A durene feeding device and a feeding method

Abstract

The application discloses a durene feeding device and a feeding method, and belongs to the field of chemical technology. The feeding method comprises the following steps: (1) hot air enters from the bottom end of an absorption tower, and molten durene is pumped from the top end of the absorption tower, the upward hot air in the absorption tower is saturated by the downward molten durene; (2) the molten durene flowing out from the bottom end of the absorption tower enters a durene storage tank, and is pumped into the absorption tower by a feeding pump; (3) the saturated hot air flowing out from the top end of the absorption tower is branched into a gas chromatograph to analyze the content of durene in the saturated steam before entering a buffer tank; and (4) the saturated steam flowing out from the top end of the absorption tower enters the buffer tank, is mixed with another hot air, and the mixed gas is used as reaction gas of a single-tube reactor. The application realizes stable and adjustable durene feeding quantity in the range of 22-226 g / h, the concentration of durene in the reaction gas can be controlled in the range of 6.7-26.7 g / m 3 , and the demand of evaluating phthalic anhydride catalyst on the single-tube reactor is met.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a mesitylene feeding device and feeding method. Background Technology

[0002] Polyimide is one of the best-performing specialty materials, possessing excellent temperature resistance and superior mechanical, electrical, radiation, and solvent resistance properties. As a promising polymer material, it has been applied in high-temperature flame-retardant fibers and filter materials, components in the defense and aerospace industries, insulating materials for electronic devices, and flexible solar cell substrates. Its potential in functional materials continues to be explored. Pyromellitic dianhydride (PMDA) is the most commonly used diacid anhydride monomer for polyimide production. Hydrogenated pyromellitic dianhydride, using pyromellitic dianhydride as a raw material, is a crucial monomer for synthesizing high-end transparent polyimides. Therefore, the development of pyromellitic dianhydride production technology is one of the key factors for the development of the polyimide industry.

[0003] Currently, the industrial production technology for homohydric anhydride mainly uses mesitylene as a raw material, which is catalytically oxidized in air to produce homohydric anhydride in one step. Since this reaction is strongly exothermic and prone to deep oxidation, generating CO and CO2, developing homohydric anhydride catalysts with high yields at low temperatures is crucial. The development of homohydric anhydride catalysts requires scale-up evaluation in a single-tube reactor to examine the catalyst's reactivity, improve mass and heat transfer, effectively control the strong exothermic nature of the catalytic reaction, control the depth of selective oxidation, reduce deep oxidation reactions and reactions generating intermediate by-products, and achieve high efficiency in the reaction process. Mesitylene is solid at room temperature and requires molten feeding during the reaction; therefore, the single-tube reactor needs to be equipped with a high-temperature feed pump. Existing high-temperature feed pumps are mostly high-flow-rate pumps, with low-flow-rate high-temperature feed pumps being rare. Furthermore, low-flow-rate high-temperature feed pumps often experience problems such as pump check valve blockage and large flow fluctuations during use, easily causing catalyst overheating and making long-term stability evaluation of the homohydric anhydride catalyst impossible. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a mesitylene feeding device and feeding method.

[0005] The technical solution adopted in this invention is:

[0006] A mesitylene feeding device includes a first inlet pipe, a second inlet pipe, a mass flow meter A, an air heater A, an absorption tower, a mesitylene storage tank, a high-temperature feed pump, a gas chromatograph, an air heater B, a mass flow meter B, and a buffer tank.

[0007] The first air inlet pipe is connected to the inlet of air heater A, and a mass flow meter A is installed on the first air inlet pipe; the outlet of air heater A is connected to the air inlet at the bottom of the absorption tower; the liquid outlet at the bottom of the absorption tower is connected to the inlet of the mesitylene storage tank; the outlet of the mesitylene storage tank is connected to the circulating liquid inlet at the top of the absorption tower through a high-temperature feed pump; the air outlet at the top of the absorption tower is connected to the inlet of the buffer tank through pipe A; a branch pipe is installed on pipe A, and the branch pipe is connected to a gas chromatograph.

[0008] The second air inlet pipe is connected to the inlet of air heater B, and a mass flow meter B is installed on the second air inlet pipe; the outlet of air heater B is connected to the inlet of buffer tank through pipe B.

[0009] The outlet of the buffer tank is connected to a mixing gas pipe.

