Method for continuously producing N, N-dimethylaniline
The catalyst is processed through the two-stage oxidation and regeneration method, which solves the problem of catalyst easy to coke inactivation, improves the stability and activity of the catalyst, and achieves continuous production and cost savings of N,N dimethylaniline.
Patent Information
- Application Number
- CN202410099053.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-11-01
- Filing Date
- 2024-01-24
- Publication Date
- 2025-05-06
AI Technical Summary
In the prior art, the catalyst is prone to coking and deactivation, and high-temperature calcination causes damage to the catalyst skeleton, affecting its stability and activity, resulting in a decrease in the selectivity and conversion rate of N,N dimethylaniline.
The catalyst to be grown is treated with two-stage oxidation and regeneration method. First, one oxidation and regeneration is performed under oxygen-containing and alkaline atmosphere, and then two-stage oxidation and regeneration is performed under oxygen-containing and phosphine to remove hard carbon on the catalyst, reduce the calcination temperature, and extend the service life of the catalyst.
It effectively improves the stability and activity of the catalyst, extends the service life of the catalyst, realizes continuous production of N,N dimethylaniline, and reduces production costs.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of synthesizing N,N-dimethylaniline, and in particular to a method for continuously producing N,N-dimethylaniline. Background Art
[0002] The N-alkylation of aniline is a commercially important chemical reaction. The product N,N-dimethylaniline produced by the N-alkylation of aniline can be used in the production of many important industrial products such as papermaking, textile dyes, medicines, fragrances and explosives.
[0003] The current mainstream preparation methods are the liquid phase method with sulfuric acid as the catalyst and the gas phase method with aniline and methanol. Among them, the liquid phase method with sulfuric acid as the catalyst is prepared by reacting aniline and methanol in a high-pressure reactor at high temperature and high pressure. This method has a high raw material conversion rate. The catalyst for the gas phase method is generally metal oxides, metal salts, molecular sieves, etc. It was first successfully developed in India, and the product selectivity is about 90%.
[0004] However, both methods have certain defects. For example, the main disadvantage of the liquid phase method is that it cannot be produced continuously. The reaction is carried out under high pressure, and the equipment and materials that are corrosion-resistant and high-pressure-resistant need to be selected, which increases the investment. A large amount of acid-soluble oil is produced during the production process. The separated products need to use a large amount of liquid alkali to neutralize the inorganic acid and produce a large amount of difficult-to-handle inorganic salts. The subsequent treatment cost is high and brings certain safety hazards and greater environmental pressure. The product selectivity of the gas phase method is lower than that of the liquid phase method, and it has not been able to achieve large-scale industrial application.
[0005] Normally, molecular sieves are used as catalysts in the gas phase method to synthesize N,N-dimethylaniline. Molecular sieves have a regular three-dimensional pore structure. Their suitable acidity and low price are conducive to the diffusion of reactant molecules in the molecular sieve pores and the reaction at the acid center. Molecular sieve catalysts are widely used in the fields of petrochemicals, especially in catalytic cracking, hydrogenation, reforming, isobutane ethylene alkylation, benzene and olefin alkylation, etc. Therefore, the research on molecular sieve catalysts not only has important academic value, but also has broad application prospects.
[0006] Some research has also been conducted in my country. Wu Kerui et al. reported the use of modified ZSM-5 as a catalyst at normal pressure, temperature 300 ° C, and liquid space velocity of 1.0 h -1 When the molar ratio of aniline to methanol is 1:3, the selectivity of dimethylaniline is 88%.
[0007] Li Guotao et al. used β molecular sieve as catalyst, at n(aniline):n(methanol)=1:3, reaction temperature 240℃-250℃ and space velocity 0.5h -1Under the conditions of , the raw material conversion rate is about 99% and the product selectivity is 85%. The catalyst conversion rate and product selectivity are low, and the conversion rate and selectivity decrease rapidly as the reaction proceeds. How to improve product selectivity and catalyst stability is a problem that molecular sieve catalysts need to solve.
[0008] Solid acid catalysts are prone to coking and deactivation, and need to be regenerated frequently. The regeneration methods of deactivated catalysts generally include hydrogenation regeneration, reaction solvent dissolution cleaning, high-temperature oxidation roasting, oxidant cleaning, etc. Among them, hydrogenation regeneration and reaction solvent dissolution cleaning regeneration are easier to achieve in industry, while high-temperature roasting is only suitable for catalysts with good thermal stability.
[0009] The coking reaction on the catalyst starts with the alkylation of N,N-dimethylaniline and methanol to form N,N,C-trimethylaniline, and then continues with hydrogen transfer, alkylation and cyclization to form coke deposits with a multi-ring structure that are difficult to volatilize. These carbon deposits are called hard coke, which are generally difficult to remove and require high-temperature oxidative roasting to remove the carbon deposits on the catalyst. High-temperature roasting of general catalysts will destroy the structure of the catalyst, thereby destroying the activity and stability of the catalyst. Summary of the invention
[0010] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for continuously producing N,N-dimethylaniline, which can realize the oxidation regeneration of the catalyst, improve the stability of the catalyst, and realize the long-term and continuous production of N,N-dimethylaniline.
