CN112851516A - Method for nitrifying o-xylene by using microchannel reactor - Google Patents
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
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Abstract
The invention aims to provide a method for nitrifying o-xylene by using a microchannel reactor, which comprises the following steps: introducing o-xylene and mixed acid into a microchannel reactor for nitration reaction; the mixed acid consists of nitric acid and sulfuric acid. According to the invention, the nitration method of the o-xylene by the mixed acid method of nitric acid and sulfuric acid is adopted in the microchannel reactor to carry out nitration, so that the product yield and the conversion rate are high, and the impurity content is low; particularly, after secondary nitration is adopted, the product yield and the conversion rate are obviously improved. When the concentration of the sulfuric acid is 70%, the molar ratio of the sulfuric acid to the nitric acid is 1.2:1, the molar ratio of the nitric acid to the m-xylene is 1.2:1, the total reaction time of the secondary nitration reaction is about 90s, and the reaction temperature is 100 ℃, the yield of the obtained product is up to 92.5%, the conversion rate is 99.2%, the impurity content is low, and the nitration effect is excellent. Compared with the traditional kettle type mixed acid nitration process, the nitration method has lower cost and higher safety, and has very good application prospect in the preparation of 3-nitro-o-xylene and 4-nitro-o-xylene.
Description
Technical Field
The invention belongs to the technical field of chemical synthesis, and particularly relates to a method for nitrifying o-xylene by using a microchannel reactor.
Background field of the invention
Nitro-o-xylene is an important chemical and medical intermediate product and is widely applied to the fields of medicines, pesticides, dyes, plastics, rubber auxiliaries and the like. Wherein, the 4-nitro-o-xylene is an important intermediate of riboflavin, herbicide pendimethalin, high-energy materials and high-grade organic dyes, and is also an important raw material for producing vitamin B2 by a chemical synthesis method; and 3-nitro-o-xylene is an important intermediate for synthesizing the anti-inflammatory analgesic mefenamic acid.
The nitro-o-xylene is mainly prepared from o-xylene through nitration reaction. In 1952, Kobe et al reported that ortho-xylene was nitrated with a mixed nitric-sulfuric acid comprising 79.4% sulfuric acid and fuming nitric acid, and reacted at 25 ℃ for 1 hour with a yield of 90% in the presence of 1:3 nitric acid and sulfuric acid.
In addition to the mixed acid nitration method, there is a method of conducting nitration by using nitrogen oxide, nitrate ester or the like as a nitrating agent. For example, in 1993, researchers of Suzuki et al proposed NO2-O3The non-nitric acid nitration process of (1) is generally called Kyodai nitration and reacts for 3 hours at-10 ℃ to obtain the yield of 80%. Nitrate or nitrate can also realize the nitration of o-xylene under the acidic condition, and researchers such as Smith use HNO3The nitration system of acetic anhydride and H beta zeolite as catalyst to nitrify o-xylene have high conversion rate up to 99%, but the method is easy to produce acetylation of o-xylene.
In addition, a catalyst is added in the nitration method of ortho-xylene to promote the reaction. Including ionic liquid catalysts, phase transfer catalysts, molecular sieve catalysis, metal oxide catalysis, and the like. Patent issued by researchers such as Alwar reports that ionic liquid is used as a high-efficiency catalyst, and by utilizing the advantages of solubility and selectivity of the ionic liquid, trihexyltetradecyl ditrifluoromethanesulfonate and trihexyltetradecyl ditrifluoroamide are added into a fuming nitric acid nitration o-xylene system, the conversion rate of o-xylene is 87%, researchers such as Wang in 2011 study the influence of various phase transfer catalysts on the nitration of the o-xylene by mixed acid, wherein mixed acid prepared by concentrated nitric acid and concentrated sulfuric acid is used in the nitration of the o-xylene, the reaction is carried out for 3h at 50 ℃, and the conversion rate is 99% when sodium dodecyl sulfate is used.
