Preparation method of N-methylisopropylamine based on heterogeneous catalysis

Abstract

The invention provides a preparation method of N-methylisopropylamine based on heterogeneous catalysis. The preparation method comprises the following steps: step 1, premixing CO2, isopropylamine gas and a gas solvent according to a molar ratio of (2-5): 1: (4-8); 2, the mixed gas and hydrogen are mixed, the molar ratio of hydrogen to CO2 is (2-5): 1, the mixed gas is introduced into an alkylation fixed bed reactor and subjected to a contact reaction with a heterogeneous catalyst, and the heterogeneous catalyst is a Pd-Mn / carrier; 3, the obtained product is subjected to cooling, gas-liquid separation and fractionation, and N-methylisopropylamine is obtained.The method is simple in raw material composition and green in process, compared with a traditional technology, use of a methylation reagent is avoided, toxicity and use cost are reduced, in addition, carbon dioxide is adopted as a methylation raw material, carbon is reduced, cost is low, the process is simple, and automatic control is easy.

Description

Technical Field

[0001] The invention discloses a method for synthesizing N-methylisopropylamine, belonging to the field of green preparation of pesticide intermediates. Background Art

[0002] N-methylisopropylamine, also known as N-methylisopropylamine or N-isopropylmethylamine, is primarily used to prepare new herbicides such as saflufenacil and has promising development prospects. As described in CN113979953B, saflufenacil is manufactured using N-methylisopropylamine in a multi-step process.

[0003] Specifically, there are numerous methods for synthesizing N-methylisopropylamine. Depending on the reaction route, the following main methods exist: 1. The reaction of isopropylamine with a methylating agent (such as methyl iodide, dimethyl sulfate, or dimethyl carbonate) under alkaline conditions to produce N-methylisopropylamine. For example, CN112851519B discloses a method using dimethyl carbonate and isopropylamine with an alkaline catalyst. This method allegedly overcomes the problems of high temperature and pressure and the difficulty in separating by-products in the prior art, achieving efficient and green N-methylisopropylamine synthesis, meeting the requirements for feedstock conversion and selectivity, and achieving yields exceeding 90%. 2. The reaction of acetone with monomethylamine and hydrogen to produce N-methylisopropylamine. For example, CN106866424A discloses a batch-process method for preparing N-methylisopropylamine. This patent involves introducing acetone and Raney nickel into a stainless steel hydrogenation reactor, introducing monomethylamine gas under pressure, and then introducing hydrogen under pressure to react. After the reaction, the filtrate is filtered and distilled under atmospheric pressure to produce N-methylisopropylamine.

[0004] Among methylation reagents, dimethyl carbonate (DMCO) is a relatively advanced process. However, its process produces carbon dioxide as a byproduct. While this yield of isopropylamine is high, the utilization rate of DMCO is low, resulting in high raw material costs. Reducing CO2 emissions, lowering production costs, and improving the green nature of the process are crucial.

[0005] The present invention uses carbon dioxide as a methylation feedstock, achieving carbon emission reductions and high utilization rates, which is of great value. However, how to achieve this requires careful and detailed research. The present invention discloses a technical solution provided after systematic research. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a green and low-cost method for synthesizing N-methylisopropylamine, which uses carbon dioxide as a methylation raw material, allows carbon dioxide to react with isopropylamine to form an amide salt, and then undergoes a hydrogenation reaction in a reactor to convert it into N-methylisopropylamine.

[0007] Specifically, the present invention provides a method for preparing N-methylisopropylamine based on heterogeneous catalysis, comprising the following steps:

[0008] Step 1: Pre-mix CO2, isopropylamine gas, and gas solvent in a molar ratio of (2-5):1:(4-8);

[0009] Step 2: mixing the mixed gas with hydrogen at a molar ratio of hydrogen to CO2 of (2-5):1, passing the mixed gas into an alkylation fixed-bed reactor for contact reaction with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / support;

[0010] Step 3: Cooling the obtained product, performing gas-liquid separation and fractionation to obtain N-methylisopropylamine.

[0011] Furthermore, the premixing conditions in step 1 are specifically as follows: the mixer temperature is controlled at 120-160° C., and the residence time of CO 2 , isopropylamine gas and gaseous solvent in the premixer is controlled at 0.5-2 hours.

[0012] Furthermore, the reaction conditions in step 2 are:

[0013] The reactor temperature is controlled at 150~200℃, the reaction pressure is controlled at 2~4MPa, and the liquid hourly space velocity is (0.2~0.4)h-1 based on isopropylamine. -1 .

[0014] Furthermore, the gaseous solvent is selected from one or more of cyclohexane, methylcyclohexane, and n-octane; the carrier of the heterogeneous catalyst is selected from one or more of alumina or silicon oxide, the Pd loading in the heterogeneous catalyst is 0.5~3wt%, and the mass ratio of Pd to Mn is controlled at 1:(0.1~0.5).

