Method for evaluating influence of raw material benzene p-nitrobenzene hydrogenation catalyst and aniline production method

Abstract

The present application relates to a kind of raw material benzene p-nitrobenzene hydrogenation catalyst influence evaluation method, comprising the following steps: raw material benzene is purchased, and heavy component monitoring index is increased, and heavy component is directly used in nitration and hydrogenation process when lower than certain content;Heavy component is higher than certain content, and raw material benzene needs to be concentrated, and the influence on hydrogenation catalyst activity is evaluated, and raw material benzene use and processing scheme are formulated according to the evaluation result.The present application also relates to a kind of aniline production method.The present application can effectively prevent the material of entraining toxic catalyst in raw material benzene, along with nitrobenzene into hydrogenation reactor, effectively avoid catalyst activity reduction, cause hydrogenation reaction parameter to fluctuate sharply, and then lead to catalyst consumption sharp increase, when serious, can cause system catalyst overall deactivation, improve the stability of production process.

Description

TECHNICAL FIELD

[0001] The present application relates to nitrobenzene hydrogenation production process, and in particular to a method for evaluating the influence of a raw material, i.e. p-nitrobenzene, on a hydrogenation catalyst and a method for producing aniline. BACKGROUND

[0002] Aniline is one of the important organic chemical raw materials. It is widely used in the dye, medicine, explosive, perfume, rubber vulcanization accelerator and other industries, and is an important raw material for MDI (4,4-diphenyl methane diisocyanate). The mainstream process for producing aniline at present is the liquid phase hydrogenation of nitrobenzene (nitrobenzene and hydrogen are reacted to produce aniline under the action of a palladium-platinum catalyst, and the reaction temperature is 200°C). The mainstream process for producing the raw material, i.e. nitrobenzene, is the adiabatic nitration of benzene (benzene and nitric acid are reacted to produce nitrobenzene under the action of 70% sulfuric acid as a catalyst, and the reaction temperature is 130°C). Specifically, raw benzene is reacted in nitro-sulfur mixed acid to produce crude nitrobenzene, the crude nitrobenzene is washed and refined to obtain the product, i.e. nitrobenzene, and the product, i.e. nitrobenzene, is further reacted with hydrogen under the action of a catalyst to produce crude aniline, and the crude aniline is refined to obtain the product, i.e. aniline.

[0003] The hydrogenation of nitrobenzene usually uses a supported noble metal catalyst, which has the advantages of mild reaction conditions, high selectivity and good product quality. However, such a catalyst is prone to deactivation during the hydrogenation process due to the following reasons: 1) the high CO / CO2 content in hydrogen is highly toxic to the noble metal catalyst; 2) some sulfur-containing compounds introduced into the reaction system are strongly adsorbed on the active surface of the noble metal, causing sulfur poisoning of the noble metal catalyst; and 3) impurities such as azo compounds, oxidation azo compounds and tar-like macromolecular compounds generated during the reaction cause the pore channels of the catalyst to be blocked and the surface active centers to be covered, resulting in a decrease in the activity of the catalyst.

[0004] In view of the above factors affecting the noble metal hydrogenation catalyst, mature monitoring and control measures have been taken in the existing aniline production process, such as reducing the CO / CO2 content in hydrogen to less than 5 ppm by means of a methanation reaction, avoiding the introduction of sulfur substances during the hydrogenation process by monitoring the total sulfur content in the raw material benzene, and avoiding the blockage of the micropores of the catalyst by controlling the tar content in the reaction system. However, in the actual production of aniline, the activity of the noble metal hydrogenation catalyst is still frequently reduced, resulting in a significant increase in the unit consumption of the catalyst and affecting the stability of the aniline production process. SUMMARY

[0005] The inventors of the present application found through a large number of experimental researches that trace impurities in raw benzene can enter a hydrogenation reactor along with nitrobenzene products after a nitration reaction, thereby producing a toxic effect on a noble metal hydrogenation catalyst, and once the redundancy of the catalyst resistance to poison exceeds, permanent deactivation of the catalyst can be caused. Further, the inventors established a method for monitoring trace impurities in raw benzene and evaluating the influence of the trace impurities on the activity of a noble metal catalyst, classified different raw benzene, determined direct use, blending use, desorption treatment and other use schemes, thereby effectively avoiding deactivation of the catalyst used in hydrogenation reaction, reducing the cost of the catalyst, improving the stability of the process production, and thus completing the present application.

