Treatment method of isophthalonitrile raw material, hydrogenation method of isophthalonitrile and hydrogenation device

Abstract

The invention relates to the field of catalytic chemistry, in particular to a treatment method of an isophthalonitrile raw material, a hydrogenation method of isophthalonitrile and a hydrogenation device. The invention provides a treatment method of an isophthalonitrile raw material. The isophthalonitrile raw material is sequentially contacted with a dehydrating agent and a protective agent, the protective agent is used for removing amide impurities and carboxylic acid impurities; the isophthalonitrile raw material is a liquid phase mixture of isophthalonitrile and liquid ammonia. According to the method, the content of impurities such as water and 3-cyanobenzoic acid in the isophthalonitrile raw material can be effectively reduced, so that the problems that an isophthalonitrile hydrogenation catalyst in the prior art is relatively poor in activity and easy to inactivate are solved, and the purpose of preparing the m-xylylenediamine through efficient hydrogenation of the isophthalonitrile is achieved.

Description

Technical Field

[0001] This invention relates to the field of catalytic chemistry, and more specifically to a method for processing isophthalonitrile feedstock, a method for hydrogenating isophthalonitrile, and a hydrogenation apparatus. Background Technology

[0002] m-Phenylenediamine, abbreviated as MXDA, is also known as 1,3-phenylenediamine, 1,3-di(aminomethyl)benzene, or diaminom-xylene. Its structural formula is:

[0003]

[0004] CAS Registry Number: 1477-55-0, Molecular Formula: C8H 12 N2, molecular weight: 136.13. It is a colorless liquid with an almond odor. Upon prolonged exposure to air, it absorbs carbon dioxide and turns yellow. It is soluble in water and organic solvents. MXDA is an important fine chemical intermediate with three main applications: first, as a low-temperature, low-toxicity, low-viscosity epoxy resin curing agent; second, in the synthesis of nylon MXD6, which has high high-temperature strength and elasticity, high deformation temperature, low thermal expansion coefficient, and good barrier properties; and third, in the synthesis of isophthalic diisocyanate (XDI) polyurethane resin, which has excellent yellowing resistance. The demand for MXDA is expected to increase further in the future; therefore, the production of high-end MXDA products is a technology that urgently needs to be developed in China.

[0005] Currently, m-phenylenediamine is produced via liquid-phase catalytic hydrogenation of isophthalonitrile. The hydrogenation reaction can be carried out using either batch hydrogenation (stack-type) or continuous hydrogenation (fixed-bed). However, batch hydrogenation is significantly inferior to continuous hydrogenation in terms of product yield, production cost, and product quality, making fixed-bed hydrogenation the most important and promising production process for m-phenylenediamine. However, the fixed-bed hydrogenation process for m-phenylenediamine suffers from poor stability and significantly reduced catalytic activity of nickel-based hydrogenation catalysts. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of significantly reduced activity of hydrogenation catalysts during the hydrogenation of isophthalonitrile to isophthalic dimethylamine. This invention provides a method for processing isophthalonitrile feedstock, a hydrogenation method for isophthalonitrile, and a hydrogenation apparatus. This invention can effectively reduce the content of impurities such as water and 3-cyanobenzoic acid in the isophthalonitrile feedstock, thereby solving the problem of poor activity and easy deactivation of existing isophthalonitrile hydrogenation catalysts, and achieving efficient hydrogenation of isophthalonitrile to isophthalic dimethylamine.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for processing isophthalonitrile raw material, wherein the isophthalonitrile raw material is sequentially contacted with a dehydrating agent and a protective agent; the protective agent is used to remove amide impurities and carboxylic acid impurities; the isophthalonitrile raw material is a liquid-phase mixture of isophthalonitrile and liquid ammonia.

[0008] A second aspect of the present invention provides a method for hydrogenating isophthalonitrile, the method comprising: treating isophthalonitrile feedstock according to the above-described processing method of the present invention; and then reacting it with hydrogen in the presence of a catalyst.

