Production method of ethyl maltol

Abstract

The invention relates to the technical field of organic synthesis, in particular to a production method of ethyl maltol. The production method comprises the following steps: respectively mixing toluene and tetrahydrofuran at a flow rate of 1200-2500mL / min and a flow rate of 400-1000mL / min, then adding magnesium chips and chloroethane to react to obtain a Grignard reagent, mixing the Grignard reagent with furfural, and carrying out an addition reaction to obtain an addition reagent; the method comprises the following steps: mixing an addition reagent and a magnesium chloride solution, carrying out hydrolysis reaction to obtain a furfuryl propanol mixed solution and basic magnesium chloride, and carrying out reduced pressure distillation on the furfuryl propanol mixed solution to obtain furfuryl propanol; the feeding rate of the magnesium chips is 80-150g / min, and the feeding rate of the chloroethane is 280-650g / min. By accurately controlling the adding rate of the materials, the purity and the yield of the intermediate product furfuryl propanol are remarkably improved, so that the purity and the yield of the final product ethyl maltol are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and particularly relates to a production method of ethyl maltol. Background Art

[0002] Ethyl maltol is an ideal food additive that is safe, non-toxic, widely used, has good effects, and requires extremely small amounts. It is widely used in food, medicine, cigarettes, cosmetics, light-sensitive materials, etc. It has a significant effect on improving and enhancing the fragrance of food, and has antibacterial and anti-corrosion properties, which can extend the storage period of food.

[0003] The synthesis methods of ethyl maltol include total synthesis method, semi-synthesis method, pyromellitic acid method, furfural method, electrolytic oxidation method, organic closed-loop method, etc. Among them, the furfural method synthesis process has the advantages of easily available raw materials, low cost, and less three wastes, so it is widely used and is easy to realize industrial production.

[0004] However, the steps of Grignard, addition, and hydrolysis reactions require a relatively long time, wasting time and energy consumption. Developing an industrial production method of ethyl maltol with simple operation, high yield, purity, and safety is an urgent problem to be solved at present. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a production method of ethyl maltol, which can improve the purity and yield of the intermediate furfuryl propanol, thereby improving the purity and yield of the final product ethyl maltol.

[0006] To this end, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a production method of ethyl maltol in an optional embodiment, including the following steps:

[0008] S1: Toluene and tetrahydrofuran are mixed at a flow rate of 1200 - 2500 mL / min and 400 - 1000 mL / min respectively, then magnesium chips and chloroethane are added, and a Grignard reaction is carried out to obtain a Grignard reagent. Then, the Grignard reagent and furfural are mixed to carry out an addition reaction to obtain an addition reagent;

[0009] S2: The addition reagent and magnesium chloride solution are mixed to carry out a hydrolysis reaction to obtain a furfuryl propanol mixed solution and basic magnesium chloride. The furfuryl propanol mixed solution is subjected to vacuum distillation to obtain furfuryl propanol, and finally a chlorination reaction and a chlorination hydrolysis reaction are carried out to obtain ethyl maltol;

[0010] Among them, the feeding rate of the magnesium chips is 80 - 150 g / min, and the feeding rate of the chloroethane is 280 - 650 g / min.

[0011] In the present invention, the reaction equation for preparing ethyl maltol is as follows:

[0012]

[0013] Preferably, when mixing the Grignard reagent and furfural, the flow rate of the Grignard reagent is 200 - 1200 mL / min, and the flow rate of furfural is 200 - 350 mL / min; or, the flow rate of the Grignard reagent is 1600 - 2000 mL / min, and the flow rate of furfural is 400 - 2000 mL / min.

[0014] Preferably, when mixing the addition reagent and magnesium chloride solution, the flow rate of the addition reagent is 1000 - 3000 mL / min, and the flow rate of the magnesium chloride solution is 520 - 1000 mL / min; and / or, the concentration of the magnesium chloride solution is 0.5 - 1.2 mol / L. The volume ratio of toluene to tetrahydrofuran is 3:1; and / or, the temperature of the Grignard reaction is 81 - 100 °C, and the time is 2.5 - 3.5 hours.

[0015] In the present invention, the materials need to be initiated before the Grignard reaction, and the initiation temperature is 60 - 80 °C.

[0016] Preferably, the reaction temperature of the addition reaction is below 35 °C, and the time is 3.5 - 4.5 hours; and / or, the reaction temperature of the hydrolysis reaction is below 30 °C, and the time is 2.5 - 3.5 hours. The temperature of the vacuum distillation is 60 - 65 °C, and the time is 5.5 - 6.5 hours; and / or, the pressure of the vacuum distillation is below -0.095 MPa. The index for the end of the vacuum distillation is: when the content of furfuryl alcohol in the mixed solution ≥ 95%, and the content of toluene and tetrahydrofuran ≤ 2.0%, and the content of furfural ≤ 1.5%, the vacuum distillation ends. The toluene and tetrahydrofuran separated by the vacuum distillation are recycled and used continuously in the Grignard reaction.

