Sodium methoxide feeding system for preparing PTMEG through alcoholysis reaction and feeding method of sodium methoxide feeding system

Abstract

The invention discloses a sodium methoxide feeding system for preparing PTMEG (polytetramethylene ether glycol) through alcoholysis reaction and a feeding method of the sodium methoxide feeding system. The method has the advantages that after sodium methoxide is diluted, the condition of pipeline blockage or material breakage caused by sodium methoxide precipitation can be prevented; meanwhile, in order to ensure the original sodium methoxide feeding amount, the conveying flow needs to be expanded, so that the problems that the sodium methoxide conveying flow is too low and cannot be accurately measured and the addition amount cannot be accurately controlled can be solved, the incomplete alcoholysis reaction caused by insufficient sodium methoxide addition is prevented, the waste caused by excessive sodium methoxide addition can be effectively reduced, and the production cost is reduced. And the shortening of the regeneration period of the ion exchange resin in the later working section caused by excessive addition of sodium methoxide is avoided.

Description

Technical Field The invention relates to the technical field of producing PTMEG by a perfluorosulfonic acid resin method, and in particular to a sodium methoxide feeding system and a feeding method for preparing PTMEG by an alcoholysis reaction. Background Art In the perfluorosulfonic acid resin process for producing PTMEG, THF polymerizes with acetic anhydride as a chain initiator and end-capping agent to form the intermediate product PTMEA. PTMEA then undergoes alcoholysis with methanol in a reactive distillation column to produce PTMEG. During the alcoholysis reaction, sodium methoxide is homogeneously added to the column as a catalyst. The sodium methoxide addition ratio must be strictly controlled to 250-270 ppm (sodium methoxide / PTMEA mass ratio). The current process involves adding sodium methoxide to the system, including a 40m³ sodium methoxide storage tank, an 18L flow chamber, two 15μm precision filters, and two 10L / h diaphragm metering pumps. Sodium methoxide with a mass concentration of 30% is pumped from the auxiliary tank area to the third floor of the framework via the metering pumps, where it then joins the liquid methanol feed line. At full capacity, the sodium methoxide flow rate is controlled at 7kg / h. However, this addition process presented numerous challenges. First, at low temperatures, sodium methoxide in a 30% sodium methoxide solution could easily precipitate and clog pipes and filters, potentially causing feedstock shortages in the reaction distillation column. Second, due to the low flow rate of 7 kg / h, the flow velocity in the pipeline was too low, resulting in large measurement errors for the flowmeter and inaccurate detection. Furthermore, the diaphragm metering pump experienced significant flow fluctuations during speed and stroke adjustments, leading to insufficient or excessive catalyst addition. Third, the pipeline between the auxiliary tank area and the third floor of the framework was approximately 42 meters long and had a large volume (approximately 20.6 liters). After the metering pump was started, the entire process of venting and displacing the pipeline and allowing the sodium methoxide to reach the tee on the third floor took over two hours, resulting in significant startup delays. Furthermore, the entire pipeline from the auxiliary tank area to the third floor of the framework required electric heating to control temperature to prevent sodium methoxide from crystallizing at low temperatures. Inadequate heating or damaged insulation could easily cause sodium methoxide precipitation, leading to serious process failures such as feedstock shortages. Therefore, a new sodium methoxide feeding system and method are urgently needed to solve the above problems. Summary of the Invention The first object of the present invention is to provide a sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction; A second object of the present invention is to provide a method for feeding sodium methoxide to prepare PTMEG by alcoholysis reaction.