[0015] Furthermore, step 3 specifically includes:

[0016] The crude reaction product obtained in step 2 is cooled and sequentially enters a gas-liquid separation tower, an isopropylamine removal tower, and an intermediate distillate removal tower to obtain the product at the top of the product tower. The bottom of the product tower is passed through a solvent tower to recover the solvent.

[0017] Furthermore, the equipment used for premixing in step 1 is a premixer, which is a horizontal shell-and-tube type and has an enhanced mass transfer unit placed inside to ensure that the enhanced Reynolds number Re ≥ 2000. The enhanced mass transfer unit is one of a wire mesh type, a twisted sheet type, and a packing type. Thermal oil, steam, or hot water is introduced from the outside to maintain the temperature at 130-150° C.; the isopropylamine and carbon dioxide are preheated to 90-150° C. before entering the premixer; and the alkylation fixed-bed reactor is a shell-and-tube reactor.

[0018] Furthermore, in the step, CO2, isopropylamine and solvent are pre-mixed in a molar ratio of (2-3):1:(4-6), and hydrogen is subsequently introduced to ensure that the molar ratio of hydrogen to CO2 is (3-4):1;

[0019] Furthermore, in step 2, the Pd loading of the heterogeneous catalyst is controlled at 1-2 wt %, and the mass ratio of Pd to Mn is controlled at 1:0.2-0.3;

[0020] Furthermore, the temperature of gas-liquid separation in step 3 is controlled at 60-80°C.

[0021] Furthermore, in step 2, the Pd loading of the heterogeneous catalyst is controlled at 1.2-1.5 wt %, the mass ratio of Pd to Mn is controlled at 1:0.25-0.28, the reaction temperature is 160-170° C., and the reaction pressure is controlled at 3.0-3.5 MPa.

[0022] Compared with the prior art, the present invention has a simple raw material composition and a green process. Compared with traditional processes, it avoids the use of methylating agents, reducing toxicity and cost. In addition, the present invention uses carbon dioxide as the methylation raw material, which reduces carbon emissions and is low in cost. The process is simple and easy to automate. DETAILED DESCRIPTION

[0023] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0024] The embodiment of the present invention provides a method for preparing N-methylisopropylamine based on heterogeneous catalysis, comprising the following steps:

[0025] Step 1: Pre-mix CO2, isopropylamine gas, and gas solvent in a molar ratio of (2-5):1:(4-8);

[0026] Step 2: mixing the mixed gas with hydrogen at a molar ratio of hydrogen to CO2 of (2-5):1, passing the mixed gas into an alkylation fixed-bed reactor for contact reaction with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / support;

[0027] Step 3: Cooling the obtained product, performing gas-liquid separation and fractionation to obtain N-methylisopropylamine.

[0028] The overall reaction equation of the specific process of the embodiment of the present invention is as follows:

[0029]

[0030] In some optional embodiments, the premixing conditions in step 1 are specifically as follows: the mixer temperature is controlled at 120-160° C., and the residence time of CO 2 , isopropylamine gas and gaseous solvent in the premixer is controlled at 0.5-2 hours.

[0031] In some optional embodiments, the reaction conditions in step 2 are:

[0032] The reactor temperature is controlled at 150~200℃, the reaction pressure is controlled at 2~4MPa, and the liquid hourly space velocity is (0.2~0.4)h-1 based on isopropylamine. -1 .

[0033] In some optional embodiments, the gaseous solvent is selected from one or more of cyclohexane, methylcyclohexane, and n-octane; the carrier of the heterogeneous catalyst is selected from one or more of alumina or silica; the Pd loading in the heterogeneous catalyst is 0.5-3 wt %, and the mass ratio of Pd to Mn is controlled at 1:(0.1-0.5). In some optional embodiments, the Pd loading in the heterogeneous catalyst in step 2 is controlled at 1-2 wt %, and the mass ratio of Pd to Mn is controlled at 1:(0.2-0.3). In some embodiments, the Pd loading in the heterogeneous catalyst in step 2 is controlled at 1.2-1.5 wt %, and the mass ratio of Pd to Mn is controlled at 1:0.25-0.28. The reaction temperature is 160-170° C., and the reaction pressure is controlled at 3.0-3.5 MPa.

[0034] In some optional embodiments, step 3 specifically includes:

[0035] The crude reaction product obtained in step 2 is cooled and sequentially enters a gas-liquid separation tower, an isopropylamine removal tower, and an intermediate distillate removal tower to obtain the product at the top of the product tower. The bottom of the product tower is passed through a solvent tower to recover the solvent.

[0036] In some optional embodiments, the equipment used for premixing in step 1 is a premixer, which is a horizontal shell-and-tube type and has an enhanced mass transfer unit placed inside to ensure that the enhanced Reynolds number Re ≥ 2000. The enhanced mass transfer unit is one of a wire mesh type, a twisted sheet type, and a packing type. Thermal oil, steam, or hot water is introduced from the outside to maintain the temperature at 130-150° C.; the isopropylamine and carbon dioxide are preheated to 90-150° C. before entering the premixer; and the alkylation fixed-bed reactor is a shell-and-tube reactor.

