Method for preparing 1-nitro-2-naphthol through selective nitration of 2-naphthol

Abstract

The invention discloses a method for preparing 1-nitro-2-naphthol through selective nitration of 2-naphthol. The method comprises the following steps: preparing N2O5; preparing an N2O5 solution; in an N2O5 solution system, 2-naphthol is catalyzed by ammonium phosphomolybdate supported by solid acid catalyst-silicon dioxide to be converted into 1-nitro-2-naphthol; and sequentially filtering, extracting and purifying the reaction product mixed solution to obtain the 1-nitro-2-naphthol. According to the method disclosed by the invention, an N2O5 / CH2Cl2 system is used as a nitrating agent, so that the 2-naphthol has better conversion rate and selectivity; the reaction condition is mild, and waste acid can be recycled after the reaction; the solid acid catalyst has strong B acid and small corrosivity, can replace a traditional liquid acid catalyst, and can also be recycled; the ammonium phosphomolybdate heteropolyacid is loaded on the silicon dioxide, so that the specific surface area is obviously increased, the ammonium phosphomolybdate heteropolyacid is more easily in full contact with reactants during reaction, the catalytic activity is improved, and the nitration conversion rate of 2-naphthol is greatly increased.

Description

Technical Field

[0001] The invention belongs to the technical field of drug synthesis, and particularly relates to a method for preparing 1-nitro-2-naphthol by selective nitration of 2-naphthol. Background Art

[0002] 1-Nitro-2-naphthol is mainly used as a raw material for synthesizing dyes and resins, and is a commonly used organic synthesis intermediate. There are two main methods for preparing 1-nitro-2-naphthol in the prior art: one is an oxynitration reaction, that is, in the presence of a mercury salt (catalyst), naphthalene is nitrated with nitric acid having a mass concentration of 50% to 60% to generate nitronaphthol, and its defect is that the product purity is low; the other is to synthesize 1-nitro-2-naphthol using N-acetyl-1-nitro-2-naphthylamine as a raw material, and the disadvantage is that the reaction steps are cumbersome and the preparation cost is high.

[0003] At present, the nitration reaction of aromatic compounds mainly uses high-concentration nitric acid as a nitrating agent, and phosphoric acid, sulfuric acid or hydrofluoric acid as a liquid acid catalyst. Although these process methods have strong nitration capabilities, they have problems such as difficulty in separating the product and the catalyst, difficulty in recycling the catalyst, huge amounts of waste liquid and waste gas, serious equipment corrosion and serious environmental pollution, which do not meet the development requirements of green chemistry. With the introduction of the concept of "clean chemical industry", many scientific researchers have begun to reform and update the existing nitration technology with the principle of clean production, mainly including the use of green catalysts to promote the nitration reaction, the use of nitrogen oxides as nitrating agents, etc. Nitrogen pentoxide (N2O5) is a new type of green nitrating agent. The green nitration process using N2O5 as a nitrating agent, in addition to overcoming the various shortcomings of the traditional nitration process, also has the advantages of less side reactions and the ability to nitrate acid-sensitive or water-sensitive substances. Compared with sulfuric acid, solid acid catalysts have the advantages of being reusable and having mild reaction conditions, which can effectively reduce corrosion to equipment and reduce pollution to the environment. The invention discloses a method for preparing 1-nitro-2-naphthol by selective nitration of 2-naphthol based on the advantages of dinitrogen pentoxide and solid acid catalyst, so as to provide a new direction for the synthesis of 1-nitro-2-naphthol. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol. The method uses a N2O5 / CH2Cl2 system as a nitrating agent and is applied to the regional selective nitration of 2-naphthol. Compared with the prior art, the method achieves a better conversion rate and nitration selectivity. The system has mild reaction conditions and can recycle waste acid after the reaction, thus having a good development prospect. The solid acid catalyst, ammonium phosphomolybdate supported by silicon dioxide, can well replace the traditional sulfuric acid liquid acid catalyst because the heteropoly acid has a strong B acid and is less corrosive, and can be repeatedly recycled. The solid acid catalyst, ammonium phosphomolybdate supported by silicon dioxide, is in powder form. After the heteropoly acid is supported on silicon dioxide, the specific surface area is significantly increased, and the heteropoly acid is more easily in full contact with the reactant during the reaction, thereby improving the catalytic activity thereof, thereby greatly improving the nitration conversion rate of 2-naphthol into 1-nitro 2-naphthol. The method is simple to operate, the overall operation takes a short time, is pollution-free, meets the development requirements of green chemistry, and provides a new scheme for the synthesis of 1-nitro 2-naphthol.

