Bifunctional catalyst for aniline alkylation co-production of hydrogen

Abstract

The invention relates to the technical field of catalyst preparation, in particular to a bifunctional catalyst for aniline alkylation co-production of hydrogen. The preparation method of the catalyst comprises the following steps: carrying out two parallel flow co-precipitation reactions on a salt solution containing copper, zinc, aluminum, chromium and manganese and an alkaline solution, and aging to obtain a reaction slurry; filtering the reaction slurry, adding hot desalted water for pulping, filtering again after pulping is completed, and carrying out colloid mill treatment on the filter cake to obtain catalyst slurry; carrying out spray drying on the catalyst slurry to obtain a catalyst precursor; calcining the catalyst precursor, and forming to obtain the copper-based bifunctional catalyst. The catalyst is used for co-production of hydrogen through aniline alkylation. The catalyst prepared by the method provided by the invention takes aniline alkylation byproduct wastewater as a raw material for co-production of hydrogen. The whole procedure is simple, operation is convenient, the production process is continuous, the productivity is large, and the production efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, in particular to a bifunctional catalyst for aniline alkylation and co-production of hydrogen. Background Art

[0002] In the 1950s, the first N-methylaniline production unit in my country was built in Taiyuan Chemical Plant with assistance from the Soviet Union. It used a gas-phase catalytic method and Cu-Mn catalysts, and the product was used as a neutralizer for explosives. However, the catalyst had a short service life and had to be regenerated every 200-300 hours, with a total service life of 1000-2000 hours. In 1983, the CNW-1 aniline N-alkylation catalyst of Southwest Institute was officially used in the industrial unit of Taiyuan Chemical Plant. The catalyst has high catalytic activity, good selectivity, long service life, and better performance than the original catalyst. After years of use, it has been confirmed that the CNW-1 catalyst has excellent performance, with a conversion rate of generally 90% to 96% and a selectivity of 95% to 98%, and won the second prize of Sichuan Science and Technology Progress.

[0003] Based on the original technology, Southwest Institute has optimized and improved the process, which can realize the combined conversion of aniline alkylation and methanol steam cracking in the same reactor, and produce hydrogen as a by-product while synthesizing N-methylaniline with high selectivity, meeting the application needs of different scenarios. The catalyst uses copper metal as the main active center, combines the alkylation function with the methanol cracking function, and makes the spatial distance between the two active sites close, so that the products of methanol cracking reaction and methanol alkylation reaction, that is, carbon monoxide and water, are fully contacted, so that the water generated by the alkylation reaction quickly reacts with the carbon monoxide generated by the cracking reaction at the catalyst change active site to generate carbon dioxide and hydrogen. In this process, the hydrogen molecule is small and quickly leaves the reaction active center, pushing the reaction to the right. The product quickly leaves the catalyst active center, pulling fresh raw materials into the active center again to complete the next round of reaction. In this process, methanol is in excess, and the catalyst active center is adjusted to make the methanol cracking reaction conversion rate slightly higher than the alkylation reaction, generate relatively more carbon monoxide, consume water as much as possible, and generate more hydrogen. At the same time, the active sites of the alkylation reaction need to be highly selective to ensure that N-methylaniline and N,N-dimethylaniline react in series, so that excessive generation of N,N-dimethylaniline will not cause consumption of N-methylaniline, and the ton consumption remains unchanged.

[0004] The aniline alkylation process is an exothermic reaction, and methanol steam cracking is an endothermic reaction. After combining the two, the energy consumption of the entire production line is the same as that of traditional alkylation production. There is no need to add additional heat or circulating cooling capacity, and the energy consumption remains unchanged.

