Method for directly preparing dimethyl carbonate from carbon dioxide and methanol under catalysis of nano cerium oxide

Abstract

The invention belongs to the technical field of fine chemical preparation, and discloses a method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol through nano cerium oxide, which comprises the following steps: step S10, weighing nano cerium oxide, methanol and a deep eutectic solvent; s20, putting the weighed nano cerium oxide, methanol and the deep eutectic solvent into a beaker, and stirring and mixing; s30, adding the mixed solution into a reaction kettle, introducing carbon dioxide to replace air in the reaction kettle, and then heating the reaction kettle; s40, after the reaction kettle is cooled to the normal temperature, releasing the pressure and taking out the dimethyl carbonate; according to the scheme, by adding the deep eutectic solvent, water and a product in the reaction are separated, the reaction is promoted, homogeneous reaction and heterogeneous separation are realized, the highest conversion rate of methanol can reach 49.70%, and the selectivity of dimethyl carbonate exceeds 99%; the invention solves the problem of low conversion rate of the existing dimethyl carbonate preparation method.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemical preparation, and specifically relates to a method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide. Background Art

[0002] Dimethyl carbonate (DMC) is a widely used organic compound with the molecular formula C3H6O3. Due to its unique chemical properties and low toxicity, DMC has been widely used in many fields. DMC is an excellent solvent and is widely used in coatings, adhesives, medicines, pesticides and other fields. It can dissolve a variety of organic and inorganic substances, and its volatilization rate is moderate, which helps to improve the quality and performance of products.

[0003] DMC can also increase the octane number of gasoline, improve combustion performance, and reduce exhaust emissions. DMC is one of the important raw materials for the production of polycarbonate (PC), a high-performance engineering plastic widely used in electronics, automobile manufacturing, building materials and other fields. DMC is also widely used in the electrolyte of lithium-ion batteries (LIBs) and supercapacitors. It has good conductivity and stability, which helps to improve the performance and life of the battery.

[0004] Referring to the document with the existing publication (announcement) number CN106946706B, a method for preparing dimethyl carbonate by direct reaction of carbon dioxide and methanol is disclosed, wherein methanol, N,N-dialkyl imidazole bicarbonate ionic liquid and carbon dioxide are placed in an autoclave, the pressure of the carbon dioxide is 0.1 to 5 MPa, at room temperature to 100° C., N,N-dialkyl imidazole bicarbonate ionic liquid is used as a catalyst and a dehydrating agent, and the mixture is continuously stirred to directly react to obtain dimethyl carbonate; after the reaction is completed, dimethyl carbonate and methanol are removed by distillation.

[0005] The method of preparing dimethyl carbonate by direct reaction of carbon dioxide and methanol has the advantages of low raw material price, high atomic utilization rate, and green reactants and products. However, the process of generating dimethyl carbonate by reaction of carbon dioxide and methanol is limited by thermodynamic equilibrium. Without the addition of deep eutectic solvent, the conversion rate of the reaction is lower than that of the reaction. Summary of the invention

[0006] The purpose of this scheme is to provide a method for preparing dimethyl carbonate by directly catalyzing the reaction of carbon dioxide and methanol by nano-cerium oxide, so as to solve the problem of low conversion rate of existing dimethyl carbonate preparation methods.

[0007] In order to achieve the above object, the present invention provides a method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol with nano-cerium oxide, characterized in that it comprises the following steps:

[0008] Step S10: weighing nano-cerium oxide, methanol and a deep eutectic solvent;

[0009] Step S20: putting weighed nano-cerium oxide, methanol and deep eutectic solvent into a beaker and stirring and mixing;

[0010] Step S30: adding the mixed solution into a reactor, introducing carbon dioxide to replace the air in the reactor, and then heating the reactor;

[0011] Step S40: After the reactor is cooled to room temperature, the pressure is released and dimethyl carbonate is taken out.

[0012] Furthermore, the heating temperature of step S30 is 80° C. to 140° C.; and the reaction time of step S30 is 2 h to 16 h.

[0013] Furthermore, the carbon dioxide pressure in step S30 is 1 MPa to 6 MPa.

