Method for preparing p-benzoquinone dioxime by using microchannel reactor

Abstract

The invention provides a method for preparing p-benzoquinone dioxime by using a microchannel reactor. The method comprises the following steps: respectively introducing a sodium nitrite aqueous solution and a hydrochloric acid aqueous solution into a first microchannel reactor, and reacting to obtain a mixed solution A; respectively introducing an ethanol or chloroform solution of phenol and the mixed solution A into a second microchannel reactor, and carrying out nitrosation reaction to obtain a mixed solution B; respectively introducing the mixed solution B and an aqueous solution of hydroxylamine hydrochloride into a third microchannel reactor, and carrying out oximation reaction to obtain a mixed solution C; and carrying out reduced pressure distillation on the mixed solution C, centrifuging the obtained residual solution, and drying. The method disclosed by the invention is high in safety, high in production efficiency and high in reaction conversion rate, and the obtained product is stable in quality and high in yield and purity; meanwhile, the used organic solvent ethanol can be recycled and reused, and the generated waste salt is single sodium chloride salt and can be subjected to resource utilization.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis and preparation of p-benzoquinone dioxime, and in particular to a method for preparing p-benzoquinone dioxime by using a microchannel reactor. Background Art

[0002] 4-Benzoquinone dioxime is a cross-linking agent with excellent performance. It is easy to disperse in the rubber compound, has a fast vulcanization speed, has high tensile strength of the vulcanized rubber, is heat-resistant, weather-resistant, ozone-resistant, and has good electrical insulation properties. It is widely used in the rubber industry. 4-Benzoquinone dioxime can be used as an inhibitor of acrylic acid, which can improve the thermal resistance of polyester fiber tire cord. 4-Benzoquinone dioxime can also be used as an adhesive for hot-melt connection between metal and glass, a regulator for cross-linking of olefin copolymers, an organic monomer stabilizer, and a self-vulcanizing adhesive. It has an activation effect on oxidants. 4-Benzoquinone dioxime is particularly suitable for butyl rubber, natural rubber, ethylene-propylene rubber, styrene-butadiene rubber, and polysulfide rubber with high tensile strength and fast vulcanization speed. However, the critical temperature of 4-Benzoquinone dioxime is relatively low, and it has a tendency to scorch. Adding certain scorch retardants (such as phthalic anhydride, scorch retardant NA) and accelerators (such as thiuram, thiazoles, and dithiocarbamates) can effectively improve operational safety. At the same time, benzoquinone dioxime is polluting, and about five parts of titanium dioxide can be added to prevent or improve the pollution.

[0003] In recent years, the methods for synthesizing p-benzoquinone dioxime mainly include:

[0004] The first method: at 0°C and in the presence of a certain concentration of sulfuric acid, sodium nitrite reacts with phenol dissolved in a 30% NaOH solution to produce p-benzoquinone monoxime, and then the obtained p-benzoquinone monoxime is added to hydroxylamine for oximation to produce the final product p-benzoquinone dioxime. The purity and yield of the product are limited by this synthesis method, and the purity is generally ≤90%, containing more impurities, and the yield is generally ≤60%. Specifically, 1) the nitrous acid generated by sodium nitrite in contact with acid is extremely unstable, and it is very easy to disproportionate and decompose when heated, illuminated or in contact with air, generating disproportionation products nitric acid and nitric oxide, as well as decomposition products dinitrogen trioxide, and at the same time, dinitrogen trioxide is rapidly decomposed into nitric oxide and nitrogen dioxide, thereby greatly reducing the yield and quality of p-benzoquinone dioxime. 2) During the nitrosation reaction to generate p-benzoquinone monoxime, the air in the reactor will also oxidize part of the p-benzoquinone monoxime to generate resin, which affects the quality of p-benzoquinone monoxime and further affects the quality of p-benzoquinone dioxime.