[0006] The main purpose of the present application is to provide a method for evaluating the influence of raw benzene on a p-nitrobenzene hydrogenation catalyst, which can effectively identify raw benzene having a toxic effect on the activity of the catalyst, and develop a reasonable use scheme to avoid the toxic effect of the raw benzene on the hydrogenation catalyst, thereby greatly improving the stability of the hydrogenation process production.

[0007] Another purpose of the present application is to provide a method for preparing aniline from raw benzene comprising the aforementioned evaluation method.

[0008] To achieve the above purposes, the technical solutions of the present application are as follows:

[0009] A method for evaluating the influence of raw benzene on a p-nitrobenzene hydrogenation catalyst, comprising the following steps:

[0010] 1) Raw benzene quality monitoring: analyzing the heavy component content in any batch of raw benzene, and determining that the batch of raw benzene has no influence on the p-nitrobenzene hydrogenation catalyst when the heavy component content is less than or equal to 10 ppm;

[0011] When the heavy component content is greater than 10 ppm, it is determined that the batch of raw benzene may have an influence on the p-nitrobenzene hydrogenation catalyst, and the activity of the raw benzene needs to be further evaluated;

[0012] 2) Raw benzene activity evaluation: distilling and concentrating the raw benzene, then evaluating the influence of the concentrated liquid on the activity of the p-nitrobenzene hydrogenation catalyst, and calculating the activity factor K and the relative activity index γ of the concentrated liquid;

[0013] When the relative activity index γ of the batch of raw benzene is greater than or equal to 0.9, it is determined that the batch of raw benzene with excessive heavy components has no influence on the p-nitrobenzene hydrogenation catalyst;

[0014] When the relative activity index γ of the batch of raw benzene is less than 0.9, it is determined that the batch of raw benzene with excessive heavy components has an influence on the p-nitrobenzene hydrogenation catalyst.

[0015] In a specific embodiment, the heavy component content of the raw benzene in step 1) is detected by gas chromatography, the chromatographic column is Agilent 19095J-323: 300℃: 30m x 530um x 1.5um, the carrier gas is nitrogen, the flow rate is 3ml / min, the detector is FID, the detection temperature is 300℃, and the programmed temperature is: 50℃ for 2min, 8℃ / min to 80℃, 1min, 15℃ / min to 300℃, 10min.

[0016] In a specific embodiment, the purity and impurity content of the raw benzene is calculated by area normalization, and the heavy component content of the raw benzene is the total content of substances with carbon number greater than 9.

[0017] In a specific embodiment, the method for distillation and concentration of the raw benzene in step 2) is as follows: 300-600g of raw benzene is taken and added to a three-necked flask, the temperature is raised to 75-95℃, preferably 80℃, using a heating device, and the benzene is continuously vaporized to obtain a concentrated solution, and the concentration multiple is controlled to be 25-35, preferably 30.

[0018] In a specific embodiment, the evaluation method of the activity of the raw benzene concentrated solution is as follows: 0.0045g of hydrogenation catalyst, 15g of nitrobenzene, 5g of benzene concentrated solution, 30ml of water and 50ml of ethanol are added to a reaction kettle, then the reaction kettle is pressurized to 25-35bar, preferably 30bar, with hydrogen, the temperature of the reaction kettle is raised to 100℃, and then the stirring speed is set to 900rpm, the nitrobenzene continuously reacts with hydrogen under the action of the catalyst to generate aniline, and the time when the pressure of the reaction kettle drops by 5bar, 10bar, 15bar and 20bar is recorded as T5, T10, T15 and T20 respectively; the relative activity index calculation model of the raw benzene concentrated solution is as follows:

[0019] κ activity factor = 1 / (T5) + 1 / (T10-T5) + 1 / (T15-T10) + 1 / (T20-15);

[0020] γ relative activity index = κ abnormal benzene activity factor / κ normal benzene activity factor.

[0021] On the other hand, a method for producing aniline, comprising the steps of nitration of raw benzene to obtain nitrobenzene, and hydrogenation of the nitrobenzene to obtain aniline, wherein the raw benzene is first evaluated for its effect on the hydrogenation catalyst of the nitrobenzene by the method described above, and then the use mode of the raw benzene is determined.

[0022] In a specific embodiment, when the heavy component content of the raw benzene is less than or equal to 10ppm, the batch of raw benzene can be used directly, and the benzene is nitrated to obtain nitrobenzene, which does not affect the hydrogenation catalyst.

[0023] In a specific embodiment, when the heavy component content in the raw material benzene is greater than 10 ppm, the activity of the batch of raw material benzene is further evaluated.

