CN107089917A - Multiple stage fluidized-bed middle nitrobenzene compounds Hydrogenation for amino benzenes compounds technique - Google Patents

Abstract

The invention discloses a process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed. Under the action of gas velocity, the particle size is classified, and a coarse particle catalyst bed is formed in the lower part of the multi-stage fluidized bed, and a fine particle catalyst bed is formed in the upper part of the multi-stage fluidized bed. And through the setting of the overflow pipe, the height of the catalyst bed in each section is kept stable. Through an independent heat exchange system, the temperature of each section can be kept under control. It can realize the functions of rapid reaction and strong heat transfer in the early stage, and the purpose of deep gas conversion in the later stage. The invention has the advantages of simple control, large operating flexibility, wide gas velocity range, high raw material conversion rate (>99.990%), high product selectivity (greater than 99.40%), and the like.

Description

Process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed

technical field

The invention belongs to the technical field of chemical industry, in particular to a process for preparing aniline compounds by hydrogenating nitrobenzene compounds in a multi-stage fluidized bed.

Background technique

Aniline is a very important class of chemical products. With the wide application of polyurethane in the fields of construction, automobiles, electrical appliances and packaging materials, the output of methyl diisocyanate (MDI for short, prepared from aniline), the main raw material of polyurethane, has increased rapidly, resulting in a substantial increase in the consumption of aniline. . In addition, methylaniline is the main raw material for preparing another type of isocyanate TDI. Diaminobenzene and chloroaniline are important raw materials for pesticides, organic pigments, pharmaceuticals, and rubber antioxidants. The annual demand for these important chemicals is about 5 million tons.

And the common industrialized production method of preparing aniline, methylaniline, diaminobenzene, and chlorinated aniline is the catalyst hydrogenation of nitrobenzene compounds. The basic principle is to simultaneously vaporize and heat nitrobenzene compounds and hydrogen to about 180-200°C, pass them into a fluidized bed reactor, and generate aniline at 220-320°C under the action of a metal-loaded catalyst. After the reaction gas exits the reactor, it is condensed and dehydrated to obtain crude aniline compounds. Then various organic impurities are removed through the refined preparation process to obtain high-purity aniline compound products.

Due to the purity requirements of MDI, TDI and other pharmaceutical intermediates, the conversion rate of nitrobenzene compounds is required to be greater than 99.9%, so as to ensure the normal operation of the subsequent separation system and obtain a content of less than 5ppm in the final product. However, the bubbles in most fluidized beds are very large, the gas-solid contact effect is poor, and the corresponding conversion requirements cannot be met. The catalyst life is short, the energy consumption of the subsequent separation system is high, and the refined products cannot meet the quality requirements. The existing multi-stage fluidized bed technology can enhance the conversion of raw materials by forming multiple catalyst beds in the fluidized bed. However, this technology uses a catalyst with a relatively uniform particle size, and multi-stage fluidized bed operation relies on a higher gas velocity. This leads to not only a very complex structure of this type of fluidized bed, but also a narrow range of applicable gas velocity. It cannot well adapt to the needs of large fluctuations in production tasks in production (often resulting in large fluctuations in gas velocity and catalyst space velocity). It also prevents devices designed for large scale from operating efficiently at low loads.

Contents of the invention

In order to overcome the above-mentioned shortcoming of the prior art, the object of the present invention is to provide a kind of process of preparing aniline compound by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed, adopting a multi-stage fluidized bed reactor to achieve high operating flexibility and reaction The device has the advantages of simple structure, low investment and low energy consumption; it has the advantages of simple control, large operating flexibility, wide range of gas velocity, high conversion rate of raw materials (>99.990%), high product selectivity (greater than 99.40%), etc.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed. In the multi-stage fluidized bed, double-sieve catalysts are loaded, and then raw materials containing nitrobenzene compounds are fed in, at 0.3- Under the conditions of 0.8m/s, 180-290℃, absolute pressure 0.1-1MPa, and the molar ratio of hydrogen to nitrobenzene compounds is 6:1-20:1, nitrobenzene compounds are converted into aniline compounds.

In the double-sieving catalyst, the active metal is one or more of copper, gold, nickel, platinum, and iron, and the load is one of silica gel, alumina, silicon oxide, molecular sieve, or aluminum silicate, and the particle size distribution is 10-450 microns, with 60-80 microns and 200-300 microns as the peak centers, presenting a bimodal distribution, and the mass fraction of the components with 60-80 microns as the peak centers in the catalyst is 10-40%.

The nitrobenzene compound is one or more of nitrobenzene, dinitrobenzene, methylnitrobenzene, chloronitrobenzene and nitrophenol.