[0011] In order to achieve the above object, the present invention provides a method for continuously producing N,N-dimethylaniline, wherein the method comprises: synthesizing the N,N-dimethylaniline and oxidizing and regenerating the catalyst to be regenerated, and returning the regenerated catalyst obtained by oxidizing and regenerating to the synthesis cycle of N,N-dimethylaniline for reuse;
[0012] The synthesis of N,N-dimethylaniline comprises: in the presence of a fresh catalyst, reacting the reaction raw materials methanol and aniline in a gas phase to obtain a catalyst to be produced; the fresh catalyst comprises a molecular sieve, a carrier and a modified component, the modified component is copper and phosphorus, and the acid content of the medium-strong acid in the fresh catalyst accounts for more than 35% of the total acid content;
[0013] The oxidation regeneration comprises: subjecting the catalyst to be regenerated to two-stage oxidation regeneration to obtain a regenerated catalyst.
[0014] S1, subjecting the catalyst to be regenerated to a stage of oxidation regeneration in an oxygen-containing atmosphere and an alkaline atmosphere and optionally in the presence of phosphine;
[0015] S2. The product obtained in step S1 is subjected to two-stage oxidation regeneration in an oxygen-containing atmosphere and phosphine.
[0016] The inventors of the present invention have found in their research that high-temperature calcination has a negative impact on the P and Cu sites loaded on the phosphorus and copper modified catalysts. After multiple high-temperature calcinations, the P in the catalyst will escape, while the Cu sites will agglomerate to a certain extent, which will affect the subsequent activity and hydrothermal stability of the catalyst.
[0017] The method of the present invention performs two-stage oxidation regeneration on the spent catalyst, can remove hard carbon deposited on the spent catalyst, effectively reduce the temperature required for calcination, reduce the damage to the catalyst skeleton caused by continuous high-temperature calcination, extend the catalyst life, and realize the continuous production of N,N-dimethylaniline. DETAILED DESCRIPTION
[0018] The endpoints and any values of the ranges disclosed in this article 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 each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.
[0019] The present invention provides a method for continuously producing N,N-dimethylaniline, wherein the method comprises: synthesizing the N,N-dimethylaniline and oxidizing and regenerating a catalyst to be regenerated, and returning the regenerated catalyst obtained by oxidizing and regenerating to the synthesis cycle of the N,N-dimethylaniline for reuse;
[0020] The synthesis of N,N-dimethylaniline comprises: in the presence of a fresh catalyst, reacting the reaction raw materials methanol and aniline in a gas phase to obtain a catalyst to be produced; the fresh catalyst comprises a molecular sieve, a carrier and a modified component, the modified component is copper and phosphorus, and the acid content of the medium-strong acid in the fresh catalyst accounts for more than 35% of the total acid content;
[0021] The oxidation regeneration comprises: subjecting the catalyst to be regenerated to two-stage oxidation regeneration to obtain a regenerated catalyst.
[0022] The inventors of the present invention have found in their research that high-temperature calcination has a negative impact on the P and Cu sites loaded on the phosphorus and copper modified catalysts. After multiple high-temperature calcinations, the P in the catalyst will escape, while the Cu sites will agglomerate to a certain extent, which will affect the subsequent activity and hydrothermal stability of the catalyst.
[0023] The method of the present invention performs two-stage oxidation regeneration on the spent catalyst, can remove hard carbon deposited on the spent catalyst, effectively reduce the temperature required for calcination, reduce the damage to the catalyst skeleton caused by continuous high-temperature calcination, extend the catalyst life, and realize the continuous production of N,N-dimethylaniline.
[0024] In the present invention, it should be noted that the gas phase reaction refers to that the reaction raw materials methanol and aniline are fed in gaseous form or the reaction conditions during the reaction process make methanol and aniline in gaseous state. The present invention does not specifically limit the gasification method of the raw materials, and the conventional methods defined in the art can be applied to the present invention.
[0025] In the present invention, the catalyst acid distribution is characterized by NH3 programmed temperature desorption method (NH3-TPD). The characterization method is as follows: Instrument: Quantachrome Chemstar TPx Test process: Weigh 0.15g (20-40 mesh) of molecular sieve or catalyst sample, heat it to 550℃, dry it, and then reduce it to 100℃ to make the catalyst saturated with NH3, heat it to 250℃, 350℃, 450℃ and 550℃ respectively to desorb NH3, and use TCD detector to detect NH3 concentration. The adsorption curves obtained at different temperature sections are integrated, and the instrument automatically calculates the acid density distribution at different temperatures. Among them, the acid amount obtained by integration at 250℃ is weak acid, 250℃-450℃ is medium-strong acid, and 450℃-550℃ is strong acid.