[0005] To achieve the above object, the technical solution of the present invention is to design a method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol, comprising the following steps:

[0006] S1: Preparation of N2O5;

[0007] S2: dissolving the N2O5 prepared in step S1 in an organic good solvent to form a N2O5 solution of a certain concentration, and storing the N2O5 solution in a low temperature environment for standby use;

[0008] S3: adding 2-naphthol and a solid acid catalyst to a reaction flask, adding a certain amount of the N2O5 solution prepared in step S2 to the reaction flask under stirring, and stirring the reaction at a certain temperature for a certain time, the solid acid catalyst used is ammonium phosphomolybdate supported by silica, the loading amount of the effective catalytic component in the solid acid catalyst is calculated by the mass ratio of MoO3 / SiO2, the loading amount of the effective catalytic component in the solid acid catalyst is 1-30%, the amount of the solid acid catalyst is 1-20% of the mass of the 2-naphthol feed, and the molar feed ratio of N2O5 to 2-naphthol is 1:1;

[0009] S4: filtering, extracting and purifying the reaction product mixture in sequence to obtain 1-nitro-2-naphthol.

[0010] The preferred technical solution is that the specific operation of step S1 is as follows: placing a three-necked flask in a low-temperature constant temperature stirring bath device below 0°C, slowly adding fuming nitric acid into the three-necked flask, slowly adding phosphorus pentoxide in batches under strong mechanical stirring, and stopping stirring when the solution becomes yellow and viscous and difficult to continue stirring, and transferring the three-necked flask to a constant temperature water bath, configuring a vacuum distillation device, heating the constant temperature water bath to a certain temperature, and collecting nitrogen pentoxide, and the mass concentration of the fuming nitric acid used is 95-98%.

[0011] A further preferred technical solution is that in step S1, the initial temperature of the constant temperature water bath is ≤5°C, the temperature of the constant temperature water bath is controlled at 20-25°C when collecting the nitrogen pentoxide fraction, and the mass concentration of the fuming nitric acid used is 98%.

[0012] Another preferred technical solution is that the specific operation of step S2 is: dissolving the nitrogen pentoxide prepared in step S1 in a dichloromethane solution at low temperature, then transferring it to a volumetric flask to make a fixed volume to form a N2O5 solution of a certain concentration, and storing the N2O5 solution in a low temperature environment below -5°C for standby use, and the molar concentration of N2O5 in the N2O5 solution is 1 to 2 mol / L.

[0013] Another preferred technical solution is that in step S3, the amount of the solid acid catalyst is 5-15% of the mass of the 2-naphthol feed, and the reaction time is 5-60 min.

[0014] A further preferred technical solution is that in the step S3, the amount of the solid acid catalyst is 10% of the mass of the 2-naphthol feed, and the reaction time is 20 min.

[0015] A further preferred technical solution is that in the step S3, the preparation method of the solid acid catalyst is: weigh an appropriate amount of ammonium molybdate and dissolve it in a 3% by mass aqueous hydrogen peroxide solution to obtain an ammonium molybdate solution; add ethyl orthosilicate, deionized water, and anhydrous ethanol to a reaction bottle in a volume ratio of 1:2:2, stir for 20 to 40 minutes at a temperature of 60 to 80°C and mix evenly, and at the same time, drop phosphoric acid and the prepared ammonium molybdate solution into the reaction bottle, the amount of phosphoric acid and ammonium molybdate solution added is determined according to the molar ratio of phosphorus: molybdenum atoms of 1:12, and after the phosphoric acid and ammonium molybdate solutions are added, continue to stir the reaction at a temperature of 60 to 80°C until a gel is generated, and place it at room temperature for aging for more than 24 hours, and dry it at a temperature of 90 to 120°C, and calcine it for 3 to 6 hours to obtain a solid acid catalyst.