[0001] The first object of the present invention is implemented by the following technical solutions: A sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction, comprising a methanol storage tank, a methanol pump, a sodium methoxide stock solution storage tank, a sodium methoxide feeding metering tank, a sodium methoxide metering pump, and an alcoholysis reaction distillation tower; The outlet of the methanol storage tank is communicated with the inlet of the methanol pump, and the outlet of the methanol pump is communicated with the top inlet of the sodium methoxide feed metering tank; the outlet of the sodium methoxide stock solution storage tank is communicated with the bottom inlet of the sodium methoxide feed metering tank through a pipeline, the outlet of the sodium methoxide feed metering tank is communicated with the inlet of the sodium methoxide metering pump through a pipeline, and the outlet of the sodium methoxide metering pump is communicated with an inlet of a tee through a pipeline; the outlet of the methanol pump is also communicated with the other inlet of the tee through a pipeline, the outlet of the tee is communicated with the inlet of 1# pipeline mixer, the outlet of the 1# pipeline mixer and the outlet of the PTMEA feed pipeline are both communicated with the inlet of 2# pipeline mixer, and the outlet of the 2# pipeline mixer is communicated with the liquid phase feed port of the alcoholysis reaction distillation tower through a reaction distillation tower liquid phase feed pipeline; A methanol feed valve and a methanol flowmeter are provided on the pipeline connecting the methanol pump and the tee pipe; a diluent feed valve is provided at the outlet of the sodium methoxide feed metering tank; and a diluent flowmeter is provided on the pipeline connecting the sodium methoxide metering pump and the tee pipe; A methanol inlet valve is provided on the pipeline connecting the methanol pump and the sodium methoxide feed metering tank, and a sodium methoxide inlet valve is provided on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank.

[0002] Furthermore, a sampling port is provided at the outlet of the sodium methoxide feed metering tank, a sampling tube is screwed to the sampling port, and a sampling valve is also provided at the sampling port.

[0003] Furthermore, a filter is provided on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank.

[0004] Furthermore, the number of the sodium methoxide feed metering tanks is two, and the two sodium methoxide feed metering tanks are arranged in parallel.

[0005] Furthermore, there are two sodium methoxide metering pumps, and the two sodium methoxide metering pumps are arranged in parallel.

[0006] Furthermore, a liquid level sensor is provided in the sodium methoxide feed metering tank, the signal output end of the liquid level sensor is signal-connected to the signal input end of the controller, and the signal output end of the controller is signal-connected to the signal input ends of the methanol inlet valve, the sodium methoxide inlet valve and the diluent feed valve respectively.

[0007] Furthermore, it also includes a nitrogen source, the outlet of the nitrogen source is connected to the air inlet of the sodium methoxide feed metering tank through a pipeline, and a nitrogen valve is provided at the outlet of the nitrogen source; a pressure sensor is provided in the sodium methoxide feed metering tank, a vent is opened at the top of the sodium methoxide feed metering tank, and a vent valve is provided at the vent; The signal output end of the pressure sensor is signal-connected to the signal input end of the controller, and the signal output end of the controller is signal-connected to the signal input ends of the nitrogen valve and the relief valve respectively.

[0008] Furthermore, an electric heating tape is laid on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank, and a temperature sensor is provided at the outlet of the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank; the signal output end of the temperature sensor is signal-connected to the signal input end of the controller, and the signal output end of the controller is signal-connected to the signal input end of the start-stop switch of the electric heating tape.

[0009] The second object of the present invention is implemented by the following technical solutions: A method for feeding sodium methoxide to prepare PTMEG by alcoholysis reaction comprises the following steps: (1) adding the sodium methoxide stock solution in the sodium methoxide stock solution storage tank and the methanol in the methanol storage tank into the sodium methoxide feed metering tank respectively, and diluting the sodium methoxide stock solution with methanol to obtain a sodium methoxide diluted solution; (2) mixing the sodium methoxide dilution obtained in step (1) with the methanol solution to obtain a primary mixed solution; (3) The initially mixed solution obtained in step (2) is mixed with PTMEA and then introduced into an alcoholysis reaction distillation tower.

[0010] Furthermore, in the step (1), the mass concentration of sodium methoxide in the sodium methoxide dilution solution is 1.5-3%; in the step (2), the mass concentration of sodium methoxide in the initial mixed solution is 840ppm-890ppm; and in the step (3), the mass concentration of sodium methoxide in the mixed solution is 250ppm-270ppm.