The purity of the nitrobenzene compound in the raw material is 90-99.99%, and the rest is impurities mainly including water or alcohols.

The multistage fluidized bed includes a fluidized bed 1, the lower end of the fluidized bed 1 is a gas inlet 2, and the upper end is a gas outlet 6, and two to four catalyst accumulation areas are arranged in the fluidized bed 1 along its axial direction, Adjacent catalyst accumulation areas are separated by a transverse porous distribution plate 5, and the top of the uppermost catalyst accumulation area is communicated with the bottom of the lowermost catalyst accumulation area through an overflow pipe 7, and each catalyst accumulation area has an independent replacement valve. The thermal system 3 and the component system 4 , the overflow pipe 7 can be arranged inside or outside the fluidized bed 1 .

The double-sieved catalyst is packed into the bottom section of the multi-stage fluidized bed, and the catalyst and the multi-stage fluidized bed are heated to 180°C by passing high-temperature gas (air or nitrogen), and then blown by an inert gas (nitrogen or argon). Sweep to make the oxygen content in the outlet gas of the fluidized bed less than 0.5%, then pass in a mixture of hydrogen and nitrogen, and reduce the catalyst at 180-200°C for 3-24 hours at a gas velocity of 0.03-0.1m/s hours, wherein the volume content of hydrogen is 10-40%, and then feed nitrobenzene compounds and hydrogen, and control the catalyst space velocity to be 0.1-2kg nitrobenzene compounds/kg catalyst/hour.

Heat hydrogen together with nitrobenzene compounds to 180-200°C, pass it into a multi-stage fluidized bed, adjust the average temperature in the first stage to 220-290°C, control the absolute pressure and gas velocity at the gas inlet, and double screen The fine particles in the catalyst are blown to the second, third or fourth stage of the multi-stage fluidized bed, and the temperature in the second to fourth stages is adjusted so that the temperature in the second to fourth stages is 180-260 ° C. The catalyst in the catalyst accumulation area of the uppermost stage When it is excessive, it returns to the catalyst accumulation area at the bottom through the overflow pipe, and the gas product exits the fluidized bed from the top.

Compared with prior art, the beneficial effect of the present invention is:

1) Compared with the previous multi-stage fluidized bed, the structure of the multi-stage fluidized bed of this technology is greatly reduced, and the cost is saved by about 30%. At the same time, the control operation difficulty is reduced by 30%.

2) After adopting a catalyst with a bimodal particle size distribution, the gas velocity range for forming a multi-stage fluidized bed operation is expanded downward by 0.1-0.2m/s, and the corresponding stable operating load is increased by 20-30%, making it possible to operate at low The proportion of qualified products operated under gas velocity and low load has increased by 80%. The process energy consumption of the subsequent refining system is reduced by 20-30%.

Description of drawings

Fig. 1 is a structural schematic diagram of a multi-stage fluidized bed provided by the present invention, two stages are arranged in total.

Fig. 2 is a structural schematic diagram of the multi-stage fluidized bed provided by the present invention, and three stages are arranged in total.

Fig. 3 is a structural schematic diagram of a multi-stage fluidized bed provided by the present invention, and four stages are arranged in total.

In the figure: 1. Fluidized bed; 2. Gas inlet; 3. Heat exchange system; 4. Component system; 5. Transverse porous distribution plate; 6. Gas outlet; 7. Overflow pipe.

detailed description

The implementation of the present invention will be described in detail below in conjunction with the drawings and examples.

Example 1:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a two-stage fluidized bed 1 according to Fig. 1 .

Fill the two-stage fluidized bed with double-sieve catalyst (nickel/silicon oxide, particle size distribution of 10-400 microns, double-sieve distribution with 60 microns, 200 microns as the peak center, and 60 microns as the peak center group The mass fraction in the catalyst is 10%), the catalyst and the multi-stage fluidized bed are heated to 180°C with high-temperature gas (air), and the oxygen content in the outlet gas of the fluidized bed is less than 0.5%. The catalyst was reduced at 180° C. for 10 hours at a gas velocity of 0.03 m/s by feeding a mixture of hydrogen and nitrogen (the volume content of hydrogen was 10%). Heat hydrogen together with nitrobenzene to 190°C, pass it into the fluidized bed, and control the catalyst space velocity to 0.4kg nitrobenzene/kg catalyst/hour. The reaction is exothermic, and the heat exchange system in the fluidized bed is adjusted so that the average temperature in the first section of the fluidized bed is 220°C. Control fluidized bed gas inlet 2 (absolute) pressure is 1MPa, the molar ratio of hydrogen and nitrobenzene is 6:1. The gas velocity is controlled to be 0.8m/s, and the fine particles in the double-screened catalyst are blown to the second stage of the multi-stage fluidized bed. Adjust the heat exchange system located in the second section so that the temperature of the second section is at 180°C.