[0037] In some optional embodiments, in the step, CO2, isopropylamine and solvent are premixed in a molar ratio of (2~3):1:(4~6), and hydrogen is subsequently introduced to ensure that the molar ratio of hydrogen to CO2 is (3~4):1.

[0038] In some optional embodiments, the temperature of gas-liquid separation in step 3 is controlled at 60-80°C.

[0039] To further illustrate the specific embodiments of the present invention, the following several examples and comparative examples are disclosed. It should be noted that the premixing equipment used in step 1 of the present invention and comparative examples is a premixer. The premixer is a horizontal shell-and-tube type, and contains an enhanced mass transfer unit to ensure an enhanced Reynolds number (Re) ≥ 2000. The enhanced mass transfer unit is a wire mesh, twisted sheet, or packing type, and is fed with heat transfer oil, steam, or hot water to maintain the temperature at 130-150°C. The isopropylamine and carbon dioxide are preheated to 90-150°C before entering the premixer. The alkylation fixed-bed reactor is a shell-and-tube reactor.

[0040] Example 1

[0041] Step 1. CO2, isopropylamine, and solvent cyclohexane are premixed in a molar ratio of 3:1:5, wherein the flow rates of isopropylamine and cyclohexane are controlled by a feed pump, and CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 118 g / h (2 mol / h). After feeding, CO2, isopropylamine, and solvent cyclohexane are heated to 120°C by a heater, wherein the mixer temperature is controlled at 135-138°C, and the residence time in the premixer is controlled at 1.25 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 4532;

[0042] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and the contact reaction is carried out with a multiphase catalyst. The multiphase catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3.

[0043] Step 3. The crude reaction material obtained in step 2 is cooled to 65° C. and then enters the gas-liquid separation tank. The size of the gas-liquid separation tank is 5 L. The liquid in the gas-liquid separation tank is then sampled and analyzed. The reaction was carried out continuously for 1000 hours without any blockage or other phenomena. The isopropylamine conversion rate was 98%, the N-methylisopropylamine selectivity was 95%, and the equivalent yield was ~93% (isopropylamine conversion rate × N-methylisopropylamine selectivity). The liquid then passed through a deisopropylamine tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) in sequence. The top temperature of the deisopropylamine tower was controlled at 50°C, the tower pressure was controlled at 0.25 MPa, the reflux ratio was 500, the top extraction and feed ratio was 1:500, and the recovered isopropylamine had a purity of greater than 99%. The deisopropylamine tower bottom liquid then entered a deintermediate distillate tower. The top temperature of the deintermediate distillate tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) was controlled at 47°C, and the tower pressure was controlled at 0.03 MPa. , reflux ratio 15, top extraction and feed ratio is 2:100, tower bottom liquid continuously enters the product tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), and the product is obtained at the top of the product tower, the tower top temperature is controlled at 52°C, the tower pressure is controlled at 0.01MPa, the reflux ratio is 6, the tower top extraction and feed ratio is 20:100, the product purity is 99.9% (gas chromatography GC method), the product tower bottom enters the solvent tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), a phase separator is set at the top of the product tower, the oil phase refluxes, water is intermittently produced, the tower top temperature is controlled at 81°C, the tower pressure is controlled at 0.02MPa, the reflux ratio is 3, the tower top extraction and feed ratio is 90:100, and the purity of the recovered solvent cyclohexane is greater than 98%.

[0044] Example 2

[0045] Step 1. CO2, isopropylamine, and solvent cyclohexane are premixed in a molar ratio of 3:1:5, wherein the flow rates of isopropylamine and cyclohexane are controlled by a feed pump, and CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 118 g / h (2 mol / h). After feeding, the CO2, isopropylamine, and solvent cyclohexane are heated to 120°C by a heater, wherein the mixer temperature is controlled at 135-138°C, and the residence time in the premixer is controlled at 1.25 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 1800;

[0046] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and the reaction is carried out in contact with a heterogeneous catalyst Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5 wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3.