[0005] The alkylation process of aniline generates about 0.17 tons of wastewater per ton of product. Since aniline and other materials are slightly soluble in water, the COD of wastewater from traditional production lines is around 30,000, which is a high-concentration organic wastewater with high treatment costs. The current treatment cost is 100-150 yuan / ton, and the environmental protection equipment is complex and occupies a large area. One of the raw materials used for co-production of hydrogen is by-product water. Through process adjustments, there is no wastewater discharge during normal operation of the entire production line. The wastewater is converted into hydrogen, reducing the direct operating cost of the product by about 15% and improving product competitiveness. Summary of the invention

[0006] The purpose of the present invention is to provide a bifunctional catalyst for the alkylation of aniline to produce hydrogen. In the process of preparing the catalyst, the present application combines coprecipitation and spray drying to improve the catalytic performance of the catalyst, and has a good effect when it is used for the alkylation of aniline to produce hydrogen.

[0007] In order to achieve the above invention object, the specific technical solution of the present invention is:

[0008] A method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen comprises the following steps:

[0009] 1) First, nitrates containing copper, zinc, chromium and manganese are dissolved in water to obtain a metal salt mixed solution I;

[0010] 2) Next, nitrates containing copper, zinc and aluminum are dissolved in water to obtain a metal salt mixed solution II;

[0011] 3) preparing an alkaline solution;

[0012] 4) Preheating the metal salt mixed solution I in step 1), the metal salt mixed solution II in step 2), and the alkaline solution in step 3) respectively, and then subjecting the metal salt mixed solution I to a first stage of co-current co-precipitation reaction with the alkaline solution, and then aging the slurry obtained by the reaction; then, based on the first stage of co-current co-precipitation, subjecting the metal salt mixed solution II to a second stage of co-current co-precipitation reaction with the alkaline solution, and then aging the slurry obtained by the reaction;

[0013] 5) filtering the aged reaction slurry, adding hot desalted water for pulping, and filtering again after pulping to obtain a filter cake;

[0014] 6) The filter cake is subjected to colloidal milling to obtain a catalyst slurry; the catalyst slurry is spray-dried to obtain a catalyst precursor; the catalyst precursor is calcined and formed to obtain a copper-based bifunctional catalyst, which is used for aniline alkylation and co-production of hydrogen.

[0015] According to an embodiment of the method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen of the present invention, in step 3), the alkaline solution is a solution obtained by dissolving sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate in water.

[0016] According to an embodiment of the method for preparing a bifunctional catalyst for the alkylation of aniline and the co-production of hydrogen of the present invention, in step 4), the preheating temperatures of the metal salt mixed solution I, the metal salt mixed solution II and the alkaline solution are all 65-80°C; the temperatures of the two-stage co-precipitation reactions are both 65-80°C and the pH value is 7.5-8.5, and the aging time is 45-90 minutes.

[0017] According to an embodiment of the method for preparing a bifunctional catalyst for the alkylation of aniline and the co-production of hydrogen of the present invention, in step 5), the reaction slurry is filtered and then added with hot desalted water for slurrying. After the slurrying is completed, it is filtered again, and the slurrying and filtering are repeated 2 to 3 times until the total content of sodium and potassium ions in the filter cake drops below 0.01wt%.

[0018] According to an embodiment of the method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen of the present invention, in step 6), desalted water or a sodium carbonate aqueous solution with a mass concentration of 0.03-0.08% is added to the filter cake for colloid mill treatment, wherein the gap of the colloid mill is 0.1-1.0 mm, and the amount of desalted water or sodium carbonate aqueous solution added is 1-10 times the volume of the filter cake.

[0019] According to an embodiment of the method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen of the present invention, in step 6), the inlet air temperature of the spray drying is 180-250° C., and the feed rate is 500-1000 ml / h; the volume ratio of the catalyst slurry to water during the spray drying process is 1:1-1:5.

[0020] According to an embodiment of the method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen of the present invention, in step 6), the calcination temperature is 210-400° C. and the calcination time is 3-6 hours; graphite and water are added and pressed into tablets to obtain the bifunctional catalyst.