[0017] Preferably, the chlorination reaction includes the following steps: After mixing furfuryl alcohol and methanol aqueous solution, adjust the temperature to below -18 °C, and introduce chlorine gas for reaction to obtain a chlorination reagent; the reaction temperature is (-12) - (-10) °C, and the time is 4 - 5 hours, and the mass fraction of methanol in the methanol aqueous solution is 59 - 61%.

[0018] Preferably, the chlorination hydrolysis reaction comprises the following steps: distilling the chlorination reagent, then dropping an alkaline solution to adjust the pH to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution, cooling and crystallizing the yellow aqueous solution, filtering to obtain a first crude product, distilling and sublimating the black oil to obtain a second crude product and pitch, and recrystallizing and purifying the first crude product and the second crude product; the distillation temperature is 92 - 95 °C and the time is 2 - 3 hours; before dropping the alkaline solution, the temperature is lowered to 62 - 68 °C; the alkaline solution is selected from one or more of an aqueous ammonia solution with a concentration of 25%, a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution, and a potassium carbonate solution.

[0019] Preferably, the yield of the furfuryl propanol ≥ 84%, and the purity ≥ 94.5%.

[0020] Furthermore, toluene and tetrahydrofuran solvents are introduced into a rotary tube reactor, magnesium chips and chloroethane are added, and a Grignard reaction is carried out. The outflow solution is completely reacted in a microchannel reactor to obtain a Grignard reagent. The Grignard reagent and furfural are respectively pumped into a continuous flow microchannel reactor by metering pumps to carry out an addition reaction to obtain an addition reagent, and the utilization rate of the Grignard reagent can reach 100%. The outflowing addition reagent is pumped into the rotary tube reactor, and at the same time, a magnesium chloride solution is pumped in to carry out a hydrolysis reaction to produce a furfuryl propanol mixed solution and basic magnesium chloride. The furfuryl propanol mixed solution is subjected to vacuum distillation in a vacuum kettle to distill out furfuryl propanol.

[0021] The materials of the rotary tube reactor and the microchannel reactor are babbit metal.

[0022] In the present invention, babbit metal not only has excellent corrosion resistance to various acids at different temperatures, but also has good heat transfer and pressure resistance properties, and the maximum tolerable pressure reaches 2.0 - 2.5 MPa. By defining the materials of the rotary tube reactor and the microchannel reactor as babbit metal, the safety of the reaction can be effectively guaranteed. In addition, the cost of babbit metal is moderate and is suitable for industrial production and promotion.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. By precisely controlling the feeding rate, reaction time, and temperature of the materials, the present invention significantly improves the purity and yield of the intermediate furfuryl propanol, thereby improving the purity and yield of the final product ethyl maltol.

[0025] 2. By using a combination of two reactors, the present invention not only solves the problem that the microchannel reactor is prone to blockage when there are solids in the reaction system, but also increases the mass transfer effect and reaction efficiency and shortens the reaction time.

[0026] 3. The present invention adopts a fully automated operation process, which is simple to operate, easy to control, has high safety, and is suitable for industrial continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 It is the gas chromatogram of furfuryl alcohol prepared in Example 1 of the present invention;

[0029] Figure 2 It is the gas chromatogram of furfuryl alcohol prepared in Example 4 of the present invention;

[0030] Figure 3 It is the gas chromatogram of furfuryl alcohol prepared in Comparative Example 4 of the present invention;

[0031] Figure 4 It is the gas chromatogram of furfuryl alcohol prepared in Comparative Example 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following will further elaborate on the present invention in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] For those steps or conditions not specified in the examples, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments not specified by the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0034] In the following examples and comparative examples, a rotary cutting tube reactor and a microchannel reactor of model VMRHS2600 are used.

[0035] The following will further elaborate on the technical method of the present invention in the form of examples.

[0036] Example 1

[0037] This example provides a production method of ethyl maltol, including the following steps:

[0038] Step 1: Grignard reaction

[0039] Use a metering pump to pump toluene and tetrahydrofuran into the first tubular rotary reactor respectively. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain Grignard reagent.

[0040] Step 2: Addition reaction

[0041] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous-flow microchannel reactor using a metering pump. Control the reaction temperature between 28 °C and 32 °C. Control the flow rate of the Grignard reagent at 1200 mL / min and the flow rate of furfural at 280 mL / min to make the reaction proceed for 4 hours to obtain an addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0042] Step 3: Hydrolysis reaction

[0043] Pump the flowing-out addition reagent into the second rotary tubular reactor using a metering pump, control the flow rate at 2000 mL / min, and simultaneously pump in an aqueous magnesium chloride solution (1.07 mol / L) at a certain ratio, with a flow rate of 555 mL / min. Control the temperature at 26 °C - 28 °C to make the reaction proceed for 3 hours under normal pressure, and the produced material is a mixed solution of furfuryl alcohol and basic magnesium chloride.

[0044] Step 4: Vacuum distillation

[0045] The mixed solution of furfuryl alcohol is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. Control the distillation temperature at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran for subsequent recovery and reuse; continue distillation, control the end temperature to be less than 90 °C, take samples for detection, and when the content of furfuryl alcohol ≥ 95%, the content of toluene and tetrahydrofuran solvents ≤ 2.0%, and the content of furfural ≤ 1.5%, the distillation reaction ends.