[0016] A further preferred technical solution is that the specific operation of step S4 is: filtering the reaction product mixed solution and retaining the filtrate, extracting the filtrate with dichloromethane for more than 3 times, combining the extracts, taking a small amount of the extract and drying it with anhydrous sodium sulfate for chromatographic analysis, pouring most of the extract into an appropriate amount of ice water to precipitate solids, and washing the filtered filter cake with distilled water several times, recrystallizing, and drying to obtain 1-nitro-2-naphthol.

[0017] A further preferred technical solution is that in step S4: the solvent used for recrystallization is methanol.

[0018] The advantages and beneficial effects of the present invention are:

[0019] 1. A method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol of the present invention uses a N2O5 / CH2Cl2 system as a nitrating agent and is applied to the regional selective nitration of 2-naphthol. Compared with the prior art, a better conversion rate and nitration selectivity are achieved; and the system has mild reaction conditions and the waste acid can be recycled and reused after the reaction, and has a good development prospect; the solid acid catalyst used, ammonium phosphomolybdate supported by silica, can well replace the traditional sulfuric acid liquid acid catalyst because the heteropoly acid has a strong B acid and is less corrosive, and can be repeatedly recycled.

[0020] 2. The present invention discloses a method for preparing 1-nitro-2-naphthol by selective nitration of 2-naphthol. The solid acid catalyst used, ammonium phosphomolybdate supported on silica, is in powder form. After the heteropoly acid is supported on silica, the specific surface area is significantly increased, and it is easier to fully contact with the reactants during the reaction, thereby improving its catalytic activity, thereby greatly improving the nitration conversion rate of 2-naphthol to 1-nitro-2-naphthol.

[0021] 3. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol of the present invention is simple to operate, takes a short time for the overall operation, is pollution-free, meets the development requirements of green chemistry, and provides a new solution for the synthesis of 1-nitro 2-naphthol. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0023] (I) Preparation of reaction raw materials and reagents

[0024] (1) Preparation of solid acid catalyst: Weigh an appropriate amount of ammonium molybdate and dissolve it in a 3% by mass aqueous hydrogen peroxide solution to obtain an ammonium molybdate solution; add ethyl orthosilicate, deionized water and anhydrous ethanol in a volume ratio of 1:2:2 into a reaction flask, stir for 20 to 40 minutes at 60 to 80° C. and mix evenly; simultaneously, add phosphoric acid and the prepared ammonium molybdate solution dropwise into the reaction flask, wherein the amount of phosphoric acid and ammonium molybdate solution added is determined according to a phosphorus:molybdenum atomic molar ratio of 1:12; after the phosphoric acid and ammonium molybdate solution are added dropwise, continue to stir and react at 60 to 80° C. until a gel is generated, place at room temperature for aging for more than 24 hours, dry at 90 to 120° C., and calcine for 3 to 6 hours to obtain a solid acid catalyst-silicon dioxide-supported ammonium phosphomolybdate.

[0025] (2) Preparation of N2O5: Place a three-necked flask in a low-temperature constant temperature stirring bath device below 0°C, slowly add fuming nitric acid into the three-necked flask, and slowly add phosphorus pentoxide in batches under strong mechanical stirring. When the solution becomes yellow and viscous and it is difficult to continue stirring, stop stirring and transfer the three-necked flask to a constant temperature water bath pot, install a vacuum distillation device, heat the constant temperature water bath pot to a certain temperature, and collect the nitrogen pentoxide. The mass concentration of the fuming nitric acid used is 95-98%.

[0026] (3) The nitrogen pentoxide prepared in step (2) is dissolved in a dichloromethane solution at low temperature, and then transferred to a volumetric flask to form a N2O5 / CH2Cl2 solution of a certain concentration, and the N2O5 / CH2Cl2 solution is stored in a low temperature environment below -5°C for standby use, wherein the molar concentration of N2O5 in the N2O5 / CH2Cl2 solution is 1 mol / L.