[0010] Furthermore, heat tracing pipes are installed on the inlet and outlet pipelines of the absorption tower, mesitylene storage tank, and buffer tank.

[0011] Furthermore, flow regulating valves are installed on both pipe A and pipe B.

[0012] Furthermore, the absorption tower is equipped with an insulation jacket, and the upper and lower ends of the insulation jacket are respectively equipped with a heat transfer oil outlet pipe and a heat transfer oil inlet pipe.

[0013] Furthermore, the absorption tower is equipped with packing material.

[0014] A method for feeding mesitylene specifically includes the following steps:

[0015] (1) After being measured by mass flow meter A, air A enters air heater A and is heated to become hot air A. Hot air A enters from the bottom of the absorption tower. Molten mesitylene in the mesitylene storage tank is pumped into the top of the absorption tower by a high-temperature feed pump. Inside the absorption tower, the upward hot air A is saturated by the downward molten mesitylene.

[0016] (2) Molten mesitylene flowing out from the bottom of the absorption tower enters the mesitylene storage tank and is then pumped back into the absorption tower by a high-temperature feed pump.

[0017] (3) The saturated steam flowing out from the top of the absorption tower enters the buffer tank through pipeline A, and at the same time enters the gas chromatograph through the branch pipe to analyze the content of mesitylene in the saturated steam.

[0018] (4) After being measured by mass flow meter B, air B enters air heater B and is heated to become hot air B. Hot air B and saturated steam flowing out from the top of the absorption tower enter the buffer tank together to form a mixed gas. The mixed gas is used as the reaction gas of the single tube reactor.

[0019] Further, in step (1), the temperature of hot air A is 85-120℃ and the flow rate is 200-500L / h; the temperature of molten tetramethylbenzene is 85-120℃; the mass-volume ratio of molten tetramethylbenzene to hot air A is 10:1-50:1g / L; and the heat preservation temperature of the absorption tower (8) is 85-120℃.

[0020] Furthermore, in step (2), the temperature of the mesitylene in the mesitylene storage tank is 85–120°C.

[0021] Furthermore, in step (3), the mass flow rate of mesitylene in the saturated vapor is 22–226 g / h.

[0022] Furthermore, in step (4), the temperature of the hot air B is 100–200°C, and the concentration of mesitylene in the mixed gas is 6.7–26.7 g / m³. 3 .

[0023] The beneficial effects of this invention are:

[0024] 1. This invention utilizes an absorption tower to saturately absorb mesitylene using hot air, thereby stably controlling the concentration of mesitylene in the saturated steam at the absorption tower outlet. Further mixing of this saturated steam with another stream of hot air maintains the mesitylene concentration in the reaction gas at 6.7–26.7 g / m³. 3 Within the specified range, it meets the requirements for evaluating homogenized anhydride catalysts on a single-tube reactor.

[0025] 2. By controlling the flow rate of hot air entering the absorption tower and the circulation rate of mesitylene, this invention can achieve stable low-flow feed in a single-tube reactor, making the mesitylene feed rate stable and adjustable within the range of 22 to 226 g / h.

[0026] 3. The feeding device of the present invention has a simple process and is easy to control. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the mesitylene feeding device of the present invention.

[0028] Figure 2 This is a process flow diagram of the mesitylene feeding method of the present invention. Attached image description:

[0030] 1-Mass flow meter A; 2-Air heater A; 3-Heat tracing tape; 4-Mesitylene storage tank; 5-High temperature feed pump; 6-Heat transfer oil inlet; 7-Heat transfer oil outlet; 8-Vaporization tower; 9-Gas chromatograph; 10-Air heater B; 11-Mass flow meter B; 12-Buffer tank. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and a preferred embodiment.

[0032] Example 1

[0033] See Figure 1 This embodiment provides a mesitylene feeding device, including a first air inlet pipe 101, a second air inlet pipe 102, a mass flow meter A1, an air heater A2, an absorption tower 3, a mesitylene storage tank 4, a high-temperature feed pump 5, a gas chromatograph 9, an air heater B10, a mass flow meter B11, and a buffer tank 12.