[0046] Step 5: Chlorination reaction

[0047] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a mixed solution of furfuryl alcohol - methanol. When controlling the temperature of the reaction kettle to drop below -18 °C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorination reagent;

[0048] Step 6: Chlorination hydrolysis reaction

[0049] The obtained chlorinating reagent is pumped into the chlorination hydrolysis kettle, and methanol is distilled out under positive pressure. The distillation time is 2.5 hours and the temperature is 92 °C. Then, the temperature is lowered to 65 °C, and an aqueous ammonia solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5, obtaining black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, and filtered to obtain the first crude product. The black oil is distilled and sublimated to obtain the second crude product and pitch. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0050] Example 2

[0051] This example provides a production method of ethyl maltol, including the following steps:

[0052] Step 1: Grignard reaction

[0053] Toluene and tetrahydrofuran are respectively pumped into the first tubular rotary cutter reactor using metering pumps. The flow rate of toluene is 2000 mL / min, and the flow rate of tetrahydrofuran is 667 mL / min. Magnesium chips and chloroethane are added to react. The feeding rate of magnesium chips is 180 g / min, and the feeding rate of chloroethane is 650 g / min. The initiation temperature is controlled at 60 - 65 °C, and the reaction temperature is 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain the Grignard reagent.

[0054] Step 2: Addition reaction

[0055] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. The reaction temperature is controlled between 28 °C - 32 °C. The flow rate of the Grignard reagent is controlled at 1200 mL / min, and the flow rate of furfural is 280 mL / min, so that the reaction proceeds for 4 hours to obtain the addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0056] Step 3: Hydrolysis reaction

[0057] The flowing out addition reagent is pumped into the second rotary cutter tubular reactor using a metering pump, and the flow rate is controlled at 2000 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in at a certain ratio simultaneously, and its flow rate is 555 mL / min. The temperature is controlled at 26 °C - 28 °C, so that the reaction proceeds for 3 hours under normal pressure, and the produced material is a furfuryl propanol mixed solution and basic magnesium chloride.

[0058] Step 4: Vacuum distillation

[0059] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum still for 6 hours, with the negative pressure below -0.095 MPa, and the distillation temperature is controlled at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran, which is recycled for subsequent use; continue distillation, control the end temperature to be less than 90 °C, take samples for detection, and when the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0060] Step Five: Chlorination Reaction

[0061] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorination reagent.

[0062] Step Six: Chlorination Hydrolysis Reaction

[0063] Pump the obtained chlorination reagent into a chlorination hydrolysis kettle, distill out methanol under positive pressure for 2.5 hours at a temperature of 92 °C, then cool down to 65 °C, add an aqueous ammonia solution with a concentration of 25% to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. Cool and crystallize the yellow aqueous solution, filter to obtain the first crude product, distill and sublime the black oil to obtain the second crude product and pitch, and recrystallize and purify the first crude product and the second crude product to obtain ethyl maltol.

[0064] Example 3

[0065] This example provides a method for producing ethyl maltol, including the following steps:

[0066] Step 1: Grignard Reaction

[0067] Use metering pumps to pump toluene and tetrahydrofuran into the first tubular rotary cutter reactor respectively. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain a Grignard reagent.

[0068] Step Two: Addition Reaction

[0069] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into a second continuous-flow microchannel reactor using metering pumps. The reaction temperature is controlled between 28°C and 32°C. The flow rate of the Grignard reagent is controlled at 650 mL / min, and the flow rate of furfural is 280 mL / min, allowing the reaction to proceed for 4 hours to obtain an addition reagent, with the utilization rate of the Grignard reagent reaching 100%.

[0070] Step 3: Hydrolysis reaction

[0071] The outflowing addition reagent is pumped into a second rotary tube reactor using a metering pump, controlling the flow rate at 2500 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in at a certain ratio simultaneously, with a flow rate of 555 mL / min. The temperature is controlled at 26°C - 28°C, allowing the reaction to proceed for 3 hours under atmospheric pressure, and the resulting material is a furfuryl alcohol mixed solution and basic magnesium chloride.

[0072] Step 4: Vacuum distillation

[0073] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. The distillation temperature is controlled at 60 - 65°C to separate out the toluene and tetrahydrofuran mixed solvent, which is recycled for subsequent use. Continuing the distillation, controlling the end point temperature to be less than 90°C, sampling and testing. When the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0074] Step 5: Chlorination reaction

[0075] Methanol aqueous solution (mass fraction of methanol is 60%) is added to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle is controlled to drop below -18°C, chlorine gas is introduced for reaction for 4.5 hours, and the reaction temperature is controlled at -10°C to obtain a chlorination reagent.