[0027] (ii) A series of examples of preparing 1-nitro-2-naphthol using the method of the present invention

[0028] Example 1

[0029] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 5% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0030] Example 2

[0031] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0032] Example 3

[0033] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 15% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0034] Example 4

[0035] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 20% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0036] Detection: Using 1-nitro-2-naphthol as a standard, the filtrate obtained after drying with anhydrous sodium sulfate in Examples 1 to 4 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard for quantitative analysis. The results are shown in Table 1.

[0037] Table 1:

[0038] 2-Naphthol conversion rate (%) Selectivity (%) Example 1 100 78.9 Example 2 100 88.5 Example 3 100 82.3 Example 4 100 80.1

[0039] As can be seen from Table 1, the nitrogen pentoxide nitrating agent and silicon dioxide-loaded ammonium phosphomolybdate used in the present invention as catalysts have high catalytic activity and product selectivity for the nitration reaction of 2-naphthol, and when the loading amount reaches 10%, the selectivity of 1-nitro-2-naphthol reaches a maximum value of 88.5%, obtaining the best result.

[0040] Example 5

[0041] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 5 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0042] Example 6

[0043] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0044] Example 7

[0045] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 40 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0046] Example 8

[0047] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 60 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solid, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0048] Detection: Using 1-nitro-2-naphthol as a standard, the filtrate obtained after drying with anhydrous sodium sulfate in Examples 5 to 8 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard for quantitative analysis. The results are shown in Table 2.

[0049] Table 2:

[0050] 2-Naphthol conversion rate (%) Selectivity (%) Example 5 100 75.6 Example 6 100 88.5 Example 7 100 73.8 Example 8 100 69.5

[0051] As can be seen from Table 2, the reaction time has a certain influence on the catalytic effect of the catalyst. The nitrogen pentoxide nitrating agent and the silica-supported ammonium phosphomolybdate catalyst used in the present invention have high catalytic activity and product selectivity for the nitration reaction of 2-naphthol. When the reaction time is 20 min, the best result can be obtained.

[0052] Example 9

[0053] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.1 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0054] Example 10

[0055] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.2 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0056] Embodiment 11

[0057] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0058] Example 12

[0059] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.5 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0060] Detection: 1-nitro-2-naphthol was used as a standard substance, and the filtrate obtained after drying with anhydrous sodium sulfate in Examples 9 to 12 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard, and quantitative analysis was performed. The results are shown in Table 3.

[0061] Table 3:

[0062] 2-Naphthol conversion rate (%) Selectivity (%) Example 9 100 85.8 Example 10 100 86.7 Embodiment 11 100 88.5 Example 12 100 87.3

[0063] As can be seen from Table 3, different amounts of catalysts all showed high catalytic activity. The nitrogen pentoxide nitrating agent and silica-supported ammonium phosphomolybdate catalyst used in the present invention have high catalytic activity and product selectivity for the nitration reaction of 2-naphthol. When the catalyst dosage is 0.3 g, the best selectivity result can be obtained.

[0064] Embodiment 13

[0065] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under 0°C ice bath; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0066] Embodiment 14

[0067] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 5°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0068] Embodiment 15

[0069] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 10°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0070] Example 16

[0071] 0.1 mol 2-naphthol was added to 20 ml dichloromethane, and 0.3 g of the solid acid catalyst prepared in step (i) - ammonium phosphomolybdate supported by silica was added, wherein the loading amount of the effective catalytic component in the solid acid catalyst was 10% based on the mass ratio of MoO3 / SiO2; 1 mol / L prepared in step (i) was added dropwise with stirring under an ice bath at 15°C; N2O5 / CH2Cl2 solution, after adding N2O5 / CH2Cl2 solution, react at low temperature for 20 minutes; add ice water, filter, extract the filtrate with dichloromethane as the extractant for 4 times, combine the extracts and put them in a beaker; take a small amount of extract, dry it with anhydrous sodium sulfate, filter it, collect the filtrate, take a small amount of filtrate and detect it with high performance liquid chromatography; combine the remaining filtrate with most of the extract and pour it into an appropriate amount of ice water to precipitate solids, wash the filtered filter cake with distilled water for 2 to 3 times, recrystallize it with methanol, and dry it to obtain 1-nitro-2-naphthol.