[0009] A third aspect of the present invention provides an isophthalonitrile hydrogenation apparatus, the hydrogenation apparatus comprising:

[0010] The feed processing system and the hydrogenation system are connected in series along the material flow direction;

[0011] The raw material processing system includes: two-stage protective beds connected in series along the material flow direction;

[0012] The first-stage protective bed is used to fill a dehydrating agent, which is used to remove water from the isophthalonitrile feedstock.

[0013] The second-stage protective bed is used to fill with a protective agent, which is used to remove amide and carboxylic acid impurities from the isophthalonitrile feedstock;

[0014] The hydrogenation system is used for the hydrogenation of isophthalonitrile.

[0015] Through the above technical solution, this invention uses a dehydrating agent and a protective agent to treat isophthalonitrile feedstock, effectively reducing the content of water, amide impurities (e.g., 3-cyanobenzoamide), and carboxylic acid impurities (e.g., 3-cyanobenzoic acid) in the isophthalonitrile feedstock. The isophthalonitrile feedstock obtained by the aforementioned treatment method is used for hydrogenation to prepare isophthalic dimethylamine, effectively improving the stability of the catalyst (e.g., a nickel-based catalyst) under reaction conditions, thus achieving the goal of efficient hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine. According to embodiments of this invention, under stable catalyst operation for 500 hours, the isophthalonitrile conversion rate can reach over 97%, and the isophthalic dimethylamine selectivity can reach over 95%. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of the present invention provides a method for processing isophthalonitrile raw material, wherein the isophthalonitrile raw material is sequentially contacted with a dehydrating agent and a protective agent; the protective agent is used to remove amide impurities and carboxylic acid impurities; the isophthalonitrile raw material is a liquid-phase mixture of isophthalonitrile and liquid ammonia.

[0018] Unlike existing technologies that first dehydrate or decarboxylate the isophthalonitrile feedstock before mixing it with liquid ammonia for hydrogenation, in this invention, the feedstock used for isophthalonitrile hydrogenation is a liquid-phase mixture of isophthalonitrile and liquid ammonia. When the isophthalonitrile feedstock contains liquid ammonia, if the moisture in the feedstock is not removed in time, the liquid ammonia will react with water to generate strongly alkaline ammonia water, which will further lead to the hydrolysis of isophthalonitrile to generate 3-cyanobenzamide impurities. In addition, carboxylic acid and amide impurities in the feedstock can easily adsorb onto the catalyst surface, leading to catalyst deactivation. Therefore, it is necessary to remove the moisture in the feedstock first, and then remove the carboxylic acid and amide impurities.

[0019] The present invention employs the above-mentioned technical solution to dehydrate isophthalonitrile raw materials and then remove amide and carboxylic acid impurities, effectively reducing the content of water, amide and carboxylic acid impurities in isophthalonitrile raw materials.

[0020] In this invention, the isophthalonitrile content in the liquid mixture of isophthalonitrile and liquid ammonia can be selected from a wide range. This is an illustrative example, but does not limit the scope of the invention. According to one embodiment of the invention, the isophthalonitrile content is 1-7 wt%, for example, 2%, 3%, 4%, 5%, or 6%; and the liquid ammonia content is 93-99 wt%, for example, 94%, 95%, 96%, 97%, or 98%.

[0021] According to one embodiment of the present invention, the liquid mixture of isophthalonitrile and liquid ammonia does not contain other solvents, such as alkylpyrazole solvents.

[0022] In this invention, a dehydrating agent is used to remove water from isophthalonitrile raw materials. The range of types of dehydrating agents is relatively wide. This is an illustrative example, but it does not limit the scope of this invention. According to one embodiment of this invention, the dehydrating agent is selected from at least one of 4A molecular sieve, supported alkali metal oxides, and / or supported alkaline earth metal oxides.

