Preparation process of N-methyl-p-anisidine
阅读说明：本技术 一种n-甲基-对氨基苯甲醚的制备工艺 (Preparation process of N-methyl-p-anisidine ) 是由 程佛子 刘成翠 胡毅 于 2021-09-26 设计创作，主要内容包括：本发明提出了一种N-甲基-对氨基苯甲醚的制备工艺,包括如下步骤：S1,对氨基苯甲醚加氢除氯；S2,精对氨基苯甲醚单甲基化反应；S3,精馏。本发明采用对氨基苯甲醚加氢除氯和两段固定床催化,氮气控温反应解决了反应结焦、转化率低的技术问题,具有操作简单、条件温和、低污染、高收率的优点。(The invention provides a preparation process of N-methyl-p-anisidine, which comprises the following steps: s1, removing chlorine by hydrogenating para-anisidine; s2, performing monomethylation reaction of refined p-anisidine; and S3, rectifying. The invention adopts the para-anisidine hydrogenation dechlorination and two-section fixed bed catalysis, and the nitrogen temperature control reaction solves the technical problems of reaction coking and low conversion rate, and has the advantages of simple operation, mild condition, low pollution and high yield.)
1. A preparation process of N-methyl-p-anisidine is characterized by comprising the following steps: the method comprises the following steps:
s1, removing chlorine by hydrogenating para-anisidine: adding p-anisidine, methanol and a metal oxide catalyst A into a reactor, filling hydrogen, and heating and reacting for 5-6h at the temperature of 100-; after the reaction is finished, reducing the temperature of the reaction liquid to 40-60 ℃, centrifuging, and leaving supernatant to obtain the refined p-anisidine;
s2, performing monomethylation reaction of refined p-anisidine: adding the refined p-anisidine and the methanol in the step S1 into a heat exchanger, charging nitrogen, and heating until the reaction liquid is gasified; removing tar from the gasified mixed gas, and then putting the gasified mixed gas into a reactor with a built-in metal oxide catalyst B for catalytic reaction; after the reaction is finished, condensing, and removing nitrogen to obtain a liquid material;
s3, rectification: and (4) adding the liquid material obtained in the step S2 into a distillation kettle, and carrying out hydrogenation distillation to obtain the N-methyl-p-anisidine.
2. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: the catalytic reaction in the step S2 is carried out in a fixed bed reactor with a built-in metal oxide catalyst B, the reaction temperature is controlled at 250-290 ℃, and the pressure is controlled at 30-50 kPa.
3. The process for the preparation of N-methyl-p-anisidine according to claim 2, wherein: the fixed bed reactor is divided into a first reactor and a second reactor, reaction liquid sequentially enters the first reactor and the second reactor, the reaction liquid is catalyzed by the first reactor, nitrogen is filled into the reaction liquid to cool the temperature of the reaction liquid to 250 ℃, and then the reaction liquid enters the second reactor for catalysis.
4. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: the distillation temperature of the step S3 is controlled at 140 ℃ and the pressure is controlled at 3-6 kPa.
5. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: the metal oxide catalyst A comprises 50-65 parts of NiO and Al according to weight percentage2O335-50 parts.
6. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: the metal oxide catalyst B comprises, by weight, 10-15 parts of CuO, 20-30 parts of NiO, 5-10 parts of ZnO and Al2O310-30 parts of Cr2O310-15 parts.
7. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: p-anisidine in step S1: the mass ratio of the methanol is (2-6) to (1-2).
8. The process for the preparation of N-methyl-p-anisidine according to claim 1, wherein: fine p-anisidine in step S2: methanol: the mass ratio of the nitrogen is (2-5) to (1-3) to (5-8).
Technical Field
The invention relates to the technical field of organic chemical synthesis, in particular to a preparation process of N-methyl-p-anisidine.
Background
The gasoline antiknock can be divided into a metal ash type and an organic ash-free type according to the application characteristics, and the organic ash-free gasoline antiknock is a novel gasoline octane number accelerator, has a large octane number promotion range, and can simultaneously realize the cleanness of gasoline. The research on the performance of aromatic amine and other nitrogen-containing compounds shows that the aromatic amine and other nitrogen-containing compounds have better octane number improving effect, and the development of the aromatic amine and other nitrogen-containing compounds is greatly promoted due to the advantages of low volatility and the like. Among them, N-methylaniline has been widely used as an antiknock agent for gasoline. However, N-methylaniline also has the problems of high toxicity, environmental pollution and the like. Compared with N-methylaniline, the N-methyl p-methoxyaniline as the antiknock agent has the characteristics of low toxicity and better performance, and becomes an ideal choice for replacing the N-methylaniline.