[0034] The first air inlet pipe 101 is connected to the inlet of the air heater A1, and a mass flow meter A1 is installed on the first air inlet pipe 101; the outlet of the air heater A2 is connected to the air inlet at the lower end of the absorption tower 8, the liquid outlet at the bottom of the absorption tower 8 is connected to the inlet of the mesitylene storage tank 4, the outlet of the mesitylene storage tank 4 is connected to the circulating liquid inlet at the upper end of the absorption tower 8 through the high temperature feed pump 5, and the air outlet at the top of the absorption tower 8 is connected to the inlet of the buffer tank 12 through the pipe A104, and a branch pipe 105 is provided on the pipe A104, which is connected to the gas chromatograph 9;

[0035] The second air inlet pipe 102 is connected to the inlet of the air heater B11, and a mass flow meter B11 is installed on the second air inlet pipe 102; the outlet of the air heater B10 is connected to the inlet of the buffer tank 12 through the pipe B106; the outlet of the buffer tank 12 is connected to the mixing pipe 103.

[0036] Flow regulating valves are installed on pipes A104 and B106 respectively to facilitate the adjustment of the flow rate of saturated steam entering buffer tank 12 and the flow rate of hot air B; a flow regulating valve is installed on branch pipe 105 to facilitate the adjustment of the flow rate of saturated steam entering gas chromatograph 9.

[0037] The absorption tower 8 is a packed tower, and the packing is preferably at least one of Pall rings, rectangular saddle rings, Raschig rings, stepped rings, flat rings, perforated corrugated packing, calendered perforated ring packing, and wire mesh packing. The theoretical number of plates in the absorption tower 8 is 30 to 70. The shell of the absorption tower 8 is equipped with a heat-insulating jacket 81, and the upper and lower ends of the heat-insulating jacket 81 are respectively provided with a heat transfer oil outlet pipe 7 and a heat transfer oil inlet pipe 6. By circulating heat transfer oil through the heat-insulating jacket 81, the insulation temperature of the absorption tower 8 is controlled within a set range.

[0038] The inlet and outlet pipelines of the absorption tower 8, the mesitylene storage tank 4, and the buffer tank 12 are all equipped with heat tracing pipes 3. The heat tracing temperature of the heat tracing pipes 3 is 85-120℃. By installing heat tracing pipes, the heat loss of hot air and mesitylene raw material can be reduced.

[0039] Example 2

[0040] See Figure 2 This embodiment provides a method for feeding mesitylene using the feeding device described in Embodiment 1. The specific steps include:

[0041] (1) After being metered by mass flow meter A1, air A enters air heater A2 at a flow rate of 200 L / h and is heated to 120°C. Hot air A enters from the bottom of absorption tower 8. Mesotriene is heated to 120°C and melted in mesotriene storage tank 4. Molten mesotriene is pumped into absorption tower 8 from the top of absorption tower 8 via feed pump 5 at a flow rate of 10 kg / h. The mass-volume ratio of molten mesotriene to hot air A is 50:1 g / L. The hot air rising in absorption tower 8 is saturated by the molten mesotriene falling in.

[0042] (2) The molten mesitylene flowing out from the bottom of the absorption tower 8 enters the mesitylene storage tank 4 and is then pumped back into the absorption tower 8 by the feed pump 5.

[0043] (3) The saturated vapor flowing out from the top of the absorption tower 8 enters the gas chromatograph 9 via a branch before entering the buffer tank 12. The mass flow rate of mesitylene in the saturated vapor is 89 g / h.

[0044] (4) Another stream of air, B, is measured by mass flow meter B11 and then flows at a rate of 3.13m³. 3 The hot air (B) enters the air heater B10 at a flow rate of / h and is heated to 200℃. This hot air, along with the saturated steam flowing from the top of the absorber tower 8, enters the buffer tank 12. The resulting mixture serves as the reaction gas in the single-tube reactor, with a mesitylene concentration of 26.7 g / m³. 3 .

[0045] The theoretical number of plates in absorption tower 8 is 50, the insulation temperature of absorption tower 8 is 120℃, and the heat tracing temperature of heat tracing pipeline 3 is 120℃.

[0046] Example 3

[0047] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0048] Air A enters air heater A at a flow rate of 200 L / h and is heated to 85°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 85°C, and the theoretical number of plates in absorption tower 8 is 64.

[0049] Mesitylene is heated to 85°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 2 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 10:1 g / L.

[0050] The mass flow rate of mesitylene in saturated vapor is 22 g / h.

[0051] Air B at 3.08m 3 The air enters air heater B at a flow rate of / h and is heated to 100°C before entering the buffer tank;

[0052] The concentration of mesitylene in the gas mixture was 6.7 g / m³. 3 .