[0014] Furthermore, in step S30, the initial pressure of carbon dioxide is 3 MPa, the reaction temperature is 100° C., and the reaction time is 4 h.

[0015] Furthermore, the molar ratio of the methanol, the deep eutectic solvent and the nano-cerium oxide is 0.025-0.3:0.05:0.001-0.006.

[0016] Furthermore, the deep eutectic solvent is obtained by mixing and reacting a hydrogen bond donor with a hydrogen bond acceptor.

[0017] Furthermore, the hydrogen bond donor includes one or more of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, methanesulfonic acid, trifluoromethanesulfonic acid, formic acid, acetic acid, and oxalic acid.

[0018] Furthermore, the hydrogen bond acceptor includes one or more of L-carnitine, urea, acetamide, benzamide, 4-aminotoluene-3-sulfonic acid, 4-pyridinecarboxylic acid, proline, and 2-pyridinecarboxylic acid.

[0019] The beneficial effect of this solution is that the present invention separates the water and product in the reaction by adding a deep eutectic solvent, promotes the reaction and realizes homogeneous reaction and heterogeneous separation, and can make the maximum conversion rate of methanol reach 49.70%, and the selectivity of dimethyl carbonate exceeds 99%.

[0020] Furthermore, the reactor includes a reactor body and a stirring assembly arranged in the reactor body, the stirring assembly includes an air supply pipe, a connecting pipe and a stirring pipe, the air inlet end of the air supply pipe is connected to a high-pressure gas source, the air outlet end of the air supply pipe is connected to one end of the connecting end pipe, the free end of the connecting pipe is connected to one end of the stirring pipe, and the free end of the stirring pipe is provided with an air outlet; the connecting pipe and the stirring pipe are both made of flexible materials; the connecting pipe is a connecting pipe that rotates one circle along the central axis of the air supply pipe, and after the connecting pipe and the stirring pipe are filled with gas, the connecting pipe is reset and rotates one circle along the central axis of the air supply pipe.

[0021] The principle and effect of this scheme are as follows: (1) When replacing the air in the reactor, the prior art opens a gas hole at the position of the reactor cover to pass the gas into the reactor to replace the air. However, this method has some problems. First, the introduced gas is prone to form a local high-concentration area at the outlet position, because after the gas enters from a single outlet, it will diffuse along the path of least resistance, usually flowing upward or along the wall of the reactor, rather than being evenly distributed throughout the space inside the reactor. Secondly, when the gas outlet is far from the material liquid surface, part of the gas has been mixed with the air in the reactor before reaching the material liquid surface. The gas requires a longer time and a larger flow rate to reach the vicinity of the material, which results in poor air replacement efficiency near the material. Please refer to the existing gas replacement device and reactor system with the publication (announcement) number CN106390887B. (2) In this solution, since the connecting tube and the stirring tube are both made of flexible materials, after the reaction solution is poured into the kettle, the connecting tube and the stirring tube will float on the surface of the solution due to the buoyancy of the solution, so that the position of the air outlet of the stirring tube is adjusted to be close to the liquid surface of the reaction kettle material, thereby improving the air replacement efficiency and effect. (3) Since the air supply pipe is connected to a high-pressure gas source, high-pressure carbon dioxide can be sent into the connecting tube and the stirring tube through the air supply pipe, and when the gas fills the stirring tube, it is ejected from the air outlet of the stirring tube. Since the connecting tube is a connecting tube that rotates one circle along the central axis of the air supply pipe, after the stirring tube and the connecting tube are filled with gas, the stirring tube will rotate one circle along the central axis of the air supply pipe, thereby stirring the liquid surface. At the same time, since during the rotation process, the air outlet has been ejecting carbon dioxide to the liquid surface, and the bubbles will be broken by the rotation of the stirring tube, forming multiple bubbles, thereby increasing the reaction area of ​​carbon dioxide and gas, and increasing the absorption efficiency of carbon dioxide and solution. After the stirring tube rotates to the initial position, since the carbon dioxide is discharged from the air outlet, the connecting tube and the stirring tube are not filled, so the connecting tube is turned again, over and over again, so that the stirring tube can periodically stir the water while introducing carbon dioxide gas for replacement.