Research shows that the reaction of methanol as methylating agent with p-anisidine to produce N-methyl p-anisidine is the greenest and economic way. Most of the existing preparation process patents of N-methyl-p-anisidine are catalyst types in research, such as molecular sieve supported active component catalysts, palladium carbon catalysts and metal oxide catalyst patents, and the preparation process is not mature at present and has low yield. Therefore, a set of mature preparation processes of N-methyl-p-anisidine is urgently needed to be researched.
Disclosure of Invention
In view of the above, the invention provides a preparation process of N-methyl-p-anisidine, which has high conversion efficiency, no coking and high operability.
The technical scheme of the invention is realized as follows: the invention provides a preparation process of N-methyl-p-anisidine, which comprises the following steps:
the raw material p-anisidine contains 0.2 percent of p-chloroaniline, which is equivalent to the chlorine content of about 500 PPM; the content of parachloroaniline allowed by the subsequent pure para-anisidine monomethylation catalyst is less than 30PPM, which is equivalent to 8PPM containing chlorine, and the para-anisidine is required to be hydrogenated to remove chlorine.
And (3) removing chlorine by hydrogenating para-anisidine: adding p-anisidine, methanol and a metal oxide catalyst A into a reactor, filling hydrogen, and heating and reacting for 5-6h at the temperature of 100-; after the reaction is finished, reducing the temperature of the reaction liquid to 40-60 ℃, centrifuging, and leaving supernatant to obtain the refined p-anisidine;
s2, performing monomethylation reaction of refined p-anisidine: adding the refined p-anisidine and the methanol in the step S1 into a heat exchanger, charging nitrogen, and heating until the reaction liquid is gasified; removing tar from the gasified mixed gas, and then adding the gasified mixed gas into a reactor with a built-in metal oxide catalyst B for catalytic reaction; after the reaction is finished, condensing, and removing nitrogen to obtain a liquid material;
s3, rectification: and (4) adding the liquid material obtained in the step S2 into a distillation kettle, and carrying out hydrogenation distillation to obtain the N-methyl-p-anisidine.
On the basis of the above technical solution, preferably, the catalytic reaction in step S2 is performed in a fixed bed reactor with a built-in metal oxide catalyst B, the reaction temperature is controlled at 250-290 ℃, and the pressure is controlled at 30-50 kPa.
On the basis of the technical scheme, preferably, the fixed bed reactor is divided into a first reactor and a second reactor, reaction liquid sequentially enters the first reactor and the second reactor, and after being catalyzed by the first reactor, nitrogen is filled into the reaction liquid to reduce the temperature of the reaction liquid to 250 ℃, and then the reaction liquid enters the second reactor for catalysis.
Based on the above technical solution, it is preferable that the distillation temperature of step S3 is controlled at 120-140 deg.C, and the pressure is controlled at 3-6 kPa.
On the basis of the technical scheme, preferably, the metal oxide catalyst A comprises 50-65 parts of NiO and Al according to weight percentage2O335-50 parts.
On the basis of the above technical scheme, preferably, the metal oxide catalyst B comprises, by weight, 10 to 15 parts of CuO, 20 to 30 parts of NiO, 5 to 10 parts of ZnO, and Al2O310-30 parts of Cr2O310-15 parts.
On the basis of the above technical solution, preferably, the p-anisidine in step S1: the mass ratio of the methanol is (2-6) to (1-2).
On the basis of the above technical solution, preferably, in step S2, the ratio of fine p-anisidine: methanol: the mass ratio of the nitrogen is (2-5) to (1-3) to (5-8).
Compared with the prior art, the preparation process of the N-methyl-p-anisidine has the following beneficial effects:
(1) the hydrogenation dechlorination reaction of the para-anisidine reduces the chlorine content to 8PPM, which is beneficial to the subsequent methylation reaction.
