carbonate is obtained by reaction.
2. The method according to claim 1, characterized in that, The catalyst is selected from organotitanium catalysts and / or organotin catalysts.
3. The method according to claim 1, characterized in that, The catalyst is selected from tetraphenyl titanate and / or tetrabutyl titanate.
4. The method according to claim 1, characterized in that, The molar ratio of the catalyst to phenol is (0.001~0.1):
1.
5. The method according to claim 1, characterized in that, The molar ratio of the catalyst to phenol is (0.005~0.05):
1.
6. The method according to claim 1, characterized in that, In step (3), the temperature is raised to 180~220℃.
7. The method according to claim 1, characterized in that, The molecular sieve is used in an amount that is 0.5 to 2 times the weight of phenol.
8. The method according to claim 1, characterized in that, The molecular sieve is a calcined molecular sieve.
9. The method according to claim 8, characterized in that, The calcination is carried out at 300~800℃ for 1~6 hours.
10. The method according to any one of claims 1 to 9, characterized in that, After the reaction is complete, the molecular sieve is removed and calcined.
11. The method according to claim 10, characterized in that, Perform at 300~800℃ for 1~6 hours.