[0047] Step 3. The crude reaction mixture obtained in Step 2 is sequentially cooled to 65°C and then enters a gas-liquid separator, the size of the gas-liquid separator is 5L, and then the liquid in the gas-liquid separator is sampled and analyzed. The reaction is continuously carried out for 1000h, and no plugging phenomenon is observed. The conversion rate of isopropylamine is 85%, the selectivity of N-methylisopropylamine is 72%, and the equivalent yield is ~61% (conversion rate of isopropylamine x selectivity of N-methylisopropylamine). Subsequently, the liquid sequentially passes through a de-isopropylamine column (column diameter 50mm, effective packing height 2m, middle feeding), the top temperature of the de-isopropylamine column is controlled at 50°C, the column pressure is controlled at 0.25MPa, the reflux ratio is 500, and the top product is collected at a ratio of 1:500 to the feed. The purity of the recovered isopropylamine is greater than 85%. Subsequently, the de-isopropylamine column liquid enters a de-intermediate fraction column (column diameter 50mm, effective packing height 2m, middle feeding), the top temperature of the de-intermediate fraction column is controlled at 47°C, the column pressure is controlled at 0.03MPa, the reflux ratio is 15, and the top product is collected at a ratio of 2:100 to the feed. The column liquid continuously enters a product column (column diameter 50mm, effective packing height 2m, middle feeding), and the product is obtained at the top of the product column. The top temperature of the product column is controlled at 52°C, the column pressure is controlled at 0.01MPa, the reflux ratio is 6, and the top product is collected at a ratio of 20:100 to the feed. The purity of the product is 99.9% (by gas chromatography GC method). The product column liquid enters a solvent column (column diameter 50mm, effective packing height 2m, middle feeding), a phase separator is provided at the top of the product column, the oil phase is refluxed, and water is intermittently collected at the top. The top temperature of the solvent column is controlled at 81°C, the column pressure is controlled at 0.02MPa, the reflux ratio is 3, and the top product is collected at a ratio of 90:100 to the feed. The purity of the recovered solvent cyclohexane is greater than 98%.

[0048] Example 3

[0049] Step 1. CO2, isopropylamine and solvent cyclohexane are premixed in a molar ratio of 2:1:6, wherein the flow rate of isopropylamine and cyclohexane is controlled by a feed pump, and the flow rate of CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 118g / h (2mol / h). After feeding, CO2, isopropylamine and solvent cyclohexane are heated to 120°C by a heater, wherein the temperature of the mixer is controlled at 135-138°C, the residence time in the premixer is controlled at 1.25 hours, and a twisted sheet mass transfer enhancer is inserted into the premixer, and Re is 4532.

[0050] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and the contact reaction is carried out with a multiphase catalyst. The multiphase catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3.

[0051] Step 3. The crude reaction material obtained in step 2 is cooled to 65° C. and then enters the gas-liquid separation tank. The size of the gas-liquid separation tank is 5 L. The liquid in the gas-liquid separation tank is then sampled and analyzed. The reaction was carried out continuously for 1000 hours without any blockage or other phenomena. The isopropylamine conversion rate was 89%, the N-methylisopropylamine selectivity was 93%, and the equivalent yield was ~83% (isopropylamine conversion rate × N-methylisopropylamine selectivity). The liquid then passed through a deisopropylamine tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) in sequence. The top temperature of the deisopropylamine tower was controlled at 50°C, the tower pressure was controlled at 0.25 MPa, the reflux ratio was 500, the top extraction and feed ratio was 1:500, and the recovered isopropylamine had a purity of greater than 99%. The deisopropylamine tower bottom liquid then entered a deintermediate distillate tower. The top temperature of the deintermediate distillate tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) was controlled at 47°C, and the tower pressure was controlled at 0.03 MPa. , reflux ratio 15, top extraction and feed ratio is 2:100, tower bottom liquid continuously enters the product tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), and the product is obtained at the top of the product tower, the tower top temperature is controlled at 52°C, the tower pressure is controlled at 0.01MPa, the reflux ratio is 6, the tower top extraction and feed ratio is 20:100, the product purity is 99.9% (gas chromatography GC method), the product tower bottom enters the solvent tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), a phase separator is set at the top of the product tower, the oil phase refluxes, water is intermittently produced, the tower top temperature is controlled at 81°C, the tower pressure is controlled at 0.02MPa, the reflux ratio is 3, the tower top extraction and feed ratio is 90:100, and the purity of the recovered solvent cyclohexane is greater than 98%.

[0052] Example 4

[0053] Step 1. CO2, isopropylamine, and solvent cyclohexane are premixed in a molar ratio of 5:1:8, wherein the flow rates of isopropylamine and cyclohexane are controlled by a feed pump, and CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 118 g / h (2 mol / h). After feeding, CO2, isopropylamine, and solvent cyclohexane are heated to 120°C by a heater, wherein the mixer temperature is controlled at 135-138°C, and the residence time in the premixer is controlled at 1.25 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 4532;

[0054] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and a contact reaction is carried out with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3;