[0022] Furthermore, the air supply pipe is a corrugated pipe; the outlet end of the air outlet faces the bottom of the kettle body; and a one-way valve is provided at the outlet end of the air outlet.

[0023] The principle and effect of this scheme are as follows: (1) The air supply pipe is set as a bellows so that the connecting pipe and the stirring pipe can move up and down with the height of the liquid level, so that the stirring pipe floats on the liquid surface and the air outlet is close to the liquid surface, thereby improving the air replacement efficiency and effect. (2) The air outlet end of the air outlet is facing the bottom of the kettle so that the carbon dioxide sprayed from the air outlet can be sprayed onto the liquid surface, thereby generating more bubbles on the liquid surface. Under the action of the stirring pipe, the absorption rate of carbon dioxide and solution is higher. (3) A one-way valve is set to prevent the solution from entering the stirring pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Chromatogram of the direct preparation of dimethyl carbonate from carbon dioxide and methanol;

[0025] Figure 2 The structure of the reactor of the present invention is shown in FIG. Figure 1 ;

[0026] Figure 3 The structure of the reactor of the present invention is shown in FIG. Figure 2 .

[0027] The reference numerals in the drawings of the specification include: kettle body 1 , stirring assembly 2 , air supply pipe 21 , connecting pipe 22 , stirring pipe 23 , air outlet 231 , solution 3 . DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0029] The reagents and the like used in the examples of the present invention, unless otherwise specified, can be obtained through commercial channels. The experimental methods used in the examples of the present invention, unless otherwise specified, are conventional methods.

[0030] The reaction process of the present invention is as follows:

[0031]

[0032] In a specific embodiment, the steps of synthesizing dimethyl carbonate include:

[0033] Step S10: mixing methanol, deep eutectic solvent and nano-cerium oxide catalyst in a molar ratio of (0.025-0.3):0.05:(0.001-0.006), and adding the mixture into a reaction kettle;

[0034] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0035] Step S30: introducing carbon dioxide gas at a pressure of 1 MPa to 5 MPa into the reactor;

[0036] Step S40: heating the reactor to 80-140° C. to start the reaction, and the reaction time is 2-16 hours;

[0037] Step S50: After the reaction is completed, the temperature is stopped from being raised, and after the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and analyzed using gas chromatography.

[0038] The following describes the invention in conjunction with specific embodiments.

[0039] Embodiment 1:

[0040] This embodiment provides screening of the reaction time of preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0041] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3455 g), methanol (0.0202 mol, 0.6452 g), and deep eutectic solvent (0.1005 mol, 10.4562 g) in a beaker, stir them evenly, and then add them into a 25 ml reaction kettle;

[0042] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0043] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0044] Step S40: heating the reactor to 120°C and starting the reaction for 2 hours;

[0045] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used to analyze the product. The result shows that the conversion rate of methanol is 47.18%, and the selectivity of dimethyl carbonate is 91.77%.

[0046] Embodiment 2:

[0047] This embodiment provides a screening of the reaction time of preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0048] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3389 g), methanol (0.0202 mol, 0.6448 g), and deep eutectic solvent (0.1000 mol, 10.4036 g) in a beaker, stir them evenly, and then add them into a 25 ml reaction kettle;

[0049] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0050] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0051] Step S40: heating the reactor to 120°C and starting the reaction for 4 hours;

[0052] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 48.63% and the selectivity of dimethyl carbonate is 92.77%.

[0053] Embodiment 3:

[0054] This embodiment provides a screening of the reaction time of preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0055] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3430 g), methanol (0.0203 mol, 0.6496 g), and deep eutectic solvent (0.1012 mol, 10.5283 g), stir them evenly in a beaker, and then add them into a 25 ml reaction kettle;

[0056] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0057] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0058] Step S40: heating the reactor to 120°C and starting the reaction for 6 hours;

[0059] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 72.19% and the selectivity of dimethyl carbonate is 70.33%.

[0060] Embodiment 4:

[0061] This example provides a screening of the reaction temperature for preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0062] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3498 g), methanol (0.1012 mol, 3.2388 g), and deep eutectic solvent (0.0501 mol, 5.2102 g) in a beaker, stir them evenly, and then add them into a 25 ml reactor;

[0063] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0064] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0065] Step S40: heating the reactor to 90°C and starting the reaction for 4 hours;

[0066] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 34.47% and the selectivity of dimethyl carbonate is 56.62%.