[0023] According to a preferred embodiment of the present invention, in the supported alkali metal oxide and the supported alkaline earth metal oxide, the support is independently selected from one or more of SiO2, alumina, and magnesium oxide; wherein the content of alkaline earth metal and alkali metal is preferably 1-10 wt%, for example 2%, 4%, 6%, and 8%.

[0024] According to a preferred embodiment of the present invention, the dehydrating agent is selected from a composition of 4A molecular sieve and supported alkaline earth metal oxide; preferably, the volume ratio of 4A molecular sieve to supported alkaline earth metal oxide is 1:1-10, more preferably 1:2-8; the alkaline earth metal oxide can be, for example, magnesium oxide, barium oxide, calcium oxide, strontium oxide, etc.; which is beneficial for further removing water, amide impurities and carboxylic acid impurities from isophthalonitrile raw materials.

[0025] In this invention, the dehydrating agent is a composition of 4A molecular sieve and supported alkaline earth metal oxide. There are no particular limitations on the arrangement of the dehydrating agent; for example, it can be a mixture of 4A molecular sieve and supported alkaline earth metal oxide. Alternatively, the 4A molecular sieve and supported alkaline earth metal oxide can be arranged in layers, for example, isophthalonitrile raw material can be in sequential contact with the 4A molecular sieve layer and the supported alkaline earth metal oxide layer, or the isophthalonitrile raw material can be in sequential contact with the supported alkaline earth metal oxide layer and the 4A molecular sieve layer. According to a preferred embodiment of this invention, the isophthalonitrile raw material is in sequential contact with the 4A molecular sieve layer and the supported alkaline earth metal oxide layer, which is beneficial for reducing the carboxylic acid and amide content in isophthalonitrile.

[0026] According to a preferred embodiment of the present invention, the supported alkaline earth metal oxide is CaO supported on SiO2; this is beneficial for further removing water, amide impurities and carboxylic acid impurities from the isophthalonitrile raw material.

[0027] In this invention, the range of types of protective agents is relatively wide. This is an illustrative example, but it does not limit the scope of this invention. According to one embodiment of this invention, the protective agent is selected from at least one of silica gel and basic resin; preferably, the basic resin is selected from one or more of Dow 550A(OH) strong base anion exchange resin and strong base styrene-based anion exchange resin.

[0028] According to a preferred embodiment of the present invention, the protective agent is an alkaline resin.

[0029] In this invention, the volume ratio of isophthalonitrile raw material to dehydrating agent can be selected over a wide range. According to a preferred embodiment of this invention, the flow rate of isophthalonitrile raw material is 0.06-0.25 times / min of the volume of dehydrating agent, preferably 0.1-0.2 times / min.

[0030] In this invention, the volume ratio of isophthalonitrile raw material to protective agent can be selected over a wide range. According to a preferred embodiment of this invention, the flow rate of isophthalonitrile raw material is 0.05-0.5 times / min of the volume of protective agent, preferably 0.1-0.4 times / min.

[0031] In this invention, there are no special limitations on the contact conditions between isophthalonitrile raw material and dehydrating agent; conventional conditions in the art are sufficient. This is an illustrative example, but it does not limit the scope of the invention. According to one embodiment of the invention, the contact conditions include: a contact temperature of 20-60°C, preferably 30-50°C, for example, 32°C, 35°C, 38°C, 40°C, 34°C, 45°C, or 48°C.

[0032] In this invention, there are no special limitations on the contact conditions between isophthalonitrile raw material and protective agent; conventional conditions in the art are sufficient. This is an illustrative example, but it does not limit the scope of the invention. According to one embodiment of the invention, the contact conditions include contact under a nitrogen atmosphere.

[0033] According to one embodiment of the present invention, the moisture content of the isophthalonitrile raw material is ≤0.5wt%, preferably ≤3000ppm.

[0034] According to one embodiment of the present invention, the content of carboxylic acid and amide is calculated as carboxylic acid content. In the isophthalonitrile raw material, the content of carboxylic acid and amide is ≤0.1wt%, preferably ≤500ppm.