[0005] The second method is to use p-benzoquinone and hydroxylamine hydrochloride as raw materials, calcium carbonate as catalyst, and catalytically synthesize p-benzoquinone dioxime in one step at a certain temperature. Since p-benzoquinone is an absorptive crystalline solid, it is very easy to be adsorbed to the human body during use, causing discomfort to the human body, which is not conducive to industrial production. In addition, the p-benzoquinone dioxime synthesized by this method has a darker appearance and a lower purity. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing p-benzoquinone dioxime using a microchannel reactor. The method of the present invention has high safety, high production efficiency, high reaction conversion rate, stable product quality, high yield and purity; at the same time, the organic solvent ethanol used can be recycled and reused, and the waste salt generated is a single sodium chloride salt, which can be used as a resource; the synthesis method of the present invention overcomes the problems of low raw material utilization, many side reactions, high production energy consumption, poor safety, low product yield and purity in traditional processes.

[0007] The technical solution proposed by the present invention is:

[0008] A method for preparing p-benzoquinone dioxime using a microchannel reactor comprises the steps of:

[0009] 1) sodium nitrite aqueous solution and hydrochloric acid aqueous solution are respectively introduced into a first microchannel reactor to obtain a mixed solution A containing nitrous acid through reaction;

[0010] 2) the ethanol or chloroform solution of phenol and the mixed solution A are respectively introduced into the second microchannel reactor to obtain a mixed solution B containing p-benzoquinone monoxime through a nitrosation reaction;

[0011] 3) The mixed solution B and the aqueous solution of hydroxylamine hydrochloride are respectively introduced into the third microchannel reactor to obtain a mixed solution C containing p-benzoquinone dioxime through oximation reaction;

[0012] 4) The mixed solution C is distilled under reduced pressure, the obtained steam is condensed to recover ethanol, and the obtained residual liquid is centrifuged and dried to obtain p-benzoquinone dioxime.

[0013] According to the present invention, in step 1), step 2) and step 3), the microchannel reactors are all microchannel reactors reported in the prior art, also known as microreactors, and the materials flow continuously in the microchannel reactors. In the present invention, the microchannel reactor used adopts light-shielding measures to avoid the disproportionation and decomposition of the benzoquinone monoxime generated by the nitrosation reaction under the influence of light. The first microchannel reactor, the second microchannel reactor, and the third microchannel reactor of the present invention are sequentially connected in series through pipelines.

[0014] Preferably according to the present invention, in step 1), the mass fraction of the sodium nitrite aqueous solution is 50% to 60%, and the mass fraction of the hydrochloric acid aqueous solution is 20% to 30%.

[0015] Preferably according to the present invention, in step 1), the sodium nitrite aqueous solution and the hydrochloric acid aqueous solution are cooled to 3°C to 5°C before being introduced into the first microchannel reactor.

[0016] Preferably according to the present invention, in step 1), the introduction rate of the sodium nitrite aqueous solution and the hydrochloric acid aqueous solution is 16 to 35 g / min.

[0017] Preferably according to the present invention, in step 1), in the first microchannel reactor, the molar ratio of sodium nitrite to hydrochloric acid is 1:(1-1.2).

[0018] According to the preferred embodiment of the present invention, in step 1), in the first microchannel reactor, the reaction temperature is 3°C to 10°C, the reaction residence time is 5 to 15 minutes, and the reaction is carried out in the dark and under the protection of an inert gas. Preferably, the inert gas is nitrogen or argon.

[0019] According to the present invention, in step 1), the reaction in the first microchannel reactor is:

[0020] NaNO2+HCl→HNO2+NaCl

[0021] Preferably according to the present invention, in step 2), the mass ratio of phenol to ethanol or chloroform is 1:(1-2).

[0022] Preferably according to the present invention, in step 2), the introduction rate of the ethanol or chloroform solution of phenol and the mixed solution A is 12 to 26 g / min.