(2) The catalytic reaction adopts two sections of fixed beds, and the nitrogen is adopted between the sections to control the reaction temperature rise, thereby avoiding the reaction coking and being beneficial to improving the conversion rate of the para-anisidine.
(3) The partial pressure of reactants can be changed by controlling the flow of nitrogen and the proportion of p-anisidine, and the conversion rate of methylation reaction is improved.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention has the following properties:
1. p-anisidine of formula C7H9NO, molecular weight M ═ 123.15, yellow to reddish crystals, density 1.089g/cm3Melting point 57.2 deg.C, boiling point 242 deg.C, heat of vaporization 48.31 KJ/mol.
Consists of the following components: 99.0 percent of p-anisidine, less than 0.2 percent of p-chloroaniline, less than 0.5 percent of o-anisidine, less than 0.2 percent of low-boiling-point substances, less than 0.3 percent of high-boiling-point substances and less than 0.5 percent of water.
2. Methanol, molecular formula CH3OH, molecular weight M32.04, melting point-97 deg.C, boiling point 64.7 deg.C, density 0.7918g/cm3Colorless liquid, heat of vaporization 35.32KJ/mol, specific heat capacity 2.51KJ/kg. K.
Consists of the following components: more than or equal to 99.8 percent of methanol, less than or equal to 0.15 percent of water, less than or equal to 0.003 percent of acid or less than or equal to 0.008 percent of alkali, less than or equal to 0.005 percent of carbonyl compound and less than or equal to 0.003 percent of evaporation residue.
The product prepared by the invention: n-methyl-p-anisidine of the formula C8H11NO, molecular weight M137.18, purity not less than 99.0%, density 1.032g/cm3Melting point 33-36 deg.C, boiling point 252.4 deg.C (760Torr), and heat of vaporization 49 KJ/mol.
Example one
S1 dechlorination of p-anisidine by hydrogenation
The hydrogenation dechlorination system of the para-anisidine is operated intermittently.
The method comprises the following specific steps: p-anisidine and methanol are injected into a hydrogenation reactor, and a metal oxide catalyst A is added; charging hydrogen to 1.0 MPa. Heating to 100 deg.C with heat conducting oil under stirring and hydrogen, increasing pressure to 3.0MPa, and reacting for 5 hr. Cooling the reactant to 40 ℃ by using coil cooling water, discharging the reaction liquid to a centrifugal separator for centrifugation, and reserving supernatant liquid to obtain the refined p-anisidine clear liquid.
The metal oxide catalyst A comprises 50 parts of NiO and Al according to weight percentage2O335 parts of (A).
P-anisidine: the mass ratio of methanol is 2: 1.
S2, monomethylation of fine p-anisidine
The monomethylation reaction of the fine p-anisidine is continuous operation, and the pressure is controlled at 30 kPa.
The method comprises the following specific steps: the mixed clear liquid of the refined p-anisidine and the methanol is pumped to a heat exchanger by a gear pump to be heated to 200 ℃ and then mixed with 35Nm3The nitrogen was mixed and then fed to the vaporizer. The mixed materials are heated by heat-conducting oil in a vaporizer, all the materials are vaporized, and the materials are superheated to the methylation reaction temperature of 250 ℃ according to the requirement of a catalyst.
The mixed gas out of the vaporizer is separated by a tar separator, and the mixed gas without tar enters a methylation reactor to react at 290 ℃. The methylation reactor is a vertical fixed bed reactor, and 200L of metal oxide catalyst B is arranged in the methylation reactor. After the methylation reaction is finished, the materials exchange heat in a heat exchanger, are cooled to 40 ℃ in a water cooler and enter N2And separating the mixture to obtain liquid material.
The metal oxide catalyst B comprises 10 parts of CuO, 20 parts of NiO, 5 parts of ZnO and Al according to weight fraction2O310 parts of Cr2O310 parts.
Fine p-anisidine: methanol: the mass ratio of nitrogen is 2:1: 5.
S3, rectification
The rectification separation is intermittent and vacuum operation. The method comprises the following specific steps: out of N2And after the liquid material of the separator is sent into a distillation kettle, closing a feed valve, starting a vacuum pump and circulating water, starting heat-conducting oil for hydrogenation, and distilling to obtain the N-methyl p-anisidine. The temperature during distillation is controlled at 120 deg.C, and the pressure is controlled at 3kPa。
Example two
S1 dechlorination of p-anisidine by hydrogenation
The hydrogenation dechlorination system of the para-anisidine is operated intermittently.