[0021] According to an embodiment of the method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen of the present invention, the method further comprises a step of evaluating the activity of the bifunctional catalyst.

[0022] According to an embodiment of the method for producing hydrogen by the bifunctional catalyst for aniline alkylation of the present invention, in the step of activity evaluation, the catalyst activity is evaluated on a fixed bed and the reaction product is analyzed by gas chromatography. The test conditions include: a temperature of 190 to 270° C., a raw material liquid volume space velocity of 0.3 to 3 h -1 .

[0023] Compared with the prior art, the present invention has the following positive effects:

[0024] The catalyst prepared by the present invention is used to use the wastewater produced as a by-product of aniline alkylation as a raw material to co-produce hydrogen. The overall process is simple, the operation is convenient, the production process is continuous, the production capacity is large and the production efficiency is high. The catalyst can be used in the same reactor to realize the combined conversion of aniline alkylation and methanol steam cracking, and high-purity hydrogen is produced as a by-product while synthesizing N-methylaniline with high selectivity, without wastewater discharge, and meeting the application requirements of different scenarios. Compared with the traditional alkylation production line, the energy consumption and ton consumption remain unchanged, and the cost of converting wastewater into hydrogen is reduced by about 15%. DETAILED DESCRIPTION

[0025] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0026] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0027] According to an exemplary embodiment of the present invention, the method for producing a bifunctional catalyst for the alkylation of aniline and co-production of hydrogen mainly includes two parts of treatment: co-precipitation and spray drying, and specifically includes the following steps.

[0028] Step A:

[0029] A salt solution containing copper, zinc, aluminum, chromium and manganese is subjected to two parallel co-precipitation reactions with an alkaline solution, followed by aging to obtain a reaction slurry, wherein the atomic ratio between the solutes of copper, zinc, aluminum, chromium and manganese is Cu:Zn:Al:Cr:Mn=(0.5-2):(0.3-1):(0.03-0.5):(0.03-0.5):(0.001-0.01).

[0030] According to the present invention, the salt solution containing copper, zinc, aluminum, chromium and manganese is a solution obtained by dissolving their nitrates in water, and the alkaline solution is a solution obtained by dissolving sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate in water, and the alkaline solution is preferably an aqueous solution of sodium carbonate. Preferably, desalted water is used to prepare the above solution, and the salts of copper, zinc and aluminum may also be salts such as sulfates and chlorides.

[0031] This step involves the precipitation reaction of the main active components of the catalyst, wherein the temperature of the coprecipitation reaction is 65-80°C and the pH value is 7.5-8.5. Specifically, the metal salt forms a composite metal precipitate during the precipitation reaction, the first section of the coprecipitation is the aniline alkylation active site, and the second section is the methanol cracking active site with copper-zinc-aluminum as the main body. Among them, the chromium and aluminum metal precipitates are amphoteric, and too high or too low pH will affect the precipitation morphology of the metal, causing the activity of the catalyst to decrease or even deactivate. In addition, the aging time is controlled to be 45 to 90 minutes. After many experimental comparisons, this aging time can control the catalyst activity to be in the most suitable reaction range.

[0032] Step B:

[0033] The reaction slurry is slurried with hot desalted water and filtered to obtain a filter cake.

[0034] This step is to remove impurities in the reaction slurry and obtain a qualified filter cake so as to obtain a catalyst that meets the requirements in the subsequent preparation process.

[0035] Specifically, the reaction slurry is filtered and then hot desalted water is added for beating, and after beating, it is filtered again, and the beating and filtering are repeated 2 to 3 times until the sodium and potassium ion content in the filter cake is reduced to below 0.01wt%, and a qualified filter cake is obtained. In each beating, the amount of hot desalted water added is 1 to 10 times the volume of the filter cake, and the temperature of the hot desalted water is 65 to 75°C.

[0036] Step C:

[0037] The filter cake is subjected to colloid milling to obtain catalyst slurry.