When the catalyst in the catalyst accumulation area of the second stage is excessive, it returns to the lowermost catalyst accumulation area through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of nitrobenzene is 99.998%, and the selectivity of aniline is 99.60%.

Example 2:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a three-stage fluidized bed 1 according to Fig. 2 .

Fill the three-stage fluidized bed with a double-sieve catalyst (copper-nickel/silica gel, particle size distribution of 10-350 microns, double-sieve distribution with 70 microns, 250 microns as the peak center, and a group with 70 microns as the peak center The mass fraction in the catalyst as a whole is 30%), the catalyst and the multi-stage fluidized bed are heated to 180° C. with high-temperature gas (nitrogen), and the oxygen in the outlet gas of the fluidized bed is purged by an inert gas (nitrogen). The content is less than 0.5%. The catalyst was reduced at 180° C. for 24 hours by feeding a mixture of hydrogen and nitrogen (the volume content of hydrogen was 10%), and the gas velocity was 0.05 m/s. Heat hydrogen together with methylnitrobenzene to 180°C, pass it into the fluidized bed, and control the catalyst space velocity to 0.7kg methylnitrobenzene/kg catalyst/hour. The reaction is exothermic, and the heat exchange system in the fluidized bed is adjusted so that the average temperature in the first section of the fluidized bed is 270°C. The absolute pressure of the fluidized bed gas inlet is controlled to be 0.4MPa, and the molar ratio of hydrogen to methylnitrobenzene is 12:1. The gas velocity is controlled at 0.3m/s, and the fine particles in the double-screened catalyst are blown to the second and third stages of the multi-stage fluidized bed (the second and third stages each account for 50% of the fine particles). Adjust the heat exchange system in each section so that the temperature of the second and third sections is both 250°C.

When the catalyst in the catalyst accumulation area of the third stage is excessive, it returns to the catalyst accumulation area in the lowermost stage through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of methylnitrobenzene is 99.992%, and the selectivity of methylaniline is 99.60%.

Example 3:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a four-stage fluidized bed 1 according to Fig. 3 .

Fill the four-stage fluidized bed with double-sieve catalysts (gold-copper/alumina, particle size distribution of 15-450 microns, double-sieve distribution with 80 microns, 300 microns as the peak center, and 80 microns as the peak center The mass fraction of the component in the catalyst is 40%), the catalyst and the multi-stage fluidized bed are heated to 195 °C with high-temperature gas (air), and the fluidized bed outlet gas is purged by an inert gas (nitrogen or argon). The oxygen content is less than 0.5%. The catalyst was reduced at 200° C. for 12 hours by feeding a mixture of hydrogen and nitrogen (the volume content of hydrogen was 20%), and the gas velocity was 0.03 m/s. Heat hydrogen together with chloronitrobenzene to 200°C, pass it into the fluidized bed, and control the catalyst space velocity to 0.9kg chloronitrobenzene/kg catalyst/hour. The heat of reaction is released, and the amount of cooling medium in the heat exchange system in the fluidized bed is adjusted so that the average temperature in the first section of the fluidized bed is 290°C. Control the absolute pressure of the gas inlet of the fluidized bed to 0.5MPa, and the molar ratio of hydrogen to chloronitrobenzene is 20:1. Control the gas velocity at 0.6m/s, and blow the fine particle part in the double-screened catalyst to the second section of the multi-stage fluidized bed, the third section and the fourth section (the second, third, and fourth sections respectively account for 30% of the fine particle part) 50%, 30%, 20%). Adjust the heat exchange system located in each section so that the temperatures of the second, third and fourth sections are respectively 260, 250 and 240°C.

When the catalyst in the catalyst accumulation area of the fourth stage is excessive, it returns to the catalyst accumulation area in the lowermost stage through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of chloronitrobenzene is 99.994%, and the selectivity of chloroaniline is 99.60%.

Example 4:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a two-stage fluidized bed 1 according to Fig. 1 .