[0024] In a specific embodiment, if the relative activity index γ of the batch of raw material benzene is greater than or equal to 0.9, the batch of raw material benzene with excessive heavy components can be directly used.

[0025] If the relative activity index of the batch of raw material benzene is less than 0.9, the batch of raw material benzene needs to be mixed and used with normal benzene in a certain proportion.

[0026] In a specific embodiment, the calculation model of the mixing ratio is: abnormal benzene: normal benzene = 1: a * (1 / γ-1), wherein the coefficient a is 1-3, preferably 1.

[0027] Compared with the prior art, the positive effects of the present application are:

[0028] 1) The evaluation method of the present application for the influence of raw material benzene on p-nitrobenzene hydrogenation catalyst is simple and effective. By establishing a heavy component monitoring index in raw material benzene, raw materials with potential influence on the activity of hydrogenation catalyst can be screened out in time.

[0029] 2) The evaluation method of the present application for the influence of raw material benzene on p-nitrobenzene hydrogenation catalyst is concentrated on the activity evaluation of abnormal benzene, further quantifying the influence factor of the batch of raw material benzene on the activity of hydrogenation catalyst, so as to develop an abnormal benzene use scheme.

[0030] 3) The aniline production method of the present application, after using the raw material benzene evaluation method of the present application, can effectively avoid the reduction of catalyst activity and improve the stability of hydrogenation reaction in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The flowchart of the evaluation method of the present application for the influence of raw material benzene on p-nitrobenzene hydrogenation catalyst is shown. DETAILED DESCRIPTION

[0032] In order to better understand the technical solutions of the present application, the following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any known changes within the scope of the claims of the present application should also be included.

[0033] As Figure 1As shown, a method for evaluating the influence of a raw material benzene p-nitrobenzene hydrogenation catalyst is first analyzed for the sample of the batch of raw material benzene, and the heavy components in the batch of raw material benzene are monitored. When the content of heavy components is less than or equal to 10 ppm, it is determined that the quality of the raw material benzene is normal and can be directly used, and will not affect the activity of the subsequent nitration and nitrobenzene hydrogenation catalyst. When the content of heavy components is greater than 10 ppm, it is determined that the quality of the raw material benzene is abnormal and may affect the activity of the subsequent nitrobenzene hydrogenation catalyst, and the activity of the raw material benzene needs to be further evaluated and confirmed. The activity of the raw material benzene is evaluated by concentrating the raw material benzene, and when the relative activity index is greater than or equal to 0.9, it is determined that the quality of the batch of raw material benzene is also normal and can be directly used, and will not affect the activity of the nitrobenzene hydrogenation catalyst. When the relative activity index is less than 0.9, it is determined that the quality of the batch of raw material benzene is abnormal or abnormal and cannot be directly used, and needs to be mixed with normal raw material benzene for use.

[0034] (I) Raw material benzene quality monitoring

[0035] The conventional analysis indicators of the raw material benzene mainly include benzene content, aromatic hydrocarbon (except benzene), non-aromatic hydrocarbon, and total sulfur. The present application develops a quantitative analysis method for heavy component substances in benzene (gas chromatography detection, chromatographic column is Agilent 19095J-323: 300℃: 30m x 530um x 1.5um, carrier gas is nitrogen, flow rate is 3ml / min, detector FID, detection temperature 300℃, program temperature: 50℃ for 2min, 8℃ / min to 80 degrees, hold for 1min, 15℃ / min to 300℃, hold for 10min). The benzene purity and impurity content are calculated by area normalization, and the substances with carbon number greater than 9 are defined as heavy components, and the total content of C9 heavy component substances is quantitatively counted. By monitoring the content of heavy components in the raw material benzene, a heavy component monitoring database of the raw material benzene is established, the heavy components in the raw material benzene are analyzed in association with the hydrogenation reaction stability, and it is found that when the content of heavy components in the raw material benzene is less than or equal to 10ppm, the hydrogenation catalyst activity will not be adversely affected during the preparation of aniline by hydrogenation reaction of nitrobenzene prepared by nitration. When the content of heavy components in the raw material benzene is greater than 10ppm, the hydrogenation catalyst activity may be affected during the preparation of aniline by hydrogenation reaction of nitrobenzene prepared by nitration. Therefore, the raw material benzene with less than or equal to 10ppm of heavy components is defined as normal benzene, and the raw material benzene with more than 10ppm of heavy components is defined as abnormal benzene.