[0026] In the present invention, there is no particular limitation on the amount of the reaction raw materials. Preferably, the molar ratio of methanol to aniline is 1-10:1, preferably 2-8:1.
[0027] In the present invention, the selection range of the synthesis conditions of N,N-dimethylaniline is relatively wide. Preferably, the synthesis conditions of N,N-dimethylaniline include: a reaction temperature of 220-300°C, a mass space velocity of methanol and aniline of 0.1-10h -1 .
[0028] In the present invention, preferably, when the conversion rate of aniline is lower than 95%, the spent catalyst is obtained.
[0029] In the present invention, the oxidation regeneration is divided into two stages, and the gas atmosphere and conditions of the two stages of oxidation regeneration are controlled to reduce the influence of high temperature roasting on the spent catalyst, thereby achieving oxidation regeneration of the spent catalyst and increasing the service life of the catalyst. Preferably, the oxidation regeneration includes:
[0030] S1, subjecting the catalyst to be regenerated to a stage of oxidation regeneration in an oxygen-containing atmosphere and an alkaline atmosphere, wherein the alkaline atmosphere is ammonia and / or methylamine;
[0031] S2, subjecting the product obtained in step S1 to secondary oxidation regeneration in the presence of phosphine and optionally an oxygen-containing atmosphere.
[0032] The method provided by the present invention introduces an alkaline atmosphere during oxidation regeneration, and NH3 forms chemical adsorption at P and Cu sites, thereby reducing the damage to the molecular sieve catalyst under high-temperature roasting conditions and inhibiting Cu from agglomerating under high-temperature conditions; at the same time, phosphine is added to undergo a decomposition reaction at 500°C, and the decomposed P can react with the molecular sieve to supplement the P lost in the molecular sieve framework and improve the acidity and stability of the catalyst, while the obtained H2 can decompose with Cu to form hydrogen free radicals (H·), thereby removing hard carbon deposited on the catalyst, effectively reducing the temperature required for roasting, reducing the damage to the catalyst framework caused by continuous high-temperature roasting, and extending the catalyst life.
[0033] In the present invention, the alkaline atmosphere has a wide range of choices, and the alkaline atmospheres conventionally defined in the art are applicable to the present invention. Preferably, in step S1, the alkaline atmosphere is ammonia.
[0034] In the present invention, preferably, in step S1, based on the total amount of the oxygen-containing atmosphere and the alkaline atmosphere, the content of the alkaline atmosphere is 0.1-95% by volume, and the concentration of the oxygen-containing atmosphere is 5-99.9% by volume; further preferably, in step S1, based on the total amount of the oxygen-containing atmosphere and the alkaline atmosphere, the content of the alkaline atmosphere is 1-90% by volume, and the concentration of the oxygen-containing atmosphere is 10-99% by volume.
[0035] In the present invention, the range of conditions for the one-stage oxidation regeneration is relatively wide. Preferably, in step S1, the one-stage oxidation regeneration conditions include: the volume space velocity of the oxygen-containing atmosphere and the alkaline atmosphere is 0.01-10h -1 , the heating rate is 0.1-50℃ / min, the constant temperature is 450-550℃, and the constant temperature time is 0.5-48h; further preferably, the conditions of the first stage oxidation regeneration include: the volume space velocity of the oxygen-containing atmosphere and the alkaline atmosphere is 0.1-10h -1 , the heating rate is 0.1-10℃ / min, the constant temperature is 450-550℃, and the constant temperature time is 8-48h.
[0036] In the present invention, the oxygen-containing atmosphere has a wide range of choices. Preferably, in step S1 and step S2, the oxygen-containing atmosphere is independently selected from air and / or oxygen. In the present invention, the concentration of oxygen in the oxygen-containing atmosphere is not particularly limited, and those skilled in the art can adjust it according to actual needs.
[0037] In the present invention, preferably, in step S2, based on the total amount of phosphine and optionally the oxygen-containing atmosphere, the content of phosphine is 0.1-100% by volume, and the content of the oxygen-containing atmosphere is 0-99.9% by volume; further preferably, in step S2, based on the total amount of phosphine and optionally the oxygen-containing atmosphere, the content of phosphine is 50-100% by volume, and the content of the oxygen-containing atmosphere is 0-50% by volume.
[0038] In the present invention, the conditions for the second-stage oxidation regeneration can be selected in a wide range. Preferably, in step S2, the conditions for the second-stage oxidation regeneration include: the volume space velocity of the phosphine and optionally the oxygen-containing atmosphere is 0.1-15h -1 , the heating rate is 0.1-15°C / min, the constant temperature is 500-700°C, and the constant temperature time is 0.5-12h; further preferably, the conditions of the second-stage oxidation regeneration include: the volume space velocity of the phosphine and optionally the oxygen-containing atmosphere is 0.1-10h -1 , the heating rate is 0.1-10℃ / min, the constant temperature is 550-700℃, and the constant temperature time is 2-12h.