[0035] According to a preferred embodiment of the present invention, the water content in the isophthalonitrile feedstock after contact with the protective agent is ≤500ppm, which is beneficial to improving the stability of the isophthalonitrile hydrogenation catalyst.

[0036] According to a preferred embodiment of the present invention, the content of carboxylic acid and amide is calculated as carboxylic acid content. In the isophthalonitrile raw material after contact with the protective agent, the content of carboxylic acid and amide impurities is ≤200ppm, which is beneficial to improving the stability of the isophthalonitrile hydrogenation catalyst.

[0037] According to a preferred embodiment of the present invention, isophthalonitrile raw material is sequentially contacted with a dehydrating agent and a protective agent in an inert gas atmosphere.

[0038] In this invention, there is no particular limitation on the type of inert gas. According to a preferred embodiment of the invention, the inert gas is selected from one or more of nitrogen and rare gases.

[0039] A second aspect of the present invention provides a method for hydrogenating isophthalonitrile, the method comprising: treating isophthalonitrile feedstock according to the above-described processing method of the present invention; and then reacting it with hydrogen in the presence of a catalyst.

[0040] In the production of isophthalonitrile, the raw materials contain some 3-cyanobenzoic acid impurities, which are carried into the hydrogenation process. Isophthalonitrile is highly likely to hydrolyze to generate 3-cyanobenzoic acid and 3-cyanobenzamide, among other impurities. These impurities further react and coat the surface of the catalyst's active sites, significantly degrading the hydrogenation effect. The method for treating isophthalonitrile raw materials described in this invention reduces the content of water, amide impurities, and carboxylic acid impurities in the raw materials, significantly reducing the occurrence of other side reactions and improving catalyst stability.

[0041] In this invention, there are no special requirements for the amount of hydrogen used, and it can be the conventional amount used in the art. According to one embodiment of the invention, the molar ratio of hydrogen to isophthalonitrile is 8-18, for example, 10, 12, 15, or 16.

[0042] According to one embodiment of the present invention, the liquid space velocity is 2.75-5 h⁻¹. -1 For example, 3h -1 4h -1 5h -1 .

[0043] In this invention, there are no special limitations on the hydrogenation reaction conditions; conventional conditions in the art are acceptable. This is an illustrative example, but it does not limit the scope of the invention. According to one embodiment of the invention, the hydrogenation conditions include: a temperature of 40-100°C, for example, 50°C, 60°C, 70°C, 80°C, or 90°C; and a pressure of 7-9 MPa.

[0044] In this invention, the range of catalysts that can be selected is relatively wide. According to a preferred embodiment of this invention, the catalyst is selected from one or more nickel-based catalysts. The nickel-based catalyst is a catalyst containing nickel, such as at least one of Raney nickel and supported nickel. The support for the supported nickel is preferably alumina, silicon dioxide, titanium dioxide, magnesium oxide, or activated carbon. Preferably, the nickel-containing catalyst also contains one or more of group VIB metal elements, group IB metal elements, group IIB metal elements, and group VIII metal elements, such as W, Mo, Cu, Zn, Co, etc.

[0045] In a preferred embodiment of the present invention, isophthalonitrile feedstock enters the first-stage protective bed along the upward feed flow direction, allowing the isophthalonitrile feedstock to fully contact and dehydrate with the dehydrating agent, and then enters the second-stage protective bed along the downward feed flow direction.

[0046] According to a preferred embodiment of the present invention, the hydrogenation feedstock is carried out in a fixed-bed apparatus, the hydrogenation temperature is 40-100°C, the pressure is 7-9 MPa, and the liquid hourly space velocity is 2.75-5 h⁻¹. -1The hydrogen-nitrogen molar ratio is 8-18. The hydrogenation feedstock (IPN liquid ammonia solution with an IPN concentration of 5wt%) is fed into the reaction unit by a metering pump at a rate of 0.4-1.0 mL / min.