[0055] Step 3. The crude reaction material obtained in step 2 is cooled to 65° C. and then enters the gas-liquid separation tank. The size of the gas-liquid separation tank is 5 L. The liquid in the gas-liquid separation tank is then sampled and analyzed. The reaction was carried out continuously for 1000 hours without any blockage or other phenomena. The isopropylamine conversion rate was 99%, the N-methylisopropylamine selectivity was 80%, and the equivalent yield was ~79% (isopropylamine conversion rate × N-methylisopropylamine selectivity). The liquid then passed through a deisopropylamine tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) in sequence. The top temperature of the deisopropylamine tower was controlled at 50° C., the tower pressure was controlled at 0.25 MPa, the reflux ratio was 500, the top extraction and feed ratio was 1:500, and the recovered isopropylamine had a purity of greater than 99%. The deisopropylamine tower bottom liquid then entered a deintermediate distillate tower. The top temperature of the deintermediate distillate tower (tower diameter 50 mm, effective packing height 2 m, intermediate feed) was controlled at 47° C., and the tower pressure was controlled at 0.03 MPa. , reflux ratio 15, top extraction and feed ratio is 2:100, tower bottom liquid continuously enters the product tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), and the product is obtained at the top of the product tower, the tower top temperature is controlled at 52°C, the tower pressure is controlled at 0.01MPa, the reflux ratio is 6, the tower top extraction and feed ratio is 20:100, the product purity is 99.9% (gas chromatography GC method), the product tower bottom enters the solvent tower (tower diameter 50mm, effective packing height is 2m, intermediate feed), a phase separator is set at the top of the product tower, the oil phase refluxes, water is intermittently produced, the tower top temperature is controlled at 81°C, the tower pressure is controlled at 0.02MPa, the reflux ratio is 3, the tower top extraction and feed ratio is 90:100, and the purity of the recovered solvent cyclohexane is greater than 98%.

[0056] Example 5

[0057] Step 1. CO2, isopropylamine, and solvent cyclohexane are premixed in a molar ratio of 3:1:5, wherein the flow rates of isopropylamine and cyclohexane are controlled by a feed pump, and CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 354 g / h (6 mol / h). After feeding, CO2, isopropylamine, and solvent cyclohexane are heated to 120°C by a heater, wherein the mixer temperature is controlled at 135-138°C, and the residence time in the premixer is controlled at 2 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 4532;

[0058] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.5 MPa, and the catalyst is contacted with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5 wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3;

[0059] Step 3. The crude reaction mixture obtained from Step 2 was passed through a gas-liquid separator, which was cooled to 65°C, and the size of the gas-liquid separator was 5L, and then the liquid in the gas-liquid separator was sampled and analyzed. The reaction was continuously carried out for 1000h, and no phenomenon such as plugging was observed. The conversion rate of isopropylamine was 93%, the selectivity of N-methylisopropylamine was 92%, and the equivalent yield was ~86% (conversion rate of isopropylamine x selectivity of N-methylisopropylamine). Subsequently, the liquid was passed through a de-isopropylamine column (column diameter 50mm, effective packing height 2m, middle feeding) in sequence, the overhead temperature of the de-isopropylamine column was controlled at 50°C, the column pressure was controlled at 0.25MPa, the reflux ratio was 500, and the overhead product was taken out at a ratio of 1:500 to the feed. The purity of the recovered isopropylamine was greater than 99%. Subsequently, the de-isopropylamine column liquid was passed through a de-intermediate fraction column (column diameter 50mm, effective packing height 2m, middle feeding), the overhead temperature of the de-intermediate fraction column was controlled at 47°C, the column pressure was controlled at 0.03MPa, the reflux ratio was 15, and the overhead product was taken out at a ratio of 2:100 to the feed. The column liquid was continuously passed through a product column (column diameter 50mm, effective packing height 2m, middle feeding), and the product was obtained at the top of the product column. The overhead temperature of the product column was controlled at 52°C, the column pressure was controlled at 0.01MPa, the reflux ratio was 6, and the overhead product was taken out at a ratio of 20:100 to the feed. The purity of the product was 99.9% (by gas chromatography GC method). The product column liquid was passed through a solvent column (column diameter 50mm, effective packing height 2m, middle feeding), a phase separator was arranged at the top of the product column, the oil phase was refluxed, and water was intermittently taken out. The overhead temperature of the solvent column was controlled at 81°C, the column pressure was controlled at 0.02MPa, the reflux ratio was 3, and the overhead product was taken out at a ratio of 90:100 to the feed. The purity of the recovered solvent cyclohexane was greater than 98%.

[0060] Example 6

[0061] Step 1. CO2, isopropylamine and solvent cyclohexane were premixed in a molar ratio of 3:1:5. The flow rate of isopropylamine and cyclohexane was controlled by a feed pump, and the flow rate of CO2 was controlled by a gas flow meter. The flow rate of isopropylamine was 118g / h (2mol / h). After feeding, CO2, isopropylamine and solvent cyclohexane were heated to 120°C by a heater. The temperature of the mixer was controlled at 135-138°C. The residence time in the premixer was controlled at 1.25 hours. Twisted sheet mass transfer was inserted into the premixer, and Re was 4532.