[0023] Preferably according to the present invention, in step 2), in the second microchannel reactor, the theoretical amount of nitrous acid and the amount of phenol in the mixed solution A are in a ratio of (1 to 1.1):1.

[0024] Preferably according to the present invention, in step 2), the ethanol or chloroform solution of phenol and the mixed solution A are cooled to 0°C to 2°C before being introduced into the second microchannel reactor.

[0025] According to the preferred embodiment of the present invention, in step 2), in the second microchannel reactor, the reaction temperature is 0°C to 5°C, the reaction residence time is 10 to 20 minutes, and the reaction is carried out under light-proof and inert gas protection. Preferably, the inert gas is nitrogen or argon. This low-temperature reaction is conducive to reducing the occurrence of side reactions and improving the selectivity of raw materials.

[0026] According to the present invention, in step 2), the reaction in the second microchannel reactor is:

[0027]

[0028] Preferably according to the present invention, in step 3), the concentration of the aqueous solution of hydroxylamine hydrochloride is 50% to 60%.

[0029] Preferably according to the present invention, in step 3), the mixed solution B and the aqueous solution of hydroxylamine hydrochloride are preheated to 50° C. to 60° C. before being introduced into the third microchannel reactor.

[0030] Preferably according to the present invention, in step 3), the introduction rate of the mixed solution B and the aqueous solution of hydroxylamine hydrochloride is 9 to 45 g / min.

[0031] Preferably according to the present invention, in step 3), in the third microchannel reactor, the molar ratio of hydroxylamine hydrochloride to the phenol conversion product in the mixed solution B is (1-1.2):1.

[0032] Preferably, in step 3), in the third microchannel reactor, the reaction temperature is 60°C to 75°C, the reaction residence time is 10 to 20 minutes, and the reaction is carried out in the dark and under the protection of an inert gas. Preferably, the inert gas is nitrogen or argon.

[0033] According to the present invention, in step 3), the reaction in the third microchannel reactor is:

[0034]

[0035] Preferably according to the present invention, in step 4), the temperature of the reduced pressure distillation is 45° C. to 60° C.; and the time of the reduced pressure distillation is 0.5 h to 1.5 h.

[0036] Preferably according to the present invention, in step 4), the drying temperature is 60° C. to 85° C., and the drying time is 0.5 h to 2 h.

[0037] The methods and devices not described in detail in the present invention are all prior art and will not be described in detail.

[0038] The technical features and beneficial effects of the present invention are as follows:

[0039] (1) The present invention uses sodium nitrite and dilute hydrochloric acid to react at low temperature to first generate a nitrous acid solution, and then the nitrous acid solution and phenol directly undergo a nitrosation reaction to generate p-benzoquinone monoxime. Compared with the traditional synthesis method of mixing phenol, liquid caustic soda and sodium nitrite solution and then adding sulfuric acid solution, this synthesis method has better reaction activity, higher synthesis efficiency and conversion rate.

[0040] (2) In the present invention, nitrous acid is directly used as a nitrosating agent to replace the sodium nitrite in the conventional process. In the nitrous acid solution synthesis process and the nitrosation reaction process, a microreactor is used and the reaction speed and reaction temperature are strictly controlled to suppress the disproportionation and decomposition of nitrous acid. However, when a common reactor is used to carry out the reaction, even if it is carried out under light protection and inert gas protection, the nitrous acid solution synthesis process is slow, and disproportionation and decomposition are very likely to occur, resulting in a low yield and purity of the target product.

[0041] (3) In the present invention, ethanol or chloroform is used as the organic solvent of phenol, and can be used as the solvent of miscible phenol and nitrous acid solution in nitrosation reaction, thereby improving the dispersibility of reaction system, accelerating the reaction rate, shortening the reaction time, and making the reaction more complete. In addition, the organic solvent ethanol or chloroform can be recovered after distillation and condensation, thereby improving production efficiency, improving the utilization rate of raw materials, and helping to reduce production cost.