[0038] The main purpose of the colloid mill treatment is to reduce the particle size of the catalyst and change the particle shape, so that the catalyst particles are evenly dispersed, thereby improving the catalyst performance. Specifically, desalted water or a sodium carbonate aqueous solution with a mass concentration of 0.03-0.08% is added to the filter cake for colloid mill treatment, wherein the gap of the colloid mill is 0.1-1.0 mm, and the amount of desalted water or sodium carbonate aqueous solution added is 1-10 times the volume of the filter cake.

[0039] Step D:

[0040] The catalyst slurry is spray-dried to obtain a catalyst precursor.

[0041] Spray drying is an effective means to prepare fine particle catalysts with uniform particle size and spherical shape. It can produce catalysts with uniform particle size distribution, large specific surface area and good particle fluidity. Its specific advantages also include: 1) The raw materials are mixed in a solution state to ensure uniform distribution of components, and the process is simple, with less component loss and accurate control of the stoichiometric ratio, which is particularly suitable for preparing multi-component composite powders; 2) Micropowders are dried from droplets suspended in the air. The particles are generally regular spherical and less agglomerated, and no subsequent washing and grinding are required, which ensures the high purity and high activity of the product; 3) The entire process is completed quickly in just a few seconds, so the droplets do not have time to undergo component segregation during the reaction, further ensuring the uniformity of component distribution; 4) The process is simple, and the finished product is obtained in one step, without filtering, washing, drying, and crushing processes. The operation is simple and convenient, the production process is continuous, the production capacity is large, and the production efficiency is high, which is very conducive to large-scale industrial production.

[0042] Therefore, the present invention utilizes a scheme combining spray drying treatment with co-precipitation treatment to prepare a bifunctional catalyst with better performance.

[0043] Specifically, the inlet air temperature of the spray drying is 180-250° C., and the feed rate is 500-1000 ml / h; the volume ratio of the catalyst slurry to water during the spray drying process is 1:1-1:5.

[0044] Step E:

[0045] The catalyst precursor is calcined and formed to obtain a bifunctional catalyst.

[0046] Calcination is the process of thermally decomposing alkaline metal salts into oxides, wherein the calcination temperature is 210-400°C and the calcination time is 3-6 hours; molding can be performed by adding graphite and water for tableting to obtain a bifunctional catalyst.

[0047] According to an exemplary embodiment of the present invention, the method further comprises a step F of evaluating the activity of the bifunctional catalyst. Specifically, in step F, the catalyst activity is evaluated on a fixed bed and the reaction product is analyzed by gas chromatography. The test conditions include: a temperature of 190 to 270°C, a raw material liquid volume space velocity of 0.3 to 3 h -1 .

[0048] The method of the bifunctional catalyst for the alkylation of aniline and co-production of hydrogen of the present invention will be further described below with reference to specific examples.

[0049] Embodiment 1:

[0050] Weigh 201.51 g of hydrated copper nitrate, 144.96 g of hydrated zinc nitrate, 102.03 g of hydrated chromium nitrate and 1.21 g of hydrated manganese nitrate, dissolve them in a beaker filled with 500 mL of desalted water, add desalted water and stir to completely dissolve it, and make the volume to 2000 mL to prepare a salt solution I containing copper, zinc, chromium and manganese.

[0051] Weigh 167.74 g of sodium carbonate and 3.40 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare an alkaline solution I.

[0052] The salt solution containing copper, zinc, etc. and the alkaline solution are preheated to 75°C, and the temperature of the reaction water bath is controlled at 75°C.

[0053] Weigh 201.51 g of hydrated copper nitrate, 144.96 g of hydrated zinc nitrate and 110.62 g of hydrated aluminum nitrate, dissolve them in a beaker filled with 500 mL of desalted water, add desalted water and stir to completely dissolve them, and make the volume to 2000 mL to prepare a salt solution II containing copper, zinc and aluminum.

[0054] Weigh 171.32 g of sodium carbonate and 3.93 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare alkaline solution II.

