Production method of nitrotoluene

Abstract

The present invention relates to a method for producing nitrotoluene, comprising: (1) providing a first material, wherein the first material comprises sulfuric acid, nitric acid, metal nitrate and heteropoly acid; (2) providing a second material, wherein the second material comprises toluene; (3) feeding the first material and the second material into a reaction zone of a reactor to react and form nitrotoluene. The method of the present invention uses less sulfuric acid than nitric acid, and the raw material conversion rate can be as high as 98%.

Description

Technical Field

[0001] The invention relates to a method for producing nitrotoluene, and in particular to a method for continuously producing nitrotoluene by using a microchannel reactor. Background Art

[0002] Nitrotoluene has three kinds of isomers, namely, ortho-, meta- and para-nitrotoluene, and para-nitrotoluene and ortho-nitrotoluene are both important chemical materials. However, nitration reaction is a kind of fast strong exothermic reaction process, and reaction process is not easy to control. If the heat generated by reaction cannot be taken away in time, it will also cause side reaction and potential safety hazard. At present, nitrating agent is generally a mixture of concentrated nitric acid and concentrated sulfuric acid, and sulfuric acid consumption is substantially more than 3 times of nitric acid volume, and the consumption of acid is large, which can cause serious environmental pollution. Therefore, this area expects an improved method for the safe and continuous production of nitrotoluene. Summary of the invention

[0003] In order to solve the deficiencies in the prior art, the present invention provides a method for producing nitrotoluene, which specifically comprises the following steps:

[0004] (1) providing a first material, wherein the first material comprises sulfuric acid, nitric acid, a metal nitrate and a heteropoly acid;

[0005] (2) providing a second material, wherein the second material comprises toluene;

[0006] (3) Feeding the first material and the second material into a reaction zone of a reactor to react and form nitrotoluene.

[0007] In some embodiments of the present invention, the reaction temperature in the reaction zone of the reactor is set at 80-120° C., and the reaction is maintained at a constant temperature within this temperature range.

[0008] In some embodiments of the present invention, the metal nitrate comprises one or both of copper nitrate and cerium nitrate.

[0009] In some embodiments of the present invention, the heteroatom of the heteropolyacid is silicon.

[0010] In some embodiments of the present invention, the heteropolyacid comprises silicomolybdic acid.

[0011] In some embodiments of the present invention, the mass ratio of sulfuric acid to nitric acid in the first material is sulfuric acid: nitric acid = 1:1-2:1, preferably 1.1:1.

[0012] In some embodiments of the present invention, the mass ratio of metal nitrate to heteropolyacid in the first material is metal nitrate: heteropolyacid = 1-5:1, preferably 2-2.5:1.

[0013] In some embodiments of the present invention, the mass ratio of metal nitrate to nitric acid in the first material is metal nitrate: nitric acid = 2-10:100, preferably 3.2-4.5:100.

[0014] In some embodiments of the present invention, the molar ratio of nitric acid in the first material to toluene in the second material is 1.0-1.4:1, preferably 1.1:1.

[0015] In some embodiments of the present invention, the residence time of the reaction in the reactor is 1-60 seconds, preferably 8-20 seconds.

[0016] In some embodiments of the present invention, the reactor is a continuous flow reactor, and the flow rate of the first material entering the reaction zone is 20-120 ml / min, and the flow rate of the second material entering the reaction zone is 20-120 ml / min.

[0017] In some embodiments of the present invention, the reactor is selected from a tank reactor, a tubular reactor, a microchannel reactor, a high-throughput reactor, and a flow reactor.

[0018] In some embodiments of the present invention, the reactor may be a reactor combination in which the number of reactors is greater than 1, and the types of reactors selected in the reactor combination may be the same or different; when reactions occur in the reactors in the reactor combination, the reaction temperatures of the reaction zones of the reactors may be the same or different.

[0019] In the present invention, metal nitrate and heteropoly acid are used as catalysts, and the ratio of p-nitrotoluene and m-nitrotoluene can be well controlled. When copper nitrate and heteropoly acid mixture are used as catalysts, the ratio of m-nitrotoluene can reach 15%; when cerium nitrate and heteropoly acid mixture are used as catalysts, the ratio of p-nitrotoluene can reach 60%. Moreover, the microchannel reactor can enhance the mass transfer effect, and its intrinsic safety characteristics reduce the risk of producing nitrotoluene and improve the safety factor of the toluene nitration synthesis process. Lower liquid holding capacity and precise control of residence time can further reduce the probability of side reactions, making it difficult to produce dinitro and polynitro byproducts of toluene nitration. In the present invention, sulfuric acid is used in a small amount relative to nitric acid. Within a certain extent, the amount of sulfuric acid increases, the more violent the reaction, the more polynitro compounds, and the more dangerous the reaction. Relatively speaking, the less sulfuric acid, the milder the reaction, and the lower the raw material conversion rate. Compared with the traditional process, under the condition of reduced sulfuric acid, the present invention can still achieve a higher conversion rate, while the waste acid treatment amount is low, which is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a reaction formula for synthesizing nitrotoluene in one embodiment of the present invention.