[0042] (4) The present invention uses 20% to 30% hydrochloric acid solution as the raw material for synthesizing nitrous acid solution. This is because when the concentration of the hydrochloric acid solution is high, the generated nitrous acid solution is easy to decompose. When the concentration of the hydrochloric acid solution is low, the nitrosation reaction efficiency and conversion rate in the second microchannel reactor are low, and the quality and yield of the synthesized product are poor. In addition, the reaction by-product is sodium chloride, which can be converted into a single salt together with the by-product hydrogen chloride of the oximation reaction and then produced and utilized as a resource.

[0043] (5) The entire reaction in the present invention needs to be carried out under the protection of inert gas and light-proof conditions to avoid contact between the intermediate materials and air. This is because the p-benzoquinone mono-oxime generated by the nitrous acid and oximation reaction is unstable and is easily decomposed by temperature, light, air, etc., or undergoes disproportionation reaction to generate quinone substances and oxidation to generate resin. This avoids the occurrence of side reactions and improves the conversion rate and quality of p-benzoquinone dioxime.

[0044] (6) The present invention performs a cooling treatment before the raw material solution enters the first microchannel reactor and the second microchannel reactor. On the one hand, it avoids the disproportionation and decomposition of nitrous acid due to heat, and on the other hand, it helps to improve the reaction efficiency and make the reaction more complete and thorough.

[0045] (7) The present invention adopts microchannel reaction technology, which has high production efficiency, high reaction conversion rate, few side reactions, and stable quality of the target product. At the same time, the microchannel production technology is used to more accurately control the temperature of the reaction process, avoiding the occurrence of local overheating. In addition, the use of this production method is highly safe, with few production risks, which is conducive to achieving essential production safety.

[0046] (8) The present invention can successfully complete the work that cannot be completed under the conventional route by controlling the material introduction ratio and temperature, shortening the reaction time, increasing the selectivity of the target product, increasing the reaction conversion rate, and achieving stable and reliable product quality, which is conducive to large-scale industrial production.

[0047] (9) Compared with existing synthesis methods, the synthesis method of the present invention has less waste output, shorter reaction time, higher efficiency and lower production cost; the synthesis method is simple and easy, with mild conditions and high safety, and the target product has high yield and purity, and is easy to be mass-produced industrially. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] In order to further understand the present invention, a method for preparing p-benzoquinone dioxime using a microchannel reactor provided by the present invention is described in detail below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0050] In the embodiment, the microchannel reactor used is composed of a first microchannel reactor, a second microchannel reactor, and a third microchannel reactor connected in series in sequence through a pipeline. The microchannel reactor is protected from light.

[0051] Example 1

[0052] A method for preparing p-benzoquinone dioxime using a microchannel reactor comprises the following steps performed in sequence:

[0053] (1) A 50% sodium nitrite aqueous solution and a 25% hydrochloric acid aqueous solution were cooled to 5°C respectively. Under the regulation of a flow meter, a 50% sodium nitrite aqueous solution was introduced into the first microchannel reactor at a rate of 20.11 g / min, and a 25% hydrochloric acid aqueous solution was introduced into the first microchannel reactor at a rate of 22.94 g / min. The molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor was controlled to be 1:1.08, the reaction temperature was controlled at 8°C, the residence time was 7 min, and the reaction was carried out in the dark and under nitrogen protection to obtain a mixed solution A;

[0054] (2) The anhydrous ethanol solution of phenol with a mass fraction of 48.45% and the mixed solution A were cooled to 2° C. respectively. Under the regulation of the flow meter, the mixed solution A was introduced into the second microchannel reactor at a rate of 20.09 g / min, and the anhydrous ethanol solution of phenol was introduced into the second microchannel reactor at a rate of 12.93 g / min. The theoretical amount of nitrous acid and the amount of phenol in the mixed solution A in the second microchannel reactor were controlled to be 1.02:1. The reaction temperature was controlled at 5° C., the residence time was 15 min, and the reaction was carried out in the dark and under nitrogen protection to obtain a mixed solution B;