[0067] Embodiment 5:

[0068] This example provides a screening of the reaction temperature for preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0069] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3399 g), methanol (0.1004 mol, 3.2142 g), and deep eutectic solvent (0.0501 mol, 5.2077 g) in a beaker, stir them evenly, and then add them into a 25 ml reactor;

[0070] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0071] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0072] Step S40: heating the reactor to 100°C and starting the reaction for 4 hours;

[0073] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 30.18%, and the selectivity of dimethyl carbonate is 81.84%.

[0074] Embodiment 6:

[0075] This example provides a screening of the reaction temperature for preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide, and the specific steps are as follows:

[0076] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3378 g), methanol (0.1004 mol, 3.2814 g), and deep eutectic solvent (0.0509 mol, 5.2895 g), stir them evenly in a beaker, and then add them into a 25 ml reaction kettle;

[0077] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0078] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0079] Step S40: heating the reactor to 110° C. and starting the reaction for 4 hours;

[0080] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 25.45%, and the selectivity of dimethyl carbonate is 73.90%.

[0081] Embodiment 7:

[0082] This embodiment provides the screening of the reaction pressure of preparing dimethyl carbonate by using carbon dioxide and methanol catalyzed by nano-cerium oxide, and the specific steps are as follows:

[0083] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3440 g), methanol (0.1006 mol, 3.2185 g), and deep eutectic solvent (0.0500 mol, 5.2060 g) in a beaker, stir them evenly, and then add them into a 25 ml reaction kettle;

[0084] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0085] Step S30: continuously introducing carbon dioxide gas at a pressure of 2 MPa into the reactor;

[0086] Step S40: heating the reactor to 100°C and starting the reaction for 4 hours;

[0087] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 51.77% and the selectivity of dimethyl carbonate is 75.79%.

[0088] Embodiment 8:

[0089] This embodiment provides the screening of the reaction pressure of preparing dimethyl carbonate by using carbon dioxide and methanol catalyzed by nano-cerium oxide, and the specific steps are as follows:

[0090] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3473 g), methanol (0.1013 mol, 3.2423 g), and deep eutectic solvent (0.0513 mol, 5.3334 g), stir them evenly in a beaker, and then add them into a 25 ml reaction kettle;

[0091] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0092] Step S30: continuously introducing carbon dioxide gas at a pressure of 3 MPa into the reactor;

[0093] Step S40: heating the reactor to 100°C and starting the reaction for 4 hours;

[0094] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used to analyze the product. The result shows that the conversion rate of methanol is 55.11%, and the selectivity of dimethyl carbonate is 91.29%.

[0095] Embodiment 9:

[0096] This embodiment provides the screening of the reaction pressure of preparing dimethyl carbonate by using carbon dioxide and methanol catalyzed by nano-cerium oxide, and the specific steps are as follows:

[0097] Step S10: weigh nano-cerium oxide (0.0020 mol, 0.3417 g), methanol (0.1003 mol, 3.2095 g), and deep eutectic solvent (0.0508 mol, 5.2854 g), stir them evenly in a beaker, and then add them into a 25 ml reactor;

[0098] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0099] Step S30: continuously introducing carbon dioxide gas at a pressure of 2 MPa into the reactor;

[0100] Step S40: heating the reactor to 100°C and starting the reaction for 4 hours;

[0101] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and gas chromatography is used for analysis. The results show that the conversion rate of methanol is 58.19% and the selectivity of dimethyl carbonate is 74.78%.

[0102] Through Examples 1 to 9, it is determined that the optimal reaction conditions in the present invention are reaction time 4 h, reaction temperature 100° C., and reaction pressure 3 MPa.