[0021] Figure 2 Schematic diagram of a microchannel reactor 10 for synthesizing nitrotoluene in one embodiment of the present invention. A first material enters a reactor module 11 from a feed port 12, a second material enters a reactor module 11 from a feed port 13, and a final product is collected at an outlet 14 of the reactor. The reactor 10 includes three reaction modules 11. IPC (In-process-control) is a central control. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is now described in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0023] As used herein, the term "microchannel reactor" refers to a microreactor whose internal structure is mainly composed of micrometer-sized (usually 10-300 μm) channels.

[0024] As used herein, the term "(GC) analysis" refers to gas chromatography (GC) analysis.

[0025] As used herein, the term "(LC) analysis" refers to liquid chromatography (LC) analysis.

[0026] The methods described herein can be carried out at normal pressure or elevated pressure. The pressure in any reaction zone of the methods described herein can be 0.1-5 MPa, preferably 0.1-2 MPa, for example, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa.

[0027] Herein, reaction residence time = total volume flow rate of reaction raw materials (ml / min) / reactor internal volume (ml). The reactor internal volume is provided by the supplier of the commercially available reactor.

[0028] The conversion rate described herein = (initial amount of reactants - remaining amount of reactants) / initial amount of reactants.

[0029] Selectivity as described herein = amount of target product / (starting amount of reactants x conversion rate)

[0030] The temperature described herein refers to degrees Celsius. As required, the concentration / content / amount / number of portions described herein may be the concentration / content / amount / number of portions expressed in terms of mass, volume, mole, mass / volume, or volume / mass.

[0031] The methods described herein can be performed adiabatically or non-adiabatically.

[0032] The method described herein can be carried out under isothermal or non-isothermal conditions. In the present invention, the term "isothermal" means that the reaction temperature can fluctuate within ±5°C, preferably ±4°C, 3°C or 2°C, more preferably within 0.5°C of the above set temperature value.

[0033] The second material herein may be prepared before, simultaneously with or after the preparation of the first material.

[0034] In the present invention, the microchannel reactor can refer to the content described in CN102325589A of Corning Co., Ltd. In the present invention, the term "microchannel reactor" refers to a microreactor whose internal structure is mainly composed of micron-level (usually 10-300μm) channels. The microchannel reactor includes but is not limited to Corning G1-glass reactor and Corning G5-SiC reactor.

[0035] The reaction temperature of the microchannel reactor can be precisely controlled by a heat exchanger, and the first material and the second material enter the reactor through an injection device, and the injection device includes but is not limited to injection by pump, extrusion, penetration, injection, etc. In some embodiments, the first material and the second material can be pumped from the first material reservoir and the second material reservoir respectively by a plunger pump, and enter the microchannel reactor through a feed frame for reaction.

[0036] In the present invention, the first material and the second material can be introduced into a microchannel reactor for reaction, specifically including: allowing the first material and the second material to contact, mix, and react in the channel of the microchannel reactor, and realizing plug flow along the channel so that the reaction liquid can achieve the effect of enhanced mass transfer.

[0037] Figure 2 Corning G1-glass microchannel reactor 10 used in some specific embodiments of the present invention includes three microchannel reactor modules 11, a heat exchanger device (not marked in the figure) and an injection device (not marked in the figure). The heat exchange device includes a heat exchange passage adjacent to the reaction passage of the microchannel reactor module, which is connected to other liquid or gaseous media, and a control device located outside that can keep the medium in the heat exchange passage circulating and control its temperature. The injection device includes a plunger pump and a matching injection frame, which can pump the reactants into the microchannel reactor module. The first material is introduced into the microchannel reactor module 11 from the feed port 12, and the second material flow is introduced into the microchannel reactor module 11 from the feed port 13. After the reaction is completed, the reaction product flows out of the reactor from the discharge port 14.

[0038] In a preferred embodiment, the present invention can maintain a constant temperature reaction of the first material and the second material at a temperature between 80-160°C, preferably 100-140°C, and more preferably 110-130°C, by circulating a cooled heat control fluid around the microchannel reactor or in the microchannel reactor.