[0055] (3) Preheating the mixed solution B and the 50% by mass hydroxylamine hydrochloride aqueous solution to 60° C. respectively; passing the obtained mixed solution B into the third microchannel reactor at a rate of 33.02 g / min under the regulation of a flow meter, and simultaneously passing the 50% by mass hydroxylamine hydrochloride aqueous solution into the third microchannel reactor at a rate of 9.73 g / min, controlling the molar ratio of hydroxylamine hydrochloride in the third microchannel reactor to the phenol conversion product in the mixed solution B to be 1.05:1, controlling the reaction temperature to be 65° C., the residence time to be 15 min, and the reaction to be carried out in the dark and under nitrogen protection to obtain a mixed solution C;

[0056] (4) The obtained mixed solution C is subjected to reduced pressure distillation at 50° C. for 1 h, the steam is condensed to recover anhydrous ethanol, and the remaining liquid is evaporated, centrifuged, and dried at 70° C. for 1 h to obtain the final p-benzoquinone dioxime product.

[0057] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Example 1 was 92.99%, the appearance was light grey powder, the purity was 99.832 wt %, and the DSC Peak point was 254.71° C.

[0058] Example 2

[0059] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "a 25% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 22.94 g / min" is replaced by "a 25% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 21.90 g / min", and the molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor is controlled to be 1:1.03; other steps and conditions are the same as in Example 1.

[0060] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Example 2 was 92.33%, the appearance was light grey powder, the purity was 99.846 wt %, and the DSC Peak point was 254.46° C.

[0061] Example 3

[0062] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "a 25% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 22.94 g / min" is replaced by "a 20% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 28.68 g / min", and the molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor is controlled to be 1:1.08; other steps and conditions are the same as in Example 1.

[0063] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Example 3 was 92.61%, the appearance was light grey powder, the purity was 99.801wt%, and the DSC Peak point was 253.14°C.

[0064] Example 4

[0065] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "a 50% by mass aqueous solution of sodium nitrite is introduced into the first microchannel reactor at a rate of 20.11 g / min" is replaced by "a 60% by mass aqueous solution of sodium nitrite is introduced into the first microchannel reactor at a rate of 16.76 g / min", and the molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor is controlled to be 1:1.08; other steps and conditions are the same as in Example 1.

[0066] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Example 4 was 92.46%, the appearance was light grey powder, the purity was 99.825wt%, and the DSC Peak point was 253.89°C.

[0067] Example 5

[0068] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "a 25% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 22.94 g / min" is replaced by "a 25% by mass aqueous solution of hydrochloric acid is introduced into the first microchannel reactor at a rate of 27.53 g / min", and the molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor is controlled to be 1:1.29; other steps and conditions are the same as in Example 1.

[0069] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Example 5 was 92.90%, the appearance was light grey powder, the purity was 99.817 wt %, and the DSC Peak point was 254.58° C.

[0070] Example 6

[0071] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "the reaction temperature is controlled at 8°C and the residence time is 7 minutes" is replaced by "the reaction temperature is controlled at 10°C and the residence time is 15 minutes"; the other steps and conditions are the same as in Example 1.

[0072] After detection and measurement, the yield of p-benzoquinone dioxime obtained in Example 6 was 91.01%, the appearance was light grey powder, the purity was 99.618 wt%, and the DSC Peak point was 253.52°C.

[0073] Example 7

[0074] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (2), "residence time is 15 min" is replaced by "residence time is 20 min"; other steps and conditions are the same as in Example 1.

[0075] After detection and measurement, the yield of p-benzoquinone dioxime obtained in Example 7 was 92.28%, the appearance was light grey powder, the purity was 99.822 wt%, and the DSC Peak point was 254.06°C.