Although the methods for nitration of ortho-xylene are numerous, most methods are not suitable for industrial production due to the disadvantages of non-ideal conversion rate, more generated impurities, higher production cost, difficult separation of products and the like. The mixed acid method of nitric acid and sulfuric acid has great advantages due to mature production process and low production cost, and is still widely used in industry at present. However, the conventional ortho-xylene nitric-sulfuric acid mixed acid nitration kettle type process has great liquid holdup, violent reaction heat release and low heat transfer efficiency, and the generated dinitration and polynitration compounds have the characteristics of easy explosion and the like, so great potential safety hazards exist, and the solution is urgently needed.
The microchannel reactor is used for nitrating the o-xylene, so that the safety of the reaction can be improved, and the research is widely carried out. However, the prior method for nitrating ortho-xylene by using a microchannel reactor has some problems, such as: for example, the 2016 master's academic paper of Nanjing university of science and technology, the application of microchannel reactor in nitration, provides a method for preparing nitro-o-xylene by using microchannel reactor, which uses dinitrogen pentoxide as nitrating agent, and the conversion rate of o-xylene can only reach 87.6%. In order to increase the yield and the conversion rate, other catalysts need to be added into a mixed acid system or a specific microreactor needs to be used, so that the reaction cost is increased, and the industrial production is not facilitated.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for nitrifying ortho-xylene using a microchannel reactor.
The invention provides a method for nitrifying o-xylene by using a microchannel reactor, which comprises the following steps: introducing o-xylene and mixed acid into a microchannel reactor for nitration reaction; the mixed acid consists of nitric acid and sulfuric acid.
Further, the times of the nitration reaction are 1-2 times; when the nitration time is 2 times, the 2 nd nitration reaction is to introduce the reaction liquid obtained after the 1 st nitration reaction and mixed acid into a microchannel reactor, and then carry out nitration reaction;
preferably, the number of nitration reactions is 2.
Further, the microchannel reactor is a microchannel continuous flow reactor; preferably, the microchannel continuous flow reactor is a corning Lab-reactor.
Further, in each nitration reaction, the concentration of the nitric acid is 98% and the concentration of the sulfuric acid is 66-85%; preferably, the concentration of the sulfuric acid in each nitration reaction is 66-75%; more preferably, the concentration of the sulfuric acid in each nitration reaction is between 66% and 70%.
Further, when the nitration reaction time is 1 time, the concentration of the sulfuric acid is 70%; when the nitration reaction times are 2 times, the concentration of the 1 st sulfuric acid is 66-70%, and the concentration of the 2 nd sulfuric acid is 70%.
Further, in each nitration reaction, the molar ratio of the nitric acid to the sulfuric acid is (1:1) - (5: 1); the molar ratio of the nitric acid to the o-xylene is (0.5:1) - (1.5: 1);
preferably, the molar ratio of the nitric acid to the sulfuric acid in each nitration reaction is (1:1) to (1.62: 1); the molar ratio of the nitric acid to the o-xylene is (1.1:1) to (1.2: 1);
more preferably, the molar ratio of nitric acid to sulfuric acid is 1.2:1 per nitration reaction; the molar ratio of the nitric acid to the o-xylene is (1.1:1) to (1.2: 1).
Further, the temperature of each nitration reaction is 15-110 ℃; the time of each nitration reaction is 10-90 s;
preferably, the temperature of each nitration reaction is 100 ℃; the time of each nitration reaction is 15-70 s.
Further, when the number of times of nitration reaction is 1, the time of nitration reaction is 60 s; when the nitration reaction times are 2, the time of the 1 st nitration reaction is 39-62 s, and the time of the 2 nd nitration reaction is 17-40 s.
Further, when the nitration reaction times are 2 times, the time of the 1 st nitration reaction is 50-65 s, and the time of the 2 nd nitration reaction is 30-40 s;
preferably, when the number of times of nitration reaction is 2, the time of the 1 st nitration reaction is 57-61 s, and the time of the 2 nd nitration reaction is 35-49 s.