[0039] In the present invention, preferably, the amount of medium-strong acid in the fresh catalyst accounts for 40-50% of the total acid amount, and more preferably 42-45%.
[0040] In the present invention, there is no particular limitation on the preparation method of the fresh catalyst. Preferably, the preparation method of the fresh catalyst comprises: (1) mixing a molecular sieve and a carrier to obtain a mixture; (2) mixing the mixture obtained in step (1) with a solution containing a copper precursor and a phosphorus-containing compound to form a mixture, and then calcining the mixture once to obtain a fresh catalyst.
[0041] The method provided by the present invention increases the ratio of medium and strong acids in the catalyst by introducing copper, reduces the ratio of strong acids, can reduce the adsorption of methanol with greater polarity at acidic sites, reduce the occurrence of side reactions, and improve the life of the catalyst; further synergizes phosphorus modification to improve the hydrothermal stability of the catalyst under high temperature conditions, does not have a negative impact on the acidity and stability of the catalyst itself, and achieves long-term continuous operation of the catalyst, which is conducive to industrial continuous production and greatly saves production costs. The method provided by the present invention controls the order of adding raw materials during the catalyst preparation process, strictly follows the first mixing of molecular sieves and carriers, and directly mixes and molds the catalyst with a solution containing a copper precursor and a phosphorus-containing compound without roasting, and only needs to be roasted once during the catalyst preparation process, avoiding the multiple roastings of the catalyst after the catalyst is formed and modified in the prior art, reducing the difficulty of the catalyst preparation process and reducing energy consumption.
[0042] In the present invention, the molecular sieve has a wide range of selection. Preferably, in step (1), the molecular sieve is selected from at least one of Y-type molecular sieve, ZSM-5 type molecular sieve, β-type molecular sieve, MCM-22 type molecular sieve and mordenite, preferably at least one of Y-type molecular sieve, ZSM-5 type molecular sieve and β-type molecular sieve, and more preferably β-type molecular sieve.
[0043] In the present invention, preferably, in step (1), the carrier is aluminum oxide and / or silicon oxide.
[0044] In the present invention, preferably, in step (1), the mass ratio of the molecular sieve to the carrier is 95:5-20:80, and more preferably 90:10-25:75.
[0045] In the present invention, preferably, in step (1), the carrier exists in a solid state and / or a sol state, and more preferably exists in a sol state. The advantage of adopting this preferred embodiment is that the molecular sieve and the carrier can be better mixed, more evenly distributed, more strongly interacted, and the catalyst activity is better.
[0046] In the present invention, preferably, when the carrier is in a sol state, the carrier is provided by aluminum sol and / or silica sol.
[0047] In the present invention, there is no particular limitation on the concentration of aluminum sol and silica sol. Preferably, the concentration of aluminum sol and silica sol is independently 10-30 wt%.
[0048] In the present invention, preferably, in step (1), the carrier is alumina.
[0049] In the present invention, there is no particular limitation on the type of aluminum oxide precursor, as long as it can provide aluminum oxide. Preferably, the aluminum oxide is provided by at least one of pseudo-boehmite, aluminum chloride, aluminum hydroxide and aluminum sol.
[0050] In the present invention, there is no particular limitation on the type of copper precursor, as long as it can provide copper element. Preferably, in step (2), the copper precursor is selected from soluble copper compounds, preferably at least one selected from cupric chloride, cuprous chloride, cupric nitrate, cupric sulfate and cuprous sulfate.
[0051] In the present invention, there is no particular limitation on the type of phosphorus-containing compound, as long as it can provide phosphorus. Preferably, in step (2), the phosphorus-containing compound is selected from at least one of phosphoric acid, phosphorous acid, soluble phosphates and phosphites.
[0052] In the present invention, there is no particular limitation on the specific type of the soluble phosphate. Preferably, the soluble phosphate is selected from at least one of ammonium phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.
[0053] In the present invention, preferably, the phosphorus-containing compound is provided by an aqueous solution of the phosphorus-containing compound. Preferably, the concentration of the phosphorus-containing compound is 0.01-25wt%, preferably 5-25wt%.
[0054] In the present invention, preferably, in step (2), the mass ratio of the copper precursor to the phosphorus-containing compound is 5:95-70:30, preferably 30:70-80:20. By controlling the amount of the copper precursor and the phosphorus-containing compound, the acid distribution in the catalyst can be controlled, the proportion of medium and strong acids can be increased, and the hydrothermal stability of the catalyst can be improved, the long-term continuous operation of the catalyst can be achieved, and the reaction temperature of the synthesis reaction can be widened, which is conducive to industrial production.