[0076] Example 8

[0077] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (2), the "48.45% by mass phenol anhydrous ethanol solution" is replaced by "48.45% by mass phenol chloroform solution"; the other steps and conditions are the same as in Example 1.

[0078] After detection and measurement, the yield of p-benzoquinone dioxime obtained in Example 8 was 91.26%, the appearance was light grey powder, the purity was 99.786 wt%, and the DSC Peak point was 253.27°C.

[0079] Comparative Example 1

[0080] A method for preparing p-benzoquinone dioxime using a microchannel reactor is as described in Example 1, except that: in step (1), "cooling the 50% sodium nitrite aqueous solution and the 25% hydrochloric acid aqueous solution to 5°C respectively" and in step (2), "cooling the 48.45% phenol anhydrous ethanol solution and mixed solution A to 2°C respectively." are replaced by "keeping the 50% sodium nitrite aqueous solution and the 25% hydrochloric acid aqueous solution at room temperature" and "keeping the 48.45% phenol anhydrous ethanol solution at room temperature, and the temperature of the mixed solution A is not treated in any way"; other steps and conditions are the same as in Example 1.

[0081] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 1 was 63.08%, the appearance was black powder, the purity was 88.619wt%, and the DSC Peak point was 245.92°C.

[0082] Comparative Example 2

[0083] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Example 1, except that: in step (1), "a 25% hydrochloric acid aqueous solution by mass" and "simultaneously introducing a 25% hydrochloric acid aqueous solution by mass into the first microchannel reactor at a rate of 22.94 g / min" are replaced by "a 36% hydrochloric acid aqueous solution by mass" and "simultaneously introducing a 36% hydrochloric acid aqueous solution by mass into the first microchannel reactor at a rate of 15.93 g / min", and the molar ratio of sodium nitrite to hydrochloric acid in the first microchannel reactor is controlled to be 1:1.08; other steps and conditions are the same as in Example 1.

[0084] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 2 was 50.14%, the appearance was black powder, the purity was 84.325wt%, and the DSC Peak point was 229.86°C.

[0085] Comparative Example 3

[0086] A method for preparing p-benzoquinone dioxime using a microchannel reactor comprises the steps of:

[0087] (1) 94 g of phenol was dissolved in 100 g of anhydrous ethanol, and the mixture was cooled to 5° C. with a 50% sodium nitrite aqueous solution and a 25% hydrochloric acid aqueous solution. Under the regulation of a flow meter, a 48.45% phenol anhydrous ethanol solution was introduced into the first microchannel reactor at a rate of 12.93 g / min, and a 50% sodium nitrite aqueous solution and a 25% hydrochloric acid aqueous solution were introduced into the first microchannel reactor at a rate of 9.38 g / min and a 25% hydrochloric acid aqueous solution were introduced into the first microchannel reactor at a rate of 10.71 g / min. The molar ratio of phenol, sodium nitrite and hydrochloric acid in the first microchannel reactor was controlled to be 1:1.02:1.1, the reaction temperature was controlled at 5° C., the residence time was 15 min, and the reaction was carried out in the dark and under nitrogen protection to obtain a mixed solution A;

[0088] (2) Preheating the mixed solution A and a 50% by mass aqueous solution of hydroxylamine hydrochloride to 60° C. respectively; passing the obtained mixed solution A into the second microchannel reactor at a rate of 33.02 g / min under the regulation of a flow meter, and simultaneously passing the 50% by mass aqueous solution of hydroxylamine hydrochloride into the second microchannel reactor at a rate of 9.73 g / min, controlling the molar ratio of hydroxylamine hydrochloride in the second microchannel reactor to the phenol conversion product in the mixed solution B to be 1.05:1, controlling the reaction temperature to be 65° C., the residence time to be 15 min, and performing the reaction in a light-proof and nitrogen-protected environment to obtain a mixed solution B;

[0089] (3) The obtained mixed solution B is subjected to reduced pressure distillation at 50° C. for 1 h, the steam is condensed to recover anhydrous ethanol, and the remaining liquid is evaporated, centrifuged, and dried at 70° C. for 1 h to obtain the final p-benzoquinone dioxime product.