[0076] Step 6: Chlorination hydrolysis reaction

[0077] The obtained chlorination reagent is pumped into a chlorination hydrolysis kettle, and methanol is distilled out under positive pressure for 2.5 hours at a temperature of 92°C. Then the temperature is lowered to 65°C, and an aqueous ammonia solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, filtered to obtain a first crude product. The black oil is distilled and sublimated to obtain a second crude product and pitch. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0078] Example 4

[0079] This example provides a method for producing ethyl maltol, including the following steps:

[0080] Step 1: Format Reaction

[0081] Use metering pumps to pump toluene and tetrahydrofuran into the first tubular rotary cutter reactor respectively. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain Grignard reagent.

[0082] Step 2: Addition Reaction

[0083] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. Control the reaction temperature between 28 °C - 32 °C, control the flow rate of the Grignard reagent at 1800 mL / min, and the flow rate of furfural at 630 mL / min, and make the reaction proceed for 4 hours to obtain an addition reagent. The utilization rate of the Grignard reagent can reach 100%.

[0084] Step 3: Hydrolysis Reaction

[0085] Pump the flowing out addition reagent into the second rotary cutter tubular reactor using a metering pump, control the flow rate at 2800 mL / min, and simultaneously pump in an aqueous magnesium chloride solution (1.07 mol / L) at a certain ratio, with a flow rate of 782 mL / min. Control the temperature at 26 °C - 28 °C, and make the reaction proceed for 3 hours under normal pressure to produce a mixed solution of furfuryl alcohol and basic magnesium chloride.

[0086] Step 4: Vacuum Distillation

[0087] The mixed solution of furfuryl alcohol is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. Control the distillation temperature at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran for subsequent recovery and reuse; continue distillation, control the end point temperature to be less than 90 °C, take samples for detection. When the content of furfuryl alcohol ≥ 95%, the content of toluene and tetrahydrofuran solvents ≤ 2.0%, and the content of furfural ≤ 1.5%, the distillation reaction ends.

[0088] Step 5: Chlorination Reaction

[0089] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a mixed solution of furfuryl alcohol - methanol. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorination reagent;

[0090] Step 6: Chlorination Hydrolysis Reaction

[0091] The obtained chlorinating reagent is pumped into the chlorination hydrolysis kettle, and methanol is distilled out under positive pressure. The distillation time is 2.5 hours and the temperature is 92 °C. Then, the temperature is lowered to 65 °C, and an ammonia water solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5, obtaining black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, and then filtered to obtain the first crude product. The black oil is distilled and sublimated to obtain the second crude product and pitch. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0092] Example 5

[0093] This example provides a production method of ethyl maltol, which includes the following steps:

[0094] Step 1: Grignard reaction

[0095] Toluene and tetrahydrofuran are respectively pumped into the first tubular rotary cutter reactor using metering pumps. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Magnesium chips and chloroethane are added to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. The initiation temperature is controlled at 60 - 65 °C, and the reaction temperature is 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain the Grignard reagent.

[0096] Step 2: Addition reaction

[0097] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. The reaction temperature is controlled between 28 °C and 32 °C. The flow rate of the Grignard reagent is controlled at 1200 mL / min, and the flow rate of furfural is 280 mL / min, allowing the reaction to proceed for 4 hours to obtain the addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0098] Step 3: Hydrolysis reaction

[0099] The flowing out addition reagent is pumped into the second rotary cutter tubular reactor using a metering pump, and the flow rate is controlled at 2000 mL / min. An aqueous magnesium chloride solution (0.8 mol / L) is pumped in at a certain ratio simultaneously, and its flow rate is 555 mL / min. The temperature is controlled at 26 °C - 28 °C, allowing the reaction to proceed for 3 hours under normal pressure, and the output materials are a furfuryl propanol mixed solution and basic magnesium chloride.

[0100] Step 4: Vacuum distillation

[0101] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum still for 6 hours under a negative pressure below -0.095 MPa, and the distillation temperature is controlled at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran, which is then recycled for subsequent use; continue distillation, control the end temperature to be less than 90 °C, take samples for detection, and when the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0102] Step Five: Chlorination Reaction

[0103] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorination reagent.

[0104] Step Six: Chlorination Hydrolysis Reaction

[0105] Pump the obtained chlorination reagent into a chlorination hydrolysis kettle, distill out methanol under positive pressure for 2.5 hours at a temperature of 92 °C, then cool down to 65 °C, add an aqueous ammonia solution with a concentration of 25% to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. Cool and crystallize the yellow aqueous solution, filter to obtain the first crude product, distill and sublime the black oil to obtain the second crude product and pitch, and recrystallize and purify the first crude product and the second crude product to obtain ethyl maltol.

[0106] Example 6

[0107] This example provides a method for producing ethyl maltol, which includes the following steps:

[0108] Step 1: Grignard Reaction

[0109] Use a metering pump to pump toluene and tetrahydrofuran into the first tubular rotary cutter reactor respectively. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 90 - 95 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor to fully react to obtain a Grignard reagent.