[0055] In the present invention, preferably, the mass ratio of the carrier to the copper precursor is 80:20-99.9:0.1, and more preferably 85:15-99:1. The advantages of adopting this preferred embodiment are that the preparation method is simple, and Cu 2+ / Cu + More is distributed on the molecular sieve.
[0056] In the present invention, when the carrier alumina exists in a sol state, a peptizing agent needs to be introduced to peptize it. The present invention does not particularly limit the specific operation mode of peptization, and those skilled in the art can select it according to actual needs. Preferably, the preparation method of the catalyst also includes: introducing a peptizing agent into a solution containing a copper precursor and a phosphorus-containing compound and mixing it with the mixture obtained in step (1) to form a mixture.
[0057] In the present invention, there is no particular limitation on the type of peptizing agent, and all peptizing agents conventionally defined in the art are applicable to the present invention. Preferably, the peptizing agent is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, formic acid and acetic acid.
[0058] In the present invention, there is no particular limitation on the amount of the peptizing agent, as long as it can meet the peptization requirements, and those skilled in the art can select it according to actual needs. Preferably, the amount of the peptizing agent is such that the pH of the solution containing the copper precursor and the phosphorus-containing compound is 1-4. The present invention also does not particularly limit the concentration of the peptizing agent, and those skilled in the art can select it according to actual needs.
[0059] In the present invention, there is no particular limitation on the molding method in step (2), and those skilled in the art can select the method according to actual needs.
[0060] In the present invention, the range of selection of calcination conditions is relatively wide. Preferably, in step (2), the calcination conditions include: temperature of 450-800°C, time of 1-15h; further preferably, in step (2), the calcination conditions include: temperature of 500-700°C, time of 2-8h.
[0061] The present invention will be described in detail below by way of examples. In the following examples, all raw materials used are commercially available unless otherwise specified.
[0062] Preparation Examples 1-7 and Comparative Examples 1-5 are used to illustrate the preparation of fresh catalysts.
[0063] Preparation Example 1
[0064] (1) 90 g HY molecular sieve (silicon to aluminum molar ratio of 5) and 10 g alumina were mixed evenly;
[0065] (2) 3 g of cuprous chloride was added to 100 g of 10 wt% H3PO4 solution, added to the mixed powder in step (1), mixed evenly, and extruded by an extruder, and calcined at 500° C. for 12 h to obtain catalyst Y-1. The acid content of the catalyst is shown in Table 1.
[0066] Preparation Example 2
[0067] (1) 750 g of β molecular sieve (silicon-aluminum molar ratio of 20) and 1250 g of 20 wt% aluminum sol were mixed uniformly;
[0068] (2) 5 g of Cu2SO4 was added to 100 g of a 5 wt% KH2PO4 solution, and then the pH was adjusted to 2.5 with nitric acid and added to the mixture of molecular sieve and aluminum sol, and then mixed and rolled and extruded into small balls, and then calcined at 600°C for 1 hour to obtain catalyst β-1. The acid content of the catalyst is shown in Table 1.
[0069] Preparation Example 3
[0070] (1) 200 g of ZSM-5 molecular sieve (silicon to aluminum molar ratio of 50) and 500 g of 20 wt% silica sol were mixed uniformly;
[0071] (2) 10g of Cu(NO3)2 was added to 100g of 10wt% K3PO4 solution, added to the molecular sieve and silica sol mixture, mixed evenly, extruded and molded by an extruder, and calcined at 800°C for 2h to obtain the catalyst ZSM-1. The acid content of the catalyst is shown in Table 1.
[0072] Preparation Example 4
[0073] The catalyst was prepared according to the method of Preparation Example 2, except that 50 g of Cu2SO4 was added to 200 g of 25 wt% KH2PO4 solution, and then the pH was adjusted to 4 with nitric acid and added to the mixture of molecular sieves and aluminum sol, and calcined at 500°C for 8 h to obtain catalyst β-2.
[0074] The results of the acid content of the catalyst are shown in Table 1.
[0075] Preparation Example 5
[0076] The catalyst was prepared according to the method of Preparation Example 2, except that the amount of Cu2SO4 added was 60 g and other conditions remained unchanged, to obtain catalyst β-3.
[0077] The results of the acid content of the catalyst are shown in Table 1.
[0078] Preparation Example 6
[0079] The catalyst was prepared according to the method of Preparation Example 2, except that 2 g of Cu2SO4 was added to 200 g of a 25 wt% KH2PO4 solution to obtain catalyst β-4.
[0080] The results of the acid content of the catalyst are shown in Table 1.
[0081] Preparation Example 7
[0082] The catalyst was prepared according to the method of Preparation Example 2, except that alumina powder was used instead of aluminum sol. Other conditions remained unchanged, and catalyst β-5 was obtained.