[0090] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 3 was 51.78%, the appearance was black powder, the purity was 81.784wt%, and the DSC Peak point was 231.67°C.

[0091] Comparative Example 4

[0092] A method for preparing p-benzoquinone dioxime using a microchannel reactor is as described in Comparative Example 3, except that:

[0093] In step (1), “94 g of phenol was dissolved in 100 g of anhydrous ethanol” and “the anhydrous ethanol solution of phenol was introduced into the first microchannel reactor at a rate of 12.93 g / min under the regulation of a flow meter” are replaced by “94 g of phenol was dissolved in 125 g of a 32% sodium hydroxide aqueous solution” and “the sodium hydroxide aqueous solution of phenol was introduced into the first microchannel reactor at a rate of 14.60 g / min under the regulation of a flow meter”;

[0094] Step (3) is as follows: the obtained mixed solution B is filtered and dried at 70° C. for 1 hour to obtain the final p-benzoquinone dioxime product.

[0095] The other steps and conditions are the same as those in Comparative Example 3.

[0096] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 4 was 84.20%, the appearance was light grey powder, the purity was 99.761wt%, and the DSC Peak point was 253.65°C.

[0097] Comparative Example 5

[0098] A method for preparing p-benzoquinone dioxime using a microchannel reactor, as described in Comparative Example 4, except that: in step (1), "25% hydrochloric acid aqueous solution" and "25% hydrochloric acid aqueous solution by mass is introduced into the first microchannel reactor at a rate of 10.71 g / min" are replaced by "25% sulfuric acid aqueous solution" and "25% sulfuric acid aqueous solution by mass is introduced into the first microchannel reactor at a rate of 28.75 g / min"; other steps and conditions are the same as Comparative Example 4.

[0099] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 5 was 86.69%, the appearance was light grey powder, the purity was 99.653 wt%, and the DSC Peak point was 253.74°C.

[0100] Comparative Example 6

[0101] A method for preparing p-benzoquinone dioxime comprises the following steps performed in sequence:

[0102] (1) A 50% sodium nitrite aqueous solution and a 25% hydrochloric acid aqueous solution were cooled to 5° C. respectively, added to a reaction kettle, the molar ratio of sodium nitrite to hydrochloric acid was 1:1.08, the reaction temperature was controlled at 8° C., stirred for 2 h, and the reaction was carried out in a dark and nitrogen atmosphere to obtain a mixed solution A;

[0103] (2) The anhydrous ethanol solution of phenol with a mass fraction of 48.45% and the mixed solution A were cooled to 2° C. respectively. The anhydrous ethanol solution of phenol with a mass fraction of 48.45% was added to the mixed solution A, the theoretical amount of nitrous acid and the amount of phenol in the mixed solution A was 1.02:1, the reaction temperature was controlled at 5° C., the reaction was stirred for 2 hours, and the reaction was carried out in the dark and under nitrogen protection to obtain a mixed solution B;

[0104] (3) preheating the mixed solution B and a 50% by mass aqueous solution of hydroxylamine hydrochloride to 60° C. respectively; adding a 50% by mass aqueous solution of hydroxylamine hydrochloride to the mixed solution B, the molar ratio of hydroxylamine hydrochloride to the phenol conversion product in the mixed solution B being 1.05:1, the reaction temperature being controlled at 65° C., the reaction time being 2 min, and the reaction being carried out in the dark and under nitrogen protection, to obtain a mixed solution C;

[0105] (4) The obtained mixed solution C is subjected to reduced pressure distillation at 50° C. for 1 h, the steam is condensed to recover anhydrous ethanol, and the remaining liquid is evaporated, centrifuged, and dried at 70° C. for 1 h to obtain the final p-benzoquinone dioxime product.