[0036] (II) Raw material benzene activity evaluation

[0037] The raw material benzene is distilled and concentrated, and then the influence of the concentrated liquid on the activity of the nitrobenzene hydrogenation catalyst is evaluated, and the activity factor K and the relative activity index γ of the concentrated liquid are calculated.

[0038] The raw material benzene distillation concentration step: take 300-600g of raw material benzene, add to a three-necked flask, use heating equipment to warm up to 75-95°C, preferably 80°C, benzene is continuously vaporized to obtain a concentrated solution of 10-20g, control the concentration ratio of 25-35 times, preferably 30 times.

[0039] The nitrobenzene hydrogenation catalyst activity evaluation step: add 0.0045g of hydrogenation catalyst, 15g of nitrobenzene, 5g of benzene concentrate, 30ml of water, and 50ml of ethanol to a reaction kettle, then charge the reaction kettle with 25-35bar of hydrogen, preferably 30bar, warm the reaction kettle to 100°C, then set the stirring speed to 900rpm, nitrobenzene continuously reacts with hydrogen under the action of the catalyst to generate aniline, record the time when the reaction kettle pressure drops by 5bar, 10bar, 15bar, and 20bar as T5, T10, T15, and T20, respectively.

[0040] The activity factor calculation model of the concentrated solution is:

[0041] The activity factor calculation model of the concentrated solution is:

[0042] Respectively detect the activity factor of normal benzene and abnormal benzene, and calculate the relative activity index according to the following model:

[0043] The relative activity index is calculated according to the following model:

[0044] (Three) raw material benzene use scheme

[0045] According to the raw material benzene quality monitoring and raw material benzene activity evaluation results, the raw material benzene use scheme is determined.

[0046] 1) If the heavy component content in the raw material benzene is less than or equal to 10ppm, the batch of raw material benzene can be directly used, and benzene is nitrified to obtain nitrobenzene, which does not affect the hydrogenation catalyst.

[0047] 2) If the heavy component content in the raw material benzene is greater than 10ppm, the batch of raw material benzene needs to be distilled and concentrated, and then the concentrated solution is evaluated for nitrobenzene hydrogenation to obtain the activity factor of the batch of benzene concentrate. If the relative activity index of the batch of raw material benzene is greater than or equal to 0.9, the batch of raw material benzene with excessive heavy components can be directly used, and if the relative activity index of the batch of raw material benzene is less than 0.9, the batch of raw material benzene needs to be mixed with normal benzene for use, and the mixing ratio of abnormal benzene to normal benzene is 1:a*(1 / γ-1), the coefficient a is 1-3, preferably 1, so that the mixed benzene after mixing does not affect the nitrobenzene hydrogenation catalyst.

[0048] The application will be further explained by more specific examples below, but not constitute any limitation.

[0049] Example 1

[0050] The newly arrived raw material benzene was analyzed by gas phase analysis, and the heavy component content was 29mm, which belonged to abnormal benzene. The batch of abnormal benzene was distilled and concentrated by 30 times at 80℃, then 0.0045g of hydrogenation catalyst, 15g of nitrobenzene, 5g of benzene concentrate, 30ml of water and 50ml of ethanol were added into the hydrogenation reactor, 30bar of hydrogen was injected into the reactor, the stirring speed was set to 900rpm, and the time when the reactor pressure dropped by 5bar, 10bar, 15bar and 20bar was recorded as 780s, 1690s, 3090s and 5290s respectively, and the κ activity factor of the batch of benzene was calculated as 1 / (780)+1 / (1690-780)+1 / (3090-1690)+1 / (5290-3090)=0.0017. According to the above method, the κ activity factor of normal benzene concentrate was 0.018. The γ relative activity index of the batch of benzene was calculated as 0.0017 / 0.018=0.094<0.9, and the batch of benzene could not be directly used, and the hydrogenation catalyst activity of nitrobenzene was greatly affected. It was suggested that the batch of abnormal benzene should be mixed with normal benzene for use, and the minimum mixing ratio was abnormal benzene: normal benzene = 1:1 / 0.094-1=1:9.6. The adiabatic nitration reaction (benzene and nitric acid reacted to generate nitrobenzene in 70% sulfuric acid as catalyst, reaction temperature 130℃, benzene molar quantity was 8% more than nitric acid) was carried out according to the mixing ratio of abnormal benzene: normal benzene 1:10 and 1:20 respectively, and nitrobenzene product was obtained. The liquid phase hydrogenation reaction (nitrobenzene and hydrogen reacted to generate aniline in palladium platinum catalyst, reaction temperature 200℃, reaction pressure 1.65Mpa, hydrogen / nitrobenzene molar ratio 3.4) was carried out with nitrobenzene as raw material. During the hydrogenation reaction, the hydrogenation catalyst consumption did not increase significantly, while when the abnormal benzene was directly used, the catalyst consumption increased sharply, and the reactor fluctuated violently.