[0062] Step 2. The above mixture was mixed with hydrogen, and the molar ratio of hydrogen to CO2 was 3:1. The above mixture was introduced into an alkylation fixed bed reactor. The loading amount of the catalyst in the fixed bed was 400ml, and the liquid hourly space velocity of isopropylamine was 0.4h -1The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and the catalyst is contacted with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 2 wt%, and the mass ratio of Pd to Mn is controlled at 1:0.2;

[0063] Step 3. The crude reaction material obtained in step 2 is cooled to 65°C and then enters the gas-liquid separation. The size of the gas-liquid separation tank is 5L. The liquid in the gas-liquid separation tank is then sampled and analyzed. The reaction is carried out continuously for 1000h without any blockage or other phenomena. The isopropylamine conversion rate is 99%, the N-methylisopropylamine selectivity is 85%, and the equivalent yield is ~84%. The liquid then passes through a deisopropylamine tower (tower diameter 50mm, effective packing height is 2m, intermediate feed) in sequence. The top temperature of the deisopropylamine tower is controlled at 50°C, the tower pressure is controlled at 0.25MPa, the reflux ratio is 500, the top extraction and feed ratio is 1:500, and the recovered isopropylamine purity is greater than 99%. The deisopropylamine tower bottom liquid then enters a deintermediate distillate tower. The top temperature of the deintermediate distillate tower (tower diameter 50mm, effective packing height is 2m, intermediate feed) is controlled at 47°C, the tower pressure is controlled at 0.03MPa, the reflux ratio is 15, and the top extraction and feed ratio is 1:500. The production-to-feed ratio is 2:100, the bottom liquid continuously enters the product tower (tower diameter 50 mm, effective packing height 2 m, intermediate feeding), and the product is obtained at the top of the product tower. The tower top temperature is controlled at 52°C, the tower pressure is controlled at 0.01 MPa, the reflux ratio is 6, the tower top production-to-feed ratio is 20:100, and the product purity is 99.9% (gas chromatography GC method). The bottom of the product tower enters the solvent tower (tower diameter 50 mm, effective packing height 2 m, intermediate feeding). A phase separator is set at the top of the product tower, the oil phase refluxes, and water is intermittently produced. The tower top temperature is controlled at 81°C, the tower pressure is controlled at 0.02 MPa, the reflux ratio is 3, the tower top production-to-feed ratio is 90:100, and the purity of the recovered solvent cyclohexane is greater than 98%.

[0064] Comparative Example 1

[0065] Step 1. CO2, isopropylamine and solvent cyclohexane are premixed at room temperature in a molar ratio of 3:1:5, wherein the flow rates of isopropylamine and cyclohexane are controlled by a feed pump, and CO2 is controlled by a gas flow meter, wherein the flow rate of isopropylamine is 118 g / h (2 mol / h). After feeding, CO2, isopropylamine and solvent cyclohexane are heated to 120°C by a heater, wherein the mixer temperature is controlled at 135-138°C, and the residence time in the premixer is controlled at 1.25 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 1795;

[0066] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and a contact reaction is carried out with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / Al2O3, wherein the Pd loading is controlled at 1.5wt%, and the mass ratio of Pd to Mn is controlled at 1:0.3;

[0067] Step 3. The crude reaction material obtained in step 2 is cooled to 65°C and then enters the gas-liquid separation. The size of the gas-liquid separation tank is 5L. The liquid in the gas-liquid separation tank is then sampled and analyzed. During 1000h of continuous operation, the isopropylamine conversion rate is 81%, the N-methylisopropylamine selectivity is 51%, and the equivalent yield is ~40%. The liquid then passes through a deisopropylamine tower (tower diameter 50mm, effective packing height 2m, intermediate feed). The top temperature of the deisopropylamine tower is controlled at 50°C, the tower pressure is controlled at 0.25MPa, the reflux ratio is 500, the top extraction and feed ratio is 1:500, and the recovered isopropylamine has a purity greater than 99%. The deisopropylamine tower bottom liquid then enters a deintermediate distillate tower. The top temperature of the deintermediate distillate tower (tower diameter 50mm, effective packing height 2m, intermediate feed) is controlled at 47°C, the tower pressure is controlled at 0.03MPa, the reflux ratio is 15, and the top extraction and feed ratio is 1:500. The ratio is 2:100, the bottom liquid continuously enters the product tower (tower diameter 50mm, effective packing height 2m, intermediate feeding), and the product is obtained at the top of the product tower. The tower top temperature is controlled at 52°C, the tower pressure is controlled at 0.01MPa, the reflux ratio is 6, the tower top production and feed ratio is 20:100, and the product purity is 99.9% (gas chromatography GC method). The bottom of the product tower enters the solvent tower (tower diameter 50mm, effective packing height 2m, intermediate feeding). A phase separator is set on the top of the product tower, the oil phase refluxes, and water is intermittently produced. The tower top temperature is controlled at 81°C, the tower pressure is controlled at 0.02MPa, the reflux ratio is 3, the tower top production and feed ratio is 90:100, and the purity of the recovered solvent cyclohexane is greater than 98%.