[0110] Step Two: Addition Reaction

[0111] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into a second continuous flow microchannel reactor using metering pumps. The reaction temperature is controlled between 10°C and 20°C. The flow rate of the Grignard reagent is controlled at 1200 mL / min, and the flow rate of furfural is 280 mL / min, allowing the reaction to proceed for 4 hours to obtain an addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0112] Step Three: Hydrolysis Reaction

[0113] The outflowing addition reagent is pumped into a second rotary cutting tube reactor using a metering pump, with the flow rate controlled at 2000 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in simultaneously at a certain ratio, with a flow rate of 555 mL / min. The temperature is controlled between 10°C and 20°C, allowing the reaction to proceed for 3 hours under atmospheric pressure, and the resulting material is a furfuryl alcohol mixed solution and basic magnesium chloride.

[0114] Step Four: Vacuum Distillation

[0115] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. The distillation temperature is controlled at 60 - 65°C to separate out the toluene and tetrahydrofuran mixed solvent, which is recycled for subsequent use; continue distillation, control the end point temperature to be less than 90°C, take samples for testing. When the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0116] Step Five: Chlorination Reaction

[0117] Methanol aqueous solution (mass fraction of methanol is 60%) is added to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18°C, chlorine gas is introduced for reaction for 4.5 hours, and the reaction temperature is controlled at -10°C to obtain a chlorination reagent;

[0118] Step Six: Chlorination Hydrolysis Reaction

[0119] The obtained chlorination reagent is pumped into a chlorination hydrolysis kettle, and methanol is distilled out under positive pressure for 2.5 hours at a temperature of 92°C. Then the temperature is lowered to 65°C, and an ammonia aqueous solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5, obtaining black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, filtered to obtain a first crude product, and the black oil is distilled and sublimated to obtain a second crude product and asphalt. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0120] Comparative Example 1

[0121] This comparative example provides a method for producing ethyl maltol, including the following steps:

[0122] Step 1: Format reaction

[0123] Use metering pumps to pump toluene and tetrahydrofuran into the first tubular rotary cutter reactor respectively. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain Grignard reagent.

[0124] Step Two: Addition reaction

[0125] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. Control the reaction temperature between 40 °C - 50 °C, control the flow rate of the Grignard reagent at 1200 mL / min, and the flow rate of furfural at 280 mL / min, so that the reaction proceeds for 4 hours to obtain an addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0126] Step Three: Hydrolysis reaction

[0127] Pump the flowing out addition reagent into the second rotary tubular reactor using a metering pump, control the flow rate at 2000 mL / min, and simultaneously pump in an aqueous magnesium chloride solution (1.07 mol / L) at a certain ratio, with a flow rate of 555 mL / min. Control the temperature at 26 °C - 28 °C, so that the reaction proceeds for 3 hours under normal pressure, and the produced material is a furfuryl alcohol mixed solution and basic magnesium chloride.

[0128] Step Four: Vacuum distillation

[0129] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. Control the distillation temperature at 60 - 65 °C to separate out the toluene and tetrahydrofuran mixed solvent, which is recycled for subsequent use; continue distillation, control the end point temperature to be less than 90 °C, take samples for detection. When the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0130] Step Five: Chlorination reaction

[0131] Add an aqueous methanol solution (the mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas for reaction for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorination reagent;

[0132] Step Six: Chlorination hydrolysis reaction

[0133] The obtained chlorinating reagent is pumped into the chlorination hydrolysis kettle, and methanol is distilled out under positive pressure. The distillation time is 2.5 hours and the temperature is 92 °C. Then, the temperature is reduced to 65 °C, and an ammonia water solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5, obtaining black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, and filtered to obtain the first crude product. The black oil is distilled and sublimated to obtain the second crude product and pitch. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0134] Comparative Example 2

[0135] This comparative example provides a method for producing ethyl maltol, including the following steps:

[0136] Step 1: Grignard reaction

[0137] Toluene and tetrahydrofuran are respectively pumped into the first tubular rotary cutter reactor using metering pumps. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Magnesium chips and chloroethane are added to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. The initiation temperature is controlled at 60 - 65 °C, and the reaction temperature is 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain the Grignard reagent.

[0138] Step 2: Addition reaction

[0139] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. The reaction temperature is controlled between 28 °C - 32 °C. The flow rate of the Grignard reagent is controlled at 1200 mL / min, and the flow rate of furfural is 280 mL / min, making the reaction proceed for 4 hours to obtain the addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0140] Step 3: Hydrolysis reaction

[0141] The flowing out addition reagent is pumped into the second rotary cutter tubular reactor using a metering pump, and the flow rate is controlled at 2000 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in at a certain ratio simultaneously, and its flow rate is 555 mL / min. The temperature is controlled at 40 °C - 50 °C, making the reaction proceed for 3 hours under normal pressure reaction, and the produced material is a furfuryl propanol mixed solution and basic magnesium chloride.

[0142] Step 4: Vacuum distillation

[0143] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum still for 6 hours, with the negative pressure below -0.095 MPa, and the distillation temperature is controlled at 60 - 65°C to separate out the toluene and tetrahydrofuran mixed solvent, which is recycled for subsequent use; continue distillation, control the end temperature to be less than 90°C, take samples for detection, and when the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0144] Step Five: Chlorination Reaction

[0145] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18°C, introduce chlorine gas for reaction for 4.5 hours, and control the reaction temperature at -10°C to obtain a chlorinating reagent.