Further, after the nitration reaction, the obtained reaction liquid is quenched by ice water, and a water layer is removed, so that a product is obtained.
According to the invention, the nitration method of the o-xylene by the mixed acid method of nitric acid and sulfuric acid is adopted in the microchannel reactor to carry out nitration, so that the yield and the conversion rate of the product are high, and the impurity content is low; particularly, after secondary nitration is adopted, the yield and the conversion rate of the product are obviously improved. When the concentration of the sulfuric acid is 70%, the molar ratio of the sulfuric acid to the nitric acid is 1.2:1, the molar ratio of the nitric acid to the m-xylene is 1.2:1, the total reaction time of the secondary nitration reaction is about 90s, and the reaction temperature is 100 ℃, the yield of the obtained product is up to 92.5%, the conversion rate is 99.2%, the impurity content is low, and the nitration effect is excellent. Meanwhile, compared with the traditional kettle type mixed acid nitration process, the method for nitrating the o-xylene has lower cost and higher safety, and has very good application prospect in the preparation of the 3-nitro-o-xylene and the 4-nitro-o-xylene.
Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.
The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.
Drawings
FIG. 1 is a process flow diagram of primary nitration of ortho-xylene by using a microchannel reactor.
FIG. 2 is a process flow diagram of secondary nitration of ortho-xylene by using a microchannel reactor.
Detailed Description
The raw materials and equipment used in the embodiment of the present invention are known products and obtained by purchasing commercially available products.
1. Primary reagent
The main reagents used in the present invention and their properties are shown in table 1.
TABLE 1 Main Agents and their Properties
Example 1 method for primary nitration of ortho-xylene by using microchannel reactor
The technological process of the invention for primary nitration of ortho-xylene by using a microchannel reactor is shown in figure 1. The specific method comprises the following steps: the Corning microchannel continuous flow reactor (Corning lab-reactor, single module, liquid holding volume 2.7ml, two inlets and one outlet, revolution of heat exchange oil pump 3500) is used as the reaction equipment. Pumping mixed acid (the mixed acid consists of concentrated sulfuric acid and concentrated nitric acid, the concentration of the concentrated nitric acid is 98%, and the concentration of the concentrated sulfuric acid and the molar ratio of the concentrated sulfuric acid to the concentrated nitric acid are shown in table 2) and o-xylene into a reactor through a plunger pump for reaction, quenching the reaction liquid through ice water, and removing a water layer to obtain a product. The molar ratio of nitric acid to o-xylene, the reaction temperature and the reaction time are shown in Table 2.
The product was analyzed by gas chromatography under the following conditions:
Phase：SH-Rtx-5
Dimensions：L30m，ID0.25，DF0.25
sample injector: 290 deg.C
A detector: 290 deg.C
Temperature programming: 50 ℃ to 280 DEG C
The results of the yields of the obtained products, the conversion, the impurity contents, the ratios of the yields of 4-nitro-o-xylene and 3-nitro-o-xylene (4-position/3-position) under different reaction conditions are shown in Table 2.
TABLE 2 yield, conversion, impurity content and results for 4-position/3-position of the product obtained under different reaction conditions
The above results show that: under different sulfuric acid concentrations, molar ratios of sulfuric acid to nitric acid, molar ratios of nitric acid to o-xylene, reaction temperatures and reaction times, the yield, conversion rate, impurity content, 4-nitro-o-xylene yield and 3-nitro-o-xylene yield of products obtained by primarily nitrifying o-xylene by using the microchannel reactor are greatly different. When the concentration of sulfuric acid is 70%, the molar ratio of sulfuric acid to nitric acid is 1.62:1, the molar ratio of nitric acid to o-xylene is 1:1, the reaction temperature is 100 ℃, the reaction time is 60s, the optimal reaction condition is adopted, the yield of the product obtained by nitration is 64.6%, the conversion rate is 70.2%, the content of impurities is 5.6%, and the ratio of the yield of 4-nitro-o-xylene to the yield of 3-nitro-o-xylene is 0.84. When the reaction temperature exceeds 100 ℃, the nitric acid has obvious decomposition phenomenon, generates a large amount of gas and is not beneficial to the reaction.