[0068] Comparative Example 2

[0069] Step 1. CO2, isopropylamine and solvent cyclohexane were premixed at room temperature with a molar ratio of 3:1:5, where the flow rate of isopropylamine and cyclohexane were controlled by feed pumps, and the flow rate of CO2 was controlled by a gas flow meter, where the flow rate of isopropylamine was 118 g / h (2 mol / h), and after feeding, the CO2, isopropylamine and solvent cyclohexane were heated to 120°C by a heater, where the temperature of the mixer was controlled at 135-138°C, and the residence time in the premixer was controlled at 1.25 hours, and the residence time in the premixer was controlled at 1.25 hours, and a twisted sheet mass transfer enhancer was inserted in the premixer, with a Re of 1795;

[0070] Step 2. The above mixture was mixed with hydrogen, where the molar ratio of hydrogen to CO2 was 3:1, and the above mixture was fed into an alkylation fixed bed reactor, where the catalyst loading in the fixed bed was 400 ml, and the liquid hourly space velocity (LHSV) of isopropylamine was 0.4 h -1 , the reactor temperature was controlled at 160°C, the reaction pressure was controlled at 3.1 MPa, and the contact reaction was carried out with a heterogeneous catalyst, which was Pd / Al2O3, where the Pd loading was controlled at 1.5 wt%, and the catalyst did not contain Mn;

[0071] Step 3. The crude reaction material obtained in step 2 was cooled to 65°C and then fed into a gas-liquid separator, where the size of the gas-liquid separator was 5 L, and then the liquid in the gas-liquid separator was sampled and analyzed. In 1000 h of continuous operation, the conversion rate of isopropylamine was 64%, the selectivity of N-methylisopropylamine was 52%, and the equivalent yield was ~33%, and then the liquid was sequentially fed into a deisopropylamine column (column diameter 50 mm, effective packing height 2 m, middle feeding), where the column top temperature of the deisopropylamine column was controlled at 50°C, the column pressure was controlled at 0.25 MPa, the reflux ratio was 500, and the column top take-off to feed ratio was 1:500, and the purity of the recovered isopropylamine was greater than 99%, and then the deisopropylamine column bottom liquid was fed into a de-intermediate fraction column (column diameter 50 mm, effective packing height 2 m, middle feeding), where the column top temperature of the de-intermediate fraction column was controlled at 47°C, the column pressure was controlled at 0.03 MPa, the reflux ratio was 15, and the column top take-off to feed ratio was 2:100, and the column bottom liquid was continuously fed into a product column (column diameter 50 mm, effective packing height 2 m, middle feeding), where the product was obtained at the column top, the column top temperature was controlled at 52°C, the column pressure was controlled at 0.01 MPa, the reflux ratio was 6, and the column top take-off to feed ratio was 20:100, and the purity of the product was 99.9% (gas chromatography, GC method), and the product column bottom was fed into a solvent column (column diameter 50 mm, effective packing height 2 m, middle feeding), where a phase separator was provided at the top of the product column, the oil phase was refluxed, the water was intermittently taken off, the column top temperature was controlled at 81°C, the column pressure was controlled at 0.02 MPa, the reflux ratio was 3, and the column top take-off to feed ratio was 90:100, and the purity of the recovered solvent cyclohexane was greater than 98%.

[0072] Comparative Example 3

[0073] Step 1. CO2, isopropylamine, and solvent cyclohexane are premixed in a molar ratio of 3:1:5. The flow rates of isopropylamine and cyclohexane are controlled by feed pumps, and the CO2 is controlled by a gas flow meter. The flow rate of isopropylamine is 118 g / h (2 mol / h). The residence time in the premixer is controlled at 1.25 hours. A twisted plate is inserted in the premixer to enhance mass transfer, and Re is 1795.

[0074] Step 2: The above mixture was mixed with hydrogen, wherein the molar ratio of hydrogen to CO2 was 3:1, and the above mixed raw materials were introduced into an alkylation fixed bed reactor, the catalyst loading amount in the fixed bed was 400 ml, and the liquid hourly space velocity (LISV) was 0.4 h-1, based on isopropylamine. -1 The reactor temperature is controlled at 160°C, the reaction pressure is controlled at 3.1 MPa, and the catalyst is contacted with a multiphase catalyst. The multiphase catalyst is Pd / Al2O3, wherein the Pd loading is controlled at 1.5 wt% and does not contain Mn.

[0075] Step 3. The crude reaction material obtained in Step 2 was cooled to 40-48°C and then placed in a 5L gas-liquid separator. The liquid in the separator was then sampled and analyzed. After the reaction system ran for 12 hours, the mixer and outlet gas-liquid separator interface were clogged, making subsequent processing impossible.

[0076] In the embodiments of the present invention, carbon dioxide and isopropylamine are premixed and the residence time, temperature, and Reynolds number (Re), representing the mixing intensity, are appropriately controlled to effectively improve the isopropylamine conversion rate and N-methylisopropylamine selectivity, thereby increasing the equivalent yield of N-methylisopropylamine. The mass transfer enhancement components in the present invention can be selected from a wire mesh, twisted sheet, or packing type. The flow enhancement components are suitable for achieving the Re enhancement requirements described in the present invention and are not limited to a fixed design. However, the Re value is a prerequisite for the implementation of the embodiments of the present invention.

[0077] The inventors speculate that the core reaction process of the embodiment of the present invention may be that isopropylamine first forms a salt with carbon dioxide, that is, a typical salt-forming reaction between amine and carbon dioxide actually occurs during the mixing process, as described below:

[0078]

[0079] Therefore, it can be seen from Examples 1-6 that in the early premixing process, the mixing uniformity has a great influence on the reaction yield.