Fill the two-stage fluidized bed with double sieve catalyst (Fe-Pt/molecular sieve, the particle size distribution is 10-380 microns, the double sieve distribution takes 70 microns, 200 microns as the peak center, and the group with 70 microns as the peak center The mass fraction in the catalyst is 20%), the catalyst and the multi-stage fluidized bed are heated to 189°C with high-temperature gas (air), and purged by an inert gas (nitrogen or argon), the fluidized bed outlet gas The oxygen content is less than 0.5%. A mixture of hydrogen and nitrogen (the volume content of hydrogen is 30%) was introduced, and the catalyst was reduced at 180° C. for 3 hours at a gas velocity of 0.1 m/s. Heat hydrogen together with dinitrobenzene (containing 5% nitrobenzene) to 200° C., and control the catalyst space velocity to 0.1 kg dinitrobenzene (containing 5% nitrobenzene)/kg catalyst/hour. Pass into the fluidized bed, the reaction releases heat, adjust the amount of cooling medium in the heat exchange system in the fluidized bed, so that the average temperature in the first section of the fluidized bed is 260 °C. Control the (absolute) pressure of the gas inlet (2) of the fluidized bed to 0.1 MPa, and the molar ratio of hydrogen to dinitrobenzene (containing 5% nitrobenzene) is 15:1. The gas velocity is controlled at 0.5m/s, and the fine particles in the double-screened catalyst are blown to the second stage of the multi-stage fluidized bed. Adjust the heat exchange system in each section so that the temperature of the second section is 260°C.

When the catalyst in the catalyst accumulation area of the second stage is excessive, it returns to the lowermost catalyst accumulation area through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of dinitrobenzene is 99.992%, and the selectivity of diphenylamine is 99.60%. Wherein the conversion rate of nitrobenzene is 99.997%, and the selectivity of aniline is 99.45%.

Example 5:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a two-stage fluidized bed 1 according to Fig. 1 .

Fill the two-stage fluidized bed with a double-sieve catalyst (iron-platinum/aluminum silicate, the particle size distribution is 10-450 microns, the double-sieve distribution takes 75 microns, 300 microns as the peak center, and 75 microns as the peak center The mass fraction of the component in the catalyst is 20%), the catalyst and the multi-stage fluidized bed are heated to 185° C. with high-temperature gas (air), purged with an inert gas (argon), and the fluidized bed outlet gas is The oxygen content is less than 0.5%. The catalyst was reduced at 190° C. for 13 hours by feeding a mixture of hydrogen and nitrogen (the volume content of hydrogen was 25%), and the gas velocity was 0.2 m/s. Heat hydrogen together with nitrophenol to 190°C, pass it into the fluidized bed, and control the catalyst space velocity to 1.4kg nitrophenol/kg catalyst/hour. The heat of reaction is released, and the amount of cooling medium in the heat exchange system in the fluidized bed is adjusted so that the average temperature in the first section of the fluidized bed is 275°C. Control the fluidized bed gas inlet 2 (absolute) pressure to 0.7MPa, and the molar ratio of hydrogen to nitrophenol to 13:1. The gas velocity is controlled at 0.4m/s, and the fine particles in the double-screened catalyst are blown to the second stage of the multi-stage fluidized bed. Adjust the heat exchange system in each section so that the temperature of the second section is 240°C.

When the catalyst in the catalyst accumulation area of the second stage is excessive, it returns to the lowermost catalyst accumulation area through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of nitrophenol is 99.996%, and the selectivity of aminophenol is 99.50%.

Embodiment 6:

The gas inlet 2, the gas outlet 6, the component system 4, the heat exchange system 3, the transverse porous distribution plate 5, the overflow pipe 7, etc. form a three-stage fluidized bed 1 according to Fig. 2 .

Fill the two-stage fluidized bed with double sieve catalyst (copper/silicon oxide, the particle size distribution is 20-430 microns, the double sieve distribution takes 60 microns, 240 microns as the peak center, and the group with 60 micron as the peak center The mass fraction in the catalyst is 10%), the catalyst and the multi-stage fluidized bed are heated to 180°C with high-temperature gas (nitrogen), and the oxygen content in the outlet gas of the fluidized bed is less than 0.5%. The catalyst was reduced at 180° C. for 10 hours by feeding a mixture of hydrogen and nitrogen (the volume content of hydrogen was 20%), and the gas velocity was 0.1 m/s. Heat hydrogen and nitrobenzene (containing 10% dinitrobenzene) to 180°C, pass it into the fluidized bed, and control the catalyst space velocity to 2kg nitrobenzene (containing 10% dinitrobenzene)/kg catalyst/hour . The reaction is exothermic, and the heat exchange system in the fluidized bed is adjusted so that the average temperature in the first section of the fluidized bed is 270°C. Control the fluidized bed gas inlet 2 (absolute) pressure to 1MPa, and the molar ratio of hydrogen to nitrobenzene (containing 10% dinitrobenzene) to 6:1. The gas velocity is controlled to be 0.8m/s, and the fine particles in the double-screened catalyst are blown to the second and third stages of the multi-stage fluidized bed (the second and third stages account for 70% and 30% of the fine particles respectively). Adjust the heat exchange system in the second and third sections so that the temperatures of the second and third sections are 240 and 220°C respectively.