The method comprises the following specific steps: p-anisidine and methanol are injected into a hydrogenation reactor, and a metal oxide catalyst A is added; charging hydrogen to 1.0 MPa. Heating to 150 deg.C with heat conducting oil under stirring and hydrogen, increasing pressure to 3.0MPa, and reacting for 6 hr. Cooling the reactant to 60 ℃ by using coil cooling water, discharging the reaction liquid to a centrifugal separator for centrifugation, and reserving supernatant liquid to obtain the refined p-anisidine clear liquid.
The metal oxide catalyst A comprises 65 parts of NiO and Al according to weight percentage2O350 parts of the raw materials.
P-anisidine: the mass ratio of methanol was 3: 1.
S2, monomethylation of fine p-anisidine
The monomethylation reaction of the fine p-anisidine is continuous operation, and the pressure is controlled at 50 kPa.
The method comprises the following specific steps: the mixed clear liquid of the refined p-anisidine and the methanol is pumped to a heat exchanger by a gear pump to be heated to 200 ℃ and mixed with about 35Nm3The nitrogen was mixed and then fed to the vaporizer. The mixed materials are heated by heat-conducting oil in a vaporizer, all the materials are vaporized, and the materials are superheated to the methylation reaction temperature of 250 ℃ according to the requirement of a catalyst.
The mixed gas out of the vaporizer is separated by a tar separator, and the mixed gas without tar enters a methylation reactor. The methylation reactor is a vertical fixed bed reactor and comprises a first reactor and a second reactor, and the total volume of the methylation reactor is 200L with a built-in metal oxide catalyst B. The mixed gas enters a first reactor and a second reactor in sequence for catalytic reaction, and about 14Nm is used at the outlet of the first reactor3And/h, mixing the circulating nitrogen at the temperature of 80 ℃, cooling to 250 ℃, and then entering a second reactor. After the methylation reaction is finished, the materials exchange heat in a heat exchanger, are cooled to 40 ℃ in a water cooler and enter N2And separating the mixture to obtain liquid material.
Metal oxide catalystsThe reagent B comprises 15 parts of CuO, 30 parts of NiO, 10 parts of ZnO and Al according to weight fraction2O330 parts of Cr2O315 parts.
Fine p-anisidine: methanol: the mass ratio of nitrogen is 5:3: 8.
S3, rectification
The rectification separation is intermittent and vacuum operation. The method comprises the following specific steps: out of N2And after the liquid material of the separator is sent into a distillation kettle, closing a feed valve, starting a vacuum pump and circulating water, starting heat-conducting oil for hydrogenation, and distilling to obtain the N-methyl p-anisidine. The temperature during distillation was controlled at 140 ℃ and the pressure at 6 kPa.
EXAMPLE III
S1 dechlorination of p-anisidine by hydrogenation
The hydrogenation dechlorination system of the para-anisidine is operated intermittently.
The method comprises the following specific steps: p-anisidine and methanol are injected into a hydrogenation reactor, and a metal oxide catalyst A is added; charging hydrogen to 1.0 MPa. Heating to 130 ℃ by using heat conducting oil under the conditions of stirring and hydrogen, increasing the pressure to 3.0MPa, and reacting for 5.5 hours. Cooling the reactant to 50 ℃ by using coil cooling water, discharging the reaction liquid to a centrifugal separator for centrifugation, and reserving supernatant liquid to obtain the refined p-anisidine clear liquid.
The metal oxide catalyst A comprises 55 parts of NiO and Al by weight2O340 parts of the components.
P-anisidine: the mass ratio of methanol was 3: 2.
S2, monomethylation of fine p-anisidine
The monomethylation reaction of the fine p-anisidine is continuous operation, and the pressure is controlled at 40 kPa.
The method comprises the following specific steps: the mixed clear liquid of the refined p-anisidine and the methanol is pumped to a heat exchanger by a gear pump to be heated to 200 ℃ and mixed with about 35Nm3The nitrogen was mixed and then fed to the vaporizer. The mixed materials are heated by heat-conducting oil in a vaporizer, all the materials are vaporized, and the materials are superheated to the methylation reaction temperature of 250 ℃ according to the requirement of a catalyst.