[0106] After detection and measurement, the yield of p-benzoquinone dioxime prepared in Comparative Example 6 is 49.34%, the appearance is black powder, the purity is 85.732wt%, and the DSC Peak point is 214.65°C.

[0107] The yield and purity data of the products obtained in the examples of the present invention and the comparative examples are shown in Table 1 below:

[0108] Table 1

[0109]

[0110]

[0111] Note: The yields in the table are the yields calculated after decomposition.

[0112] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing p-benzoquinone dioxime using a microchannel reactor, comprising the steps of: 1) sodium nitrite aqueous solution and hydrochloric acid aqueous solution are respectively introduced into a first microchannel reactor to obtain a mixed solution A containing nitrous acid through reaction; 2) the ethanol or chloroform solution of phenol and the mixed solution A are respectively introduced into the second microchannel reactor to obtain a mixed solution B containing p-benzoquinone monoxime through a nitrosation reaction; 3) The mixed solution B and the aqueous solution of hydroxylamine hydrochloride are respectively introduced into the third microchannel reactor to obtain a mixed solution C containing p-benzoquinone dioxime through oximation reaction; 4) The mixed solution C is distilled under reduced pressure, the obtained steam is condensed to recover ethanol, and the obtained residual liquid is centrifuged and dried to obtain p-benzoquinone dioxime.

2. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 1), the mass fraction of the sodium nitrite aqueous solution is 50% to 60%, and the mass fraction of the hydrochloric acid aqueous solution is 20% to 30%.

3. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 1), the sodium nitrite aqueous solution and the hydrochloric acid aqueous solution are cooled to 3°C to 5°C before being introduced into the first microchannel reactor.

4. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 1), one or more of the following conditions are included: i. The introduction rate of the sodium nitrite aqueous solution and the hydrochloric acid aqueous solution is 16-35 g / min; ii. In the first microchannel reactor, the molar ratio of sodium nitrite to hydrochloric acid is 1:(1-1.2); iii. In the first microchannel reactor, the reaction temperature is 3°C to 10°C, the reaction residence time is 5 to 15 min, and the reaction is carried out in a light-proof and inert gas environment; preferably, the inert gas is nitrogen or argon.

5. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 2), one or more of the following conditions are included: i. The mass ratio of phenol to ethanol or chloroform is 1:(1-2); ii. The introduction rate of phenol ethanol or chloroform solution and mixed solution A is 12-26 g / min; iii. In the second microchannel reactor, the theoretical amount of nitrous acid and the amount of phenol in the mixed solution A are in a ratio of (1 to 1.1):

1.

6. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 2), the ethanol or chloroform solution of phenol and the mixed solution A are cooled to 0°C to 2°C before being introduced into the second microchannel reactor.

7. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 2), in the second microchannel reactor, the reaction temperature is 0°C to 5°C, the reaction residence time is 10 to 20 min, and the reaction is carried out in a light-proof and inert gas environment; preferably, the inert gas is nitrogen or argon.

8. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 3), one or more of the following conditions are included: i. The concentration of the aqueous solution of hydroxylamine hydrochloride is 50% to 60%; ii. The mixed solution B and the aqueous solution of hydroxylamine hydrochloride are preheated to 50° C. to 60° C. before being introduced into the third microchannel reactor; iii. The introduction rate of the mixed solution B and the aqueous solution of hydroxylamine hydrochloride is 9-45 g / min.

9. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 3), in the third microchannel reactor, the molar ratio of hydroxylamine hydrochloride to the phenol conversion product in the mixed solution B is (1-1.2):

1.

10. The method for preparing p-benzoquinone dioxime using a microchannel reactor according to claim 1, It is characterized in that In step 3), in the third microchannel reactor, the reaction temperature is 60°C to 75°C, the reaction residence time is 10 to 20 min, and the reaction is carried out in the dark and under the protection of an inert gas; preferably, the inert gas is nitrogen or argon.

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