Example 2 method for secondary nitration of ortho-xylene by using microchannel reactor
The technological process of the invention for secondary nitration of ortho-xylene by using a microchannel reactor is shown in figure 2. The specific method comprises the following steps: the Corning microchannel continuous flow reactor (Corning lab-reactor, single module, liquid holding volume 2.7ml, two inlets and one outlet, revolution of heat exchange oil pump 3500) is used as the reaction equipment.
For the first nitration, the o-xylene and the mixed acid of nitric acid and sulfuric acid pass through a first reaction module to obtain a first nitration reaction liquid: nitric-sulfuric mixed acid (prepared from concentrated nitric acid with the concentration of 98% and sulfuric acid with the concentration shown in table 3 according to the corresponding molar ratio shown in table 3) and o-xylene are pumped into a reactor through a plunger pump to react, so as to obtain primary nitration reaction liquid. The first nitration reaction temperature was 100 ℃ and the molar ratio of nitric acid to o-xylene and the reaction time were as shown in Table 3.
And (3) second nitration: and (3) allowing the primary nitration reaction liquid to enter a second reaction module, simultaneously pumping mixed acid (prepared from concentrated nitric acid with the concentration of 98% and sulfuric acid with the concentration shown in table 4 according to the corresponding molar ratio shown in table 4) into the second reaction module, reacting, quenching the reaction liquid by using ice water, and removing a water layer to obtain the product. The temperature of the second nitration reaction was 100 ℃, and the molar ratio of nitric acid to o-xylene in the mixed acid and the reaction time were as shown in table 4.
The product was analyzed by gas chromatography under the following conditions:
Phase：SH-Rtx-5
Dimensions：L30m，ID0.25，DF0.25
sample injector: 290 deg.C
A detector: 290 deg.C
Temperature programming: 50 ℃ to 280 DEG C
The results of conversion, yield, impurity content, ratio of 4-nitro-o-xylene yield to 3-nitro-o-xylene yield (4-position/3-position) of the product obtained under different reaction conditions after the second nitration are shown in Table 4.
TABLE 3 conditions of the first nitration
TABLE 4 conditions and results of the second nitration
The above results show that: after the secondary nitration, the yield and the conversion rate of the obtained product nitro-o-xylene are obviously improved compared with the primary nitration. When the concentration of the sulfuric acid obtained by the two-time nitration is 70-75%, or the concentration of the nitric acid obtained by the first nitration is 66%, the concentration of the nitric acid obtained by the second nitration is 70%, the molar ratio of the sulfuric acid obtained by the two-time nitration to the nitric acid is (1:1) - (1.2:1), and the molar ratio of the nitric acid obtained by the two-time nitration to the o-xylene is (1.1:1) - (1.2:1), the yield of the nitro-o-xylene is more than 85%, and the conversion rate is more than 95%. In particular, the molar ratio of the nitro group to the o-xylene is adjusted to 1.2:1 or the strength of the sulfuric acid of the first nitration is weakened to 66 percent, and the yield can reach more than 92 percent. The optimal reaction conditions are that when the concentration of sulfuric acid obtained by twice nitration is 70%, the molar ratio of sulfuric acid to nitric acid obtained by twice nitration is 1.2:1, and the molar ratio of nitric acid obtained by twice nitration to o-xylene is 1.2:1 (test number is 12), the yield of nitro-o-xylene is 92.5%, the conversion rate is as high as 99.2%, and the impurity content is less than 7%.