[0103] Example 10

[0104] Next, the reactant ratio is screened. The specific steps are as follows:

[0105] Step S10: weigh methanol (0.025 mol-0.3 mol), deep eutectic solvent (0.01-0.1 mmol), and nano-cerium oxide (0.001 mol-0.006 mmol), stir them evenly in a beaker, and then add them into a 25 ml reaction kettle;

[0106] Step S20: Seal the reactor and introduce carbon dioxide until the initial pressure of the system reaches 1 MPa, then discharge the gas, and repeat the operation 2 to 3 times to replace the air in the reactor;

[0107] Step S30: continuously introducing carbon dioxide gas at a pressure of 5 MPa into the reactor;

[0108] Step S40: heating the reactor to 110° C. and starting the reaction for 4 hours;

[0109] Step S50: After the reaction is finished, the temperature is stopped from rising. After the temperature in the reactor drops to room temperature, the pressure is released, the reactor is opened, the product is collected, and the product is analyzed using gas chromatography.

[0110] The chromatographic analysis results of methanol, deep eutectic solvent, and nano-cerium oxide at different molar ratios are shown in Table 1.

[0111]

[0112]

[0113] Table 1

[0114] As can be seen from Table 1, the highest methanol conversion rate is 83.19%, and the highest selectivity of tert-butyl acrylate is 97.87%. At this time, the molar ratio of methanol, deep eutectic solvent, and nano-cerium oxide is 62.5:12.5:1. Therefore, the optimal molar ratio of methanol, deep eutectic solvent, and nano-cerium oxide in the present invention is 62.5:12.5:1. Under the premise of ensuring the stability of the methanol conversion rate, considering the high volatility and low boiling point characteristics of methanol, an excess of methanol (0.25 mol, i.e. 6.4 g) was deliberately added to the reaction. At the same time, the deep eutectic solvent plays an important role in this process. It uses the difference in polarity to separate the water generated in the reaction from the product, eliminates the influence of water, and promotes the main reaction to proceed in the forward direction. In addition, too high a temperature will damage the catalytic activity of nano-cerium oxide. Therefore, after optimization, the selected reaction temperature is 100°C and the reaction time is 4 hours.

[0115] Embodiment 11:

[0116] This embodiment provides a reaction kettle to achieve better replacement and reaction effects of carbon dioxide in the above experiment.

[0117] See also Figure 2 A reaction kettle comprises a kettle body 1 and a stirring assembly 2 arranged in the kettle body 1. The kettle body 1 and the air inlet end, the air outlet end and the feed port of the kettle body 1 are all prior arts and will not be described in detail herein.

[0118] See also Figure 2 and Figure 3The stirring assembly 2 includes an air supply pipe 21, a connecting pipe 22 and a stirring pipe 23. The air inlet end of the air supply pipe 21 is connected to a blower, which is used to deliver the high-pressure carbon dioxide required for the experiment into the connecting pipe 22 and the stirring pipe 23 through the air supply pipe 21. A section of the air supply pipe 21 is set as a bellows or a telescopic pipe; the air outlet end of the air supply pipe 21 is connected to one end of the connecting end pipe 22, and the free end of the connecting pipe 22 is connected to one end of the stirring pipe 23. The free end of the stirring pipe 23 is provided with an air outlet 231, and the air outlet end of the air outlet 231 is about 3-4 cm away from the bottom of the stirring pipe 23, so that the air outlet end of the air outlet 231 will not directly contact the liquid surface of the solution 3, and the air outlet direction of the air outlet end is toward the bottom of the kettle body 1, so that the carbon dioxide gas sprayed from the air outlet end can be toward the liquid surface of the solution 3; in order to prevent the solution 3 from entering the stirring A one-way valve is provided on the outlet end of the air outlet 231 in the tube 23; the connecting tube 22 and the stirring tube 23 are both made of flexible material, such as the material used for air bags or balloons, so that the connecting tube 22 and the stirring tube 23 can float on the surface of the solution 3, so that the position of the air outlet 231 of the stirring tube 23 is adjusted to be close to the liquid surface of the reactor material, thereby improving the air replacement efficiency and effect; the connecting tube 22 is the connecting tube 22 that has been rotated one circle along the central axis of the air supply tube 21, that is, before the gas is introduced into the connecting tube 22, the connecting tube 22 has been rotated one circle (knob) along the central axis of the air supply tube 21, and after the connecting tube 22 and the stirring tube 23 are filled with gas, the connecting tube whose knob is turned is reset by the action of the gas, thereby driving the connecting tube 22 and the stirring tube 23 to rotate one circle along the central axis of the air supply tube 21, thereby stirring the liquid surface. At the same time, during the rotation process, the gas outlet 231 is constantly spraying carbon dioxide toward the liquid surface, and the bubbles are burst by the rotation of the stirring tube 23, forming multiple bubbles, thereby increasing the reaction area between carbon dioxide and gas, and increasing the absorption efficiency of carbon dioxide and solution. After the stirring tube 23 rotates to the initial position, since carbon dioxide is discharged from the gas outlet 231, the connecting tube 22 and the stirring tube 23 are not filled, so that the connecting tube 22 is turned again, and the cycle repeats, so that the stirring tube 23 can periodically stir the water body while introducing carbon dioxide gas for replacement.