[0053] The heat tracing temperature of heat tracing pipeline 3 is 85℃.

[0054] Example 4

[0055] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0056] Air A enters air heater A at a flow rate of 500 L / h and is heated to 85°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 85°C, and the theoretical number of plates in absorption tower 8 is 70.

[0057] Mesitylene is heated to 85°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 5 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 10:1 g / L.

[0058] The mass flow rate of mesitylene in saturated vapor is 56 g / h.

[0059] Air B at 5m 3 The air enters air heater B at a flow rate of / h and is heated to 100°C before entering the buffer tank;

[0060] The concentration of mesitylene in the gas mixture was 10.2 g / m³. 3 .

[0061] The heat tracing temperature of heat tracing pipeline 3 is 85℃.

[0062] Example 5

[0063] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0064] Air A enters air heater A at a flow rate of 500 L / h and is heated to 120°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 120°C, and the theoretical number of plates in absorption tower 8 is 30.

[0065] Mesitylene is heated to 120°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 25 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 50:1 g / L.

[0066] The mass flow rate of mesitylene in saturated vapor is 226 g / h.

[0067] Air B at 7.96m 3 The air enters air heater B at a flow rate of / h and is heated to 200℃ before entering the buffer tank;

[0068] The concentration of mesitylene in the gas mixture was 26.7 g / m³. 3 .

[0069] The heat tracing temperature of heat tracing pipeline 3 is 120℃.

[0070] Example 6

[0071] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0072] Air A enters air heater A at a flow rate of 500 L / h and is heated to 110°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 110°C, and the theoretical number of plates in absorption tower 8 is 47.

[0073] Mesitylene is heated to 110°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 10 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 20:1 g / L.

[0074] The mass flow rate of mesitylene in saturated vapor is 156 g / h.

[0075] Air B at 6.23m 3 The air enters air heater B at a flow rate of / h and is heated to 180°C before entering the buffer tank.

[0076] The concentration of mesitylene in the gas mixture was 23.2 g / m³. 3 .

[0077] The heat tracing temperature of heat tracing pipeline 3 is 110℃.

[0078] Example 7

[0079] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0080] Air A enters air heater A at a flow rate of 500 L / h and is heated to 100°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 100°C, and the theoretical number of plates in absorption tower 8 is 50.

[0081] Mesitylene is heated to 100°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 10 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 20:1 g / L.

[0082] The mass flow rate of mesitylene in saturated vapor is 105 g / h.

[0083] Air B at 7.5m 3 The air enters air heater B at a flow rate of / h and is heated to 170°C before entering the buffer tank.

[0084] The concentration of mesitylene in the gas mixture was 13.1 g / m³. 3 .

[0085] The heat tracing temperature of heat tracing pipeline 3 is 100℃.

[0086] Example 8

[0087] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0088] Air A enters air heater A at a flow rate of 500 L / h and is heated to 90°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 90°C, and the theoretical number of plates in absorption tower 8 is 63.

[0089] Mesitylene is heated to 90°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 10 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 20:1 g / L.

[0090] The mass flow rate of mesitylene in saturated vapor is 70 g / h.

[0091] Air B at 5.3m 3 The air enters air heater B at a flow rate of / h and is heated to 130°C before entering the buffer tank;

[0092] The concentration of mesitylene in the gas mixture was 12.1 g / m³. 3 .

[0093] The heat tracing temperature of heat tracing pipeline 3 is 90℃.

[0094] Example 9

[0095] This embodiment provides a method for feeding mesitylene, the process steps of which are the same as in Embodiment 1, except that:

[0096] Air A enters air heater A at a flow rate of 500 L / h and is heated to 85°C before entering absorption tower 8. The insulation temperature of absorption tower 8 is 85°C, and the theoretical number of plates in absorption tower 8 is 58.

[0097] Mesitylene is heated to 85°C and melted in the storage tank. The molten mesitylene is pumped into the absorption tower 8 at a flow rate of 10 kg / h. The mass-to-volume ratio of molten mesitylene to hot air A is 20:1 g / L.

[0098] The mass flow rate of mesitylene in saturated vapor is 56 g / h.

[0099] Air B at 4.1m 3 The air enters air heater B at a flow rate of / h and is heated to 110°C before entering the buffer tank;

[0100] The concentration of mesitylene in the gas mixture was 12.2 g / m³. 3 .