[0051]

[0052]

[0053] Example 2

[0054] The new arrival raw material benzene was analyzed by gas phase analysis, and the heavy component content was 17mm, which belonged to abnormal benzene. The batch of abnormal benzene was concentrated 25 times at 80℃, then 0.0045g of hydrogenation catalyst, 15g of nitrobenzene, 5g of benzene concentrate, 30ml of water and 50ml of ethanol were added into the hydrogenation reactor, 35bar of hydrogen was injected into the reactor, the stirring speed was set to 900rpm, and the time when the reactor pressure dropped by 5bar, 10bar, 15bar and 20bar was recorded as 229s, 487s, 769s and 1084s respectively, and the κ activity factor of the batch of benzene was calculated as 1 / (229)+1 / (487-229)+1 / (769-487)+1 / (1084-769)=0.015. According to the above method, the κ activity factor of normal benzene concentrate was 0.018. The γ relative activity index of the batch of benzene was calculated as 0.015 / 0.018=0.83<0.9, which could not be directly used, and the hydrogenation catalyst activity of nitrobenzene was greatly affected. It was suggested that the batch of abnormal benzene should be mixed with normal benzene, and the minimum mixing ratio was abnormal benzene: normal benzene=1:1 / 0.83-1=1:0.2. When the mixing ratio of abnormal benzene: normal benzene was 1:0.2 and 1:0.6 respectively, the hydrogenation catalyst consumption did not increase significantly, while when the abnormal benzene was directly used, the catalyst consumption increased and the reactor fluctuated slightly.

[0055] Regime of use Catalyst specific consumption g / t aniline Hydrogenation reaction behaviour Normal benzene Direct use 8 Stable Abnormal benzene Direct use 9.6 Severe fluctuations Abnormal benzene : normal benzene 1:0.2 8.3 Stable Abnormal benzene : normal benzene 1:0.6 8.1 Stable

[0056] Example 3

[0057] The new arrival raw material benzene was analyzed by gas phase analysis, and the heavy component content was 18mm, which belonged to abnormal benzene. The batch of abnormal benzene was concentrated 25 times at 80℃, then 0.0045g of hydrogenation catalyst, 15g of nitrobenzene, 5g of benzene concentrate, 30ml of water and 50ml of ethanol were added into the hydrogenation reactor, 25bar of hydrogen was injected into the reactor, the stirring speed was set to 900rpm, and the time when the reactor pressure dropped by 5bar, 10bar, 15bar and 20bar was recorded as 196s, 416s, 661s and 931s respectively, and the κ activity factor of the batch of benzene was calculated as 1 / (196)+1 / (416-196)+1 / (661-416)+1 / (931-661)=0.0174. According to the above method, the κ activity factor of normal benzene concentrate was 0.018. The γ relative activity index of the batch of benzene was calculated as 0.00174 / 0.018=0.97>0.9, which could be directly used, and the hydrogenation catalyst consumption of nitrobenzene did not increase significantly in actual application, and the system was stable.

[0058] Regime of use Catalyst specific consumption g / t aniline Hydrogenation reaction behaviour Normal benzene Direct use 8 Stable Abnormal benzene Direct use 8.2 Stable