[0072] Detection: Using 1-nitro-2-naphthol as a standard, the filtrate obtained after drying with anhydrous sodium sulfate in Examples 13 to 16 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard for quantitative analysis. The results are shown in Table 4.

[0073] Table 4:

[0074] 2-Naphthol conversion rate (%) Selectivity (%) Example 13 100 82.6 Embodiment 14 100 88.5 Embodiment 15 100 80.3 Example 16 100 73.7

[0075] It can be seen from Table 4 that the reaction temperature has a certain influence on the catalytic effect of the catalyst. The nitrogen pentoxide nitrating agent and the silica-supported ammonium phosphomolybdate catalyst used in the present invention have high catalytic activity and product selectivity for the nitration reaction of 2-naphthol. When the reaction temperature is 5°C, the best selectivity result can be obtained.

[0076] Embodiment 17

[0077] 0.1mol 2-naphthol is added to 20ml dichloromethane, and 0.3g of the solid acid catalyst prepared in step (a) - ammonium phosphomolybdate supported by silicon dioxide is added, wherein the loading amount of the effective catalytic component in the solid acid catalyst is 10% by mass ratio of MoO3 / SiO2; 1mol / LN2O5 / CCl4 solution is added dropwise with stirring under 5°C ice bath, and reacted at low temperature for 20min after the addition of N2O5 / CCl4 solution; ice water is added, suction filtered, and the filtrate is extracted 4 times with dichloromethane as an extractant, and the extracts are combined and placed in a beaker; a small amount of the extract is dried with anhydrous sodium sulfate and suction filtered, and the filtrate is collected, and a small amount of the filtrate is detected by high performance liquid chromatography; the remaining filtrate is combined with most of the extract and poured into an appropriate amount of ice water to precipitate solids, and the filter cake filtered out is washed with distilled water 2 to 3 times in sequence, recrystallized with methanol, and dried to obtain 1-nitro 2-naphthol.

[0078] Embodiment 18

[0079] 0.1mol 2-naphthol is added to 20ml dichloromethane, and 0.3g of the solid acid catalyst prepared in step (a) - ammonium phosphomolybdate supported by silicon dioxide is added, wherein the loading amount of the effective catalytic component in the solid acid catalyst is 10% by mass ratio of MoO3 / SiO2; 1mol / LN2O5 / CHCl3 solution is added dropwise with stirring under 5°C ice bath, and the reaction is carried out at low temperature for 20min after the addition of N2O5 / CHCl3 solution; ice water is added, suction filtered, and the filtrate is extracted 4 times with dichloromethane as an extractant, and the extracts are combined and placed in a beaker; a small amount of the extract is dried with anhydrous sodium sulfate and then suction filtered, and the filtrate is collected, and a small amount of the filtrate is detected by high performance liquid chromatography; the remaining filtrate is combined with most of the extract and poured into an appropriate amount of ice water to precipitate a solid, and the filter cake filtered out is washed with distilled water 2 to 3 times in sequence, recrystallized with methanol, and dried to obtain 1-nitro-2-naphthol.

[0080] Embodiment 19

[0081] 0.1mol 2-naphthol is added to 20ml dichloromethane, and 0.3g of the solid acid catalyst prepared in step (a) - ammonium phosphomolybdate supported by silicon dioxide is added, wherein the loading amount of the effective catalytic component in the solid acid catalyst is 10% in terms of the mass ratio of MoO3 / SiO2; 1mol / LN2O5 / CH2Cl2 solution is added dropwise with stirring under a 5°C ice bath, and the reaction is carried out at low temperature for 20min after the addition of the N2O5 / CH2Cl2 solution; ice water is added, suction filtered, and the filtrate is extracted 4 times with dichloromethane as an extractant, and the extracts are combined and placed in a beaker; a small amount of the extract is dried with anhydrous sodium sulfate and then suction filtered, and the filtrate is collected, and a small amount of the filtrate is detected by a high performance liquid chromatograph; the remaining filtrate is combined with most of the extract and poured into an appropriate amount of ice water to precipitate a solid, and the filter cake filtered out is washed with distilled water 2 to 3 times in turn, recrystallized with methanol, and dried to obtain 1-nitro 2-naphthol.