[0119] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol with nano-cerium oxide, characterized in that: The steps include: Step S10: weighing nano-cerium oxide, methanol and a deep eutectic solvent; Step S20: putting weighed nano-cerium oxide, methanol and deep eutectic solvent into a beaker and stirring and mixing; Step S30: adding the mixed solution into a reactor, introducing carbon dioxide to replace the air in the reactor, and then heating the reactor; Step S40: After the reactor is cooled to room temperature, the pressure is released and dimethyl carbonate is taken out.

2. The method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide according to claim 1, characterized in that: The heating temperature of step S30 is 80° C. to 140° C.; the reaction time of step S30 is 2 h to 16 h.

3. The method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide according to claim 1, characterized in that: The carbon dioxide pressure in step S30 is 1 MPa to 6 MPa.

4. The method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide according to claim 1, characterized in that: In step S30, the initial pressure of carbon dioxide is 3 MPa, the reaction temperature is 100° C., and the reaction time is 4 h.

5. The method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide according to claim 1, characterized in that: The molar ratio of the methanol, the deep eutectic solvent and the nano-cerium oxide is 0.025-0.3:0.05:0.001-0.

006.

6. The method for directly preparing dimethyl carbonate by catalyzing carbon dioxide and methanol using nano-cerium oxide according to claim 1, characterized in that: The deep eutectic solvent is obtained by mixing and reacting a hydrogen bond donor with a hydrogen bond acceptor.

7. The method for directly preparing dimethyl carbonate by using nano-cerium oxide to catalyze carbon dioxide and methanol according to claim 6, characterized in that: The hydrogen bond donor includes one or more of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, methanesulfonic acid, trifluoromethanesulfonic acid, formic acid, acetic acid, and oxalic acid.

8. The method for directly preparing dimethyl carbonate by using nano-cerium oxide to catalyze carbon dioxide and methanol according to claim 6, characterized in that: The hydrogen bond acceptor includes one or more of L-carnitine, urea, acetamide, benzamide, 4-aminotoluene-3-sulfonic acid, 4-pyridinecarboxylic acid, proline, and 2-pyridinecarboxylic acid.

9. The method for directly preparing dimethyl carbonate by using nano-cerium oxide to catalyze carbon dioxide and methanol according to claim 1, characterized in that: The reaction kettle comprises a kettle body (1) and a stirring assembly (2) arranged in the kettle body (1); the stirring assembly (2) comprises an air supply pipe (21), a connecting pipe (22) and a stirring pipe (23); the air inlet end of the air supply pipe (21) is connected to a high-pressure gas source; the air outlet end of the air supply pipe (21) is connected to one end of the connecting pipe (22); the free end of the connecting pipe (22) is connected to one end of the stirring pipe (23); the free end of the stirring pipe (23) is provided with an air outlet (231); the connecting pipe (22) and the stirring pipe (23) are both made of flexible materials; the connecting pipe (22) is a connecting pipe (22) that has been rotated one circle along the central axis of the air supply pipe (21); after the connecting pipe (22) and the stirring pipe (23) are filled with gas, the connecting pipe (22) is reset and rotates one circle along the central axis of the air supply pipe (21).

10. The method for directly preparing dimethyl carbonate by using carbon dioxide and methanol catalyzed by nano-cerium oxide according to claim 9, characterized in that: The air delivery pipe (21) is a corrugated pipe; the outlet end of the air outlet (231) faces the bottom of the kettle body (1); and a one-way valve is provided at the outlet end of the air outlet (231).

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