In conclusion, the invention nitrifies the o-xylene by adopting a nitration method of a mixed acid of nitric acid and sulfuric acid method in the microchannel reactor, the yield and the conversion rate of the product are high, and the impurity content is low; particularly, after secondary nitration is adopted, the yield and the conversion rate of the product are obviously improved. When the concentration of the sulfuric acid is 70%, the molar ratio of the sulfuric acid to the nitric acid is 1.2:1, the molar ratio of the nitric acid to the m-xylene is 1.2:1, the total reaction time of the secondary nitration reaction is about 90s, and the reaction temperature is 100 ℃, the yield of the obtained product is up to 92.5%, the conversion rate is 99.2%, the impurity content is low, and the nitration effect is excellent. Meanwhile, compared with the traditional kettle type mixed acid nitration process, the method for nitrating the o-xylene has lower cost and higher safety, and has very good application prospect in the preparation of the 3-nitro-o-xylene and the 4-nitro-o-xylene.
Claims (10)
1. A method for nitrifying o-xylene by using a microchannel reactor is characterized by comprising the following steps: it comprises the following steps: introducing o-xylene and mixed acid into a microchannel reactor for nitration reaction; the mixed acid consists of nitric acid and sulfuric acid.
2. The method of claim 1, wherein: the times of the nitration reaction are 1-2 times; when the nitration time is 2 times, the 2 nd nitration reaction is to introduce the reaction liquid obtained after the 1 st nitration reaction and mixed acid into a microchannel reactor, and then carry out nitration reaction;
preferably, the number of nitration reactions is 2.
3. The method of claim 1, wherein: the microchannel reactor is a microchannel continuous flow reactor; preferably, the microchannel continuous flow reactor is a corning Lab-reactor.
4. The method of claim 1, wherein: in each nitration reaction, the concentration of the nitric acid is 98 percent, and the concentration of the sulfuric acid is 66-85 percent; preferably, the concentration of the sulfuric acid in each nitration reaction is 66-75%; more preferably, the concentration of the sulfuric acid in each nitration reaction is between 66% and 70%.
5. The method of claim 4, wherein: when the nitration reaction frequency is 1 time, the concentration of the sulfuric acid is 70 percent; when the nitration reaction times are 2 times, the concentration of the 1 st sulfuric acid is 66-70%, and the concentration of the 2 nd sulfuric acid is 70%.
6. The method of claim 1, wherein: in each nitration reaction, the molar ratio of the nitric acid to the sulfuric acid is (1:1) - (5: 1); the molar ratio of the nitric acid to the o-xylene is (0.5:1) - (1.5: 1);
preferably, the molar ratio of the nitric acid to the sulfuric acid in each nitration reaction is (1:1) to (1.62: 1); the molar ratio of the nitric acid to the o-xylene is (1.1:1) to (1.2: 1);
more preferably, the molar ratio of nitric acid to sulfuric acid is 1.2:1 per nitration reaction; the molar ratio of the nitric acid to the o-xylene is (1.1:1) to (1.2: 1).
7. The method of claim 1, wherein: the temperature of each nitration reaction is 15-110 ℃; the time of each nitration reaction is 10-90 s;
preferably, the temperature of each nitration reaction is 100 ℃; the time of each nitration reaction is 15-70 s.
8. The method of claim 7, wherein: when the nitration reaction frequency is 1 time, the nitration reaction time is 60 s; when the nitration reaction times are 2, the time of the 1 st nitration reaction is 39-62 s, and the time of the 2 nd nitration reaction is 17-40 s.
9. The method of claim 8, wherein: when the nitration reaction times are 2, the time of the 1 st nitration reaction is 50-65 s, and the time of the 2 nd nitration reaction is 30-40 s;
preferably, when the number of times of nitration reaction is 2, the time of the 1 st nitration reaction is 57-61 s, and the time of the 2 nd nitration reaction is 35-49 s.
10. The method of claim 1, wherein: after the nitration reaction, the obtained reaction solution is quenched by ice water, and a water layer is removed to obtain a product.
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