[0146] Step Six: Chlorination Hydrolysis Reaction

[0147] Pump the obtained chlorinating reagent into a chlorination hydrolysis kettle, distill out methanol under positive pressure for 2.5 hours at a temperature of 92°C, then cool down to 65°C, add an aqueous ammonia solution with a concentration of 25% to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. Cool and crystallize the yellow aqueous solution, filter to obtain the first crude product, distill and sublime the black oil to obtain the second crude product and pitch, and recrystallize and purify the first crude product and the second crude product to obtain ethyl maltol.

[0148] Comparative Example 3

[0149] This comparative example provides a method for producing ethyl maltol, including the following steps:

[0150] Step 1: Grignard Reaction

[0151] Use a metering pump to pump toluene and tetrahydrofuran into the first tubular rotary cutter reactor respectively. The flow rate of toluene is 1000 mL / min, and the flow rate of tetrahydrofuran is 330 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 230 g / min. Control the initiation temperature at 60 - 65°C and the reaction temperature at 80 - 100°C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain a Grignard reagent.

[0152] Step Two: Addition Reaction

[0153] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into a second continuous flow microchannel reactor by metering pumps. The reaction temperature is controlled between 28°C and 32°C. The flow rate of the Grignard reagent is controlled at 1200 mL / min, and the flow rate of furfural is 280 mL / min, so that the reaction proceeds for 4 hours to obtain an addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0154] Step 3: Hydrolysis reaction

[0155] The outflowing addition reagent is pumped into a second rotary cutting tube reactor by a metering pump, with the flow rate controlled at 2000 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in at a certain ratio simultaneously, with its flow rate being 555 mL / min. The temperature is controlled at 26°C - 28°C, so that the reaction proceeds for 3 hours under atmospheric pressure, and the resulting material is a furfuryl propanol mixed solution and basic magnesium chloride.

[0156] Step 4: Vacuum distillation

[0157] The furfuryl propanol mixed solution is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. The distillation temperature is controlled at 60 - 65°C to separate out the toluene and tetrahydrofuran mixed solvent, which is recycled for subsequent use; continue distillation, control the end point temperature to be less than 90°C, take samples for detection. When the furfuryl propanol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0158] Step 5: Chlorination reaction

[0159] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl propanol) to obtain a furfuryl propanol - methanol mixed solution. When the temperature of the reaction kettle drops below -18°C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10°C to obtain a chlorination reagent;

[0160] Step 6: Chlorination hydrolysis reaction

[0161] The obtained chlorination reagent is pumped into a chlorination hydrolysis kettle, and methanol is distilled out under positive pressure for 2.5 hours at a temperature of 92°C. Then the temperature is lowered to 65°C, and an aqueous ammonia solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, filtered to obtain a first crude product. The black oil is distilled and sublimated to obtain a second crude product and asphalt. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0162] Comparative Example 4

[0163] This comparative example provides a method for producing ethyl maltol, including the following steps:

[0164] Step 1: Format reaction

[0165] Use metering pumps to pump toluene and tetrahydrofuran into the first tubular rotary cutting reactor respectively. The flow rate of toluene is 2000 mL / min, and the flow rate of tetrahydrofuran is 667 mL / min. Add magnesium chips and chloroethane to react. The feeding rate of magnesium chips is 180 g / min, and the feeding rate of chloroethane is 650 g / min. Control the initiation temperature at 60 - 65 °C and the reaction temperature at 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain Grignard reagent.

[0166] Step 2: Addition reaction

[0167] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. Control the reaction temperature between 28 °C and 32 °C. Control the flow rate of the Grignard reagent at 1500 mL / min and the flow rate of furfural at 380 mL / min to make the reaction proceed for 4 hours to obtain the addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0168] Step 3: Hydrolysis reaction

[0169] Pump the flowing out addition reagent into the second rotary cutting tubular reactor using a metering pump, control the flow rate at 2000 mL / min, and simultaneously pump in an aqueous solution of magnesium chloride (1.07 mol / L) at a certain ratio, with a flow rate of 555 mL / min. Control the temperature at 26 °C - 28 °C to make the reaction proceed for 3 hours under normal pressure to produce a mixed solution of furfuryl alcohol and basic magnesium chloride.

[0170] Step 4: Vacuum distillation

[0171] The mixed solution of furfuryl alcohol is subjected to vacuum distillation in a vacuum kettle for 6 hours, with the negative pressure below -0.095 MPa. Control the distillation temperature at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran for subsequent recycling; continue distillation, control the end temperature to be less than 90 °C, take samples for detection. When the content of furfuryl alcohol ≥ 95%, the content of toluene and tetrahydrofuran solvents ≤ 2.0%, and the content of furfural ≤ 1.5%, the distillation reaction ends.