[0047] A third aspect of the present invention provides an isophthalonitrile hydrogenation apparatus, the hydrogenation apparatus comprising:

[0048] The feed processing system and the hydrogenation system are connected in series along the material flow direction;

[0049] The raw material processing system includes: two-stage protective beds connected in series along the material flow direction;

[0050] The first-stage protective bed is used to fill a dehydrating agent, which is used to remove water from the isophthalonitrile feedstock.

[0051] The second-stage protective bed is used to fill with a protective agent, which is used to remove amide and carboxylic acid impurities from the isophthalonitrile feedstock;

[0052] The hydrogenation system is used for the hydrogenation of isophthalonitrile.

[0053] The hydrogenation apparatus described above in this invention purifies the raw material for the hydrogenation of isophthalonitrile to produce isophthalic dimethylamine, effectively reducing the content of water, amide impurities, and carboxylic acid impurities in the hydrogenation raw material, reducing the occurrence of other side reactions, and improving the selectivity and stability of the catalyst.

[0054] In this invention, the reaction bed is used to fill with optional supports. There are no special requirements for the filling position of the supports. According to one embodiment of the invention, the supports are filled in the upper and / or lower part of the reaction bed.

[0055] In this invention, the range of types of supports that can be selected is relatively wide. This is an illustrative example, but it does not limit the scope of this invention. According to one embodiment of this invention, the support is selected from one or more inert supports; preferably, the inert support is inert quartz sand; more preferably, the inert quartz sand has a mesh size of 20-40 mesh.

[0056] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0057] In the following examples, the isophthalonitrile feedstock was evaluated in a fixed-bed apparatus. The catalyst and inert silica sand were packed with inert silica sand at the top and bottom, with the catalyst in the middle. The catalyst was a Ni-W / Al2O3 catalyst. The hydrogenation temperature was 80°C, the pressure was 8.0 MPa, and the liquid hourly space velocity was 4 h⁻¹. -1The hydrogen-nitrogen molar ratio is 16. The hydrogenation feedstock (IPN-liquid ammonia feedstock) is fed into the reaction unit by a metering pump. After running for 500 hours, the gas phase after the reaction is directly discharged into the air, and the liquid phase is collected by condensation for qualitative and quantitative chromatographic analysis.

[0058] The water content in isophthalonitrile feedstock was determined by the Karl Fischer method.

[0059] The principle of acid value determination: the number of milligrams or millimoles of potassium hydroxide required to neutralize 1g of sample. a. 95% ethanol; b. Potassium hydroxide standard solution c(KOH) = 0.05mol / L, standardized according to GB 601; c. Phenolphthalein indicator solution 1g / L ethanol solution; d. Neutral ethanol: using phenolphthalein as an indicator, adjust 95% ethanol to a faint pink color with b. potassium hydroxide standard solution.

[0060] Test method: Accurately weigh the sample into neutral ethanol, heat to dissolve, add 1 drop of phenolphthalein indicator, and use potassium hydroxide standard solution to titrate until the color does not fade in 10 seconds as the endpoint.

[0061] In the following examples, the water content of the isophthalonitrile liquid ammonia feedstock was 3000 ppm, and the content of carboxylic acid and amide impurities was 492 ppm.

[0062] Example 1

[0063] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the material flow direction using a plunger pump at a rate of 1.0 mL / min. The first-stage protective bed was filled with 4A molecular sieve dehydrating agent (8 mL in volume). The bed temperature in the dehydrating agent filling section was kept constant at 40°C. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the material flow direction. The second-stage protective bed was filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, 8 mL in volume). After treatment, contacted isophthalonitrile feedstock A was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock A are shown in Table 1.

[0064] (2) Raw material A was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 97.1% and the selectivity of isophthalic dimethylamine was 91.3%.