[0011] Advantages of the present invention: By diluting the sodium methoxide, pipeline blockage or material interruption caused by sodium methoxide precipitation can be prevented; at the same time, in order to ensure the original sodium methoxide feed amount, the delivery flow rate needs to be expanded, which can solve the problem that the sodium methoxide delivery flow rate is too low and the addition amount cannot be accurately measured or accurately controlled, prevents incomplete alcoholysis reaction caused by insufficient sodium methoxide addition, and effectively reduces waste caused by excessive sodium methoxide addition, avoiding the shortening of the regeneration cycle of the ion exchange resin in the later stage caused by excessive sodium methoxide addition. By moving the intersection tee of sodium methoxide and methanol solution to the outlet of the sodium methoxide metering pump, the distance of the sodium methoxide delivery pipeline is greatly shortened, and the time for sodium methoxide to enter the alcoholysis reaction distillation tower is greatly shortened, thereby effectively reducing the time it takes for the system to return to normal after sodium methoxide interruption. The present invention can improve the economic benefits of the factory, reduce the operating risks of personnel, and reduce the possibility of process accidents. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of system connections in Example 1; Figure 2 This is a control principle diagram of Example 1.

[0012] In the figure: methanol storage tank 1, sodium methoxide stock solution storage tank 2, sodium methoxide feed metering tank 3, sodium methoxide metering pump 4, alcoholysis reaction distillation tower 5, T-piece 6, 1# pipeline mixer 7, PTMEA feed pipeline 8, methanol inlet valve 9, sodium methoxide inlet valve 10, methanol feed valve 11, sampling tube 12, sampling valve 13, filter 14, liquid level sensor 15, controller 16, nitrogen source 17, nitrogen valve 18, pressure sensor 19, bleed valve 20, electric heating tape 21, temperature sensor 22, methanol flowmeter 23, diluent feed valve 24, methanol pump 25, 2# pipeline mixer 26, reaction distillation tower liquid phase feed pipeline 27, diluent flowmeter 28. DETAILED DESCRIPTION The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0013] Example 1: like Figures 1 to 2 The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction shown in FIG2 includes a methanol storage tank 1, a methanol pump 25, a sodium methoxide stock solution storage tank 2, a sodium methoxide feeding metering tank 3, a sodium methoxide metering pump 4, and an alcoholysis reaction distillation tower 5; The outlet of the methanol storage tank 1 is communicated with the inlet of the methanol pump 25, and the outlet of the methanol pump 25 is communicated with the top inlet of the sodium methoxide feed metering tank 3; the outlet of the sodium methoxide stock solution storage tank 2 is communicated with the bottom inlet of the sodium methoxide feed metering tank 3 through a pipeline, the outlet of the sodium methoxide feed metering tank 3 is communicated with the inlet of the sodium methoxide metering pump 4 through a pipeline, and the outlet of the sodium methoxide metering pump 4 is communicated with one inlet of a tee pipe 6 through a pipeline; the outlet of the methanol pump 25 is also communicated with the other inlet of the tee pipe 6 through a pipeline, the outlet of the tee pipe 6 is communicated with the inlet of the 1# pipeline mixer 7, and the outlet of the 1# pipeline mixer 7 and the outlet of the PTMEA feed pipeline 8 are both connected to the 2# The inlet of the pipeline mixer 26 is connected, and the outlet of the 2# pipeline mixer 26 is connected to the liquid phase feed port of the alcoholysis reaction distillation tower 5 through the reaction distillation tower liquid phase feed pipeline 27; a methanol feed valve 11 and a methanol flowmeter 23 are provided on the pipeline connecting the methanol pump 25 and the tee pipe 6; a diluent feed valve 24 is provided at the outlet of the sodium methoxide feed metering tank 3; a diluent flowmeter 28 is provided on the pipeline connecting the sodium methoxide metering pump 4 and the tee pipe 6; a methanol liquid inlet valve 9 is provided on the pipeline connecting the methanol pump 25 and the sodium methoxide feed metering tank 3, and a sodium methoxide liquid inlet valve 10 is provided on the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3. An electric heating cable 21 is installed on the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3. A temperature sensor 22 is installed at the outlet of the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3. A filter 14 is installed on the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3. A liquid level sensor 15 is installed in the sodium methoxide feed metering tank 3.

[0014] This embodiment also includes a nitrogen source 17, the outlet of the nitrogen source 17 is connected to the air inlet of the sodium methoxide feed metering tank 3 through a pipeline, and a nitrogen valve 18 is provided at the outlet of the nitrogen source 17; a pressure sensor 19 is provided in the sodium methoxide feed metering tank 3, a vent is provided at the top of the sodium methoxide feed metering tank 3, and a vent valve 20 is provided at the vent; a sampling port is provided at the outlet of the sodium methoxide feed metering tank 3, a sampling tube 12 is screwed at the sampling port, and a sampling valve 13 is also provided at the sampling port.