[0083] The results of the acid content of the catalyst are shown in Table 1.
[0084] Comparative Preparation Example 1
[0085] The catalyst was prepared according to the method of Preparation Example 1, except that no subsequent phosphorus loading was performed. The other conditions were the same as Preparation Example 1, and catalyst DY-1 was obtained.
[0086] The results of the acid content of the catalyst are shown in Table 1.
[0087] Comparative Preparation Example 2
[0088] The catalyst was prepared according to the method of Preparation Example 1, except that only phosphoric acid solution was added during the preparation of the catalyst. The other conditions were the same as Preparation Example 1, and catalyst DY-2 was obtained.
[0089] The results of the acid content of the catalyst are shown in Table 1.
[0090] Comparative Preparation Example 3
[0091] The catalyst was prepared according to the method of Preparation Example 2, except that only copper salt solution was added during the preparation of the catalyst. The other conditions were the same as Preparation Example 2, and catalyst Dβ-1 was obtained.
[0092] The results of the acid content of the catalyst are shown in Table 1.
[0093] Comparative Preparation Example 4
[0094] The catalyst was prepared according to the method of Preparation Example 2, except that only phosphoric acid solution was added during the preparation of the catalyst, and the other conditions were the same as Preparation Example 2 to obtain catalyst Dβ-2. The acid content of the catalyst is shown in Table 1.
[0095] Table 1
[0096]
[0097] The examples and comparative examples are used to illustrate the continuous production of N,N-dimethylaniline
[0098] Examples 1-7
[0099] The catalyst in the above-mentioned Preparation Example 1-7 was selected as a fresh catalyst for the synthesis of N,N-dimethylaniline. The catalyst was reacted in a fixed bed reactor. The molar ratio of methanol:aniline was 2:1, and the mass space velocity of methanol and aniline was 0.1h -1 The reaction temperature is 230°C. The raw materials are pumped into the reactor by a raw material pump. Aniline and methanol are gasified in the reactor and react after contacting the catalyst bed. When the aniline conversion rate is lower than 95%, the catalyst is considered to be deactivated and the catalyst is oxidized and regenerated.
[0100] First, the materials in the reactor were replaced with nitrogen, and then a mixed gas of ammonia and air with a volume ratio of 1:1 was introduced, and the volume space velocity of ammonia and air was 0.1h -1 , heating rate is 0.1℃ / min, heating to 450℃, keeping constant temperature for 8h.
[0101] The gas was then replaced with a mixture of phosphine and air in a volume ratio of 1:1, and the volumetric air velocity of the mixture was 0.1h -1 The temperature was raised to 550°C at a heating rate of 0.1°C / min and maintained at this temperature for 2 hours to obtain a regenerated catalyst. The regenerated catalyst was cooled to the reaction temperature and then the raw materials were introduced again to react, and multiple reaction regenerations were performed.
[0102] The reaction results are shown in Table 2.
[0103] Example 8
[0104] The catalyst in Preparation Example 2 was selected as a fresh catalyst and the catalyst was reacted in a fixed bed reactor. The molar ratio of methanol to aniline was 8:1 and the mass space velocity of methanol and aniline was 8h -1 The reaction temperature is 290°C. The raw materials are pumped into the reactor by a raw material pump. Aniline and methanol are gasified in the reactor and react after contacting the catalyst bed. When the aniline conversion rate is lower than 95%, the catalyst is considered to be deactivated and the catalyst is oxidized and regenerated.
[0105] First, the materials in the reactor were replaced with nitrogen, and then a mixed gas of ammonia and air with a volume ratio of 1:99 was introduced, and the volume space velocity of the mixed gas was 10h -1 , heating rate is 10℃ / min, heating to 550℃, and keeping temperature constant for 48h.
[0106] The gas was then replaced with pure phosphine, with a volumetric space velocity of 10h -1 The temperature was raised to 700°C at a heating rate of 10°C / min and kept at this temperature for 12 hours to obtain a regenerated catalyst. The obtained catalyst was cooled to the reaction temperature and the raw materials were introduced again to react, and multiple reactions and regeneration were performed.
[0107] The reaction results are shown in Table 2.
[0108] Example 9
[0109] The catalyst in Preparation Example 2 was selected as a fresh catalyst and the catalyst was reacted in a fixed bed reactor. The molar ratio of methanol to aniline was 5:1 and the mass space velocity of methanol and aniline was 4h -1 The reaction temperature is 250°C. The raw materials are pumped into the reactor by a raw material pump. Aniline and methanol are gasified in the reactor and react after contacting the catalyst bed. When the aniline conversion rate is lower than 95%, the catalyst is considered to be deactivated and the catalyst is oxidized and regenerated.