[0055] The metal salt solution and alkaline solution are preheated to 75°C, and the reaction water bath temperature is controlled at 75°C.

[0056] When the temperature of the raw materials and the water bath reaches the required level, the metal salt solution I and the alkaline solution I are added to the reactor in parallel to perform a coprecipitation reaction and stirred vigorously. The temperature of the coprecipitation reaction is 75°C and the pH value is 7.8. After the reaction is completed, the reaction slurry I is obtained by aging for 1 hour.

[0057] On the basis of reaction slurry I, metal salt solution II and alkaline solution II were then added to the reactor in parallel to perform coprecipitation reaction and stirred vigorously. The temperature of the coprecipitation reaction was 75° C. and the pH value was 7.8. After the reaction was completed, the reaction slurry was aged for 1 hour to obtain reaction slurry II.

[0058] The reaction slurry II after aging is filtered out of most of the mother liquor using a centrifugal filter, and then 6000 mL of desalted water is added to the filter cake for slurrying. After slurrying, centrifugal filtration is performed again. Slurrying and filtration are repeated 3 times until the sodium ion content in the filter cake drops below 0.01 wt% to obtain a qualified filter cake.

[0059] Take the qualified filter cake, add 2000 mL of sodium carbonate aqueous solution with a mass concentration of 0.03%, and then slowly add it into the colloid mill hopper for colloid mill treatment to obtain catalyst slurry.

[0060] The catalyst slurry after colloid mill treatment was sent to a spray dryer for spray drying. The inlet air temperature was adjusted to 220°C, the feed rate was adjusted to 1000ml / h, and the volume ratio of the catalyst slurry to water during the spray drying process was controlled to be 1:3. After spray drying, a catalyst precursor was obtained.

[0061] After spray drying, the catalyst precursor was taken out and placed in a calcination furnace for calcination at a temperature of 310° C. and a calcination time of 5 hours. After cooling, an appropriate amount of graphite and water were added and mixed, and then tableted to obtain 240 g of bifunctional catalyst A.

[0062] Example 2: (This is a comparative example)

[0063] Weigh 188.13 g of copper nitrate, 131.24 g of zinc nitrate and 90.62 g of aluminum nitrate, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL, and prepare a salt solution I containing copper, zinc and aluminum.

[0064] Weigh 154.91 g of sodium carbonate and 3.22 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare an alkaline solution I.

[0065] Weigh 188.13 g of hydrated copper nitrate, 131.24 g of hydrated zinc nitrate, 95.43 g of hydrated chromium nitrate and 0.86 g of hydrated manganese nitrate, dissolve them in a beaker filled with 500 mL of desalted water, add desalted water and stir to completely dissolve them, and make the volume to 2000 mL to prepare a salt solution II containing copper, zinc, chromium and manganese.

[0066] Weigh 202.17 g of potassium carbonate and 3.18 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare alkaline solution II.

[0067] The subsequent steps were carried out in the same manner as in Example 1, and finally 220 g of bifunctional catalyst B was obtained.

[0068] Embodiment 3:

[0069] Weigh 175.82 g of hydrated copper nitrate, 122.65 g of hydrated zinc nitrate, 89.19 g of hydrated chromium nitrate and 0.80 g of hydrated manganese nitrate, dissolve them in a beaker filled with 500 mL of desalted water, add desalted water and stir to completely dissolve it, and make the volume to 2000 mL to prepare a salt solution I containing copper, zinc, chromium and manganese.

[0070] Weigh 188.94 g of potassium carbonate and 2.97 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare an alkaline solution I.

[0071] Weigh 175.82 g of copper nitrate, 122.65 g of zinc nitrate and 84.69 g of aluminum nitrate, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL, to prepare a salt solution II containing copper, zinc and aluminum.

[0072] Weigh 144.78 g of sodium carbonate and 3.01 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare alkaline solution II.