[0172] Step 5: Chlorination reaction

[0173] Add an aqueous solution of methanol (the mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a mixed solution of furfuryl alcohol - methanol. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas for reaction for 4.5 hours, and control the reaction temperature at -10 °C to obtain the chlorination reagent;

[0174] Step 6: Chlorination hydrolysis reaction

[0175] The obtained chlorinating reagent is pumped into the chlorination hydrolysis kettle, and methanol is distilled out under positive pressure. The distillation time is 2.5 hours and the temperature is 92 °C. Then the temperature is lowered to 65 °C, and an aqueous ammonia solution with a concentration of 25% is added to adjust the pH value to 2.2 - 2.5, obtaining black oil and a yellow aqueous solution. The yellow aqueous solution is cooled and crystallized, and filtered to obtain the first crude product. The black oil is distilled and sublimated to obtain the second crude product and asphalt. The first crude product and the second crude product are recrystallized and purified to obtain ethyl maltol.

[0176] Comparative Example 5

[0177] This comparative example provides a production method of ethyl maltol, including the following steps:

[0178] Step 1: Grignard reaction

[0179] Toluene and tetrahydrofuran are respectively pumped into the first tubular rotary cutter reactor using metering pumps. The flow rate of toluene is 1250 mL / min, and the flow rate of tetrahydrofuran is 417 mL / min. Magnesium chips and chloroethane are added to react. The feeding rate of magnesium chips is 100 g / min, and the feeding rate of chloroethane is 283 g / min. The initiation temperature is controlled at 60 - 65 °C, and the reaction temperature is 80 - 100 °C for 3 hours. The solution flowing out of the tubular reactor then enters the first microchannel reactor for full reaction to obtain the Grignard reagent.

[0180] Step 2: Addition reaction

[0181] The Grignard reagent obtained in Step 1 and furfural are respectively pumped into the second continuous flow microchannel reactor using metering pumps. The reaction temperature is controlled between 28 °C and 32 °C. The flow rate of the Grignard reagent is controlled at 650 mL / min, and the flow rate of furfural is 280 mL / min, making the reaction proceed for 4 hours to obtain the addition reagent, and the utilization rate of the Grignard reagent can reach 100%.

[0182] Step 3: Hydrolysis reaction

[0183] The flowing out addition reagent is pumped into the second rotary cutter tubular reactor using a metering pump, and the flow rate is controlled at 2000 mL / min. An aqueous magnesium chloride solution (1.07 mol / L) is pumped in at a certain ratio simultaneously, and its flow rate is 500 mL / min. The temperature is controlled at 26 °C - 28 °C, making the reaction proceed for 3 hours under normal pressure, and the output materials are a furfuryl propanol mixed solution and basic magnesium chloride.

[0184] Step 4: Vacuum distillation

[0185] The furfuryl alcohol mixed solution is subjected to vacuum distillation in a vacuum still for 6 hours, with the negative pressure below -0.095 MPa, and the distillation temperature is controlled at 60 - 65 °C to separate out the mixed solvent of toluene and tetrahydrofuran, which is then recycled for subsequent use; continue distillation, control the end temperature to be less than 90 °C, take samples for detection, and when the furfuryl alcohol content ≥ 95%, the toluene and tetrahydrofuran solvent content ≤ 2.0%, and the furfural content ≤ 1.5%, the distillation reaction ends.

[0186] Step Five: Chlorination Reaction

[0187] Add an aqueous methanol solution (mass fraction of methanol is 60%) to the reaction kettle (containing furfuryl alcohol) to obtain a furfuryl alcohol - methanol mixed solution. When the temperature of the reaction kettle drops below -18 °C, introduce chlorine gas to react for 4.5 hours, and control the reaction temperature at -10 °C to obtain a chlorinating reagent.

[0188] Step Six: Chlorination Hydrolysis Reaction

[0189] Transfer the obtained chlorinating reagent into a chlorination hydrolysis kettle, distill out methanol under positive pressure for 2.5 hours at a temperature of 92 °C, then cool down to 65 °C, add an aqueous ammonia solution with a concentration of 25% to adjust the pH value to 2.2 - 2.5 to obtain black oil and a yellow aqueous solution. Cool and crystallize the yellow aqueous solution, filter to obtain the first crude product, distill and sublime the black oil to obtain the second crude product and asphalt, and recrystallize and purify the first crude product and the second crude product to obtain ethyl maltol.

[0190] Experimental Example

[0191] Calculate the yield and detect the purity of the furfuryl alcohol prepared in Step Four of Examples 1 - 6 and Comparative Examples 1 - 5:

[0192] Yield calculation: The furfuryl alcohol is prepared by the format reaction (Grignard reaction), and the yield calculation method is as follows:

[0193] Yield = (amount of furfuryl alcohol actually obtained ÷ amount of furfuryl alcohol theoretically obtainable) × 100%

[0194] The theoretical yield is calculated based on the chemical reaction equation, using the amount of the starting material that has completely reacted to calculate the amount of the product. Based on the amount of the reaction raw materials input (calculated by the mass of magnesium), calculate the amount of furfuryl alcohol that should be produced in a complete reaction according to the stoichiometric relationship.

[0195] The actual yield is the mass of furfuryl alcohol actually weighed after purification, drying and other operations at the end of the experimental operation.