[0039] Unless otherwise specified, the raw materials used in the present invention are all industrial grade raw materials. In the embodiment, the raw material toluene can be purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd., and its purity is >99.5%; nitric acid can be purchased from Nanjing Chemical Reagent Co., Ltd., wherein the nitric acid content can reach 98%; and sulfuric acid can be purchased from Jiangsu Yongfeng Chemical Reagent Co., Ltd., wherein the sulfuric acid content can reach 98%. Copper nitrate can be purchased from Aladdin Reagent, and its purity is >99.5%; cerium nitrate can be purchased from Aladdin Reagent, and its purity is >99.5%; silicomolybdic acid can be purchased from Exploration Platform, and its purity is >97%.

[0040] General Methods

[0041] Examples 1-2 were performed using the following general procedure.

[0042] Copper nitrate, silicomolybdic acid hydrate or cerium nitrate, silicomolybdic acid hydrate are dissolved in a nitric-sulfuric acid mixture as the first material; and enter the reactor through the feed port 12, the mass ratio of sulfuric acid to nitric acid in the first material is sulfuric acid: nitric acid = 1:1-2:1, preferably 1.1:1. The mass ratio of metal nitrate and silicomolybdic acid in the first material is metal nitrate: silicomolybdic acid = 1-5:1, preferably 2-2.5:1. The mass ratio of metal nitrate and nitric acid in the first material is metal nitrate: nitric acid = 2-10:100, preferably 3.2-4.5:100. The flow rate of the first material entering the reactor is 20-120 ml / min

[0043] Pure toluene is used as the second material and enters the reactor through the feed port 13. The pump 1 for delivering the first material is set to feed at a rate of 20-50 ml / min. The flow rate of the second material entering the reactor is 20-120 ml / min.

[0044] The molar ratio of nitric acid in the first material to toluene in the second material is 1.0-1.4:1, preferably 1.1:1.

[0045] The reaction temperature in the reaction zone of the reactor is set at 80-120°C, and the reaction is maintained at a constant temperature within this temperature range.

[0046] The residence time of the reaction in the reactor is 1-120 seconds, preferably 8-20 seconds.

[0047] The reactor may be an AFR G1-Glass reactor or an AFR G5-Glass reactor manufactured by Corning Incorporated.

[0048] After the system is stable, samples are collected at the reaction outlet 14. The reaction solution is cooled by a stainless steel coil at 10-15°C and then quenched with ice water. The phases are separated, and the organic phase is washed once with water and once with saturated sodium bicarbonate to obtain a crude nitrotoluene mixture. The sample is analyzed by GC.

[0049] Example 1

[0050] 25 g of copper nitrate and 10 g of silicomolybdic acid hydrate were dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0051] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0052] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0053] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (73 ml / min).

[0054] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.8 s.

[0055] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 98.1%, including 40% of o-nitrotoluene, 15% of m-nitrotoluene, 43% of p-nitrotoluene, and 0.1% of dinitrotoluene.

[0056] Example 2

[0057] 18g of cerium nitrate and 9g of silicomolybdic acid hydrate were dissolved in 151g of water, and after the dissolution, 561g of fuming nitric acid and 494g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50°C to obtain the first material.

[0058] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0059] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0060] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (75 ml / min).

[0061] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.6 s.

[0062] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 98.5%, including 27.6% of o-nitrotoluene, 10.4% of m-nitrotoluene, 60% of p-nitrotoluene, and 0.2% of dinitrotoluene.

[0063] Comparative Example 1

[0064] 25 g of copper nitrate was dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0065] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0066] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0067] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (74 ml / min).

[0068] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.7 s.

[0069] After the system is stable, the sample collection starts, and the sample collected at the reaction outlet is analyzed by GC after 10 seconds. GC analysis shows that the conversion rate of raw material toluene is 94%, including 48% of o-nitrotoluene, 5% of m-nitrotoluene, 40% of p-nitrotoluene, and 0.2% of dinitrotoluene.

[0070] Comparative Example 2

[0071] 561 g of fuming nitric acid and 1683 g of concentrated sulfuric acid were added to 267 g of water, and the temperature was controlled not to exceed 50° C. to obtain the first material.

[0072] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0073] Pump 1 for delivering the first material was set to feed at a rate of 48 g / min (55 ml / min).

[0074] Pump 2, used to deliver the second material, was set to feed at a rate of 160 g / min (98 ml / min).

[0075] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.4 s.

[0076] After the system stabilized, the samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 82%, including 45% of o-nitrotoluene, 3% of m-nitrotoluene, 30% of p-nitrotoluene, and 1.2% of dinitrotoluene.

[0077] Comparative Example 3

[0078] 9 g of silicomolybdic acid hydrate was dissolved in 151 g of water, and 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added, and the temperature was controlled not to exceed 50° C. during the test to obtain the first material.

[0079] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0080] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0081] Pump 2, used to deliver the second material, was set to feed at a rate of 110 g / min (75 ml / min).

[0082] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.6 s.