[0065] Example 2

[0066] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the material flow direction using a plunger pump at a rate of 1.0 mL / min. The first-stage protective bed was filled with CaO / SiO2 supported dehydrating agent with a CaO mass content of 15 wt% (volume 8 mL). The bed temperature in the dehydrating agent filling section was kept constant at 40℃. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the material flow direction. The second-stage protective bed was filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, volume 8 mL). After treatment, contacted isophthalonitrile feedstock B was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock B are shown in Table 1.

[0067] (2) Raw material B was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 98.9% and the selectivity of isophthalic dimethylamine was 94.9%.

[0068] Example 3

[0069] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the material flow direction of the feed using a plunger pump at a rate of 1.0 mL / min. The first-stage protective bed was filled with 4A molecular sieve and CaO / SiO2 supported dehydrating agent with a mass content of 15 wt% CaO (total volume of 8 mL). The bed temperature in the dehydrating agent filling section was kept constant at 40℃. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the material flow direction of the feed. The second-stage protective bed was filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, volume of 8 mL). After treatment, isophthalonitrile feedstock C after contact was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock C are shown in Table 1.

[0070] (2) Raw material C was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 99.7% and the selectivity of isophthalic dimethylamine was 95.6%.

[0071] Example 4

[0072] (1) IPN-liquid ammonia feedstock with a concentration of 1 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the material flow direction using a plunger pump at a rate of 0.5 mL / min. The first-stage protective bed was filled with CaO / SiO2 supported dehydrating agent with a CaO mass content of 20 wt% (volume 8 mL). The bed temperature in the dehydrating agent filling section was kept constant at 30°C. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the material flow direction. The second-stage protective bed was filled with alkaline resin (strong base styrene-based anion exchange resin, volume 2 mL). After treatment, contacted isophthalonitrile feedstock D was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock D are shown in Table 1.

[0073] (2) Raw material D was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 97.3% and the selectivity of isophthalic dimethylamine was 92.7%.

[0074] Example 5

[0075] (1) IPN-liquid ammonia feedstock with a concentration of 7 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the material flow direction using a plunger pump at a rate of 2.0 mL / min. The first-stage protective bed was filled with CaO / SiO2 supported dehydrating agent with a CaO mass content of 8 wt% (volume of 10 mL). The bed temperature in the dehydrating agent filling section was kept constant at 60°C. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the material flow direction. The second-stage protective bed was filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, volume of 4 mL). After treatment, contacted isophthalonitrile feedstock E was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock E are shown in Table 1.

[0076] (2) Raw material E was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 97.5% and the selectivity of isophthalic dimethylamine was 91.9%.

[0077] Example 6

[0078] The method of Example 2 is the same as in Example 1, except that the first-stage protective bed is filled with CaO / SiO2 supported dehydrating agent (4 mL in volume).

[0079] The water content, carboxylic acid content, and amide content of the isophthalonitrile raw material are shown in Table 1;

[0080] The conversion rate of isophthalonitrile was 98%, and the selectivity of m-phenylenediamine was 94.7%.

[0081] Example 7

[0082] The method of Example 2 is the same as in Example 1, except that the second-stage protective bed is filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, volume 2 mL).

[0083] The water content, carboxylic acid content, and amide content of the isophthalonitrile raw material are shown in Table 1;

[0084] The conversion rate of isophthalonitrile was 97.6%, and the selectivity of m-phenylenediamine was 93.8%.

[0085] Comparative Example 1

[0086] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the feed direction at a rate of 1.0 mL / min using a plunger pump. The first-stage protective bed was filled with 4A molecular sieve dehydrating agent (8 mL in volume). The bed temperature in the dehydrating agent filling section was kept constant at 40°C. The entire protective bed was protected with nitrogen. After treatment, contacted isophthalonitrile feedstock F was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock F are shown in Table 1.

[0087] (2) Raw material F was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 96.7% and the selectivity of isophthalic dimethylamine was 90.2%.