[0073] The subsequent steps were carried out in the same manner as in Example 1, and finally 200 g of bifunctional catalyst C was obtained.

[0074] Embodiment 4:

[0075] Weigh 206.94 g of hydrated copper nitrate, 144.36 g of hydrated zinc nitrate and 0.95 g of hydrated manganese nitrate, dissolve them in a beaker filled with 500 mL of desalted water, add desalted water and stir to completely dissolve them, and make the volume to 2000 mL to prepare a salt solution I containing copper, zinc, chromium and manganese.

[0076] Weigh 167.39 g of potassium carbonate and 3.48 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare an alkaline solution I.

[0077] Weigh 206.94 g of copper nitrate, 144.36 g of zinc nitrate and 99.68 g of aluminum nitrate, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume up to 2000 mL, and prepare a salt solution II containing copper, zinc and aluminum.

[0078] Weigh 170.40 g of sodium carbonate and 3.54 g of sodium hydroxide, dissolve them in a beaker filled with 500 mL of desalted water, stir to completely dissolve them, add desalted water and make the volume to 2000 mL to prepare alkaline solution II.

[0079] The subsequent steps were carried out in the same manner as in Example 1, and finally 220 g of bifunctional catalyst D was obtained.

[0080] Embodiment 5:

[0081] The reaction bed temperature is 220℃, atmospheric pressure and the raw material liquid volume space velocity is 2h -1 Under the conditions of , the activity of the catalysts prepared in Example 1 and Example 2 was evaluated. The results of gas chromatography analysis are shown in Table 1.

[0082] Embodiment 6:

[0083] The reaction bed temperature is 220℃, atmospheric pressure and the raw material liquid volume space velocity is 1h -1 Under the conditions of , the activity of the catalysts prepared in Example 1 and Example 2 was evaluated. The results of gas chromatography analysis are shown in Table 1.

[0084] Embodiment 7:

[0085] The reaction bed temperature is 210℃, atmospheric pressure and the raw material liquid volume space velocity is 1h -1 Under the conditions of , the activity of the catalysts prepared in Example 1 and Example 2 was evaluated. The results of gas chromatography analysis are shown in Table 1.

[0086] Table 1 Activity and selectivity results of the catalysts prepared in Example 1 and Example 2

[0087]

[0088] From the results in Table 1, it can be seen that aniline alkylation can be combined with methanol steam cracking and converted in the same reactor to simultaneously synthesize N-methylaniline with high selectivity and co-produce high-purity hydrogen. By adjusting the process parameters and catalysts, the production line can balance the co-production products within a certain range. The traditional CNW-1 has a high yield for N-methylaniline, but high selectivity cannot produce more hydrogen. The bifunctional catalyst for aniline alkylation and hydrogen production uses copper-chromium as the main active center, combines the alkylation function with the methanol cracking function, and makes the spatial distance between the two active sites close, so that the methanol cracking reaction and the methanol alkylation reaction products, that is, carbon monoxide and water, are fully contacted, so that the water generated by the alkylation reaction quickly reacts with the carbon monoxide generated by the cracking reaction at the catalyst change active site to generate carbon dioxide and hydrogen. In this process, the hydrogen molecule is small and quickly leaves the reaction active center, pushing the reaction to the right. The product quickly leaves the catalyst active center, pulling the fresh raw material into the active center again to complete the next round of reaction. In this process, methanol is in excess. The active center of the catalyst is adjusted to make the conversion rate of the methanol cracking reaction slightly higher than that of the alkylation reaction, generate relatively more carbon monoxide, consume water as much as possible, and generate more hydrogen. However, carbon monoxide cannot be too much in the tail gas to cause waste. Through research, the concentration of carbon monoxide in the tail gas can be controlled within 5%, and efficiently converted into carbon dioxide. At the same time, the active site of the alkylation reaction needs to be highly selective to ensure that N-methylaniline and N, N-dimethylaniline are carried out in a series reaction form. Under the conditions of high methanol and low water, N, N-dimethylaniline will not be excessively generated to cause the consumption of N-methylaniline. The catalyst can convert the by-product water produced into hydrogen. The entire process does not need to discharge by-product water, and even a certain amount of supplementary water is required for the surplus. While synthesizing N-methylaniline with high selectivity, the maximum amount of co-production of high-purity hydrogen is increased by more than 500%, allowing the product to produce more hydrogen to meet the needs under different working conditions. This result explains that the rational arrangement of the spatial positions of various active centers of copper metal at the nanoscale can effectively improve the atomic utilization efficiency of the catalyst and provide a new approach for the design of bifunctional catalysts for alkylation-cracking transformation.