Mixed gas from the carburetorThe mixed gas after tar removal enters a methylation reactor after being separated by a tar separator. The methylation reactor is a vertical fixed bed reactor and comprises a first reactor and a second reactor, and the total volume of the methylation reactor is 200L with a built-in metal oxide catalyst B. The mixed gas enters a first reactor and a second reactor in sequence for catalytic reaction, and about 14Nm is used at the outlet of the first reactor3And/h, mixing the circulating nitrogen at the temperature of 80 ℃, cooling to 250 ℃, and then entering a second reactor. After the methylation reaction is finished, the materials exchange heat in a heat exchanger, are cooled to 40 ℃ in a water cooler and enter N2And separating the mixture to obtain liquid material.
The metal oxide catalyst B comprises 12 parts of CuO, 22 parts of NiO, 7 parts of ZnO and Al according to weight fraction2O315 parts of Cr2O313 parts.
Fine p-anisidine: methanol: the mass ratio of nitrogen is 2:1: 3.
S3, rectification
The rectification separation is intermittent and vacuum operation. The method comprises the following specific steps: out of N2And after the liquid material of the separator is sent into a distillation kettle, closing a feed valve, starting a vacuum pump and circulating water, starting heat-conducting oil for hydrogenation, and distilling to obtain the N-methyl p-anisidine. The temperature during distillation was controlled at 125 ℃ and the pressure at 4 kPa.
Example four
S1 dechlorination of p-anisidine by hydrogenation
The hydrogenation dechlorination system of the para-anisidine is operated intermittently.
The method comprises the following specific steps: p-anisidine and methanol are injected into a hydrogenation reactor, and a metal oxide catalyst A is added; charging hydrogen to 1.0 MPa. Heating to 120 deg.C with heat conducting oil under stirring and hydrogen, increasing pressure to 3.0MPa, and reacting for 5 hr. Cooling the reactant to 40 ℃ by using coil cooling water, discharging the reaction liquid to a centrifugal separator for centrifugation, and reserving supernatant liquid to obtain the refined p-anisidine clear liquid.
The metal oxide catalyst A comprises 60 parts of NiO and Al according to weight percentage2O345 parts of the raw materials.
P-anisidine: the mass ratio of methanol was 3: 1.
S2, monomethylation of fine p-anisidine
The monomethylation reaction of the fine p-anisidine is continuous operation, and the pressure is controlled at 45 kPa.
The method comprises the following specific steps: the mixed clear liquid of the refined p-anisidine and the methanol is pumped to a heat exchanger by a gear pump to be heated to 200 ℃ and mixed with about 35Nm3The nitrogen was mixed and then fed to the vaporizer. The mixed materials are heated by heat-conducting oil in a vaporizer, all the materials are vaporized, and the materials are superheated to the methylation reaction temperature of 250 ℃ according to the requirement of a catalyst.
The mixed gas out of the vaporizer is separated by a tar separator, and the mixed gas without tar enters a methylation reactor. The methylation reactor is a vertical fixed bed reactor and comprises a first reactor and a second reactor, and the total volume of the methylation reactor is 200L with a built-in metal oxide catalyst B. The mixed gas enters a first reactor and a second reactor in sequence for catalytic reaction, and about 14Nm is used at the outlet of the first reactor3And/h, mixing the circulating nitrogen at the temperature of 80 ℃, cooling to 250 ℃, and then entering a second reactor. After the methylation reaction is finished, the materials exchange heat in a heat exchanger, are cooled to 40 ℃ in a water cooler and enter N2And separating the mixture to obtain liquid material.
The metal oxide catalyst B comprises 14 parts of CuO, 28 parts of NiO, 8 parts of ZnO and Al according to weight fraction2O325 parts of Cr2O311 parts.
Fine p-anisidine: methanol: the mass ratio of nitrogen is 4:1: 7.
S3, rectification
The rectification separation is intermittent and vacuum operation. The method comprises the following specific steps: out of N2And after the liquid material of the separator is sent into a distillation kettle, closing a feed valve, starting a vacuum pump and circulating water, starting heat-conducting oil for hydrogenation, and distilling to obtain the N-methyl p-anisidine. The temperature during distillation was controlled at 135 ℃ and the pressure at 5 kPa.