[0088] Comparative Example 2

[0089] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the feed direction at a rate of 1.0 mL / min using a plunger pump. The first-stage protective bed was filled with CaO / SiO2 supported dehydrating agent with a CaO mass content of 15 wt% (volume of 8 mL). The bed temperature in the dehydrating agent filling section was kept constant at 40℃. The entire protective bed was protected with nitrogen. After treatment, contacted isophthalonitrile feedstock G was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock G are shown in Table 1.

[0090] (2) Raw material G was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 95.6% and the selectivity of isophthalic dimethylamine was 92.4%.

[0091] Comparative Example 3

[0092] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the bottom feed direction using a plunger pump at a rate of 1.0 mL / min. The first-stage protective bed was filled with alkaline resin (Dow 550A(OH) strong base anion exchange resin, volume 8 mL) as a protective agent. The entire protective bed was protected with nitrogen. Then the feedstock was fed into the second-stage protective bed along the top feed direction. The second-stage protective bed was filled with 4A molecular sieve dehydrating agent (volume 8 mL). The bed temperature in the dehydrating agent filling section was kept constant at 40°C. After treatment, contacted isophthalonitrile feedstock H was obtained. The water content, carboxylic acid content and amide content of isophthalonitrile feedstock H are shown in Table 1.

[0093] (2) The raw material H was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 96.2% and the selectivity of isophthalic dimethylamine was 90.5%.

[0094] Comparative Example 4

[0095] (1) IPN-liquid ammonia feedstock with a concentration of 5 wt% isophthalonitrile was fed into the first-stage protective bed from the top along the bottom feed direction at a rate of 1.0 mL / min using a plunger pump. The first-stage protective bed was filled with a protective agent, alkaline resin (Dow 550A(OH) strong base anion exchange resin, with a volume of 8 mL). The entire protective bed was protected with nitrogen. After treatment, contacted isophthalonitrile feedstock I was obtained. The water content, carboxylic acid content, and amide content of isophthalonitrile feedstock I are shown in Table 1.

[0096] (2) Raw material I was fed into the hydrogenation system along the material flow direction. The hydrogenated substances were subjected to chromatographic qualitative and quantitative analysis. The results showed that the conversion rate of isophthalonitrile was 89.7% and the selectivity of isophthalic dimethylamine was 86.4%.

[0097] Table 1

[0098]

[0099]

[0100] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for processing isophthalonitrile raw material, characterized in that, The isophthalonitrile raw material is contacted sequentially with the dehydrating agent and the protective agent; Protective agents are used to remove amide and carboxylic acid impurities; The isophthalonitrile raw material is a liquid-phase mixture of isophthalonitrile and liquid ammonia.

2. The processing method according to claim 1, wherein, In a liquid mixture of isophthalonitrile and liquid ammonia, the isophthalonitrile content is 1-7 wt%, and the liquid ammonia content is 93-99 wt%; and / or The liquid mixture of isophthalonitrile and liquid ammonia does not contain any other solvents; and / or The dehydrating agent is selected from at least one of 4A molecular sieve, supported alkali metal oxide and / or supported alkaline earth metal oxide; More preferably, in the supported alkali metal oxide and / or supported alkaline earth metal oxide, the support is independently selected from one or more of SiO2, alumina, and magnesium oxide; preferably, the content of alkaline earth metal and alkali metal is 1-10 wt% each; and / or The protective agent is selected from at least one of silica gel and basic resin. Preferably, the basic resin is selected from one or more of Dow 550A(OH) strong base anion exchange resin and strong base styrene-based anion exchange resin.

3. The processing method according to claim 1 or 2, wherein, The dehydrating agent is a combination of 4A molecular sieve and supported alkaline earth metal oxide; Preferably, the volume ratio of 4A molecular sieve to supported alkaline earth metal oxide is 1:1-10, more preferably 1:2-8; More preferably, the supported alkaline earth metal oxide is CaO supported on SiO2, with a CaO content of 1-20 wt%.