[0015] The signal output ends of the liquid level sensor 15, the pressure sensor 19 and the temperature sensor 22 are all connected to the signal input ends of the controller 16, and the signal output ends of the controller 16 are respectively connected to the signal input ends of the methanol inlet valve 9, the sodium methoxide inlet valve 10, the diluent feed valve 24, the nitrogen valve 18, the relief valve 20 and the start / stop switch of the electric heating tape 21.

[0016] In this embodiment, there are two sodium methoxide feed metering tanks 3, and the two sodium methoxide feed metering tanks 3 are arranged in parallel. There are two sodium methoxide metering pumps 4, and the two sodium methoxide metering pumps 4 are arranged in parallel.

[0017] Job Description: When using this embodiment, it is first necessary to prepare a sodium methoxide dilution solution: open the sodium methoxide inlet valve 10 to allow the sodium methoxide stored in the high-position sodium methoxide stock solution storage tank 2, with a mass concentration of 30%, to flow through the pipeline into the sodium methoxide feed metering tank 3; when the liquid level sensor 15 detects that the liquid level in the sodium methoxide feed metering tank 3 has reached 4% of the total liquid level, close the sodium methoxide inlet valve 10 and stop adding sodium methoxide. Then, open the methanol inlet valve 9 and start the methanol pump 25 to allow the methanol solution in the methanol storage tank 1 to enter the sodium methoxide feed metering tank 3; when the liquid level sensor 15 detects that the liquid level in the sodium methoxide feed metering tank 3 has reached 70% of the total liquid level, stop the methanol pump 25, close the methanol inlet valve 9, and stop adding methanol. During the process of adding the methanol solution to the sodium methoxide feed metering tank 3, the added methanol solution will disturb the mixed solution in the sodium methoxide feed metering tank 3, thereby gradually mixing the sodium methoxide and methanol. The sampling valve 13 is opened and the sampling tube 12 is used to sample the primary mixed solution to analyze the concentration of sodium methoxide in the primary mixed solution. When the actual concentration of sodium methoxide reaches the preset concentration requirement, the sodium methoxide dilution solution is prepared.

[0018] Next, the addition flow rates of the sodium methoxide dilution and methanol are calculated based on the actual concentration of the sodium methoxide dilution and the expected sodium methoxide feed mass concentration (250ppm-270ppm). The sodium methoxide metering pump 4 is then started, the dilution feed valve 24 and the methanol feed valve 11 are opened, and the sodium methoxide dilution and methanol solution prepared in the sodium methoxide feed metering tank 3 are respectively passed through the tee pipe 6 and then enter the No. 1 pipeline mixer 7 for uniform mixing. The flow rates are then measured using the dilution flowmeter 28 and the methanol flowmeter 23. Simultaneously, the feed valve on the PTMEA feed line 8 is opened, allowing the PTMEA and the mixed solution, which has been uniformly mixed in the No. 1 pipeline mixer 7, to enter the No. 2 pipeline mixer 26 according to a set flow ratio. After uniform mixing, the PTMEA enters the alcoholysis reaction distillation tower 5 through the reaction distillation tower liquid phase feed line 27, thereby completing the feeding of sodium methoxide.

[0019] In this embodiment, the dilution ratio of sodium methoxide can be roughly controlled by using the liquid level sensor 15; then, the actual concentration of sodium methoxide can be accurately analyzed through sampling and analysis.

[0020] By providing two sodium methoxide feed metering tanks 3, when the first sodium methoxide feed metering tank 3 is normally feeding the alcoholysis reaction distillation tower 5, the second sodium methoxide feed metering tank 3 can be used to prepare the sodium methoxide dilution liquid; when the liquid level in the first sodium methoxide feed metering tank 3 drops to 10% of the total liquid level, the dilution liquid feed valve 24 of the first sodium methoxide feed metering tank 3 is closed, and the dilution liquid feed valve 24 of the second sodium methoxide feed metering tank 3 is opened, thereby switching the two sodium methoxide feed metering tanks 3, and the second sodium methoxide feed metering tank 3 is used to feed the alcoholysis reaction distillation tower 5, and the first sodium methoxide feed metering tank 3 starts to prepare the sodium methoxide dilution liquid; the two sodium methoxide feed metering tanks 3 are used in a reciprocating manner.