EXAMPLE five
S1 dechlorination of p-anisidine by hydrogenation
The hydrogenation dechlorination system of the para-anisidine is operated intermittently.
The method comprises the following specific steps: p-anisidine and methanol are injected into a hydrogenation reactor, and a metal oxide catalyst A is added; charging hydrogen to 1.0 MPa. Heating to 110 deg.C with heat conducting oil under stirring and hydrogen, increasing pressure to 3.0MPa, and reacting for 6 hr. Cooling the reactant to 42 ℃ by using coil cooling water, discharging the reaction liquid to a centrifugal separator for centrifugation, and reserving supernatant liquid to obtain the refined p-anisidine clear liquid.
The metal oxide catalyst A comprises 58 parts of NiO and Al by weight2O342 parts of the raw materials.
P-anisidine: the mass ratio of methanol was 5: 1.
S2, monomethylation of fine p-anisidine
The monomethylation reaction of the fine p-anisidine is continuous operation, and the pressure is controlled at 48 kPa.
The method comprises the following specific steps: the mixed clear liquid of the refined p-anisidine and the methanol is pumped to a heat exchanger by a gear pump to be heated to 200 ℃ and mixed with about 35Nm3The nitrogen was mixed and then fed to the vaporizer. The mixed materials are heated by heat-conducting oil in a vaporizer, all the materials are vaporized, and the materials are superheated to the methylation reaction temperature of 250 ℃ according to the requirement of a catalyst.
The mixed gas out of the vaporizer is separated by a tar separator, and the mixed gas without tar enters a methylation reactor. The methylation reactor is a vertical fixed bed reactor and comprises a first reactor and a second reactor, and the total volume of the methylation reactor is 200L with a built-in metal oxide catalyst B. The mixed gas enters a first reactor and a second reactor in sequence for catalytic reaction, and about 14Nm is used at the outlet of the first reactor3And/h, mixing the circulating nitrogen at the temperature of 80 ℃, cooling to 250 ℃, and then entering a second reactor. After the methylation reaction is finished, the materials exchange heat in a heat exchanger, are cooled to 40 ℃ in a water cooler and enter N2And separating the mixture to obtain liquid material.
The metal oxide catalyst B comprises 14 parts of CuO, 26 parts of NiO, 6 parts of ZnO and Al according to weight fraction2O325 parts of Cr2O314 parts of (A).
Fine p-anisidine: methanol: the mass ratio of nitrogen is 3:1: 5.
S3, rectification
The rectification separation is intermittent and vacuum operation. The method comprises the following specific steps: out of N2And after the liquid material of the separator is sent into a distillation kettle, closing a feed valve, starting a vacuum pump and circulating water, starting heat-conducting oil for hydrogenation, and distilling to obtain the N-methyl p-anisidine. The temperature during distillation was controlled at 135 ℃ and the pressure at 4 kPa.
Comparative example
The prior preparation process of N-methyl-p-anisidine is taken as a comparative example, p-anisidine directly reacts with methanol without hydrogenation for dechlorination, and the methylation reaction is a one-section fixed bed continuous reaction. The method comprises the following specific steps:
p-anisidine and methanol are used as reactants, metal oxide catalysts A and B are used as methylation reaction catalysts, the reactants are filled into a fixed bed reactor, nitrogen flow rate is introduced at 5ml/min, the temperature is raised to 200 ℃ within 1h, and the anisidine and the methanol are added into the reactor for reaction. And after the reaction is finished, rectifying the reaction solution to obtain the N-methyl p-anisidine. The mass ratio of the methoxyaniline to the methanol and the amount of the catalyst are the same as in example one.
TABLE 1 Effect of conversion of para-anisidine
The data in table 1 show that the conversion rate of p-anisidine can be greatly improved by performing the methylation reaction after the dechlorination of the p-anisidine. Compared with the comparative examples, the conversion rates of the examples 1 to 5 are improved by 12 to 24 percent and reach 83.39 to 95.15 percent.
As can be seen from the examples 1 and 2 to 5, the two-stage fixed bed catalytic reaction is adopted, and the nitrogen is adopted between the two stages to control the reaction temperature rise, so that the reaction coking can be avoided, the conversion rate is enhanced, and the conversion rate can be improved by 7 to 12 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.