[0083] After the system stabilized, the samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw material toluene was 92%, including 48% of o-nitrotoluene, 3% of m-nitrotoluene, 34% of p-nitrotoluene, and 6% of dinitrotoluene.

[0084] Comparative Example 4

[0085] 25 g of copper nitrate and 10 g of silicomolybdic acid hydrate were dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0086] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0087] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0088] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (73 ml / min).

[0089] The temperature of the reaction zone was set at 80° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.8 s.

[0090] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 82.1%, including 35% of o-nitrotoluene, 12.5% ​​of m-nitrotoluene, 34% of p-nitrotoluene, and 0.1% of dinitrotoluene.

[0091] Comparative Example 5

[0092] 25 g of copper nitrate and 10 g of silicomolybdic acid hydrate were dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0093] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0094] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0095] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (73 ml / min).

[0096] The temperature of the reaction zone was set at 160° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.8 s.

[0097] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 99%, including 37.3% of o-nitrotoluene, 16.2% of m-nitrotoluene, 43.5% of p-nitrotoluene, and 2.7% of dinitrotoluene.

[0098] Comparative Example 6

[0099] 25 g of copper nitrate and 10 g of silicomolybdic acid hydrate were dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0100] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0101] Pump 1 for delivering the first material was set to feed at a rate of 40 g / min (35 ml / min).

[0102] Pump 2, used to deliver the second material, was set to feed at a rate of 113 g / min (73 ml / min).

[0103] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 17.6 s.

[0104] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 20 seconds. GC analysis showed that the conversion rate of raw toluene was 86%, including 34.8% of o-nitrotoluene, 13.1% of m-nitrotoluene, 37.3% of p-nitrotoluene, and 0.2% of dinitrotoluene.

[0105] Comparative Example 7

[0106] 25 g of copper nitrate and 10 g of silicomolybdic acid hydrate were dissolved in 151 g of water, and after the dissolution, 561 g of fuming nitric acid and 494 g of concentrated sulfuric acid were added. During the test, the dissolution temperature did not exceed 50° C. To obtain the first material.

[0107] Pure toluene is used as the second material and enters the reactor through the feed port 13.

[0108] Pump 1 for delivering the first material was set to feed at a rate of 65 g / min (75 ml / min).

[0109] Pump 2, used to deliver the second material, was set to feed at a rate of 124 g / min (80 ml / min).

[0110] The temperature of the reaction zone was set at 120° C. The reactor was a G1 reactor. The internal volume of the reactor was 24 ml (3 modules) and the reaction residence time was about 9.3 s.

[0111] After the system stabilized, samples were collected, and GC analysis was performed on the samples collected at the reaction outlet after 10 seconds. GC analysis showed that the conversion rate of raw toluene was 99%, of which o-nitrotoluene accounted for 39%, m-nitrotoluene accounted for 14.8%, p-nitrotoluene accounted for 41%, and dinitrotoluene accounted for 2.5%.

[0112] The present invention has been described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art will appreciate that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention.

Claims

1. A method for producing nitrotoluene, characterized in that: The method comprises: (1) providing a first material, wherein the first material comprises sulfuric acid, nitric acid, a metal nitrate and a heteropoly acid; (2) providing a second material, wherein the second material comprises toluene; (3) feeding the first material and the second material into a reaction zone of a reactor to react and form nitrotoluene; Wherein, the metal nitrate is selected from one or both of copper nitrate and cerium nitrate; and the heteropolyacid is silicomolybdic acid.

2. The method according to claim 1, characterized in that The reaction temperature in the reaction zone of the reactor was set at 80-160°C.

3. The method according to claim 1, characterized in that The mass ratio of sulfuric acid to nitric acid in the first material is sulfuric acid: nitric acid = 1:1-2:

1.

4. The method according to claim 1, characterized in that The mass ratio of the metal nitrate to the heteropoly acid in the first material is metal nitrate:heteropoly acid=1-5:

1.

5. The method according to claim 1, characterized in that The mass ratio of metal nitrate to nitric acid in the first material is metal nitrate: nitric acid = 2-10:

100.

6. The method according to claim 1, characterized in that The molar ratio of nitric acid in the first material to toluene in the second material is 1.0-1.4:

1.

7. The method according to any one of claims 1 to 6, characterized in that: The residence time of the reaction in the reactor is 1-60 seconds.

8. The method according to any one of claims 1 to 6, characterized in that: The reactor is a continuous flow reactor, and the flow rate of the first material entering the reaction zone is 20-120 ml / min, and the flow rate of the second material entering the reaction zone is 20-120 ml / min.

9. The method according to any one of claims 1 to 6, wherein the reactor is selected from a tank reactor, a tubular reactor, a microchannel reactor, a high-throughput reactor, and a flow reactor.

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