[0110] First, the materials in the reactor were replaced with nitrogen, and then a mixed gas of ammonia and air with a volume ratio of 1:1 was introduced. The volume space velocity of the mixed gas was 4h -1 , heating rate is 5℃ / min, heating to 500℃, and keeping constant temperature for 24h.
[0111] The gas was then replaced with a mixture of phosphine and oxygen in a volume ratio of 1:99, and the volumetric air velocity of the mixture was 5h -1 The temperature was raised to 600°C at a heating rate of 5°C / min and kept at this temperature for 6 hours to obtain a regenerated catalyst. The obtained catalyst was cooled to the reaction temperature and the raw materials were introduced again to react, and multiple reactions and regeneration were performed.
[0112] The reaction results are shown in Table 2.
[0113] Example 10
[0114] The catalyst in Preparation Example 2 was selected as a fresh catalyst and the catalyst was reacted in a fixed bed reactor. The molar ratio of methanol to aniline was 5:1 and the mass space velocity of methanol and aniline was 10h -1 The reaction temperature is 300°C. The raw materials are pumped into the reactor by a raw material pump. Aniline and methanol are gasified in the reactor and react after contacting the catalyst bed. When the aniline conversion rate is lower than 95%, the catalyst is considered to be deactivated and the catalyst is oxidized and regenerated.
[0115] First, the materials in the reactor were replaced with nitrogen, and then a mixture of phosphine and air with a volume ratio of 95:5 was introduced. The volume space velocity of the mixture was 4h -1 , heating rate is 5℃ / min, heating to 500℃, and keeping constant temperature for 24h.
[0116] The gas was then replaced with a mixture of phosphine and oxygen in a volume ratio of 1:99, and the volumetric air velocity of the mixture was 5h -1 The temperature was raised to 600°C at a heating rate of 5°C / min and kept at this temperature for 6 hours to obtain a regenerated catalyst. The obtained catalyst was cooled to the reaction temperature and the raw materials were introduced again to react, and multiple reactions and regeneration were performed.
[0117] The reaction results are shown in Table 2.
[0118] Comparative Examples 1-4
[0119] The catalysts in the above-mentioned comparative preparation examples 1-4 and the method in Example 1 were used to carry out the synthesis and oxidation regeneration reaction of N,N-dimethylaniline. The reaction results are shown in Table 2.
[0120] Comparative Example 5
[0121] The catalyst in Preparation Example 2 was selected as a fresh catalyst and the catalyst was reacted in a fixed bed reactor. The molar ratio of methanol to aniline was 5:1 and the mass space velocity of methanol and aniline was 4h -1 The reaction temperature is 250°C. The raw materials are pumped into the reactor by a raw material pump. Aniline and methanol are gasified in the reactor and react after contacting the catalyst bed. When the aniline conversion rate is lower than 95%, the catalyst is considered to be deactivated and the catalyst is oxidized and regenerated.
[0122] First, the materials in the reactor were replaced with nitrogen, and then a mixed gas with a volume ratio of ammonia and air of 1:1 was introduced. The volume space velocity of the mixed gas was 4h -1 The temperature was raised to 500°C at a rate of 5°C / min and kept constant for 24 hours to obtain a regenerated catalyst, which was cooled to the reaction temperature and then introduced into the raw material again for reaction, and regenerated by multiple reactions.
[0123] The reaction results are shown in Table 2.
[0124] Table 2
[0125]
[0126]
[0127] As can be seen from the above table, the catalysts reacted and regenerated by this method have a long reaction life, and after multiple reactions and regenerations, the life can be restored, and the activity does not change significantly. However, the catalyst in Comparative Example 5 was only regenerated for one period, and the catalyst life after oxidation regeneration continued to decay, indicating that this method cannot effectively regenerate the catalyst.
[0128] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.
Claims
1. A method for continuously producing N,N-dimethylaniline, characterized in that: The method comprises: synthesizing the N,N-dimethylaniline and oxidatively regenerating the catalyst to be regenerated, and returning the regenerated catalyst obtained by oxidatively regenerating to the synthesis of N,N-dimethylaniline for recycling; The synthesis of N,N-dimethylaniline comprises: in the presence of a fresh catalyst, reacting the reaction raw materials methanol and aniline in a gas phase to obtain a catalyst to be produced; the fresh catalyst comprises a molecular sieve, a carrier and a modified component, the modified component is copper and phosphorus, and the acid content of the medium-strong acid in the fresh catalyst accounts for more than 35% of the total acid content; The oxidation regeneration comprises: subjecting the catalyst to be regenerated to two-stage oxidation regeneration to obtain a regenerated catalyst.
2. The method according to claim 1, wherein: The molar ratio of methanol to aniline is 1-10:1, preferably 2-8:1; Preferably, the synthesis conditions of N,N-dimethylaniline include: reaction temperature of 220-300°C, mass space velocity of methanol and aniline of 0.1-10h -1 ; Preferably, when the conversion rate of aniline is lower than 95%, a spent catalyst is obtained.