4. The processing method according to any one of claims 1-3, wherein, The flow rate of the isophthalonitrile feedstock is 0.06-0.25 times the volume of the dehydrating agent per min, preferably 0.1-0.2 times per min; and / or The flow rate of the isophthalonitrile feedstock is 0.05-0.5 times the volume of the protective agent per min, preferably 0.1-0.4 times per min; and / or The conditions for contact between isophthalonitrile feedstock and dehydrating agent include: a temperature of 20-60°C, preferably 30-50°C; and / or The conditions for contact between isophthalonitrile raw materials and protective agents include: contact under a nitrogen atmosphere.

5. The processing method according to any one of claims 1-4, wherein, The isophthalonitrile raw material has a moisture content of ≤0.5wt%, preferably ≤3000ppm; and / or The content of carboxylic acids and amides is calculated as carboxylic acid content. In the isophthalonitrile raw material, the content of carboxylic acids and amides is ≤0.1wt%, preferably ≤500ppm; and / or The isophthalonitrile feedstock after contact with the protective agent has a water content ≤500ppm; and / or The content of carboxylic acids and amides is expressed as carboxylic acid content. In isophthalonitrile raw materials after contact with the protective agent, the content of carboxylic acid and amide impurities is ≤200ppm.

6. A method for hydrogenating isophthalonitrile, characterized in that, The method includes: The isophthalonitrile feedstock is processed according to the processing method of any one of claims 1-5; then, it is hydrogenated with hydrogen in the presence of a catalyst.

7. The hydrogenation method according to claim 6, wherein, The molar ratio of hydrogen to isophthalonitrile is 8-18; and / or The liquid space velocity is 2.75-5 h⁻¹. -1 ; and / or Hydrogenation reaction conditions include: temperature 40-100℃; pressure 7-9MPa; and / or The catalyst is selected from one or more nickel-based catalysts.

8. The hydrogenation method according to claim 6 or 7, wherein, The method is carried out in a hydrogenation unit, which includes: The feed processing system and the hydrogenation system are connected in series along the material flow direction; The raw material processing system includes: two-stage protective beds connected in series along the material flow direction; The first-stage protective bed is used to fill a dehydrating agent, which is used to remove water from the isophthalonitrile feedstock. The second-stage protective bed is used to fill with a protective agent, which is used to remove amide and carboxylic acid impurities from the isophthalonitrile feedstock; The hydrogenation system is used for the hydrogenation of isophthalonitrile; The hydrogenation method includes: (1) The isophthalonitrile feedstock enters the first-stage protective bed along the material flow direction and comes into contact with the dehydrating agent; then it enters the second-stage protective bed and comes into contact with the protective agent. (2) It then enters the hydrogenation system and undergoes a hydrogenation reaction with hydrogen; Preferably, the isophthalonitrile feedstock enters the first-stage protective bed along the upward feed flow direction, and then enters the second-stage protective bed along the downward feed flow direction.

9. An isophthalonitrile hydrogenation apparatus for use in the method according to any one of claims 6-8, characterized in that, The hydrogenation unit includes: The feed processing system and the hydrogenation system are connected in series along the material flow direction; The raw material processing system includes: two-stage protective beds connected in series along the material flow direction; The first-stage protective bed is used to fill a dehydrating agent, which is used to remove water from the isophthalonitrile feedstock. The second-stage protective bed is used to fill with a protective agent, which is used to remove amide and carboxylic acid impurities from the isophthalonitrile feedstock; The hydrogenation system is used for the hydrogenation of isophthalonitrile.

10. The hydrogenation apparatus according to claim 9, wherein, The hydrogenation system includes: a reaction bed for loading a catalyst and optionally a support; the support is selected from one or more inert supports; Preferably, the support fills the upper and / or lower part of the reaction bed; Preferably, the inert support is inert quartz sand; Preferably, the inert quartz sand has a mesh size of 20-40.

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