[0082] Embodiment 20

[0083] 0.1mol 2-naphthol is added to 20ml dichloromethane, and 0.3g of the solid acid catalyst prepared in step (a) - ammonium phosphomolybdate supported by silicon dioxide is added, wherein the loading amount of the effective catalytic component in the solid acid catalyst is 10% in terms of the mass ratio of MoO3 / SiO2; 1mol / LN2O5 / CH3NO2 solution is added dropwise with stirring under a 5°C ice bath, and the reaction is carried out at low temperature for 20min after the addition of the N2O5 / CH3NO2 solution; ice water is added, suction filtered, and the filtrate is extracted 4 times with dichloromethane as an extractant, and the extracts are combined and placed in a beaker; a small amount of the extract is dried with anhydrous sodium sulfate and then suction filtered, and the filtrate is collected, and a small amount of the filtrate is detected by a high performance liquid chromatograph; the remaining filtrate is combined with most of the extract and poured into an appropriate amount of ice water to precipitate a solid, and the filter cake filtered out is washed with distilled water 2 to 3 times in turn, recrystallized with methanol, and dried to obtain 1-nitro 2-naphthol.

[0084] Detection: Using 1-nitro-2-naphthol as a standard, the filtrate obtained after drying with anhydrous sodium sulfate in Examples 17 to 20 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard for quantitative analysis. The results are shown in Table 5.

[0085] Table 5:

[0086] 2-Naphthol conversion rate (%) Selectivity (%) Embodiment 17 100 81.7 Embodiment 18 100 84.1 Embodiment 19 100 88.5 Embodiment 20 100 86.0

[0087] It can be seen from Table 5 that the organic solvent has a certain influence on the nitration result of the reaction. The nitrogen pentoxide / organic solvent system used in the present invention can obtain the best selectivity result when the organic solvent is selected as dichloromethane.

[0088] Embodiment 21

[0089] The number of times the reaction catalyst in Example 11 was used was recorded as 1; the catalyst after the reaction in Example 11 was filtered and dried successively, and the reaction in Example 11 was repeated again, and the number of times the catalyst was used was recorded as 2; the catalyst after reuse was filtered and dried successively, and the reaction in Example 11 was repeated for the third time, and the number of times the catalyst was used was recorded as 3.

[0090] Detection: 1-nitro-2-naphthol was used as a standard substance, and the filtrate obtained after drying over anhydrous sodium sulfate in the catalytic reaction in Example 21 was analyzed by high performance liquid chromatography. The results showed that the product component in the filtrate was mainly 1-nitro-2-naphthol. Nitrobenzene was used as an internal standard, and quantitative analysis was performed. The results are shown in Table 6.

[0091] Table 6:

[0092]

[0093] It can be seen from Table 6 that after the catalyst was recycled three times, the catalytic activity did not decrease significantly, and it has good catalytic stability.

[0094] The invention discloses a method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol. The method uses a N2O5 / CH2Cl2 system as a nitrating agent and is applied to the regional selective nitration of 2-naphthol. Compared with the prior art, the method achieves a better conversion rate and nitration selectivity. The system has mild reaction conditions and can recycle waste acid after reaction, thus having a good development prospect. The solid acid catalyst, ammonium phosphomolybdate supported by silicon dioxide, can well replace the traditional sulfuric acid liquid acid catalyst because the heteropoly acid has a strong B acid and is less corrosive, and can be recycled repeatedly.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol, characterized in that: The steps are as follows: S1: Preparation of N2O5; S2: dissolving the N2O5 prepared in step S1 in an organic good solvent to form a N2O5 solution of a certain concentration, and storing the N2O5 solution in a low temperature environment for standby use; S3: adding 2-naphthol and a solid acid catalyst to a reaction flask, adding a certain amount of the N2O5 solution prepared in step S2 to the reaction flask under stirring, and stirring the reaction at a certain temperature for a certain time, the solid acid catalyst used is ammonium phosphomolybdate supported by silica, the loading amount of the effective catalytic component in the solid acid catalyst is calculated by the mass ratio of MoO3 / SiO2, the loading amount of the effective catalytic component in the solid acid catalyst is 1-30%, the amount of the solid acid catalyst is 1-20% of the mass of the 2-naphthol feed, and the molar feed ratio of N2O5 to 2-naphthol is 1:1; S4: filtering, extracting and purifying the reaction product mixture in sequence to obtain 1-nitro-2-naphthol.

2. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 1, characterized in that, The specific operation of step S1 is as follows: placing a three-necked flask in a low-temperature constant temperature stirring bath device below 0° C., slowly adding fuming nitric acid into the three-necked flask, slowly adding phosphorus pentoxide in batches under strong mechanical stirring, stopping stirring when the solution becomes yellow and viscous and it is difficult to continue stirring, and transferring the three-necked flask to a constant temperature water bath, configuring a vacuum distillation device, heating the constant temperature water bath to a certain temperature, and collecting nitrogen pentoxide, wherein the mass concentration of the fuming nitric acid used is 95-98%.

3. The method for preparing 1-nitro beta-naphthol by selective nitration of beta-naphthol as claimed in claim 2, characterized in that, In the step S1, the initial temperature of the constant temperature water bath is ≤5°C, the temperature of the constant temperature water bath is controlled at 20-25°C when collecting the nitrogen pentoxide fraction, and the mass concentration of the fuming nitric acid used is 98%.

4. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 1, characterized in that, The specific operation of step S2 is: dissolving the nitrogen pentoxide prepared in step S1 in a dichloromethane solution at low temperature, then transferring it to a volumetric flask to form a N2O5 solution of a certain concentration, and storing the N2O5 solution in a low temperature environment below -5°C for standby use. The molar concentration of N2O5 in the N2O5 solution is 1 to 2 mol / L.

5. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 1, characterized in that, In the step S3, the amount of the solid acid catalyst is 5-15% of the mass of the 2-naphthol feed, and the reaction time is 5-60 minutes.

6. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 5, characterized in that, In the step S3, the amount of the solid acid catalyst is 10% of the mass of the 2-naphthol feed, and the reaction time is 20 minutes.

7. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 6, characterized in that, In the step S3, the preparation method of the solid acid catalyst is as follows: weigh an appropriate amount of ammonium molybdate, dissolve it in a 3% by mass aqueous hydrogen peroxide solution to obtain an ammonium molybdate solution; add ethyl orthosilicate, deionized water, and anhydrous ethanol to a reaction bottle in a volume ratio of 1:2:2, stir for 20 to 40 minutes at a temperature of 60 to 80°C, and mix evenly; at the same time, drop phosphoric acid and the prepared ammonium molybdate solution into the reaction bottle, and the amount of the added phosphoric acid and ammonium molybdate solution is determined according to the molar ratio of phosphorus to molybdenum atoms of 1:12; after the phosphoric acid and ammonium molybdate solution are added, continue to stir and react at a temperature of 60 to 80°C until a gel is generated, place at room temperature for aging for more than 24 hours, and dry at a temperature of 90 to 120°C, and calcine for 3 to 6 hours to obtain a solid acid catalyst.

8. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 1, characterized in that, The specific operation of step S4 is as follows: filtering the reaction product mixed solution and retaining the filtrate, extracting the filtrate with dichloromethane for more than 3 times, combining the extracts, taking a small amount of the extracts and drying them with anhydrous sodium sulfate for chromatographic analysis, pouring most of the extracts into an appropriate amount of ice water to precipitate solids, and washing the filtered filter cake with distilled water for several times, recrystallizing, and drying to obtain 1-nitro-2-naphthol.

9. The method for preparing 1-nitro 2-naphthol by selective nitration of 2-naphthol as claimed in claim 8, characterized in that, In the step S4: the solvent used for recrystallization is methanol.

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