3. The method according to claim 1 or 2, wherein: The oxidative regeneration comprises: S1, subjecting the catalyst to be regenerated to a stage of oxidation regeneration in an oxygen-containing atmosphere and an alkaline atmosphere, wherein the alkaline atmosphere is ammonia and / or methylamine; S2, subjecting the product obtained in step S1 to secondary oxidation regeneration in the presence of phosphine and optionally an oxygen-containing atmosphere.
4. The method according to claim 3, wherein: In step S1, the alkaline atmosphere is ammonia; Preferably, in step S1, based on the total amount of the oxygen-containing atmosphere and the alkaline atmosphere, the content of the alkaline atmosphere is 0.1-95% by volume, and the content of the oxygen-containing atmosphere is 5-99.9% by volume; Further preferably, in step S1, based on the total amount of the oxygen-containing atmosphere and the alkaline atmosphere, the content of the alkaline atmosphere is 1-90% by volume, and the concentration of the oxygen-containing atmosphere is 10-99% by volume; Preferably, in step S1, the conditions for the first stage oxidation regeneration include: the volume space velocity of the oxygen-containing atmosphere and the alkaline atmosphere is 0.01-10h -1 , heating rate is 0.1-50℃ / min, constant temperature is 400-550℃, constant temperature time is 0.5-48h; Preferably, in step S1 and step S2, the oxygen-containing atmosphere is independently selected from air and / or oxygen; Preferably, in step S2, based on the total amount of phosphine and optionally the oxygen-containing atmosphere, the content of phosphine is 0.1-100% by volume, and the content of the oxygen-containing atmosphere is 0-99.9% by volume; Further preferably, in step S2, based on the total amount of phosphine and optionally the oxygen-containing atmosphere, the content of phosphine is 50-100% by volume, and the content of the oxygen-containing atmosphere is 0-50% by volume; preferably, in step S2, the conditions for the second-stage oxidation regeneration include: the volume space velocity of the phosphine and optionally the oxygen-containing atmosphere is 0.1-15h -1 , the heating rate is 0.1-15℃ / min, the constant temperature is 500-700℃, and the constant temperature time is 0.5-12h.
5. The method according to any one of claims 1 to 4, wherein: The medium-strong acid content of the fresh catalyst accounts for 40-50% of the total acid content, preferably 42-45%; Preferably, the preparation method of the fresh catalyst comprises: (1) mixing a molecular sieve and a carrier to obtain a mixture; (2) mixing the mixture obtained in step (1) with a solution containing a copper precursor and a phosphorus-containing compound to form a mixture, and then calcining the mixture once to obtain a fresh catalyst.
6. The method according to claim 5, wherein: In step (1), the molecular sieve is at least one selected from Y-type molecular sieve, ZSM-5 type molecular sieve, β-type molecular sieve, MCM-22 type molecular sieve and mordenite, preferably at least one selected from Y-type molecular sieve, ZSM-5 type molecular sieve and β-type molecular sieve, and more preferably β-type molecular sieve; Preferably, in step (1), the carrier is aluminum oxide and / or silicon oxide; Preferably, in step (1), the mass ratio of the molecular sieve to the carrier is 95:5-20:80, more preferably 90:10-25:75; Preferably, in step (1), the carrier is in a solid state and / or a sol state, and more preferably in a sol state; Preferably, in step (1), the carrier is alumina.
7. The method according to claim 5, wherein: In step (2), the copper precursor is selected from soluble copper compounds, preferably at least one selected from cupric chloride, cuprous chloride, cupric nitrate, copper sulfate and cuprous sulfate; Preferably, in step (2), the phosphorus-containing compound is selected from at least one of phosphoric acid, phosphorous acid, soluble phosphates and phosphites; Preferably, the soluble phosphate is selected from at least one of ammonium phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.
8. The method according to claim 5, wherein: In step (2), the mass ratio of the copper precursor to the phosphorus-containing compound is 5:95-98:2, preferably 30:70-80:20; Preferably, the mass ratio of the carrier calculated as oxide to the copper precursor calculated as element is 80:20-99.9:0.1, and more preferably 85:15-99:
1.
9. The method according to claim 8, wherein: The preparation method of the catalyst further comprises: introducing a peptizing agent into a solution containing a copper precursor and a phosphorus-containing compound and mixing the mixture obtained in step (1) to form a mixture; Preferably, the peptizing agent is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, formic acid and acetic acid; Preferably, the amount of the peptizing agent used is such that the pH of the solution containing the copper precursor and the phosphorus-containing compound is 1-4.
10. The method according to claim 5, wherein: In step (2), the calcination conditions include: temperature of 450-800° C. and time of 1-15 h; Preferably, in step (2), the calcination conditions include: temperature of 500-700° C. and time of 2-8 h.