[0059] Although the present application has been described in detail through the preferred embodiments, it should be appreciated that the above description is not to be construed as limiting the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A method for evaluating the influence of a raw material benzene p-nitrobenzene hydrogenation catalyst, characterized by, The method comprises the following steps: 1) Quality monitoring of raw benzene: analyzing the content of heavy components in any batch of raw benzene, when the content of heavy components is less than or equal to 10 ppm, it is determined that the batch of raw benzene has no effect on the p-nitrobenzene hydrogenation catalyst; when the content of heavy components is greater than 10 ppm, it is determined that the batch of raw benzene may have an effect on the p-nitrobenzene hydrogenation catalyst, and then the activity of the raw benzene needs to be further evaluated; 2) Activity evaluation of raw benzene: distilling and concentrating the raw benzene, and then evaluating the effect of the concentrated liquid on the activity of the p-nitrobenzene hydrogenation catalyst to obtain the activity factor κ and the relative activity index γ of the concentrated liquid; The evaluation method of the activity of the raw benzene concentrated liquid is as follows: 0.0045 g of hydrogenation catalyst, 15 g of p-nitrobenzene, 5 g of benzene concentrated liquid, 30 ml of water and 50 ml of ethanol are added into a reaction kettle, the reaction kettle is pressurized to 25-35 bar of hydrogen, the temperature of the reaction kettle is raised to 100 DEG C, then the stirring speed is set to 900 rpm, the p-nitrobenzene is continuously reacted with hydrogen under the action of the catalyst, and the time when the pressure of the reaction kettle drops by 5 bar, 10 bar, 15 bar and 20 bar is recorded as T5, T10, T15 and T20 respectively; the relative activity index calculation model of the raw benzene concentrated liquid is as follows: κ activity factor = 1 / (T5) + 1 / (T10-T5) + 1 / (T15-T10) + 1 / (T20-15); γ relative activity index = κ abnormal benzene activity factor / κ normal benzene activity factor; When the relative activity index γ of the batch of raw benzene is greater than or equal to 0.9, it is determined that the batch of raw benzene with excessive heavy components has no effect on the p-nitrobenzene hydrogenation catalyst; When the relative activity index γ of the batch of raw benzene is less than 0.9, it is determined that the batch of raw benzene with excessive heavy components has an effect on the p-nitrobenzene hydrogenation catalyst; The content of heavy components in the raw benzene is the total content of substances with carbon number greater than 9. In step 1), the content of heavy components in the raw benzene is detected by gas chromatography, the chromatographic column is Agilent 19095J-323: 300 DEG C: 30 m x 530 um x 1.5 um, the carrier gas is nitrogen, the flow rate is 3 ml / min, the detector is FID, the detection temperature is 300 DEG C, and the programmed temperature rising is 50 DEG C for 2 min, 8 DEG C / min to 80 DEG C for 1 min, 15 DEG C / min to 300 DEG C for 10 min.

2. The evaluation method according to claim 1, characterized by The purity and impurity content of the raw benzene are calculated by area normalization.

3. The evaluation method according to claim 2, characterized by, In step 2), the method for distilling and concentrating the raw benzene is as follows: 300-600 g of raw benzene is added into a three-necked flask, the temperature of the heating device is raised to 75-95 DEG C, and the benzene is continuously vaporized to obtain a concentrated liquid, and the concentration multiple is controlled to be 25-35 times.

4. The evaluation method according to claim 1, characterized by In step 2), the method for distilling and concentrating the raw benzene is as follows: 300-600 g of raw benzene is added into a three-necked flask, the temperature of the heating device is raised to 80 DEG C, the benzene is continuously vaporized to obtain a concentrated liquid, and the concentration multiple is controlled to be 30 times.

5. The evaluation method according to claim 4, characterized by The reaction kettle is pressurized to 30 bar of hydrogen.

6. The evaluation method according to claim 1, characterized by ​ 7. A method for producing aniline, comprising the steps of producing nitrobenzene by nitration of a raw material benzene, and producing aniline by hydrogenation of the nitrobenzene, characterized by, The effect of the raw material benzene on the nitrobenzene hydrogenation catalyst is first evaluated using the method described in any one of claims 1 to 6, and then the method of using the raw material benzene is determined.

8. The production method according to claim 7, characterized by, When the content of heavy components in the raw benzene is less than or equal to 10 ppm, the batch of raw benzene can be used directly. After nitration, benzene is obtained as nitrobenzene, which will not affect the hydrogenation catalyst.

9. The production method according to claim 7, characterized by, When the content of heavy components in the raw benzene is greater than 10 ppm, the activity of the batch of raw benzene is further evaluated.

10. The production method according to claim 9, characterized by, If the relative activity index γ of the benzene in this batch is greater than or equal to 0.9, then the benzene in this batch with excessive heavy components can be used directly. If the relative activity index of benzene in this batch of raw materials is less than 0.9, then normal benzene must be used in a certain proportion for this batch of raw materials.

11. The production method according to claim 10, characterized by, The calculation model for the blending ratio is: Abnormal benzene: Normal benzene = 1:a*(1 / γ-1), where the coefficient of a is 1-3.

12. The production method according to claim 10, characterized by, The calculation model for the blending ratio is: Abnormal benzene : Normal benzene = 1 : a*(1 / γ-1), where the coefficient of a is 1.

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