[0089] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0090] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen, characterized in that: The following steps are involved: 1) First, nitrates containing copper, zinc, chromium and manganese are dissolved in water to obtain a metal salt mixed solution I; 2) Next, nitrates containing copper, zinc and aluminum are dissolved in water to obtain a metal salt mixed solution II; 3) preparing an alkaline solution; 4) preheating the metal salt mixed solution I in step 1), the metal salt mixed solution II in step 2), and the alkaline solution in step 3); Then, the metal salt mixed solution I and the alkaline solution are subjected to a first stage of co-current co-precipitation reaction, and the slurry obtained by the reaction is aged; then, based on the first stage of co-current co-precipitation, the metal salt mixed solution II and the alkaline solution are subjected to a second stage of co-current co-precipitation reaction, and the slurry obtained by the reaction is aged; 5) filtering the aged reaction slurry, adding hot desalted water for pulping, and filtering again after pulping to obtain a filter cake; 6) The filter cake is subjected to colloidal milling to obtain a catalyst slurry; the catalyst slurry is spray-dried to obtain a catalyst precursor; the catalyst precursor is calcined and formed to obtain a copper-based bifunctional catalyst, which is used for aniline alkylation and co-production of hydrogen.

2. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: The alkaline solution in step 3) is a solution obtained by dissolving sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate in water.

3. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: The atomic ratio of carbonate to hydroxide is 15 to 40:

1.

4. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: In step 4), the temperature of the two parallel co-precipitation reactions is 65-80° C., the pH value is 7.5-8.5, and the aging time is 45-90 minutes.

5. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: In step 5), the reaction slurry is filtered and slurried for 2 to 3 times until the total content of sodium and potassium ions in the filter cake is reduced to below 0.01 wt%.

6. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: In the reaction slurry after aging, the atoms of copper, zinc, aluminum, chromium and manganese are 0.5-2: 0.3-1: 0.03-0.5: 0.03-0.5: 0.001-0.

01.

7. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: During the colloid mill treatment in step 6), desalted water or a sodium carbonate aqueous solution with a mass concentration of 0.03-0.08% is added to the filter cake for colloid mill treatment, wherein the gap of the colloid mill is 0.1-1.0 mm, and the amount of desalted water or sodium carbonate aqueous solution added is 1-10 times the volume of the filter cake.

8. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: The inlet air temperature of the spray drying is 180-250° C., and the feed rate is 500-1000 ml / h; the volume ratio of the catalyst slurry to water during the spray drying process is 1:1-1:

5.

9. The method for preparing a bifunctional catalyst for aniline alkylation and co-production of hydrogen according to claim 1, characterized in that: The calcination temperature is 210-400°C, and the calcination time is 3-6 hours; graphite and water are added during the molding process to perform tableting.

10. A bifunctional catalyst for aniline alkylation and co-production of hydrogen prepared by the method according to any one of claims 1 to 9, characterized in that: The catalyst uses copper metal as the main active center and combines the alkylation function with the methanol cracking function. In the same reactor, it realizes the combined conversion of aniline alkylation and methanol steam cracking, producing hydrogen as a by-product while synthesizing N-methylaniline with high selectivity.

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