When the catalyst in the catalyst accumulation area of the third stage is excessive, it returns to the catalyst accumulation area in the lowermost stage through the overflow pipe. The gaseous product exits the fluidized bed from the top. The conversion rate of nitrobenzene is 99.998%, and the selectivity of aniline is 99.60%. Wherein the conversion rate of dinitrobenzene is 99.991%, and the selectivity of diphenylamine is 99.45%.

Claims (10)

1. A process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed is characterized in that, in the multi-stage fluidized bed, a double screening catalyst is filled, and then the raw material containing nitrobenzene compounds The nitrobenzene compound is converted into Aniline compounds. 2. according to claim 1, the process for preparing anilines by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed, is characterized in that, in the double screening catalyst, the active metal is copper, gold, nickel, platinum, iron One or more of them, and the load is one of silica gel, alumina, silicon oxide, molecular sieve or aluminum silicate. 3. according to claim 1 or 2, the process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed, is characterized in that, the double sieving catalyst has a particle size distribution of 10-450 microns, wherein With 60-80 microns and 200-300 microns as the peak center, it presents a bimodal distribution. 4. according to claim 3 in the described multistage fluidized bed, the technology that nitrobenzene compound is hydrogenated prepares aniline compound, it is characterized in that, described double sieve catalyst, take 60-80 micron as the component of peak center in The mass fraction in the catalyst is 10-40%. 5. according to the technology that the hydrogenation of nitrobenzene compounds in the multistage fluidized bed of claim 1 prepares aniline compounds, it is characterized in that, described nitrobenzene compounds are nitrobenzene, dinitrobenzene, methyl One or more of nitrobenzene, chloronitrobenzene and nitrophenol. 6. according to claim 1, the process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in the multi-stage fluidized bed is characterized in that, the purity of nitrobenzene compounds in the raw material is 90-99.99%, and the rest are Contains mainly water or alcohol impurities. 7. according to the technology that nitrobenzene compound hydrogenation prepares aniline compound in the described multistage fluidized bed of claim 1, it is characterized in that, described multistage fluidized bed comprises fluidized bed (1), fluidized bed (1 ) is the gas inlet (2) at the lower end, and the gas outlet (6) at the upper end, two to four catalyst accumulation areas are arranged in the fluidized bed (1) along its axial direction, between adjacent catalyst accumulation areas The horizontal porous distribution plate (5) separates the top of the catalyst accumulation area in the uppermost section and the bottom of the catalyst accumulation area in the lowermost section through the overflow pipe (7). Each catalyst accumulation area has an independent heat exchange system (3) and component systems (4). 8. The process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed according to claim 7, wherein the overflow pipe (7) is arranged inside or outside the fluidized bed (1) . 9. according to claim 1, the process of preparing aniline compounds by hydrogenation of nitrobenzene compounds in the multi-stage fluidized bed, is characterized in that, the double screening catalyst is packed into the bottom section of the multi-stage fluidized bed, and is passed through Inject high-temperature gas to heat the catalyst and multi-stage fluidized bed to 180°C, and then purge with inert gas to make the oxygen content in the outlet gas of the fluidized bed less than 0.5%, and then introduce a mixture of hydrogen and nitrogen at a gas velocity of 0.03 Under the condition of -0.1m/s, reduce the catalyst at 180-200°C for 3-24 hours, wherein the hydrogen volume content is 10-40%, and then feed nitrobenzene compounds and hydrogen, and control the catalyst space velocity to 0.1 - 2 kg nitrobenzenes/kg catalyst/hour. 10. The process for preparing aniline compounds by hydrogenation of nitrobenzene compounds in a multi-stage fluidized bed according to claim 1 or 9, characterized in that the hydrogen and nitrobenzene compounds are heated to 180-200° C. into the multi-stage fluidized bed, adjust the average temperature in the first stage to be 220-290°C, control the absolute pressure and gas velocity of the gas inlet, and blow the fine particles in the double-screened catalyst to the second stage of the multi-stage fluidized bed, In the third or fourth section, adjust the temperature in the second to fourth sections at 180-260°C. When the catalyst in the uppermost catalyst accumulation area is excessive, return to the lowermost catalyst accumulation area through the overflow pipe, and the gas product The fluidized bed exits from the top.