[0080] Another aspect of the present invention provides a heterogeneous catalyst, wherein palladium is a preferred active component and manganese is a preferred promoter. The heterogeneous catalyst is a guarantee for achieving high yield.

[0081] Under the catalysts and matching processes of Examples 1-6 of the present invention, the yield of N-methylisopropylamine, calculated as isopropylamine, is greater than 85%, and greater than 90% under optimized conditions, wherein the yield of the main by-product N,N-dimethylisopropylamine is less than 10%, and less than 5% under optimized conditions.

[0082] The present invention needs to be controlled at a reasonable cooling temperature before gas-liquid separation. If the cooling temperature is higher than the above cooling temperature, a large amount of light component loss will be caused, and if the cooling temperature is lower than the above cooling temperature, a large amount of carbonate will be generated, thereby clogging the pipeline (refer to the clogging situation in Comparative Example 3). After careful experiments, the present invention found that the best effect is achieved when the temperature is controlled at 60~80℃, and more optimally controlled at 65~70℃.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, technicians can still modify or replace the specific implementation methods of the present invention with equivalents, but these modifications or changes do not depart from the scope of protection of the pending claims of the present application.

Claims

1. A method for preparing N-methylisopropylamine based on heterogeneous catalysis, characterized in that: The following steps are involved: Step 1: Pre-mix CO2, isopropylamine gas, and gas solvent in a molar ratio of (2-5):1:(4-8); Step 2: mixing the mixed gas with hydrogen at a molar ratio of hydrogen to CO2 of (2-5):1, passing the mixed gas into an alkylation fixed-bed reactor for contact reaction with a heterogeneous catalyst, wherein the heterogeneous catalyst is Pd-Mn / support; Step 3: Cooling the obtained product, performing gas-liquid separation and fractionation to obtain N-methylisopropylamine.

2. The method for preparing N-methylisopropylamine according to claim 1, wherein The premixing conditions in step 1 are specifically as follows: the mixer temperature is controlled at 120-160° C., and the residence time of CO 2 , isopropylamine gas and gaseous solvent in the premixer is controlled at 0.5-2 hours.

3. The method for preparing N-methylisopropylamine according to claim 1, wherein The reaction conditions in step 2 are: The reactor temperature is controlled at 150~200℃, the reaction pressure is controlled at 2~4MPa, and the liquid hourly space velocity is (0.2~0.4)h-1 based on isopropylamine. -1 .

4. The method for preparing N-methylisopropylamine according to claim 1, wherein The gaseous solvent is selected from one or more of cyclohexane, methylcyclohexane, and n-octane; the carrier of the heterogeneous catalyst is selected from one or more of aluminum oxide or silicon oxide, the Pd loading amount in the heterogeneous catalyst is 0.5~3wt%, and the mass ratio of Pd to Mn is controlled at 1:(0.1~0.5).

5. The method for preparing N-methylisopropylamine according to claim 1, wherein Step 3 specifically includes: The crude reaction product obtained in step 2 is cooled and sequentially enters a gas-liquid separation tower, an isopropylamine removal tower, and an intermediate distillate removal tower to obtain the product at the top of the product tower. The bottom of the product tower is passed through a solvent tower to recover the solvent.

6. The method for preparing N-methylisopropylamine according to claim 1, wherein The equipment used for premixing in step 1 is a premixer, which is a horizontal tube-type premixer with an enhanced mass transfer unit placed inside to ensure that the enhanced Reynolds number Re is greater than or equal to 2000. The enhanced mass transfer unit is one of a wire mesh type, a twisted sheet type, and a packing type. Thermal oil, steam, or hot water is introduced from the outside to maintain the temperature at 130-150°C. The isopropylamine and carbon dioxide are preheated to 90-150° C. before entering the premixer; and the alkylation fixed-bed reactor is a shell-and-tube reactor.

7. The method for preparing N-methylisopropylamine according to claim 1, wherein In the step, CO2, isopropylamine and solvent are premixed in a molar ratio of (2-3):1:(4-6), and hydrogen is subsequently introduced to ensure that the molar ratio of hydrogen to CO2 is (3-4):

1.

8. The method for preparing N-methylisopropylamine according to claim 4, wherein: In the step 2, the Pd loading of the heterogeneous catalyst is controlled at 1-2 wt %, and the mass ratio of Pd to Mn is controlled at 1:0.2-0.

3.

9. The method for preparing N-methylisopropylamine according to claim 5, wherein The temperature of gas-liquid separation in step 3 is controlled at 60-80°C.

10. The method for preparing N-methylisopropylamine according to claim 8, wherein In step 2, the Pd loading of the heterogeneous catalyst is controlled at 1.2-1.5 wt %, the mass ratio of Pd to Mn is controlled at 1:0.25-0.28, the reaction temperature is 160-170° C., and the reaction pressure is controlled at 3.0-3.5 MPa.

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