[0196] Purity detection: Use gas chromatography to detect the purity of furfuryl alcohol, and the method is as follows:

[0197] Inject an appropriate amount of the diluted sample solution into the gas chromatograph. For Examples 1 and 4, and Comparative Examples 4 and 5, refer to the gas chromatograms respectively in Figures 1-4 , record the chromatographic peak area of furfuryl alcohol in the sample, and calculate the purity of furfuryl alcohol according to the formula: Purity = Chromatographic peak area of furfuryl alcohol / Sum of all chromatographic peak areas × 100%.

[0198] The results are shown in Table 1:

[0199] Table 1 Yield and purity of furfuryl alcohol prepared in Step 4 of Examples 1-6 and Comparative Examples 1-5

[0200]

[0201] It can be seen from Table 1 that: By precisely controlling the feeding rate, reaction time, and temperature of the materials, the present invention significantly improves the purity and yield of the intermediate furfuryl alcohol, thereby improving the purity and yield of the final product ethyl maltol.

[0202] Although the principle of the present invention has been described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are only explanations of the illustrative implementation manners of the present invention, and do not limit the scope of the present invention. The details in the embodiments do not constitute a limitation to the scope of the present invention. Without departing from the spirit and scope of the present invention, any obvious changes such as equivalent transformations and simple substitutions based on the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for producing ethyl maltol, characterized in that: The following steps are involved: S1: mixing toluene and tetrahydrofuran at flow rates of 1200-2500 mL / min and 400-1000 mL / min respectively, then adding magnesium chips and ethyl chloride to carry out a Grignard reaction to obtain a Grignard reagent, then mixing the Grignard reagent and furfural to carry out an addition reaction to obtain an addition reagent; S2: mixing the addition reagent and magnesium chloride solution, performing a hydrolysis reaction to obtain a furfuryl propanol mixed solution and basic magnesium chloride, performing reduced pressure distillation on the furfuryl propanol mixed solution to obtain furfuryl propanol, and finally performing a chlorination reaction and a chlorination hydrolysis reaction to obtain ethyl maltol; The acceleration rate of the magnesium chips is 80-150 g / min, and the acceleration rate of the ethyl chloride is 280-650 g / min.

2. The production method of ethyl maltol according to claim 1, characterized in that When the Grignard reagent and furfural are mixed, the flow rate of the Grignard reagent is 200-1200 mL / min, and the flow rate of furfural is 200-350 mL / min; or, The flow rate of the Grignard reagent is 1600-2000 mL / min, and the flow rate of furfural is 400-2000 mL / min.

3. The production method of ethyl maltol according to claim 1, characterized in that When the addition reagent and the magnesium chloride solution are mixed, the flow rate of the addition reagent is 1000-3000 mL / min, and the flow rate of the magnesium chloride solution is 520-1000 mL / min; and / or, The concentration of the magnesium chloride solution is 0.5-1.2 mol / L.

4. The method for producing ethyl maltol according to claim 1, characterized in that The volume ratio of toluene to tetrahydrofuran is 3:1; and / or, The temperature of the format reaction is 81-100° C. and the time is 2.5-3.5 hours.

5. The method for producing ethyl maltol according to claim 1, characterized in that: The reaction temperature of the addition reaction is below 35° C. and the reaction time is 3.5-4.5 hours; and / or, The reaction temperature of the hydrolysis reaction is below 30° C. and the reaction time is 2.5-3.5 hours.

6. The method for producing ethyl maltol according to claim 1, characterized in that: The temperature of the reduced pressure distillation is 60-65°C and the time is 5.5-6.5 hours; and / or, The pressure of the reduced pressure distillation is below -0.095 MPa.

7. The method for producing ethyl maltol according to claim 1, characterized in that: The index for the end of the reduced pressure distillation is: when the content of furfuryl propanol in the mixed solution is ≥95%, the content of toluene and tetrahydrofuran is ≤2.0%, and the content of furfural is ≤1.5%, the reduced pressure distillation is ended.

8. The method for producing ethyl maltol according to claim 1, characterized in that: The toluene and tetrahydrofuran separated by the reduced pressure distillation are recycled to the Grignard reaction for further use.

9. The method for producing ethyl maltol according to claim 1, characterized in that: The chlorination reaction comprises the following steps: After mixing furfuryl propanol and methanol aqueous solution, adjusting the temperature to below -18°C, introducing chlorine gas to react, and obtaining a chlorination reagent; The reaction temperature is (-12)-(-10)°C and the reaction time is 4-5 hours; The mass fraction of methanol in the methanol aqueous solution is 59-61%.

10. The method for producing ethyl maltol according to claim 9, characterized in that: The chlorination hydrolysis reaction comprises the following steps: The chlorination reagent is distilled, and then an alkaline solution is added dropwise to adjust the pH value to 2.2-2.5 to obtain black oil and a yellow aqueous solution, the yellow aqueous solution is cooled and crystallized, and filtered to obtain a first crude product, the black oil is distilled and sublimated to obtain a second crude product and asphalt, and the first crude product and the second crude product are recrystallized and purified; The distillation temperature is 92-95°C and the time is 2-3 hours; Before adding the alkaline solution, cool to 62-68°C; The alkaline solution is selected from one or more of 25% aqueous ammonia solution, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution and potassium carbonate solution.

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