[0021] In the present embodiment, in order to prevent the methanol in the sodium methoxide feed metering tank 3 from volatilizing, nitrogen is introduced into the sodium methoxide feed metering tank 3 to maintain a slightly positive pressure in the sodium methoxide feed metering tank 3. When the pressure sensor 19 detects that the pressure in the sodium methoxide feed metering tank 3 reaches 15 kPa, the nitrogen valve 18 is closed and the nitrogen supply is stopped; when the pressure sensor 19 detects that the pressure in the sodium methoxide feed metering tank 3 reaches 20 kPa, the vent valve 20 is opened; when the pressure sensor 19 detects that the pressure in the sodium methoxide feed metering tank 3 is lower than 10 kPa, the nitrogen valve 18 is opened to continue to introduce nitrogen. At the same time, in order to prevent the high concentration of sodium methoxide stock solution from precipitating at low temperatures, an electric heating tape 21 is laid on the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3. When the temperature sensor 22 detects that the temperature of the sodium methoxide stock solution is lower than 30°C, the start switch of the electric heating tape 21 is activated. The electric heating tape 21 heats the pipeline connecting the sodium methoxide stock solution storage tank 2 and the sodium methoxide feed metering tank 3 at a fixed power to prevent the precipitation of sodium methoxide from clogging the pipeline and the filter 14. In addition, by providing two sodium methoxide metering pumps 4 in this embodiment, one can be used in backup mode to ensure continuous and stable operation of the system.

[0022] This embodiment can prevent the pipeline blockage or material shortage caused by the precipitation of sodium methoxide by diluting the sodium methoxide; at the same time, in order to ensure the original sodium methoxide feed amount, it is necessary to expand the delivery flow rate, which can solve the problem that the sodium methoxide delivery flow rate is too low and cannot be accurately measured or accurately controlled. It prevents the incomplete alcoholysis reaction caused by insufficient sodium methoxide addition, and can effectively reduce the waste caused by excessive addition of sodium methoxide, thereby avoiding the shortening of the regeneration cycle of the ion exchange resin in the later stage caused by excessive addition of sodium methoxide. By moving the intersection tee pipe 6 of the sodium methoxide and methanol solution to the outlet of the sodium methoxide metering pump 4, the distance of the sodium methoxide delivery pipeline is greatly shortened, and the time for the sodium methoxide to enter the alcoholysis reaction distillation tower is greatly shortened, thereby effectively reducing the time for the system to return to normal after the sodium methoxide is cut off. The present invention can improve the economic benefits of the factory, reduce the operating risks of personnel, and reduce the possibility of process accidents. Example 2: A method for feeding a sodium methoxide feeding system for preparing PTMEG by an alcoholysis reaction according to Example 1 comprises the following steps: (1) adding the sodium methoxide stock solution with a mass concentration of 30% in the sodium methoxide stock solution storage tank 2 and the methanol in the methanol storage tank 1 into the sodium methoxide feed metering tank 3 respectively, and diluting the sodium methoxide stock solution by 10 to 20 times with methanol to obtain a sodium methoxide diluted solution with a mass concentration of 1.5 to 3%; (2) mixing the sodium methoxide dilution obtained in step (1) with the methanol solution to obtain a primary mixed solution having a mass concentration of sodium methoxide of 840 ppm to 890 ppm; (3) The primary mixed solution obtained in step (2) is mixed with PTMEA to obtain a mixed solution having a mass concentration of sodium methoxide of 250 ppm to 270 ppm, and the mixed solution is then fed into the alcoholysis reaction distillation tower 5. In this embodiment, by diluting the 30% sodium methoxide stock solution to a concentration of 1.5 to 3%, sodium methoxide will not precipitate even at a temperature of -20°C in winter, effectively preventing the risk of pipeline blockage and material interruption.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction, characterized in that: Including methanol storage tank, methanol pump, sodium methoxide stock solution storage tank, sodium methoxide feed metering tank, sodium methoxide metering pump and alcoholysis reaction distillation tower; The outlet of the methanol storage tank is communicated with the inlet of the methanol pump, and the outlet of the methanol pump is communicated with the top inlet of the sodium methoxide feed metering tank; the outlet of the sodium methoxide stock solution storage tank is communicated with the bottom inlet of the sodium methoxide feed metering tank through a pipeline, the outlet of the sodium methoxide feed metering tank is communicated with the inlet of the sodium methoxide metering pump through a pipeline, and the outlet of the sodium methoxide metering pump is communicated with an inlet of a tee through a pipeline; the outlet of the methanol pump is also communicated with the other inlet of the tee through a pipeline, the outlet of the tee is communicated with the inlet of 1# pipeline mixer, the outlet of the 1# pipeline mixer and the outlet of the PTMEA feed pipeline are both communicated with the inlet of 2# pipeline mixer, and the outlet of the 2# pipeline mixer is communicated with the liquid phase feed port of the alcoholysis reaction distillation tower through a reaction distillation tower liquid phase feed pipeline; A methanol feed valve and a methanol flowmeter are provided on the pipeline connecting the methanol pump and the tee pipe; a diluent feed valve is provided at the outlet of the sodium methoxide feed metering tank; and a diluent flowmeter is provided on the pipeline connecting the sodium methoxide metering pump and the tee pipe; A methanol inlet valve is provided on the pipeline connecting the methanol pump and the sodium methoxide feed metering tank, and a sodium methoxide inlet valve is provided on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank.

2. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: A sampling port is provided at the outlet of the sodium methoxide feed metering tank, a sampling tube is screwed on the sampling port, and a sampling valve is also provided at the sampling port.

3. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: A filter is provided on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank.

4. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: The number of the sodium methoxide feed metering tanks is two, and the two sodium methoxide feed metering tanks are arranged in parallel.

5. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: There are two sodium methoxide metering pumps, and the two sodium methoxide metering pumps are arranged in parallel.

6. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: A liquid level sensor is provided in the sodium methoxide feed metering tank, and a signal output end of the liquid level sensor is signal-connected to a signal input end of a controller, and a signal output end of the controller is signal-connected to the signal input ends of the methanol inlet valve, the sodium methoxide inlet valve, and the diluent feed valve, respectively.

7. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: It also includes a nitrogen source, the outlet of the nitrogen source is connected to the air inlet of the sodium methoxide feed metering tank through a pipeline, and a nitrogen valve is provided at the outlet of the nitrogen source; a pressure sensor is provided in the sodium methoxide feed metering tank, a vent is opened at the top of the sodium methoxide feed metering tank, and a vent valve is provided at the vent; The signal output end of the pressure sensor is signal-connected to the signal input end of the controller, and the signal output end of the controller is signal-connected to the signal input ends of the nitrogen valve and the relief valve respectively.

8. The sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to claim 1, characterized in that: An electric heating tape is laid on the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank, and a temperature sensor is provided at the outlet of the pipeline connecting the sodium methoxide stock solution storage tank and the sodium methoxide feed metering tank; the signal output end of the temperature sensor is signal-connected to the signal input end of the controller, and the signal output end of the controller is signal-connected to the signal input end of the start / stop switch of the electric heating tape.

9. A method for feeding a sodium methoxide feeding system for preparing PTMEG by alcoholysis reaction according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) adding the sodium methoxide stock solution in the sodium methoxide stock solution storage tank and the methanol in the methanol storage tank into the sodium methoxide feed metering tank respectively, and diluting the sodium methoxide stock solution with methanol to obtain a sodium methoxide diluted solution; (2) mixing the sodium methoxide dilution obtained in step (1) with the methanol solution to obtain a primary mixed solution; (3) The initial mixed solution obtained in step (2) is mixed with PTMEA to obtain a mixed solution, and the mixed solution is fed into an alcoholysis reaction distillation tower.

10. The method for feeding sodium methoxide to prepare PTMEG by alcoholysis reaction according to claim 9, characterized in that: In the step (1), the mass concentration of sodium methoxide in the sodium methoxide dilution solution is 1.5-3%; in the step (2), the mass concentration of sodium methoxide in the initial mixed solution is 840ppm-890ppm; in the step (3), the mass concentration of sodium methoxide in the mixed solution is 250ppm-270ppm.

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