[0101] The heat tracing temperature of heat tracing pipeline 3 is 85℃.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A mesitylene feeding device, characterized in that, It includes a first air inlet pipe (101), a second air inlet pipe (102), a mass flow meter A (1), an air heater A (2), an absorption tower (8), a mesitylene storage tank (4), a high-temperature feed pump (5), a gas chromatograph (9), an air heater B (10), a mass flow meter B (11), and a buffer tank (12); The first air inlet pipe (101) is connected to the inlet of the air heater A (2), and a mass flow meter A (1) is installed on the first air inlet pipe (101); the outlet of the air heater A (2) is connected to the lower air inlet of the absorption tower (8), the bottom liquid outlet of the absorption tower (8) is connected to the inlet of the mesitylene storage tank (4), the outlet of the mesitylene storage tank (4) is connected to the upper circulating liquid inlet of the absorption tower (8) through the high temperature feed pump (5), and the top air outlet of the absorption tower (8) is connected to the inlet of the buffer tank (12) through the pipe A (104). A branch pipe (105) is installed on the pipe A (104), and the branch pipe (105) is connected to the gas chromatograph (9); The second air inlet pipe (102) is connected to the inlet of the air heater B (10), and a mass flow meter B (11) is installed on the second air inlet pipe (102); the outlet of the air heater B (10) is connected to the inlet of the buffer tank (12) through the pipe B (106); The outlet of the buffer tank (12) is connected to a mixing gas pipe (103).

2. The mesitylene feeding device according to claim 1, characterized in that, The inlet and outlet pipelines of the absorption tower (8), the mesitylene storage tank (4) and the buffer tank (12) are all equipped with heat tracing pipes (3).

3. The mesitylene feeding device according to claim 1, characterized in that, Flow regulating valves are installed on pipes A (104) and B (106).

4. The mesitylene feeding device according to claim 1, characterized in that, The absorption tower (8) is equipped with a heat insulation jacket (81), and the upper and lower ends of the heat insulation jacket (81) are respectively equipped with a heat transfer oil outlet pipe (7) and a heat transfer oil inlet pipe (6).

5. The mesitylene feeding device according to claim 1, characterized in that, The absorption tower (8) is equipped with packing (82), and the theoretical number of plates in the absorption tower (8) is 30 to 70.

6. A method for feeding mesitylene, characterized in that, Specifically, the following steps are included: (1) After being measured by mass flow meter A (1), air A enters air heater A (2) and is heated into hot air A. Hot air A enters from the lower end of the absorption tower (8). Molten mesitylene in the mesitylene storage tank (4) is pumped from the upper end of the absorption tower (8) by high temperature feed pump (5). In the absorption tower (8), the upward hot air A is saturated by the downward molten mesitylene. (2) The molten mesitylene flowing out from the bottom of the absorption tower (8) enters the mesitylene storage tank (4) and is then pumped back into the absorption tower (8) by the high-temperature feed pump (5); (3) The saturated steam flowing out from the top of the absorption tower (8) enters the buffer tank (12) through pipe A (104), and at the same time enters the gas chromatograph (9) through the branch pipe (105) to analyze the content of mesitylene in the saturated steam. (4) After being measured by mass flow meter B (11), air B enters air heater B (10) and is heated into hot air B. Hot air B and saturated steam flowing out from the top of absorption tower (8) enter buffer tank (12) together to form mixed gas. Mixed gas is used as reaction gas in single tube reactor.

7. A method for feeding mesitylene according to claim 6, characterized in that, In step (1), the temperature of hot air A is 85-120℃ and the flow rate is 200-500L / h; the temperature of molten tetramethylbenzene is 85-120℃; the mass-volume ratio of molten tetramethylbenzene to hot air A is 10:1-50:1g / L; and the heat preservation temperature of the absorption tower (8) is 85-120℃.

8. A method for feeding mesitylene according to claim 6, characterized in that, In step (2), the temperature of the mesitylene in the mesitylene storage tank is 85-120℃.

9. A method for feeding mesitylene according to claim 6, characterized in that, In step (3), the mass flow rate of mesitylene in the saturated vapor is 22-226 g / h.

10. A method for feeding mesitylene according to claim 6, characterized in that, In step (4), the temperature of hot air B is 100–200°C, and the concentration of mesitylene in the mixed gas is 6.7–26.7 g / m³. 3 .

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